Power transmission

Claim 1

A hydraulic control system comprising a hydraulic actuator having an element and opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions, a pump for supplying fluid to said actuator, pilot operated meter-in valve means to which the fluid from the pump is supplied, said meter-in valve means being pilot controlled by alternately supplying fluid at pilot pressure to said meter-in valve means for controlling the direction of movement of the actuator, a pair of lines extending from said meter-in valve means to said respective openings of said actuator, a drop check valve in each said line, meter-out valve means associated with each opening of the actuator for controlling the flow out of said actuator, said meter-out valve means being pilot operated by the pilot pressure, a poppet valve associated with each said meter-out valve means, and relief valve means associated with said poppet valve and the supply pressure being supplied by said meter-in valve means to one of said actuator openings functioning as an inlet and operable when the meter-in valve means is returned to a neutral position due to an absence of pilot pressure thereon to cause the poppet valve of the meter-out valve, which is associated with the actuator opening functioning as an outlet, to function as a relief valve for the load pressure being built up at the actuator opening which is functioning as an outlet.