Molded fasteners with side wings

Abstract

A fastener in the form of a flexible strip (18) comprising a resin layer (20) with opposite longitudinal edges (36) and an array of individual fastener elements (10) seated on a surface of the flexible strip. Each fastener element has a resin stem (12) extending upwardly from and continuous with the resin layer (20), the stem having opposite lateral side surfaces (14) facing the edges of the flexible strip, and a wing (16) projecting from one of the lateral side surfaces of the stem and disposed above the resin layer. The wing defines a region (Ac) in a vertical plane coincident with one of the side surfaces of the stem. Measured perpendicular to the resin layer, the center of gravity (C) of the region is closer to the lowest point of the region than to the highest point of the region.

Description

TECHNICAL FIELD

[0001] This invention relates to molded fasteners and methods for engaging such fasteners in self-locking fastening assemblies. BACKGROUND

[0002] Some fastening products have a series of individual protruding fasteners that interlock with fasteners from a related product to form a releasable fastener. This type of fastener is sometimes referred to as "self-locking," especially when the fasteners on each product are similar in size and shape.

[0003] Fasteners of self-engaging fastener (SEF) products typically feature overhanging heads that flex when the two assemblies are pressed together and require head flexion to separate after engagement. Many SEF products utilize mushroom-shaped fasteners with heads that overhang in multiple directions. Many such mushroom-shaped fasteners are manufactured by deforming the ends of molded or extruded stems to create heads that overhang on multiple sides of the stem. It is possible to manufacture SEF assemblies using only molded hooks, each overhanging in a single direction, as described in U.S. Patent No. 8,225,467.

[0004] For many SEF products, some type of feedback may be desirable, such as audible or haptic, to indicate that the two assemblies are fully engaged.

[0005] Improvements in fastener elements useful for SEF products and fastener element structures that are also useful for releasable loop engagement are desired. SUMMARY

[0006] One aspect of the invention relates to a fastener comprising a flexible strip with a resin layer and having opposed edges extending longitudinally along the flexible strip, and an array of individual fastener elements seated on a surface of the flexible strip. Each fastener element comprises a resin stem extending upwardly from and continuous with the resin layer, the stem having opposed lateral side surfaces facing the edges of the flexible strip, and a wing projecting from one of the lateral side surfaces of the stem and overlying the resin layer. The wing has a bottom surface facing and overhanging the resin layer and a top surface facing away from the resin layer.The wing defines an area in a vertical plane coincident with one of the lateral surfaces of the stem, the area having a lowest point and a highest point with respect to the perpendicular distance to the resin layer and the area defining a center of gravity.

[0007] In some embodiments, the center of gravity, measured perpendicular to the resin layer, is closer to the lowest point than to the highest point.

[0008] In some examples, the upper surface forms a pair of protrusions spaced apart along the lateral side surface of the stem and extending away from the flexible strip, with the upper surface defining a recess between the protrusions. The protrusions may, for example, be located at opposite ends of the wing.

[0009] In some embodiments, in all vertical planes parallel to the side surface of the stem and extending through the wing, a cross-section of the wing has a center of gravity that is closer to a lowest point of the cross-section than to a highest point of the cross-section.

[0010] In some cases the wing extends laterally from the stalk to a free distal edge.

[0011] In some examples, the underside surface of the wing is non-reentrant. In some cases, the upper surface of the wing is U-shaped.

[0012] The wing preferably has a thickness which, measured perpendicular to the surface of the resin layer, is less at a point between opposite ends of the wing than at the opposite ends of the wing.

[0013] In some examples, the wing, adjacent to the vertical plane, defines a larger static moment of area with respect to downward bending about a first bending axis parallel to the resin layer in the vertical plane at a lowest extent of the wing than with respect to upward bending about a second bending axis parallel to the resin layer in the vertical plane at a top extent of the wing.

[0014] In some embodiments, the array of individual fasteners is configured and arranged to form a releasable fastener when mated with an identical array of fasteners. Such embodiments are referred to as "self-locking." Preferably, the array of individual fasteners is configured and arranged such that each fastener of a column disposed between fastener columns of the identical array overlaps the wings of at least three fasteners of the identical array.

