Abstract:
A method of manufacturing a fastener product includes continuously introducing a sheet of preformed material to a gap defined adjacent a peripheral surface of a rotating mold roll. A lane of resin is also introduced into the gap with the lane overlapping a longitudinal edge of the sheet. The resin is pressed against the sheet in the gap, such that the resin becomes permanently bonded to the sheet, while an array of stems is molded from the resin in the thicker region, the stems extending from a base portion of the resin. Engageable heads are formed on the stems to form fastener elements. The gap is configured with a step in thickness, the step defining a boundary between a relatively thicker gap region and a relatively thinner gap region, the sheet of preformed material being introduced to the gap with its longitudinal edge disposed within the thicker gap region.

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS  
       [0001]     This application claims the benefit prior U.S. Provisional Application No. 60/677,992, filed May 5, 2005, which is incorporated herein by reference in its entirety. 
     
    
     TECHNICAL FIELD  
       [0002]     This invention relates to molding fastener stems onto substrate.  
       BACKGROUND  
       [0003]     Molding apparatus used to produce touch fastener products have been described in U.S. Pat. No. 4,872,243 issued to Fischer and U.S. Pat. No. 5,260,015 issued to Kennedy, et al. (“Kennedy”), the entire contents of both of which are incorporated herein by reference. Such molding apparatus introduce moldable resin into a gap adjacent a mold roll. Moldable resin can be, but is not necessarily in a molten state. Pressure is applied in the gap to force resin from the gap into mold cavities defined in the mold roll to form touch fasteners. Kennedy further describes introducing the resin into the gap between a preformed sheet material and the mold roll and bonding the resin to the preformed sheet material in the gap.  
       SUMMARY  
       [0004]     In one aspect of the invention, a method of manufacturing a fastener product includes continuously introducing a sheet of preformed material to a gap defined adjacent a peripheral surface of a rotating mold roll; introducing a lane of moldable resin into the gap such that the lane of resin overlaps a longitudinal edge of the sheet; pressing the lane of moldable resin against the sheet in the gap, such that the resin becomes permanently bonded to the sheet in the overlapped region, while molding an array of stems from the resin in the thicker region, the stems extending from a base portion of the resin; and forming engageable heads on the stems to form fastener elements. The gap is configured with a step in thickness, the step defining a boundary between a relatively thicker gap region and a relatively thinner gap region, the sheet of preformed material being introduced to the gap with its longitudinal edge disposed within the thicker gap region.  
         [0005]     In another aspect of the invention, a method of manufacturing a fastener product, the method includes continuously introducing two sheets of preformed material to a gap defined adjacent a peripheral surface of a rotating mold roll, the sheets of preformed material positioned with an interval between them, introducing a lane of moldable resin into the gap such that the lane of resin overlaps longitudinal edges of the sheets adjacent the interval, the lane of moldable resin having a thinner region overlapping the sheets and a thicker region substantially aligned with the interval; pressing the lane of moldable resin against the sheets in the gap, such that the resin becomes permanently bonded to the sheets in the overlapped region, while molding an array of stems from the resin in the thicker region, the stems extending from a base portion of the resin; and forming engageable heads on the stems to form fastener elements.  
         [0006]     In another aspect of the invention, a method of manufacturing a fastener product includes continuously introducing a sheet of preformed material to a gap defined adjacent a peripheral surface of a rotating mold roll; introducing a lane of moldable resin into the gap such that the lane of resin overlaps a longitudinal edge of the sheet, the lane of moldable resin having, as introduced to the gap, a relatively thinner region overlapping the sheet and a relatively thicker region extending beyond the sheet; pressing the lane of moldable resin against the sheet in the gap, such that the resin becomes permanently bonded to the sheet in the overlapped region, while molding an array of stems from the resin in the thicker region, the stems extending from a base portion of the resin; and forming engageable heads on the stems to form fastener elements.  
         [0007]     In some embodiments, the gap is defined between the mold roll and a counter-rotating pressure roll.  
         [0008]     In some embodiments, the step in thickness corresponds to a change in diameter of the pressure roll and/or a change in diameter of the mold roll.  
