Abstract:
A self-engaging touch fastener, separable by peeling, includes portions with a generally thin shell structure and a closely spaced array of bilaterally undercut generally convex protrusions which are directed by proximate oblique stem walls into an interlocking relationship with corresponding receptors when the portions are compressed. Touch fastening products have a non-grabbing non-abrasive texture and may be manufactured of thin plastic films or similar low cost materials using a simple die-cutting/forming method, thus providing a user friendly reliable and economic alternative to hook-and-loop and other presently available fastening systems for connecting flexible materials for applications including packaging, apparel, and disposable products. The device may be furnished as an independent product, as an integrally formed or molded segment of a primary product, or attached to rigid or flexible substrates. An apparatus and method for economically manufacturing such device is also provided.

Description:
PRIORITY 
     This application claims priority on the basis of US provisional patent applications: 61/137,420, filed Jul. 29, 2008; and 61/207,007, filed Feb. 6, 2009. 
    
    
     FIELD 
     This application is related to touch-type surface fasteners with hermaphroditic portions. 
     BACKGROUND 
     The field of Touch fasteners includes many well known products manufactured under the trade names of Velcro®, Aplix®, YKK®, 3M®, and others. Generally these systems include hook-and-loop types with differentiated portions, or self-engaging types with hermaphroditic portions, each type having well known attributes as well as known drawbacks. Abrasion, clogging, noise, lack of durability, failure when wet, loss of strength, indiscriminate grab, profile thickness, and relative cost are all frequently cited negative attributes of hook-and-loop systems. Mushroom systems and others share similar negative attributes and are limited by the excessive force needed for disengagement and limited cycle life. With regard to disposable products in particular, cost and type of material are significant factors. Abrasion, relative to products in contact with skin, as well as noise are also significant issues for many applications such as personal care products. 
     Examples of fabric based hook-and-loop fasteners include: DeMestral U.S. Pat. No. 2,717,437; Erb U.S. Pat. No. 3,594,863, Zinke et al U.S. Pat. No. 4,910,062, and Brumlik, U.S. Pat. No. 3,522,637. Examples of molded hook-and-loop hooks include: Kayaki, U.S. Pat. No. 5,067,210, Berger et al, U.S. Pat. No. 5,119,531; and Provost, U.S. Pat. No. 6,526,633. Examples of self-engaging undercut mushroom-like fasteners include: Flanagan, U.S. Pat. No. 3,666,113; Hall, U.S. Pat. No. 4,531,733; and Tuma US2009/0126166 A1. Examples of interengaging bulbous shapes include: Batrell, U.S. Pat. No. 4,946,527, Petersen, U.S. Pat. No. 5,867,876; Clume, U.S. Pat. No. 6,162,040. Chesley et al., U.S. Pat. No. 5,505,747 disclose hooks and mushrooms of various profiles. The prior art also includes other types of interengaging three dimensional shapes, examples of which include: Rouser, U.S. Pat. No. 5,201,101; Murasaki, U.S. Pat. No. 5,457,856; McGanty, U.S. Pat. No. 5,212 855; Berg, et al, U.S. Pat. No. 5,657,516; and Appledorn, U.S. Pat. No. 4,875,259. Ausen, U.S. Pat. No. 7,241,483, more recently discloses a reticulating web with hooks formed by a multiple step process. All typically include a plurality of male to male members locking with multidirectional undercuts or by friction. 
     Several examples of prior art include relatively thin structures which are formed into fastening elements. Zimmerman, U.S. Pat. No. 3,604,145, discloses a strip of sheet material formed into nesting frictionally connected pins/receptors. Spier, U.S. Pat. No. 4,581,792, discloses a sheet formed uni-directionally undulating structure which is self-engaged by friction along its alternating undulated edges. Cohen, U.S. Pat. No. 4,870,721, discloses hollow pyramids with barbs for fastening with a second receiving structure. Battrell, in U.S. Pat. No. 4,946,527 and U.S. Pat. No. 5,221,276, presents interengaging portions with pluralities of three-dimensionally bulbous shapes with hollow inner cores, apparently formed from a sheet material: the portions are interengaged by compression causing respective bulbous heads to deform and then expand so that their inclined underwalls interface. 
     Fastening Technologies, including slidingly engaging fasteners and several improvements thereto were introduced by the present inventor, as disclosed in U.S. Pat. Nos. 5,983,467, 7,245,416, AU Patent 60/034,096, EPO Patent 1,011,362, CA Patent 2, 311,306, and other patents pending including Published US application 2008/0018025 A1 concerning methods of making fasteners including die forming methods. Slidingly engaging fasteners (SEFs) comprise generally hermaphroditic arrays of islands with undersides and corresponding receiving apertures between adjacent islands. The islands are connected by sliding correspondent undersides beneath each other until they are stopped at the narrow end of an effectively tapered chamber. Some of the previously disclosed embodiments of SEFs also have included three-dimensional surface modeling to enhance self-alignment, spacing of islands to prevent back sliding, as well as three dimensional aspects to enhance initiation of engagement by compression. However, the thickness of islands is generally equal to the depth of corresponding apertures so that at least minimal shear pressure is required to achieve engagement. For some applications requiring significant flexure, low cost production, relatively small scales, and engagement by simple compression (touch), these previous SEF systems may be less than fully adequate. In particular, an SEF system which is fully self-aligned, which can be engaged solely by touch, which has a generally undulating texture with no exposed edges, and which can be produced of inexpensive materials by die forming would be particularly useful. 
