Ferromagnetic fiber having uses in monitoring electrical appliances and manufacture thereof

(54)

PATENT INVENTOR INVENTOR'S OFFICE NAME (56) (57)

Pitney

John O.

H Albihns patent agency AB

Ferromagnetic Fibers for Product Monitoring and Methods for Producing These CALLED PUBLICATIONS: - - SUMMARY:

Bowes Inc_z Stamford Strom-Olsen, Quebec

CT US CA, Piotr Z

Rudkowski, Quebec CA use in electronic

A ferromagnetic fiber made for special use in the field of Electronic Art Surveillance (EAS), wherein the ferromagnetic fiber is manufactured using a rotary disk device which engages a molten alloy bath with the desired fiber compositions. The use of ferromagnetic fibers has resulted in the ability to produce EAS marking elements of such length that they can be applied using a commercial label application device.

<img file="SE504685C2_D0001.tif" />

The numbers in brackets indicate international identification code, INID code. Letters in clips indicate International Document Code.

504 685

Unauthorized use of goods has long been a major problem in the retail sector. Various attempts have been made to prevent such unauthorized measures, commonly referred to as mockery **. An electronic product monitoring system of the electromagnetic type has been described in French patent application FR763 681, published in 1934, by Picard. This system included a transmitter, a receiver and a ferromagnetic marker. Attempts have been made to reduce the size and cost of markings for product surveillance purposes, as described in US-4,568,921 (Pokalsky, February 4, 1986). In accordance with the latter patent, the filamentous marking element is about 0.127 mm (127 µm) in diameter and, more importantly, the marking element itself has a length of about 76.2 mm. United States Reissue Patent Re.-32,427 (Gregor, May 26, 1987) relates to a marker element, which consists of an elongated, flexible strip of amorphous ferromagnetic material, which retains its signal identity after bending or folding.

One method has been developed for the production of ferromagnetic fibers for use in marker elements. By marking element is meant an object which can be detected by a sensing system after the marking element has been placed in a magnetic field with suitable properties. The present invention comprises a ferromagnetic fiber, or fibers, together with any suitable form of carrier. The fibers can be detected in an examination zone, where the fibers have a length of less than 15 mm (5/8 inch). It has been found that one of the important parameters of the ferromagnetic fibers is the aspect ratio. Fibers having a diameter of about 100 μια or less have been found suitable for making a marking element, for example a label, of a length of about 15 mm or less. It will be appreciated that the length may be longer, if desired.

504 685 ²

Another important parameter is the method by which the ferromagnetic fiber is produced. Rapid solidification methods are used, where the fibers are cast directly into their final physical dimension and no subsequent mechanical or thermal treatment is required for carrying out the invention. Fibers produced by rapid solidification method are in a stress state and molecular orientation which is favorable with respect to its magnetic properties in molded form.

It is an object of the present invention to provide an improved marking element for an electronic merchandise monitoring system with a ferromagnetic marking element, which is significantly shorter than marking elements of the prior art and which is inexpensive and yet provides efficient electromagnetic. response in the system.

Another object of the invention is to provide an improved electromagnetic marking element for use in an electronic merchandise surveillance system, wherein the marking element is either a crystalline or amorphous fiber made by fast setting technology.

A further object of the invention is to provide an improved production of an electromagnetic marking element for use in an electronic merchandise surveillance system, wherein the marking element is produced by fast counting technology.

Still another object of the invention is to provide an improved marker element for use in an electronic monitoring system, wherein one or more ferromagnetic marker elements are mounted in a random orientation on a suitable carrier, for example, a registration element such as a label, price tag or other marking.

Yet another object of the invention is to provide an improved marking element for use in an electronic merchandise monitoring system in which crystalline ferromagnetic material, e.g., a permalloy, is used, and wherein

504 The 685 tag element is flexible enough to be manipulated without loss of its signal identity. Further, an object of the invention is to provide an improved marking element for an electronic merchandise monitoring system, wherein a marking element comprises a fiber woven into the fabric.

Another object of the invention is to provide an improved marker element for use in an electronic merchandise monitoring system, where a marker element is directly inserted into paper.

It is a further object of the invention to provide an improved method of producing a marker element for use in an electronic monitoring system, wherein one or more marker elements are inserted into a papermaking slurry, which is then rolled into paper, whereby the resulting paper can be detected through the system.