         [0009]     In some embodiments, the longitudinal edge of the sheet is defined by a longitudinal fold in the sheet.  
         [0010]     In some embodiments, forming engageable heads comprises molding tapered ends on the stems to form loop-engageable hooks. In some alternate embodiments, forming engageable heads comprises applying heat and pressure to compress distal ends of the stems.  
         [0011]     In some embodiments, the preformed material is a non-woven fabric, for example, a polyolefin non-woven fabric.  
         [0012]     In some embodiments, the thickness of the preformed material is between about 0.001 inch and 0.25 inch in the nip.  
         [0013]     In some embodiments, the thickness of the base portion is between about 0.001 inch and 0.25 inch (e.g. between about 0.025 inch and 0.25 inch, between about 0.05 inch and 0.15 inch, 0.015 inch and 0.10 inch).  
         [0014]     In some embodiments, the lane of moldable resin comprises a first resin and a second resin. For example, in some fastener products, the array of stems is molded predominantly from a first resin and the base portion is formed predominantly from a second resin. In another example, in some fastener products, the second resin has a flexural modulus that less than half of a flexural modulus of the first resin. In some cases, the flexural modulus of the first resin is at least 100,000 pounds per square inch.  
         [0015]     In some fastener products, the first resin and the second resin are attached to each other but substantially distinct in a region not overlapped. For example, in some cases, the lane of moldable resin has at least one longitudinal bead of the first resin disposed on a web of the second resin. In some cases, the lane of moldable resin includes polypropylene. In some cases, the base portion and fastener elements are translucent.  
         [0016]     In some embodiments with an interval, the interval is at least 0.5 inch wide (e.g. at least 1 inch wide, at least 1.5 inch wide, at least 3 inches wide, at least 6 inches wide).  
         [0017]     In some embodiments, the stems extend from opposing faces of the base portion of the resin.  
         [0018]     It has been discovered that use of a vertical spacer in the gap adjacent a mold roll can function to help regulate the height of the gap and pressure applied in the gap, thus advantageously protecting soft substrates, protecting substances embedded in the resin, and/or allowing the formation of thicker resin bases while still providing sufficient pressure to force the moldable resin into the mold cavities for fastener formation.  
         [0019]     The details of one or more embodiments of the invention are set forth in the accompanying drawings and the description below. Other features, objects, and advantages of the invention will be apparent from the description and drawings, and from the claims. 
     
    
     DESCRIPTION OF DRAWINGS  
       [0020]      FIG. 1  is a perspective view of a diaper with fastener tabs.  
         [0021]      FIG. 1A  is plan view of fastener tab engagement.  
         [0022]      FIG. 2  is a diagrammatic view of an apparatus for producing fastener tabs as shown in  FIGS. 1 and 1 A.  
         [0023]      FIG. 2A  is a cross-sectional view taken along A-A in  FIG. 2  of a nip with a mold-roll acting as a vertical spacer.  
         [0024]      FIG. 3  is alternate apparatus for continuous production of a fastener product with a single substrate acting as a vertical spacer.  
         [0025]      FIG. 3A  is a cross-sectional view of the extrusion die taken along A-A in  FIG. 3 .  
         [0026]      FIGS. 3B  is a cross-sectional view taken along B-B in  FIG. 3  and  FIG. 3C  is more detailed view of region C noted on  FIG. 3B .  
         [0027]      FIG. 3D  is a cross-sectional view of the resulting fastener product taken along D-D in  FIG. 3 .  
         [0028]      FIGS. 4A-4B  are, respectively, cross-sectional views of the nip of an alternate apparatus with two substrates acting as vertical spacers and an associated extrusion die.  
         [0029]      FIG. 4C  is a cross-sectional view of the resulting fastener product.  
         [0030]      FIG. 4D  is a cross-sectional of the nip of an alternate embodiment of the apparatus.  
         [0031]      FIG. 5A  is a cross-sectional view of an apparatus with a stepped pressure roll acting as a vertical spacer.  
         [0032]      FIGS. 5B and 5C  are, respectively, cross-sectional views of an alternate embodiment of a stepped pressure roll and the resulting fastener product.  