     A pressure activated self-adhering device also by the present inventor has been published as US 2008/0034560 A1. It includes a plurality of nodules protruding from the interstices of a structural matrix which define receptors for receiving like modules to effect a very low-profile self-engaging fastener with no additive thickness. This system however requires relatively significant compressive engagement pressure and is preferably manufactured by a relatively expensive molding process. 
     There appears to be a continuing significant need and market for an improved type of self-engaging touch fastener which is easy to use, relatively durable, quiet, non-abrasive to skin, and which could be manufactured at low cost by die cut and formed materials including plastic films. 
     GENERAL DESCRIPTION 
     A primary object of the present invention is to provide an economical alternative to presently available touch fasteners which is non-grabbing, smooth to touch, strong, quiet, hermaphroditic, and inexpensive to manufacture. Other objects of this invention include providing a touch engageable fastener: which has a non-grabbing texture; which is soft to touch; which is economical to produce by die forming sheet materials; which securely connects portions with a relatively light touch; which is resistant to aggregate tensile stresses but easily peeled apart from a joining portion end; which is substantially resistant to shear, tensile, and torque forces; which is quiet; which is self-engaging with hermaphroditic portions; and which can be provided at virtually any scale and in a variety of embodiment designs. Further objects will become apparent throughout the disclosure. 
     The Touch Engageable Fastener includes two similar portions, each having an array of bilaterally undercut convex protrusions with fore and aft stems, defining receptors between each pair of protrusions which are deeper than the height of protrusions and also longer than protrusions, extending from a proximate stem wall. The protrusions are arranged so that, when the portions are lightly pressed together by a relative compressive force (touch), the protrusions of a first portion self-align with and are snuggly received into the corresponding receptor openings of a second portion. Upon continuing compression the protrusions are then diverted longitudinally into an effectively interlocked position by obliquely sloping stem walls and entrapped within respective corresponding receptors. The assembled portions are resistant to longitudinal or lateral shear as well as tension, but can be readily disconnected by simply applying tension to a lateral edge of one portion and sequentially reversing the connection process by peeling. In several preferred embodiments the fastener portion is presented as an effectively dimpled, undulating surface made up of a plurality of dome-like protrusions, thereby providing a generally soft surface texture with blind fastening elements. Alternative geometric configurations are also included. 
     In each embodiment, receptors are at least somewhat deeper than corresponding protrusions, and stem walls are obliquely inclined, so that after the protrusions pass through their respective receptor openings, continuing perpendicular touch pressure causes the protrusions to shift longitudinally within the receptor until respective protrusion undersides oppose each other to effect a secure interlocking connection. 
     Touch Engageable Fasteners of a first preferred embodiment have receptor openings sized to just snugly receive corresponding protrusions without significantly distorting the structure and have a longitudinally asymmetrical design to resist applied uni-directional shear, thereby requiring minimal pressure to engage or disengage and causing minimal structural stress or sound. Touch fasteners of other embodiments include receptor openings which are somewhat smaller than corresponding protrusions and a longitudinally symmetrical design, so that, as compression is applied, interfacing protrusion sidewalls “snap” into respective openings, temporarily distorting to allow corresponding edges to bypass, resulting in an assembly resistant to bi-directional shear as well as tensile stresses. 
     The “snap” engagement attribute may be applied to embodiments of either symmetrical or asymmetrical design. In embodiments of the “snap” type, the depth to height differential allows bypassing undercut edges to distort vertically as they pass through respective receptor openings and to then resiliently assume their prior shape as the protrusion also shifts longitudinally. 
     Longitudinally asymmetrical touch fasteners include aft stems which are wider than forward stems, thereby effecting a longitudinally narrowing receptor so that leading undercut edges of protrusions are blocked by the second stems at a position of optimal underside interface. Rows of protrusions may be furnished either in aligned rows (quadrille pattern), wherein the protrusion sidewalls interface with two adjacent stem walls of the next row; or in offset rows (diamond pattern), wherein the protrusion sidewalls interface with a single stem wall. A “snap” engagement aspect may also be optionally combined with such an asymmetrical configuration to provide primary unidirectional shear resistance with effective “back-out” resistance. 
     Longitudinally symmetrical fasteners with a “snap” aspect and at least three alternately offset (diamond pattern) rows are configured in a longitudinally symmetrical configuration with fore and aft stems of effectively equal width, wherein the receptors are bounded and longitudinally aligned with the proximate protrusion stem walls of each adjacent offset row. This configuration combines bi-directional shear resistance with relatively short adjustment intervals. Such embodiments may be designed with relatively long receptors, in which protrusions are able to slide longitudinally when subjected to shear pressure; or they may be designed with relatively short receptors, close coupled, in which protrusions are longitudinally limited: the former requiring less engagement pressure, the latter providing a short adjustment interval. Such design choices must be based on application requirements and material characteristics. 
     Diverse geometric design options included within the scope of the invention provide optimal solutions for assorted application requirements. Design options include polygonal shapes, protrusions of diverse proportions including elongated and widened configurations, oblique undersides, and alternative geometries and combinations within the general parameters of the invention. Fasteners of the asymmetrically type are engaged with minimal touch pressure and are highly resistant to uni-directional and lateral shear, though they are less resistant to shear in a reversed (back-out) direction. Such fasteners are particularly suitable for applications affording relatively constant shear such as an elastic strap, or for a medical wrap or personal item, etc. where minimal pressure is also desirable. Fasteners of the “snap” type typically require somewhat greater compressive pressure in order to complete engagement and are therefore most suitable for applications requiring a secure connection where somewhat greater engagement force is tolerable such as in the closure for an apparel item, clothing accessory, footwear, packaging, etc. Fasteners of the “snap” type combined with a longitudinally symmetrical aspect may be best for applications requiring minimal shear strength such as various single use disposable products, plastic bags, packaging, etc. Because the device in any geometric variation is economical to produce at virtually any scale, a wide range of uses is foreseen in applications ranging from personal products, household goods, and personal electronic devices to high strength construction assemblies. 
