Patent GB-929514-A (GB)
Title: Sewing machine
IPC: D05B1/10
Filed: 1961-05-04
Abstract: 929,514. Sewing-machines. MAN-SEW CORPORATION. May 4, 1961 [May 20, 1960], No. 16168/61. Class 112. A sewing-machine producing a two-thread chain stitch includes a threaded needle and an oscillating threaded underlooper the thread of which is formed into a triangle for entry therein by the sewing-machine needle, a movable forked member being provided to co-operate with the under-looper thread and the needle thread in the stitch formation. The Specification describes the conversion of two lock-stitch machines into chain-stitch machines incorporating the features set out above. The machine is the two-needle machine described in Specification 802,833, one needle 14 being employed to form a lockstitch seam, the other needle 22 co-operating with a pair of loopers to form an overedge seam. The forked member comprises a thread presenter 36 (see Figs. 6 and 7) adjustably mounted in an arm 30 pivoted at 31 to a fixed bracket and oscillated in the direction of fabric feed by a link 32 pivoted to the arm at 34 and embracing a bearing 35 carried on a crank-pin 29. The crank-pin is carried on a crank formed on a shaft 12 journalled in the machine bed and driven by spur gears from the shaft 9 so that the presenter makes one oscillation for each needle bar reciprocation. Take-up.-The underlooper thread is provided with a take-up comprising a U-shaped arm 38 provided with a pair of thread openings 39, a take-up lever 40 being adjustably clamped on to the hub of the arm 30 to rock with it and deflect the thread. Underlooper.-The threaded underlooper is provided by furnishing the existing underlooper 51 for the overedge stitching with a further limb 51c either fastened to or, as shown, formed with that looper. In the modification to the secord machine, where no overedge underlooper is available, a separate drive for the underlooper (see Fig. 12) is provided. The plate previously provided on the underside of the box 60 is replaced by a casting 64 having upwardly projecting lugs 66 between which is pivoted a bracket 68 supporting idler gears 71, 72 (see also Fig. 13). The bracket 68 is adjustable by setscrews 73 to allow correct meshing of the gears 71, 72, respectively with the pinion 62 on the shaft 9 and the gear 76 fast on a cross-shaft 78 journalled in the casting 64. A crank on the end of shaft 78 is connected by a pitman 81 to an arm 86 fixed to an underlooper rock-shaft 85 journalled in the far end of an arm 82 extending from the casting. The underlooper 89 is adjustably fixed in the carrier 88 attached to the shaft 85 and oscillates transversely to the direction of feed. The presenter carrying arm 30 is pivoted to the casting. Operation of the stitch-forming parts.-As the needle rises from its lowest position the thread presenter begins to move back from its forward position with both limbs 36a, 36b about the needle, only part of the latter limb being shown in Fig. 16, the base line of the underlooper thread triangle held by the presenter being pressed against the needle to force the needle thread loop to bow out at the rear of the needle in the path of the looper 89 which enters it. As the underlooper continues to move to the right the bump 91 on the underlooper engages the needle thread and tends to push it to the right, the inner side of the limb 36b of the presenter retaining both limbs of the needle thread loop to lessen the amount of needle thread required during stitch formation. When the presenter and the looper have respectively reached their extreme rearward and rightward positions, with the ends of the presenter limbs just behind the underlooper and clear of the needle thread loop, the needle thread take-up tightens the needle thread about the underlooper body to the left of the bump 91, the looper begins to move left, pulling the needle loop with it and the presenter then moving forward. As the needle descends the left side of presenter limb 36a engages the right side of the needle thread loop to hold the loop in the path of the needle, and limb 36b continues under the underlooper thread, over the body of the underlooper, the right side of the limb 36b retaining the underlooper thread as that looper moves to the left (Fig. 14, not shown). As the presenter moves further forward corner 36c on limb 36b and corner 36e on limb 36a in turn engage the looper thread to form the base line of the triangle. The needle passes down through the triangle as it moves towards the bottom of its stroke.