Machining by sparking

Claim 1

A SPARK-MACHINING APPARATUS FOR PRODUCING PERFORATIONS OF SMALL CROSS-SECTION IN A METALLIC WORKPIEVE COMPRISING A TANK ADAPTED TO CONTAIN A DIELECTRIC LIQUID, MEANS FOR SUPPORTING SAID WORKPIECE WITHIN SAID TANK, TWO SETS OF WIRE ELECTRODES OF SMALL CROSS-SECTION HAVING THE ENDS THEREOF COOPERATING WITH SAID WORKPIECE, EACH SET BEING INSULATED FROM THE OTHER, A COMMON CARRIER FOR SAID ELECTRODES, A SINGLE POWER SOURCE CONNECTED THROUGH A SEPARATE VOLTAGE-DROPPING IMPEDANCE TO A SEPARATE SPARK DISCHARGE CIRCUIT CONNECTED BETWEEN EACH SET OF WIRE ELECTRODES AND SAID WORKPIECE TO GENERATE SPARK DISCHARGES BETWEEN SAID ENDS OF SAID WIRE ELECTRODES AND SAID WORKPIECE TO DISINTEGRATE THE METAL OF THE WORKPIECE AT THE POINTS OF SAID DISCHARGES, AND MEANS FOR CONTROLLING THE MOVEMENT OF SAID CARRIER TO MAINTAIN SUBSTANTIALLY CONSTANT THE DISPLACEMENT OF SAID ENDS OF THE ELECTRODES FROM THE PART OF THE WORKPIECE UNDERGOING MACHINING COMPRISING AN ELECTRIC MOTOR WHICH IS VARIABLE CONTROLLED THROUGH SEPARATE BLOCKING RECTIFIERS BY THE AVERAGE SPACINGS OF THE ENDS OF EITHER SET OF ELECTRODES FROM THE OPERATION OF THE WORKPIECE UNDERGOING MACHINING.