Another object of the invention is to provide an improved marker element for use in electronic monitoring systems, wherein the marker element comprises a marker element of a shape and voltage which provides favorable ferromagnetic properties.

Further, an object of the invention is to provide an improved marking element for use in an electronic merchandise monitoring system, wherein the marking element comprises a marking element with a ferromagnetic fiber not having a length exceeding 15 mm.

It is a further object of the invention to provide a marking element having at least one sheet carrying one or more ferromagnetic fibers.

Further, an object of the invention is to provide an improved inexpensive, ferromagnetic marker element.

504 685

Another object of the invention is to produce a ferromagnetic marking element in an even drawing method which results in a product ready for use.

It is a further object of the invention to provide a ferromagnetic material useful in shielding magnetic fields.

It is a further object of the invention to provide an improved marker element for use in an electronic merchandise monitoring system, wherein the marker element comprises a ferromagnetic marker element having a cross-sectional area less than 6 x 10³ mm².

It is a further object of the invention to provide an improved marking element for use in an electronic merchandise monitoring system, wherein the marking element comprises a ferromagnetic fiber having a maximum transverse dimension of less than 80 µα.

Another object of the invention is to provide an improved marker element for use in an electronic merchandise monitoring system, wherein the marker element comprises a ferromagnetic fiber having a weight of less than 20 mg. It is a further object of the invention to provide a ferromagnetic marker element which can be used in modern commercial devices for affixing labels.

Fig. 1 is a longitudinal cross-sectional view of a melt extraction device for producing ferromagnetic fibers;

Fig. 2 is an enlarged cross-section along the line 2-2 in Fig. 1 of the spinning disk periphery shown in Fig. 1;

Fig. 3 is a cross-sectional view taken along line 3-3 of Fig. 1 showing the cross-section of a fiber produced by the device of Fig. I;

Fig. 4 is a plan view of a composite web comprising fibers made by the device of Fig. 1;

685

504

Fig. 5 is a cross-sectional view taken along lines 5-5 of Fig. 4 showing a side view of the composite web; and

Fig. 6 is a plan view showing an alternative distribution of the fibers within a label.

With reference to Figs. 1-3, a rotating disc device is shown capable of providing rapid solidification generally at 10, which provides ferromagnetic fibers in accordance with the principles of the present invention. What is shown and described herein is a melt extraction technique, but it will be appreciated that other methods can be used in the practice of the invention, including melt spinning, melt drawing and the pendulum drop method. The important requirement is that the material has a shape such as those described and solidifies rapidly. The device 10 comprises a disc, 12, or wheel, which is stationary fixed by a rotatable shaft 13 and has a reduced section 14 at its periphery. The reduced section 14 has an edge 16. The disc 12 used in the practice of the invention had a diameter of 15 cm (6 inches) and the edge 16 has a radius of curvature of about 30 μη, with 5-50 µm being acceptable. The shaft 13 engages an engine 17 through any conventional device so that the shaft, and the disc 12 mounted thereon, can be caused to rotate.

A bowl-shaped cast water 18 is placed under the disc 12 and is intended to accommodate a metal alloy composition 20. Induction coils 22 are located around the vane 18 and are connected to a power source 23. When sufficient energy is supplied to the coils 22, metal alloy compositions 20 melt within the water 18. rotating, as shown by the arrow in Fig. 1, and on the disk rotating within the molten alloy composition, a fiber 24 is formed. Optionally, in contact with the flange 14, a wiper 26 is provided, made of a material, such as fabric, for the purpose of keeping the reduced section 14 clean.

With reference to Figures 4 and 5, the fibers 24 are oriented relative to each other and located between upper and lower sheets 30, 32, which are joined together by an adhesive 34 for forming

504 685 6 of a marking element, which is shown in the form of a label 28. The labels 28 are supported by a web 36 and can be applied to the surface of an article by using a labeling device well known in the art. As used herein, the term label also includes price tags and the like. For details of a carrier web as described herein, reference may be made to US-A-4,207,131. Preferably, the marking element 28 has a length of less than 25 mm (1 inch) and preferably about 15 mm (5/8 inch). With such a size, composite web 38 can be used in a commercial labeling device, such as an 1110 labeler, available from Monarch Marking Systems Inc., Dayton, Ohio. Although the marking element 28 is shown with top and bottom sheets, 30, 32, it will be appreciated that the fibers 24 can be made to adhere only, the bottom sheet 32 ​​and the top sheet can be eliminated.

