Press workpiece feeder required position signal generator - has two channels delivering same signal to comparator which prevents signal evaluation if one channel fails

摘要

The required value signal supplying circuit may be used as aprt of a control circuit for positioning a work piece feeder in dependence on the operating cycle of a machine press. At least two similar signal generating devices supplied with variable values are coupled to respective inputs of a comparator which responds to a difference between the two inputs to inhibit the evaluation of the signal, e.g. by opening a switch. Pref. a test signal generator is intermittently coupled to the comparator to simulate the signal from each signal generating device, with a test circuit indicating when the comparator fails to respond.