Virginia Chemicals Inc.

Hisashi Ebisawa

Ernest W Schumacher

A device is provided for monitoring and controlling the above-ambient pressure in a system by comparing a net pressure force, produced by the system pressure on a pair of diaphragms having unequal areas, with a net spring force produced by a pair of opposed springs which clamp together a valve member and a valve seat in a pressure-relief member. The valve seat is connected by a passage to a port which is connected to the system pressure. While thus clamped together, the valve member and the pressure-relief member travel together through most of the total stroke created by movement of the pair of diaphragms and activate a microswitch for admitting additional fluid to the system when the system pressure is insufficient. If the net pressure force is sufficiently greater than the net spring force because of excessive system pressure, a port is opened when the valve strikes a stop and the pressure-relief member continues to move. The device is suitable for systems at below-ambient pressures by reversing the inequality of the diaphragms.

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Duncanville, TX, United States of America

Hisashi Ebisawa