HOOK ELEMENT FOR SURFACE FASTENERS

Abstract: A hook or male element (10) for surface fasteners has peripheral surface irregularities in the form of protuberances (13) and/or grooves (14), affording increased surface area for a given material. This hook element (10) is capable of holding itself in the shape and posture desired for effective engagement with its female counterpart, a loop element.

Description: This invention relates generally to hook-and-loop or surface fasteners and particularly to hook elements therefor. Many hook-and-loop fasteners have been proposed in the art for use on a variety of articles such as sphygmomanometer bands, wrist watch bands, diapers, bags, clothings, sporting goods and the like. Conventional hook-and-loop fasteners comprise hooks or male elements on one support tape engageable with corresponding loops or female elements on the other tape, the hooks being plastic monofilaments having a round cross section and smooth or refined surface characteristics. Because of these physical characteristics, the starting monofilamentary material is relatively low in thermal efficiency and hence difficult to retain the shape of the hook afforded upon heat set, the resulting hooks being susceptible to elongation or deformation and hence insufficient in opportunity and strength of coupling engagement with their mating loops. Such hook elements are further difficult to dye to sufficient depth and with uniformity. EP-A-53 348 discloses a surface fastener comprising a substrate in the form of a tape and hook elements supported on said substrate and made of a thermoplastic filamentary material. However, the filamentary material is of smooth circular cross-section, making it less than ideal as regards thermal setting and retention of shape and, when dyed, retention of dye. FR-A-2 318 951 discloses monofilamentary sewing threads made of thermoplastic material having a multivaned configuration which provides greater knot strength, a factor which is not relevant to hook elements of a surface fastener. FR-A-2 318 951 points out at the beginning thereof that monofilament thread assumes the colour of the fabric into which it is sewn, meaning that the thread does not require to be dyed. Of course, the characteristics required of sewing thread are quite different to the characteristics required of hook elements in a surface fastener. With the foregoing drawbacks of the prior art in view, the present invention seeks to provide a hook or male element for surface fasteners which is capable of holding itself in the shape and posture desired for effective engagement with its female counterpart. The present invention further seeks to provide a hook element for surface fasteners which can be effectively dyed. The present invention further seeks to provide a hook element for surface fasteners which can be produced with less quantities of a starting plastic material than heretofore required. It is an object of the invention to provide a surface fastener comprising a substrate in the form of a tape and hook elements supported on said substrate and made of a thermoplastic filamentary material, with good thermal setting characteristics and good dye retention ability. The present invention provides a surface fastener as claimed in each of the claims, to which reference is directed. These and other objects and features of the invention will be better understood from the following description taken in connection with the accompanying drawings which illustrate by way of example certain preferred embodiments of the invention. Figure 1 is a front elevational view on englarged scale of a hook element secured to a support tape; Figure 2a is a plan view, partly sectional, on enlarged scale of a portion of a hook element according to one embodiment of the invention; Figure 2b is a cross-sectional view of Figure 2a; Figure 3a is a plan view, partly sectional, on enlarged scale of a portion of a hook element according to another embodiment of the invention; Figure 3b is a cross-sectional view of Figure 3a; Figure 4a is a cross-sectional view on enlarged scale of a hook element according to a further embodiment of the invention; Figure 4b is a cross-sectional view on enlarged scale of a hook element according to still another embodiment of the invention; Figure 4c is a cross-sectional view on enlarged scale of a hook element according to still further embodiment of the invention; and Figures 5a and 5b, Figures 6a and 6b, and Figure 7a and 7b inclusive each are cross-sectional views on enlarged scale of a symmetrical set of modified grooves in and protuberances on hook elements according to the invention contemplated under the invention. According to the principles of the invention, a hook or male element for a surface fastener is provided peripherally with a plurality of protuberances and/or grooves or notches. Referring to Figure 1, there is shown a preferred form of a hook or male element 10 generally circular in cross section which is supported on a substrate such as a tape 11 and which has a slit 12 through which the hook 10 is engageable with its mating loop or female element (not shown) in a manner well known in the art. The hook element 10 of Figure 1 is made of a suitable plastic filamentary material and has a plurality of longitudinally, radially extending protuberances 13 alternating with longitudinal grooves 14 as better shown in Figures 2a and 2b. The hook element 10 shown in Figures 3a and 3b is characterized by the provision of four longitudinally extending, cross-sectionally square protuberances 15 which are equally spaced in symmetric positions with their corners 15′ rounded off to prevent possible damage on the mating loop. Figure 4a shows a modification of Figures 3a and 3b in which the hook element 10 is provided with four grooves 16 in place of the protuberances 15. Figure 4b shows a hook element 10 similar to that shown in Figure 4a but having larger grooves 17. Figure 4c shows a hook element 10 is the same as that of Figures 3 and 3b except for the protuberances 15 being dimensionally larger. The hook element 10 shown in Figures 5a and 5b is provided with either cross-sectionally semicircular or arcuate protuberance or protuberances 18 or with cross-sectionally semicircular or arcuate grooves 19. Figures 6a and 6d show a hook element 10 having protuberance 20 or a groove 21 cross-sectionally trapezoidal. Figure 7a shows a further modification of a hook element 10 which is generally square in cross section and which has a longitudinal, cross-sectionally square groove 22 in each of the four sides, and Figure 7b has a hook element 10 symmetrical to that of Figure 7a in that it has protuberances 23 in place of corresponding grooves 22. Having thus described the invention, it will be understood that the hook element 10 for surface fastener is importantly and invariably provided with peripheral surface irregularities either in a convex (protuberance) form or a concave (groove) form, or a combination thereof, thereby providing a greater gross surface area than that of the conventional counterpart with the result that the hook forming material with such surface characteristics can be more effectively thermally set in the desired form which is retainable over prolonged service life. The hook element 10 of the invention can be coloured distinctly and uniformly when dyed for example by pad steaming as the protuberances or grooves afford increased surface tension and greater dye pick-up. Also advantageously, the hook elements 10 with protuberances alone can be fabricated with reduced amounts of thermoplastic monofilamentary material as the protuberances serve to provide increased resistance to bending stress.

