Electric discharge machining method and apparatus

Claim 2

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time which is variable, means for variably adjusting individual pause times in dependence upon working voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, and said adjusting means comprising means responding to said another operative position of said second switching element to variably adjust said pause time.

Claim 3

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising, switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, and actuating means responsive to the consecution of a predetermined number of the pulse voltages putting said second switching element in the one operative position to control said adjusting means to decrease said pause time.

Claim 4

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising, switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, and actuating means responsive to the consecution of a predetermined number of the pulse voltages putting said second switching element in the one operative position to control said adjusting means to decrease said pause time.

Claim 5

An electric discharge machining apparatus comprising means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross In one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time and operable to another operative position, and actuating means responsive to the sequence of a predetermined number of the pulse voltages operating said second switching element to said another operative position to control said adjusting means to increase said pause time.

Claim 6

An electric discharge machining apparatus comprising means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross In one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time and operable to another operative position, and actuating means responsive to the sequence of a predetermined number of the pulse voltages operating said second switching element to said another operative position to control said adjusting means to increase said pause time.

Claim 7

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time to be put in another operative position, first actuating means responsive to a sequence of a predetermined number of the pulse voltages operating said second switching element to the one operative position to control said adjusting means to decrease said pause time and second actuating means responsive to a sequence of a predetermined number of the pulse voltages operating said second switching element to said another operative position to control said adjusting means to increase said pause time.

Claim 8

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time to be put in another operative position, first actuating means responsive to a sequence of a predetermined number of the pulse voltages operating said second switching element to the one operative position to control said adjusting means to decrease said pause time and second actuating means responsive to a sequence of a predetermined number of the pulse voltages operating said second switching element to said another operative position to control said adjusting means to increase said pause time.

Claim 9

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, first actuating means responsive to a sequence of a predetermined number of the pulse voltages putting said second switching element in said one operative position to control said adjusting means to decrease said pause time, and second actuating means responsive to a sequence of a predetermined number of the pulse voltages putting said second switching element in said another operative position to control said adjusting means to increase said pause time, and said adjusting means having means responding to each of the operations of either of said first and second actuating means to be controlled by a predetermined amount.

Claim 10

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, first actuating means responsive to a sequence of a predetermined number of the pulse voltages putting said second switching element in said one operative position to control said adjusting means to decrease said pause time, and second actuating means responsive to a sequence of a predetermined number of the pulse voltages putting said second switching element in said another operative position to control said adjusting means to increase said pause time, and said adjusting means having means responding to each of the operations of either of said first and second actuating means to be controlled by a predetermined amount.

Claim 11

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric disCharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, first actuating means responsive to holding of said second switching element in said another operative position for a predetermined time interval to control said adjusting means to increase said pause time, and second actuating means responsive to an increase in pause time to a predetermined value through the operation of said first actuating means to control said adjusting means to decrease said pause time.

Claim 12

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric disCharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, first actuating means responsive to holding of said second switching element in said another operative position for a predetermined time interval to control said adjusting means to increase said pause time, and second actuating means responsive to an increase in pause time to a predetermined value through the operation of said first actuating means to control said adjusting means to decrease said pause time.

Claim 13

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, first actuating means responsive to holding of said second switching element in said another operative position for a predetermined time interval to control said adjusting means to increase said pause time, and second actuating means responsive to an increase in pause time to a predetermined value through the operation of said first actuating means to control said adjusting means to decrease said pause time, an amount by which the pause time increased by said first actuating means is larger than an amount by which the pause time is decreased by said second actuating means.

Claim 14

An electric discharge machining apparatus comprising, means for holding a workpiece and a working electrode disposed in opposed relationship to said workpiece to form a working gap therebetween, means including said electrode for applying a voltage across said gap comprising a switching element for intermittently interrupting the power supply to said working gap to apply across said working gap pulse voltages each followed by a pause time, means for adjusting said pause time in accordance with voltages across said working gap, a second switching element responsive to no occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross in one operative position and responsive to both the occurrence of electric discharge across said working gap due to the application of said pulse voltages thereacross and the presence of said pause time in another operative position, first actuating means responsive to holding of said second switching element in said another operative position for a predetermined time interval to control said adjusting means to increase said pause time, and second actuating means responsive to an increase in pause time to a predetermined value through the operation of said first actuating means to control said adjusting means to decrease said pause time, an amount by which the pause time increased by said first actuating means is larger than an amount by which the pause time is decreased by said second actuating means.