Abstract:
A bi-stable hook component of a touch fastener can bend into, and remain in, a stable concave position. Another stable position enables initial engagement with a mating component (e.g., a loop component). The concave position applies engagement-enhancing tension to the engaged loops, and in some cases forces end portions of the hooks into close proximity with one another to secure the fastening and to produce a curved touch fastener that, as engaged, can better conform to an underlying curved surface, such as the contour of a wearer&#39;s body. Absorbent articles having such a bi-stable fastening system are also disclosed.

Description:
TECHNICAL FIELD 
     This invention is directed to touch fastening, and particularly to bi-stable touch fasteners (e.g., hook and loop fasteners) and articles incorporating such fasteners. 
     BACKGROUND 
     A number of fastening systems, such as diaper fastening systems, incorporate a hook and loop system for easy fastening and release. The hook component typically includes a flat plastic sheet laminate with a number of protruding hooks that engage with a number of loops protruding from a corresponding loop component. The flat hook backing remains essentially flat while undergoing engagement with the corresponding loop component. Such hook and loop fastening systems rely primarily on shear forces that resist unfastening. The force of the user allows the hooks to engage into corresponding loops, with little dimensional change in either the hook component or the loop component. More particularly, the hook component and the loop component tend to remain flat, or bent only about a single axis, throughout the engagement process. 
     Since the shear forces resist unfastening of the hook and loop fastening system, hook and loop components are typically separated from one another using peel forces. However, with little resistance to the peel forces, the hook and loop fastening system is susceptible to coming unfastened at unexpected, and often undesirable, times. 
     There is a need or desire for a hook and loop fastening system with improved fastening security. 
     SUMMARY 
     The present invention is directed to a touch fastening system with improved fastening security. The improved fastening security is attributable to a design that utilizes the forces used to apply a product and the three-dimensional geometry of corresponding hook components and loop components. 
     According to one aspect of the invention, a touch fastener comprises a hook component and a loop component, with each of the hook and loop components having exposed elements on an active side thereof for releasable engagement with the exposed elements of the other component. The active side of one of the hook and loop components has a surface that bi-stabilizes between a first stable form for initiating engagement with the active side of the other of the hook and loop components, and a stable, concave form for securing an initiated engagement of the other of the hook and loop components. The other of the hook and loop components has a flexible backing adapted to conform to the concave form of the one of the hook and loop components during engagement. 
     In some embodiments, the bi-stabilizing surface is inherently either semi-spherical or semi-ellipsoidal in its stable concave form. 
     In presently preferred forms, the exposed elements of the hook component comprise hooks, each hook having a free end with an engageable head. Preferably, the heads of at least two adjacent hooks are farther apart from one another when the bi-stabilizing surface is in its first stable form than when the bi-stabilizing surface is in its stable, concave form. Ideally, the heads of at least two adjacent hooks contact one another when the bi-stabilizing surface is in its stable, concave form. 
     The exposed elements of the hook component comprise, for some applications, mushroom-shaped hooks. These mushroom-shaped hooks may have flat upper surfaces, for example. 
     In some cases the bi-stabilizing surface is of the hook component. 
     According to another aspect, a touch fastener comprises a hook component and a loop component, with each of the hook and loop components having exposed elements on an active side thereof for releasable engagement with the exposed elements of the other component. The active side of one of the hook and loop components has a surface that bi-stabilizes between a first stable form for initiating engagement with the active side of the other of the hook and loop components, and a stable, concave form for securing an initiated engagement of the other of the hook and loop components. The exposed elements of the hook component comprise hooks, and the heads of at least two adjacent hooks contact one another when the bi-stabilizing surface is in its stable, concave form, to secure engaged loop component elements. 
     According to another aspect, a touch fastener comprises a pair of releasably engageable components, each of the components having exposed elements on an active side thereof for releasable engagement with the exposed elements of the other component. The active side of one of the components comprising a surface that bi-stabilizes between a first stable form for initiating engagement with the active side of the other of the components, and a stable, concave form for securing an initiated engagement of the other of the components. The exposed elements of at least one of the components comprise mushroom-shaped hooks. 
