Hydromechanical shutoff for an internal combustion engine

Abstract

An engine shutoff device includes provisions to shut down an internal combustion engine under conditions outside the normal operating limits of the engine. While the engine is idling, shutdown is initiated by fuel cutoff when engine oil pressure is below a predetermined level. As engine speed increases the low oil pressure cutoff provided in the idle range is isolated from the system so that shutdown again by fuel cutoff will occur if oil pressure drops below a second predetermined level relatively greater than first predetermined level. Engine shutdown is also initiated by fuel cutoff when either coolant temperature or lubricant temperature is excessive. The engine can be manually shut down by an emergency valve that causes cutoff of the fuel and air supply. Finally, the device initiates engine shutdown by both fuel and air cutoff when an overspeed condition occurs. The device is comprised of a self-contained fluid pump, a speed-responsive valve spool, and a series of pilot operated valves which, with appropriate passages, form a series of fluid circuits. Engine lubricating oil is pressurized by the self-contained fluid pump and is passed through the series of circuits. Appropriate pressure and temperature sensing devices along with a speed sensing device are operable upon variation of pressure, temperature, or speed in the various circuits to actuate fuel shutoff or air shutoff as required.