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Power source circuit for electric discharge machine

  • US 4,395,612 A
  • Filed: 02/11/1981
  • Issued: 07/26/1983
  • Est. Priority Date: 02/16/1980
  • Status: Expired due to Term
First Claim
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1. An improved power source for electric discharge machines of the type wherein a first digital oscillator drives a switching element in the charging circuit of a capacitor which repeatedly produces machining discharges through a gap between an electrode and a workpiece in order to machine the workpiece, the machining discharges occurring at a first voltage which is higher than the breakdown voltage of the gap following a machining discharge, wherein the improvement comprises:

  • first means for detecting the voltage across the gap;

    second means responsive to the first means for turning the switching element OFF at least once, for a duration longer than that determined by the first oscillator, before the gap voltage has risen to a second voltage following a machining discharge, the second voltage being higher than the breakdown voltage of the gap following a machining discharge but lower than the first voltage at which a machining discharge occurs, said second means including a second digital oscillator having a frequency lower than the first digital oscillator, a first gate having a first input responsive to the output of the first oscillator and a second input responsive to the output of the second oscillator, and third means for communicating the output of the first gate to the switching element; and

    additional means for keeping the switching element ON, following a machining discharge, as the gap voltage rises from a level above the breakdown voltage of the gap following a machining discharge to the first voltage at which a machining discharge occurs.

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