     In some preferred instances, the exposed elements of one of the components comprise fibers exposed for engagement by the hooks. In other cases, the exposed elements of both of the components comprise arrays of self-engageable mushroom-shaped hooks. 
     The above-described touch fastener systems are employed to advantage in various articles. In one aspect of the invention, an absorbent article (e.g., a diaper, a feminine hygiene product, or an incontinence product) has the featured touch fastener arranged to secure the absorbent article. Preferably, the touch fastener is arranged to extend over an underlying, curved surface of a wearer&#39;s body with the bi-stabilizing surface in its stable, concave form, for conforming the touch fastener to the wearer. In other aspects of the invention, the fastener system is provided on a training pant or medical garment. 
     According to yet another aspect of the invention, a method of releasably securing an article over an underlying curved surface is provided. The method includes grasping one of a pair of touch fastener components secured to the article, the grasped component having an active side comprising a surface that bi-stabilizes between a first stable form for initiating engagement with an active side of the other of the pair of touch fastener components, and a stable, concave form for securing an initiated engagement of the other of the touch fastener components. With the surface of the grasped component in its first stable form, an active side of the other component is contacted with the active side of the grasped component. With the active sides of the components in contact, the bi-stabilizing surface of the grasped component is forced or made to toggle to its stable, concave form to secure the components in engagement and to conform the grasped touch fastener component to the underlying curved surface. 
     In some instances, the article comprises a garment (e.g., a diaper) and the underlying curved surface is of a wearer&#39;s body. 
     According to yet other aspects of the invention, methods are provided for forming the bi-stable fastener products as herein described. 
     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 
     FIG. 1 is a side view of the components of a touch fastener as they are brought into initial engagement with the bi-stable hook component in a stable convex form. 
     FIG. 2 is a side view of the touch fastener subsequent to full engagement, with the bi-stable hook component assuming its stable, concave form. 
     FIG. 3 is a side view of a touch fastener in a flat position, with a hook component engaged with a loop component. 
     FIGS. 4-6 correspond to FIGS. 1-3, respectively, but illustrating a second embodiment of hook fastener. 
     FIG. 7 is a side view of an individual, J-shaped hook of a hook component. 
     FIGS. 8 and 9 are side and front views, respectively, of an individual, mushroom-shaped hook having a head with a flat upper surface. 
     FIGS. 10 through 12 are top views of an array of mushroom-shaped hooks of a bi-stable hook component, with the hook component in flat, convex, and concave form, respectively. 
     FIG. 13 illustrates a bi-stable hook component during initial engagement with a loop component on a disposable diaper, with the hook component in a stable, convex position. 
     FIG. 14 shows the diaper fastener of FIG. 13 after engagement, with the hook component in a stable, concave position. 
     FIG. 15 is a side view of another bi-stable hook component. 
     FIGS. 16A-16C are alternative cross-sections of the hook component of FIG. 15, taken along line  16 — 16  in FIG.  15 . 
     FIG. 17 shows the hook component of FIG. 15 incorporated into a diaper tab. 
     FIGS. 18A and 18B show another bi-stable hook component in stable convex and stable concave position, respectively. 
     FIG. 19 schematically illustrates a method and apparatus for forming bi-stable hook component tape. 
     FIG. 20 is a cross-sectional view, taken along line  20 — 20  in FIG.  19 . 
     Like reference symbols in the various drawings indicate like elements. 
    
    
     DEFINITIONS 
     Within the context of this specification, each term or phrase below will include the following meaning or meanings. 
     “Bi-stabilize” refers to the ability of an object to assume either of two stable forms, and the ability to alternate between these two forms through the application of force. By “stable form” we mean that once the form is obtained, the object will remain in that form unless acted upon by a force external to the object. 
