AUTOMATIC THREAD CUTTER IN SEWING MACHINE APPARATUS

PURPOSE:To enable respective hollow rings to be cut off to previously set lengths by performing arithmetic on a timing for cutting off thread extended at a sewing start and/or at a sewing end, to a specified length, based on stored set numbers and values measured by a sewing measuring means, and by working an automatic thread-cutting means. CONSTITUTION:Pulse signals aN synchronous with the vertical movement (number of needles N) of needle bars and an integer multiple (a) are counted, and so when an actual moving speed V is converted to the number of pulses from a sewing speed detecting means, then V=L/aN is set. A moving degree till thread is actually cut off after an automatic thread-cutter is turned ON, is set to be Lt/aN, and when a hollow ring is intended to be cut off to the length of L2 from a cloth end, then at the position of L2-(Lt/aN), via a solenoid driver 16, a thread cutting knife 14 should be ON-worked. In other wards, when a distance between a rear side cloth sensor 9 and the thread cutting knife 14 is set to be L3, then this ON-timing is applied by aN(L3-L2)/L-t, and on a timing processed in a central control circuit 1 after the cloth end passes the rear side cloth sensor 9, the thread cutting knife 14 is driven via the solenoid driver 16.