Frequency generator for electrical discharge machining

Claim 2

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source; said output means operated in response to said pulses of adjusted duration; monitoring means connected between said electrical discharge machining device and said duty cycle control means, operated in response to detection of a decrease in potential at said electrical discharge machining device, below a predetermined value to automatically adjust said duty cycle control means to vary the duration of said pulses from said pulse source whereby said output means is further operated to vary the duration of said bipolar pulses conducted to said electrical discharge machining device, from the manually determined duration; and said monitoring means being operable in response to a reduction in gap voltage at said electrical discharge machining device below a predetermined voltage substantially in excesss of zero voltage to automatically reduce the duty cycle from a predetermined normAl duty cycle by an amount proportional to the amount by which said gap voltage falls below said predetermined voltage, said monitoring means being continuously operable to monitor said gap voltage so as to continuously maintain said duty cycle at a level reduced from said normal duty cycle by an amount proportional to the amount which said gap voltage is below said predetermined voltage and to adjust said duty cycle to a predetermined minimum duty cycle if said gap voltage is reduced to zero volts.

Claim 3

A frequency generator as claimed in claim 1 wherein said train of continuous pulses produced by said pulse source are of saw-tooth wave form.

Claim 4

A frequency generator as claimed in claim 1 wherein said pulse source includes means for manually selecting the frequency of operation of said pulse source.

Claim 5

A frequency generator as claimed in claim 1 wherein said duty cycle control means include selection means manually operated to select the duration of said pulses.

Claim 6

A frequency generator as claimed in claim 4 wherein said selection means include first adjustable means for determining the basic duration of said pulses.

Claim 7

A frequency generator as claimed in claim 4 wherein said selection means include second adjustable means for determining the minimum duration of said pulses.

Claim 8

A frequency generator as claimed in claim 4 wherein said selection means include third adjustable means for determining the maximum duration of said pulses.

Claim 9

A frequency generator as claimed in claim 4 wherein said selection means include first adjustable means for determining the basic duration of said pulses, second adjustable means for determining the minimum duration of said pulses and third adjustable means for determining the maximum duration of said pulses.

Claim 10

A frequency generator as claimed in claim 4 wherein said monitoring means include potential magnitude detecting means connected between said electrical discharge machining device and said selection means, said detecting means being operated in response to detection of said potential magnitude at said device being different than a predetermined value to automatically further adjust said selection means to re-determine the duration of said pulses.

Claim 11

A frequency generator as claimed in claim 1 wherein said output means comprise a differential amplifier connected between said duty cycle control means and said electrical discharge machining device, said differential amplifier being periodically operated in response to pulses of adjusted duration from said duty cycle control means to conduct bipolar pulses to said electrical discharge machining device.

Claim 12

A frequency generator as claimed in claim 10 wherein said output means further include shaping means connected between said differential amplifier means and said electrical discharge machining device, said shaping circuit being operated to modify the waveform of said bipolar pulses conducted to said electrical discharge machining device.

Claim 13

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source, said duty cycle control means including selection means manually operated to select the duration of said pulses including adjustable means for determining the maximum duration of said pulses; and monitoring means connected between said electrical discharge machining device and said duty cycle control means, operated in response to detection of a decrease in potential at said electrical discharge machining device, below a predetermined valUe to automatically adjust said duty cycle control means to vary the duration of said pulses from said pulse source whereby said output means is further operated to vary the duration of each of said bipolar pulses conducted to said electrical discharge machining device from the manually determined duration, said monitoring means including potential magnitude detecting means connected between said electrical discharge machining device and said adjustable means, said detecting means being operated in response to detection of said potential magnitude at said device being less than a predetermined value to automatically further adjust said adjustable means to redetermine the maximum duration of said pulses.

Claim 14

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source, said duty cycle control means including selection means manually operated to select the duration of said pulses including adjustable means for determining the maximum duration of said pulses; and monitoring means connected between said electrical discharge machining device and said duty cycle control means, operated in response to detection of a decrease in potential at said electrical discharge machining device, below a predetermined valUe to automatically adjust said duty cycle control means to vary the duration of said pulses from said pulse source whereby said output means is further operated to vary the duration of each of said bipolar pulses conducted to said electrical discharge machining device from the manually determined duration, said monitoring means including potential magnitude detecting means connected between said electrical discharge machining device and said adjustable means, said detecting means being operated in response to detection of said potential magnitude at said device being less than a predetermined value to automatically further adjust said adjustable means to redetermine the maximum duration of said pulses.