     In general, a minimum of two rows of at least two protrusions are required on at least one of the portions to provide uni-directional shear resistance in the asymmetrical fasteners discussed above. Three rows are required to provide equal bi-directional shear resistance as in the symmetrical configuration above. In many applications, multiple rows are provided on at least one of the portions in order to maximize the range of adjustability. In some applications such as an integral closure for a sheet form plastic bag, a minimum number of rows is preferable. 
     Preferred embodiments of the device include a relatively thin generally flexible undulating structure with dome-like protrusions with edges extending partially over laterally adjacent receptors. The structure of such embodiments has a generally uniform thickness contiguous throughout the undulations except at its undercut edges. The fastener with its inherently closely spaced convex protrusions presents an effectively soft primary surface texture which is non-grabbing and non-abrasive (somewhat similar in texture to common “bubble wrap”) which can be placed in close contact with skin or sensitive surfaces without causing abrasion, while the undercut undulations simultaneously provide an effective means of ventilating the underlying surface. 
     Embodiments of the device are produced at a relatively small scale by die forming thin sheet materials with a punching and forming dieset. Although such thin film materials are generally highly flexible in their unformed sheet state, those materials with satisfactory shape memory formed into a three-dimensional matrix of convex and concave forms become sufficiently rigid in their micro-structure to maintain repetitively reusable fastening function, resistant to crushing loads, while remaining flexible in the aggregate. In general, a material thickness to protrusion width ratio of 1:3 would appear to be a minimum practical limit, resulting in relatively stiff protrusions. Ratios of 1:10 and greater have been proven effective in prototypes. Such design choices are inherently related to material characteristics as well as application parameters. 
     When furnished as a flexible structural sheet with relatively small scale fastening modules, it is expected that an effective majority of the modules may will be fully connected and effective at a particular time. The aggregate redundancy of the system will be sufficient to maintain a strong connection of the whole even with some segments disconnected, a matter which may be determined by design. 
     In a preferred manufacturing method, a relatively thin plastic film, preselected for its inherent shape memory, is fed through a counter rotating dieset having punching and forming segments. The resultant fastening product can therefore be significantly less costly to produce than presently available molded, extruded or heat formed fastening systems. 
     Alternatively the device may be manufactured for many applications such as disposable products of paper or other fibrous matter by utilizing a similar counter rotating dieset into which a saturated pliable sheet or slurry is fed, the material dried as the fastening product is extracted. Another alternative means of manufacture comprises heat forming by feeding a softened semi-solid plastic sheet through a similar apparatus. Other manufacturing methods include: injection molding; punch and die forming sheet-metal embodiments; sequentially forming rows of fastening elements with a reciprocating punch and die apparatus; stamp/forming a pre-perorated sheet material; machining a solid substance; or other known means of manufacturing applicable to the present structural aspects. Alternative embodiments may be molded or formed of materials with differential thickness, for instance injection molded as an integral fastening zone in the surface of a primary product, molded of plastic or rubberized foams or fibrous materials, or simply machined in diverse materials by computerized machining tools. 
    
    
     
       DRAWINGS 
         FIG. 1  schematically represents a first preferred embodiment of a touch fastener portion in plan view.  FIGS. 1A-C  are sectional views. 
         FIG. 2  schematically represents a second preferred embodiment of a touch fastener portion in plan view.  FIGS. 2A-B  depict sectional views. 
         FIGS. 3 ,  3 A and  3 B schematically represent an alternative preferred embodiment of a touch fastener portion with elongated protrusions. 
         FIGS. 4 ,  4 A, and  4 B schematically represent an alternative preferred embodiment of a touch fastener portion with proportionally wide protrusions. 
         FIG. 5  schematically represents an alternative preferred embodiment with minimal adjustment interval in an oblique view.  FIG. 5A  is a detail of  FIG. 5  in plan view. 
         FIG. 6  schematically represents in sectional view a preferred apparatus for manufacturing a touch fastener portion. 
     
    
    
     DESCRIPTION 
     As seen in  FIGS. 1-5 , the Touch Engageable Fastener in diverse embodiments includes two like portions  01 ,  01 ′ each having a plurality of protrusions  02  arrayed in a first row  13  of at least two such protrusions. Each protrusion has bilateral generally convex sidewalls  18  terminating at undercut edges  03  which are arcuately bowed away from a longitudinal axis  04 , and which have undersides  07 . The undercut edges are separated by first stems  05  and second stems  06  longitudinally contiguous with the generally convex sidewalls  18 , interconnecting protrusions at fore and aft ends respectively. The axis  04  and bilateral undersides  07  of each protrusion are generally coincident with a meeting plane  08 . The stems  05 ,  06  each have stem walls  10  contiguous with the sidewalls  18  which continue below the meeting plane and have stem edges  09 . 
