Abstract:
Apparatus and methods are provided to allow for creation an elastic laminate. Non-stretched elastic can be laid at peaks over a nonwoven layer contained in valleys and atop peaks. Stretched elastic can be laid over tented nonwoven to create nonwoven tunnels when a second nonwoven is laid atop the first nonwoven and elastic, and the tunnels resist un-stretching of stretched elastic strands by frictional or obstruction forces. A laminated material comprising a first and second layer of material bonded at spaced apart bond sites is disclosed, with a plurality of elastic strands disposed in a non-linear manner between said first and second layer of material, so that said strands meander in a cross-machine direction and traverse a machine direction line, restraining movement of the strands by frictional forces between the strands and the non-woven layers.

Description:
RELATED APPLICATION 
       [0001]    This application claims the benefit of co-pending U.S. Provisional Patent Application Ser. No. 62/041,876, filed 26 Aug. 2014. 
     
    
     BACKGROUND OF THE INVENTION 
       [0002]    This invention relates to an apparatus and method for producing a laminate of elastic material by attaching a non-elongated elastic to a carrier web or webs. While the description provided relates to diaper manufacturing, the apparatus and methods are easily adaptable to other applications. 
         [0003]    Generally, diapers comprise an absorbent insert or patch and a chassis, which, when the diaper is worn, supports the insert proximate a wearer&#39;s body. Additionally, diapers may include other various patches, such as tape tab patches, reusable fasteners and the like. The raw materials used in forming a representative insert are typically cellulose pulp, tissue paper, poly, nonwoven web, acquisition, and elastic, although application specific materials are sometimes utilized. Usually, most of the insert raw materials are provided in roll form, and unwound and applied in assembly line fashion. 
         [0004]    In the creation of a diaper, multiple roll-fed web processes are typically utilized. To create an absorbent insert, the cellulose pulp is unwound from the provided raw material roll and pulverized by a pulp mill. Discrete pulp cores are formed by a core forming assembly and placed on a continuous tissue web. Optionally, super-absorbent powder may be added to the pulp core. The tissue web is wrapped around the pulp core. The wrapped core is debulked by proceeding through a calender unit, which at least partially compresses the core, thereby increasing its density and structural integrity. After debulking, the tissue-wrapped core is passed through a segregation or knife unit, where individual wrapped cores are cut. The cut cores are conveyed, at the proper pitch, or spacing, to a boundary compression unit. 
         [0005]    While the insert cores are being formed, other insert components are being prepared to be presented to the boundary compression unit. For instance, the poly sheet is prepared to receive a cut core. Like the cellulose pulp, poly sheet material is usually provided in roll form. The poly sheet is fed through a splicer and accumulator, coated with an adhesive in a predetermined pattern, and then presented to the boundary compression unit. In addition to the poly sheet, which may form the bottom of the insert, a two-ply top sheet may also be formed in parallel to the core formation. Representative plies are an acquisition web material and a nonwoven web material, both of which are fed from material rolls, through a splicer and accumulator. The plies are coated with adhesive, adhered together, cut to size, and presented to the boundary compression unit. Therefore, at the boundary compression unit, three components are provided for assembly: the poly bottom sheet, the core, and the two-ply top sheet. 
         [0006]    A representative boundary compression unit includes a die roller and a platen roller. When all three insert components are provided to the boundary compression unit, the nip of the rollers properly compresses the boundary of the insert. Thus, provided at the output of the boundary compression unit is a string of interconnected diaper inserts. The diaper inserts are then separated by an insert knife assembly and properly oriented. At this point, the completed insert is ready for placement on a diaper chassis. 
         [0007]    A representative diaper chassis comprises nonwoven web material and support structure. The diaper support structure is generally elastic and may include leg elastic, waistband elastic and belly band elastic. The support structure is usually sandwiched between layers of the nonwoven web material, which is fed from material rolls, through splicers and accumulators. The chassis may also be provided with several patches, besides the absorbent insert. Representative patches include adhesive tape tabs and resealable closures. 
         [0008]    The process utilizes two main carrier webs; a nonwoven web which forms an inner liner web, and an outer web that forms an outwardly facing layer in the finished diaper. In a representative chassis process, the nonwoven web is slit at a slitter station by rotary knives along three lines, thereby forming four webs. One of the lines is on approximately the centerline of the web and the other two lines are parallel to and spaced a short distance from the centerline. The spaced effect of such slicing is twofold; first, to separate the nonwoven web into two inner diaper liners. One liner will become the inside of the front of the diaper, and the second liner will become the inside of the back of that garment. Second, two separate, relatively narrow strips are formed that may be subsequently used to cover and entrap portions of the leg-hole elastics. The strips can be separated physically by an angularly disposed spreader roll and aligned laterally with their downstream target positions on the inner edges of the formed liners. 