     “Concave” and “convex” are used in their traditional sense, both requiring at least some curvature in both of two perpendicular planes normal to the surface at a common point. The curvature in each of the two planes does not have to be equal, and in some instances the ideal conformance with an underlying surface, or a particular bi-stability feature, may require the curvature in one of the planes to be relatively small (i.e., having a large radius of curvature) with respect to the curvature in the other orthogonal plane, such that the touch fastener substantially conforms to a surface with a fairly large radius of curvature. 
     “Flexible” refers to materials which are compliant and which will readily conform to the general shapes and contours of the objects in contact with the materials. 
     “Inherently curved surface” is a surface that is curved in a relaxed state, in the absence of an external biasing force. 
     “Inherently non-flat surface” is a surface that is non-flat in a relaxed state, in the absence of an external biasing force. 
     “Longitudinal” and “transverse” have their customary meaning, as indicated by the longitudinal and transverse axes depicted in FIGS. 1-9. The longitudinal axis lies in the plane of the article to which the fastening system is attached and is generally parallel to a vertical plane that bisects a standing wearer into left and right body halves when the article is worn. The transverse axis lies in the plane of the article generally perpendicular to the longitudinal axis. 
     “Peel force” refers to a force that tends to pull two adjoining bodies away from one another in opposite directions generally perpendicular to a plane in which the bodies are joined. 
     “Personal care garment,” as used herein, includes diapers, training pants, swim wear, absorbent underpants, adult incontinence products, feminine hygiene products, medical garments, and the like. The term “medical garment” includes medical (i.e., protective and/or surgical) gowns, caps, gloves, drapes, face masks, blood pressure cuffs, bandages, veterinary products, mortuary products, and the like. 
     “Polymers” include, but are not limited to, homopolymers, copolymers, such as for example, block, graft, random and alternating copolymers, terpolymers, etc. and blends and modifications thereof. Furthermore, unless otherwise specifically limited, the term “polymer” shall include all possible geometrical configurations of the material. These configurations include, but are not limited to isotactic, syndiotactic and atactic symmetries. 
     “Releasably attached,” “releasably engaged” and variations thereof refer to two elements being connected or connectable such that the elements tend to remain connected absent a separation force applied to one or both of the elements, and the elements being capable of separation without substantial permanent deformation or rupture. The required separation force is typically beyond that encountered while wearing the absorbent garment. 
     “Shear force” refers to forces that tend to produce an opposite but parallel sliding motion between two bodies&#39; planes. 
     “Thermoplastic” describes a material that softens when exposed to heat and which substantially returns to a non-softened condition when cooled to room temperature. 
     These terms may be defined with additional language in the remaining portions of the specification. 
     DETAILED DESCRIPTION 
     FIGS. 1 and 2 illustrate a hook-and-loop fastening system  48  that utilizes the three-dimensional geometry of the hook and loop components, as well as the forces employed to apply a product to a wearer, for increased security. This hook and loop fastening system  48  is particularly suitable for use on disposable absorbent articles, such as diapers, training pants, feminine hygiene products, incontinence products, other personal care or health care garments, including medical garments, or the like. 
     Hook component  20  and loop component  22  can be brought together to be releasably attached, or releasably engaged, to one another. The hook component  20  has a number of individual hooks  24  protruding generally perpendicularly from a flexible hook backing material  26 . A semi-rigid layer  27  is attached to the flexible hook backing  26  to enable stable convex (FIG. 1) and concave (FIG. 2) conformations of the surface of the hook component  20  from which hooks  24  extend. Similarly, loop component  22  has a number of individual loops  28  protruding generally perpendicularly from a flexible loop backing material  30 . Upon initial contact with the hook component in convex form (FIG.  1 ), some of the individual hooks  24  and loops  28  are brought into engagement. When the hook component is subsequently snapped to its concave position  32 , this engagement is augmented and additional hooks and loops are engaged to increase the strength of the fastening. As the hook component is moved to its concave stable form, the lateral spacing between the engageable heads of adjacent hooks is reduced, helping to entrap the engaged loops or fibers. Tension in the engaged fibers is also increased as hook component  20  forces the deflection of the base of loop component  22  by pulling on its loops. This tension can also help to secure the fastening. 
