Directional control valves for the power cylinders of operating elements of machines

Claim 1

A directional control valve providing bidirectional floating for controlling the operating elements of machines, such as roadbuilding machines and tractors or the like, said elements including a hydraulic pump, a tank supplying said pump, and a power cylinder having chambers, said control valve comprising: a valve body having circular recesses; a main valve spool being mounted in said valve body; passages communicating said circular recesses with said hydraulic pump, with said tank and with the chambers of said power cylinder; a control cavity being provided in said main valve spool; an auxiliary valve spool being mounted in said valve body; passages communicating said auxiliary valve spool with the control cavity in said main valve spool and with the circular recesses in said valve body; differential valves having throttles being installed in the passages communicating said valve body with the chambers in said power cylinder; three cavities being formed by each of Said differential valves, said last-mentioned cavities including a first cavity forming a connection between an upper end of said differential valve and the passages communicating the chambers of said power cylinder with said main valve spool, a second cavity forming a connection between the intermediate portion of said differential valve and with the supply tank; a second auxiliary valve spool being mounted in said valve body and connected to said second cavity; and spring biased non-return valves each communicating with each other, with a third cavity connected to a lower end of said differential valve and with said second auxiliary valve spool for providing a floating position.