Claim 15

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source; said output means operated in response to said pulses of adjusted duration and comprising a differential amplifier connected between said duty cycle control means and said electrical discharge machining device, said differential amplifier being periodically operated in response to pulses of adjusted duration from said duty cycle control means to conduct bipolar pulses to said electrical discharge machining device; monitoring means connected between said electrical discharge machining device and said duty cycle control means, operated in response to detection of a decrease in potential at said electrical discharge machining device below a predetermined value to automatically adjust said duty cycle control means to vary the duration of said pulses from said pulse source whereby said output means is further operated to vary the duration of each of said bipolar pulses conducted to said electrical discharge machining device from the manually determined duration; said output means further including shaping means connected between said differential amplifier means and said electrical discharge machining device, said shaping circuit being operated to modify the waveform of said bipolar pulses conducted to said electrical discharge machining device; and said shaping means including feedback means connected to said differential amplifier, whereby said differential amplifier operational time is reduced in response to the polarity of pulses conducted to said electrical discharge machining device.

Claim 16

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source; said output means operated in response to said pulses of adjusted duration and comprising a differential amplifier connected between said duty cycle control means and said electrical discharge machining device, said differential amplifier being periodically operated in response to pulses of adjusted duration from said duty cycle control means to conduct bipolar pulses to said electrical discharge machining device; monitoring means connected between said electrical discharge machining device and said duty cycle control means, operated in response to detection of a decrease in potential at said electrical discharge machining device below a predetermined value to automatically adjust said duty cycle control means to vary the duration of said pulses from said pulse source whereby said output means is further operated to vary the duration of each of said bipolar pulses conducted to said electrical discharge machining device from the manually determined duration; said output means further including shaping means connected between said differential amplifier means and said electrical discharge machining device, said shaping circuit being operated to modify the waveform of said bipolar pulses conducted to said electrical discharge machining device; and said shaping means including feedback means connected to said differential amplifier, whereby said differential amplifier operational time is reduced in response to the polarity of pulses conducted to said electrical discharge machining device.

Claim 17

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source; said output means operated in response to said pulses of adjusted duration and comprising a differential amplifier connected between said duty cycle control means and said electrical discharge machining device, said differential amplifier being periodically operated in response to pulses of adjusted duration from said duty cycle control means to conduct bipolar pulses to said electrical discharge machining device; shaping means connected between said differential amplifier means and said electrical discharge machining device, said shaping circuit being operated to modify the waveform of said bipolar pulses conducTed to said electrical discharge machining device; and said shaping means comprising a first switch having an input connected to said differential amplifier, and a second switch including an input connected to said first switch and an output connected to said electrical discharge machining device, said first switch being operated upon operation of said differential amplifier in response to the presence of a pulse of adjusted duration to operate said second switch to conduct pulses of a first polarity to said electrical discharge machining device, and said first switch being further operated upon further operation of said differential amplifier in response to absence of pulses of adjusted duration to operate said second switch to connect pulses of a second polarity to said electrical discharge machining device.

Claim 18

For use with an electrical discharge machining device, a frequency generator comprising: a pulse source operated to produce a continuous train of pulses at a predetermined frequency; output means connected to said electrical discharge machining device, operable to produce a continuous train of bipolar pulses for conduction to said electrical discharge machining device; duty cycle control means connected between said pulse source and said output means, initially adjustable manually to determine the duration of each of said pulses produced by said pulse source; said output means operated in response to said pulses of adjusted duration and comprising a differential amplifier connected between said duty cycle control means and said electrical discharge machining device, said differential amplifier being periodically operated in response to pulses of adjusted duration from said duty cycle control means to conduct bipolar pulses to said electrical discharge machining device; shaping means connected between said differential amplifier means and said electrical discharge machining device, said shaping circuit being operated to modify the waveform of said bipolar pulses conducTed to said electrical discharge machining device; and said shaping means comprising a first switch having an input connected to said differential amplifier, and a second switch including an input connected to said first switch and an output connected to said electrical discharge machining device, said first switch being operated upon operation of said differential amplifier in response to the presence of a pulse of adjusted duration to operate said second switch to conduct pulses of a first polarity to said electrical discharge machining device, and said first switch being further operated upon further operation of said differential amplifier in response to absence of pulses of adjusted duration to operate said second switch to connect pulses of a second polarity to said electrical discharge machining device.

Claim 21

A method as defined in claim 15 where said predetermined voltage is approximately 20 volts.

Claim 22

A method as defined in claim 15 where a time delay is provided between a change in said gap voltage and a corresponding change in said duty cycle.