JPS6425898A - Constant position stop apparatus of sewing machine - Google Patents

Abstract

PURPOSE: To discriminate whether the shape of a corner is a bent straight line or circular arc and to control the sewing speed of a sewing machine correspondingly to the arcuate shape by detecting the cloth end of a corner part at plural different positions. CONSTITUTION: A length d0 from a needle drop hole N to a first detecting position 7a and a margin X0 to be sewed up are stored in a RAM 12 by set keys 13 and 14. Cloth is arranged on the cloth feeding surface of a sewing machine 1 and the sewing machine is driven. The cloth is sewn for a cloth feeding quantity P for each stitch and the cloth end is detected by a cloth detecting means S. When the corner part is an acute angle for example, the cloth end is first detected at a third detecting point 7c, the number of stitches is counted based on the detecting signal of a main rod detector 8 and when the cloth end is detected at a second detecting point 7b, a first detection quantity feeding quantity (1)} is operated by multiplying the number of stitches at such a time and the feeding quantity P. At the same time, the number of stitches is newly counted and, when the cloth end is detected at the third detecting point 7c, a second detection quantity feeding quantity (m)} is operated by multiplying this number of stitches and the feeding quantity P. Concerning the first detection quantity 1 and second detection quantity (m), the condition of (1)-2(m)=0 is established from the proportional relation and a CPU 10 discriminates a straight line mode.