     The force required to separate the engaged hooks  24  and loops  28  can be reduced, when desired, by bending the hook backing material  26  out of the concave position  32  (FIG. 2) into a flat position  34  (FIG. 3) or a convex position  36  (FIG.  1 ). 
     FIGS. 4-6 show a hook component  20  having J-shaped hooks  24  rather than the mushroom-shaped hooks  24  shown in FIGS. 1-3. The hook component  20  having J-shaped hooks  24  can be engaged with and separated from the loop component  20  in the same manner as the hook component  20  having mushroom-shaped hooks  24 . Virtually any hook shape can be used with the hook component  20  of this invention. Suitably, the individual hooks  24  have an engageable head  38  at a free end  40  of each hook  24 . The head  38  can be flat (FIGS. 1-3,  8  and  9 ), rounded (FIGS.  4 - 7 ), or any other suitable shape. The mushroom-shaped hook  24  shown here has a circular head  38  with a flat top and can look the same in the transverse direction (FIG. 8) as in the longitudinal direction (FIG.  9 ), in which case the stem  42  of the hook  24  is suitably round or square as viewed from above. Alternatively, the stem  42  of the hook  24  can be oblong, rectangular, triangular, or any other suitable shape. One example of a mushroom-shaped hook is CFM 60-1002 (0.06) available from Velcro USA of Manchester, N.H. This particular hook component  20  has an array of hooks  24  protruding from the backing  26 , with the hooks  24  lined up in two directions to form rows. The longitudinal direction is indicated by an arrow  44  in FIGS. 1-8. The term “transverse direction” refers to a direction perpendicular to the longitudinal direction. The transverse direction is indicated by an arrow  46  in FIG.  9 . In many diaper fasteners, the transverse direction of the hook fastening component is typically aligned parallel to the wearer&#39;s waistline, with the longitudinal direction of the fastening component parallel to the wearer&#39;s backbone. The hooks  24  can be organized into other geometries to optimize engagement with available loops  28 . 
     As used herein, the terms “convex” and “concave” are used with respect to the side of the hook component  20  from which the hooks  24  protrude. When the hook component  20  is in the fastened, concave position  32 , the concavity of the hook component  20  ideally curves to fit comfortably about a curvature of the wearer&#39;s body at the location of the hook component  20 . 
     The individual loops  28  of the loop component  22  can be needled, stitched or otherwise connected to or projected through the loop backing material  30 , which can suitably be made from a non-woven material. The individual loops  28  thus connected can be made of yarn or tow. Once the loops  28  have been formed, fibers forming the loops  28  can be anchored in place by bonding the fibers to the loop backing material  30  with heat and/or adhesives or any other suitable means. Such suitable loop components  22  are also available from Velcro USA of Manchester, N.H. The individual loops  28  can alternatively be formed as an integral part of a fibrous non-woven web such as a spunbond non-woven web or a staple fiber carded web. These non-woven webs can be creped or crimped using processes known in the art, to form well-defined loop regions within their fiber structures. Another suitable type of material for making the loop component  22  is “point unbonded” material. Point unbonded materials are fabrics having continuous thermally bonded areas defining a plurality of discrete unbonded areas and are described in greater detail in U.S. Pat. No. 5,858,515 to Stokes, et al. 
     The hook backing  26  includes semi-rigid layer  27 , to create enhanced fastening security. FIG. 10 shows a top view of a plurality of mushroom-shaped hooks  24  on the hook backing  26  with the hook backing  26  in a flat position  34 . FIG. 11 shows a top view of the same mushroom-shaped hooks  24  with the hook backing  26  in a convex position  36  (see also FIG.  1 ). When the hook backing  26  is in the convex position  36  as shown, the heads  38  of the hooks  24  are a greater distance apart from one another than when the hook backing  26  is either flat or concave. When the hook backing  26  is in the convex position  36 , the loops  28  of the loop component  22  can more readily engage the hooks  24  because of this increased spacing. 
