Transverse tab application method and apparatus

Background of the Invention

0001The present invention relates to processes and apparatus for applying tabs to traveling webs, and more specifically to a method and apparatus for applying tabs to a traveling web of material at a transfer position when the tabs are provided to the transfer position in a path that can be skew to the travel direction of the web of material. The invention has particular applicability to the manufacture of disposable diapers.

0002The history of cutting and applying tabs to disposable diaper webs is now entering its fourth decade. Over the course of that time, various types of automatic manufacturing equipment have been developed which produce the desired results with a variety of materials and configurations. This equipment generally included window-knife and slip-and-cut applicators, each having their own advantages and limitations

0003window-knife applicators generally comprise the following; one or more rotating heads, each made up of a knife edge and a vacuum plate; a more or less stationary knife, which is configured with a hole (window) ; and a tape transfer mechanism. Typically, the rotating heads are mechanically configured to eliminate head rotation relative to the stationary knife. Each head is passed, once per cycle, across the face of the stationary window knife, through which the infeeding tape is passed. The rotating knife shears the extended length of tape against the sharp inner edge of the hole (window), after which the severed segment is held by the vacuum plate. The rotating head, with the segment of tape held in place by the vacuum plate, continues through its rotation to a point, usually 90 degrees later, where it contacts the traveling web, which is pressed against the exposed adhesive of the tape segment. This contact, usually against some backing device, effects a transfer of the tape tab from the vacuum plate to the traveling web, which then carries the tape tab downstream.

0004Slip-and-cut applicators are typically comprised of the following: a cylindrical rotating vacuum anvil; a rotating knife roll; and a transfer device. In typical applications, a tape web is fed at a relatively low speed along the vacuum face of the rotating anvil, which is moving at a relatively higher surface speed and upon which the tape web is allowed to "slip." A knife-edge, mounted on the rotating knife roll, cuts a segment of tape from the tape web against the anvil face. This knife-edge is preferably moving at a surface velocity similar to that of the anvil's circumference. Once cut, the tape tab is held by vacuum drawn through holes on the anvil's face as it is carried at the anvil's speed downstream to the transfer point where the tape segment is transferred to the traveling web.

0005Continual improvements and competitive pressures have incrementally increased the operational speeds of disposable diaper converters. As speeds increased, the mechanical integrity and operational capabilities of the applicators had to be improved accordingly. As a further complication, the complexity of the tape tabs being attached has also increased. That is, for a given tape web design, cut tape tabs may need to be applied to a traveling web of material at a transfer position while the tape tabs are -provided to the transfer position in a path that is skew to the travel direction of the web of material. Consumer product manufacturers offer tapes which are die-cut to complex profiles and which may be constructed of materials incompatible with existing applicators. For instance, a proposed tape tab may be a die-profiled elastic textile, instead of a typical straight-cut stiff-paper and plastic type used in the past. Consequently, a manufacturer may find itself with a window-knife applicator, which cannot feed a tape web with too little axial stiffness. It could also find itself with a slip-and-cut applicator, which cannot successfully apply die-cut tape segments. Furthermore, existing applicators cannot successfully apply tapes whose boundaries are fully profiled, as may be desired to eliminate sharp corners, which might irritate a baby's delicate skin. This demonstrates a clear need for an improved applicator capable of applying new tape configurations and overcoming other shortcomings of some prior art applicators.

0006To overcome some shortcomings, Parish et al. (<patcit id="pcit0001" dnum="US6475325B"><text>U.S. Patent No. 6,475,325</text></patcit>), which has been assigned to the same assignee as the present application, discloses an applicator and method that allows tape tabs to be applied to a running web of material, even when the web of tape tab material is moving at a different speed than the web of material. A protuberance acting against the web of material brings the web into contact with the tape tabs and adheres the tape tabs to the web. While this invention adequately solved many of the problems of the prior art, it did not address the placement of tape tabs which are being fed in a direction that is skew to the traveling direction of the web of material.

0007<patcit id="pcit0002" dnum="US20060201619A"><text>US 2006/0201619</text></patcit> discloses a method and apparatus for applying tape tabs to a travelling web of material when the tape tabs are moving in path which is perpendicular to the path of the travelling web.

Summary of the Invention

0008The present invention provides a method according to claim 1 and an apparatus according to claim 10.

