Apparatus for machining through varying-frequency constant-duration pulse-controlled electric discharges

Claim 2

Apparatus for machining a part by elctric discharge comprising an electrode disposed adjacent said part so as to define a gap therebetween, a voltage source, switching means for applying successive voltage pulses to said gap, circuit means connecting said voltage source and said switching means with said electrode and said part, means for sensing the commencement of electric discharge across said gap, and timing means connected with said sensing means and said switching means and responsive to said sensing means to open said switching means to end said electric discharge a predetermined time after commencement of said electric discharge whereby electric discharge is assured with each of said pulses.

Claim 3

The invention as recited in claim 1 wherein said timing means includes means for closing said switching means to initiate a succeeding pulse a predetermined time after said switching means is opened.

Claim 4

The invention as recited in claim 1 wherein said circuit means includes a resistor connected in series with said switching means and said voltage source, and sensing means includes means for sensing the voltage across said resistor.

Claim 5

The invention as recited in claim 1 wherein said timing means includes a first monostable multivibrator having an input connected with said sensing means and an output, end a second monostable multivibrator having an input connected with the output of said first monostable multivibrator and an output connected with said switching means whereby the time delay associated with said first monostable multivibrator defines the duration of the electric discharge associated with each pulse and the time delay associated with said second monostable multivibrator defines the duration between the end of said electric discharge and the initiation of the next succeeding pulse.

Claim 6

The invention as recited in claim 1 wherein said switching means includes a semiconductor device having a control electrode connected with said timing means.

Claim 7

Apparatus for machining a part by electric discharge comprising an electrode disposed adjacent said part so as to define a gap therebetween; a source of voltage; switching means for periodically applying said voltage to said gap to define a succession of voltage pulses; means for sensing the commencement of electric discharge across said gap; control means for said switching means connected with and responsive to said sensing means and including first timing means for controlling said switching means so that the duration of the electric discharge associated with each of said voltage pulses is constant and second timing means connected with and responsive to said first timing meAns for controlling said switching means so that the period between the end of the electric discharge associated with each of said voltage pulses and the initiation of the next succeeding voltage pulse is constant; and means connecting said control means with said switching means.

Claim 8

Apparatus for machining a part by electric discharge comprising an electrode disposed adjacent said part so as to define a gap therebetween; a source of voltage; switching means for periodically applying said voltage to said gap to define a succession of voltage pulses; means for sensing the commencement of electric discharge across said gap; control means for said switching means connected with and responsive to said sensing means and including first timing means for controlling said switching means so that the duration of the electric discharge associated with each of said voltage pulses is constant and second timing means connected with and responsive to said first timing meAns for controlling said switching means so that the period between the end of the electric discharge associated with each of said voltage pulses and the initiation of the next succeeding voltage pulse is constant; and means connecting said control means with said switching means.

Claim 9

The invention as recited in claim 6 wherein said first timing means includes a first monostable multivibrator having an input connected with said sensing means and an output, and said second timing means includes a second monostable multivibrator having an input connected with the output of said first monostable multivibrator and an output connected with said switching means.

Claim 10

The invention as recited in claim 6 wherein said sensing means includes a resistor connected in series with said switching means and said electrode, and means for sensing the voltage across said resistor.

Claim 11

The invention as recited in claim 6 wherein said sensing means includes voltage sensing means and a Schmitt trigger connected with and responsive to said voltage sensing means.

Claim 12

The invention as recited in claim 6 wherein said switching means includes a semiconductor controlled switch having a control electrode, and said means connecting said control means with said switching means includes first pulse forming means connected with said first timing means and said control electrode to provide pulses to render said semiconductor controlled switch nonconductive and second pulse forming means connected with said second timing means and said control electrode to provide pulses to render said semiconductor controlled switch conductive.

Claim 13

The invention as recited in claim 6 wherein said switching means includes a plurality of transistors, each having a base, a collector and an emitter and means connecting said transistors in parallel at their collectors and emitters and connecting their bases together, and said means connecting said control means with said switching means includes pulse means connected with said second timing means and said bases for providing pulses to control the conduction of said plurality of transistors.

Claim 14

Apparatus for machining a part by electric discharge comprising an electrode disposed adjacent said part to define a gap therebetween, circuit means connected with said electrode for supplying pulses of electrical energy to cause electric discharge across said gap, means for sensing the commencement of electric discharge across said gap, timing means connecting with and responsive to said sensing means for controlling the duration of the electric discharge associated with each of said pulses and the time duration between successive ones of said pulses, and means connecting said timing means with said circuit means to control the operation thereof.

Claim 15

Apparatus for machining a part by electric discharge comprising an electrode disposed adjacent said part to define a gap therebetween, circuit means connected with said electrode for supplying pulses of electrical energy to cause electric discharge across said gap, means for sensing the commencement of electric discharge across said gap, timing means connecting with and responsive to said sensing means for controlling the duration of the electric discharge associated with each of said pulses and the time duration between successive ones of said pulses, and means connecting said timing means with said circuit means to control the operation thereof.

