Electroplating method for metal fastener and electroplating device for metal fastener

TECHNICAL FIELD

The present invention relates to an electroplating method for a metal fastener. The present invention also relates to an electroplating device for a metal fastener.

BACKGROUND ART

Some slide fasteners include element rows made of a metal, and such slide fasteners are generally referred to as "metal fasteners". The metal fasteners often use copper alloys or aluminum alloys, and are suitable for designs that take advantage of color and texture of metals. Recently, there are various needs of user for the design of the metal fastener, and various color tones are required depending on applications.

One of methods for changing the color tone of a metal product is electroplating. In the electroplating method, an object to be plated is immersed in a plating solution and energization is conducted to form a plating film on a surface of the object to be plated.

Most electroplating methods for small products use barrel plating in which an object to be plated is placed in a barrel, the barrel is introduced into a plating solution, and electroplating is carried out while rotating the barrel (e.g., Japanese Patent Application Publication No. <patcit id="pcit0001" dnum="JP20041000011A"><text>2004-1000011 A</text></patcit>, Japanese Patent Application Publication No. <patcit id="pcit0002" dnum="JP2008202086A"><text>2008-202086 A</text></patcit>, Japanese Patent No. <patcit id="pcit0003" dnum="JP3087554B"><text>3087554 B</text></patcit>, and Japanese Patent No. <patcit id="pcit0004" dnum="JP5063733B"><text>5063733 B</text></patcit>).

Further, as an electroplating method for an elongated product, a method is known in which electroplating is carried out while continuously conveying the elongated product in a plating bath (e.g., Japanese Patent Application Publication No. <patcit id="pcit0005" dnum="JP2004076092A"><text>2004-76092A</text></patcit>, Japanese Patent Application Publication No. <patcit id="pcit0006" dnum="JPH05239699A"><text>H05-239699 A</text></patcit>, and Japanese Patent Application Publication No. <patcit id="pcit0007" dnum="JPH08209383A"><text>H08-209383 A</text></patcit>).

However, the above methods do not consider specificities of the metal fasteners. In the metal fastener, adjacent elements are not electrically connected to each other, so that it is difficult to electroplate uniformly each element by the above method. Therefore, to plate the metal fastener, a method is proposed in which a fastener chain is produced in a state where elements have been electrically connected in advance, and the fastener chain is continuously subjected to electroplating. For example, Japanese Patent No. <patcit id="pcit0008" dnum="JP2514760B"><text>2514760 B</text></patcit> proposes to produce a fastener chain in a state where elements are electrically connected, by knitting conductive yarns into an element attachment portion of a fastener tape.

CITATION LIST

Patent Literatures

<ul id="ul0001" list-style="none" compact="compact"><li>Patent Document 1: Japanese Patent Application Publication No. <patcit id="pcit0009" dnum="JP2004100011A"><text>2004-100011 A</text></patcit></li><li>Patent Document 2: Japanese Patent Application Publication No. <patcit id="pcit0010" dnum="JP2008202086A"><text>2008-202086 A</text></patcit></li><li>Patent Document 3: Japanese Patent No. <patcit id="pcit0011" dnum="JP3087554B"><text>3087554 B</text></patcit></li><li>Patent Document 4: Patent No. <patcit id="pcit0012" dnum="JP5063733B"><text>5063733 B</text></patcit></li><li>Patent Document 5: Japanese Patent Application Publication No. <patcit id="pcit0013" dnum="JP2004076092A"><text>2004-76092 A</text></patcit></li><li>Patent Document 6: Japanese Patent Application Publication No. <patcit id="pcit0014" dnum="JPH05239699A"><text>H05-239699 A</text></patcit></li><li>Patent Document 7: Japanese Patent Application Publication No. <patcit id="pcit0015" dnum="JPH08209383A"><text>H08-209383 A</text></patcit></li><li>Patent Document 8: Japanese Patent No. <patcit id="pcit0016" dnum="JP2514760B"><text>2514760 B</text></patcit></li></ul>

SUMMARY OF INVENTION

Technical Problem

In the case of the method disclosed in Japanese Patent No. <patcit id="pcit0017" dnum="JP2514760B"><text>2514760 B</text></patcit>, a current can be applied to the entire element row simultaneously to electroplate it continuously. However, the method has a problem that the conductive yarn is expensive, and the conductive yarn is easily cut and the metal is easily dissolved in preparation and dying of the tape due to knitting of the metal conductive yarn, so that productivity is poor. As a method for electroplating a metal fastener without using the conductive yarns, a continuous plating method is considered in which a metal fastener is conveyed while bringing individual elements of the metal fastener into contact with a surface of a cylindrical feed roll in a plating bath. However, with such a method, the contact between the feed roll and the element tends to be uneven, so that it is necessary to repeat the contact with the feed roll many times in order to obtain uniformity of a plating film. This leads to necessity of a large-scale and expensive plating device.

Thus, a main object of the present invention is to provide a method and device for electroplating a metal fastener, which can conveniently plate individual elements of the metal fastener with improved uniformity, even if the elements are not electrically connected to each other in advance.

Solution to Problem

The metal fasteners are generally produced via an intermediate product called a fastener chain which is formed by engaging metal element rows fixed to opposing side edges of a pair of elongated fastener tapes. The fastener chain is cut at a predetermined length, and various parts such as a slider, upper stoppers, a lower stopper and the like are attached to complete the metal fastener.

The present inventor has conducted intensive studies in order to solve the above problems, and found that it is effective to bring each metal element fixed to a fastener chain into contact with a plurality of conductive media flowably accommodated and apply a current via the conductive media while traveling the fastener chain in a plating solution. Then, the present inventors has found that, by ensuring the contacting of the metal elements with the plating solution while disposing the conductive media on one main surface side of the fastener chain without disposing the conductive media on the other main surface side when the metal elements are brought into contact with the conductive media, a plating film is effectively grown on the other main surface side. That is, the present inventor has found that a current can be reliably carried to the individual elements by plating the metal element on one side across the fastener tape at one time.