     Embodiments of the invention are described herein as though oriented on common orthogonal width, length, height axes, although such terms are intended to be descriptive in a relative sense only. The term “touch” as used herein is intended to imply the application of a relatively light compressive pressure comparative to the scale of the device: in small scale embodiments such as personal products “touch” implies finger pressure sufficient to engage a segment of the portions without conveying significant distortion on the assembly as a whole or on a substrate; in larger scale embodiments proportionally greater pressure may be required as a matter of design choice. The term “generally convex” is intended to include any shape that fulfills the function of three-dimensionally directing protrusions into corresponding respective receptor openings. Therefore, within the scope of the invention, protrusions may be manufactured with diverse geometries and profile curves which generally have a wider base than top including conical, prismatic, revolved curves, pyramidal shapes, and truncations or combinations of such shapes. The term “arcuately bowed” with respect to the undercut edges of protrusions is intended to include a curved line, two or more conjoined straight line segments, and/or conjoined straight and curved line segments, provided that the edges of a protrusion are closer at a point adjacent to at least the first stem than at the widest lateral section of the protrusion. 
     At least one receptor  11  is bounded laterally by the stem edges  09  of at least the first stems  05 , bounded vertically by the undersides  07  of two laterally adjacent protrusions, and is bounded longitudinally by an oblique stem wall  10  of at least one next proximate protrusion  14  in an adjoining proximate row  21 . The stem wall  10  is generally oblique to a basal surface  16  and preferably follows a concave profile generally complementary to the convex profile of a corresponding protrusion sidewall  18 . As seen in  FIGS. 1-5 , the stem wall inclines generally into the receptor from the meeting plane, although segments at and near to the meeting plane may be vertical. The term “oblique”, in reference to stem walls, is intended to include diverse curvatures which serve to direct protrusions into their interlocking disposition, preferably mimicking the general convexity of a protrusion profile. 
     Each receptor  11  has a receptor opening  17 , coincident with the meeting plane  08 , which is bounded by the undercut edges  03  of two laterally adjacent protrusions  02  and by a stem wall  10  of at least one next proximate protrusion  14  of one longitudinally adjacent row  21 . The effective planar profile of a receptor opening  17  generally corresponds to the profile of a corresponding protrusion  02  at the meeting plane, so that a relatively minimal compressive force (touch) will cause the protrusion to “snuggly” enter the opening without causing significant structural distortion of the structure as a whole. It is important to note that the receptors  11  generally comprise a cavity which is at least somewhat larger than a corresponding protrusion  02 : extending longitudinally from the stem wall  10  of at least one proximate protrusion  14 , effecting a receptor length rl; and extending vertically from undersides  07  to a basal surface  16 , depth d; and having an optimally interlocked position vertically opposite the protrusion undersides  07 , indicated as hatched area  25 . Thus, the receptor openings  17  are inherently offset longitudinally from the protrusion undersides, in that they are coincident with the meeting plane  08  at the relatively lowest horizontal profile between sets of surrounding convex sidewalls  18 . 
     The term “snuggly” is intended to imply a tight but not overly restrictive relationship and may include protrusion profiles and receptor openings of effectively equal size as well as receptor openings somewhat smaller than protrusion profiles. Touch Fasteners of a first type as schematically illustrated in  FIGS. 1 and 4  are designed with receptor openings essentially equal in size to a protrusion profile so that the protrusions may enter snuggly but unimpeded. Touch Fasteners of a second type, as will be seen in  FIGS. 2 ,  3  and  5 , are designed with somewhat smaller receptor openings so that respective interfacing protrusion sidewalls  18  must be temporarily distorted at their edges  03  as they enter receptor openings  17 , then resiliently resume their original shape, thereby effecting a “snap” reception aspect. The aspect of “snugness” is generally determined by the longitudinal spacing of proximate rows of protrusions. 
     The Touch Fastener is configured so that: the vertical depth “d” of a receptor  11  from the meeting plane  8  to its basal surface  16  is at least slightly greater than the height “h” of a protrusion  02  above the plane; the lateral width “w” between the undercut edges  03  of a protrusion is greater than the gap distance “g” between the edges  03  of adjacent protrusions  02 ; and the width “s” of a receptor  11 , between the stem edges  09  of at least the first stems  05  of laterally adjacent protrusions  02 , is at least as great as the width “w” of a corresponding protrusion. 
     The two portions are fastened together by a method which includes:
         1. Providing two oppositely oriented portions  01 ,  01 ′;   2. Lightly compressing the portions together into initial contact (at a position “A”);   3. Continuing compression so as to cause opposing protrusions  02  to bypass as their interfacing surfaces slide laterally and/or longitudinally along respective inclines on a generally convex interface  12  until they each generally self-align with a respective receptor opening  17  (at position “B”);   4. Continuing compression so as to cause the protrusions  02  to each be snuggly received into corresponding receptor openings  17  as the respective undercut edges  03  bypass each other;   5. Finally, continuing compression so as to cause respective corresponding oblique stem walls  10  to interface with the obliquely sloping protrusion sidewalls  18  so as to cause the protrusions to shift in a longitudinal direction, effectively entrapping respective corresponding undersides  07  in a generally vertically opposing juxtaposition within the receptor  11  (at position “C”), thereby effectively interlocking the portions.       

     It is important to note that the dimensional differential specified above regarding receptor depth “d” being at least somewhat greater than protrusion height “h” is an important inherent aspect of the invention. After corresponding respective undercut edges  03  have bypassed the receptor opening at the meeting plane, protrusion sidewalls  18  then continue to effectively shift obliquely along their respective interfacing stem walls  10 , simultaneously moving both vertically and longitudinally so as to cause the respective undersides  07  to effectively interlock as they move longitudinally under each other. A d&gt;h differential is necessary in order to allow this essential interlocking action without requiring application of an additional shearing force. As will be seen below, the d&gt;h aspect is also important to the function of fasteners of the “snap” type by providing space for corresponding resiliently distorted undercut edges to bypass as they shift longitudinally. This dimensional differential may be relatively small in many embodiments, but is essential to effect an interlock solely by compression. 
