1974-08-05
1976-08-17
Miller, J D
3171485B, H01H 4732
Patent
active
039756661
ABSTRACT:
In order to provide intrinsically safe operation of an electromagnetically operated device, such as a pneumatic or hydraulic valve, a circuit in accordance with the invention includes electrical energy storage means, such as a capacitor, which is charged from a source at an intrinsically safe energy level and is subsequently at least partially discharged via switching means through an operating coil of the electromagnetic device. The capacitor is preferably charged from an intrinsically safe d.c. supply via a diode which inhibits discharging of the capacitor back into the d.c. supply. The switching means preferably operates to connect the capacitor to the operating coil when the charge on the capacitor reaches a predetermined level, as determined by a voltage sensitive device which responds to the capacitor voltage. The circuit may be used to operate a valve of the latching type having two operating coils connected in series, the capacitor being discharged through both of said coils to set the valve, the circuit including a second storage means connected in series with the coils and means for discharging the second storage means through one of the coils to reset the valve. The second storage means may be charged from the first storage means in a succession of steps.
REFERENCES:
patent: 2427751 (1947-09-01), Snyder
patent: 3121175 (1964-02-01), Vigneron
patent: 3221174 (1965-11-01), Jacobs
patent: 3382417 (1968-05-01), Armstrong
patent: 3454839 (1969-07-01), McIntosh
Miller J D
Moose Jr. Harry E.
Skinner Precision Industries, Inc.
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