A HYDRAULIC CONTROL SYSTEM FOR ACTUATOR SUCH AS USED ON EARTH MOVING EQUIPMENT INCLUDING EXCAVATOR

摘要

A hydraulic control system comprising:a hydraulic actuator having opposed openings adapted to alternately function as inlets and outlets for moving the element of the actuator in opposite directions,a load sensing variable displacement pump for supplying fluid to said chamber,meter-in valve means to which the fluid from the pump is supplied,a pair of lines extending from said meter-in valve means to said respective openings of said actuator,said meter-in valve means being pilot controlled by alternately supplying fluid at pilot pressure to said meter in valve means for selectively controlling the flow of fluid to the lines and thereby direction of movement of the actuator,meter-out valve means separate from and operable independently of said meter-in 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,and means for sensing the outlet pressure being directed to the actuator when the meter-in valve means is operated and providing a pressure proportional to outlet pressure ton said meter-in valve means opposing the force of pilot pressure tending to actuate the meter-in valve means.