0009The present invention has the added capability over the prior art by providing a method and apparatus for applying tabs to a travelling web of material at a transfer position when the tabs are provided to the transfer position in a path that is skew to the travel direction of the web of material.

0010The invention provides the additional benefit of quiet operation compared to prior art equipment, which uses high speed cutting faces and suffers from the effects of the very high energy levels seen at the point of contact. Generally, these energies, and the sounds that they generate, increase in proportion to the square of the velocity. The present invention benefits from the relatively low speed of the cutting faces and exhibits extremely low noise levels. In fact, the underlying noise of the mechanical drive systems and the travelling web equipment contribute to make the cutting noise level nearly unnoticeable .

0011The present invention provides a simplified process wherein a rotary knife or die, with one or more cutting edges, turns against and in coordination with a corresponding vacuum anvil cylinder. An infeeding tape web is fed along the surface of the anvil, which is rotating at a surface velocity equal to or only somewhat greater than that of the tape web. As the tape web passes the nip created between the knife-edges and the anvil surface, segments of tape are parted to form tape tabs but not significantly displaced upon the anvil surface. The tape tabs continue downstream on the anvil surface, held securely by forces induced by a vacuum source directed to one or more holes provided for each segment in the anvil surface.

0012At a point downstream, a transfer position, along the surface of the anvil, the traveling web to which the segments are to be attached is brought into close proximity with the anvil and its tape tabs at a transfer location. At the transfer position, the traveling web is proceeding in a direction that is skew to the tangent of the rotational direction of the anvil.

0013The present invention may include a vacuum commutation system configured to remove or reduce the level of vacuum used to hold each tab to the anvil surface just before the point of transfer. The materials and finishes selected for the anvil and the bump transfer surfaces provide a situation in which the coefficient of friction between the bump transfer surfaces and the traveling web is relatively high, while the coefficient of friction between the tape tab and the anvil is relatively low. The highly aggressive nature of the bond between the adhesive side of the tape tab and the target surface of the traveling web ensures that there is virtually no slippage between the two. This ensures that the traveling web is driven through the point of transfer at its existing velocity, and that any tendency of the tape tab to adhere to the anvil surface will not influence the traveling web. While some slippage may be inevitable, the slip occurs preferably only between the tape tab and the anvil surface. Given the extremely low moment of inertia of a tape tab and the aggressive adhesion provided between it and the compatible surface of the traveling web, each successive tape tab is successfully transferred to the traveling web, accelerating quickly to the speed of the traveling web.

0014The present invention allows for placement of tape onto areas of the disposable garment when the tape tabs are presented to the web at skew angles. For instance, training pants for babies typically have a removable panel in the rear of the diaper. A soiled panel is removed from the pants and rolled up and secured with the fastening tapes. The present invention provides for a method to apply the transverse fastening tapes to a diaper. Likewise, the present invention provides a method to attach tapes to sides of garments that are manufactured according to a transverse process.

Brief Description of the Drawings

0015<ul id="ul0001" list-style="none" compact="compact"><li><figref idref="f0001">Figure 1A</figref> is a perspective view of a prior art tape application apparatus.</li><li><figref idref="f0001">Figure 1B</figref> is a top plan view of a tape to be applied by the prior art tape application apparatus of <figref idref="f0001">Figure 1A</figref>.</li><li><figref idref="f0002">Figure 1C</figref> is an overhead diagrammatic view of tape tabs cut from the tape of <figref idref="f0001">Figure 1B</figref> applied by the prior art apparatus of <figref idref="f0001">Figure 1A</figref>.</li><li><figref idref="f0002">Figure 2A</figref> is a perspective view of a comparative transverse tab applicator.</li><li><figref idref="f0003">Figure 2B</figref> is a top plan view of a web to be applied by the tab applicator of <figref idref="f0002">Figure 2A</figref>.</li><li><figref idref="f0003">Figure 2C</figref> is an overhead diagrammatic view of tabs cut from the web of <figref idref="f0003">Figure 2B</figref> applied by the prior applicator of <figref idref="f0002">Figure 2A</figref>.</li><li><figref idref="f0004">Figure 3A</figref> is a perspective view illustrating an embodiment of the present invention.</li><li><figref idref="f0004">Figure 3B</figref> is an overhead diagrammatic view of tabs cut from the web of <figref idref="f0003">Figure 2B</figref> applied by the embodiment of <figref idref="f0004">Figure 3A</figref>.</li><li><figref idref="f0005">Figure 4</figref> is a front elevational view of the embodiment of <figref idref="f0004">figure 3A</figref>.</li><li><figref idref="f0005">Figure 5A</figref> is a front elevational view of a second embodiment of the invention.</li><li><figref idref="f0006">Figure 5B</figref> is a top plan view of a web to be applied by the tab applicator of <figref idref="f0005">Figure 5A</figref>.</li><li><figref idref="f0006">Figure 5C</figref> is an overhead diagrammatic view of tabs cut from the web of <figref idref="f0006">Figure 5B</figref> applied by the embodiment of <figref idref="f0005">Figure 5A</figref>.</li><li><figref idref="f0007">Figure 6</figref> is an overhead diagrammatic view of a second tab application according to the present invention.</li></ul>