[0015] Another aspect of the invention relates to a method for releasably joining two surfaces. The method comprises bringing two fasteners into contact as described above such that the wings of one of the fasteners touch the wings of the other of the fasteners, each of the two fasteners sitting on the respective one of the two surfaces, and pressing the two fasteners together such that the wings deform and interlock, and the wings of one of the two fasteners come closer to the resin layer of the other of the two fasteners than the wings of the other of the two fasteners.

[0016] Another aspect of the invention relates to a method for molding a fastener product. The method comprises pressing flowable resin into a mold defining an array of closed fastener cavities extending inwardly from a surface of the mold, solidifying the molded resin within the cavities along with a resin layer formed on the surface of the mold, and withdrawing the solidified resin from the cavities by tension applied to the layer. Note that each cavity is shaped to form a resin stem extending upwardly from and continuous with the resin layer, the stem having opposite lateral side surfaces facing the edges of the flexible strip and a wing projecting from one of the lateral side surfaces of the stem and spaced from the resin layer.The wing has a lower surface facing and projecting above the resin layer, and a top surface facing away from the resin layer. The wing defines a region in a vertical plane coincident with one of the lateral surfaces of the stem, the region having a lowest point and a highest point relative to the perpendicular distance from the resin layer, and the region defining a center of gravity. The center of gravity, measured perpendicular to the resin layer, is closer to the lowest point than to the highest point.

[0017] Configuring laterally expanding wings with centroids in the lower half of the wing cross-section has been found to provide a noticeable advantage in the relative force profiles during engagement and disengagement of fastener assemblies, as well as improving haptic engagement feedback. During engagement, the upper portion of the wing is subjected to strong tension and stretches as the wing flexes to engage, whereas during disengagement, the lower portion of the wing is subjected to tension as the wing flexes to disengage. Advantages may also arise from designing the wing to have a larger static area moment when bending downward about a horizontal bending axis along the lateral side surface of the stem at a lowest extent of the wing than when bending upward about a horizontal bending axis along the lateral side surface of the stem at a top extent of the wing.Various structures disclosed herein may also provide advantages in releasably engaging loop fibers, particularly structures with longitudinally offset wings.

[0018] The details of one or more embodiments of the invention are set forth in the accompanying drawings and the following description. Other features, objects, and advantages of the invention will become apparent from the description, drawings, and claims. DESCRIPTION OF THE DRAWINGS Fig. 1 is a side view of a fastener Fig. 2 is an end view of the fastener of Fig. 1. Fig. 3 is a perspective view of the fastener of Fig. 1 Fig. Figure 4 is a view of part of an assembly of fasteners as shown in Fig. 1, as part of a fastening strip. Fig. 5 is a side view of two of the fastening strips of Fig. 4 in a locked state. Fig. Figure 5A schematically illustrates two parallel, adjacent columns of fasteners with wings. Fig. 6 is an end view of the two snapped fastening strips of Fig. 5. Fig. Figures 7A-7D illustrate step-by-step release of fastener strips by elastic flexion of the fastener wings. Fig. Figure 8 is a cross-sectional view of a portion of another fastener through the wing-stem interface. Fig. 8A is an end view of the fastener of Fig. 8, which shows a wing in dashed outline. Fig. 9A-9F show additional fastener designs with different wing structures. Fig. 10 is a perspective view of another fastener, with offset wings. Fig. 11 is an enlarged exploded view of a portion of an edge of a set of forming rings for forming the fastener of Fig. 1-3. Fig. 12 schematically illustrates a method and apparatus for forming a fastening product.

[0019] Like reference numerals in the different drawings indicate like elements. DETAILED DESCRIPTION

[0020] With reference first to Fig. 1-3, a male fastener 10 comprises a central stem 12 with flat, opposite sides 14 and a curved profile. Extending from each of the opposite sides 14 is a corresponding wing 16 disposed above a flexible strip 18, at least the upper surface of which is formed from a resin layer 20 with which the stem 12 forms a single, continuous resin mass. The flat, opposite sides 14 lie in vertical planes perpendicular to the layer 20 and define a substantially constant thickness "t" of the stem. In this particular example, the upper surface 22 of the stem is concave, forming a depression at the top of the stem extending between the opposite sides 14 between two rounded peaks 24, which in this example form the highest extent of the male fastener 10 above the strip 18.The strip itself is oriented longitudinally along the direction AA in . Fig. 1 continuous, so that opposite sides 14 are referred to as opposite lateral side surfaces.