     Once the loops  28  are inserted between the hooks  24 , the hook backing  26  can be bent, or snapped, into a concave position  32  to engage the hooks  24 . A top view of the position of the hooks  24  on the concave hook backing  26  is shown in FIG.  12 . As can be seen in FIGS. 2 and 12, when the hook backing  26  is in the concave position  32  the heads  38  of the hooks  24  are closer to one another than when the hook backing  26  is in its unstable flat or stable convex form. Suitably, in the concave position  32  the heads  38  of adjacent hooks  24  contact one another, thereby fully trapping the loops  28  between adjacent hooks  24 . The hook backing  26  is flexible, yet contains enough rigidity to maintain a concave shape until a user forces the hook backing  26  into its convex shape. 
     A reasonable amount of energy is required to “snap” the hook backing  26  into a convex  36  or a concave position  32 . The amount of energy required should be small enough to enable a typical user to overcome the internal stabilizing forces of the backing  26  without over-exertion, yet large enough to avoid unintentional form transition due to forces applied to the fastener during normal use, such as the forces exerted on a diaper fastener, for example, during infant wear. Preferably, the force required to toggle the hook backing  26  should be of similar magnitude to the force required to toggle a common light switch. 
     In the illustrated embodiment of FIGS. 1 and 2, the hook backing  26  has an inherently curved surface  50  (such as an inherently partial spherical or ellipsoidal surface) and can assume either a stable concave position  32  or a stable convex position  36  but will not assume any other state (e.g., a flat state) without maintained force. In another example (not shown), a bi-stable hook backing can be toggled between a flat stable position. (as in FIG. 3) and a stable concave position (as in FIG.  2 ). 
     The semi-rigid layer  27  can either be a separate layer attached to the hook backing  26  or can serve as the entire hook backing  26  from which the hooks  24  protrude. For example, the semi-rigid layer  27  of FIGS. 1 and 2 forms a partial spherical or ellipsoidal surface  50 . Suitable materials for the semi-rigid layer  27 , or semi-rigid hook backing  26 , include metals, laminates, and/or thermoplastic polymers selected from polyamides, polyesters, polyolefins (e.g. polypropylene or polyethylene) or another suitable material. Spring steel tape, for example, may be heat-treated to display a bi-stable nature and then either embedded in, or attached to, hook backing  26 . If the hooks  24  are co-formed with a flexible hook backing  26 , or are otherwise adhered to a flexible hook backing  26 , the flexible hook backing  26  can be bonded to the semi-rigid layer  27 , such as a semi-rigid partial spherical or ellipsoidal surface  50 , or any three-dimensionally shaped surface that can be formed from a flat material, to enable the hook component  20  to bend and remain in the concave  32  or convex position  36 . The semi-rigid layer  27  can be either continuous or non-continuous, such that the semi-rigid layer  27  can cover an entire surface of the hook component  20 , or merely a center portion of the hook component  20 , or merely a border portion of the hook component  20 , or any other suitable portion of the hook component  20 . 
     Preferable hook components  20  generally have between about 16 and about 620 hooks per square centimeter, more preferably between about 124 and about 388 hooks per square centimeter, and desirably between about 155 and about 310 hooks per square centimeter. The hooks  24  suitably have a height of from about 0.00254 centimeter (cm) to about 0.19 cm, preferably from about 0.0381 cm to about 0.0762 cm. The hooks may be molded or extruded from a thermoplastic polymer selected from polyamides, polyesters, polyolefins (e.g. polypropylene or polyethylene) or another suitable material. Likewise, the hook backing material  26 , not including the semi-rigid material, can be made of any of these or any other suitable materials since the hooks  24  and the hook backing  26  are generally produced from the same material in one process, such as the continuous molding method taught by Fischer in U.S. Pat. No. 4,794,028, hereby incorporated by reference. The hook backing material  26  generally has a thickness in a range of between about 0.5 millimeter (mm) and about 5 mm, preferably in a range of between about 0.8 mm and 3 mm, with the combined backing and hooks having a basis weight in a range of from about 20 grams per square meter to about 70 grams per square meter. The hooks  24  are spatially arranged in rows or any other suitable configuration on the hook backing  26 . 
