Abstract:
This invention proposes a new, improved method and apparatus for applying web segments to a traveling web. These web segments, sometimes called ears or wings, may be asymmetrical or otherwise incompatible with the usual slip-and-cut method. The asymmetrical shape may have differing web tensions which can cause the web segments to be improperly engaged with the vacuum holes on an anvil roll. The present invention utilizes both circumferential rows of vacuum holes and an additional pattern of ear retaining vacuum holes. The circumferential rows of vacuum holes are activated consecutively by vacuum commutation, however, the pattern of ear retaining vacuum holes are activated simultaneously to counter the effects of differing web tensions on the ear portions.

Description:
BACKGROUND OF THE INVENTION 
     The present invention relates to disposable hygiene products and more specifically, to methods and apparatuses for processing disposable hygiene products. More specifically, the invention relates to cutting and applying segments of one web to attach to a disposable hygiene product. Various types of automatic manufacturing equipment have been developed which produce the desired results with a variety of materials and configurations. 
     When manufacturing hygiene products, such as baby diapers, adult diapers, disposable undergarments, incontinence devices, sanitary napkins and the like, a common method of applying discrete pieces of one web to another is by use of a slip-and-cut applicator. A slip-and-cut applicator is typically comprised of a cylindrical rotating vacuum anvil, a rotating knife roll, and a transfer device. In typical applications, an incoming 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 incoming web is allowed to “slip”. A knife-edge, mounted on the rotating knife roll, cuts a off a segment of the incoming web against the anvil face. This knife-edge is preferably moving at a surface velocity similar to that of the anvil&#39;s surface. Once cut, the web segment 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 web segment is transferred to the traveling web. 
     Typical vacuum rolls used in the prior art have rows of vacuum holes which are fed by cross-drilled ports, each being exposed to the source of vacuum by commutations, as the ports move into a zone of negative pressure in a stationary manifold. Such a configuration serves to apply vacuum sequentially to each successive row of holes. 
     A common 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 infeeding web tends to induce a high tensile stress in the infeeding web. Having been placed under such a high level of stress, the infeeding web can recoil violently when the cut is finally completed, causing loss of control of the infeeding web. This “snap-back” effect increases with the thickness of the infeeding web. Thicker webs tend to prolong the duration of engagement with the knife before completion of the cut, thereby increasing the build-up of stress. 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. 
     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 fastener tabs being attached to those products has also increased. Consumer product manufacturers are now offering tapes which are die-cut to complex profiles and which may be constructed of materials incompatible with existing applicators. For instance, a proposed fastener 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 slip-and-cut applicator which cannot successfully apply die-cut tape segments. Existing applicators cannot successfully apply fastener 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 fastener configurations and overcoming other shortcomings of prior art applicators. 
     Slip-and-cut apparatus are well known for their ability to cut relatively short segments of one web and place them accurately on another, higher speed web. Certain materials, however, behave badly in these applications. The tension pulsation caused by the cutting may cause the material to snap back, losing its natural track down the moving surface of the anvil roll. This is especially common with thick webs. Other materials, such as nonwoven fabrics, may be difficult to control because they are very porous and provide little resistance to air flow to keep the material on track. Still other materials, such as certain perforated films may possess texture qualities which tend to be very unstable on the anvil surface, acting instead like a puck on an air hockey table. 
     These problems are further exacerbated by using materials with a very low modulus of elasticity. Here, even very low levels of vacuum at the anvil surface may cause the material to stretch with the advancing movement of the anvil. The sudden change of tension seen when the knife cuts this over-stretched web can result in severe snap-back and complete loss of position, relative to the intended centerline. Likewise, webs with very high moduli may snap back violently when the web is cut. 