The power source 23 is arranged so as to cause the induction coils to heat the metal alloy 20 to a temperature above its melting point, thereby forming a molten bath of metal alloy. It should be noted that the reduced section 14 of the disk 12 extends into the metal 20. Although the metal is shown to have a dome appearance, this is somewhat exaggerated to show that the reduced section 14 dips into the melt. In any event, a portion of the diameter of the disc 12 extends below the top portion of the water to engage the metal alloy 20 after the metal alloy has reached its appropriate temperature. Depending on the temperature of the alloy, the arm 19 is lowered so that the reduced section 14 is placed in the metal alloy and the motor 17 is started to cause the disc 12 to rotate. The disc 12 rotates in it through the arrow in FIG. 1 shown a direction and a fiber of ferromagnetic material 24 is thereby formed. This fiber 24 can be made as long as desired.

It will be appreciated that the quick-setting process described provides a fiber that is in a state ready for use, i.e., it goes directly from molten state to solid state ready for immediate use. Some subsequent treatment

504 685 ling is not required to achieve the desired properties. This is in contrast to prior art ferromagnetic materials, such as wires and permalloy foils, where mechanical and / or thermal treatment is required to obtain the necessary properties.

In accordance with this invention, a ferromagnetic fiber is defined as a generally elongated article composed of either amorphous or crystalline ferromagnetic material, having a diameter of 3-80 μηι, a side ratio, i.e. length to diameter ratio, of at least 150, and a magnetic switching time at half-amplitude points (t₀₅) of less than 10 microseconds at a sine wave driving frequency of 6 kH and an amplitude on the order of one Oersted. The fiber formed by the aforementioned device has a cross-section, as shown in Fig. 3, ie 8 in general kidney format. A special fiber was kidney shaped and had a dimension of 30-80 / an in one direction, and 20-30 gm in the other direction. When the velocity was the disk 12 increased, the fiber 24 assumed a more oval shape, as opposed to the kidney shape, and would eventually have a circular cross-section with a narrow groove if the diameter of the fibers was 15 µm or less. Best results are obtained with a fiber 24 having a generally circular cross-section.

Under optimal conditions, the fiber 24 would be of indefinite length, but it has been found that certain conditions affect the length of the fiber. The conditions which cause variation in the length of the fiber are the speed of rotation of the disc 12, vibration of the system and the shape and design of the disc.

The fiber 24 was cut to lengths of about 19 mm (3/4 inch) and placed on a first layer 32 of a label. A second layer 30 was placed over the fiber 24, in alignment with the first layer, and with glue disposed therebetween to form a label. The fibers 24 may be placed in an oriented relation, as shown in Fig. 4, at a distance of about 1 mm, or they may be placed in the label in a random manner, as shown in Fig. 6. It has been found that three or more multiple fibers,

504 685 8 positioned in orientation would be sufficient for the selection element to be detected at an examination zone, while when the fibers were randomly placed, five or more fibers were sufficient. Placement of the fibers 24 in a random manner with overlapping each other is unique in the art. Earlier marking elements required that several elements be oriented with and / or sequentially. Other orientations are possible. One or more fibers in helical, curved, or curved form can also give acceptable response detection. It was found that the minimum total weight of fiber 24, which can be detected, was about 0.2 mg.

A large number of compositions were prepared for the purpose of producing fibers 24. The following is a table of some of the compositions examined with the physical form and test results obtained from the system.

504 685 ^hrs0,5 ^(1s)