The present invention completed based on the above findings is illustrated as follows: <ul id="ul0002" list-style="none"><li>[1] A method for electroplating a fastener chain having rows of metal elements, the method comprising: <ul id="ul0003" list-style="none" compact="compact"><li>causing the fastener chain to pass through one or more first insulating container(s) (110a, 310a) while bringing each metal element into contact with a plating solution in a plating bath, the first insulating container(s) (110a, 310a) flowably accommodating a plurality of conductive media (111, 311) in electrical contact with a negative electrode (118, 317),</li><li>wherein, during the fastener chain passing through the first insulating container(s) (110a, 310a), power is supplied by mainly bringing a surface of each metal element exposed on a first main surface side of the fastener chain into contact with the conductive media (111, 311) in the first insulating container(s) (110a, 310a); and</li><li>a first positive electrode (119, 316) is disposed at a positional relationship so as to face a surface of each metal element exposed on a second main surface side of the fastener chain.</li></ul></li><li>[2] The method according to [1], wherein the fastener chain passes through the first insulating container(s) (110a, 310a) while rising.</li><li>[3] The method according to [2], wherein the fastener chain passes through the first insulating container(s) (110a, 310a) while rising in a vertical direction.</li><li>[4] The method according to any one of [1] to [3], wherein, during the fastener chain passing through the first insulating container(s) (110a), power is supplied by bringing only the surface of each metal element exposed on the first main surface side of the fastener chain into contact with the conductive media (111) in the first insulating container(s) (110a).</li><li>[5] The method according to any one of [1] to [4], further comprising: <ul id="ul0004" list-style="none" compact="compact"><li>a step of causing the fastener chain to pass through one or more second insulating container(s) (110b, 310b) while bringing each metal element into contact with a plating solution in a plating bath, each of the second insulating container(s) (110b, 310b) flowably accommodating the conductive media (111, 311) in electrical contact with the negative electrode (118, 317),</li><li>wherein, during the fastener chain passing through the second insulating container(s) (110b, 310b), power is supplied by mainly bringing the surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media (111, 311) in the second insulating container(s) (110b, 310b); and</li><li>a second positive electrode (119, 316) is disposed at a positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain.</li></ul></li><li>[6] The method according to [5], wherein, during the fastener chain passing through the second insulating container(s) (110b), power is supplied by bringing only the surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media (111) in the second insulating container(s) (110b).</li><li>[7]. The method according to any one of [1] to [6], wherein each of the conductive media (111, 311) is spherical.</li><li>[8] The method according to [7], wherein the first insulating container(s) (110a) comprises: a passage (112) for guiding a traveling path of the fastener chain; and an accommodating portion (113) for flowably accommodating the conductive media (111), inside the first insulating container(s) (110a); the passage (112) comprises: an inlet (114) for the fastener chain; an outlet (115) for the fastener chain; one or more opening(s) (117) on a passage surface (112a) facing the first main surface side of the fastener chain, the opening(s) (117) enabling access to the conductive media (111); and one or more opening(s) (116) on a passage surface (112b) facing the second main surface side of the fastener chain, the opening(s) (116) enabling fluid communication with the plating solution; and the one or more opening(s) (117) enabling access to the conductive media (111) satisfies a relationship: 2D &lt; W2 &lt; 6D, in which W2 represents a length in a chain width direction, and D represents a diameter of each of the conductive media (111).</li><li>[9] The method according to any one of [1] to [8], wherein the negative electrode (118, 317) used in the first insulating container(s) (110a, 310a) is disposed at multiple positions on an inner side of the first insulating container(s) (110a, 310a).</li><li>[10]. The method according to [9], wherein the negative electrode (118, 317) is disposed at least on a front inner side (113a) in a passing direction of the fastener chain; and on a rear portion of an inner side (113b) parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a).</li><li>[11] The method according to [10], wherein the negative electrode (118, 317) is disposed at least on a central portion of the inner side (113b) in the passing direction of the fastener chain, the inner side being parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a).</li><li>[12] The method according to [11], wherein the negative electrode (118, 317) disposed on the inner side (113b) parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a), is disposed so as to be flush with the inner side.</li><li>[13]. The method according to [11] or [12], wherein the negative electrode (118, 317) disposed on the inner side (113b) parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a), is disposed within a range of from 30 to 70% from a front side of the passing direction of the fastener chain, relative to 100% of a length of the inner side in the passing direction.</li><li>[14] The method according to any one of [9] to [13], wherein the negative electrode (118, 317) is disposed at multiple positions at equal intervals in the passing direction of the fastener chain.</li><li>[15] The electroplating method according to any one of [9] to [14], wherein the negative electrode (118, 317) disposed at multiple positions has the same potential, respectively.</li><li>[16] The method according to any one of [9] to [15], wherein a relationship: 0.8 ≤ D_min / D_max is satisfied, in which D_max represents a current density of an element having the highest current density among the elements passing through the first insulating container(s) (110a, 310a), and D_min represents a current density of an element having the lowest current density among the elements passing through the first insulating container(s) (110a, 310a).</li><li>[17] The method according to any one of [9] to [16] depending from [5] or [6], wherein the negative electrode (118, 317) used for the second insulating container(s) (110b, 310b) is disposed at multiple positions on an inner side of the second insulating container(s) (110b, 310b).</li><li>[18] A device for electroplating a fastener chain having rows of metal elements, comprising: <ul id="ul0005" list-style="none" compact="compact"><li>a plating bath (201, 401) capable of accommodating a plating solution;</li><li>a first positive electrode (119, 316) disposed in the plating bath (201, 401); and</li><li>one or more first insulating container(s) (110a, 310a) disposed in the plating path (201, 401), the first insulating container(s) (110a, 310a) flowably accommodating a plurality of conductive media (111, 311) in electrical contact with a negative electrode (118,317),</li><li>wherein the first insulating container(s) (110a, 310a) are configured to enable the fastener chain to pass through the first insulating container(s) (110a, 310a) while mainly bringing a surface of each metal element exposed on a first main surface side of the fastener chain into contact with the conductive media (111, 311) in the first insulating container(s) (110a, 310a); and</li><li>the first positive electrode (119, 316) is disposed in a positional relationship so as to face a surface of each metal element exposed on a second main surface side of the fastener chain during the fastener chain passing through the first insulating container(s) (110a, 310a).</li></ul></li><li>[19] The device according to [18], wherein the first insulating container(s) (110a) comprises: a passage (112) for guiding a traveling path of the fastener chain; and an accommodating portion (113) for flowably accommodating the conductive media (111), inside the first insulating container(s) (110a); and the passage (112) comprises: an inlet (114) for the fastener chain; an outlet (115) for the fastener chain; one or more opening(s) (117) on a passage surface (112a) facing the first main surface side of the fastener chain, the opening(s) (117) enabling access to the conductive media (111); and one or more opening(s) (116) on a passage surface (112b) facing the second main surface side of the fastener chain, the opening(s) (116) enabling fluid communication with the plating solution.</li><li>[20] The device according to [18] or [19], wherein the passage (112) has the outlet (115) above the inlet (114).</li><li>[21] The device according to [20], wherein the passage (112) has the outlet (115) vertically above the inlet (114).</li><li>[22] The device according to any one of [18] to [21], further comprising: <ul id="ul0006" list-style="none" compact="compact"><li>a second positive electrode (119, 316) disposed in the plating bath (201, 401); and</li><li>one or more second insulating container(s) (110b, 310b) disposed in the plating bath (201, 401), the second insulating container(s) (201, 401) flowably accommodating a plurality of conductive media (111, 311) in electrical contact with a negative electrode (118,317),</li><li>wherein the second insulating container(s) (110b, 310b) are configured to enable the fastener chain to pass through the second insulating container(s) (110b, 310b) while mainly bringing the surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media (111, 311) in the second insulating container(s) (110b, 310b); and</li><li>the second positive electrode (119, 316) is disposed in a positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain during passing the fastener chain through the second insulating container(s) (110b, 310b).</li></ul></li><li>[23] The device according to [18], wherein the first insulating container(s) (310a) are configured to enable the fastener chain to pass through the first insulating container(s) (310a) such that the first main surface is on a lower side and the second main surface is on an upper side; the first insulating container(s) (310a) is a rotary barrel comprising: an inlet (314a) for the fastener chain; an outlet (315a) for the fastener chain; and a rotation axis (313) parallel to a traveling direction of the fastener chain; and the conductive media (311) are filled in the rotary barrel to a height that is preferentially contacted with the surface of each metal element exposed on the first main surface side of the fastener chain compared with the surface of each metal element exposed on the second main surface side of the fastener chain.</li><li>[24] The device according to [22], wherein the second insulating container(s) (310b) is configured to enable the fastener chain to pass through the second insulating container(s) (310b) such that the first main surface is on the lower side and the second main surface is on the upper side; the second insulating container(s) (310b) is a rotary barrel comprising: an inlet (314b) for the fastener chain; an outlet (315b) for the fastener chain; and a rotation axis (313) parallel to a traveling direction of the fastener chain; and the rotary barrel comprises at least one guide (312) protruding inward from an inner surface parallel to the rotation axis (313), such that the conductive media (311) accommodated in the rotary barrel are preferentially contacted with the surface of each metal element exposed on the second main surface side of the fastener chain compared with the surface of each metal element exposed on the first main surface side of the fastener chain.</li><li>[25] The device according to any one of [18] to [24], wherein the negative electrode (118, 317) used in the first insulating container(s) (110a, 310a) is disposed at multiple positions on an inner side of the first insulating container(s) (110a, 310a).</li><li>[26] The device according to [25], wherein the negative electrode (118, 317) is disposed at least on a front inner side (113a) in a passing direction of the fastener chain; and on a rear portion of an inner side surface (113b) parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a).</li><li>[27]. The device according to [26], wherein the negative electrode (118, 317) is disposed at least on a central portion of the inner side (113b) in the passing direction of the fastener chain, the inner side being parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a).</li><li>[28] The device according to [27], wherein the negative electrode (118, 317) disposed on the inner side (113b) parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a), is disposed so as to be flush with the inner side .</li><li>[29] The device according to [27] or [28], wherein the negative electrode (118, 317) disposed on the inner side (113b) parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (110a, 310a), is disposed within a range of from 30 to 70% from a front side of the passing direction of the fastener chain, relative to 100% of a length of the inner side in the passing direction.</li><li>[30] The device according to any one of [25] to [29], wherein the negative electrode (118, 317) is disposed at multiple positions at equal intervals in the passing direction of the fastener chain.</li><li>[31] The device according to any one of [25] to [30] depending from [22], wherein the negative electrode (118, 317) used in the second insulating container(s) (110b, 310b) is disposed at multiple positions on an inner side of the second insulating container(s) (110b, 310b).</li></ul>

Advantageous Effects of Invention

According to the present invention, even if the fastener chain is not in a state where the elements are electrically connected to each other in advance, the individual elements will be reliably subjected to power supply while bringing the individual elements into sufficient contact with the plating solution when electroplating the fastener chain, so that a highly uniform plating film can be formed in a short period of time. Further, the size of the plating device can be decreased, so that installation costs and maintenance costs can be reduced. The conductive media may also be plated, but the conductive media are flowably accommodated and can be separately removed from the plating device, which also provides an advantage of easy maintenance of the device. Therefore, the present invention will contribute to enable proposal of inexpensive fastener products having a wide variety of color tones to users.

BRIEF DESCRIPTION OF DRAWINGS

<ul id="ul0007" list-style="none" compact="compact"><li><figref idref="f0001">FIG. 1</figref> is a schematic front view of a metal fastener.</li><li><figref idref="f0002">FIG. 2</figref> is a cross-sectional view of an insulating container as viewed from a direction facing a conveying direction of a fastener chain when the fastener chain passes straight through the insulating container of a fixed cell type plating device.</li><li><figref idref="f0003">FIG. 3</figref> is a schematic cross-sectional view taken along the line A-A' of the insulating container shown in <figref idref="f0002">FIG. 2</figref>.</li><li><figref idref="f0004">FIG. 4</figref> is a schematic cross-sectional view taken along the line B-B' when conductive media and a fastener chain are removed from the insulating container shown in <figref idref="f0002">FIG. 2</figref>.</li><li><figref idref="f0005">FIG. 5</figref> shows a first overall structural example of a fixed cell type electroplating device.</li><li><figref idref="f0006">FIG. 6</figref> shows a second overall structural example of a fixed cell type electroplating device.</li><li><figref idref="f0007">FIG. 7</figref> shows a third overall structural example of a fixed cell type electroplating device.</li><li><figref idref="f0008">FIG. 8</figref> shows a fourth overall structural example of a fixed cell type electroplating device.</li><li><figref idref="f0009">FIG. 9</figref> shows a fifth overall structural example of a fixed cell type electroplating device.</li><li><figref idref="f0010">FIG. 10</figref> shows a sixth overall structural example of a fixed cell type electroplating device.</li><li><figref idref="f0011">FIG. 11</figref> is a schematic view illustrating principle of preferentially plating an upper surface of a fastener chain in a rotary barrel type electroplating device.</li><li><figref idref="f0012">FIG. 12</figref> is a schematic view illustrating principle of preferentially plating a lower surface of a fastener chain in a rotary barrel type electroplating device.</li><li><figref idref="f0013">FIG. 13</figref> shows an overall structural example of a rotary barrel type electroplating device.</li><li><figref idref="f0014">FIG. 14</figref> shows an overall structure of an electroplating device according to Comparative Example.</li><li><figref idref="f0015">FIG. 15</figref> schematically shows a change in a conveying direction of current flowing through elements in a case where one negative electrode is disposed on an inner surface on a front side in the conveying direction, among inner surfaces of insulating containers.</li><li><figref idref="f0016">FIG. 16</figref> schematically shows a change in a conveying direction of current flowing though elements in case where at least one negative electrode is disposed on an inner side surface on a front side in a passing direction of a fastener chain; and on a rear portion of an inner side surface parallel to the passing direction of the fastener chain, among inner side surfaces of first insulating containers.</li><li><figref idref="f0017">FIG. 17</figref> schematically shows a change in a conveying direction of current flowing though elements in case where at least one negative electrode is disposed on an inner side surface on a front side in a passing direction of a fastener chain; as well as on a central portion and a rear portion of an inner side surface parallel to the passing direction of the fastener chain, among inner side surfaces of first insulating containers.</li><li><figref idref="f0018">FIG. 18</figref> is a plan view showing arrangement of negative electrodes in the embodiment of <figref idref="f0017">FIG. 17</figref>.</li></ul>

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

(1. Metal Fastener)

<figref idref="f0001">FIG. 1</figref> exemplarily shows a schematic front view of a metal fastener. As shown in <figref idref="f0001">FIG. 1</figref>, the metal fastener includes: a pair of fastener tapes 1 each having a core portion 2 formed on an inner edge side; rows of metal elements 3 caulked and fixed to the core portions 2 of the fastener tapes 1 at predetermined spaces; upper stoppers 4 and a lower stopper 5 caulked and fixed to the core portions 2 of the fastener tapes 1 at upper ends and lower ends of the rows of the metal elements, respectively; and a slider 6 disposed between the rows of the pair of opposing elements 3 and slidable in an up and down direction for engaging and disengaging the pair of metal elements 3. An article in which the row of the elements 3 has been attached to the core portion 2 of one fastener tape 1 is referred to as a fastener stringer, and an article in which the rows of the elements 3 attached to the core portions 2 of a pair of fastener tapes 1 have been engaged with each other is referred to as a fastener chain 7. It should be noted that the lower stopper 5 may be an openable, closable and fittingly insertable tool consisting of an insert pin, a box pin and a box body, so that the pair of slide fastener chains can be separated by engaging and disengaging operations of the slider. Other embodiments that are not shown are also possible.