[0021] Each wing 16 extends laterally to a flat distal end 26 lying in a vertical plane. The wings and stem together also form a single, continuous resin mass, which is formed by molding the entire structure in a similarly shaped cavity, as described below. Each wing is shaped to extend substantially laterally, with the top and side surfaces tapered only slightly (e.g., by 4.5 degrees) to facilitate removal of the molded wing from its portion of the mold cavity. The underside surface 28 of each wing faces and overhangs the resin layer 20, with a significant radius where the underside surface 28 meets the lateral side surface 14 of the stem. The top surface 30 of each wing faces away from the resin layer.The upper surface of each wing forms a pair of projections 32 spaced along the lateral side surface 14 of the stem and projecting from the flexible strip 18, the upper surface defining a recess 34 between the projections. The upper end of each projection 32 is curved, with a radius of approximately 0.05 mm, and the recess 34 defines an arc with a radius of approximately 0.12 mm. Each fastener 10 is symmetrical about a vertical plane extending through the stem midway between the two wings.

[0022] To give an idea of ​​the general size of such fasteners, the total height of the stem is approximately 0.93 mm and the stem thickness is 0.35 mm. The wings have a total length, along AA, of 0.6 mm and a total height (excluding the radius at the bottom) of approximately 0.22 mm, and protrude a total of 0.2 mm from the stem.

[0023] With reference to Fig. 4, in a typical arrangement, many such male fasteners will be arranged in rows and columns along the flexible strip 18 with their opposite lateral side surfaces 14 facing the longitudinal edges 36 of the strip. Fig. Figure 4 shows only two columns and three rows of fasteners 10, but in most commercial applications, a strip will have 10 or more columns and 50 or more rows of such elements. As shown, the fasteners of adjacent columns may be slightly offset longitudinally, so that the fasteners of a given row are not in exact alignment.

[0024] The offset is also in Fig. 5 visible, the two of the fastening strips 38 from Fig. 4 interlocking, with their arrangements of fastening elements 10 facing each other and overlapping, so that the wings 16 of the fastening elements of one fastening strip 38 are closer to the resin layer 20 of the other fastening strip 38 than its own wings 16. The extent of the longitudinal offset O LA between the adjacent columns of a fastening strip is slightly larger than the total length Lw of one of the wings in the longitudinal direction, which in turn is larger than the total length L G the gap between wings in the longitudinal direction (Lw > L G ). Adjacent fastening elements of the two interlocking arrangements are also spaced apart by a distance O LBlongitudinally offset by a distance less than the length of one of the wings. Once engaged, the assemblies of fasteners can slide past each other in the direction transverse to the wings. This sliding in the machine direction is useful when winding mated fastener strips onto a reel. Ideally, the wings of adjacent structures in any given column will be arranged so that the opposing wings of the mating fastener strips will always overlap as the two assemblies slide past each other. It will be understood that the height variation across the top of the wing (in this case, the projections extending beyond the central recess) can help to provide some sliding resistance when two unmated fastener strips are held together with the top surfaces of the wings touching.Forming these structures in cavities rather than as an extrusion that is later cut and stretched means that irregularities in the fastener pattern can be deliberately incorporated into the assembly to create haptic feedback when moved.

[0025] The fastening strips 38 shown here are basically designed for such engagement with one another, also referred to as self-locking, and not for engagement with a loop field, although such a fastening strip could indeed form a releasable fastening with a suitable loop material.

[0026] Fig. Figure 5A schematically illustrates two adjacent columns of an array of such winged fasteners, with the projected top surface of the wings and stem of each element represented by a block 40 on a post 42. To ensure that each winged fastener always engages at least three fasteners of the mating array, two conditions must be met. First, the wing length Lw must be greater than the sum of the longitudinal offset O LA and the gap length L G . In other words, L W > (O LA + L G ).