Description of the Preferred Embodiment

0016Although the disclosure hereof is detailed and exact to enable those skilled in the art to practice the invention, the physical embodiments herein disclosed merely exemplify the invention which may be embodied in other specific structures. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.

0017<figref idref="f0001">Figure 1A</figref> displays a perspective view of a prior art tape tab application apparatus 100, as disclosed in Parish et al. (<patcit id="pcit0003" dnum="US6475325B"><text>U.S. Patent No. 6,475,325</text></patcit>), which has been assigned to the same assignee as the present application. The apparatus 100 includes a first tab supply assembly 110 and a first tab applicator 120, and it may further include a second tab supply assembly 130, and a second tab applicator 140. The first tab supply assembly 110 comprises a supplied web 111, which may be adhesive-coated, provided -over a first roller 112 and through a nip created by at least one blade 113 disposed on a first rotary cutter 114 cooperating with a first anvil 115. The first anvil 115 includes a vacuum drawn through its circumferential surface to maintain tabs 111a in place from the time of cutting to a transfer location 14. At the transfer location 14 of this prior art apparatus 100, a tangent 30 of the anvil surface is parallel to the traveling direction 12 o-f the web 10. The first tab applicator 120 comprises a wheel 121 affixed to a rotatable shaft 122, the wheel 121 having a simple protuberance 123 formed thereon.

0018The web 111 is fed over the roller 112 onto the anvil 115. The web 111 is fed to the anvil 115 at a speed that approximately equals the speed at which the outer periphery of the anvil 115 is traveling. If desired, the anvil 115 may rotate at a slightly higher speed than the linear speed of the tape web 111. The at least one blade 113 of the rotary cutter 114 also travels at a peripheral speed substantially equal to that of anvil 115. After being cut, the tabs 111a are carried on the outer surface of the anvil 115. The tabs 111a are held in place by the vacuum provided from within the interior of the anvil 115. If the web 111 is coated with an adhesive, the adhesive-coated surface preferably faces outwardly while a preferably non-tacky surface engages the anvil 115.

0019The first tab applicator 120 engages the web 10 at a predetermined interval against a tab 111a located on the anvil 115 at the transfer position 14. The protrusion 123 serves to deflect a portion of the web 10 toward the anvil 115 in order to transfer the tab 111a onto the web 10.

0020The arrangement of the second tab supply assembly 130 and the second tab applicator 140 of this prior art apparatus 100 is similar to that of the first.

0021The second tab supply assembly 130 comprises a supplied adhesive-coated tape web 131 provided over a roller 132 and through a nip created by at least one blade 133 disposed on a second rotary cutter 134 cooperating with a second anvil 135. The second anvil 135 includes a vacuum drawn through its circumferential surface to maintain tabs 131a in place from the time of cutting to a transfer location 14. The second tab applicator 140 comprises a wheel 141 affixed to the rotatable shaft 122, the wheel 141 having a simple protuberance 143 formed thereon.

0022The adhesive-coated tape web 131 is fed over the roller 132 onto the anvil 135. The tape web 131 is fed to the anvil 135 at a speed that approximately equals the speed at which the outer periphery of the anvil 135 is traveling. If desired, the anvil 135 may rotate at a slightly higher speed than the linear speed of the tape web 131. Blades 133 of the rotary cutter 134 also travel at a peripheral speed substantially equal to that of anvil 135. After being cut, the tabs 131a are carried on the outer surface of anvil 135. The tabs 131a are held in place by the vacuum provided from within the interior of the anvil 135. The adhesive-coated surface of the tape web 131 is facing outwardly while a preferably non-tacky surface engages the anvil 135.