Materials of the metal elements 3 that can be used include, but not particularly limited to, copper (pure copper), copper alloys (red brass, brass, nickel white, and the like) and aluminum alloys (Al-Cu alloys, Al-Mn alloys, Al-Si alloys, Al-Mg alloys, Al-Mg-Si alloys, AI-Zn-Mg alloys, AI-Zn-Mg-Cu alloys and the like), zinc, zinc alloys, iron, iron alloys, and the like.

The metal elements can be subjected to various electroplating. The plating can be performed aiming at a rust prevention effect, a crack prevention effect, and a sliding resistance reduction effect, in addition to the design purpose of obtaining a desired color tone. A type of plating is not particularly limited and may be any of single metal plating, alloy plating and composite plating. Examples of the plating includes Sn plating, Cu-Sn alloy plating, Cu-Sn-Zn alloy plating, Sn-Co alloy plating, Rh plating, and Pd plating. Further examples of the plating includes Zn plating (including a zincate treatment), Cu plating (including copper cyanide plating, copper pyrophosphate plating, and copper sulfate plating), Cu-Zn alloy plating (including brass plating), Ni plating, Ru plating, Au Plating, Co plating, Cr plating (including a chromate treatment), Cr-Mo alloy plating and the like. The type of plating is not limited to those, and other various metal plating can be performed in accordance with the purpose.

The slide fastener can be attached to various articles, and particularly functions as an opening/closing tool. The articles to which the slide fastener is attached include, but not limited to, daily necessities such as clothes, bags, shoes and miscellaneous goods, as well as industrial goods such as water storage tanks, fishing nets and space suites.

(2. Plating Method)

As a plating method for a metal fastener, the prevent invention proposes a method for continuously electroplating the fastener chain having the rows of the metal elements while conveying the fastener chain.

In one embodiment, the electroplating method according to the present invention includes a step of causing the fastener chain to pass through one or more first insulating container(s) while bringing each metal element into contact with a plating solution in a plating bath, he first insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode, for the purpose of mainly plating the surface of the element row exposed on one main surface side of the fastener chain.

In another embodiment, the electroplating method according to the present invention further includes a step of causing the fastener chain to pass through one or more second insulating container(s) while bringing each metal element into contact with a plating solution in a plating bath, the second insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode, for the purpose of mainly plating the surface of the element row exposed on the other main surface side of the fastener chain.

By carrying out these two steps, it is possible to plate the surface of the element rows exposed on both main surface sides of the fastener chain. Moreover, by carrying out both of the steps using different plating solutions, it is possible to form different a plating film on one main surface of the fastener chain that is different from that on the other main surface of the fastener chain.

Conditions such as a composition and a temperature of the plating solution and the like may be appropriately set by those skilled in the art depending on types of metal components to be deposited on each element, and are not particularly limited.

Materials of the conductive media are not particularly limited, and are generally metals. Among the metals, iron, stainless steel, copper and brass are preferable, and iron is more preferable, because they have higher corrosion resistance and higher abrasion resistance. However, when using conductive media made of iron, the contact of the conductive media with the plating solution will lead to formation of a displacement-plating film having poor adhesion on surfaces of iron balls. The plating film peels off from the conductive media during electroplating of the fastener chain to form fine metal pieces which float in the plating solution. The floating of the metal pieces in the plating solution leads to adhesion to the fastener tapes, and it is thus preferable to prevent the floating. Therefore, when using the conductive media made of iron, it is preferable that the conductive media have been previously subjected to copper pyrophosphate plating, copper sulfate plating, nickel plating or tin-nickel alloy plating in order to prevent the displacement plating. Although the displacement plating can also be prevented by copper cyanide plating on the conductive media, it leads to relatively large irregularities on the surfaces of the conductive media so that rotation of the conductive media is inhibited. Therefore, , copper pyrophosphate plating, copper sulfate plating, nickel plating, or tin-nickel alloy plating is preferred.

Materials of the first insulating container(s) and the second insulating container(s) include, preferably, high density polyethylene (HDPE), heat resistant hard polyvinyl chloride, and polyacetal (POM), and more preferably high density polyethylene (HDPE), in terms of chemical resistance, abrasion resistance, and heat resistance.

A plurality of conductive media flowably accommodated in the first insulating container(s) and in the second insulating container(s) are in electrical contact with the negative electrode, so that power can be supplied from the negative electrode to each element via the conductive media. The negative electrode may be disposed at a non-limiting position, but it is desirable to dispose the negative electrode at a position where the electrical contact with each conductive medium is not interrupted in each insulating container.

For example, when using a fixed cell type electroplating device as described below, the fastener chain passing through the first insulating container(s) and the second insulating container(s) in the horizontal direction leads to movement of the conductive media to the front side in the conveying direction and to accumulation there. The fastener chain passing through the first insulating container(s) and the second insulating container(s) vertically upward leads to tendency of the conductive media accumulated downward.

Therefore, when the fastener chain passes in the horizontal direction, the negative electrode is preferably disposed at least on the front inner side in the conveying direction where the conductive media are easily accumulated, among the inner sides of the insulating container(s). When the fastener chain passes vertically upward, the negative electrode is preferably disposed at least on the lower inner side of the insulating container where the conductive media are easily accumulated, among the inner side s of the insulating container(s). The shape of the negative electrode is not particularly limited, and it may be, for example, a plate shape.

The fastener chain can also travel in an oblique direction in the middle of the horizontal direction and the vertical direction. In this case, the position where the conductive media are easily accumulated varies depending on the inclination, traveling speed, number and size of the conductive media. Therefore, the position where the positive electrode is disposed may be adjusted according to the actual conditions.

The magnitude of the current flowing through the conductive media contained in the first insulating container(s) and the second insulating container(s) decreases as the distance from the negative electrode increases. Therefore, the current flowing through each element via the conductive media also decreases as the distance from the negative electrode increases. For example, when a negative electrode is disposed at one position on the inner side surface on the front side in the conveying direction among the inner sides of the insulating container(s), the current in the element located at the front side is the largest, and the current decreases toward the rear side, as schematically shown in <figref idref="f0015">FIG. 15</figref>. According to results of intensive studies by the present inventors, provided that a distance in the conveying direction from the negative electrode at which a current becomes 0 when the current flowing through the negative electrode is I₀ (in other words, the maximum distance in the conveying direction from the negative electrode where the element is plated) is defined as D₀, and a distance in the conveying direction from the negative electrode at which the current becomes 0 when the current flowing through the negative electrode is I₁ is defined as D₁, the following empirical formula is established between them: <maths id="math0001" num="[Formula 1]"><math display="block"><msub><mi mathvariant="bold-italic">D</mi><mn>1</mn></msub><mo>=</mo><msub><mi mathvariant="bold-italic">D</mi><mn>0</mn></msub><mo>×</mo><msqrt><mfrac><msub><mi mathvariant="bold-italic">I</mi><mn>1</mn></msub><msub><mi mathvariant="bold-italic">I</mi><mn>0</mn></msub></mfrac></msqrt></math><img file="EP3556907A1_D0001.tif" /></maths>

Thus, as the distance from the negative electrode increases, the current flowing through the elements decreases, so that a plating efficiency decreases at the low current portion. To increase the plating efficiency, it is desirable to eliminate the low current portion. It is also conceivable to increase the current on the rear side by increasing the current on the front side. However, this will further increase the current on the front side, which may cause burnt plating. Therefore, it is desirable that the negative electrode used for the first insulating container(s) (second insulating container(s)) be disposed at multiple positions on the inner side of the first insulating container(s) (second insulating container(s)) to improve uniformity of the current flowing through the elements passing through the first insulating container(s) (second insulating container(s)). The higher uniformity of the current flow through the elements also allows the maximum current that will not cause burn plating to flow through all of the elements passing through the insulating container(s). As the plating efficiency is improved, time required to grow a plating film having the same thickness is shortened, so that a conveying speed of the fastener chain can be increased to improve a production efficiency. The effect of making the current uniform by providing the negative electrodes is more remarkable as the plating solution has lower conductivity.

According to a preferable embodiment, the relationship: 0.8 ≤ D_min / D_max ≤ 1.0 is satisfied, in which D_max represents a current density (a current flowing through an element / a surface area of an element) of an element having the highest current among the elements passing through the first insulating container(s), and D_min represents a current density of an element having the lowest current among the elements passing through the first insulating container(s). More preferably, 0.9 ≤ D_min / D_max ≤ 1.0 is satisfied, and further more preferably, 0.95 ≤ D_min / D_max ≤ 1.0 is satisfied

An increase in the conveying speed by uniform current will be discussed. For example, in the case where the negative electrode is disposed at one position on the inner side surface on the front side in the conveying direction among the inner sides of the insulating container(s), assuming that the current is 10 A/dm² for the element near the negative electrode and the current is 3 A/dm² for the element near the outlet, then an average current density is (10 + 3) / 2 = 6.5 A/dm². In contrast, when the average current density is 10 A/dm² by arranging a plurality of negative electrodes, the conveying at a speed of 10 / 6.5 = 1.54 times is possible to obtain a plating film having the same thickness.

In a preferred embodiment, the negative electrode is disposed at least on the front inner side and the rear inner side of the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (the second insulating container(s)). This can lead to improved uniformity of the electric current in the conveying direction of the fastener chain. For example, <figref idref="f0016">FIG. 16</figref> schematically shows a change in the conveying direction of the current flowing though the elements in case where the negative electrode is disposed on the front inner side in the passing direction of the fastener chain; and on the rear portion of the inner side parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s). In this case, the current (shown by the dotted lines) derived from each negative electrode decreases as it goes away from each negative electrode, but when the currents are summed up, the uniformity of the current flowing to the element passing through the insulating container(s) is improved as shown by the solid line. The negative electrode may be disposed on the rear inner side of the first insulating container (second insulating container). However, the conductive media tend to accumulate on the front side, thereby decreasing a possibility that the rear inner side is contacted with the conductive media. Therefore, it is preferable to dispose the negative electrode on the rear portion of the inner side parallel to the passing direction of the fastener chain. In this case, the negative electrode at the rear portion is preferably disposed within a range of from 0 to 30%, more preferably from 0 to 20%, from the rear side in the passing direction of the fastener chain, relative to 100% of a length of the inner side in the passing direction of the fastener chain.