[0027] Secondly, the gap length L G be less than half of the longitudinal offset O LA , or L G < O LA / 2.

[0028] Fig. Figure 6 shows the engagement of the two assemblies. The wings 16 of the two fastening strips 38 overlap laterally by the distance "x", which means that the interlocking assemblies of fastening elements 10 resist withdrawal due to the mutual interference of the wings when the two strips are pulled apart. The overlap distance "x" is greater than the total lateral distance between adjacent columns (i.e., x > (X1 + X2)), which, together with the longitudinal overlap of the wings (L W > L G ), means that the two assemblies cannot be separated from a relative position without some wing bending.

[0029] Fig. Figures 7A-7D illustrate the wing deflection during such a separation step by step. For illustrative purposes, only one set of intermeshing wings is shown, and the deflections are not to scale. As the intermeshing strips begin to separate, their respective wings approach each other ( Fig. 7A) until their underside surfaces touch. Further separation causes the touching wings to bend away from their respective resin layers 20 ( Fig. 7B), and with increasing bending the lateral overlap between the wings decreases ( Fig. 7C), until the wings can finally move past each other ( Fig. 7D). The wings are designed to withstand such hyperelastic bending without plastic deformation or cracking. Due to the longitudinal offset between the intermeshing wings (O LB in Fig. 5), the deflection does not occur entirely in one plane, but involves a certain amount of rotation around a horizontal transverse axis. In this example, one of the projections 32 of each wing is caught in the recess 30 of the other wing (see Fig. 3) when the wings first touch upon separation, and the separating wings do not overlap completely along their length, but only by the distance L W -O LB ( Fig. 5). The process of interlocking two such fastening strips also involves significant wing deflection, but in the opposite direction, as the wings flex to pass each other during interlocking. It is desirable that the force-deflection curve in the direction of engagement be such that the final engagement provides tactile or haptic feedback, allowing the user to feel (and possibly hear) that the fastening strips have fully interlocked.

[0030] There are certain physical properties that enhance the ability of wings to undergo such significant deflection in both directions under load and provide the desired feedback. One of these properties has been found to be related to the cross-sectional area of ​​the wing in a vertical longitudinal plane. Fig. Figure 8 shows such a cross-section at the wing-stem interface (i.e., at the vertical surface of the stem), but of a fastener with a stem where the top surface is convex rather than concave. The area Ac of the cross-section has a centroid 'C' closer to the bottom edge of the area than to the top edge. In other words, C1 < C2. Preferably, such a relationship holds not only at the interface with the stem, but in all vertical longitudinal planes through the wing. This characteristic is believed to help promote a difference in the force / deflection curve for the wing when it is bent downwards (during engagement) compared to when it is bent upwards (during separation), resulting in more perceptible haptic feedback of engagement while maintaining acceptable engagement / separation force values.

[0031] With reference to Fig. 8A, the structure of the wing is also such that it has a larger static moment of area with respect to downward bending about a horizontal bending axis (Y2) along the lateral side surface of the stem at a lowest extent of the wing compared to the moment of area with respect to upward bending about a horizontal bending axis (Y1) along the lateral side surface of the stem at a top extent of the wing.

[0032] At the Fig. 1 to 3, it can be seen that such a positioning of the center of gravity is partly due to the depression in the upper surface of the wing compared to the lower surface. Such a shift in the center of gravity does not depend on this specific shape. For example, each of the Fig. 9A-9F have a center of gravity closer to the lower edge of the wing cross-section than to the upper edge. In all cases, the cross-section does not vary across the lateral width of the wing (from stem to tip), except due to a shape release taper or radius on the lower wing surface (in Fig. 9A, Fig. 9B, Fig. 9D, Fig. 9E and Fig. 9F by hatching). The wing in Fig. 9C differs from that in Fig. 1 by the absence of a significant radius on the lower surface.

