| 摘要 |
1492027 Electro-erosion FRIEDRICH DECKEL AG 4 March 1975 [4 Dec 1973 23 May 1974] 56184/73 and 23145/74 Heading B3V The occurrence of arcing during electrical discharge machining is sensed by detecting the absence of a high frequency component in a discharge across the machining gap and thereupon interrupting the discharges within 20 microseconds. The gap voltage or current W is fed through a filter F whose output is connected via an amplifier A to a comparator circuit C having another input derived from a gap current detector CD. When an HF component, e.g. above 1 MHz, is absent from a discharge indicative of arcing, pulses are not supplied from the filter F to the comparator circuit C, whereupon the pulse generator G is caused to switch off for a predetermined period, e.g. below 2 sees. The electrode may also be withdrawn and the amplitude of the discharges reduced. If arcing occurs too frequently, the generator is switched off and an alarm actuated. If a short is detected across the gap by a circuit S, the discharges are interrupted for a shorter period. To test whether the monitoring circuit is functioning correctly, signals simulating the occurrence of arcing are applied randomly or regularly through contacts T 1 -T 3 whereupon a signal is applied to a gate G 2 whose other input receives a signal from the generator G upon the occurrence of a discharge therefrom. If the generator has not switched off within 20 Ásecs., a signal is supplied to an integrator I which switches it off. |
