STITCH BALANCING THREAD TENSION DEVICE-RELEASING DEVICE FOR SEWING MACHINE

PURPOSE:To hold a stitch balancing thread tension device under a non-operating condition even when a holder lifting lever is lowered as long as the holder lifting lever is raised at one point when a thread is set by providing an operation cam which synchronizes with a main shaft and has positions to put the stitch balancing thread tension device under the operating and non-operating conditions, and a holding means to hold the stitch balancing thread tension device under a non-operating condition. CONSTITUTION:An operation cam 3 which synchronizes with a main shaft 1 and has two positions to put tension discs 21, 23 under a operating and non-operating conditions, and a release claw 13 which is operated by the operation cam 3 and holds the tensions discs 21, 23 under the non-operating condition are provided. When a thread is set, the main shaft 1 is rotated by putting in and out of a cloth, a needle tip is lifted higher than a throat plate, and a holder lifting lever 45 is raised at one point. By doing these motions, even when the holder lifting lever 45 is lowered, the tension discs 21, 23 are held open and under the non-operating condition. The tension discs are held under the non-operating condition until a needle hole moves under the throat plate. For this reason, a thread is assuredly inserted between the tension discs 21, 23, and a thread setting can be performed without a mistake.