Mark Wayne Dallas, 741765 Woodfield St, Brandon, MI 48462

4892114, Jan 9, 1990

Apr 13, 1989

7/337334

G. Earl Maroney - Clarkston MI
Mark W. Dallas - Ortonville MI
Christopher West - Clawson MI
John A. Diemer - Auburn Hills MI
Mark B. Chamberlin - Royal Oak MI

M. C. Aerospace Corporation - Lake Orion MI

G05D 700

137 87

A flow-sensing shutoff valve connectable between upstream and downstream portions of a hydraulic system comprises a valve body having pressure entrance and return exit ports connectable to the upstream portion of the system, and pressure exit and return entrance ports connectable to the downstream portion of the system. A valve element within the valve body is movable between a normally open position in which the pressure and return entrance and exit ports are connected by separate passages in the valve body, and a closed position in which the passages are blocked. Pressure and return flowmeters are adapted to sense fluid flow in the passages between the valve element and the pressure exit port and the return exit port, respectively. Flow rate signals from the flowmeters are compared in a control circuit and in response to a certain flow differential, an output signal drives an actuator which moves the valve element to closed position, isolating the downstream from the upstream portion of the hydraulic system.