Polarity reversal system for electrical discharge machining apparatus

Claim 2

In an electrical discharge machining apparatus for machining a conductive workpiece gap element by electrical discharges passed from a tool electrode gap element across a dielectric coolant filled gap, a periodically operated electronic output switch and a DC power source operatively connected across said gap for providing machining power pulses thereto, a system for selectively reversing the relative polarities of said gap elements, said system comprising a first switching means operatively connected between said output switch and one of said gap elements, a second switching means operatively connected between said output switch and the other of said elements, both of said switching means selectively actuable for connecting said output switch to a respective one of said gap elements and, at the same time, connecting a like terminal of said source to the other, and a control network operatively connected to one of said gap elements for providing a constant polarity control signal to a utilization means in said apparatus, said network including a third switching means operable in unison with said two first mentioned switching means to provide a first signal path direct from said gap to said utilization means, and an inverter stage, said third switching means operable to provide a second signal path from said gap through said inverter stage to said utilization means.

Claim 3

In an electrical discharge machining apparatus for machining a conductive workpiece gap element by electrical discharges passed from a tool electrode gap element across a dielectric coolant filled gap, a periodically operated electronic output switch and a DC power source operatively connected to said gap for providing machining power pulses thereto, wherein the improvement comprises a system for selectively reversing the relative polarities of said gap elements, said system comprising a first switching means operatively connected between said output switch and one of said gap elements and a second switching means operatively connected between said output switch and the other of said gap elements, both of said switching means selectively actuable for connecting said output switch to a respective one of said gap elements and, at the same time, connecting a like terminal of said source to the other, a servo feed means operably connected to one of said gap elements to provide feed movement relative to the other, and a control network coupled to the output of said gap for providing a constant polarity control signal to said servo feed means, said network including a third switching means actuable in unison with said first mentioned two switching means to provide a first signal path direct from said gap to said servo means and a second signal path from said gap through an inverter stage to said servo means.

Claim 4

In an electrical discharge machining apparatus for machining a conductive workpiece gap element by electrical discharges passed from a tool electrode gap element across a dielectric coolant filled gap, a periodically operated electronic output switch and a DC power source operatively connected to said gap for providing machining power pulses thereto, wherein the improvement comprises a system for selectively reversing the relative polarities of said gap elements, said system comprising a first switching means operatively connected between said output switch and one of said gap elements and a second switching means operatively connected between said output switch and the other of said gap elements, both of said switching means selectively actuable for connecting said output switch to a respective one of said gap elements and, at the same time, connecting a like terminal of said source to the other, a servo feed means operably connected to one of said gap elements to provide feed movement relative to the other, and a control network coupled to the output of said gap for providing a constant polarity control signal to said servo feed means, said network including a third switching means actuable in unison with said first mentioned two switching means to provide a first signal path direct from said gap to said servo means and a second signal path from said gap through an inverter stage to said servo means.

Claim 5

The combination as set forth in claim 2 wherein said servo means includes a differential amplifier wherein a reference voltage source is connected to one input of said amplifier and said constant polarity control signal is connected to the other input of said differential amplifier.

Claim 6

The combination as set forth in claim 3 wherein said differential amplifier includes a pair of alternately operable transistors and wherein an electrical control element for said servo means is connected between like power electrodes of said transistors for operation.

Claim 7

The combination as set forth in claim 2 wherein said inverter stage includes a transistor having its control electrode coupled to said gap through a sensing network and one of its principal electrodes operably coupled to said servo means.

Claim 8

In an electrical discharge machining apparatus for machining a conductive workpiece gap element by electrical dIscharges passed from a tool electrode gap element across a dielectric coolant filled gap, a periodically operated electronic output switch and a DC power source operatively connected to said gap for providing machining power pulses thereto, a system for selectively reversing the relative polarities of said gap elements, said system comprising a first switching means operatively connected between the output of said output switch and one of said gap elements and a second switching means operatively connected between said output switch and the other of said elements, said switching means each selectively actuable for connecting said output switch to a respective one of said gap elements and, at the same time connecting a like terminal of said source to the other, a protective cut-off means operably connected to said output switch to interrupt machining power pulses to the gap responsive to gap short circuit condition, and a control network coupled to the output of said gap for providing a constant polarity control signal to said cut-off means, said network including a third switching means actuable in unison with said first mentioned pair of switching means to provide a first signal path direct from said gap to said cut-off means and a second signal path from said gap through an inverter stage to said cut-off means.