     When fastening system  48  is employed on an absorbent article, such as a diaper, for example, the hook component  20  is attached to a first portion  52  of the article and the loop component  22  is attached to a second portion  54  of the article. Alternatively, the loop component  22  can cover an entire surface of the article, with the hook component  20  attached to only a portion of the article. As shown in FIG. 13, prior to fastening the loop component  22  and the hook component  20 , the hook component  20  is in its stable convex form  36 . As shown in FIG. 14, when the hook component  20  and the loop component  22  are fastened, the hook component  20  is in the concave state  32 , which helps to contour the fastening system to the shape of the wearer&#39;s body. 
     Thus, fastening system  48  employs energy supplied by a user to manipulate the form of the fastener to engage and trap loops  28  of the loop component  22  among the hooks  24  of the hook component  20 . The result is a three-dimensional fastening system  48  that improves fastening security and can also be optimized to conform to a wearer. 
     The hook component  20  can bend into a partial spherical surface, such that the hook heads radially expand or contract into convex and concave modes, accordingly. The hooks  24  can be flat-top hooks, J-shaped hooks, or any other suitably shaped hooks. In the illustrated system, the hook component is supported with a backing that forces the hook component to be in either the convex or the concave mode, but does not allow the hook component to assume a flat state once engaged. This system requires a reasonable amount of energy to snap from concave to convex, and vice-versa. 
     The touch fastener components are attached to, for example, a diaper. The consumer receives the diaper (or other product having the above-described hook and loop fastening system), with the bi-stabilizing component in the convex state with respect to its active side. The consumer presses the bi-stabilizing component to the active surface of the other component with enough force to “snap” the stiff backing of the bi-stabilizing component into its concave state. As this happens, the fastener elements of the other component (e.g., loops or fibers) bypass the engaging heads of the fastener elements of the other component (e.g., hooks) to be trapped or ensnared once the bi-stabilizing component is snapped into the concave state, resulting in improved fastening performance over some conventional systems. 
     FIG. 15 illustrates a length of bi-stable male fastener component tape  60  with hook-shaped fastener elements  62  integrally molded with a surface of a common, curved, sheet-form base  64 . As shown, base  64  has curvature in two orthogonal planes. First, it defines a relatively large radius of curvature “R” about an axis perpendicular to the figure, and locally defines at each point along its length a relatively small radius of curvature “r” about an axis extending along its length (see also FIG. 16A, for example). The hook-shaped fastener elements  62  are molded in rows extending along the length of the tape. The fastener elements may be molded to face in the same direction, as shown, or in opposite directions along alternating rows. 
     As shown in cross-sectional views  16 A- 16 C, various embodiments of hook tape  60  have different structures of base  64  to result in its bi-stable nature. Referring first to FIG. 16A, for example, base  64  is a lamination of two different materials. The upper surface  66  of the base is formed of the same resin as the hook-shaped fastener elements  62 , as integrally molded. The underside  68  of the base, however, is formed of a second material, such as another polymer resin with different physical properties than the material forming the upper surface of the base and the hooking elements. In such case, the resin of underside  68  is preferably a relatively rigid resin, such as polyvinyl chloride. The underside resin can be made substantially more rigid than the upper surface resin by selectively cross-linking the underside resin after molding, for example. Alternatively, the material of underside  68  can be a pre-formed material of relatively stiff structure and exhibiting shape memory, such as a strip of spring steel, that is laminated to the upper base resin, either during hook molding or afterward. 
     In another embodiment shown in FIG. 16B, base  64  consists of a single layer of resin integrally molded with hook elements  62 . Subsequent to molding, base  64  is rigidified, such as by selective cross-linking from below, as it is permanently deformed to have its dual-curved form. 