     The prior art is quite successful when processing full-width or symmetrical webs, which are drawn uniformly forward by the sliding vacuum surface on which they are held. Attempts to process asymmetrical webs on such a surface are less successful, as the draw of the advancing vacuum pattern will act differently on parts of the web which have differing lines of tension. For instance, a die-cut ear web for a disposable diaper may have only a narrow continuous portion along one edge, with the opposite edge being more or less scalloped in shape. 
     It is therefore an object of this invention to provide an apparatus which can maintain control over die cut web sections of various shapes. 
     SUMMARY OF THE INVENTION 
     The present invention provides a method and apparatus which provides high speed vacuum porting to selected vacuum pattern areas on a rotating cylindrical roll. This invention has the advantage of being able to “switch on” selected areas rather than discrete rows. 
     In a typical configuration of a slip-and-cut applicator, there is a pattern of vacuum holes distributed to evenly draw the entering web onto the anvil&#39;s surface and thence into a cut point where a knife edge engages an anvil, thus severing the web into discrete segments if so desired. The invention provides a generally cylindrical anvil body connected to a source of vacuum. The anvil roll has an ear retaining portion on its outer surface. This ear retaining portion is formed with a plurality of vacuum holes. A vacuum slot is provided on an end face surface (commutating surface) of the anvil roll and is adapted to put the plurality of vacuum holes in communication with the vacuum source. The anvil roll is utilized in connection with a rotary knife to cut small segments of an incoming web. The anvil roll then transfers those cut segments to an additional web. 
     It is desired to immediately grasp and hold the ear at the instant of the cut of the continuous web as it is separated into discrete segments. As soon as the ear is cut from the infeeding web, instantaneous control must be established. 
     One embodiment of this invention provides a cylindrical anvil roll which is symmetrical about a center circumferential plane. This embodiment allows two incoming webs to be utilized, allowing two segments to be cut, one on either end of the anvil roll, each time the rotary knife engages the anvil roll. 
     Additionally, the anvil roll may have an additional set of ear retaining portions formed in diametric opposition to the first set of ear retaining portions. In such an embodiment, the knife roll would engage the anvil roll two times for each rotation of the anvil roll, thus producing up to four cut segments per rotation of the anvil roll. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         FIG. 1  is a diagrammatic side view of a Prior Art process. 
         FIG. 2  is a top view of the ear forming web including an individual ear detached from the web. 
         FIG. 3  is a front view of the anvil roll of the present invention. 
         FIG. 4  is a perspective view of the anvil roll of the present invention. 
         FIG. 5  is a cross sectional view of the anvil roll of the present invention. 
         FIG. 6  is a side view of the anvil roll of the present invention, showing an endface of the anvil, and a vacuum manifold pattern applied to vacuum holes disposed on the endface of the anvil. 
     
    
    
     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. 
     Referring to the drawings there is seen in  FIG. 1  a diagrammatic illustration of a prior art process for applying tabs to webs in a diaper making process. The present invention can use this prior art method of affixing the ears  12  to the web  10 , with a different anvil, the new anvil  114  described below. Web  10  is a composite material used in formation of diapers which is generally formed of various layers of material such as plastic back sheets, absorbent pads and nonwoven topsheets. A series of ears  12  are applied to web  10 . In the illustrated process a rotatable vacuum anvil  14  is used to supply the ears  12  to web  10 . Anvil  14  has internally reduced air pressure or vacuum (not shown), and a plurality of openings  24  are provided through its surface to enable suction of the tab segments  13  against the anvil surface  14 . A web of the ear tab forming material  16  is fed by rollers  20  and  22  against the anvil surface  14  where it is cut into segments by a rotary knife  18 . 
     In the prior art, the surface of the anvil roll  14  has vacuum holes  24  on its smooth surface. In a typical configuration of a slip-and-cut applicator, there is a pattern of vacuum holes  24  distributed to evenly draw the entering web onto the surface of anvil  14  and thence into the cut point where the knife edge  18  engages the anvil  14 . 
