Electrohydraulic servovalve

Abstract

A two-stage miniature electrohydraulic servovalve including an electromagnetic positioner having a flexure tube mounted drive arm secured to and movable with an armature movable in accordance with a combined magnetic field resulting from both permanent magnets and an electrical signal fed to electromagnetic coils, a four-way hydraulic valve main valve stage including a valve body having a sleeve mounted therein with two annular, internal, axially spaced apart metering grooves, a metering spool having five lands alternating with four metering grooves positioned within the sleeve for controlled axial movement with respect to the sleeve, and end caps positioned over the ends of the sleeve and a jet pipe pilot stage including a jet pipe member secured to the end of the drive arm having a jet pipe nozzle aligned with the drive arm and a hydraulic fluid feeder passage which passage is disposed at right angles to the plane of movement of the drive arm, a resiliently mounted counterbalance positioned on the drive arm, and passages in the spool from adjacent the jet pipe nozzle to the opposite ends of the spool.