When the insulating container is long in the conveying direction, only disposing of the negative electrode on the front inner side of the fastener chain in the passing direction and on the rear side of the inner side parallel to the fastener chain in the passing direction may not allow sufficient uniformity of the current flowing to the elements passing through the insulating container(s). In such a case, it is preferable that the negative electrode is disposed at one or more additional position(s) on the inner side of the first insulating container (second insulating container) parallel to the passing direction of the fastener chain. The number of the negative electrodes disposed on the inner side parallel to the passing direction of the fastener chain may be determined according to the length of the insulating container in the conveying direction and the desired current. Further, when three or more negative electrodes are disposed, a plurality of negative electrodes are preferably disposed at equal intervals in the passing direction of the fastener chain in order to improve the uniformity of the current flowing to the elements passing through the insulating container(s).

<figref idref="f0017">FIG. 17</figref> schematically shows a change in the conveying direction of the current flowing though the elements in case where the negative electrode is disposed on the front inner side in the passing direction of the fastener chain; as well as on the central portion and the rear portion of the inner side parallel to the passing direction of the fastener chain, among the inner sides of the insulating container(s). According to this embodiment, even if the current (indicated by the dotted lines) derived from the electrode disposed on the front inner side in the passing direction of the fastener chain and on the rear portion of the inner side parallel to the passing direction of the fastener chain is greatly decreased at the central position in the passing direction of the inner fastener chain, the disposing of the negative electrode on the central portion of the inner side parallel to the passing direction of the fastener chain can allow flowing of the current (indicated by the dashed line) derived from the negative electrode. Thus, when the currents derived from the three negative electrodes are summed up, the uniformity of the current in the conveying direction of the fastener chain can be improved as shown by the solid line. In the embodiment where the three negative electrodes are disposed, the negative electrode disposed on the inner side parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (the second insulating container(s)), is preferably disposed within a range of from 30 to 70%, more preferably from 40 to 60%, from the front side in the passing direction of the fastener chain, relative to 100% of the length of the inner side in the passing direction of the fastener chain, in terms of improving the uniformity of the current.

The negative electrode disposed on the inner side parallel to the passing direction of the fastener chain, among the inner sides of the first insulating container(s) (the second insulating container(s)), is preferably disposed so as to be flush with the inner side (see <figref idref="f0018">FIG. 18</figref>). This prevents the flow of the conductive media from being hindered by the negative electrodes.

The conductive media are flowable in each insulating container, and as the fastener chain travels, the conductive media constantly changes the contact position with each element while being flowed and/or rotated and/or moved up and down. This can allow growth of a plating film having high uniformity because the position of current passing and the contact resistance are also changed constantly. The shape of each conductive medium is not limited as long as the conductive media are contained in the container(s) in a flowable state, but preferably it is spherical in terms of flowability.

An optimum dimension of each conductive medium varies depending on a chain width of the fastener chain, as well as a width and pitch of the slider sliding direction of the elements. When using a fixed cell type electroplating device as described below, the diameter of each conducive medium is preferably equal to or more than the chain thickness in order to prevent the conductive media from entering the traveling path of the fastener chain and the traveling path from being clogged by the conductive media while the fastener chain passes through the first insulating container(s) and the second insulating container(s).

The number of conductive media to be accommodated in the first insulating container(s) and the second insulating container(s) is not particularly limited, and is preferably set as needed in view of being able to supply power to each element of the fastener chain, in particular of ensuring a sufficient quantity of the conductive media to maintain constant contact with each element during passing through the first insulating container(s) and the second insulating container(s) even if the conductive media move in the traveling direction. On the other hand, it is preferable that an appropriate pressing pressure is applied from the conductive media to each element of the fastener chain because it allows facilitation of flow of electricity, but an excessive pressing pressure increases conveying resistance to hinder smooth conveying of the fastener chain. Therefore, it is preferable that the fastener chain can smoothly pass through the first insulating container(s) and the second insulating container(s) without experiencing the excessive conveying resistance. From the above point of view, illustratively, the quantity of the conductive media accommodated in each insulating container is preferably such that 3 or more layers (in other words, a lamination thickness of 3 or more times as large as the diameter of the conductive medium), and typically from 3 to 8 layers (in other words, a lamination thickness of form 3 to 8 times as large as the diameter of the conductive medium) can be formed when the conductive media spread over the elements.

When using a fixed cell type electroplating device as described below, the horizontal passing of the fastener chain through the first insulating container(s) and the second insulating container(s) moves the conductive media to the front portion in the conveying direction to facilitate accumulation. Thus, the weight of the conductive media accumulated in the front portion presses the fastener chain, and the conveying resistance to the fastener chain increases. Further, when current flows from the negative electrode to the conductive media, a longer length of a cell drops voltage, thereby decreasing a plating efficiency. Therefore, the connecting of two or more of each of the first insulating container(s) and the second insulating container(s) in series can allow a decrease in conveying resistance due to the weight of the conductive media, and can allow an increased plating efficiency. It is also possible to adjust the thickness of the plating film and the traveling speed of the fastener chain by increasing or decreasing a connecting number of two or more of insulating containers connected in series.

In terms of reducing the conveying resistance, it is desirable to provide an upward angle in the traveling direction of the fastener chain passing through each insulating container, that is, the fastener chain passing through each insulating container while rising. Thus, the conductive media which are easy to move in the conveying direction falls to the rear in the conveying direction due to its own weight, so that the conductive media are not likely to accumulate at the front portion of the conveying direction. The inclination angle may be appropriately set according to the conveying speed, the size and number of conductive media, and the like. When the conductive media are spherical and the quantity of the conductive media are such that from 3 to 8 layers can be formed over the elements, the inclination angle is preferably 9° or more, and typically 9° or more and 45° or less, in terms of maintaining the contact of the conductive media with the elements passing through the first insulating container(s) and the second insulating container(s) even if the conductive media move in the traveling direction during traveling of the fastener chain.

In terms of designing a more compact plating device, there is also a method in which the fastener chain passes through each insulating container while rising in the vertical direction. According to the method, the plating bath is elongated in the vertical direction and shortened in the horizontal direction, so that a footprint for disposing the plating device can be reduced.

In one embodiment of the plating method according the present invention, during the fastener chain passing through the first insulating container(s), power is supplied by mainly bringing the surface of each metal element exposed on the first main surface side of the fastener chain into contact with the conductive media in the first insulating container(s). During the step, the first positive electrode is disposed in a positional relationship so as to face the surface of each metal element exposed on the second main surface side of the fastener chain, so that regular flows of cations and electrons are generated, and a plating film can be rapidly grown on the surface of each metal element exposed on the second main surface side of the fastener chain. In terms of suppressing the plating of the conductive media, the first positive electrode should be preferably disposed only in the positional relationship so as to face the surface of each metal element exposed on the second main surface side of the fastener chain.

Further, in another embodiment of the plating method according to the present invention, during the fastener chain passing through the second insulating container(s), power is supplied by mainly bringing the surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media in the second insulating container(s). During the step, the second positive electrode is disposed at a positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain, so that regular flows of cations and electrons are generated, and a plating film can be rapidly grown on the surface of each metal element exposed on the first main surface side of the fastener chain. In terms of suppressing the plating on excessive areas other than the elements, the second positive electrode should be preferably disposed only in the positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain.

When a plurality of conductive media is randomly brought into contact with both main surfaces of the fastener chain, flows of cations and electrons will also be random, so that a growth speed of an electroplating film is slow down. Therefore, it is preferable that the surface exposed on one main surface side is preferentially contacted with the conductive media as much as possible. Therefore, during the fastener chain passing through the first insulating container(s), 60% or more, and preferably 80% or more, and more preferably 90% or more, and even more preferably all of the total number of conductive media in the first insulating container(s) are configured to be contactable with the surface of each metal element exposed on the first main surface side of the fastener chain. The expression "all of the conductive media in the first insulating container(s) are configured to be contactable with the surface of each metal element exposed on the first main surface side of the fastener chain" means that only the surface of the metal elements exposed on the first main surface side is brought into contact with the conductive media in the first insulating container(s).

Similarly, during the fastener chain passing through the second insulating container(s), 60% or more, and preferably 80% or more, and more preferably 90% or more, and even more preferably all of the total number of conductive media in the second insulating container(s) are configured to be contactable with the surface of each metal element exposed on the second main surface side of the fastener chain. The expression "all of the conductive media in the second insulating container(s) are configured to be contactable with the surface of each metal element exposed on the second main surface side of the fastener chain" means that only the surface of the metal elements exposed on the second main surface side is brought into contact with the conductive media in the second insulating container(s).

The shortest distance between the surface of each metal element exposed on the second main surface side of the fastener chain and the first positive electrode, and the shortest distance between the surface of each metal element exposed on the first main surface side of the fastener chain and the second positive electrode are preferably shorter, respectively, because they can allow efficient plating on each metal element and can allow suppression of plating on unnecessary portions (for example, conductive media). The increased plating efficiency can save maintenance costs, chemicals and electricity for the conductive media. Specifically, the shortest distance between each metal element and the positive electrode is preferably 10 cm or less, and more preferably 8 cm or less, and still more preferably 6 cm or less, and even more preferably 4 cm or less. In this case, it is desirable from the viewpoint of plating efficiency that the first positive electrode and the second positive electrode be disposed so as to extend in parallel to the fastener chain conveying direction.

(3. Plating Device)

Now, embodiments of an electroplating device suitable for carrying out the electroplating method of the fastener chain including the rows of the metal elements according to the present invention will be described. However, the descriptions of the same components as those described in the embodiments of the electroplating method also apply to those of the embodiments of the electroplating device, and redundant descriptions will be thus omitted in principle.

In one embodiment, the electroplating device according to the present invention includes: <ul id="ul0008" list-style="none" compact="compact"><li>a plating bath capable of accommodating a plating solution;</li><li>a first positive electrode disposed in the plating bath; and</li><li>one or more first insulating container(s) disposed in the plating bath, the first insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode.</li></ul>

In the present embodiment, the first insulating container(s) are configured to enable the fastener chain to pass through the first insulating container(s) while mainly bringing a surface of each metal element exposed on the first main surface side of the fastener chain into contact with the conductive media in the first insulating container(s). Further, in the present embodiment, the first positive electrode is disposed in a positional relationship so as to face the surface of each metal element exposed on the second main surface side of the fastener chain during the fastener chain passing through the first insulating container(s). According to the present embodiment, the surface of the element rows exposed on one main surface side of the fastener chain can be mainly plated.

In another embodiment, the electroplating device according to the present invention further includes: <ul id="ul0009" list-style="none" compact="compact"><li>a second positive electrode disposed in the plating bath; and</li><li>one or more second insulating container(s) disposed in the plating bath, each of the second insulating container(s) flowably accommodating a plurality of conductive media in electrical contact with a negative electrode.</li></ul>

In the present embodiment, the second insulating container(s) are configured to enable the fastener chain to pass through each of the second insulating container(s) while mainly bringing a surface of each metal element exposed on the second main surface side of the fastener chain into contact with the conductive media in the second insulating container(s). Further, in the present embodiment, the second positive electrode is disposed in a positional relationship so as to face the surface of each metal element exposed on the first main surface side of the fastener chain during passing the fastener chain through the second insulating container(s). According to the present embodiment, the surfaces of the element rows exposed on both main surface sides of the fastener chain can be plated.

