Abstract:
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 is skew to the web travel path. A tab supply assembly carries the tabs in a tab path that is either perpendicularly skew or obliquely skew to the travel path of the web. The web is generally spaced from the tab supply assembly. A plurality of bump transfer surfaces is adapted to urge the web towards the tab supply assembly, thereby contacting a tab.

Description:
RELATED APPLICATION 
     This application is a continuation-in-part application of U.S. patent application Ser. No. 11/371,468, now U.S. Pat. No. 7,452,436, filed 9 Mar. 2006, and entitled “Transverse Tape Application Method and Apparatus,” which claims the benefit of U.S. Provisional Patent Application Ser. No. 60/659,785, filed 9 Mar. 2005, and entitled “Transverse Tape Application Method and Apparatus.” 
    
    
     BACKGROUND OF THE INVENTION 
     The 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. 
     The 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. 
     Window-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. 
     Slip-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&#39;s circumference. Once cut, the tape tab is held by vacuum drawn through holes on the anvil&#39;s face as it is carried at the anvil&#39;s speed downstream to the transfer point where the tape segment is transferred to the traveling web. 
     Continual 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&#39;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. 
     To overcome some shortcomings, Parish et al. (U.S. Pat. No. 6,475,325), 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. 
     SUMMARY OF THE INVENTION 
     The present invention has the added capability over the prior art by providing 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 is skew to the travel direction of the web of material. 
     The 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 traveling web equipment contribute to make the cutting noise level nearly unnoticeable. 
     The 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. 
     At 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. A device, which may be as simple as a protuberance or multiple protuberances on a rotating cylinder, presses a target zone of the traveling web against an exposed adhesive of the tape tab as it is presented by the anvil surface. The protuberance preferably has a surface velocity substantially identical to that of the traveling web. 
     The 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. 
     The 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 
         FIG. 1A  is a perspective view of a prior art tape application apparatus. 
         FIG. 1B  is a top plan view of a tape to be applied by the prior art tape application apparatus of  FIG. 1A . 
         FIG. 1C  is an overhead diagrammatic view of tape tabs cut from the tape of  FIG. 1B  applied by the prior art apparatus of  FIG. 1A . 
         FIG. 2A  is a perspective view of a transverse tab applicator disclosed in the priority application. 
         FIG. 2B  is a top plan view of a web to be applied by the tab applicator of  FIG. 2A . 
         FIG. 2C  is an overhead diagrammatic view of tabs cut from the web of  FIG. 2B  applied by the prior applicator of  FIG. 2A . 
         FIG. 3A  is a perspective view illustrating an embodiment of the present invention. 
         FIG. 3B  is an overhead diagrammatic view of tabs cut from the web of  FIG. 2B  applied by the embodiment of  FIG. 3A . 
         FIG. 4  is a front elevational view of the embodiment of  FIG. 3A . 
         FIG. 5A  is a front elevational view of a second embodiment of the invention. 
         FIG. 5B  is a top plan view of a web to be applied by the tab applicator of  FIG. 5A . 
         FIG. 5C  is an overhead diagrammatic view of tabs cut from the web of  FIG. 5B  applied by the embodiment of  FIG. 5A . 
         FIG. 6  is an overhead diagrammatic view of a second tab application according to the present invention. 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
     Although 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. 
       FIG. 1A  displays a perspective view of a prior art tape tab application apparatus  100 , as disclosed in Parish et al. (U.S. Pat. No. 6,475,325), 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  111   a  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  of 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. 
     The 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  111   a  are carried on the outer surface of the anvil  115 . The tabs  111   a  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 . 
     The first tab applicator  120  engages the web  10  at a predetermined interval against a tab  111   a  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  111   a  onto the web  10 . 
     The 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. The 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  131   a  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. 
     The 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  131   a  are carried on the outer surface of anvil  135 . The tabs  131   a  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 . 
     The second tab applicator  140  engages the web  10  at a predetermined interval against a tab  131   a  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  131   a  onto the web  10 . 
       FIG. 1B  shows a top plan view of a tape web  101  to be cut into tape tabs  111   a  and applied to a traveling web  10 . The tape web  101  has a tape web width  102  and the tape tabs  111   a  have a tape tab height  103 . The web  101  is cut at various points  104  depending upon desired dimensions for the resulting tabs  111   a . Each tab  111   a  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. 
       FIG. 1C  shows an overhead view of a web of material  10  having tape tabs  111   a  applied to the web  10  by the prior art apparatus of  FIG. 1A . The design of the tape web  111  and desirable tape tabs  111   a  allow a discrete protuberance  123  of the prior art apparatus  100  to create a sufficient attachment site  41  to maintain the tape tab  111   a  in positive adhesive contact with the web  10 . 
     While the previous apparatus  100  provides generally sufficient operation for the specified tab configuration, other tab configurations may not be accommodated by the setup.  FIG. 2A  is a perspective view of an embodiment of a transverse tape tab applicator disclosed in the application to which priority is claimed. Like the prior art embodiment of  FIG. 1A , 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. 
       FIG. 2B  shows a top plan view of a web  201  to be cut into tabs  211   a  and applied to a traveling web  10 . The web  201  has a web width  202  and the tabs  211   a  have a tab height  203 . The web  201  is cut at various points  204  depending upon desired dimensions for the resulting tabs  211   a . Each tab  211   a  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  211   a  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 . 
       FIG. 2C  depicts tabs  211   a ,  231   a  placed on a web  10  by the embodiment  200  of a transverse tape tab applicator apparatus shown in  FIG. 2A . However, despite the use of the same tape tab applicators  120 , 140  as the prior art embodiment  100 , the orientation of the tape tabs  211   a  prevents the discrete protuberance  123  of this embodiment  200  from creating a sufficient attachment site  42  to maintain the tape tab  211   a  in positive adhesive contact with the web  10 . That is, the relative dimensions of the tape tab  211   a  and the protuberance  123  provide the insufficient attachment site  42 . 
     In  FIG. 3A  there is shown a perspective view of an embodiment  209  of the present invention. Much like the apparatus in  FIG. 2A , 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  211   a  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. While such timing may be enabled in a variety of ways, the bump transfer surfaces  221 , 225  preferably travel in eccentric paths of revolution. 
       FIG. 3B  is an overhead view of a web  10  having tabs  211   a  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  211   a , thereby improving adhesion between the tab  211   a  and the web  10 . 
       FIG. 4  shows a front elevation view of the apparatus of  FIG. 3A . 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  211   a  are carried on the outer surface of the anvil  211   a . The tabs  211   a  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 . 
     The 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  211   a  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  211   a  to the web  10 . 
     A second embodiment  309  of the present invention is shown in  FIG. 5A . 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  FIG. 5A . 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. 
       FIG. 5B  shows a top plan view of a web  301  to be cut into tabs  311   a  and applied to a traveling web  10 . The web  301  has a web width  302  and the tabs  311   a  have a tab height  303 . The web  301  is cut at various points  304  depending upon desired dimensions for the resulting tabs  311   a.    
       FIG. 5C  shows an overhead view of a web of material  10  having tabs  311   a  applied to the web  10  by the embodiment  309  of  FIG. 5A . 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  311   a , thereby improving adhesion between the tab  311   a  and the web  10 . 
     As shown in  FIG. 3A ,  FIG. 4 , and  FIG. 5A , 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.  FIG. 6  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. 
     The foregoing is considered as illustrative only of the principles of the invention. Furthermore, since numerous modifications and changes will readily occur to those skilled in the art, it is not desired to limit the invention to the exact construction and operation shown and described. While the preferred embodiment has been described, the details may be changed without departing from the invention.