         [0009]    After the nonwoven web is sliced, an adhesive is applied to the liners in a predetermined pattern in preparation to receive leghole-elastic. The leg-hole elastic is applied to the liners and then covered with the narrow strips previously separated from the nonwoven web. Adhesive is applied to the outer web, which is then combined with the assembled inner webs having elastic thereon, thereby forming the diaper chassis. Next, after the elastic members have been sandwiched between the inner and outer webs, an adhesive is applied to the chassis. The chassis is now to receive an insert. 
         [0010]    To assemble the final diaper product, the insert must be combined with the chassis. The placement of the insert onto the chassis occurs on a placement drum or at a patch applicator. The inserts are provided to the chassis on the placement drum at a desired pitch or spacing. The generally flat chassis/insert combination is then folded so that the inner webs face each other, and the combination is trimmed. A sealer bonds the webs at appropriate locations prior to individual diapers being cut from the folded and sealed webs. 
         [0011]    The current practice in applying a stretchable web such as a poly web to a second web is involved continuously feeding the poly web into the process which results in poly running full length of product, or alternatively, full length of a constructed insert core which is then placed onto a nonwoven-type chassis. Not all machine configurations can be adapted from a full length poly chassis to a poly insert configuration due to space and/or cost restrictions. It should be understood that application of the poly web along the entire length of the product, rather than only where it is useful, increases the amount of poly material which must be utilized. This is a waste of the material resource and adds additional cost to the product. It is therefore desirable to create a lower cost product by putting poly into the product only where it is useful, instead of the complete product. 
         [0012]    However, typical slip/cut application of poly patch to a continuous web does not work well because of the elasticity of the poly web. The slip/cut process allows the poly to slip on anvil prior to being cut causing the poly to violently snap back at the moment of cut. This can result in a short patch-long patch output from the slip/cut where one or more of the resulting poly catches are extremely distorted on the carrier web. 
         [0013]    In certain instances, it is desirable to eliminate or minimize the use of adhesives in the manufacturing process. This results in a material savings. Also, it is desirable to reduce significant strains applied to elongated elastics that are held under significant strain of 50-400%. At this level of elongation, there is a lot of stress on the elastic and the elastic has an increased likelihood of breaking, which can lead to machine downtime. 
         [0014]    In prior art systems, such as U.S. Pat. 6,291,039, it is known to capture elastics between layers of nonwoven materials. For instance, as taught therein, elastics can be placed into a hem of nonwoven material, and when the nonwoven material is bonded onto itself at the hem, the elastic can be captured within the folded over layer of material. 
         [0015]    In U.S. Pat. No. 7,642,398 an elasticized web has a gatherable substrate and a multi-strand elastic yarn affixed to the gatherable substrate at a plurality of fixation locations. So that the yarn can be affixed to the substrate without the use of an adhesive, the yarn is subjected to forces to create partial delamination of the yarn at the fixation locations and a portion of the gatherable substrate is caused to pass between the thus delaminated strands of the multi-strand elastic yarn. A patterned surface is disclosed in which the distribution density of raised heels varies over the surface area of the patterned surface. The patterned surface comprises one or more regions along the length of the yarn in which no raised heels are present, so that the elasticized web produced using this patterned surface will have regions along the length of the elastic yarn at which no bonds are present. Accordingly, the elastic yarn will be able to move independently of the substrate or substrates in such regions. 
       SUMMARY OF THE INVENTION 
       [0016]    One aspect of the invention is a method including providing a base non-woven layer, and applying thereto an elastic strand, strip or web. Throughout the specification, nonwoven webs are referred to. The references to nonwoven webs should be considered to extend to bondable webs generally, but alternative web materials are considered within the scope the invention. Examples of bondable webs which could be used in the present invention when nonwovens are referred to, are any film webs, including polypropylene or polyethylene. Commonly elastics are applied under elongation/tension to carrier webs. In the present invention, non-elongated elastics, or elastics at low tension, are provided to a carrier web. In one embodiment, the carrier web is accumulated in valleys and the elastic is bonded to the carrier web at peaks. Such bonding could be done with, but not limited to, adhesives, ultrasonics, or pressure. After bonding, the carrier web is returned to its unaccumulated state thereby elongating the elastic(s) in the process. A simple relationship between the amount of material accumulated and the distance between bond sites determines the final elongation, or strain, of the elastic(s). 
