Electrical discharge machining power supply circuit of the superimposed voltage type

Claim 2

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series connected, additive sources of machining power, one of said sources of relatively high voltage, low current and the other of said sources of relatively low voltage, high current, one end terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, and means for pulsing said control electrodes of said switches in unison to provide superimposed high voltage pulses of like time duration to said gap for deep hole machining operations.

Claim 3

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series connected additive sources of machining power, one of said sources of relatively high voltage, low current and the other of said sources of relatively low voltage, high current, one end terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, a drive voltage source for pulsing said control electrodes of both said switches to provide superimposed, like time duration pulses for high voltage machining, and switching means connected in series with one of said power electrodes of said second electronic switch for uncoupling it to provide relatively low voltage pulses to said gap for normal machining operation.

Claim 4

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series connected additive sources of machining power, one of said sources of relatively high voltage, low current and the other of said sources of relatively low voltage, high current, one end terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, a drive voltage source for pulsing said control electrodes of both said switches to provide superimposed, like time duration pulses for high voltage machining, and switching means connected in series with one of said power electrodes of said second electronic switch for uncoupling it to provide relatively low voltage pulses to said gap for normal machining operation.

Claim 5

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series connected sources of machining power, one of said sources of relatively high voltage, low current and the other of said sources of relatively low voltage, high current, one end terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, means for pulsing said control electrodes of both said switches to provide high voltage, finish machining, and switching means operatively connected to and controlling the control electrode of said second switching means for decoupling it from said pulsing means whereby relatively low voltage pulses are passed to said gap for normal machining operation.

Claim 6

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series connected sources of machining power, one of said sources of relatively high voltage, low current and the other of said sources of relatively low voltage, high current, one end terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, means for pulsing said control electrodes of both said switches to provide high voltage, finish machining, and switching means operatively connected to and controlling the control electrode of said second switching means for decoupling it from said pulsing means whereby relatively low voltage pulses are passed to said gap for normal machining operation.

Claim 7

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, wherein the improvement comprises a pair of series connected, additive DC sources of machining power, a first electronic switch having a control electrode and having a pair of power electrodes connected across the serial connection of one of said sources and said gap, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes operatively connected across the serial combination of both said sources and said gap, and a drive voltage source connected to the control electrodes of both said switches to turn them on and off in phase to provide superimposed voltage pulses of like time duration to said gap.

Claim 8

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, wherein the improvement comprises a pair of series connected, additive DC sources of machining power, a first electronic switch having a control electrode and having a pair of power electrodes connected across the serial connection of one of said sources and said gap, a second electronic switch having a control electrode and a pair of power electrodes, said power electrodes operatively connected across the serial combination of both said sources and said gap, and a drive voltage source connected to the control electrodes of both said switches to turn them on and off in phase to provide superimposed voltage pulses of like time duration to said gap.

Claim 9

The combination as set forth in claim 4 wherein said first mentioned switch is of relatively high current, low voltage capability and said second mentioned switch is of relatively low current, high voltage capability.

Claim 10

The combination as set forth in claim 5 wherein said first mentioned source is of relatively low voltage, high current magnitude and wherein said second mentioned source is of relatively high voltage, low current magnitude.

Claim 11

The combination as set forth in claim 6 wherein a switching means is operatively connected between said second source and said gap, said switching means operable in its closed position to provide superimposed high voltage machining and operable in its open position to provide normal voltage level machining.

Claim 12

The combination as set forth in claim 4 wherein a blocking rectifier is connected in series between said first source and said gap for protecting said first switch from the higher voltage of said combined sources during high voltage cutting.

Claim 13

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series-connected, additive DC sources of machining power, one terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, means for pulsing said control electrodes of said switches in unison to provide superimposed high voltage pulses of like time duration to said gap for deep hole machining operation, a first normally closed switching means connected in series between one of said power electrodes of said second electronic switch and said gap, and a second normally closed switching means connected in series between the control electrode of said first electronic switch and said pulsing means, said first switching means operable in its open position to provide relatively low voltage machining pulses across said gap and said second switching means operable in its open position to provide relatively high voltage machining pulses across said gap.

Claim 14

In an electrical discharge machining circuit for machining a conductive workpiece by intermittent electrical discharges across a pair of gap elements comprising a tool electrode and the workpiece separated by a dielectric coolant filled gap, a pair of series-connected, additive DC sources of machining power, one terminal of said combined sources coupled to one of said gap elements, wherein the improvement comprises a first electronic switch having a control electrode and a pair of power electrodes, said power electrodes connected across a common terminal of said sources and the other of said gap elements, a second electronic switch having a control electrode and a pair of electrodes, said power electrodes connected across said other of said gap elements and the other end terminal of said combined sources, means for pulsing said control electrodes of said switches in unison to provide superimposed high voltage pulses of like time duration to said gap for deep hole machining operation, a first normally closed switching means connected in series between one of said power electrodes of said second electronic switch and said gap, and a second normally closed switching means connected in series between the control electrode of said first electronic switch and said pulsing means, said first switching means operable in its open position to provide relatively low voltage machining pulses across said gap and said second switching means operable in its open position to provide relatively high voltage machining pulses across said gap.

Claim 15

The combination as set forth in claim 9 wherein a blocking rectifier is connected in series between one of said power electrodes of said first switch and said gap for protecting said first switch from the higher voltage of said combined sources during high voltage cutting and wherein a second blocking rectifier is connected in series between the terminal of said sources connected to said gap element and said power electrode of said first switch for protecting it from high voltage transients across said gap.

Claim 16

The combination as set forth in claim 9 wherein a third normally closed switching means is operatively connected between said pulsing means and said control electrode of said second electronic switch for interrupting drive pulses thereto, said first and third switching means conjointly operable to an open position during low voltage operation of the electrical discharge machining circuit.