Patent GB-1414789-A (GB)
Title: Sliding clasp fastener stringer
IPC: A44B19/40
Filed: 1972-11-16
Abstract: 1414789 Sliding-clasp-fasteners LIGHTNING FASTENERS LTD 26 Oct 1973 [16 Nov 1972] 52936/72 Heading E2S A sliding clasp fastener stringer comprises a carrier tape 2 of non-woven, or knitted, textile construction and a series of interconnected coupling elements formed from a single thermoplastics filament of composite construction, one portion of the filament considered in any cross-section of the filament, forming at least part of the surface of the filament, the surface of said one portion of filament having a lower crystalline melting temperature than that of the material of a second portion of the filament the series of elements having been secured to the tape by heating said one portion of filament material to a temperature at, or above, the crystalline melting temperature of said one portion but below the crystalline temperature of said second portion. In this manner, according to the invention, said one portion of filament material is fused to, or is mechanically keyed with, material of the type whilst said second portion of filament material is sensibly unaffected by the securing operation. The coupling filament 1, consisting of a series of interconnected U-shaped coupling elements 3 with interconnecting portions 3a, has a core of nylon 66 and a sheath of nylon 6 having respective crystalline melting temperatures of 264‹C and 220‹C, the tape, which is of non- woven material and consisting of a web, or mat of fibre, bonded together, also includes a proportion of plastics fibres having a core of nylon 66 and a sheath of nylon 6 with respective melting points as given above. As shown in Fig. I, with the elements 3 positioned astride an edge of the tape the latter is fed between serrated tools 6, 6a of an ultra-sonic welding apparatus to press the tape against the interconnecting portions 3a, the tools 6, 6a being heated above 220‹C but below 264‹C to cause the sheath materials of nylon 6 to fuse together without affecting the core materials of nylon 66. If the tape comprises natural textile fibres then a mechanical keying is effected between these fibres and the sheath material of the coupling elements. The longitudinal edge of a tape within the elements preferably contacts the elements of the mating stringer. In a modification, Fig. 2 not shown, a series of elements (8) are interconnected by portions (13) which lie in one plane to form a filament which is formed of a series of convolutions of generally oval cross-section. In a further modification, Fig. 3, not shown, the carrier tape (16), of warp knitted construction, has alternate longitudinally extending ribs (18) and grooves (19). The tape is knitted from yarns of nylon 66 but for the marginal edge (20) where the tape incorporates at least one yarn with a sheath of nylon 6 and a core of nvlon 66. Yarns of composite structure may be distributed through out the whole width of the zone (20). The series of elements are mounted astride, and secured to, the marginal zone (20) of the tape (16) by means of the welding apparatus shown in Fig. 1. In a fourth embodiment, Fig. 4 not shown, a warp knitted tape (24) is of the same construction as the tape (16) Fig. 3 not shown, in this case however the yarn of composite structure is provided in a different rib 18. The ultra-sonic welding apparatus may be replaced by a dielectric heating device.