US 4,236,057 AGranted

Apparatus for detecting gap conditions in EDM processes with monitoring pulses

AssigneeInoue-Japax Research Incorporated

InventorKiyoshi Inoue

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Abstract

Apparatus for controlling an electric discharge machining process in which machining pulses are applied across a machining gap with a pulse duration and peak current preselected to attain a predetermined machining consequence or result. At least one monitoring pulse is interposed in the succession of machining pulses and is time-spaced from and totally independent of the machining pulses while being dimensioned to give rise to a current pulse in the machining gap. The current pulse is measured as to at least one characteristic and the gap condition is determined in response to this measurement.

Claims2

Dependent claims

An apparatus for detecting gap conditions in EDM processes, which comprises:

(a) means for applying across a machining gap a succession of machining pulses, comprising a first electronic switch connected in series with a DC source and said gap and a pulser for intermittently energizing said first switch;
(b) means for presetting a pulse duration and peak current of said machining pulses, including first variable resistor means connected in series with said first switch, said DC source and said gap;
(c) means for interposing at least one monitoring pulse into said succession of machining pulses, including a second electronic switch connected in parallel with said first electronic switch in series with said DC source and said gap and energizable by said pulser;
(d) means for presetting a pulse duration and peak current of said monitoring pulses, including second variable resistor means connected in series with said second switch, said DC source and said gap;
(e) means for measuring a characteristic of a gap current pulse resulting from said monitoring pulse to classify it into one of at least two categories;
(f) means responsive to the last-mentioned means for indicating the gap condition;
(g) an AND gate having a first input terminal connected to the output of said pulser and an output connected for energizing said first electronic switch;
(h) a counter for counting a preset number of output pulses from said pulser for resetting thereupon while providing a first timing signal;
(i) a first timer adapted to actuate in response to first timing signal to provide a first signal pulse of a predetermined duration;
(j) a second timer triggerable upon termination of said first duration to provide a second signal pulse of a predetermined second duration, said second timer being connected for energization of said second electronic switch thereby to produce said monitoring pulse;
and
(k) gate means connected between said second timer and the second input terminal of said AND gate for disabling the latter in the presence of said second signal pulse.

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Dependencies are inferred from the claim text.

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Abstract

An apparatus for detecting gap conditions in EDM processes, which comprises:

(a) means for applying across a machining gap a succession of machining pulses, comprising a first electronic switch connected in series with a DC source and said gap and a pulser for intermittently energizing said first switch;
(b) means for presetting a pulse duration and peak current of said machining pulses, including first variable resistor means connected in series with said first switch, said DC source and said gap;
(c) means for interposing at least one monitoring pulse into said succession of machining pulses, including a second electronic switch connected in parallel with said first electronic switch in series with said DC source and said gap and energizable by said pulser;
(d) means for presetting a pulse duration and peak current of said monitoring pulses, including second variable resistor means connected in series with said second switch, said DC source and said gap;
(e) means for measuring a characteristic of a gap current pulse resulting from said monitoring pulse to classify it into one of at least two categories;
(f) means responsive to the last-mentioned means for indicating the gap condition;
(g) an AND gate having a first input terminal connected to the output of said pulser and an output connected for energizing said first electronic switch;
(h) a counter for counting a preset number of output pulses from said pulser for resetting thereupon while providing a first timing signal;
(i) a first timer adapted to actuate in response to first timing signal to provide a first signal pulse of a predetermined duration;
(j) a second timer triggerable upon termination of said first duration to provide a second signal pulse of a predetermined second duration, said second timer being connected for energization of said second electronic switch thereby to produce said monitoring pulse;
and
(k) gate means connected between said second timer and the second input terminal of said AND gate for disabling the latter in the presence of said second signal pulse.

9 more elements