     Additional applied shearing pressure and/or torsional shifting of the assembly may cause individual protrusions  02  to move longitudinally within their respective receptors while their corresponding undersides  07  generally remain at least partially interfaced. Thereby, the assembly allows for significant flexure without causing the portions to inadvertently disconnect. 
     Although when thus engaged the assembly is effectively resistant to multi-directional shear, tensile stresses, and torsion, the interlocked assembly may be peeled apart relatively easily by initially separating the portions  01 ,  01 ′ at an unattached end  19 . Lifting the end  19  of an attached portion causes the nearest interfacing undersides  7  to begin to separate at its nearest end, adjacent to a stem edge  09 . As further peeling force is applied, the undercut edges  03  readily bypass as the protrusions  02 , are sequentially withdrawn through their respective receptor openings  17 . Thus, the portions are fully separated, ready for repositioning or removal. As used herein, the term “tension” or “tensile force” is intended to imply a relative perpendicular force generally acting on the structure as a whole. The term “peeling” is intended to imply application of a relative perpendicular force at a portion end so as to sequentially pull the portions apart. 
     The first preferred embodiment schematically illustrated in  FIG. 1  includes a first portion  01  with a plurality of generally dome-like protrusions  02  arrayed in a quadrille pattern of generally aligned rows and columns which define a corresponding plurality of receptor openings  17  between each quadrille set of protrusions and a receptor between each adjacent pair of protrusions. The protrusions are generally circular in planar profile and include undercut edges  03  arcuately bowing away from the longitudinal axis  04 , and extending from a relatively narrow first stem  05  to a relatively wider second stem  06 . The receptor width “s 2 ” between the edges  12  of the second stems  06  of laterally adjacent protrusions is at least as wide as a first stem  05  and less wide than a second stem  06 , thereby effecting a longitudinally asymmetrical design. The receptor opening is sized to just snuggly receive the horizontal profile of a protrusion  02 ′ of second portion  01 ′ without restriction. The oblique stem walls  10  of the next proximate protrusions  14  are located so as to each interface with a segment of sidewall  18  of the second protrusion  02  and thereby direct the protrusion longitudinally into the receptor  11  where it is effectively entrapped by the respective interfacing underside  7  and by the edges  12  of the second stems  06  at an optimal interlocking position  25 . 
     As seen in Diagonal Cross Section B-B of  FIG. 1B , the oblique stem walls  10  are concave in profile, generally complementary to protrusion sidewall  18  though with a larger radius, so as to guide the interfacing protrusion into its interlocking position with minimal compressive pressure. An applied uni-directional shearing force is resisted by second stem edges  09  interfacing with the arcuately bowed undercut edges  03 ′ of each respective protrusion/receptor set. If the direction of the shearing force is reversed, the force is initially resisted by stem walls  10  interfacing with protrusion sidewalls  18 , though continuing such reverse shearing pressure may ultimately cause the assembly to disengage, as aft protrusion sidewalls  18 ′ obliquely interface and shift vertically along the next proximate second stem walls  10 . Therefore, such a longitudinally asymmetrical design is preferred for applications having a generally consistent uni-directional shear stress, as may be furnished by an elastic segment, gravity, etc. 
     The structure of this first preferred embodiment can be seen to have a generally uniform thickness “t”, thereby effecting the essentially thin shell aspect of the device. Such a structure is preferably die-formed from a plastic sheet material with sufficient shape memory to retain the essential three-dimensional elements of the device after forming. A preferred method of manufacture is discussed later in this disclosure. This thin shell aspect, in appropriate materials, allows the structure to be relatively flexible, in that the essentially planar base can flex in multiple directions whilst the three-dimensional aspect of the individual protrusions remains relatively constant. As the structure is flexed within reasonable limits, the interior dimensions of individual receptors may vary without significantly affecting the overall integrity of the connection because individual entrapped protrusions can move within their generally larger receptors and a sufficient number of protrusion/receptor sets remain interlocked at all times to maintain the integrity of the assembly, until it is deliberately peeled apart. 
     The type of embodiment schematically illustrated in  FIG. 1  includes receptor openings  17  with a planar profile at the meeting plane  08  of effectively the same size as the planar profile of a corresponding protrusion  02 . Therefore, in embodiments of this first type, a protrusion  03  just snuggly passes through a corresponding respective receptor opening  11  without requiring any additional compressive force beyond minimal touch to initiate engagement of the portions. Therefore this type of embodiment is primarily useful for applications resisting uni-directional shear stresses and requiring minimal attachment pressure. Such applications include overlapping portions having a relatively constant shear pressure maintained by an elastic segment elsewhere in the overlapping structure such as in a binding strap or enwrapping garment article with an integral elastic segment located between the opposing fastening portions. A hanging device activated by gravity along the longitudinal axis would exemplify another potential application. Advantages of this type of embodiment include that it provides high shear resistance and an effectively silent closure/separation action while requiring only minimal “touch” pressure to activate. 