COMPOSITION

FORM

<img file="SE504685C2_D0002.tif" />

<img file="SE504685C2_D0003.tif" />

<td>^Fairy69^A126^Cr5</td><td>C</td><td> 3</td><td>and 5</td>

<td>^Fairy72^A125^Cr3</td><td>C</td><td> 7</td><td>and 8</td>

<td>^Fairy72A128</td><td>C</td><td></td><td> 6</td>

<td>^Fairy72^A125^Cr3</td><td>C</td><td></td><td> 7</td>

<td>^Fairy70^A125^cf5</td><td>c</td><td></td><td> 5</td>

<td>^You72^CU14^MO3^FairyII</td><td>c</td><td></td><td> 2</td>

<td>^You72^CU14^Cr3^FairyII</td><td>c</td><td></td><td> 3</td>

<td>^You72^CU13^MO2^Mn2^FairyII</td><td>c</td><td></td><td> 4</td>

<td>^You71^Cu13^M°2^Mn3^Fairyil</td><td>c</td><td></td><td> 2.4</td>

<td>^You73^CU13^M°2^Mnl^FairyII</td><td>c</td><td></td><td> 1.8</td>

<td>^N ±7 9^15^5^1</td><td>c</td><td></td><td> 1.5</td>

<td>You₈2^Fairyi2^Cul^Mo3^Mn2</td><td>c</td><td></td><td> 2.5</td>

<td>^CO70^Fairy4^Si16^B10</td><td>A</td><td></td><td> 2.4</td>

<td>^CO69.6^F®4.1^M° O.9^Si17.5®7.75</td><td>A</td><td></td><td> 2.8</td>

<td>^Fairy78^Si9^B13</td><td>A</td><td></td><td> 5.2</td>

<td>^Fairy74^Nb8^Si6^B12</td><td>A</td><td></td><td> 2.7</td>

504 685 wherein C = crystalline A = amorphous t_0/5 - heart rate measurement in microseconds

In determining the properties of a ferromagnetic marker element, perhaps the most critical parameter t₀₅, which is the measure of how sharp the pulse induced by the marking element is in a survey zone. More specifically, t represents_{0 5} in microseconds the time elapsed between the increasing and decreasing portions at half of the peak value of the induced signal. Ebb value of t_{0 5} = 10 microseconds or less is considered acceptable. A lower is desirable as this indicates a sharp, easily detected peak and thus high harmonic content.

Although attempts have been made in the past to use crystalline ferromagnetic materials, commonly referred to as permalloy, as an element in a marker element, two factors have prevented its use.

First, in earlier forms of permalloy element t_0/5far too large for practical use in the EAS area. Second, because permalloy is crystalline, bending tends to alter its magnetic properties. In the present invention, it has been found that these adverse properties are sufficiently reduced to permit the use of permalloy. As stated previously, low amounts of ferromagnetic material in fibrous form can be detected in a test zone.

In addition, it can be mentioned that all ferromagnetic materials which are useful as an EAS marking element in the form of a band are useful when in the form of a fiber. Reference is made to US-A-32 427 for examples of such compositions.

Generally, the fiber can be made from a ferromagnetic material consisting essentially of any of the formulas:

504 685

Fa Lb Oc, wherein

F is iron,

L is at least one of silicon or aluminum,

O is at least one of chromium, molybdenum, vanadium, copper, manganese and

<td>a varies</td><td colspan="3">in the range of about 60-90 atomic%</td>

<td>b </td><td>TL</td><td>WN</td><td> 10-50 </td>

<td>c </td><td>hrs</td><td>Η H</td><td> 0-10 </td>

or

After Fb Mc, vari

N is nickel,

F is iron,

M is at least one of copper, molybdenum, vanadium, chromium, manganese, or other non-magnetic elements, and

<td colspan="4">a varies in the range of about 60-84 atomic%</td>

<td>b</td><td>M</td><td>WMW</td><td> 0-40 </td>

<td>c</td><td>N</td><td>N Η H</td><td> 0-50 </td>

or

Ma Nb Xd Yc, vari

M is at least one of iron or cobalt, N is nickel,

O is at least one of chromium and molybdenum, X is at least one of boron and phosphorus,

Y is silicon,

Z is carbon, and

<td>A</td><td>varies</td><td colspan="5">in the range of about 35-85 atomic%</td>

<td>b</td><td>it</td><td>N</td><td>it</td><td>II</td><td> 0-45</td><td>N</td>

<td>c</td><td>M</td><td>hrs</td><td>tt</td><td>tt</td><td> 0-7</td><td>N</td>

<td>d</td><td>M</td><td>M</td><td>M</td><td>M</td><td> 5-22</td><td>it</td>

<td>e</td><td>it</td><td>W</td><td>tt</td><td>M</td><td> 0-15</td><td>hrs</td>

<td>f</td><td>tt</td><td>W</td><td>tf</td><td>it</td><td> 0-2</td><td>tt</td>

504 685 12 and the sum of d + e + f varies in the range of about 15-25 atomic%.

