Printing press synchronization

摘要

In a printing press in which a plurality of shafts in one or more printing units are each driven by individual electric motors each motor is controlled by a hybrid analogue/digital control including a pulse generator and a counter to eliminate rotational and surface speed errors between said plurality of shafts and the plate cylinders driven by said shafts. In addition to a conventional speed control loop, the counter counts up pulses from a reference pulse train and counts down pulses from an encoder driven by the motor shaft, the counter output being summed with an analogue reference.