Claims: A surface fastener comprising a substrate (11) in the form of a tape and hook elements (10) supported on said substrate and made of a thermoplastic monofilamentary material, characterized in that each said hook element (10) is thermally set in a hook form and has a peripheral surface configuration to enhance the thermal setting of the hook shape and to enhance the retention of said hook shape, said surface configuration comprises at least one protuberance (13) and/or at least one groove (14) extending longitudinally throughout the length of said hook element (10). A suface fastener according to claim 1, characterized in that said hook element (10) is dyed with a predetermined colour and said surface configuration affords increased surface tension and greater dye pick-up. A surface fastener according to claim 1 or 2, characterized in that said hook element (10) has a plurality of equally spaced longitudinal protuberances (13) and/or grooves (14). A surface fastener according to claim 1, 2 or 3, characterized in that said hook element (10) has alternate radially extending protuberances (13) and grooves (14). A surface fastener according to claim 1 or 2, characterized in that each of the protuberances (18) on said hook element (10) has a semicircular cross section. A surface fastener according to claim 1 or 2, characterized in that each of the protuberances (20) on said hook element (10) has a trapezoidal cross section. A surface fastener according to claim 1 or 2, characterized in that each of the grooves (19) in said hook element (10) has a semicircular cross section. A surface fastener according to claim 1 or 2, characterized in that each of the grooves (21) in said hook element (10) has a trapezoidal cross section. A surface fastener according to claim 1 or 2, characterized in that each of the protuberances (23) on said hook element (10) has a square cross section. A surface fastener according to claim 1 or 2, characterized in that each of the grooves (22) in said hook element (10) has a square cross section. A surface fastener according to claim 1 or 2, characterized in that each of the grooves (14) in said hook element (10) has a triangular cross section. A surface fastener according to claim 1 or 2, characterized in that said hook element (10) has a generally square cross section.

Inventors: YAMADA, YASUO
Applicants: YOSHIDA KOGYO K.K.
Application year: 1987
Main classification: A44B18
IPC codes: A44B18