     A representative example of an embodiment of the type schematically illustrated in  FIG. 1  includes dome-like protrusions at a relatively small scale of ±0.10″ diameter or less, die formed of a relatively thin ±0.01″ thick (t) or less plastic film (such as high density polyethylene). The attached assembly would therefore be approximately 0.125″ thick (h+d+2t). The preferred material is generally flexible and at least minimally resilient and has sufficient shape memory to retain its three-dimensional form. A touch engageable device such as this, comparable in scale to molded hook-and-loop, has potentially significant advantages over hook-and-loop including lower production cost, a smooth non-grabbing surface texture, hermaphrodicity, and silent operation; attributes which may be particularly useful for disposable products and packaging. Embodiments at other scales and of other materials will have particular advantages for many distinct application categories. 
     A second type of embodiment with an alternative configuration is schematically illustrated in  FIG. 2 . This embodiment includes the essential protrusions  02  and receptors  11  as outlined above, and also has a planar receptor opening profile which at the meeting plane is somewhat smaller in at least one dimension than a respective protrusion profile. Therefore, engaging the portions requires a compressive force sufficient to cause the respective protrusion sidewalls  18  to temporarily deform so as to allow entry of a protrusion into a receptor, thereby effecting a “snap” fit. Such a “snap” aspect can also be optionally applied to embodiments generally configured as in  FIG. 1  by simply reducing the distance between successive rows  13 ,  14 ,  15 , as will be seen in subsequent embodiments below. 
     The embodiment illustrated in  FIG. 2  also includes a longitudinally symmetrical aspect, comprising first and second stems  05  and  06  which are of generally similar width and protrusions  02  in each proximate row which are laterally offset to alternately align with receptors  11 , thereby defining receptors which are bounded longitudinally by the oblique stem walls  10  of each proximate row  13 ,  15 , and which are bounded laterally by the stem edges  09  of each laterally adjacent protrusion. Therefore, as relative compression is applied, resilient sidewalls  18  of both corresponding interfacing protrusions  02 ,  02 ′ are forcibly deformed temporarily in order to allow their respective undercut edges  03 ,  03 ′ to bypass each other. As the edges bypass and the sidewalls resiliently assume their approximate original shape, the protrusions are effectively entrapped in their respective receptors, confined longitudinally by the oblique stem walls  10  of the next 14 and last 15 proximate protrusions. The portions may be separated by peeling in a fashion similar to that described above. 
     Embodiments of such a longitudinally symmetrical configuration have an optimal interlocking position  25  where protrusions of both portions  01 ,  01 ′ are laterally aligned. However, the portions remain in an effectively interlocked disposition, position “C”, even when less than optimally aligned. 
     It should be appreciated that embodiments with rows of alternately offset protrusion, as in  FIGS. 2 ,  3 , and  5  and applicable to any embodiment, generally have an inherently shorter adjustment interval spacing. As can be seen in the diverse embodiments, altering proportions and combining aspects by design, within the invention&#39;s general parameters, can provide diverse functional attributes to solve particular application requirements. 
     The preferred embodiment of  FIG. 2  also includes protrusions which have a generally polygonal outline at the meeting plane  08  and have a generally pyramidal vertical profile, effectively generally convex as defined above. The protrusions illustrated in  FIG. 2  also can be seen to have a shorter height to width aspect (h/w) than those of  FIG. 1 , which aspect can be varied significantly within the scope of the invention to provide fastener portions with relatively lower or higher profile, smoother or harsher texture, and/or unforced or restricted closure. 
     It is important to appreciate that the present invention includes a significant range of potential geometric diversity in the configuration of its elements. It is also important to note that the device is fully scalable through a wide range of design choice, limited only by material characteristics and manufacturing method. Several alternative configurations are schematically illustrated in  FIGS. 3 ,  4 , and  5  by way of example. 
     The embodiment of  FIG. 3  includes a Touch Fastener with a longitudinally symmetrical aspect as described above, in which the protrusions  02  are laterally elongated, having a width greater than their length so as to effect a generally elliptical planar profile at the meeting plane. This embodiment also includes protrusions  02 ,  14 ,  15  arrayed in alternately offset rows  13 ,  21  which are spaced apart by a minimal distance so as to effect a “snap” fit, wherein the leading undercut edges  03  are forcibly distorted to allow entry into corresponding receptor openings  17 . The embodiment of  FIG. 3  includes protrusions  02  with undercut edges  03 , receptors  11 , and receptor openings  17 , as in other embodiments. The stem walls  10  are generally concave in at least their longitudinal profile as seen in  FIG. 3B , with a curvature of somewhat greater radius than that of a corresponding protrusion sidewall  18 . Therefore, a protrusion sidewall  18  interfacing such a generally concave stem wall  10  is directed longitudinally, from position “B” to position “C”, into its effectively engaged position by the application of relative compression on the portions. An embodiment of this type, with protrusions of a relatively wide width to length proportion, provides a relatively short adjustment interval which may be advantageous for many applications. 
     It should also be noted that the embodiment illustrated in  FIG. 3  comprises a generally undulating structure which includes “saddle” segments  20  at an intermediate level between the meeting plane and basal surface. This undulation aspect can be seen in  FIGS. 3A ,  3 B, and in the relative contours  23 , numbered 0-8, seen in the upper left quadrant of  FIG. 3 . This optional aspect allows the structure to flex generally along a midplane which is generally coincident with such an intermediate level; thereby providing a relatively high degree of flexure to the whole while the relative dimensions of protrusions and receptor openings remain generally constant. In comparison, embodiments as in  FIGS. 1 and 2 , with protrusions effectively extending upward from a generally uniform basal surface, will have receptor openings of relatively greater variability in size during flexure of the structure because the distance between protrusions at the meeting plane varies. A further benefit of this undulating aspect is that such fastener portions can be manufactured of a sheet material, as will be discussed, with relatively minimal stress on the material as it is stretched over a forming die. 