(3-1. Fixed Cell Type Plating Device)

Now, a specific structural example of the electroplating device according to the present invention will be described. First, a fixed cell type electroplating device will be described. The fixed cell type is advantageous in that only the surface of each metal element exposed on one of the main surfaces can be brought into contact with the conductive media in the insulating container(s). In the fixed cell type plating device, the insulating container(s) are fixed in the plating device and does not involve movement such as rotation. The structure of the insulating container (which can be used for any of the first and second insulating container) according to a structural example of the fixed cell type plating device is schematically shown in <figref idref="f0002 f0003 f0004">FIGS. 2 to 4</figref>. <figref idref="f0002">FIG. 2</figref> is a schematic cross-sectional view of the insulating container of the fixed cell type plating device as viewed from a direction facing the conveying direction of the fastener chain. <figref idref="f0003">FIG. 3</figref> is a schematic cross-sectional view taken along the line A-A' of the insulating container shown in <figref idref="f0002">FIG. 2</figref>. <figref idref="f0004">FIG. 4</figref> is a schematic cross-sectional view taken along the line B-B' when the conductive media and the fastener chain are removed from the insulating container shown in <figref idref="f0002">FIG. 2</figref>.

Referring to <figref idref="f0002">FIGS. 2</figref> and <figref idref="f0003">3</figref>, an insulating container 110 includes: a passage 112 for guiding a traveling path of a fastener chain 7; and an accommodating portion 113 for flowably accommodating a plurality of conductive media 11, inside the insulating container 110. The passage 112 includes: the inlet 114 for the fastener chain; the outlet 115 for the fastener chain; one or more opening(s) 117 on a passage surface 112a facing one (first or second) main surface side of the fastener chain 7, the opening(s) 117 enabling access to the conductive media 111; and one or more opening(s) 116 on a passage surface 112b facing the other (second or first) main surface side of the fastener chain 7, the opening(s) 116 enabling fluid communication with the plating solution and current flow. The passage surface 112b may be provided with a guide groove 120 extending along the conveying direction for guiding the conveying direction of the elements 3.

One or more opening(s) 117 enabling access to the conductive media 111 preferably satisfies the relationship: 2D &lt; W2 &lt; 6D, more preferably 2D &lt; W2 &lt; 3D, even more preferably 2.1D ≤ W2 ≤ 2.8D, in which W2 represents a length in a chain width direction, and D represents a diameter of the conductive medium 111, because power supply is easily stabilized while ensuring a space for movement and rotation of the balls when arranging from 3 to 6 balls in the chain width direction so as to partially overlap with one another. Here, the chain width refers to a width of the engaged elements as defined in JIS 3015: 2007. Further, the diameter of the conductive medium is defined as a diameter of a true sphere having the same volume as the conductive medium to be measured.

The fastener chain 7 entering the insulating container 110 from the inlet 114 travels in the direction of the arrow in the passage 112 and exits the outlet 115. While the fastener chain 7 passes through the passage 112, the conductive media 111 held in the accommodating portion 113 can be brought into contact with the surface of each element 3 exposed on one main surface side of the fastener chain 7 through the opening(s) 117. However, there is no opening where the conductive media 111 can access the surface of each element 3 exposed on the other main surface side of the fastener chain 7. Therefore, the conductive media 111 held in the accommodating portion 113 cannot be brought into contact with the surface of each element 3 exposed on the other main surface side of the fastener chain 7.

The conductive media 111 are dragged by the fastener chain 7 traveling in the passage 112 and moved to the front in the conveying direction and are likely to accumulate there. However, excessive accumulation leads to clogging of the conductive media 111 at the front and to strong pressing of the fastener chain 7, so that the conveying resistance of the fastener chain 7 is increased. Therefore, as shown in <figref idref="f0003">FIG. 3</figref>, the outlet 115 is provided at a position higher than the inlet 114 to incline the passage 112 upward, whereby the conductive media 111 contained in the insulating container 110 is returned back in the conveying direction, so that the conveying resistance can be reduced. It is also possible to provide the outlet 115 vertically above the inlet 114 so that the conveying direction of the fastener chain 7 is vertically upward, which makes it easy to control the conveying resistance and provides an advantage of only requiring a small footprint.

Referring to <figref idref="f0004">FIG. 4</figref>, a plate-shaped positive electrode 118 is disposed on a front inner side 113a in the conveying direction among inner sides of the accommodating portion 113. The conductive media 111 can be in electrical contact with the plate-shaped negative electrode 118. Further, while the fastener chain 7 passes through the passage 112, the conductive media 111 can be electrically contacted with the surface of each element 3 exposed on one main surface side of the fastener chain 7. When at least a portion of the conductive media 111 is electrically contacted with both of those conductive media 111 to create an electrical path, power can be supplied to the respective elements 3 while the fastener chain 7 passes through the passage 112.

In a typical embodiment, the fastener chain 7 is electroplated while being immersed in a plating solution. While the fastener chain 7 passes through the passage 112 of the insulating container 110, the plating solution can be contacted with each element 3 by entering the passage 112 through the opening(s) 116. By providing a positive electrode 119 on a side facing the other (second or first) main surface side of the fastener chain 7, cations in the plating solution efficiently reach the other main surface side of the fastener chain, so that the plating film can be rapidly grown on the surface of each element 3 exposed on the main surface side.

It is advantageous for smooth conveying of the fastener chain 7 that the opening(s) 116 formed on the passage surface 112b is provided so as not to catch the fastener chain 7 traveling in the passage 112. From this point of view, each opening 116 is preferably a circular hole, and can be, for example, a circular hole with a diameter of from 1 to 3 mm.

Further, it is preferable to provide the opening(s) 116 formed on the passage surface 112b so that electricity flows with high uniformity throughout the elements 3 of the fastener chain 7 traveling in the passage 112 in order to obtain a highly uniform plating film. From such a point of view, a ratio of an area of the opening(s) 116 to an area including the opening(s) 116 on the passage surface 112b (hereinafter referred to as an opening ratio) is preferably 40% or more, and more preferably 50% or more. However, the opening ratio is preferably 60% or less, for reasons of ensuring strength. Further, as shown in <figref idref="f0004">FIG. 4</figref>, the opening(s) 116 are preferably arranged along the conveying direction of the fastener chain 7 (three rows in <figref idref="f0004">FIG. 4</figref>), and are more preferably arranged in a staggered array from the viewpoint that current flows on the entire exposed surface of the elements 3 to facilitate plating.

Preferably, the conductive media 111 are not contacted with the fastener tape 1 while the fastener chain 7 travels in the passage 112. This is because when the conductive media 111 are contacted with the fastener tape 1, the conveying resistance of the fastener chain is increased. Therefore, the opening(s) 117 are preferably disposed at a position where the conductive media 111 cannot be contacted with the fastener tape. When viewing the insulating container from the direction facing the conveying direction of the fastener chain (see <figref idref="f0002">FIG. 2</figref>), each of gaps C1 and C2 in the chain width direction from both side walls of the opening 117 to both ends of the element 3 is preferably equal to or less than the radius of each conductive medium. However, a narrower distance between both side walls of the opening 117 leads to a decreased contact frequency of the conductive media 111 with the elements 3. Therefore, each of the gaps C1 and C2 is preferably 0 or more, and more preferably larger than 0. The radius of the conductive medium is defined as a radius of a true sphere having the same volume as that of the conductive medium to be measured.

Preferably, the distance between the passage surface 112a and the passage surface 112b is shorter than the diameter of the conductive medium so that the conductive medium does not enter the passage 112. This is because if the conductive medium enters the passage 112, the conveying resistance is significantly increased, which causes the conveying of the fastener chain 7 to be difficult.

<figref idref="f0005 f0006 f0007 f0008 f0009 f0010">FIGS. 5 to 10</figref> show some examples of the overall configuration of the fixed cell type electroplating device. In the embodiment shown in <figref idref="f0005 f0006 f0007 f0008 f0009 f0010">FIGS. 5 to 10</figref>, the fastener chain 7 is conveyed in the direction of the arrow under tension in the plating bath 201 containing a plating solution 202. The tension is preferably a load of from 0.1N to 0.2N.

In the embodiment shown in <figref idref="f0005">FIG. 5</figref>, the fastener chain 7 enters the plating solution 202 and then proceeds vertically downward to the bottom of the plating bath 201. After reaching the bottom, the fastener chain 7 is inverted and proceeds vertically upward to pass through the first insulating container 110a and the second insulating container 110b in this order, and left from the plating solution 202.

In the electroplating device shown in <figref idref="f0005">FIG. 5</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. Further, each interior of the first insulating container 110a and the second insulating container 110b is divided into two sections A and B connected in series. The surface of each metal element exposed on one main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath, so that the installation space can be reduced. An insulating partition plate 121 for electrical disconnection to prevent mutual influence is provided between the first insulating container 110a and the second insulating container 110b. The material of the partition plate 121 is not particularly limited as long as it is an insulator, and the partition plate 121 may be made of a resin such as a vinyl chloride resin, for example.

In the embodiment shown in <figref idref="f0006">FIG. 6</figref>, the fastener chain 7 enters the plating solution 202, and then proceeds vertically downward to the bottom of the plating bath 201. After reaching the bottom, the fastener chain 7 is inverted and proceeds vertically upward to pass through the first insulating container 110a. Once the fastener chain 7 comes out of the plating solution 202, it is inverted to enter the plating solution 202 again, and proceeds vertically downward to the bottom of the plating bath 201. After reaching the bottom, the fastener chain 7 is inverted again, and proceeds vertically upward to pass through the second insulating container 110b, and left from the plating solution 202.

In the embodiment shown in <figref idref="f0006">FIG. 6</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. Further, each interior of the first insulating container 110a and the second insulating container 110b is divided into two sections A and B connected in series. The surface of each metal element exposed on one main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. According to this embodiment, double-sided plating can be performed in one plating bath.

In the embodiment shown in <figref idref="f0007">FIG. 7</figref>, the fastener chain 7 enters the plating solution 202, and then proceeds vertically downward to the bottom of the plating bath 201. After reaching the bottom, the fastener chain 7 is inverted and proceeds vertically upward to pass through a first set of the first insulating container 110a and the second insulating container 110b in this order. Once the fastener chain 7 comes out of the plating solution 202, it is inverted to enter the plating solution 202 again, and proceeds vertically downward to the bottom of the plating bath 201. After reaching the bottom, the fastener chain 7 is inverted again, and proceeds vertically upward to pass through a second set of the first insulating container 110a and the second insulating container 110b, and left from the plating solution 202.

