Servo valve with torque feedback

Abstract

A servo valve assembly having torque feedback includes a housing and a valve spool disposed for axial translation therein. The valve spool has a plurality of lands alternating with three reduced diameter regions which cooperate with axially spaced apart inlet, return and service ports in the housing. The servo mechanism includes a piston integrally formed with the valve spool. An axial bore extends through the spool and receives a control rod having an axially extending flat which cooperates with radial passageways in the valve spool. At the end of the control rod is a torque motor which rotates bi-directionally and provides an input signal to which the servo valve assembly responds. Between the torque motor and the valve housing is a torque feedback assembly. The assembly includes a pair of cantilever spring arms each fixed at one end, the opposite ends of each of the cantilever arms coupled to a respective pair of pistons which are in communication with respective service ports. A cross member interconnects the cantilever arms adjacent the pistons. A pair of springs couple the cantilever arms to a torque arm extending radially from the control rod. In an alternate embodiment, torque feedback is provided directly from the valve spool to one of the cantilever spring arms through a pivoted, right angle crank arm.