Abstract:
The invention provides a process and apparatus for the manufacture of disposable absorbent articles comprising the application of discrete web panels ( 40   a   , 40   b ) to a receiving web ( 1 ), wherein a plurality of first web panels ( 40   a ) and second web panels ( 40   b ) are cut from the same continuous web ( 40 ), and wherein the process comprises the steps of: cutting the continuous web ( 40 ) to form at least a first web panel ( 40   a ) and a second web panel ( 40   b ); rotating the second web panel ( 40 ); and applying the first web panel ( 40   a ) and the second web panel ( 40   b ) to the receiving web ( 1 ). The object of the invention is achieved by rotating the second web panel ( 40   b ) about an axis (A) perpendicular to the plane of the second web panel ( 40   b )

Description:
The invention relates to a process for manufacturing profiled disposable absorbent articles, and to an apparatus for performing the process. In a preferred embodiment the invention provides a process and apparatus for providing profiled side-panels, in particular elastic side-panels, without waste of the side-panel material. In particular, diapers or training pants may be made by the process of the invention having side “cut-outs” for better fit around the legs of the wearer, but the process may also be applied to feminine hygiene articles, adult incontinence articles, and other disposable absorbent articles. 
     Disposable absorbent articles have become very popular in the market place today. Many of these articles include features such as side-panels that provide a variety of functions including improved containment characteristics and better, more comfortable fit. 
     An overriding consideration in the construction of a disposable absorbent article is the cost of manufacturing the article, including the materials cost. The present invention provides methods for manufacturing side panels for absorbent articles with little or no wasted material. Thus, the side panels made by the process of the present invention can be provided at relatively lower cost than many of the side panels that are currently manufactured using techniques in which material is wasted. Processes which reduce or avoid material waste are disclosed in the following references. 
     U.S. Pat. No. 5,034,007, issued on Jul. 23, 1991, describes a method for cutting “nested ears” by making a periodic convex/concave cut lengthwise along a web. The two cut portions of the web are then separated and symmetrically arranged in the width direction with the straight edges on the inside and the convex/concave edge aligned on the outside. An alternative method of achieving the same result is disclosed in EP-A-0 396 050, published on Nov. 7, 1990. This discloses individually reversing all of the cut portions by turning them 180° about an axis lying in the plane of the web. 
     WO96/24319, published Aug. 15, 1996, discloses a method for manufacturing activated side-panels cutting in a “nested” pattern, and rotating all of the cut portions of the web through 180° about an axis lying in the plane of the web prior to attaching them to the diaper web (in particular this is illustrated in FIG. 7). 
     It is an object of the present invention to provide an alternative method of achieving the waste-saving advantages of “nested ears”, and to provide an apparatus for use in the method. 
     The invention provides a process and apparatus for the manufacture of disposable absorbent articles comprising the application of discrete web panels to a receiving web, wherein a plurality of first web panels and second web panels are cut from the same continuous web, and wherein the process comprises the steps of: 
     cutting the continuous web to form at least a first web panel and a second web panel; 
     rotating the second web panel; and 
     applying the first web panel and the second web panel to the receiving web. 
     SUMMARY OF THE INVENTION 
     The object of the invention is achieved by rotating the second web panel about an axis perpendicular to the plane of the second web panel. 
    
    
     BRIEF DESCRIPTION OF THE DRAWINGS 
     FIG. 1 shows a perspective view of an apparatus for use in the process of the present invention; 
     FIG. 2 shows a side elevation view of the apparatus of FIG. 1; 
     FIG. 3 a  shows a schematic side elevation view of a production line for the manufacture of an absorbent article; 
     FIG. 3 b  shows a schematic side elevation view of a part of a production line assembly as shown in FIG. 3 a  comprising an apparatus of the present invention; 
     FIG. 4 shows a plan view of web panels after cutting, according to one embodiment of the process of the present invention. 
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
     FIG. 1 shows a perspective view of an apparatus according to the present invention. The apparatus comprises two rotating drums  60 ,  70  which are essentially oriented symmetrically. The two drums  60 ,  70  apply discrete first and second web panels  40   a ,  40   b  to the left and right sides of the receiving web  1 . In FIG. 1 a pair of incoming webs  40  are fed to the two sides of the apparatus and are cut in a nested pattern (see, for example, FIG.  4 ), and the discrete first and second web panels  40   a ,  40   b  of the incoming webs are held on vacuum shells  80   a ,  80   b  which are arranged around the circumference of each of the rotating drums  60 ,  70 . The receiving web  1 , the incoming webs  40 , and the cutting roll  39  are not shown in FIG. 1 to simplify this illustration. 
