Constant pressure type fluid pump - has piston crank gear adjusted by electro-hydraulic servo valve

摘要

The pump has a cylinder containing two opposed pistons each driven by a crankshaft. Each crankshaft carries a chain wheel and an endless chain runs over both wheels. Positioning motors move the chain so as to vary the relative phase of the crankshafts and thus adjust the pump output pressure to keep it constant. The positioning motors are hydraulically operated and supplied with oil by a pump through a servo valve. An electric pressure transducer is connected to the pump discharge and provides the signal which positions the servo valve. An electronic amplifier can be placed between the transducer and the servo valve. The valve has two coils which deflect a plate controlling the oil flow to the valve cylinder.