Open center load sensing hydraulic system

Abstract

An open center, load sensing hydraulic system is disclosed which contains a primary work circuit and a secondary work circuit. A fixed displacement pump is fluidly connected between a reservoir and both the primary and secondary work circuits for supplying pressurized fluid thereto. The primary work circuit includes a control valve which regulates fluid flow from the pump to a primary hydraulic function and which includes a feedback mechanism connected thereto. The secondary work circuit includes a manually operable control valve for regulating fluid flow from the pump to a secondary hydraulic function. A priority valve is connected between the pump and both the primary and secondary work circuits and is movable to regulate the pressure to the primary work circuit. Pressurized signals from the primary work circuit are transmitted through a load signal lne to the priority valve and are used to move the priority valve to a position which assures that adequate pressure is always available to the primary work circuit. The system also includes a control valve for sensing pressure variations between the fluid discharged from the priority valve and the fluid present in the load signal line. This valve prevents fluid flow out of the primary hydraulic function, via the load signal line, when the pressure of the fluid discharged by the pump is less than the pressure of the fluid in the load signal line and thereby essentially eliminates kickback from the primary control valve.