Circuit arrangement for controlling sewing machine speed and for positioning sewing needle

摘要

The circuit arrangement comprises a speed control system responsive to a speed signal indicative of the rotational speed of an arm shaft driving the sewing needle in the same manner as in known arrangements. Although the circuit arrangement operates in the same manner as in the known arrangement when a foot pedal is other than a neutral position, once the foot pedal is released to be in the neutral position, particularly provided speed setting data is used where the speed setting data value decreases as the rotational angle of the arm shaft increases. With this arrangement the sewing machine is capable of operating at a speed higher than conventional one during needle positioning with the speed being sufficiently reduced just before the needle is stopped. Thus a time length required for the last stitch has been remarkably reduced, providing efficient sewing work without deteriorating positioning accuracy. The sewing machine speed damping curve slope may be manually selected so that a user can set a desired positioning time. Furthermore, by selecting a needle position signal, the needle may be stopped at either at an uppermost position or a lowermost position.