0023The second tab applicator 140 engages the web 10 at a predetermined interval against a tab 131a located on the anvil 135 at the transfer position. The protrusion 143 serves to deflect a portion of the web 10 toward the anvil 135 in order to transfer the tab 131a onto the web 10.

0024<figref idref="f0001">Figure 1B</figref> shows a top plan view of a tape web 101 to be cut into tape tabs 111a and applied to a traveling web 10. The tape web 101 has a tape web width 102 and the tape tabs 111a have a tape tab height 103. The web 101 is cut at various points 104 depending upon desired dimensions for the resulting tabs 111a. Each tab 111a has a first portion 105 and a second portion 106. The first portion 105 is preferably coated with an adhesive, while the second portion 106 may be provided with a hook-and-loop type, or other, fastening means.

0025<figref idref="f0002">Figure 1C</figref> shows an overhead view of a web of material 10 having tape tabs 111a applied to the web 10 by the prior art apparatus of <figref idref="f0001">Figure 1A</figref>. The design of the tape web 111 and desirable tape tabs 111a allow a discrete protuberance 123 of the prior art apparatus 100 to create a sufficient attachment site 41 to maintain the tape tab 111a in positive adhesive contact with the web 10.

0026While the previous apparatus 100 provides generally sufficient operation for the specified tab configuration, other tab configurations may not be accommodated by the setup. <figref idref="f0002">Figure 2A</figref> is a perspective view of a comparative transverse tape tab applicator disclosed in the application to which priority is claimed. Like the prior art embodiment of <figref idref="f0001">Figure 1A</figref>, this embodiment 200 includes tab supply assemblies 210,230 and the same tab applicators 120,140. It will be noted, however, that the tab supply assemblies 210,230 have been rotated ninety degrees so that a tangent 31 of the surface of either anvil 215,235 is not parallel to the traveling direction 12 of the web 10. Rather, at the transfer location 14, the tangent 31 of the anvil surfaces is substantially perpendicular skew to the traveling direction 12 of the web 10. As used herein, skew describes referenced structures or illustrative references that are perpendicular or oblique to one another, but are not coplanar.

0027<figref idref="f0003">Figure 2B</figref> shows a top plan view of a web 201 to be cut into tabs 211a and applied to a traveling web 10. The web 201 has a web width 202 and the tabs 211a have a tab height 203. The web 201 is cut at various points 204 depending upon desired dimensions for the resulting tabs 211a. Each tab 211a has a first portion 205 and a second portion 206. The first portion 205 is preferably coated with an adhesive, while the second portion 206 may be provided with a hook-and-loop type fastening means. It should be noted that due to the respective orientation of the first portion 205 and the second portion 206, and the desired orientation on the web 10, the tabs 211a must be presented for affixation at an angle that is not parallel to the traveling direction 12 of the web 10, without major modifications to the tab supply assemblies 210,230.

0028<figref idref="f0003">Figure 2C</figref> depicts tabs 211a, 231a placed on a web 10 by the embodiment 200 of a transverse tape tab applicator apparatus shown in <figref idref="f0002">Figure 2A</figref>. However, despite the use of the same tape tab applicators 120,140 as the prior art embodiment 100, the orientation of the tape tabs 211a prevents the discrete protuberance 123 of this embodiment 200 from creating a sufficient attachment site 42 to maintain the tape tab 211a in positive adhesive contact with the web 10. That is, the relative dimensions of the tape tab 211a and the protuberance 123 provide the insufficient attachment site 42.

0029In <figref idref="f0004">Figure 3A</figref> there is shown a perspective view of an embodiment 209 of the present invention. Much like the apparatus in <figref idref="f0002">Figure 2A</figref>, this embodiment 209 of the present invention provides a tab supply assembly 210. This embodiment 209, however, provides an improved tab applicator 220. Optionally, the embodiment 209 may include a second tab supply assembly 230 and second tab applicator 240. While the tab applicators 220,240 are shown to be the same, identity is not required by the present invention. Indeed, detailed description of only one tab applicator 220 is provided, but if two applicators are used, it is preferable that the second applicator 240 be similar to the first 220. The tab applicator 220 of this embodiment 209 provides improved adhesion between a tab 211a and a traveling web 10. The applicator 220 includes a first bump transfer surface 221, which in conjunction with a first counterweight 222, is rotatable about an axis 223 and a second bump transfer surface 225, which in conjunction with a second counterweight 226, is rotatable about a second axis 227. Each bump transfer surface applies pressure to the web 10 preferably substantially simultaneously to the other.

