Hydraulic pressure control valve

Abstract

A hydraulic pressure control valve, such as a pilot-operated relief valve and such as a direct-acting differential piston relief valve, having a spring chamber pressurized with fluid from a passage though a movable relief piston. The fluid within the spring chamber may be at the same pressure as that at the inlet valve closing pressure to assist a coil spring acting against the inner face of the relief piston. Inlet pressure in the valve working on an area difference between the faces of the relief piston produces the hydraulic force which is opposed by the spring to open the valve. At its other end, the spring transmits force against a movable biasing piston immediately adjacent a closed end of the spring chamber. The biasing piston provides automatic linearly increasing adjustment of the set pressure in response to inlet pressure acting over a greater net area than that of the relief piston. Inlet pressure fluid flowing into the valve moves the biasing piston toward a stop within the spring chamber to compress the spring and, in doing so, serves to buffer otherwise abrupt pressure spikes as the system is activated. Various types of pressure relief and pressure control valves in hydraulic systems are provided.