Abstract:
A method and apparatus for applying tape tabs to a traveling web of material when the tape tabs are moving at a non-parallel angle to the web of material. An anvil that carries the tape tabs moves at a perpendicular or other non-parallel angle to the web. The invention allows placement of the tape tabs at different arrangements, such as the tape tabs running parallel to the web of material. A wheel with a protuberance located near the web contacts the web to press the web down and adhere a tape tap to the moving web.

Description:
RELATED APPLICATION  
       [0001]     This application 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  
       [0002]     The present invention relates to processes and apparatus for applying tabs to traveling webs, and more specifically to application of multiple tabs to a traveling web. The invention has particular applicability to the manufacture of disposable diapers.  
         [0003]     The history of cutting and applying tape 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.  
         [0004]     Window-knife applicators are comprised of: 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 so as 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.  
         [0005]     Window-knife applicators have a few shortcomings, among which are: the difficulty in feeding tape webs with little axial stiffness; the tendency of the infeeding tape to adhere to the window knife-edge; and for exposed adhesive to contaminate the surfaces of the window knife. For effective cutting, some degree of interference between the cutting edges is necessary between the moving and stationary knife faces, so to minimize impact, precision in manufacturing must be maintained and provision must be made for a degree of resiliency. While applicators of this type have been tested to speeds of 1000 cuts per minute, the maximum practical speed capability of current designs is approximately 750 cuts per minute.  
         [0006]     Slip-and-cut applicators are typically comprised of (a) a cylindrical rotating vacuum anvil (b) a rotating knife roll and (c) 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.  
         [0007]     A common problem with slip-and-cut applicators lies in the tendency to accumulate various contaminants on their anvil surfaces. This is most frequently seen in the form of the release compounds found on the non-adhesive side of tape, which is shipped on pre-wound rolls. Where die-cut tapes are fed onto the surfaces of slip-and-cut applicators, it is common to also see an accumulation of adhesive contamination, as the adhesive has been exposed at the tape edges by the die-cutting process. The difference in speed between the tape web and the anvil tends to “wipe” adhesive from the tape web. Contamination of the anvil, whether by release compounds or by fugitive adhesive, interferes with the regularity of slip occurring between the tape and the anvil, causing registration and cut accuracy problems. Frequent cleaning is necessary to maintain any level of productivity.  
         [0008]     Another problem associated with slip-and-cut applicators occurs at the point of cut. Since the web being cut is traveling at a very low velocity compared to the anvil and knife velocity (perhaps 1/20th), the engagement of the knife with the tape web tends to induce a high tensile strain in the tape web. Having been placed under such a high level of stress, the tape web can recoil violently when the cut is finally completed, causing loss of control of the tape web. This “snap-back” effect increases with the thickness of the tape web. Thicker webs tend to prolong the duration of engagement with the knife before completion of the cut, thereby increasing the build-up of strain. This is a common process problem that is usually addressed by the provision of various shock-absorbing devices. One possible solution might have been to reduce the surface velocity of the knife, but substantially different velocities between the knife and anvil result in rapid wear of the knife edge and/or anvil face, depending on relative hardness.  
         [0009]     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. Consumer product manufacturers are offering 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.  
         [0010]     To overcome these 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 at a non-parallel angle to the web of material.  
       SUMMARY OF THE INVENTION  
       [0011]     The present invention has the added capability over the prior art of applying tape tabs to a running web of material at non-parallel feed positions.  
         [0012]     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.  
         [0013]     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 but not significantly displaced upon the anvil surface. The segments 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.  
         [0014]     At a point downstream 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 segments. The traveling web is proceeding at a non-parallel angle and direction to the rotational direction of the anvil. A mechanically operated device, which may be as simple as a protuberance on a rotating cylinder, presses the target zone of the traveling web against the exposed adhesive of the tape segment as it is presented on the anvil surface. The protuberance preferably has a surface velocity substantially identical to that of the traveling web.  
         [0015]     Given the extremely low moment of inertia of the tape segments and the aggressive adhesion provided between its exposed adhesive and the compatible surface of the traveling web, each successive segment is successfully transferred to the traveling web, accelerating almost instantly to the speed of the traveling web.  