         [0033]      FIG. 6  is a schematic view of an apparatus for producing a fastener product using multiple resins.  
         [0034]      FIGS. 7A and 7B  are cross-sectional views of the nip of alternate embodiments of the apparatus shown in  FIG. 6 . 
     
    
       [0035]     Like reference symbols in the various drawings indicate like elements.  
       DETAILED DESCRIPTION  
       [0036]     Touch fasteners are useful in many applications. For example, referring to  FIGS. 1 and 1 A, a diaper  10  is closed using touch fasteners tabs  12  with male fastener elements  14  to engage loop material  16  mounted on the diaper. For purposes of illustration, the size of the male fastener elements  14  is exaggerated. The fastener tabs  12  are formed with a substrate  18  bonded to a resin base  20  from which the male fastener elements  14  extend. Bonding the substrate  18  to the resin base  20  only at a discrete central region  22  is believed to provide increased fastening strength. Without wishing to be bound by theory, it is anticipated that a disengagement force F applied to grasping tab  24  will primarily result in shear, rather than peel, force being applied to the engagement between the male fastener elements  14  and the loop material  16 . This helps prevent inadvertent release of a fastener product (e.g. by a toddler playing with a diaper fastener tab or by a patient catching the edge of a splint on the edge of a piece of furniture).  
         [0037]     Referring to  FIG. 2 , it has been discovered that such fastener products can be efficiently produced in a molding apparatus  26  and that use of a vertical spacer in the gap  28  adjacent a mold roll  30  can help regulate the height of the gap and the pressure applied in the gap, thus advantageously protecting soft substrates and/or allowing the formation of thicker resin bases while still providing sufficient pressure to force the moldable resin into the mold cavities  56  for fastener formation. In this apparatus  26 , the gap  28  is a nip defined between the mold roll  30  and a counter-rotating pressure roll  32 . Referring to  FIG. 2A , the mold roll  30  is assembled from multiple tool rings  34  and spacer rings  36  in a tooling region  38  and spacer rings in end regions  40  on either side of the tooling region. In this case, the spacer rings  36  in the end regions  40  are also used as vertical spacers that provide a mechanical limit helping control the height h of the nip  28  and the amount of pressure applied to the resin and thus to the folded substrate  18 . Because the mold roll  30  and pressure roll  32  are in close proximity if not in actual contact, the spacer rings in end regions  40  comprise an engineering elastomer, at least on their outer surfaces, to limit damage to the rolls  30 ,  32  due to contact between the rolls. However, as is discussed below, the substrate  18  and/or portions of the mold roll can also be used as a vertical spacer.  
         [0038]     The substrate  18  proceeds from a feed roll  42  through folding station  44  to pressure roll  32  where it is received in a channel  46  defined in the pressure roll  32  that conveys it into the nip  28  in the folded configuration provided by the folding station. An extruder  48  discharges a molten resin web  50  into the nip  28 . A portion of the folded substrate  18  is exposed to contact the resin web  50 . The substrate  18  is chosen to be physically and/or compositionally compatible with the resin in order to bond with the resin base  20  forming the central bonding region  22  ( FIG. 1A ). Examples of possible substrates include woven and non-woven fabrics, paper, plastics, and rubber.  
         [0039]     Pressure applied in the nip causes the molten resin to enter mold cavities  56 , defined by the tool rings  34 , which are configured to mold the molten resin into desired shapes (e.g. hooks with loop-engageable heads). For purposes of illustration, the size of the mold cavities is exaggerated and the number of mold cavities and associated tool and spacer rings is reduced in all of the Figures showing mold cavities. All of the mold rolls are assembled of tool and spacer rings although individual rings are only shown in  FIG. 2A .  
         [0040]     The mold roll  30  is temperature controlled to solidify the molten resin as a base  20  and molded hooks  14  extending from the base. The hooks  14 , resin base  20 , and attached substrate  18  are stripped from the mold roll  30  by tension applied at stripping roll  52 . The resulting fastener product is gathered on storage roll  54 . Optional unfolding station  55  may be included to unfold the substrate to make roll storage more efficient. Similarly, optional cutter  57  may be provided to separate portions of the fastener product from each other (e.g. slice a wide multiple lane product into discrete narrower strips).  