Claim 16

The invention as recited in claim 12 wherein said circuit means includes a first source of electrical energy, first switching means for connecting said first source across said gap, a second source of electrical energy connected across said gap and second switching means connected across said gap for shunting said second source, said timing source, said timing means includes first means connected with said sensing means and having a time delay associated therewith equal to the duration of the electric discharge associated with each of said pulses and second means connected with said first means and having a time delay associated therewith equal to the time duration between successive ones of said pulses, and said means connecting said timing means with said circuit means includes third means connecting said first timing means with said second switching means and fourth means connecting said second timing means with said first switching means.

Claim 17

The invention as recited in claim 13 wherein said sensing means includes a resistor, said first means includes a first monostable multivibrator and said second means includes a second monostable multivibrator.

Claim 18

In an electrical discharge machine for eroding material from a workpiece by passing successive pulses through an ionizable work gap defined between an electrode tool and the workpiece, a system for supplying said pulses comprising the combination of a first switch means for selectively coupling a source of ionizing potential across said work gap, a second switch means for selectively coupling a source of material eroding energy across said work gap, a detection means coupled across said gap for providing a first output signal when the gap is ionized, and a pulse generating means coupled to said second switch means and responsive to said first output signal from said detection means for actuating said second switch means to couple said source of material eroding energy across said work gap only when said work gap is ionized.

Claim 19

In an electrical discharge machine for eroding material from a workpiece by passing successive pulses through an ionizable work gap defined between an electrode tool and the workpiece, a system for supplying said pulses comprising the combination of a first switch means for selectively coupling a source of ionizing potential across said work gap, a second switch means for selectively coupling a source of material eroding energy across said work gap, a detection means coupled across said gap for providing a first output signal when the gap is ionized, and a pulse generating means coupled to said second switch means and responsive to said first output signal from said detection means for actuating said second switch means to couple said source of material eroding energy across said work gap only when said work gap is ionized.

Claim 20

The system of claim 15 wherein said pulse generating means includes a monostable pulse generator which is coupled to said second switch means and which is triggered by said first output signal to actuate said second switch means.

Claim 21

The system of claim 16 wherein said pulse generating means includes a monostable pulse generator coupled to said second switch means, a bistable circuit means coupled to said first switch means and having a first and second state, first coupling means coupling said detection means to said bistable means for switching said bistable means to said first state and actuating said first switch means in response to said second output signal, second coupling means coupling said monostable pulse generator with said detection means for actuating said second switch means in response to said first output signal, and third coupling means coupling said monostable pulse generator and said bistable means for switching said bistable means to said second state and deactuating said first switch means in response to the actuation of said second switch means.

Claim 22

The system of claim 17 wherein said source of ionizing potential has a relatively high voltage, low current characteristic and said source of material eroding energy has a relatively low voltage, high current characteristic.

Claim 23

The system of claim 18 wherein said gap has a varying ionization voltage point, said source of ionizing potential provides a voltage which is greater than the ionization voltage point of the gap, and said source of material eroding energy provides a voltage which is lower than the ionization voltage point of the gap.

Claim 24

The system of claim 17 further including a gate circuit coupled between said monostable pulse generator and said second switch means, and a reference voltage circuit coupled between said electrode tool and said gate circuit for supplying a signal to inhibit said gate circuit in response to a drop in the voltage across said gap to a point below a predetermined level to thereby deactuate said second switch means in the event of a gap short circuit and the like.

Claim 25

The system of claim 15 wherein said detection means further provides a second output signal when the work gap is deionized, and wherein said pulse generating means is coupled to said first switch means and is responsive to said second output signal for actuating said first switch means to couple said source of ionizing potential across the work gap when the work gap is deionized.

Claim 26

The system of claim 21 wherein said pulse generating means includes a bistable circuit means connected in actuating relation with said first switch means and having a first state and a second state, said bistable circuit means being coupled to said detection means and being switched to said first state in response to said second output signal for actuating said first switch means and to said second state in response to said first output signal for deactuating said first switch means.

Claim 27

The system of claim 21 further including means coupled to at least one of said electrode tool and workpiece and responsive to a drop in the voltage across the gap to a point below a predetermined level to provide an inhibiting signal and gate mEans coupled between said pulse generating means and said second switch means and responsive to said inhibiting signal for deactuating said second switch means.

Claim 28

The system of claim 15 further including means coupled to at least one of said electrode tool and workpiece and responsive to a drop in the voltage across the gap to a point below a predetermined level to provide an inhibiting signal, and gate means coupled between said pulse generating means and said means second switch means and responsive to said inhibiting signal for deactuating said second switch means.