GB251940A - Improvements in sewing machines - Google Patents

Abstract

251,940. Scharf, M. M. May 5, 1925, [Convention date]. Running-stitch machines; attaching umbrella covers to ribs.- A machine for sewing the covers on to the ribs of umbrellas comprises a needle which is transferred from at clamp mechanism on one side of the stitching point to a similar mechanism on the other side, the thread being thus drawn through an eye on the rib and above and below the rib which is automatically moved up and down in clamps for this purpose. The two clamp mechanisms are similar and each comprise a clamping arm 20 pressed by a spring 21 to grip the needle 10 against a block 15 to which the clamp is pivoted. The blocks 15 and clamps are mounted to be reciprocated on slide bars 28 by mechanism comprising levers 37. 38 having pin and slot connection with the blocks and carrying rollers 47, 51 which engage camtracks 46, 50 in cam-plates mounted on a shaft. The camtracks are of substantially similar form but are relatively displaced circumferentially so that the motions of the blocks are alternated. Each track has, for example tour outwardly projecting portions such as 50<a> which define the outermost positions of the clamps and needle and are successively at decreasing distances from the centre of the cam so as to allow for the shortening of the thread as it is used up in the stitching. Associated with the cam 46, 50 on the peripheries of their plates are a number of cam surfaces 55, 56 in slightly staggered relation, and these cams engage respectively rollers 63, 64 carried by a V-shaped member the arms 58, 59 of which bear studs 65, 66 adapted to engage and release the clamps at the correct moments for transferring the needle from one to the other. The umbrella rib 80 which is provided with an eye 82 is held by a clamp comprising jaws 75<a>, 75b pivoted on a support 74 on a slide-bar 70 reciprocated by a cam 77 engaging a roller 79, Fig. 9, carried by the bar. The contour of the cam 77 is designed so that the needle is passed above, below and through the eye, the thread being bound around the rib as shown in Fig. 15. Needle-threaders .-The thread-spool is carried by an arm 100 and the thread is led from the spool through an eye in a limb 111 of a forked member 110 supported by a rod 107 connected by a bar 106 to a sliding rod 105. The rod 105 is reciprocated by a pin and slot connection with an arm 115 mounted on a plate and oscillated by pins 126, 127 carried by an arm 124 connected to a spring-stressed slide 120. A pin 130 projects from the rod 107 through an inclined slot 128 in a fixed sleeve 108 so that as the rod 107 is reciprocated it and the fork 110 are also rotated so that the thread is brought down and moved across a threading hook 121 carried by the slide 120. The slide 120 is reciprocated by a lever 134, Fig. 5, connected to the slide by a pin and slot and oscillated by a cam on the cam-plate 45, the mechanism being arranged and timed that the hook is projected through the needle-eye when the needle is in its retracted position, the thread is laid across the hook and the hook then withdrawn carrying the thread through the eye. Thread-cutters.-A thread-cutter 142 is provided to cut the thread at two instants, first to cut the doubled thread carried by the needle on its last movement before returning to threading position and secondly to cut the single thread from the spool to the fabric 81. The knife 142 is carried by an arm 140 engaged by a lever 150 actuated by a cam 155 having two operative parts.