Controller for fluid pressure operated devices

Abstract

A controller for fluid pressure operated devices such as hydrostatic power steering systems. The controller is of the type having a primary, rotatable valve member and a follow-up valve member, and further comprising a fluid meter including a metering member coupled to the follow-up valve member. The controller is of the 5-port type, having a load signal port for communicating a steering load signal and maintaining a constant pressure drop across the main control orifice of the controller. The primary and follow-up valve members define a central reference plane oriented generally perpendicular to the axes of rotation of the valve members and the various ports and passages defined by the valve members are arranged in somewhat of a mirror image of each other about the reference plane. The follow-up valve member (sleeve) includes a pair of load sensing orifices, intersected by the reference plane, and disposed to communicate to the load signal port of the controller a pressure signal from immediately downstream of the main control orifice, for either direction of relative displacement of the primary and follow-up valve member. When the valve members are in the neutral position, the load sensing orifice communicates with a drain port in the primary valve member to relieve to tank the fluid in the load sensing circuit.