         [0017]    In another embodiment of the present invention, elastic filaments can be separated from one another through ultrasonic force, electrostatic separation, or tension on the elastic yarn. With an electrostatic charge on the elastic filaments, the filaments separate and the filaments and nonwoven layer bond with minimal severing of the filaments. 
         [0018]    In another aspect of the present invention, elastics are captured within layers of nonwoven materials, with the elastics laid down and captured between the nonwoven layers in a meandering pattern between bond points of nonwoven materials of the laminate. In this configuration, differently shaped and configured pins or protrusions on a roll or drum can urge the elastics to meander between bond points. In other words, the elastics can be trained to run straight, curved, meandering, or any combination of those lay down patterns, and then retained in that laydown position due to friction between the elastic material and the nonwoven material, particularly if the elastics are meandering through non-linear bond points. 
         [0019]    Several pin and protrusion configurations (oblong, curved, rectangular, circular) can be used in different patterns on a rotating drum, such as variably spaced patterns, offset patterns, curved patterns or the like, to establish a complex pattern of elastics meandering through bond points in the nonwoven layers capturing the elastics, and the friction between the elastic and the material retains the elastic sufficiently in place to minimized adhesive bonding between the elastics and the nonwoven required to create the laminate. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0020]      FIG. 1  is a side view of an apparatus and method of forming an elastic laminate; 
           [0021]      FIG. 2  is a side view of an elastic laminate with an unstretched elastic and a slack base layer; 
           [0022]      FIG. 3   a  is a side view of an elastic laminate with a tensioned elastic layer and a stretched or tensioned base layer; 
           [0023]      FIG. 3   b  is a side view of an elastic laminate with a tensioned elastic layer and a stretched or tensioned base layer, and a second material layer coupled to the elastic layer; 
           [0024]      FIG. 4   a  is a side view of an elastic laminate with a tensioned elastic layer and a stretched or tensioned base layer, and a second material layer coupled to the base layer (or first material layer) at discrete bond points, with the elastic layer positioned between the first and second material layers; 
           [0025]      FIG. 4   b  is a side view of an alternate embodiment of the present invention, with pins (or anvil bond points) placed about an anvil roll and carrying the first material layer, and elastic strands laid atop the first non-woven layer tented by the pins, with a second material layer laid over the elastic strands and first material layer, and trilaminate bonded together and passed downstream for further processing; 
           [0026]      FIG. 4   c  is a perspective view of the machine of  FIG. 4   b,  with elastic strands laid down atop the first material layer, and the elastic strands allowed to or encouraged to wander about the anvil bond points to be laid down and the first and second layers bonded at the bond points to secure the elastics therebetween in meandering fashion; 
           [0027]      FIG. 4   d  is a side view of a machine for joining the elastic and first material layer at bond points, bringing first material layer to a taut condition, and bonding a second material layer to the laminate during a second bonding operation; 
           [0028]      FIG. 5  is a side view of the unit of  FIG. 4   c,  showing the trilaminate formation, with the meandering elastics trapped between the bond points of the first and second layers; 
           [0029]      FIG. 6  is an alternate embodiment of the pinned anvil arrangement, with slots provided about the anvil. 
           [0030]      FIG. 7  is an alternate anvil bond point configuration; 
           [0031]      FIG. 8  is a second alternate anvil bond point configuration encouraging circuitous path of the elastic strands about the anvil bond points, the spaces between the anvil bond points (where the first and second material layers will become bonded, creating short tunnels to encourage the lacing action of the elastics between these tunnels to limit creep); 
           [0032]      FIG. 9  is a third alternate anvil bond point configuration; 
           [0033]      FIG. 10  is a perspective view of elastic material contained in a single material hem; 
           [0034]      FIG. 11  is a perspective view of elastic material contained between two materials to create a trilaminate; 
           [0035]      FIG. 12  is a fourth alternate anvil bond point configuration; 
           [0036]      FIG. 13  is a fifth alternate anvil bond point configuration. 
       
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT  
       [0037]    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. 
         [0038]    It is noted that the present techniques and apparatus are described herein with respect to products such as diapers, but as previously mentioned, can be applied to a wide variety of processes in which discrete components are applied sequentially. 
         [0039]    Referring now to  FIG. 1 , a side view of an apparatus and method of forming an elastic laminate is shown. A base support structure  18  is provided with peaks and valleys, which can be a “V” shape. A preferably non-woven layer  12  is laid into the valleys. Atop the nonwoven  12  is laid an unstretched or relatively unstretched elastic layer  14 , which can comprise strands or a web of elastic. This elastic  14  is bonded to the non-woven layer  12  at bond points  16 . Such bonding could be done with, but not limited to, adhesives, ultrasonics, or pressure. 