         [0041]     In an alternate embodiment of the apparatus, the mold cavities  56  are configured to form the male fastener elements  14  as stems whose loop-engageable heads are formed by post-processing after the stems are stripped from the mold roll  30 . For example in such an alternate embodiment, an optional radiant heater  58  and heading rolls  60  are added to the apparatus with the radiant heater  58  softening the stems  14  before heading rolls  60  deform the ends of the stems to form loop-engageable heads.  
         [0042]     Referring to  FIG. 3 , a similar apparatus for forming fastener products uses a substantially rigid substrate  18  as a vertical spacer. Referring to  FIG. 3A , the extruder  48  has a die lip  62  which shapes the extruded resin web to form a relatively thin portion  50 A and relatively thick portion  50 B. Referring to  FIGS. 3B and 3C , the resin web  50  is fed into the nip  28  with the thin portion  50 A aligned to overlap the substrate  18  in an overlap region  64  with the resin between the substrate and the mold roll  30 . The thick portion  50 B of the resin web abuts the substrate  18  and is aligned with the mold cavities  56  of the mold roll  30 . This distribution of the resin is thought to enhance both bonding of the resin with the substrate and filling of the mold cavities by the resin. The distribution of resin is predominantly influenced by characteristics and operating parameters of the extruder  48  particularly the shape of the die lip  62 . However, the shape of the resin web does not exactly match the desired resin distribution and so is often adjusted during machine design and setup to achieve the desired distribution.  
         [0043]     Other resin-substrate configurations can be used with this apparatus. For example, referring to  FIGS. 4A-4C , this apparatus can also be used with two strips of substrate  18  bracketing a lane  66  of resin. This approach provides more balanced support internal to the nip  28 . The extruder  48  has a die lip  62  that provides the desired resin distribution to produce a lane of fastener elements  14  between two lines of substrate. In a further variation, the pressure roll  32  can be replaced with a second mold roll  30  to produce fastener products with fastener elements extending from opposing faces. The exemplary embodiment illustrated in  FIG. 4D  uses a substrate with porosity such that resin in the overlap regions  64  penetrates into the substrate rather than remaining on its surface. Moreover, in addition to being compatible with the substrate  18 , the resin can be a translucent resin chosen to provide visibility of designs through the resin strip.  
         [0044]     Referring again to  FIG. 3A , using molding apparatus with a machine width MW of 12 inches allows production of single strip of fastener product whose total width TW (i.e. the combined width of the substrate  18  and the attached resin strip  20 ) approximates that of the machine width. However, such a molding apparatus also allows production of multiple narrower substrate-resin strips (e.g. five strips of fastener products each with a total width TW of 2 inches). Typically, multiple strips are produced with sides of adjacent strips abutting and attached to each other in a combined strip which is cut or separated during post-processing to produce the individual strips. Molding apparatuses are available with varying machine widths.  
         [0045]     The substrate chosen for use with this apparatus should be substantially rigid. In other words, the substrate  18  should be sufficiently incompressible (or compressible to a rigid form) to help regulate the height h of the gap  28 . However, the substrate should be compressible enough to give slightly in the overlap region to provide space between the mold roll  30  and the substrate  18  to receive the resin predominantly on the surface of the substrate ( FIGS. 3B-3C ). Alternate substrates  18  are porous enough to receive the resin within internal voids ( FIG. 4D ). For example, typical spun-bound non-woven fabrics have been found to possess appropriate porosities for this purpose. In some embodiments, an incompressible substrate is machined to a reduced thickness in the overlap region  64  in order to receive the resin and/or a shallow recess can be provided in the mold roll  30  aligned with the overlap region  64 .  
