GB911798A - Improvements in or relating to sliding clasp fasteners - Google Patents

Abstract

911,798. Stitched seams; sewing-machines. AERO ZIPP FASTENERS Ltd., and LIGHTNING FASTENERS Ltd. Feb. 24, 1961 [March 17, 1960], No. 9429/60. Class 112. [Also in Group XXV] In stitching a stringer of interconnected sliding clasp fastener elements to a tape, one or more threads are arranged to be concatenated by the stitches so as to lie on the upper surface of the fastener elements. As shown, a stringer 101 consisting of U-shaped elements 102 which straddle the edge of a tape 104 and are connected at their upper and lower ends to the adjoining elements by bridge-pieces 112 and 115 respectively, is attached to the tape by a line of stitching 103 which concatenates a pair of crossed surface threads 123, 124. The stitches are preferably, as shown, two-thread chain stitches, but may be either single-thread chain or lock stitches. The concatenated threads provide a guide for the sliding clasp 105. The tape 104 and stringer 101 are fed to a sewing-machine 131 from drums 133 and 134, respectively. The upper thread 121, the lower thread 122 and the surface threads 123, 124 are fed to the machine from spools 137. The tape 104 is fed intermittently by rollers 4 and 5. Roller 4 is carried by a shaft 6 journalled in a block 1 secured to the bed 2 of the machine. Roller 5 is journalled on an arm 10 pivoted at 11 to block 1, and is biased towards roller 4 by a spring 12. A ratchet wheel 14 on shaft 6 cooperates with a feed pawl 17 on a yoke 18 connected by a link 20 to a crank 21 on the oscillatory feed-shaft 23. The usual feed dog is removed. A stop-pawl 19 also co-operates with the ratchet wheel 14. The stringer 101 is fed intermittently by a suitably toothed wheel 24 on a shaft 25 journalled in block 1. A ratchet wheel 28 on shaft 25 co-operates with a feed pawl 32 on a yoke 31 connected by a link 36 to yoke 18. A spring-biased brake block 37 acts on shaft 25 to prevent over-run of the latter. The stringer 101 is guided to the feed wheel 24 by a reduced edge portion 41 of a guide block 40, the other edge of which is grooved to guide one edge of the tape 104. The other edge of the latter is guided by the undercut portion 441 of a guide block 44 which is slidably mounted on pins 47 projecting from a block 45 fixed to the bed 2, and is biased by springs 46 against a fixed abutment. A further tape guide block 48, situated after the sewing point and slidably mounted on pins 49 projecting from block 45, is biased by a spring 50 against a fixed abutment. The guiding edge of block 48 is formed with a bevel 51 and ramp 52 adapted to engage successive bridge portions 112, whereby the members 102 of the stringer 101 are successively pushed outwardly and stand out from the edge of tape 104. The surface threads 123, 124 issue from guide tubes 55, 56 carried on respective bars 53, 54 which are slidably mounted in block 1 and are connected by links 59, 60 to lever arms 63, 64 pivoted at 66 to a block 66 fixed to the bed plate 2. Follower rollers 73, 74 on the arms 63, 64 are biased by springs 75, 76 against eccentric circular cams 71, 72 which are mounted at 180 degrees out of phase on a rotary shaft 69. The arrangement is such that the guide tubes 55, 56 are moved to opposite extreme positions after each stitch so as to cross the threads 123, 124 in front of the needles for concatenation by the succeeding stitch. It is stated that to enable the threads 123, 124 to be positioned alternately on top, the thread guides 55, 56 could be arranged on oscillating or rotary holders, and that if the holder is rotary, the bobbins 37 for the threads would revolve around each other to avoid twisting of the threads. Specification 881,289 is referred to.