         [0040]      FIG. 2  is a side view of an elastic laminate with an unstretched elastic  14 , and a slack base layer  12 , shown just after bonding the two layers together. 
         [0041]    After bonding, the carrier web  12  is returned to its unaccumulated state thereby elongating the elastic(s)  14  in the process, as shown in  FIG. 3   a.  If considered mathematically, a relationship between the amount of material, accumulated within the valleys, and the distance between the peaks determines the final elongation or strain ∈( ) of the elastics. Twice the distance from peak to valley, divided by the distance between peaks, defines ∈) ( of the elastics. Put another way, twice the distance from peak to valley will measure the distance between bond points of nonwoven  12  in a non-accumulated state. 
         [0042]    If desired, as shown in  FIG. 3   b,  a second material layer  20  (preferably nonwoven) can be coupled to the elastic  14 , or in an alternate configuration, coupled to the first material layer ( FIG. 4   a ). 
         [0043]    In an alternative embodiment of the present invention as shown in  FIG. 4   b.  The forming technique described with reference to  FIG. 4   a  is shown in side view in  FIG. 4   b.  Pins or protrusions or anvil bond points  52  are placed about an anvil roll  50 , and elastic strands  14  laid atop a nonwoven layer  12  tented by the pins  52 . Adjacent tented nonwoven  12  peaks create somewhat of a tunnel when coupled with top nonwoven  12 , and elastic  14  is carried in the tunnel in circuitous or meandering ways as shown in  FIG. 4   c.  The result is that the elastic  14  is restrained from lateral (or cross-machine direction) movement by encountering bond points between the first and second material layers  12  and  20  respectively, created by points  52  acting against ultrasonic horn  54 . Alternatively, adhesives can be used in            
         [0044]    Still referring to  FIG. 4   c,  and also to  FIG. 5 , protrusions  52  on an anvil roll  50  carry nonwoven  12 , and create a tenting effect by raising the portions of the nonwoven  12  carried by the protrusions  52 . It is between and about these adjacent and downstream bond points that the elastic  14  is allowed to, or encouraged to, meander generally in the machine direction as opposed to traveling linearly in the machine direction. Elastic  14  is laid down with tension in a circuitous path over and about the protrusions  52 . The elastic  14  forces the nonwoven  12  down around protrusions  52  and the protrusions  52  are used to ultrasonically bond a second, top nonwoven layer  12  to the first nonwoven  12 . The elastic  14  experiences a fairly high frictional force against the bonded segments of the nonwoven layers  12  because of the serpentine (meandering) path of the elastic  14  about the bond points and against the material layers  12  and  20  themselves, keeping the elastic  14  from creeping. 
         [0045]    Referring now to  FIG. 4   d,  a forming technique described with reference to  FIG. 3   b  is shown in side view in  FIG. 4 . In particular, after joining initially relaxed elastic  14  and initially relaxed first material layer  12  at bond points  16  by bonding unit  54 , first material layer  12  and elastic layer  14  can be brought taut by elongating elastic  14 . After first material layer  12  is sufficiently taut, second material layer  20  (preferably non woven) is introduced to the laminate  12 / 14 , and a second bonding operation occurs between material layer  20  and laminate  12 / 14 . This bonding can be performed by adhesive (not shown) or by an ultrasonic horn  54  operating against drum  70 . 
         [0046]    Referring now to  FIG. 6 , an alternate embodiment of the pinned anvil arrangement of  FIGS. 4 and 5  is shown, with slots  54  provided about the anvil roll  50 . First nonwoven layer  12 , and atop that layer, the elastic  14  is laid down in slots  54 , and a top nonwoven layer  12  is laid down and bonded to first nonwoven layer  12 . This creates a tunnel, of nonwoven, and the tight elastic  14  is resistant to creeping as described previously. 
         [0047]    In addition to the techniques described above, modifications to the physical properties of the elastic  14  can assist providing the desired frictional resistance between the elastic  14  and nonwoven  12 . For instance, ultrasonic force applied to the strands can cause the strands to unravel; those unraveled ends would choke any created tunnels in the nonwoven. Alternatively or additionally, the nonwoven layers  12  could be bonded through the unraveled strands  14 , or could be unraveled without bonding. 
         [0048]    Still alternatively or additionally, a polymer coating such as Ethylene Vinyl Acetate (EVA) could be intermittently applied on the stretched elastic strands  14 , to create rings or collars of eventually solidified polymer. The eventually solidified polymer on the elastic strands  14  would provide a physical barrier on created or improvised tunnels and might even get bonded into the nonwoven bonds that form the tunnel. 