0030While such timing may be enabled in a variety of ways, the bump transfer surfaces 221,225 preferably travel in eccentric paths of revolution.

0031<figref idref="f0004">Figure 3B</figref> is an overhead view of a web 10 having tabs 211a placed by the embodiment 209 of the apparatus and method of the present invention. As can be seen, the use of a modified tab applicator 220 provides a plurality of attachment sites 43 spaced at predetermined locations along the tab 211a, thereby improving adhesion between the tab 211a and the web 10.

0032<figref idref="f0005">Figure 4</figref> shows a front elevation view of the apparatus of <figref idref="f0004">Figure 3A</figref>. The incoming web 211 is fed about a roller 212. The web 211 travels further to contact the anvil 215. The web 211 is fed to the anvil 215 at a speed that approximately equals the speed at which the outer periphery of the anvil 215 is traveling. If desired, the anvil 215 may rotate at a slightly higher speed than the linear speed of the web 211. The blades 213 of the rotary cutter 214 are also traveling at a peripheral speed substantially equal to that of the anvil 215. After being cut, the tabs 211a are carried on the outer surface of the anvil 211a. The tabs 211a are held in place by vacuum provided within the interior of the anvil 215. If the web 211 is provided with an adhesive, the adhesive-coated surface preferably faces away from the anvil 215 while a non-tacky or uncoated surface preferably engages the exterior of the anvil 215.

0033The web 10 of diaper material is caused to travel in a path slightly displaced from the outer surface of the rotating anvil 215, but in close proximity thereto. Just below the web 10 is the tab applicator 220, whose bump transfer surfaces 221,225 rotate about their respective axes 223,227 at a peripheral velocity approximately equal to the lineal velocity of web 10, which, in turn, is usually substantially greater than the peripheral velocity of the anvil 215. Generally, once a tab 211a is at the transfer location 14, and the web 10 is in a desired position, the bump transfer surfaces 221,225 depress the web 10, causing the web 10 to come into contact with the anvil 215, thereby adhering the tab 211a to the web 10.

0034A second embodiment 309 of the present invention is shown in <figref idref="f0005">Figure 5A</figref>. While the first embodiment 209 is shown having a single bump transfer surface 221,225 on each transferor, each transferor may comprise a plurality of bump transfer surfaces 325, as shown in <figref idref="f0005">Figure 5A</figref>. Likewise, the invention may be used with only one structure incorporating all transfer surfaces, instead of multiple structures. If two tab supply assemblies are used, the anvils 215 and 235 may rotate in the same direction, as shown, or it is possible to arrange them so that they are rotating in dissimilar directions if preferred, thereby allowing different orientations of the tabs.

0035<figref idref="f0006">Figure 5B</figref> shows a top plan view of a web 301 to be cut into tabs 311a and applied to a traveling web 10. The web 301 has a web width 302 and the tabs 311a have a tab height 303. The web 301 is cut at various points 304 depending upon desired dimensions for the resulting tabs 311a.

0036<figref idref="f0006">Figure 5C</figref> shows an overhead view of a web of material 10 having tabs 311a applied to the web 10 by the embodiment 309 of <figref idref="f0005">Figure 5A</figref>. As can be seen, the use of a modified tab applicator 320 provides a plurality of attachment sites 44 spaced at predetermined locations about the tab 311a, thereby improving adhesion between the tab 311a and the web 10.

0037As shown in <figref idref="f0004">Figure 3A</figref>, <figref idref="f0005">Figure 4, and Figure 5A</figref>, the axes of rotation of the tab applicators 220,240 may be generally perpendicular skew from the axes of rotation of the anvils; however, the invention also contemplates tabs placed onto a web at a predetermined oblique skew angle. <figref idref="f0007">Figure 6</figref> represents a diagrammatic view of such an arrangement. The tabs 12 are provided to the transfer location 14 in an oblique skew manner and placed onto the web of material 10 at a desired angle, such as approximately a 45 degree angle. Therefore, the relative angle between the anvil surface tangent and the web 10 may lie at any skew angle, perpendicular or oblique.

0038The foregoing is considered as illustrative only of the principles of the invention.