         [0016]     A key aspect of this invention lies in the method and apparatus used to affect the transfer of the tape segments from the anvil to the traveling web. In accordance with the invention, a vacuum commutation system is configured to remove or reduce the level of vacuum used to hold each tape segment to the anvil surface just before the point of transfer. The materials and finishes selected for the anvil and the transfer protuberances provide a situation in which the coefficient of friction between the protuberances and the traveling web is relatively high, while the coefficient of friction between the tape segment and the anvil is relatively low. The highly aggressive nature of the bond between the adhesive side of the tape segment 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 segment to adhere to the anvil surface will not influence the traveling web. The process requires that some slip occurs, and in accordance with the invention, slip occurs only between the tape segment and the anvil surface.  
         [0017]     The present invention allows for placement of tape onto areas of the disposable garment perpendicular to or at another non-parallel angle to the waistband of the disposable garment. 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 the diaper. Likewise, the present invention provides a method to attach tapes to the sides of garments that are manufactured according to a transverse process. 
     
    
     BRIEF DESCRIPTION OF THE DRAWINGS  
       [0018]      FIG. 1  is an overhead diagrammatic view of tape being applied according to the prior art.  
         [0019]      FIG. 2  is an overhead diagrammatic view of tape being applied according to the present invention.  
         [0020]      FIG. 3  is a perspective view illustrating an embodiment of the invention.  
         [0021]      FIG. 4  is a front elevational view of the equipment of  FIG. 3 .  
         [0022]      FIG. 5  is a perspective view of the present invention applied to an undergarment.  
         [0023]      FIG. 6  is an overhead diagrammatic view of an alternate embodiment of the present invention. 
     
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0024]     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 structure. While the preferred embodiment has been described, the details may be changed without departing from the invention, which is defined by the claims.  
         [0025]      FIG. 1  shows an overhead view of a web of traveling material  10  having tape tabs  12  applied to the web  10  according to the prior art. The tape tabs  12  are applied from an anvil carrying an adhesive material (not shown) that rotates in the same direction as the movement of the web  10 . The tabs  12  are placed so that the tabs  12  are attached perpendicular to the web  10 .  
         [0026]      FIG. 2  is an overhead view of the improvement of the present invention. The tabs  12  are attached parallel to the moving web  10 . The change in orientation is possible since an anvil that carries the adhesive tape  12  rotates in a direction perpendicular to the moving web  10 . The advantages of such an arrangement will be discussed later. Two separate anvils contacting the web  10  apply the tape  12 , with one anvil coming in contact with each edge of the web  10 .  
         [0027]     In  FIG. 3  there is shown, a simplified device in accordance with the invention, illustrating the application of tabs  52  and  54 , which have free ends extending parallel from opposite sides of a diaper-forming web  50 . These free ends of tabs  52  and  54  may be provided with loops on one side of the diaper-forming material and hooks on the opposite side to form hook and loop fasteners on the diapers commonly referred to as Velcro®. In other cases, the tabs on at least one side may be coated with a pressure sensitive adhesive protected until use by a release layer.  
         [0028]     As further seen in  FIG. 3 , an adhesive-coated tape web  61  is fed over a roller  64  onto an anvil  60 . The web  61  is fed to the anvil  60  at a speed such that the web speed of web  61  approximately equals the speed at which the outer periphery of anvil  60  is traveling. If desired, the anvil  60  may rotate at a slightly higher speed than the linear speed of the web  61 . Blades  56  of a rotary cutter  58  are also traveling at a peripheral speed equal to that of anvil  60 . As seen in  FIG. 3 , after cutting, a series of tabs  52  are carried on the outer surface of anvil  60 . Tabs  52  are held in place by vacuum provided within the interior of anvil  60 . The adhesive-coated surface of web  61  is facing outwardly while a non-tacky or uncoated surface engages the exterior anvil  60 .  
