Feed drive for a stitch group sewing machine

摘要

A feed drive for a stitch group sewing machine includes a cam plate serving to drive a work clamp. The cam plate is connected to a controllable clutch driven from the drive motor of the sewing machine. In order to keep the stitch length constant at varying lengths of the stitch group, the output speed of the clutch is controllable by a control device as a function of the rotational speed of the sewing machine of the transmission ratio of a gearing between the cam plate and the work clamp which determines the length of the stitch group, and of the adjusted stitch length. The stitch group to be sewn may be divided into two sections having their stitch lengths variable independently of each other, by providing that a switch responsive to a partial revolution of the cam plate corresponding to the length of the first section, alternately connects one of two potentiometers which determine the stitch length, to the control circuit of the clutch.