         [0046]     However, in some instances, it is not feasible to use the substrate as a vertical spacer. For example, it is sometimes useful to make a fastener product with a ‘soft’ substrate that is too compressible to function as a vertical spacer. Such substrates may be desirable because they provide, for example, a skin-friendly surface for applications where the fastener product may come in contact with a user&#39;s skin (e.g. medical wraps such as elastic bandages used for wrapping injured joints). In another example, it may be desirable to use a thin substrate or no substrate while embedding an object in the resin passing through the nip that may be damaged by pressure applied in the nip or by contact with mold roll if the height of the resin strip is not tall enough.  
         [0047]     Referring to  FIGS. 5A-5C , a molding apparatus for such applications uses a step  68  in the pressure roll  32 A,  32 B as a vertical spacer. As in the molding apparatuses described above, moldable resin is fed into a calender nip with a substrate. In this case, the substrate is a soft substrate  18 B. However, the substrate is protected from excessive compression by step  68  in pressure roll  32 A. Referring to  FIG. 5A , the illustrated single step pressure roll  32 A produces a fastener product with a resin base approximately twice as thick as attached substrate  18 B. By feeding the substrate  18 B into the nip  28  in a folded configuration, wider fastener products can be produced on molding apparatus with a specific machine width than would be possible if the substrate was fed in flat. Referring to  FIGS. 5B and 5C , when a fastener product  13 C with a thinner resin base is desired, a pressure roll  32 B with two steps  68 ,  68 B is used.  
         [0048]     Because the mold roll  30  and pressure roll  32  are in close proximity if not in actual contact, the spacer rings (not shown individually) making up the mold roll  30  adjacent the step  68  comprise an engineering elastomer, at least on their outer surfaces, to limit damage to the rolls  30 ,  32  due to contact between the rolls. Other approaches to protecting the rolls  30 ,  32  from contact damage are possible, including, for example, by providing the pressure roll  32  with a protective coating in the vicinity of the step  68  or by recycling a strip of protective material to loop between the mold roll  30  and the pressure roll.  
         [0049]     Vertical spacers as described above are also useful in the formation of fastener products from two resins while minimizing mixing between the resins due pressure applied in the nip. Referring to  FIG. 6 , a molding apparatus similar to those discussed above has two extruders  48 A,  48 B feeding two resins  20 A,  20 B into the calender nip  28  with substrate  18 . In one example, referring to  FIG. 7A , a resin with a flexural modulus of greater than 50,000 pounds per square inch as measured in accordance with ASTM D790 (e.g. greater than 75,000 pounds per square inch, greater than 100,000 pounds per square inch) is chosen as first resin  20 A and a resin with a flexural modulus of less than 50,000 pounds per square inch (e.g. less than 25,000 pounds per square inch, less than 10,000 pounds per square inch) is chosen as second resin  20 B. In this example, the apparatus is used with a stepped mold roll and a rigid substrate as vertical spacers to form a fastener product  13 D with hooks made from a ‘tough’ resin extending from a resin base with an opposing face made from a relatively ‘softer’ resin is thought to help provide durable reusable hooks on a skin-friendly base. The resins  20 A,  20 B can be chosen for other desired properties (e.g. one could be hydrophilic and one hydrophobic) but the two resins should be compatible enough that passage through the nip together bonds them to each other as well as to any accompanying substrate  18 .  
         [0050]     In another example, using two substrate strips as the vertical spacers, first resin  20 A is fed into is  28  in discrete longitudinally extending beads between second resin  20 B and mold roll  30 . Although second resin  20 B fills in around first resin  20 A, the two resins  20 A and  20 B remain substantially distinct. If the two resins are present in the overlapped region  64 , it is anticipated that more mixing would occur. The substrates  18 , acting as vertical spacers, serve to help regulate nip height such that pressure applied in the nip  28  forces first resin  20 A into mold cavities  56  and laminates second resin  20 B to substrates  18  without mixing the resins to the point that they lose their distinct desired properties.  
         [0051]     A number of embodiments of the invention have been described. Nevertheless, it will be understood that various modifications may be made without departing from the spirit and scope of the invention. For example, the gap adjacent the mold roll could be defined between the mold roll and an extruder rather than between the mold roll and a pressure roll. Accordingly, other embodiments are within the scope of the following claims.