     In the embodiment of FIG. 16C, a thin strip  70  of pre-curved metal, such as spring steel as employed in common, coiled measuring tape, is encapsulated between upper surface resin  66  and lower surface resin  68  as the hook elements are molded. By keeping the molding temperature below the annealing temperature of the metal strip, but high enough to cause some permanent curling of the metal strip along its length, the hook tape exhibits bi-stable properties as molded. 
     The hook tape  60  of FIG. 15 can further be laminated to a substrate  72  to form a diaper tab  74 , as shown in FIG.  17 . (As illustrated in FIG. 17, the hook tape  60  has mushroom-type fastener elements, but is otherwise as shown in FIG.  15 ). One end of tab  74  is permanently secured to a diaper  76 , as is known in the art, with hook tape  60  extending across the free end of the tab for engaging a patch of loop material (not shown) to hold the diaper in place. Similar applications include closures for other types of personal care products, garments and the like. 
     The hook component  78  of FIGS. 18A and 18B has a base  80  consisting of an upper surface  82  of resin integrally molded with hook elements  62 , and a lower surface formed by a metal strip  84  laminated to the resin. Both the resin surface  82  and metal strip  84  are creased along either edge of a convex bi-stable region  86  (convex from the perspective of the hooking side) to form two side flanges  88  covered with exposed hooks but curved only about a single axis. Flanges  88  may be permanently secured to a substrate, for example, while leaving bi-stable region free to be flexed between its stable convex (FIG. 18A) and concave (FIG. 18B) positions without unduly binding the substrate. 
     Referring now to FIG. 19, apparatus  90  for molding bi-stable hook tape includes an extruder  92  that provides a sheet of molten resin to a nip between a rotating mold roll  94  and a pressure roll  96 , such that some of the resin is forced into blind mold cavities of mold roll  94  to form hook-shaped fastener elements connected by a planar sheet of the resin cooled on the surface of the mold roll. After the resin is sufficiently cooled, the planar base and integrally molded fastener elements are stripped from the mold roll by passing the molded strip about a take-off roll  98 . More details of extruder  92 , mold roll  94  and pressure roll  96  can be found in U.S. Pat. No. 4,794,028 to Fischer. From take-off roll  98 , the molded hook tape is passed between two heated forming rolls  100  and  102  (see also FIG. 20) to form parallel bands of hook tape with cross-machine radius of curvature “r”. Extruder  92  can be adapted to supply two flows of resin to the molding nip, such as for molding the structures shown in FIGS. 16A and 16C. Embodiments containing metal strips in their bases can be formed by introducing the metal strip to the resin in the molding nip, in an in-situ lamination process such as is taught by Kennedy et al. in U.S. Pat. No. 5,260,015, the entire contents of which are also incorporated herein by reference. 
     As shown in FIG. 20, rolls  100  and  102  have mating, pleated outer surfaces, with the outer surface of roll  102  defining a series of hook-relief grooves  104  separated by base-engaging ribs  106  that force the base of the resin down into corresponding depressions in roll  100  to laterally stretch the base of the hook tape across the curved pleats of roll  100 . This curvature is either set while the hook tape is on roll  100 , or immediately after leaving roll  100 , such as in a cross-linking curvature setting station. By varying the temperature, speed, tape tension, and other parameters of this curvature-inducing process, both longitudinal and cross-machine curvature can be permanently created in the hook tape. Optimization of the process parameters will be different for each hook tape material and structure. 
     It will be appreciated that details of the foregoing embodiments, given for purposes of illustration, are not to be construed as limiting the scope of this invention. Although only a few exemplary embodiments of this invention have been described in detail above, those skilled in the art will readily appreciate that many modifications are possible in the exemplary embodiments without materially departing from the novel teachings and advantages of this invention. Accordingly, all such modifications are intended to be included within the scope of this invention, which is defined in the following claims and all equivalents thereto. Further, it is recognized that many embodiments may be conceived that do not achieve all of the advantages of some embodiments, particularly of the preferred embodiments, yet the absence of a particular advantage shall not be construed to necessarily mean that such an embodiment is outside the scope of the present invention.