| 摘要 |
PURPOSE:To effectively operate a d.c. type positioning and detecting discharge gap sensor by connecting a switch means in series to an electrocorrosion preventing inductance, and by opening and closing the switch means in accordance with a discharge instruction so that the inductance is made to be not effective before initiation of electrical discharge. CONSTITUTION:An oscillator 10 delivers a high frequency signal A in accordance with an electric discharge processing instruction B so as to control a power source 4, and therefore, a high frequency intermittent voltage is applied across the electrical discharge gap between an electrode 1 and a workpiece 2. A switching means 8 is closed, following up the electric discharge processing instruction B, and an inductance 6 is connected in parallel to the electric discharge gap in order to exhibit an electrocorrosion preventing function. However, the inductance 6 is opened before the time when the electric discharge process is initiated, so that it is isolated from the circuit of a discharge gap sensor 7 whose operation is therefore not hindered by the inductance 6. No signal is issued by a process time blockage circuit 9 including an AND circuit for a reverse signal of the high frequency signal A and an output signal from the discharge gap sensor 7 although the gap is decreased by the inductance 6 during processing.
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