     The embodiment schematically illustrated in  FIG. 4  comprises a touch fastener with a longitudinally asymmetrical aspect in which the protrusions are proportionally long relative to their width. It includes protrusions  02  with undercut edges  03 , receptors  11 , and receptor openings  17  arranged in aligned rows to effect a quadrille pattern. Effectively concave stem walls  10  direct protrusion sidewalls  18  into corresponding respective receptors  11 . The aspect of relatively long protrusions in such an asymmetrical embodiment provides a relatively greater engagement area  25  of interfacing protrusion undersides  07  (shown hatched), thereby offering relatively greater tensile resistance as well as uni-directional shear resistance. This aspect may be optionally combined with receptor openings of either the snug or snap types, as noted above. 
     It should be noted that, in embodiments arranged in a quadrille pattern such as in  FIGS. 1 and 3 , the actuating interface  12  of sidewalls  18  to pairs of stem walls  10  occurs in a direction which is oblique to the longitudinal axis  04  (diagonal sides, “shoulders” of the stem walls); whereas in embodiments with alternately offset rows such as in  FIGS. 2 and 4  the interface  12  generally aligns with the axis  04 . 
     It should be noted that the embodiment of  FIG. 4  also includes an optional aspect in which the meeting plane  08  of each row is oblique to the basal surface  16 . As seen in  FIG. 4B , the leading segment of the undercut edges  03  adjacent to first stems  05  is relatively higher than the trailing edges  03  adjacent to the second stems  06 . As in prior embodiments, the depth d of the receptor at this leading edge, next to first stem  05  is at least somewhat greater than the height h of a corresponding protrusion so that sidewalls  18  can obliquely slide along respective corresponding stem walls  10  after passing through the receptor opening  17 , (and so that the corresponding undercut edges  03  can fully bypass, and resiliently re-expand in designs also having a snap aspect). However, in this embodiment, the depth of the receptor adjacent to the second stems  06  is approximately equal to the protrusion height so as to effect a wedge-like engagement aspect in vertical section, though the average receptor depth remains greater than the average protrusion height. This optional non-parallel meeting plane aspect can be advantageous in that protrusions may be more easily received into their respective receptor openings and frictional contact between the engaged undersides in their fully “wedged” position resists inadvertent release in the absence of a consistent unidirectional shear pressure. 
     The embodiment of  FIG. 4  also includes optional longitudinal saddles  20  which extend between the ends of adjacent stem walls  05  and  06 . In comparison with the embodiment of  FIG. 3  above, the saddles  20  here help retain lateral flexibility and three dimensional structural integrity of the structure while minimizing and effectively stiffening the structure longitudinally. It should be appreciated that varying the relative proportions of elements within the general geometric and functional parameters of the invention can result in a wide variety of application specific designs. 
       FIG. 5  schematically illustrates an embodiment having first  01  and second  01 ′ portions each with a generally undulating structure, including a plurality of dome-like protrusions  02  and generally concave receptors  11 . The portions are illustrated in an assembled juxtaposition with the second portion  01 ′ viewed from its underside. Embodiment of this type are designed to minimize the longitudinal adjustment interval, and to minimize movement of protrusions within their receptors. It is similar to previous embodiments of the longitudinally symmetrical “snap”—type as seen in  FIGS. 2 and 3 , with a receptor depth d somewhat greater than the protrusion height h, a protrusion width w greater than the gap g between adjacent undercut edges, and with rows of alternately offset protrusions. However, the embodiment of  FIG. 5  is configured so that the protrusion width w is larger than gap g between adjacent undercut edges by a relatively small differential to facilitate “snap”, and the receptor length rl between a next 14 and last 15 proximate protrusions in their respective next proximate rows is relatively short, so that the concave profile of proximate stem walls and basal surface closely approximates the longitudinal profile of a corresponding protrusion. Therefore, the engaged position “C” closely approximates the optimal interlocking position  25 : although the area of engaging undersides  07  is relatively small, the close-coupling of protrusions within their respective receptors provides a secure interlock. 
     As seen in  FIGS. 5 and 5A , the receptor openings  17  (position “B”) are closely offset from their respective underlying receptors  11  (position “C”). Therefore upon application of relative compression: 1) protrusions  02  are first directed into alignment with corresponding receptor openings  17  as respective convex protrusion sidewalls of the first and second portions interface and are guided into their lowest possible alignment prior to deformation of the respective undercut edges  03 , at a receptor opening  17  which is slightly offset longitudinally from the receptor center below; 2) As compression continues, respective corresponding sidewalls  18  adjacent to undercut edges  03  resiliently deform to allow passage of protrusions  02  into their corresponding receptors  11 ; and 3) As the temporarily deformed protrusions  02  pass through the receptor openings  17 , a next proximate protrusion sidewall  18  simultaneously interfaces with the nearest next proximate stem wall  10  so as to direct the protrusion into its corresponding receptor as the lateral sidewalls  18  at the undercut edges resiliently resume their original shape, thereby interlocking the portions with undersides  07  oppositely disposed. It is important to understand that, even in this type of “close-coupled” embodiment, as the protrusions  02  approach their corresponding receptor openings, in step  1 ) above, they are directed into an alignment which is at least slightly offset longitudinally from the centerline of the receptor (a receptor opening is always defined by two adjacent actuate undercut edges and at least one proximate stem wall in the nearest proximate row). It is also important to understand that here as in other embodiments the depth of receptors is inherently deeper that the height of a corresponding protrusion so as to allow protrusions  02  to longitudinally shift into their receptors  11  as their respective undercut edges  03  simultaneously bypass. 
