HYDRAULIKSYSTEM MED EN PUMPE MED KONSTANT LEVERINGSMAENGDE OG MED EN FORRANGSVENTIL

An open center 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 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 also 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 the secondary work circuit and is movable between an open and a closed position to regulate the pressure of fluid discharged by the pump. Pressurized fluid from the primary work circuit is conveyed through a load signal line to the priority valve such that the pressurized fluid will urge the priority valve towards the closed position thereby assuring that adequate fluid pressure is available from the pump to the primary work circuit. The system also includes a control valve for sensing pressure variations between the fluid discharged from the pump and fluid present in the load signal line. This valve controls 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.