Machine safety control apparatus

Claim 1

A CONTROL CIRCUIT FOR A MACHINE HAVING A REPEATING CYCLE OF OPERATION COMPRISING A SOURCE OF ELECTRICAL CURRENT HAVING A GROUND TERMINAL, CIRCUIT CONDITIONING SWITCH MEANS ACTUATED BY THE MACHINE DURING A PORTION OF A CYCLE THEREOF INCLUDING A PAIR OF SERIALLY CONNECTED SEQUENTIALLY ACTUATED MAKE-BEFORE-BREAK-SWITCH CONNECTED MEANS CONNECTING SAID BREAK SWITCH ELEMENT TO SAID GROUND TERMINAL, A PILOT RELAY ENERGIZED FROM SAID SOURCE THROUGH SAID SWITCH ELEMENTS, SECOND SWITCH NORMALLY OPEN MEANS, NORMALLY OPERATED CLOSED ON SUCCESSFUL COMPLETION OF A PORTION OF THE MACHINE CYCLE AND DURING SAID PORTION OF A CYCLE OF THE MACHINE DURING WHICH SAID CONDITIONING SWITCH IS ACTUATED AND DURING THE PERIOD WHEN SAID MAKE SWITCH ELEMENT IS MADE AND BEFORE SAID BREAK SWITCH ELEMENT IS BROKEN, SAID SECOND SWITCH MEANS BEING CONNECTED IN CIRCUIT WITH SAID PILOT RELAY AND WHEN OPERATED ENERGIZES SAID PILOT RELAY AND MAINTAINS THE ENERGIZATION THEREOF DURING THE TIME IT IS OPERATED CLOSED, A LOAD CIRCUIT ENERGIZED BY SAID PILOT RELAY, AND RESET SWITCH MEANS CONNECTED BETWEEN SAID RELAY AND SAID SOURCE FOR BYPASSING SAID MAKE-BEFORE-BREAK-SWITCH ELEMENTS AND SAID SECOND SWITCH MEANS, EFFECTIVE TO ENERGIZE SAID RELAY WHEN SAID SECOND SWITCH IS NOT OPERATED DURING THE SAID PERIOD OF OPERATION OF SAID CIRCUIT CONDITIONING SWITCH MEANS.