In the embodiment shown in <figref idref="f0007">FIG. 7</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b. An insulating partition plate 121 for electrical disconnection to prevent mutual influence is provided between the first insulating container 110a and the second insulating container 110b. Further, the insulating partition plate 121 for electrical disconnection to prevent mutual influence is also provided between the first set and the second set. According to this embodiment, double-sided plating can be performed in one plating bath.

In the embodiment shown in <figref idref="f0008">FIG. 8</figref>, the plating bath 201 is divided into a first plating bath 201a, a second plating bath 201b, and a third plating bath 201c. The fastener chain 7 enters a plating solution 202a in the first plating bath 201a, and then proceeds vertically downward to the bottom of the first plating bath 201a. After reaching the bottom, the fastener chain is inverted and proceeds vertically upward to pass through the two first insulating container(s) 110a arranged in series, and left from the plating solution 202a. The fastener chain 7 then enters a plating solution 202b from an inlet 204 provided on a side wall of the second plating bath 201b, and passes obliquely upward through the three second insulating container(s) 110b arranged in series, and exits an outlet 205 provided on a side wall of the second plating bath 201b. The outlet 205 is at a higher position than the inlet 204. Then, after entering the plating solution 202c in the third plating bath 201c, the fastener chain 7 proceeds vertically downward to the bottom of the third plating bath 201c. After reaching the bottom, the fastener chain is inverted and proceeds vertically upward to pass through the two first insulating container(s) 110a arranged in series, and left from the plating solution 202c.

In the embodiment shown in <figref idref="f0008">FIG. 8</figref>, the plating solution overflows from the inlet 204 and the outlet 205 for the second plating bath 201b. The overflowing plating solution is collected into a storage tank 203 through a return pipe 210, and then fed to the second plating bath 201b again through a feed pipe 212 by a circulation pump 208. A heater 209 may be disposed in the storage tank 203 to heat the plating solution therein.

In the embodiment shown in <figref idref="f0008">FIG. 8</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b.

In the embodiment shown in <figref idref="f0009">FIG. 9</figref>, the plating bath 201 is divided into a first plating bath 201a and a second plating bath 201b. The fastener chain 7 enters the plating solution 202a from an inlet 206 provided on the side wall of the first plating bath 201a and passes obliquely upward through the three first insulating container(s) 110a arranged in series, and exits an outlet 207 provided on the side wall of the plating bath 201a. The outlet 207 is at a higher position than the inlet 206. Then, after entering the plating solution 202b in the second plating bath 201b, the fastener chain 7 proceeds vertically downward to the bottom of the second plating bath 201b. After reaching the bottom, the fastener chain 7 is inverted and proceeds vertically upward to pass through the three second insulating container(s) 110b arranged in series, and exits the plating solution 202b.

In the embodiment shown in <figref idref="f0009">FIG. 9</figref>, the plating solution overflows from the inlet 206 and the outlet 207 for the first plating bath 201b. The overflowing plating solution is collected into a storage tank 203 through a return pipe 210, and then fed to the first plating bath 201a again through a feed pipe 212 by a circulation pump 208. A heater 209 may be disposed in the storage tank 203 to heat the plating solution therein.

In the embodiment shown in <figref idref="f0009">FIG. 9</figref>, the first insulating container 110a and the second insulating container 110b are provided in opposite directions relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container 110a, and the surface of each metal element exposed on the other main surface side of the chain 7 is plated while the fastener chain 7 passes through the second insulating container 110b.

In the embodiment shown in <figref idref="f0010">FIG. 10</figref>, the plating bath 201 is divided into a first plating bath 201a and a second plating bath 201b. The fastener chain 7 enters a plating solution 202a from an inlet 204 provided on a side wall of the first plating bath 201a, passes obliquely upward through three first insulating container(s) 110a arranged in series, and exits an outlet 205 provided on the side wall of the plating bath 201a. The outlet 205 is at a higher position than the inlet 204. The fastener chain 7 is then turned to enter the plating solution 202b from an inlet 206 provided on a side wall of the second plating bath 201b installed above the first plating bath 201a, passing obliquely upward through three second insulating container(s) 110b arranged in series, and exits an outlet 207 provided on the side wall of the second plating bath 201b.

In the embodiment shown in <figref idref="f0010">FIG. 10</figref>, the plating solution overflows from the inlet 204 and the outlet 205 of the first plating bath 201a. The overflowing plating solution is collected in a storage tank 203 through return pipes 210a, and then fed again to the first plating bath 201a by a circulation pump 208 through a feed pipe 212a. Also, the plating solution overflows from the inlet 206 and the outlet 207 of the second plating bath 201b. The overflowing plating solution is collected in the storage tank 203 through return pipes 210b, and then fed again to the second plating bath 201b by the circulation pump 208 through a feed pipe 212b.

In the embodiment shown in <figref idref="f0010">FIG. 10</figref>, the inside of the first plating bath 201a is provided with a return pipe 214 for adjusting the liquid level of the plating solution 202a, and the inside of the second plating bath 101b is provided with a return pipe 216 for adjusting the liquid level of the plating solution 202b, which prevent the plating solution from overflowing from each plating bath (201a, 201b).

In the embodiment shown in <figref idref="f0010">FIG. 10</figref>, the first insulating container(s) 110a and the second insulating container(s) 110b are provided in opposite orientation relative to the respective main surfaces of the fastener chain 7. The surface of each metal element exposed on one of the main surface sides of the fastener chain 7 is plated while the fastener chain 7 passes through the first insulating container(s) 110a, and the surface of each metal element exposed on the other main surface side of the fastener chain 7 is plated while the fastener chain 7 passes through the second insulating container(s) 110b.

In the embodiments shown in <figref idref="f0005 f0006 f0007 f0008 f0009 f0010">FIGS. 5 to 10</figref>, the amount of current flowing to the negative electrodes of each of the fixed cells (the first insulating container 110a and the second insulating container 110b) arranged in series while conveying the fastener chain 7 is changed (ON / OFF of current, magnitude of current), whereby the thickness of the plating film can be altered for each element 3. This can allow the plating appearance of a mottled pattern (having different film thickness) to be provided to the fastener chain 7.

In the embodiments shown in <figref idref="f0008 f0009 f0010">FIGS. 8 to 10</figref>, the plating bath in which the first insulating container(s) 110a and the second insulating container 110bs are accommodated is separated. Therefore, both can be immersed in the plating solution having the same composition. However, by arranging both in the plating baths containing plating solutions having different compositions, one main surface and the other main surface can also be plated with different colors.

(3-2 Rotary Barrel Type Plating Device)

An example that is now described is a rotary barrel type electroplating device. The rotary barrel type is advantageous in that double-sided plating is performed only by horizontally traveling the fastener chain. In the rotary barrel type plating device, the insulating container forms a rotary barrel having a rotation axis parallel to the traveling direction of the fastener chain. <figref idref="f0011">FIG. 11</figref> is a schematic view for explaining the principle of preferentially plating the upper surface of the fastener chain in the rotary barrel type electroplating device. <figref idref="f0012">FIG. 12</figref> is a schematic view for explaining the principle of preferentially plating the lower surface of the fastener chain in the rotary barrel type electroplating device. <figref idref="f0011">FIGS. 11</figref> and <figref idref="f0012">12</figref> depicts the rotary barrel as viewed from a direction facing the conveying direction of the fastener chain.

Referring to <figref idref="f0011">FIG. 11</figref>, a first rotary barrel 310a immersed in a plating solution 202 in a plating bath 201 flowably accommodates a plurality of conductive media 311, and the conductive media 311 are filled in a first rotary barrel 310a to a height that is more preferentially contacted with a surface of each element 3 exposed on a lower surface side of the fastener chain 7 than a surface of each element 3 exposed on an upper surface side of the fastener chain 7. A specific height adjustment can be appropriately performed in view of the diameters and the number of the conductive media 311, the height of the fastener chain 7, and the like. The wall surface of the first rotary barrel 310a is provided with opening(s) 318 each having such a size that the conductive media 311 cannot pass through, such that the plating solution can enter and exit the first rotary barrel 310a through the opening(s) 318. While the fastener chain 7 passes through the first rotary barrel 31 0a in a direction parallel to the rotation axis, at least a portion of the conductive media 311 can be brought into contact with a negative electrode 317 disposed in the first rotary barrel 310a while moving on an inner surface of the cross-sectional circular shape of the first rotary barrel 310a in association with rotational movement of the first rotary barrel 310a, and at least a portion of the conductive media 311 can be brought into contact with the surface of each element 3 exposed on the lower side of the fastener chain passing through the first rotary barrel 310a. When at least a portion of the conductive media 311 is electrically contacted with both of those conductive media 311 to create an electrical path, power can be supplied to the elements 3 while the fastener chain 7 passes through the first rotary barrel 310a.

In <figref idref="f0011">FIG. 11</figref>, a positive electrode 316 is installed at a position facing the surface of each element 3 exposed on the upper surface side of the fastener chain 7. Thus, cations in the plating solution can efficiently reach the upper surface side of the fastener chain 7, and can rapidly grow the plating film on the surface of each element 3 exposed on the upper surface side.

On the other hand, the conductive media 311 in the first rotary barrel 310a slide down or roll off the inner surface of the first rotary barrel 310a under the influence of gravity, so that it is difficult for them to contact the surface of each element 3 exposed on the upper surface side of the fastener chain 7.

Referring to <figref idref="f0012">FIG. 12</figref>, a second rotary barrel 310b immersed in a plating solution 202 in the plating bath 201a flowably accommodates a plurality of conductive media 311. The wall surface of the second rotary barrel 310b is provided with a plurality of opening(s) 318 having such a size that the conductive medium 311 cannot pass through, such that the plating solution can enter and exit the second rotary barrel 310b through the opening(s) 318. The second rotary barrel 310b has at least one guide 312 (nine guide plates extending in a direction parallel to the rotation axis at equal intervals in <figref idref="f0008">FIG. 8</figref>) protruding inward (toward the rotational axis in <figref idref="f0012">FIG. 12</figref>) from the inner surface having the cross sectional circular shape, such that a large number of conductive media 311 accommodated in the second rotary barrel 310b are preferentially contacted with the surface of each element 3 exposed on the upper surface side of the fastener chain 7 compared with the surface of the element 3 exposed on the lower surface side of the fastener chain 7.

While the fastener chain 7 passes through the second rotary barrel 310b, the conductive media 311 can move up to the middle of the inner surface of the second rotary barrel 310b while being supported by the guide member 312, as the second rotary barrel 310b rotates. As the rotational movement of the second rotary barrel 310b proceeds, the conductive media 311 which cannot be supported by the guide member 312 flows inward of the second rotary barrel 310b.

