| 摘要 |
PROBLEM TO BE SOLVED: To incorporate a knife cutting mechanism part into an existing structure space of a sewing machine, and to enable switching between lock stitch sewing and overedge stitch sewing and work performing only the lock stitches. SOLUTION: A stich forming device of sewing machine includes: a looper clutch for forming lock stitch part and a hemstitch part by transmitting power to an upper looper and a lower looper interlocking with control for switching to overedge stitch sewing, and for forming the lock stitch part by cutting off power when the upper looper is retreated to a designated position interlocking with control for switching to lock stitch; and a looper driving part composed of the looper clutch, a clank mounted to a looper driving shaft so as to rotate, an L-shaped driving link connected to the clank, the upper looper mounting arm provided so that a middle part is pivoted on a machine frame and one end is connected to a long link end of the L-shaped looper driving link so as to support the upper link and to swing with the rotation of the clank, a lower looper driving link connected to a short link end of the L-shaped looper driving link so as to move elliptically at variable speed with rotation of the clank, and a lower looper mounting arm provided so that a middle part is pivoted by the machine frame and one end is connected to the lower looper driving link. COPYRIGHT: (C)2008,JPO&INPIT
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