Welding control system

Claim 1

IN A WELDING SYSTEM OF THE TYPE IN WHICH A NONCONSUMABLE WELD ELECTRODE IS HELD IN POSITION ADJACENT TO A WORK PIECE TO PRODUCE AN ARC THEREBETWEEN, AND WHEREIN THE ELECTRODE IS HELD IN A WELDING TORCH WHICH IS SUPPORTED BY AN AUTOMATIC WELDING HEAD HAVING DRIVING MEANS FOR POSITIONING THE ELECTRODE IN ACCORDANCE WITH AN ERROR VOLTAGE APPLIED THERETO, THE COMBINATION INCLUDING, FIRST SECOND VOLTAGE SUPPLY MEANS FOR PRODUCING FIRST AND SECOND REFERENCE VOLTAGES, CONTROL MEANS RESPONSIVE TO THE ARC VOLTAGE BETWEEN THE WELDING ELECTRODE AND THE WORK PIECE FOR PRODUCING A FIRST ERROR VOLTAGE REPRESENTING THE DIFFERENCE OF SAID ARC VOLTAGE FROM SAID FIRST REFERENCE VOLTAGE, RADIATION SENSING MEANS RESPONSIVE TO THE INTENSITY OF THE WELDING ARC RADIATION FOR PRODUCING A VOLTAGE WHICH VARIES WITH SUCH RADIATION, SAID RADIATION SENSING MEANS INCLUDING A PORTION IN ENGAGEMENT WITH THE WORK PIECE TO POSITION SAIDN SENSING MEANS WITH RESPECT TO THE WELDING ARC, MEANS PRODUCING A SECOND ERROR VOLTAGE REPRESENTING THE DIFFERENCE OF SAID VOLTAGE PRODUCED BY SAID SENSING MEANS FROM SAID SECOND REFERENCE VOLTAGE, AND SWITCH MEANS FOR INITIALLY APPLYING SAID FIRST ERROR VOLTAGE TO SAID DRIVING MEANS, SAID SWITCH MEANS INCLUDING TIME DELAY MEANS CAUSING OPERATION OF SAID SWITCH MEANS TO APPLY SAID SECOND ERROR VOLTAGE TO SAID DRIVING MEANS AFTER A PREDETERMINED TIME.