This invention relates to a valve and, more particularly to a servo operated valve responsive to low force electrical or mechanical input signals. The valve of this invention is controlled by input to a pilot valve, and is of the type used to directionally control flow from a pressure source to fluid motors, such as double-acting hydraulic cylinders, usually located at remote points. Valves of the type set forth herein are designed to operate under extremely high flows and pressures, but require a relatively low level of input force for actuation thereby permitting the use of relatively low force electro-magnetic input or low force mechanical input, such as in flexible cables. Water Control valves Low force input requirements permit the valve to be actuated by remotely positioned electrical, hydraulic or mechanical control means, which, in turn, allows the valve to be more closely positioned to the hydraulic fluid lines. The valve of this invention is an improvement in a valve of the type disclosed in U.S. Pat. Nos. 3,311,858 for TORQUE MOTOR and 3,339,573 for FLOW CONTROL VALVE, both to Eugene Bahniuk. The valve disclosed therein, in a preferred embodiment comprises a two-stage hydraulic servo or proportional valve having a low-energy electro-mechanical input in the form of a torque motor for actuating a pilot valve. The pilot valve selectively communicates an expansible chamber at one end of the main spool valve to a separate pilot valve circuit system pressure or tank pressure to vary the pressure therein. Forged Steel ValvesAn expansible chamber at the other end of the main valve is under static system pressure, whereby as the pressure is varied in the first-mentioned expansible chamber by means of selectively shifting the pilot valve, the pressure differential between the two chambers causes the main valve to shift thereby directing flow to and from the working chambers of a hydraulic piston or other working element.Displacement of the main spool is substantially proportional to the input signal to the pilot valve and is amplified with respect to the input signal.

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2011-12-01

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