Electrochemical machining of metals

Claim 1

A PROCESS FOR CONTROLLING THE ELECTROCHEMICAL MACHINING OF METALS COMPRISING PASSING A DIRECT ELECTRIC CURRENT ACROSS A GAP FILLED WITH AN ELECTROLYTE BETWEEN A TOOL ELECTRODE AND A WORKPIECE ELECTRODE, ADVANCING ONE OF SAID ELECTRODES TOWARDS THE OTHER AT A CONTROLLED RATE, OSCILLATING ONE OF SAID ELECTRODES WITH A KNOWN AMPLITUDE OF OSCILLATION IN THE DIRECTION ACROSS SAID GAP THEREBY VARYING THE MAGNITUDE OF SAID GAP AND THEREBY CAUSING THE PRODUCTION OF A FIRST ELECTRICAL SIGNAL IN THE FORM OF AN ALTERNATING SIGNAL SUPERIMPOSED ON SAID DIRECT CURRENT, DERIVING A SECOND SIGNAL, SAID SECOND ELECTRIC SIGNAL BEING PROPORTIONAL TO THE MAGNITUDE OF SAID DIRECT CURRENT, COMPARING SAID FIRST AND SECOND SIGNALS TO DERIVE A THIRD ELECTRICAL SIGNAL, AND UTILISING SAID THIRD SIGNAL TO CONTROL THE RATE OF MUTUAL ADVANCE OF SAID ELECTRODES IN SUCH A MANNER AS TO KEEP THE RATIO OF SAID FIRST AND SECOND SIGNALS, AND HENCE THE MAGNITUDE OF SAID GAP, SUBSTANTIALLY CONSTANT.