[0033] In the example from Fig. 9A, the upper surface of the wing has only one projection located at one longitudinal end of the wing. The upper surface of the wing of Fig. 9B has a projection that is only slightly offset from the longitudinal center of the wing. The wing of Fig. 9C is similar to that of Fig. 1, but without a lower radius. The wing made of Fig. 9D has a wedge-shaped cross-section, with one longitudinal end thicker than the other, so that the upper surface is inclined relative to the strip surface. The wing made of Fig. 9E essentially has the shape of a half-cylinder extending from the stem, with the curved part facing away from the strip surface. In other words, within the vertical plane, the top of the wing forms a circle and the bottom of the wing forms a horizontal line. The wing of Fig. Figure 9F illustrates the general concept of downward displacement of the center of gravity in a cross-section that is quite complex with multiple upward projections and a non-planar bottom surface.

[0034] As explained below, the fastener structures shown can be formed in cavities created by aligning flat plates. This molding process allows the wings to be slightly offset from the stem centerline, extending beyond the stem's longitudinal ends. Such a structure is Fig. 10, in which each wing extends longitudinally beyond the stem edge. The wings may each extend beyond a respective edge, as shown, or they may both extend beyond the same edge (e.g., in longitudinal alignment with each other). As long as the amount of longitudinal overhang is not too great, such a structure can function as a self-locking fastener to interlock with other structures as described above. Such an overhang can also increase the usefulness of such a fastener for releasably engaging loop fibers, since the overhang forms a hook for such fibers. This example also shows a convex upper stem surface like that of Fig. 8.

[0035] The fastener structures described above can generally be formed into the desired shape in cavities extending radially from the outer cylindrical surface of a forming roll formed as a stack of concentric plates or rings. Each column of fasteners is formed into a set of three rings, comprising a stem ring sandwiched between two wing rings, spaced from adjacent sets of rings by solid or spacer rings against which the distal ends of the wings are formed. Fig. Figure 11 shows a portion of the periphery of a set of three such rings. The stem ring 50 defines a stem-shaped cavity 52 open toward the edge of the ring. Each wing ring 54 defines a wing-shaped cavity 56 positioned to be continuous with the stem-shaped cavity 52 in the stacked set of rings, so that when flowable resin is forced through the opening at the edge of the ring into the stem-shaped cavity, it fills all three cavities. The surface of the adjacent spacer ring exposed to the wing-shaped cavity to form the distal end of the wing can be etched or contoured to form a non-flat distal wing end, if desired.The edges of the cavities on each ring side surface are sharp, except for the outermost edge 58 of the wing-shaped cavities facing the stem ring 50, which is rounded to form the radius on the underside of the wing where it connects to the stem. Each ring will have a large number of cavities distributed around its circumference, so the stacked set of rings can define over 500 hook cavities. The rings of the set must be precisely rotationally aligned to ensure that the wing cavities overlap with the stem cavity. Referring also to . Fig.12, a mold roll 60 consisting of a plurality of such concentrically stacked ring sets, held tightly together during the molding and removal process, may be used to mold a continuous resin strip 62, molding an assembly of fasteners 10 with its upper surface, as disclosed, for example, in US 10,864,662, the entire contents of which relating to methods of molding fasteners is incorporated herein by reference. In this example, flowable resin 64 from an extruder 66 is forced into the cavities 68 of the mold roll 60 by a counter-rotating pressure roll 70. After curing in the cooled mold roll, the molded fasteners are withdrawn from their cavities by passing the resin layer formed on the surface of the mold roll over a stripping roll 72.

[0036] Although some examples have been described for illustrative purposes, the foregoing description is not intended to limit the scope of the invention, which is defined by the appended claims. There are and will be further examples and modifications within the scope of the following claims. QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents submitted by the applicant was generated automatically and is included solely for the convenience of the reader. This list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions. Cited patent literature

[0000] US 8,225,467

[0003] US 10,864,662

[0035]

