Protection apparatus for electric sewing mechine

摘要

A protection apparatus for an electric sewing machine having a drive mechanism for driving the sewing machine by a motor comprises a speed detecting means for detecting a rotational speed of a shaft of the sewing machine, comparator means for comparing a rotational speed signal of the shaft of the sewing machine from the speed detecting means with an externally applied speed command signal indicative of a predetermined rotational speed of the sewing machine to determine from the comparison result whether the sewing machine is in a fault state, and invalidation means for deactivating the drive mechanism when the fault state of the sewing machine is determined by the comparison means. The protection apparatus detects the rotation of the shaft of the sewing machine while an operation command for the sewing machine is being inputted to early-detect an overload condition of the sewing machine. When an overload condition is detected, the motor and hence the sewing machine is stopped to prevent the damage of the motor.