Electric heating – Metal heating – Cutting or disintegrating
Patent
1982-08-02
1984-02-28
Shaw, C. C.
Electric heating
Metal heating
Cutting or disintegrating
324 61R, 324 88, B23P 102
Patent
active
044343469
ABSTRACT:
A method and apparatus for detecting the point of contact between a workpiece of electrically conductive material in a machine and an electrically conductive element movable relative to and insulated from the workpiece, such as the electrode of an electrical discharge machine, wherein in a time-varying signal, in particular sinusoidal, of predetermined amplitude and frequency is applied to the workpiece, a signal is derived from the conductive element or electrode resulting from the flow of current through the gap between the workpiece and conductive element in response to the applied signal, and the applied and derived signals are compared as to amplitude and phase angle. An indication of the comparison is provided with the result that the combination of an amplitude difference and a phase difference between the applied and derived signals indicates the status of the contact gap, respectively, between the workpiece and conductive element or electrode. The comparison and indication can be performed in an analog manner by means including a cathode ray tube providing a visual display of the amplitude and phase comparisons of the applied and derived signals as Lissajous patterns. The comparison and indication also can be performed in a digital manner by circuit means providing logical states indicating the results of the amplitude and phase comparisons of the signals, which logical states can be utilized to provide visual indications of the same.
REFERENCES:
patent: 3078415 (1963-02-01), Frelich
patent: 3299352 (1967-01-01), Carroll
patent: 3408566 (1968-10-01), Norwich
patent: 3651505 (1972-03-01), Schmidt
patent: 3725636 (1973-04-01), Toth
patent: 3970911 (1976-07-01), Schmall
patent: 4000448 (1976-12-01), Shum et al.
patent: 4241995 (1980-12-01), Takahama
patent: 4267423 (1981-05-01), Bell, Jr. et al.
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