Servovalves and Servo-Proportional Valves
See Also: Cartridge and Servocartridge Valves
Servovalves and Servo-Proportional Valves
Servovalves and Servo-Proportional Valves are electrohydraulic, continuously acting valves that transform a changing analog or digital input signal into a stepless hydraulic output (flow or pressure).
The term servovalve describes a valve design with bushing spool assembly, characterized by high precision metering edges. The term servo-proportional describes valves with a spool-in-body design.
Moog’s valves provide precise control of position, velocity, pressure and force.
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Moog Servovalve History
In 1950 W. C. Moog, Jr. developed the first two-stage servovalve using a frictionless pilot stage. A flapper and nozzle variable orifice was used in conjunction with a fixed orifice to drive a second-stage spool in a three-way mode. The flapper-nozzle valve was driven by a torque motor, and spool position was achieved by a spring acting directly on the spool.
The advantages of thus construction were an appreciable reduction in valve threshold, and a high dynamic response because of the lower mass of the first-stage parts. Frequency response on the order of 90” at 100 Hz was possible allowing for the use of servovalves in high gain positron servos.