Claim 9

In an electrical discharge machining apparatus for machining a conductive workpiece gap element by electrical dIscharges passed from a tool electrode gap element across a dielectric coolant filled gap, a periodically operated electronic output switch and a DC power source operatively connected to said gap for providing machining power pulses thereto, a system for selectively reversing the relative polarities of said gap elements, said system comprising a first switching means operatively connected between the output of said output switch and one of said gap elements and a second switching means operatively connected between said output switch and the other of said elements, said switching means each selectively actuable for connecting said output switch to a respective one of said gap elements and, at the same time connecting a like terminal of said source to the other, a protective cut-off means operably connected to said output switch to interrupt machining power pulses to the gap responsive to gap short circuit condition, and a control network coupled to the output of said gap for providing a constant polarity control signal to said cut-off means, said network including a third switching means actuable in unison with said first mentioned pair of switching means to provide a first signal path direct from said gap to said cut-off means and a second signal path from said gap through an inverter stage to said cut-off means.

Claim 10

The combination as set forth in claim 6 wherein said inverter stage comprises a transistor having its control electrode coupled to said gap through a sensing network and one of its principal electrodes operatively connected to said cut-off means.

Claim 11

The combination as set forth in claim 6 wherein a keying signal lead is operatively connected to said cut-off means for rendering it operable during each of said machining power pulses.

Claim 12

The combination as set forth in claim 8 wherein said cut-off means includes a cut-off electronic switch operatively connected to a drive signal source for said electronic output switch for shunting its drive signal responsive to gap short circuit condition.

Claim 13

The combination as set forth in claim 9 wherein a pulsing means and a plurality of intermediate drive stages are connected to said periodically operated electronic output switch for controlling its conduction, and wherein said keying signal lead is operatively connected to one of said drive stages and wherein an output from a control electrode of said cut-off electronic switch is coupled to shunt drive signal from the other of said drive stages.

Claim 14

In an electrical discharge machining apparatus for machining at least one conductive workpiece by electrical discharges passed from a plurality of spaced tool electrodes across a like plurality of dielectric coolant filled gaps, a periodically operated electronic output switch and a separate DC power source operatively connected to each of said gaps for providing machining power pulses thereto, wherein the improvement comprises a system for selectively reversing the relative polarity of said tool electrodes and said workpiece, said system comprising for each gap a first group of switching means, each operatively connected between the output of each of said switches and a related one of said electrodes and a second group of switching means, each operatively connected between the output of each of said switches and said workpiece, said first group of switching means selectively actuable for connecting each of said output switches to their respective tool electrode and, at the same time, connecting like terminals of said sources to said workpiece, said second group of switching means selectively actuable for connecting each of said output switches to said workpiece and at the same time connecting like terminals of said source each to a different one of said tool electrodes, a common servo feed means included to provide simultaneous feed of all of said electrodes relative to said workpiece and a control network coupled to the output of each of said gaps for providing a constant polarity control signal to said servo means, said control network including a third switching means operable in unison with said first mentioned two groups of switching means to provide a first signal path direct from said gap to said servo means and a second signal path from said gap through an inverter stage to said servo means.

Claim 15

In an electrical discharge machining apparatus for machining at least one conductive workpiece by electrical discharges passed from a plurality of spaced tool electrodes across a like plurality of dielectric coolant filled gaps, a periodically operated electronic output switch and a separate DC power source operatively connected to each of said gaps for providing machining power pulses thereto, wherein the improvement comprises a system for selectively reversing the relative polarity of said tool electrodes and said workpiece, said system comprising for each gap a first group of switching means, each operatively connected between the output of each of said switches and a related one of said electrodes and a second group of switching means, each operatively connected between the output of each of said switches and said workpiece, said first group of switching means selectively actuable for connecting each of said output switches to their respective tool electrode and, at the same time, connecting like terminals of said sources to said workpiece, said second group of switching means selectively actuable for connecting each of said output switches to said workpiece and at the same time connecting like terminals of said source each to a different one of said tool electrodes, a common servo feed means included to provide simultaneous feed of all of said electrodes relative to said workpiece and a control network coupled to the output of each of said gaps for providing a constant polarity control signal to said servo means, said control network including a third switching means operable in unison with said first mentioned two groups of switching means to provide a first signal path direct from said gap to said servo means and a second signal path from said gap through an inverter stage to said servo means.