         [0029]     A similar anvil  62  engages a second adhesive-coated web  66 . The webs  61  and  66  may have adhesive coated on one-half of their width and a hook or loop-type fastener provided on the opposite half of the width in order to form the laterally extending tabs  52  and  54 . Blades  56  of rotary cutter  58  and blades  57  of a second rotary cutter  59  cut the webs  61  and  66 , respectively. The cutters  58  and  59  are driven by respective rotatable shaft  68  and  70 . Similarly, anvils  60  and  62  are driven by respective central shaft  72  and  74 . Rotatable disks  76  and  78  provided with protrusions  80  and  82  serve to deflect the edges of the web  50  toward the respective anvils  60  and  62  in order to simultaneously pick up the tabs  54  and  52  on opposite sides of the web  50 , as shown.  
         [0030]      FIG. 4  shows a front elevation view of the apparatus of  FIG. 3 . The incoming webs  61  and  66  are fed to the rollers  64  and  84 . The webs  61  and  66  travel further to come into contact with the anvils  60  and  62 . The webs  61  and  66  are fed to the anvils  60  and  62  at a speed such that the web speed of the webs  61  and  66  approximately equals the speed at which the outer periphery of  60  and  62  are traveling. If desired, the anvils  60  and  62  may rotate at a slightly higher speed than the linear speed of the webs  61  and  66 . The blades  56  and  57  of the rotary cutters  58  and  59  are also traveling at a peripheral speed equal to that of anvils  60  and  62 . As seen in  FIG. 4 , after cutting, a series of tabs  52  and  54  are carried on the outer surfaces of the anvils  60  and  62 . Tabs  52  and  54  are held in place by vacuum provided within the interiors of anvils  60  and  62 . The adhesive-coated surface of the webs  61  and  66  are facing outwardly while a non-tacky or uncoated surface engages the exterior of the anvils  60  and  62 .  
         [0031]     The web  50  of diaper material is caused to travel in a path slightly displaced from the outer surface of the rotating anvils  60  and  62 , but in close proximity thereto. Just above the web  10  the rotating wheels  76  and  78 , which rotates at a peripheral velocity equal to the lineal velocity of web  50 , which, in turn, is substantially greater than the peripheral velocity of the anvils  60  and  62 . The anvils  60  and  62  may travel at a peripheral velocity either equal to or somewhat greater than the velocity of web  50 . In practice, to realize the benefits of this invention, the peripheral velocity of anvils  60  and  62  should not be greater than about 5 times the velocity of web  50 .  
         [0032]     As the tabs  52  and  54  travel toward the web  50 , the protrusions  80  and  82  located on the wheels  76  and  78  depress the web  50 , causing the web  50  to come into contact with the anvils  60  and  62 , which adheres the tabs  52  and  54  to the web  50 .  
         [0033]     As shown in  FIG. 4 , a shaft  86  that controls the wheels  76  and  78  is aligned perpendicular to the shafts  72  and  74 , which allows the tabs  52  and  54  to be placed in the parallel fashion shown in  FIG. 3 . While the invention is shown having one protrusion  80  and  82  on each wheel  76  and  78 , the invention may also be used having two or more protrusions located on the wheels. Likewise, the invention may be used with only one wheel instead of two. The anvils  60  and  62  are shown rotating in the same direction, but it may be possible to arrange the anvils so that they are rotating in opposite directions if preferred, thereby allowing the same relative edges of the tabs  52  and  54  to be placed on the web  50  in the same manner.  
         [0034]     For instance, as shown in  FIG. 5 , a disposable undergarment  100  is considered. The garment  100  has a releasable flap  102  located on the rear  104  of the undergarment  100 . The present invention allows placement of the tabs  52  onto the flap  102  in a parallel fashion, which allows the flap  102  to be opened or closed. Such an arrangement is useful for children to check if the undergarment  100  has been soiled. If the undergarment  100  has been soiled, the arrangement allows for the soiled flap  102  to be rolled up and secured with the tabs  52 .  
         [0035]     The invention has also been contemplated where adhesive may be placed onto a web that is not perpendicular to the web of material.  FIG. 6  represents a diagrammatic view of such an arrangement. The tabs  12  are placed onto the web of material  10  at approximately a  45 E angle. The angle may adjusted so that the tabs  12  may be placed on the web  10  so that the tabs  12  may lie between any angle parallel to perpendicular to the traveling web  10 .  
         [0036]     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.