| 摘要 |
<p>1408333 Spark erosion AEG-ELOTHERM GmbH 29 Aug 1973 [1 Sept 1972] 40584/73 Heading B3V [Also in Division G3] A spark erosion machine comprises a pulse generator 1 including a triggering voltage source U 1 and a machining voltage source U 2 , a detector circuit 5, 6, 7 connected across the machining gap 4 for accumulating peak values of the pulse triggering voltage applied across the gap 4, a circuit 8, 9 for forming a mean value signal U m of the peak values, a comparator circuit 15 for delivering an output signal if the difference between the mean value and a reference value exceeds a predetermined amount and means for varying the flow rate of the dielectric through the gap 4, when an output signal from the circuit 15 occurs. The peak value of each generated machining pulse is transferred by a diode 5 to a capacitor 6 which then discharges through a resistor 7 when the spark discharge occurs. The capacitor 6 is recharged only if the peak voltage of the next pulse exceeds the voltage still present across the capacitor 6. The mean value U m of a plurality of pulses is formed by a filter comprising a resistor 8 and a capacitor 9 and is passed via a resitor 12 into a comparator circuit 15. If the mean value signal, e.g. U mII is lower than a reference voltage supplied by a potentiometer 11 indicative of contamination in the gap 4, a transistor 17 is triggered to switch on a warning lamp 20. The rate of flow of dielectric through the gap 4 is increased by the operator or, alternatively, the detector circuit automatically controls a valve in a dielectric pump and causes the gap 4 to be widened if the contamination in the gap 4 has not been removed after a time delay.</p> |