At least a portion of the conductive media 311 flowing inward can be contacted with a negative electrode 317 disposed in the second rotary barrel 310b, and at least a portion of the conductive media 311 can be contacted with the surface of each element 3 exposed on the upper surface side of the fastener chain 7 passing through the second rotary barrel 310b in a direction parallel to the rotation axis. When at least a portion of the conductive media is electrically contacted with both of those conductive media to create an electrical path, power can be supplied to each element 3 while the fastener chain 7 passes through the second rotary barrel 310b.

In <figref idref="f0012">FIG. 12</figref>, a positive electrode 316 is installed at a position facing the surface of each element 3 exposed on the lower surface side of the fastener chain 7. Thus, cations in the plating solution can efficiently reach the lower surface side of the fastener chain 7, and can rapidly grow the plating film on the surface side of each element 3 exposed on the lower surface side.

On the other hand, the conductive media 311 at the bottom in the second rotary barrel 310b are pushed by the guide 312 and carried away in association with the rotation of the second rotary barrel 310b, so that it is difficult for the conductive media 311 to stay at the bottom in the second rotary barrel 310b. Therefore, it is difficult for the conductive media 311 in the second rotary barrel 310b to contact the surface of each element 3 exposed on the lower surface side of the fastener chain 7.

<figref idref="f0013">FIG. 13</figref> shows an overall structural example of a rotary barrel type electroplating device. The fastener chain 7 enters a plating solution 402 from an inlet 406 provided on a side wall of a plating bath 401 while being conveyed in the direction of the arrow, and straightly passes from an inlet 314a to an outlet 315a of a first rotary barrel 310a in a horizontal direction. During passing through the first rotary barrel 310a, the surface of each element 3 exposed on the upper surface side of the fastener chain is mainly plated. Then, the fastener chain 7 straightly passes from an inlet 314b to an outlet 315b of a second rotary barrel 310b serially connected to the first rotary barrel 310a in the horizontal direction, and exits an outlet 407 provided on the side wall of the plating bath 401. During passing through the second rotary barrel 310b, the surface of each element 3 exposed on the lower surface side of the fastener chain 7 is mainly plated. An insulating partition plate 321 for electrical disconnection to prevent mutual influence is provided between the first insulating container 310a and the second insulating container 310b.

In the embodiment shown in <figref idref="f0013">FIG. 13</figref>, the plating solution overflows from the inlet 406 and the outlet 407 of the plating bath 401. The overflowing plating solution is collected in a storage tank 403 through a return pipe 410 and then fed again to the plating bath 401 through a feed pipe 412 by a circulation pump 408. A heater 409 may be installed in the storage tank 403 to heat the plating solution therein.

Although the embodiment shown in <figref idref="f0013">FIG. 13</figref> uses the first rotary barrel 310a for growing the plating film on the surface of each element 3 exposed on the upper surface side of the fastener chain 7 and the second rotary barrel 310b for growing the plating film on the surface of each element 3 exposed on the lower surface side of the fastener chain 7, it is possible to plate both sides of the fastener chain by using only one of them. For example, it is considered that after vertically inverting the fastener chain 7 which has passed through the first rotary barrel 310a, the fastener chain passes through another first rotary barrel 310a. It is also considered that after vertically inverting the fastener chain 7 which has passed through the second rotary barrel 310b, the fastener chain passes through another second rotary barrel 310b. The method of using only the first rotary barrel 310a while vertically inverting the fastener chain 7 is preferable because the first rotary barrel 310a is easier to increase plating uniformity than the second rotary barrel 310b.

EXAMPLES

Hereinafter, Examples of the present invention are illustrated, but they are provided for better understanding of the present invention and its advantages, and are not intended to limit the present invention.

(Comparative Example 1)

The electroplating device shown in <figref idref="f0014">FIG. 14</figref> was constructed, and electroplating was continuously performed on a fastener chain being conveyed. In the electroplating device, an insulating container 110 containing a large number of conductive media 111 is disposed in a plating bath 201 containing a plating solution 202. A negative electrode 118 is provided at a center of the inside of the insulating container 110, and the conductive media 111 are in electrical contact with the negative electrode. The insulating container 110 has positive electrodes 119 on front and rear inner sides with respect to the traveling direction of the fastener chain 7. In this example, while the fastener chain 7 passes through the plating solution 202, the conductive media randomly contact the elements exposed on both main surface sides of the fastener chain 7, thereby forming the plating film on the surfaces of the elements.

The plating conditions were as follows: <ul id="ul0010" list-style="dash" compact="compact"><li>Fastener chain specification: model 5 RG chain (a chain width: 5.75 mm; element material: red brass) from YKK Corporation:</li><li>Plating solution: 5 L; composition: a plating solution for Sn-Co alloy plating;</li><li>Conductive media: 2700 stainless steel balls; diameter 4.5 mm; and</li><li>Current density: 5 A /dm².</li></ul>

The current density was a value obtained by dividing a current value (A) of a rectifier by a sum (dm²) of the total surface area (both sides) of the elements in a glass container and surface areas of the stainless steel balls. The reason why the surface areas of the stainless steel balls are taken into consideration is that the plating also adheres to the stainless steel balls. <ul id="ul0011" list-style="dash" compact="compact"><li>Retention time in plating solution: 7.2 seconds;</li><li>Conveying speed: 2.5 m/min; and</li><li>Insulating container: glass beaker.</li></ul>

(Example 1: Fixed Cell Type Plating Device)

Insulating containers each having the structure shown in <figref idref="f0002 f0003 f0004">FIGS. 2 to 4</figref> was produced according to the following specifications: <ul id="ul0012" list-style="dash" compact="compact"><li>Conductive Media: 450 iron balls having a copper pyrophosphate plating film with a thickness of about 3 µm on their surfaces, and having a diameter of 4.5 mm; number of laminated layers = 6;</li><li>Insulating Container: made of an acrylic resin;</li><li>Inclination Angle: 9°;</li><li>Openings 116: 54% opening ratio; circular holes having a diameter of 2 mm, arranged in a staggered pattern;</li><li>Gaps C1, C2: 2 mm;</li><li>Width W₂: 10 mm.</li></ul>

The electroplating device shown in <figref idref="f0010">FIG. 10</figref> was constructed using the above insulating containers, and electroplating was continuously performed on the fastener chain being conveyed.

Plating test conditions were as follows: <ul id="ul0013" list-style="dash" compact="compact"><li>Fastener Chain Specification: model 5 RG chain (chain width: 5.75 mm, element material: red brass) from YKK Corporation;</li><li>Plating Solution: 120 L, composition: plating solution for black Sn-Co alloy plating;</li><li>Current Density: 8.7 A/dm²;</li></ul>

The plating thickness = deposition rate x current density x plating time, and the deposition rate is a constant for each plating solution. Therefore, the current density (A/dm²) was determined from the plating time (minute), the deposition rate (µm / ((A/dm²) x min)) and plating thickness (µm). Note that the plating thickness is an average value of actual values by cross-sectional observation of several positions, and the plating time is time required for each element to pass through three insulating containers (plating time per side). <ul id="ul0014" list-style="dash" compact="compact"><li>Plating Time: 14.4 seconds;</li><li>Conveying Speed: 2.5 m/min; and</li><li>The shortest distance between each element and the positive electrode: 3 cm.</li></ul>

(Example 2: Fixed Cell Type Plating Device)

Electroplating was continuously performed on the conveying fastener chain by the same method as that of Example 1, with the exception that the test conditions were changed as follows: <ul id="ul0015" list-style="dash" compact="compact"><li>Fastener Chain Specification: model 5 RG chain (chain width: 5.75 mm, element material: red brass) from YKK Corporation;</li><li>Plating Solution: 120 L, composition: plating solution for copper pyrophosphate plating;</li><li>Current Density: 13.5 A/dm²;</li></ul>

The plating thickness = deposition rate x current density x plating time, and the deposition rate is a constant for each plating solution. Therefore, the current density (A/dm²) was determined from the plating time (minute), the deposition rate (µm / ((A/dm²) x min)) and plating thickness (µm). Note that the plating thickness is an average value of actual values by cross-sectional observation of several positions, and the plating time is time required for each element to pass through three insulating containers (plating time per side). <ul id="ul0016" list-style="dash" compact="compact"><li>Plating Time: 30.0 seconds;</li><li>Conveying Speed: 1.2 m/min; and</li><li>The shortest distance between each element and the positive electrode: 3 cm.</li></ul>

(Example 3: Fixed Cell Type Plating Device)

Electroplating was continuously performed on the conveying fastener chain by the same method as that of Example 1, with the exception that the test conditions were changed as follows: <ul id="ul0017" list-style="dash" compact="compact"><li>Fastener Chain Specification: model 5 RG chain (chain width: 5.75 mm, element material: red brass) from YKK Corporation;</li><li>Plating Solution: 120 L, composition: plating solution for copper sulfate plating;</li><li>Current Density: 25.0 A/dm²;</li></ul>

The plating thickness = deposition rate x current density x plating time, and the deposition rate is a constant for each plating solution. Therefore, the current density (A/dm²) was determined from the plating time (minute), the deposition rate (µm / ((A/dm²) x min)) and plating thickness (µm). Note that the plating thickness is an average value of actual values by cross-sectional observation of several positions, and the plating time is time required for each element to pass through three insulating containers (plating time per side). <ul id="ul0018" list-style="dash" compact="compact"><li>Plating Time: 36.0 seconds;</li><li>Conveying Speed: 1.0 m/min; and</li><li>The shortest distance between each element and the positive electrode: 3 cm.</li></ul>

(Example 4: Fixed Cell Type Plating Device)

Electroplating was continuously performed on the conveying fastener chain by the same method as that of Example 1, with the exception that the test conditions were changed as follows: <ul id="ul0019" list-style="dash" compact="compact"><li>Fastener Chain Specification: model 5 RG chain (chain width: 5.75 mm, element material: red brass) from YKK Corporation;</li><li>Plating Solution: 120 L, composition: plating solution for non-cyan Cu-Sn alloy plating;</li><li>Current Density: 4.0 A/dm²;</li></ul>

The plating thickness = deposition rate x current density x plating time, and the deposition rate is a constant for each plating solution. Therefore, the current density (A/dm²) was determined from the plating time (minute), the deposition rate (µm / ((A/dm²) x min)) and plating thickness (µm). Note that the plating thickness is an average value of actual values by cross-sectional observation of several positions, and the plating time is time required for each element to pass through three insulating containers (plating time per side). <ul id="ul0020" list-style="dash" compact="compact"><li>Plating Time: 14.4 seconds;</li><li>Conveying Speed: 2.5 m/min; and</li><li>The shortest distance between each element and the positive electrode: 3 cm.</li></ul>

(Plating Uniformity)

For Comparative Example 1 and Examples 1 to 4, evaluation results obtained by visually observing the resulting plating film of each element of the fastener chain are shown below: Evaluation was performed according to the following procedure. Each element is subjected to investigation whether or not plating is attached to both of the front and back sides. The evaluation of whether or not plating is attached to each element is carried out based on whether or not the element surface is entirely changed to black (Example 1), copper color (Example 2), copper color (Example 3) or silver color (Example 4) by visual inspection. It is determined that the plating is attached to the element only when the plating is attached to both of the front and back surfaces of the element. The investigation is performed for 200 elements adjacent to each other, and a ratio (%) of the number of elements to which plating adheres on the front and back surfaces is calculated. The results are shown in Table 1. The results are shown as average values when the same plating tests were performed multiple times. <tables id="tabl0001" num="0001"><table frame="all"><title>[Table 1]</title><tgroup cols="2"><colspec colnum="1" colname="col1" colwidth="38mm" /><colspec colnum="2" colname="col2" colwidth="47mm" /><thead><row><entry valign="top" /><entry valign="top">Plating Uniformity Evaluation</entry></row></thead><tbody><row><entry>Comparative Example 1</entry><entry>90%</entry></row><row><entry>Example 1</entry><entry>99% or more</entry></row><row><entry>Example 2</entry><entry>99% or more</entry></row><row><entry>Example 3</entry><entry>99% or more</entry></row><row><entry>Example 4</entry><entry>99% or more</entry></row></tbody></tgroup></table></tables>

<Discussion>

The use of the plating devices according to Examples according to the present invention allowed formation of a plating film with high uniformity for each element. Further, the iron ball for power supply was distant from the positive electrode and surrounded by a resin container, so that almost no plating film adhered to the iron balls.