     It should be understood that, as in all embodiments, the engaged protrusions are free to move within the boundaries of their respective receptors unless restrained by an applied shear or tensile force. In the embodiment of  FIG. 5  longitudinal movement is relatively closely restricted, although there is somewhat greater freedom to move in a vertical direction, whereas in other embodiments such as in 
       FIG. 3  above, relatively greater longitudinal movement is allowed relative to vertical movement. This aspect, variable by design choice, is generally beneficial in that it allows significant flexure of the whole without causing disconnection of individual elements. 
     The embodiment of  FIG. 5  also includes a relatively thin shell structure with diagonally disposed saddles  20  allowing flexure of the structure along a midplane coincident with the saddles without significant variation in relative protrusion and receptor dimensions. Such an embodiment, with its short adjustment interval and effectively tight engagement fit, can be highly useful for many applications and, like other embodiments, may be economically manufactured by die forming inexpensive materials with the preferred method and apparatus specified below. 
     For many applications, a first portion  01  may be provided as a relatively larger field or target area, whilst the second portion  01 ′ may be somewhat smaller in area (ideally about thumb size for apparel-type items) for adjustable placement at a desired location on the field, thereby maximizing two dimensional adjustability. The device is preferably designed so that it should not be generally necessary to connect all of the domes of both portions, since redundancy of the relatively strong interlocked domes should provide adequate strength in most instances even when a relatively large percentage are not fully connected. An end tab is preferably provided to at least the edge  19  of the overlapping portion as a grip for removal, graspable between thumb and forefinger. Embodiments of any design may be attached to a substrate by diverse commonly known means such as sewing, stapling, gluing, thermally fusing, etc. 
     It should be noted that all embodiments have fastening and non-fastening orientations relative to their radial alignment, whereby portions aligned perpendicularly will not interconnect. However, zones of alternately oriented protrusions may be provided in embodiments of symmetrical designs to provide for bi-directional engagement. It should also be noted that fastener portions include fastening orientations and non-fastening orientations relative to their top and bottom surfaces: they can not be produced as inter-engageable portions via either surface because of the above noted differential of receptor depth versus protrusion height and associated proportions. However, embodiments of any design may be produced with a self-engaging aspect by providing a first fastening zone effective from the first surface and, elsewhere along the same structure, a second fastening zone effective from the second surface. 
     An apparatus and method for manufacturing touch fastener embodiments is schematically illustrated in  FIG. 6 . For many applications various embodiments of the device may be economically die-cut and formed of a sheet material, including plastics, fibers, paper, sheet metal, etc. by such an apparatus which includes a set of counter-rotating cylindrical dies  50 ,  55 . A first cylindrical die  50  is provided with a geometric array of posts  51  extending from its surface  52 , the posts corresponding with the inner shell surface of protrusions  02  in a finished portion  01 . Each post has cutting edges  53  corresponding with undercut edges  03  and non cutting surfaces  54  corresponding with stems  05 ,  06 . A second cylindrical die  55  includes a surface  56  perforated by an array of apertures  57  corresponding with the posts, also with cutting edges  58  and non-cutting edges  59  respectively corresponding to undercut edges and stems, with allowance for material thickness t at each stem location. The cylindrical dies  50 ,  55  are assembled in a counter-rotating configuration so that surfaces  52  and  56  are separated by the thickness t of the sheet material  60  fed from roller  61 , and so that posts  51  progressively enter apertures  57  as the cylinders are rotated. Thence, the sheet material  60  is fed into the space between the cylinders and formed into the resulting portion  01  with its arrayed protrusions  02  and intervening receptors  11 . 
     The cylindrical dies may also include forming segments for other features such as optional ribs correspondent with saddles  20  between protrusions as in  FIG. 4  above. Likewise, both dies may include both post and aperture elements for forming fasteners with undulating structures such as the embodiment illustrated in  FIG. 3 . Other features may also include portion cuffing and separating devices identifying devices, etc. Optionally the dies may include zones with reversed die elements for forming self-engaging straps or portions with engagement zones on each surface of the structure. 
     The apparatus as described above may be used to economically produce fastener portions in a cold-forming process using materials with adequate shape memory to retain their formed three-dimensional aspects after release form the die set. A similar apparatus may be utilized in heat-forming other materials which may require application of heat to form useable fastener products. 
     Alternative methods of manufacture may include die-sets forming a single or relatively few protrusion rows with a reciprocating press wherein the product may be sequentially moved forward in a continuing process. The device may also be molded by injection molding, or integrally molded as a fastening zone in a larger molded component, by utilizing a set of bypassing dies. An injection molding or extrusion process can produce stronger and more durable fasteners for many applications such as clothing, sports and safety equipment, or various structural applications. Optional embodiments in rubber, rubberized plastics, silicon, foam, even leather or wood are also readily achievable with known manufacturing methods. 
     A wide range of materials may be utilized which have sufficient shape memory, strength, and flexure. High Density Polyethylene films of thicknesses ranging from 0.005″-0.020″ thick have been utilized effectively in cold formed experimental embodiments with module widths of 0.015″-0.25″. A material thickness to protrusion width ratio of approximately ⅓-⅛ appears to work well with this material. Other common plastics have similar characteristics for cold forming. Yet other materials may require application of heat and/or chemical processes. 
     Having thus described the various aspects of the invention in schematic form, which aspects may be combined and configured in diverse combinations within the scope of the invention, I hereby claim the following: