Hydraulic valve unit

Claim 1

A valve for use in controlling fluid flow between a source of hydraulic fluid and a hydraulically operated device, comprising a valve body; a cylindrical valve spool rotatably mounted within said valve body and having an axial bore extending thereinto from one end thereof serving as an inlet for pressurized hydraulic fluid from a source of same; one or more flow passages extending transversely through said valve spool from flow communication with said axial bore to flow communication with the cylindrical surface of the valve spool; a pair of ports circumferentially spaced in said valve body, positioned to independently register with said flow passage of the valve spool and to be in independent flow communication with a hydraulically powered device; a partial or completely circumferential groove formed in the cylindrical surface of the valve spool in longitudinally spaced relationship with said flow passage of the valve spool; an exhaust port in said valve body positioned to register with said circumferential groove; a longitudinal groove in the cylindrical surface of said valve spool and connecting with said circumferential groove; means for rotating the valve spool from a position in which one of said flow pssages that is in communication with the axial bore is in registry with one of said pair of ports in the valve body and the longitudinal groove is in registry with the other of said pair of ports, to a position in which the registries are reversed; and check valve means located in said axial bore to allow pressurized hydraulic fluid from said source of same to flow into the bore, but to prevent flow of fluid from the bore back to said source.