         [0049]    Still alternatively or additionally, two or more elastic strands  14 , can be twisted together, those entwined fibers  14  also physically resist travel through the created tunnels as the elastic  14  tries to relax. Additionally, a single elastic strand  14  can be rolled to make a bulky twisted structure that resists creep through the tunnel more effectively than elastic  14  that is simply stretched. Alternatively or additionally, the elastic  14  can be frayed or nicked with a rough surface such as sandpaper; it may pull the individual fibers apart, or roughen the surface to fatten it up. 
         [0050]    Referring now to  FIG. 7 , an alternate anvil bond point  52  configuration is shown. Bond points  52  are spaced apart in the machine direction by spacing y, and spaced apart in the cross-machine direction by spacing x. X and y can both vary and be variable between adjacent bond points  52 . That is, the points can be closely spaced apart in the cross-machine or machine directions, or more distantly spaced apart, and the spacing can vary from one row to the next, and from one column to the next. 
         [0051]    For instance, as shown in a second alternate anvil bond point configuration of  FIG. 8 , the bond points  52  can be spaced to encourage a circuitous path of the elastic strands  14  about the anvil bond points (noting that in a preferred embodiment that a nonwoven will be draped over the bond points  52  and the nonwoven is not shown in  FIG. 8 ). In this configuration, a cross machine direction spacing x′ offset is provided in a column of bond points  52 . The spaces between the anvil bond points  52  (where the first and second material layers  12  and  20  will become bonded) creating short tunnels to encourage the lacing action of the elastics  14  between these tunnels to limit creep. 
         [0052]    Referring to  FIG. 9 , third alternate anvil bond point  52  configuration varies machine direction spacing y′, y″ and y″ by an offset provided between adjacent rows of bond points  52 . As such, both y and x can be varied to encourage tunnel formation and encourage meandering elastics  14 . Alternatively as shown in  FIG. 9 , the protrusions can be staggered such that protrusions of a first series of adjacent rows are not staggered in the cross machine direction. This would encourage a straight run of elastics (at the to of  FIG. 9 ), and downstream in the machine direction, a second series of adjacent rows can be staggered or offset by a distance x′ to encourage a curved run (middle portion of  FIG. 9 ), or the staggering of x′ and y′ can be more random resulting in a meandering pattern of elastics  14 . 
         [0053]    Referring now to  FIG. 10  elastic material  14  can be used in the present invention by single material hem of material  12 . In this manner, the meandered elastic will be captured between a laminate of the first material  12  portions after folding over an outboard portion of web  12 , for instance by a folding plow (not shown). 
         [0054]    Referring now to  FIG. 11 , a perspective view of elastic material  14  contained between two materials  12  and  14  to create a trilaminate is shown. As can be seen, the elastic  14  meanders around bond points between material layers  12  and  14 . 
         [0055]    Referring now to  FIG. 12  is a fourth alternate anvil bond point configuration is shown. A series of curved protrusions  56  can be used instead of or in addition to pins or protrusions  52  placed about an anvil roll  50  shown on  FIGS. 4 and 5 . In this embodiment, material layer  12  is introduced atop the roll  50 , and carried in part by curved protrusions  56 . Material layer  12  will somewhat drape over and about protrusions  56  to create channels encouraging elastic  14  to he laid down in a somewhat meandering pattern, such that when material layers  12  and  20  are bonded. (see, e.g.,  FIG. 4   a ), the bond points between material layers  12  and  20  will result in friction between elastic  14  meandering through the bond points of material layers  12  and  20 . This friction prevents elastic  14  from sliding or creeping, i.e, elastic  14  is generally retained by frictional forces in its laid down meandering pattern. 
         [0056]    Referring now to  FIG. 13 , shaped protrusions  58 , generally having preferably rounded corners to prevent material defects as a result of machine processing can be used. The shape of protrusions  58  can be changed, with the spacing between shapes, and the shapes of the protrusions  58  themselves changed to accommodate the creation of frictional holding forces between elastic  14  and material layers  12  and  20 , specifically between elastic  11  and bonding points between material layers  12  and  20  which elastic  14  is sandwiched between. This configuration shows a larger surface area bond point, and a patterned profile of protrusions  52  is used to provide increased frictional resistance between elastic  14 , the surrounding layers  12  and  20  and their bond points. In essence, a maze is provided for the elastic  14  to go through during manufacture, and rounded corners of protrusions  52  can urge the elastic  14  to be laid down in those maze patterns during the elastic laydown and bonding processes previously described. 
         [0057]    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.