(Example 5: Relationship between Distance from Negative Electrode and Maximum Plating Distance)

An insulating container having the structure shown in <figref idref="f0002 f0003 f0004">FIGS. 2 to 4</figref> was produced according to the following specifications. The negative electrode was provided only on the front inner side in the passing direction of the fastener chain. <ul id="ul0021" list-style="dash" compact="compact"><li>Conductive Media: 450 iron balls having a copper pyrophosphate plating film with a thickness of about 3 µm on their surfaces, and having a diameter of 4.5 mm; number of laminated layers = 6;</li><li>Insulating Container: made of an acrylic resin;</li><li>Length of Insulating Container in Fastener Chain Conveying Direction: 20 cm;</li><li>Inclination Angle: 9°;</li><li>Openings 116: 54% opening ratio; circular holes having a diameter of 2 mm, arranged in a staggered pattern;</li><li>Gaps C1, C2: 2 mm;</li><li>Width W₂: 10 mm.</li></ul>

The plating conditions were as follows: <ul id="ul0022" list-style="dash" compact="compact"><li>Fastener chain specification: model 5 RG chain (a chain width: 5.75 mm; element material: red brass) from YKK Corporation:</li><li>Plating solution: 120 L; composition: a plating solution for nickel plating;</li><li>The conveying of the fastener chain was stopped, and a current of 2 A was applied to the negative electrode for 10 seconds while swinging the fastener chain in the insulating container in the right and left direction.</li></ul>

After the plating test, the distance to the element farthest from the negative electrode was measured, among the elements in which the adhesion of the plating was visually confirmed, indicating that it was 12 cm. Next, the distance to the elements farthest from the negative electrodes, among the elements in which the adhesion of plating was visually confirmed, was measured, under the same conditions with the exception that the current value and the plating time at the negative electrode were changed to the conditions as shown in Table 2. The results are shown in Table 2.

Further, based on D₀ = 2 A and I₀ = 12 cm, the maximum distance (D1) at which a plating film can be formed on the element when a current (I₁) at the negative electrode varied to 1.5 A, 1.0 A and 0.5 A was determined based on the following empirical formula. The results are shown in Table 2. It is understood that the experimental results well matched the maximum distance obtained from the experimental formula.<maths id="math0002" num="[Formula 2]"><math display="block"><msub><mi mathvariant="bold-italic">D</mi><mn>1</mn></msub><mo>=</mo><msub><mi mathvariant="bold-italic">D</mi><mn>0</mn></msub><mo>×</mo><msqrt><mfrac><msub><mi mathvariant="bold-italic">I</mi><mn>1</mn></msub><msub><mi mathvariant="bold-italic">I</mi><mn>0</mn></msub></mfrac></msqrt></math><img file="EP3556907A1_D0002.tif" /></maths><tables id="tabl0002" num="0002"><table frame="all"><title>[Table 2]</title><tgroup cols="4"><colspec colnum="1" colname="col1" colwidth="19mm" /><colspec colnum="2" colname="col2" colwidth="28mm" /><colspec colnum="3" colname="col3" colwidth="66mm" /><colspec colnum="4" colname="col4" colwidth="54mm" /><thead><row><entry valign="middle">Current (A)</entry><entry valign="middle">Plating Time (sec)</entry><entry valign="middle">Maximum Distance of Plated Element from Nevative Electrode (cm)</entry><entry valign="middle">Maximum Distance based on Empirical Formula (cm)</entry></row></thead><tbody><row><entry valign="middle">0.5</entry><entry valign="middle">40</entry><entry valign="middle">6</entry><entry valign="middle">6.00</entry></row><row><entry valign="middle">1.0</entry><entry valign="middle">20</entry><entry valign="middle">9</entry><entry valign="middle">8.48</entry></row><row><entry valign="middle">1.5</entry><entry valign="middle">13</entry><entry valign="middle">11</entry><entry valign="middle">10.39</entry></row><row><entry valign="middle">2.0</entry><entry valign="middle">10</entry><entry valign="middle">12</entry><entry valign="middle">-</entry></row></tbody></tgroup></table></tables>

(Example 6: Improvement of Plating Efficiency by Disposing Multiple Negative Electrodes)

The same insulating container as that of Example 5 was produced with the exception that the negative electrodes was disposed at three positions in total: the front inner side in the passing direction of the fastener chain (Point A); a position that was 7 cm (Point B) and a position that was 14 cm (Point C) from the inner surface on the front side in the passing direction of the fastener chain. Note that Point B and Point C were on the inner side parallel to the passing direction of the fastener chain.

The plating conditions were as follows: <ul id="ul0023" list-style="dash"><li>Fastener chain specification: model 5 RG chain (a chain width: 5.75 mm; element material: red brass) from YKK Corporation:</li><li>Plating solution: 120 L; composition: a plating solution for nickel plating;</li><li>The conveying of the fastener chain was stopped, and a current value of each negative electrode was set to the value shown in Table 3 and plating was carried out for the time shown in Table 3 while swinging the fastener chain in the insulating container in the right and left direction.</li></ul><tables id="tabl0003" num="0003"><table frame="all"><title>[Table 3]</title><tgroup cols="6"><colspec colnum="1" colname="col1" colwidth="16mm" /><colspec colnum="2" colname="col2" colwidth="30mm" /><colspec colnum="3" colname="col3" colwidth="30mm" /><colspec colnum="4" colname="col4" colwidth="30mm" /><colspec colnum="5" colname="col5" colwidth="19mm" /><colspec colnum="6" colname="col6" colwidth="42mm" /><thead><row><entry valign="middle">Total Current (A)</entry><entry valign="middle">Negative Electrode Current at Point A (A)</entry><entry valign="middle">Negative Electrode Current at Point B (A)</entry><entry valign="middle">Negative Electrode Current at Point C (A)</entry><entry valign="middle">Plating Time (sec)</entry><entry valign="middle">Maximum Distance of Plated Element from Nevative Electrode (cm)</entry></row></thead><tbody><row><entry valign="middle">0.5</entry><entry valign="middle">0.1</entry><entry valign="middle">0.2</entry><entry valign="middle">0.2</entry><entry valign="middle">40</entry><entry valign="middle">12</entry></row><row><entry valign="middle">1.0</entry><entry valign="middle">0.2</entry><entry valign="middle">0.4</entry><entry valign="middle">0.4</entry><entry valign="middle">20</entry><entry valign="middle">15</entry></row><row><entry valign="middle">1.5</entry><entry valign="middle">0.3</entry><entry valign="middle">0.6</entry><entry valign="middle">0.6</entry><entry valign="middle">13</entry><entry valign="middle">18</entry></row><row><entry valign="middle">2.0</entry><entry valign="middle">0.4</entry><entry valign="middle">0.8</entry><entry valign="middle">0.8</entry><entry valign="middle">10</entry><entry valign="middle">19</entry></row></tbody></tgroup></table></tables>

From comparison with Example 5, it is understood that the installation of a plurality of negative electrodes results in increased regions of the elements that can be plated while suppressing the current value to each negative electrode. It is also understood that even if the total current value is the same, the maximum current value at each negative electrode is half or less, so that plating can be performed with the total current value that is twice or more as compared with the case where one negative electrode is disposed. This indicates that plating is possible even if the traveling of the fastener chain is performed at a speed that is twice or more.

DESCRIPTION OF REFERENCE NUMERALS

<ul id="ul0024" list-style="none" compact="compact"><li>1 fastener tape</li><li>2 core potion</li><li>3 element</li><li>4 upper stopper</li><li>5 lower stopper</li><li>6 slider</li><li>7 fastener chain</li><li>110 insulating container</li><li>110a first insulating container</li><li>110b second insulating container</li><li>111 conductive medium</li><li>112 passage</li><li>112a passage surface opposite to one main surface side of fastener chain</li><li>112b passage surface opposite to other main surface of the fastener chain</li><li>113 accommodating portion</li><li>113a inner side on front side of conveying direction of accommodating portion</li><li>113b inner side parallel to conveying direction of accommodating portion</li><li>113c inner side surface on rear side of conveying direction of accommodating portion</li><li>114 inlet to passage</li><li>115 outlet from passage</li><li>116 opening</li><li>117 opening</li><li>118 negative electrode</li><li>119 positive electrode</li><li>120 guide groove</li><li>121 partition plate</li><li>201 plating bath</li><li>202 plating solution</li><li>203 storage tank</li><li>204, 206 plating bath inlet</li><li>205, 207 plating bath outlet</li><li>208 circulating pump</li><li>209 heater</li><li>210, 214, 216 return pipe</li><li>212 feed pipe</li><li>310a first rotary barrel (first insulating container)</li><li>310b second rotary barrel (second insulating container)</li><li>311 conductive Medium</li><li>312 guide member</li><li>313 rotation axis</li><li>314a inlet for first rotary barrel</li><li>315a outlet for first rotary barrel</li><li>314b inlet for second rotary barrel</li><li>315b outlet for second rotary barrel</li><li>316 positive electrode</li><li>317 negative electrode</li><li>318 opening</li><li>321 partition plate</li><li>401 plating bath</li><li>402 plating solution</li><li>403 storage tank</li><li>406 plating tank inlet</li><li>407 plating tank outlet</li><li>408 circulating pump</li><li>409 heater</li><li>410 return pipe</li><li>412 feed pipe</li></ul>