Abstract: A load sensing priority flow control system is disclosed of the type including an engine-driven pump (11), a load sensing priority flow control valve (15), a priority load circuit (steering control valve (17) and steering cylinder (21)), and an auxiliary load circuit (19). Disposed between the excess flow output port (45) of the priority valve and the auxiliary load circuit (19) is a bypass valve arrangement (55) including a bypass valve member (57) which is biased by a downstream pressure signal (61) and spring (63) to a first position in which the auxiliary load circuit is communicated to the reservoir, to prevent loading the system and stalling the engine when the engine speed and flow from the excess flow port (45) are below a predetermined minimum. As engine speed and flow from the port (45) increase, an upstream pressure signal (59) biases the bypass valve toward a second position in which the auxiliary load circuit is blocked from communication with the reservoir, and can be pressurized and actuated.

Abstract: A load sensing controller is disclosed of the type which may be used in a hydrostatic power steering system. The controller housing includes a valving arrangement (29) and a fluid meter (31), through which fluid is delivered to a steering cylinder (15). A controller housing (63) defines a load signal port (25) which is connected to a load sensing flow control valve (39) to vary the rate of fluid delivery to the controller. During normal operation, a steering load signal is sensed downstream of a variable flow control orifice (131) and communicated through a shuttle valve assembly (151) to the load signal port (25). When the steering cylinder is subjected to an overrunning load, an increased load signal is sensed upstream of a variable orifice (136) and the shuttle valve assembly communicates this increased load signal to the load signal port to increase the rate of fluid delivery to the controller to prevent cavitation.

Abstract: A controller for fluid pressure operated devices such as power steering systems is provided. The controller is of the type having an inlet for receiving a system fluid flow, an outlet, a pair of control fluid ports for connection to a primary fluid pressure operated device and an auxiliary fluid port for connection to an auxiliary fluid pressure operated device or system. The controller includes a valve means having a primary valve member and a follow-up valve member, the valve members defining a neutral position relative to each other. A fluid meter includes a movable member coupled to the follow-up valve member. The primary and follow-up valve members cooperate with the housing to define a first flow path including the inlet, one of the control fluid ports, the fluid meter, the other of the control fluid ports, and the outlet when the valve members are relatively displaced from the neutral position.