     The drums  60 ,  70  are rotated about a main axis of the apparatus. In the embodiment illustrated in FIGS. 1 and 2, the main axis is oriented horizontally, but this main axis need not necessarily be horizontal in all cases. Most preferably the two drums  60 ,  70  are rotated synchronously, at the same speed. 
     In the embodiment shown in FIG. 1, alternate vacuum shells  80   b  are mounted on rotatable shafts  81  and are rotatable through 180° about an axis A which is radial with respect to the drum  60 ,  70 . Each of the rotatable shafts  81  is connected, by means of a rack and pinion  82 ,  83 , to a cam follower which runs around a shell turning cam  84 . The shell turning cam  84  is shaped so that the rack and pinion  82 ,  83  operate to rotate the alternate vacuum shells  80   b  through 180° during a first part of the cycle, prior to transfer of the second web panels,  40   b  of the incoming web to the receiving web  1 , and then return the vacuum shells  80   b  to their original orientation by rotating them back through minus 180° during a second part of the cycle after the transfer. 
     In addition, during the first part of the cycle, a shell lifting cam (not shown in FIG. 1 or  2 ), acts to “lift” the vacuum shell  80   b  radially outwards from the drum  60 ,  70 . This action helps to apply the second web panels  40   b  of the incoming web  40  to the receiving web  1  at a transfer step. During the second part of the cycle, after the cut web panels  40   b  of the incoming web have been transferred to the receiving web  1 , the vacuum shells  80   b  are “withdrawn” radially inwards with respect to the drum  60 ,  70 . During the second part of the cycle, or subsequent to the second part of the cycle, the vacuum shells  80   a  (i.e. those vacuum shells which have not been rotated during the first part of the cycle) are “lifted” radially outwards from the drum  60 ,  70 . This action helps to apply the first web panels  40   a  of the incoming web to the receiving web at a transfer step. Finally the vacuum shells  80   a  are “withdrawn” radially inwards with respect to the drum  60 ,  70 , and the cycle is ready to repeat. 
     In the embodiment of the invention shown in FIGS. 1 and 2 the second web portion  40   b  is rotated through 180° in order to provide side panels, and preferably to provide alternately front and rear side panels for an absorbent article such as a diaper. In an alternative embodiment the second web panel  40   b  is rotated though 90° in order to provide a component in the cross-machine direction, which is perpendicular to the first web panel  40   a , preferably wherein the first and second web panels  40   a ,  40   b  are elastic. In this alternative embodiment of the invention, the cross-machine direction component may be a waist elastic for an absorbent article such as a diaper. In another alternative embodiment the panels applied during the first part of the cycle of FIG. 1 may be applied directly, without rotation, whilst the alternate panels which are subsequently applied in the second part of the cycle may be rotated (preferably through 180°) prior to application to the receiving web. 
     FIG. 3 a  shows a side elevation view of a continuous process for making an absorbent article  144 . A continuous receiving web  1  is assembled from an absorbent pad element, or core  120 , which is encased between a liquid-pervious topsheet  121  and a liquid impervious backsheet  123 . The absorbent cores  120  are fed into the nip between a pair of laminating rolls  125 ,  126  at regularly spaced intervals by means of an infeed conveyor  127 . In a preferred embodiment, the cores  120  are comprised of airfelt, within a cellulosic tissue envelope, to provide integrity to the core in use. The backsheet  123  is coated on its inner surface with beads or spirals of adhesive  128 , for affixing the backsheet to the core  120 . Continuous bands of elastic  130  are fed from metering rolls  131 ,  132  and  133  past a glue nozzle  135 . The S-wrap arrangement of the rolls  131 ,  132  and  133  minimises deformation of the elastic band  130  and allows for accurate control of the speed of the elastic. The elastic bands are fed into the direction of transport, F, at a lower speed than the cores  120 , the backsheet  123  and the topsheet  121 , so that the elastic bands  130  are stretched. After passing through the combining nip, the web passes onto a perforated vacuum conveyor belt  137 . A vacuum suction box  139  draws the web against the conveyor belt  137 , to maintain a uniform tension in the receiving web  1 . The web passes at a constant speed of transport to the infeed side  4  of the assembly  2  for periodically changing the speed of web. In the assembly  2 , the receiving web  1  can be slowed down, or stopped and is contacted by the apparatus of the invention  38 . The apparatus  38  comprises means for providing a web of material such as an elastic side panel, a waist cap or a strip of reinforcement material. The apparatus  38  can be located on the side of the topsheet  121  or on he side of the backsheet  123 . The web  1  leaves the outfeed side  6  of the assembly  2  at the constant web speed. The speed of the receiving web portions located upstream and downstream from the assembly  2  along upstream trajectory  3  and downstream trajectory  5  is not affected by the change in speed of those parts of the receiving web  1  that are passing through the assembly  2 . 