     It can be seen from  FIG. 1  that in the prior art, the infeed of the ear tab forming material  16  can be at a first speed (with individual ears  12  spaced together), after which the individual ears gain speed to the speed of the anvil  14 . Typical infeed speeds could be 120 mm/product for the infeed, while anvil speeds could be 450 mm/product on the anvil. This transition from the slower first speed to the quicker second speed takes place at the cut point, the ear tab forming material  16  slipping on the anvil  14  until cut. However, immediately at the transition cut point  19  from the slower speed to the faster speed, it is desired to place vacuum on the ears because centrifugal force would try to throw the ears off of the vacuum anvil  14 . 
     In both the prior art and the present invention, a continuous ear forming web  16  is provided to the system. The web  16  is comprised of two portions  13  and  15 , as shown in  FIG. 2 . Segment  13  is more specifically referred to as the tab section of the ear  12 , segment  15  is the ribbon section of the ear  12 . The ear forming material  16  is cut into individual ears  12  by the rotary knife  18  as shown in  FIG. 1 , along lines such as the dashed lines shown in  FIG. 2 . 
     Referring now to  FIG. 3 , a front view of an anvil roll  114  of the present invention is shown carrying ear forming material  16  (and later, an ear  12 ) in phantom. The anvil roll  114  is preferably formed with two vacuum portions  116  separated by a center groove portion  118 . The vacuum portions  116  are preferably mirror images of each other. The anvil roll  114  is symmetrical about a center plane through its circumference. Each vacuum portion  116  contains several circumferential rows of circular vacuum holes  24 . Each vacuum portion  116  may also contain a circumferential groove  120  with an additional circumferential row of vacuum holes  24  located in the circumferential groove  120 . 
     The preferred embodiment of the anvil roll  114  of the present invention is also formed with two diametrically opposed anvil pockets  122  and two diametrically opposed pairs of ear retaining portions  124 . The ear retaining portions can be created as inserts, with different vacuum patterns applied as the user deems necessary. Each anvil pocket  122  is a groove which extends across the face of the entire anvil roll  114 . One ear retaining portion  124  is located on each of the vacuum portions  116 . Each ear retaining portion  124  has an ear vacuum hole pattern  126  made of a plurality of vacuum holes  24  located at or near the surface of the anvil roll  144 . The preferred embodiment, as shown in  FIG. 3  is a plurality of rows of vacuum holes  24 , each row having a plurality of vacuum holes  24 , although more or less than those configurations or patterns shown can be used. 
     In operation, two webs of ear material  16  are carried by the anvil  114 . One web of ear material  16  is located on each vacuum portion  116 . A single ear  12  is cut from the ear web  16  when the rotary knife  18  engages the anvil roll  114  at the anvil pocket  122 . Immediately after a single ear  12  is cut from the ear web  16 , the single ear  12  is located on the ear retaining portion  124 , particularly the tab portion  13  of the ear  12  as shown in  FIG. 2 . At this point the vacuum in the ear retaining portion  124  has been engaged to secure the single ear  12  to the anvil roll  114 . As the anvil roll  114  rotates the vacuum is released at a predetermined location so that the single ear  12  can be applied to the diaper web  10 . Because this configuration has two vacuum portions  116 , a pair of two ears  12  is cut each time the rotary knife  18  engages the anvil toll  114 . This allows for two pair of ears  12  to be cut with each revolution of the anvil roll  114 . Shown in dotted line in  FIG. 3  is a vacuum slot  128 , described below. 
     Referring now to  FIG. 4 , a perspective view of the anvil  114  is shown. The anvil  114  will be described in relation to its endface and its outer surface, the outer surface that surface shown on  FIG. 3  and the endface the two ends of the anvil  114 . 