Claim 16

The combination as set forth in claim 11 wherein said inverter stage includes an electronic switch having its control electrode coupled to said associated gap through a shunt capacitor-resistor sensing network and one of its principal electrodes coupled to the output of said network.

Claim 17

The combination as set forth in claim 12 wherein said servo means includes a differential amplifier comprising two alternately conductive electronic switches, wherein said plurality of networks are each coupled to the control electrode of one of said electronic switches through like poled diodes, and wherein a selectively settable reference voltage is connected to the control electrode of the other of said electronic switches of said differential amplifier.

Claim 18

The combination as set forth in claim 13 wherein said servo means is of the electrohydraulic type and wherein a control coil for said servo means is connected intermediate corresponding principal electrodes of said electronic switches of said differential amplifier.

Claim 19

In an electrical discharge machining apparatus for machining at least one conductive workpiece by electrical discharges passed from a plurality of spaced tool electrodes across a like plurality of dielectric coolant filled gaps, a periodically operated electronic output switch and a separate DC power source operatively connected to each of said gaps for providing machining power pulses thereto, a system for selectively reversing the relative polarity of said electrodes and of said workpiece, said system comprising for each gap a separate first switching means operatively connected between the output of each of said switches and a different one of said electrodes, a second switching means operatively connected between the output of each of said switches and said workpiece, all of said first switching means selectively actuable for connecting each of said output switches to a respective tool electrode and, at the same time, connecting a like terminal of said sources to said workpiece, all said second switching means selectively actuable for connecting each of said output switches to said workpiece and, at the same time, connecting like terminals of said sources each to a different one of said tool electrodes, a separate cut-off means operatively connected to and controlling the drive signal for each of said electronic output switches, and a control network coupled to the output of each of said gaps for providing a constant polarity control signal to its cut-off means, said control network including in each instance a third switching means operable in unison with said first mentioned pair of switching means to provide a first signal path direct from said gap to said cut-off means and a second signal path from said gap through an inverter stage to said cut-off means.

Claim 20

In an electrical discharge machining apparatus for machining at least one conductive workpiece by electrical discharges passed from a plurality of spaced tool electrodes across a like plurality of dielectric coolant filled gaps, a periodically operated electronic output switch and a separate DC power source operatively connected to each of said gaps for providing machining power pulses thereto, a system for selectively reversing the relative polarity of said electrodes and of said workpiece, said system comprising for each gap a separate first switching means operatively connected between the output of each of said switches and a different one of said electrodes, a second switching means operatively connected between the output of each of said switches and said workpiece, all of said first switching means selectively actuable for connecting each of said output switches to a respective tool electrode and, at the same time, connecting a like terminal of said sources to said workpiece, all said second switching means selectively actuable for connecting each of said output switches to said workpiece and, at the same time, connecting like terminals of said sources each to a different one of said tool electrodes, a separate cut-off means operatively connected to and controlling the drive signal for each of said electronic output switches, and a control network coupled to the output of each of said gaps for providing a constant polarity control signal to its cut-off means, said control network including in each instance a third switching means operable in unison with said first mentioned pair of switching means to provide a first signal path direct from said gap to said cut-off means and a second signal path from said gap through an inverter stage to said cut-off means.

Claim 21

The combination as set forth in claim 15 wherein a common pulser means is included and a separate drive stage is included between said pulser means and each of said periodically operated electronic output switches, and wherein a keying signal is provided to said cut-off means for rendering it operable in phase with said machining power pulses.

Claim 22

The combination as set forth in claim 16 wherein said cut-off means includes a control output coupled to a respective one of said drive stages for shunting drive signal from said electronic output switch responsive to gap short circuit condition.

Claim 23

The combination as set forth in claim 15 wherein said inverter stage includes an electronic switch having its control electrode operably coupled to said gap through a sensing network and one of its principal electrodes coupled to the output of said network.

Claim 24

The combination as set forth in claim 15 whErein said first and second switching means comprise electromagnetic relays and wherein a common operator means is included for said relays to provide like polarity connection for all of said gaps at the same time.