GB553856A - Improvements in or relating to sliding clasp fasteners - Google Patents

Abstract

553,856. Sliding-clasp fasteners. STEVENS, A. H. (Dow Chemical Co.). June 8, 1942, No. 7807. [Class 44] In a sliding-clasp fastener comprising a pair of interlocking helical coils, at least one of the coils is made from material of uniform non-circular crosssection to provide major and minor diameters and the material in each convolution or in alternate convolutions is given one or more twists to provide a part in which the minor diameter is parallel to the coil axis preceded and followed by parts in which the major diameter is parallel to the coil axis. For example, starting with tape-like material of rectangular cross-section with the major diameter parallel to the coil axis, it may be given a twist through 90 degrees in either direction, followed by a further twist through 90 degrees in the same or opposite direction. The twisting provides points at which positive interlocking between the coils occurs. Fig. 1 shows coils 3, 4 wound in opposite senses and having twists 3<1>, 4<1> which provide interlocking at both sides of each convolution. Fig. 2 shows the appearance of the coils when viewed in the direction of arrows A, B, Fig. 1. The coils may be of the same sense and the convolutions of approximately circular form, but preferably they are of oval or other flattened form, Fig. 23, which shows a convolution twisted at one side only. The flattening may be effected during or after the winding of the coil. When the twists are provided in one coil only, the co-operating coil is of uniform cross-section of any suitable shape, including circular. The coils are secured to the stringer tapes 1, 2 in any usual way and are operated by the usual slider 7. In Fig. 1 the upper ends of the coils are capped by stop members 5, 6, the lower ends being provided with a socket member 12 and a member 13 having a spike (not shown) which engages a socket in member 12 so that the stringers are separable in known manner. The fastener is operable with the slider disposed either way round and two oppositely disposed sliders may be provided. The Specification gives examples of suitable non-circular cross-sectional shapes for the material, which may be metallic, or non- metallic. The major diameter is at least 1.2 times, and preferably 1.5 times the minor diameter. Amongst suitable non-metallic materials, which may be coloured, organic plastics such as solid polymers of styrene, vinyl chloride, vinylidene chloride, methyl methacrylate and resinous co-polymers of such compounds with other unsaturated organic compounds are mentioned.