     The vacuum slot  128  contains a plurality of vacuum holes  24  that allow commutation of the vacuum to the entire ear vacuum hole pattern  126 , allowing the pattern  126  to be activated simultaneously, as opposed to each of the rows that comprise the vacuum of vacuum holes  24  being enabled one at a time. The vacuum pattern  126  is activated utilizing drilled ports  28  that communicate the vacuum from the slot  128  to the individual holes  24  of the pattern  126 . It should be noted that the pattern  126  can also be provided with a depressed slot configuration so that it too is all simultaneously enabled with vacuum. 
     The remaining vacuum holes  24  provided on the anvil roll  114  are enabled sequentially, by known vacuum commutation method utilizing cross drilled ports  28 . 
     The vacuum slot  128  is provided at a first radius R 1  on the anvil roll  114 , the remaining vacuum holes provided at a different R 2 . The differing radii R 1  and R 2  allow two vacuum manifolds (not shown) to communicate each at a different radius, R 1  or R 2 , thus selectively applying vacuum to the anvil. 
     Referring now to  FIG. 5 , a cross sectional view of the anvil roll  114  of the present invention. In this embodiment, the slot  128  has been placed at R 2 . It is appreciated that the slot  128  communicating with the pattern  126  can be placed at either R 1  or R 2 , and the remaining vacuum holes  24  communicating with drilled ports  28  can be interchanged at either R 1  or R 2 . For machining purposes, it is likely preferable to place the slot  128  communicating with the pattern at R 2  for simplicity in machining. 
     Referring now to  FIG. 6 , a side view of the anvil roll  114  is shown, showing the endface of the anvil, or the circular portion of the cylindrical body  114 . The ear web  16  is shown infeeding to the anvil  114 , where it is then cut with the rotary knife  18 . It is desired to apply the vacuum to the pattern  126  simultaneously with the knife cut. 
     The range of vacuum application is provided for with a manifold (not shown) that continuously applies vacuum to vacuum patterns V 1  and V 2 . Vacuum pattern V 1  is at R 1 , Vacuum pattern V 2  is at R 2 . Vacuum pattern V 1  applies vacuum to the slot  128  each time the slot  128  rotates through the vacuum pattern V 1  provided on the manifold. When the slot  128  is in communication with V 1 , vacuum is applied to vacuum holes  24  associated in the slot  128  on the endface of the anvil for commutation to the pattern  126  on the outer surface of the anvil  114 . When the slot  128  is not in communication with V 1 , the vacuum to the pattern  126  is turned off. 
     Vacuum pattern V 2  is applied to the vacuum holes  24  disposed on the endface of the anvil  114  and the associated circumferential ribbon vacuum hole pattern on the outer surface of the anvil  114  throughout V 2 . As each successive vacuum hole  24  rotates through V 2 , the vacuum is on. As each successive vacuum hole  24  leaves V 2 , its vacuum is turned off. 
     From the center of the endface, a radius extending to the contact point of the knife  18  with the anvil roll  114  can be extended, and as the anvil roll rotates through angle B as shown, the rotation of the ear  12  will be from the knife point to the transfer point TP. It is throughout this angle B that vacuum is desired across the pattern  126  and onto the ear  12 . To accomplish this, a smaller angle C has vacuum applied to it. The angle C can be expressed mathematically as the angle B minus twice the width  128 ′ of the slot  128 . This is because pattern  126  is placed in communication with the slot  128 , the slot  128  communicates vacuum simultaneously to the pattern  126 . Therefore, the leading edge of the ear  12  and the trailing edge of the ear  12  will receive vacuum at the same time. Therefore, the user must allow the leading edge of the ear  12  to pass by the knife  18  the desired length of the ear  12  prior to engaging the vacuum onto the ear  12 . Similarly, prior to arriving at the transfer point TP, the vacuum will have to be released on both the leading and trailing edges of the ear  12  simultaneously, allowing the ear  12  to continue on its downstream path. 
     An angle A, larger than angle B, is provided to define V 2 , as it is desired to draw the web  16  into contact with the anvil both prior to and during cutting by the knife  18 . 
     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, which is defined by the claims.