It should be noted that in general, these fibers are amorphous and can be made in an ambient environment, while fibers made from crystalline compositions must be formed in a vacuum or inert atmosphere, for example argon.

It has been found that all devices which emphasize the rapid change in magnetic flux resulting from change in the magnetization of a soft magnetic material are improved by using the material in the form of fibers. Although the reasons why an electromagnetic fiber produced by flash cooling results in superior properties within the EAS range are not fully known, calculations have been made showing that a cylindrical shaped electromagnetic material is superior to the same material in the form of a tape.

Comparison of signals from a band and a fiber

B »0.6 Tasla

S

- 1 100,000 mo

-1 W = 2 p 6000 sec

Saturation flavoring of the material

Magnetic permeability of the material

Frequency of applied field

H »1.5 overstate m _G .. ---- (9.3 m

Applied field

Dimensions of a fiber (F) length (ln) = 20 mm diameter (d) = 25 gm

N - 10 Qty = 1 Qty

Coupling factor to take-up coil and band (S) width (w) - 0.8 mm thickness (t) = 25 gm of rotation on take-up coil fibers

504 685

Effective magnetic permeability for a fiber 1 DF compared to a band 1 DS taking into account the demagnetizing effect.

(ln, d) «3.2— DF dp 1 (ln, w, t) -------------- DS 14.25 tw

<img file="SE504685C2_D0004.tif" />

(ln, d) - 67.31 x 10 1

DS (ln, W, t) - 3.279 x 10

It can be seen that the effective magnetic permeability of a ferromagnetic fiber is considerably greater than that of a tape.

Volume of magnetic material.

V (l, d) F d

»P - 1 V (ln, w, t,) - wt 1 4 S

Relationship between applied field and critical field for fiber (BF) and band (BS):

BF (ln, d) «

BS (ln, w, t):

<img file="SE504685C2_D0005.tif" />

<img file="SE504685C2_D0006.tif" />

<img file="SE504685C2_D0007.tif" />

<img file="SE504685C2_D0008.tif" />

<img file="SE504685C2_D0009.tif" />

<img file="SE504685C2_D0010.tif" />

1 (N, d)

DF

<img file="SE504685C2_D0011.tif" />

m + '

1 (N, w, t)

DS

Decrease or roll off for signal from one harmonic to the next:

AF (ln, d) l + = BF (ln, d) - ln '- - AS (ln, w, t) ²\ ln + BS (ln, w, t) -1

BF (n, d)

BS (n, w, t)

AF (ln, d) = 0.821

AS (ln, w, T) - 0.191

504 685

Signal at the 9th harmonic for a fiber (SF) and a band (SS).

9

SF (ln, d) = - B w V (ln, d) AF (ln, d) n_ NG p SS ^f

SS (ln, w, t) - 4 B_s w V_f (ln, W, t). AS (ln, w, t)⁹ N_f NG

SF (ln, d) - 3,674 x 10 volts

SS (ln, w, t) = 2,783 x 10 volts

SF (n, d)

--------- » 132.017

SS (n, w, t)

Relationship for signals

V (ln, d)

F

---------- «0.025 Ratio for material volumes

V (In, v, t).

S

As shown in the above calculations, the signal generated by a fiber is 132 times larger than a signal produced by a band of the same length, 20 mm. It will be appreciated that the other dimensions of the tape can be altered so that the response capacity of the tape changes, but the ratio of the selected dimensions were those considered typical.

Although the novel fiber of this invention has been discussed here in connection with the use of labels, it will be appreciated that there are other uses for such fibers as well. If made small enough, the fibers can be woven as part of paper from which the document is produced. In this way, one can produce an article with invisible detection properties. A further use for which these fibers could be applied is the placement and identification of such structures as cables, located underground, or other unavailable structures. The wires could be included as part of the cable, which is laid underground, and by suitable detection devices, the cables can be located even if not exposed. Another use could be shielding, for example when shielding electrical cables from a magnetic field, a cover over the cables, including ferromagnetic fibers, would tend to isolate the cables from the field. Yet another use is to add the electromagnetic fibers to a pulp from which paper including fibers can be made. Such papers could be detected and have great use where security is required, for example, in the making of banknotes.

504 685