     FIG. 3 b  shows the assembly  2  for changing the speed of a flexible receiving web  1  of relatively low tear strength. By flexible, it is meant that the receiving web  1  can be transported along a curvilinear trajectory and will adapt its shape so as to conform to the trajectory. The receiving web  1  is formed of flexible material, such as paper, airfelt, plastic etc. and can be comprised of the core  120 , the topsheet  121 , the backsheet  123  or any combination thereof. 
     The receiving web  1  is transported along the upstream trajectory  3  with a constant velocity of transport V 0 , in the machine direction F. The upstream trajectory  3  is formed by the length of the receiving web  1  which extends to the right of the first guide roller  9  in FIG. 3 b , and which is moving towards the infeed side  4  of the assembly. After passing through the assembly, the receiving web  1  exits at the outfeed side  6  and is transported at constant velocity V 0  along the downstream trajectory  5 , which extends to the left of the guide roller  11 . The upstream and downstream trajectories need not correspond to the machine direction, and can be formed by straight-line or curvilinear paths. 
     The guide rollers  9  and  11  are rotationally connected to the frame  35 . The guide rollers  9 ,  11  have a fixed position. The receiving web  1  is looped around an upstream and a downstream transport roller  13 ,  15  which are mounted on a sled  41 . The sled  41  is cyclically translated along the frame  35 , generally parallel to the machine direction F, by drive motor  36 . 
     An intermediate trajectory  7   a ,  7   b ,  7   c  of the receiving web  1  is located between the upstream guide roller  9  and the downstream guide roller  11 , and comprises a first section  7   a  and a third section  7   c , of variable length, located between the upstream guide roller  9  and the upstream transport roller  13  and the downstream transport roller  15  and the downstream guide roller  11  respectively. The second section  7   c  of the intermediate trajectory  7  is located between the transport rollers  13  and  15  and is of constant length. 
     Because of the symmetry of the intermediate trajectory  7   a ,  7   b ,  7   c , the increase in length of the first section  7   a , upon displacement of the sled  41  opposite to the machine direction F and away from the equilibrium position  39 , is compensated by an equal decrease in length of the third section  7   c , and vice versa. As the length of the second section  7   b  is constant, the whole intermediate trajectory  7   a ,  7   b ,  7   c  is independent of the position of the sled  41  with respect to the frame  35 . 
     When the part of the receiving web that is located along the second section  7   b  of the intermediate trajectory  7   a ,  7   b ,  7   c , is stationary (or at least it is slower than the speed of the web speed V 0 ) relative to the frame  35 , the web  1  is contacted by the apparatus  38  which is positionally stationary (or at least slower) with respect to the frame  35 . After the apparatus  38  has interacted with the receiving web  1 , the web is accelerated along the section  7   b  of the intermediate trajectory towards the outfeed side  6  of the assembly  2 , and is supplied to the downstream trajectory  5  with web speed V 0 . 
     The guide rollers  9 ,  11  and the transport rollers  13 ,  15  are driven by a drive member in the form of a closed loop  50  and pulleys  52 ,  53  and  54 . The loop  50  is partly parallel to the intermediate trajectory  7   a ,  7   b ,  7   c . The loop  50  is driven at a constant speed which is equal to the speed of transport V 0 , of the web  1  by a single drive motor  51 . By driving the guide rollers  9 ,  11  and the transport rollers  13 ,  15 , the strain exerted on the web  1  is minimised and can be limited to the acceleration forces, which are acting to change the speed of the web. Further details of suitable assembly are disclosed in EP-A-0 652 175, published on May 10, 1995. 
     FIG. 4 shows a web  40  which has been cut into discrete portions  40   a ,  40   b . Second we portions  40   b  are subsequently rotated about their axis A. 
     The first and second web panels  40   a ,  40   b  are applied, and preferably affixed, to the receiving web  1  using any conventional method such as by gluing with adhesives, such as melt adhesives, or use of self-adhesive components, or by use of ultrasonic welding, heat sealing or the like.