Electrical safety control for machine tools

Claim 1

IN A MACHINE TOOL HAVING AT LEAST ONE MOVABLE OPERATING MEMBER, IN COMBINATION, A SOURCE OF ELECTRIC ENERGY; ELECTRICALLY OPERABLE CONTROL MEANS FOR STARTING AND TERMINATING THE OPERATION OF THE MOVABLE MACHINE MEMBER AND CHANGEABLE BY ELECTRICAL ENERGIZATION FROM AN IDLE POSITION TO AN OPERATION STARTING POSITION AND BY DEENERGIZATION BACK TO SAID IDLE POSITION WHEREBY MACHINE OPERATION IS TERMINATED; FIRST CIRCUIT MEANS CONNECTED BETWEEN SAID SOURCE AND SAID ELECTRICALLY OPERABLE CONTROL MEANS AND INCLUDING A PLURALITY OF RELAY SWITCH MEANS CONNECTED IN SERIES WITH EACH OTHER SO THAT SAID CONTROL MEANS CAN BE ENERGIZED ONLY WHEN ALL SAID RELAY SWITCH MEANS ARE IN CONDUCTIVE CONDITION, AND THAT SAID CONTROL MEANS ARE CAUSED TO BE IN SAID IDLE POSITION WHEN AT LEAST ONE OF SAID RELAY SWITCH MEANS IS INON-CONDUCTIVE CONDITION; SECOND CIRCUIT MEANS CONNECTED TO SAID SOURCE AND COMPRISING A PLURALITY OF PARALLEL CIRCUITS, EACH OF SAID PARALLEL CIRCUITS CONTAINING A RELAY COIL MEANS RESPECTIVELY ASSOCIATED WITH A DIFFERENT ONE OF SAID RELAY SWITCH MEANS FOR OPERATING THE LATTER, AND EACH PARALLEL CIRCUIT CONTAINING A RELAY CONTACT ASSOCIATED WITH AND OPERABLE BY A RELAY COIL MEANS LOCATED IN A RESPECTIVELY DIFFERENT ONE OF SAID PARALLEL CIRCUITS; PILOT SWITCH MEANS OPERATIVELY CONNECTED WITH SAID MOVABLE MACHINE MEMBER FOR BEING ACTUATED DEPENDING UPON A PREDETERMINED AMOUNT OF MOVEMENT OF SAID MACHINE MEMBER; DELAYED ACTION REALY MEANS ENERGIZABLE BY ACTUATION OF SAID PILOT SWITCH MEANS AND INTERRUPTING AFTER A PREDETERMINED DELAY ONE OF SAID PARALLEL CIRCUITS CONTAINING ONE OF SAID RELAY COILS SO AS TO CAUSE DEENERGIZATION OF SAID ELECTRICALLY OPERABLE CONTROL MEANS; AND PRIMARY CONTROL SWITCH MEANS CONNECTED TO SAID SOURCE AND TO AT LEAST ONE OF SAID RELAY COILS AND COOPERATING WITH ALL OF SAID SERIES-CONNECTED RELAY SWITCH MEANS IN SAID FIRST CIRCUIT MEANS FOR CAUSING THE SAME TO BE IN CONDUCTIVE CONDITION SO AS TO START OPERATION OF THE MACHINE.