JPS648999A - Yarn cutter - Google Patents

Abstract

PURPOSE: To stably provide an appropriate needle thread residual amount set before hand regardless of the position of a needle thread take-up by pulling out a needle thread by a movable scalpel moved in a fixed scalpel direction, cutting it by the interaction with a fixed blade and delivering the needle thread from a thread spool in a needle direction for a fixed amount by a needle thread supply means. CONSTITUTION: When sewing work is ended, a pedal 15 is operated and a cutting command is inputted, a CPU 11 controls a speed control circuit 18 and lowers the rotation speed of a sewing machine motor 19. When a needle N reaches an upper dead center based on output signals from an upper dead center detection sensor 13, the needle thread I1 is delivered simultaneously with the release of a thread clamping magnet 9, and at the point of time of delivering the needle thread for the fixed amount by a needle thread delivery roller 5 and an auxiliary roller 2, the needle thread clamping magnet 9 is turned on, the needle thread I1 is clamped and delivery is stopped. The movable scalpel is moved back and forth and both of the needle thread I1 and a needle thread I2 are cut by contact with a fixed scalpel. At the time, since the needle thread I1 is delivered in the needle direction by the needle thread supply means and no slackening or tension is present, elongation is not generated in the needle thread and a set amount is suppressed to an absolute minimum determined beforehand.