Claims

[1] Fastening means comprising: a flexible strip (18) having a resin layer (20) and having opposite edges (36) extending longitudinally along the flexible strip, and an array of individual fastening elements (10) seated on a surface of the flexible strip, each fastening element comprising a resin stem (12) extending upwardly from and continuous with the resin layer, the stem having opposite lateral side surfaces (14) facing the edges (36) of the flexible strip; and a wing (16) projecting from one of the lateral side surfaces of the stem and lying above the resin layer (20), the wing having a bottom surface (28) facing and projecting beyond the resin layer and a top surface (30) facing away from the resin layer, wherein the wing defines an area (Ac) in a vertical plane coinciding with one of the side surfaces of the stem, the area having a lowest point and a highest point with respect to a perpendicular distance to the resin layer, and the area defining a center of gravity (C), where, measured perpendicular to the resin layer, the center of gravity is closer to a lowest point than to a highest point (C1 < C2). [2] The fastener of claim 1, wherein the upper surface forms a pair of projections (32) spaced apart along the lateral side surface (14) of the stem and extending away from the flexible strip (18), the upper surface defining a recess (34) between the projections. [3] The fastener according to claim 2, wherein the projections (32) are arranged at opposite ends of the wing (16). [4] The fastener of any preceding claim, wherein in all vertical planes parallel to the side surface (14) of the stem (12) and extending through the wing (16), a cross-section of the wing has a center of gravity closer to a lowest point of the cross-section than to a highest point of the cross-section. [5] The fastener of any preceding claim, wherein the wing (16) extends laterally from the stem (12) to a free distal edge (26). [6] The fastener according to any one of the preceding claims, wherein the underside surface (28) of the wing (16) is non-reentrant. [7] The fastener according to any one of the preceding claims, wherein the top surface (30) of the wing (16) is U-shaped. [8] The fastener of any preceding claim, wherein the wing (16) has a thickness which, measured perpendicular to the surface of the resin layer (20), is less at a point between opposite ends of the wing than at the opposite ends of the wing. [9] The fastener of any preceding claim, wherein the wing (16), adjacent the vertical plane, defines a greater static area moment with respect to downward bending about a first bending axis (y2) parallel to the resin layer in the vertical plane at a lowermost extent of the wing than with respect to upward bending about a second bending axis (y1) parallel to the resin layer in the vertical plane at a topmost extent of the wing. [10] The fastening means according to any one of the preceding claims, wherein the array of individual fastening elements (10) is configured and arranged to form a releasable fastening when joined to an identical array. [11] The fastener of claim 10, wherein the array of individual fasteners (10) is configured and arranged such that each fastener (10) of a column disposed between fastener columns of the identical array overlaps wings (16) of at least three fasteners (10) of the identical array. [12] A method for releasably joining two support surfaces, the method comprising: Bringing two fastening means according to claim 1 into contact with each other such that the wings (16) of one of the fastening means touch the wings (16) of the other of the fastening means, each of the two fastening means being seated on the respective one of the two support surfaces, and Pressing the two fastening means together so that the wings deform to engage with each other, wherein the wings of one of the two fastening means come to lie closer to the resin layer (20) of the other of the two fastening means than the wings (16) of the other of the two fastening means. [13] A method of forming a fastening product, the method comprising: Pressing flowable resin (64) into a mold (60) defining an array of closed fastener cavities (68) extending inwardly from a surface of the mold; solidifying the pressed resin in the cavities together with a resin layer (20) formed on the surface of the mold; and Pulling the solidified resin out of the cavities by tension applied to the layer; wherein each cavity (68) is shaped to form: a resin stem (12) extending upwardly from and continuous with the resin layer (20), the stem having opposite lateral side surfaces (14) facing the edges (36) of a flexible strip (18) comprising the layer, and a wing (16) projecting from one of the lateral side surfaces (14) of the stem (12) and spaced from the resin layer, the wing having a bottom surface (28) facing and projecting beyond the resin layer and a top surface (30) facing away from the resin layer, wherein the wing (16) defines a region (Ac) in a vertical plane coinciding with one of the side surfaces (14) of the stem, the region having a lowest point and a highest point with respect to a perpendicular distance to the resin layer (20), and the region defining a center of gravity (C), where the center of gravity (C), measured perpendicular to the resin layer, is closer to the lowest point than to the highest point.

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