Hydraulic system with air-venting arrangement

Claim 1

In a hydraulic system, a combination comprising a source of pressurized hydraulic fluid; a user; a valve housing having a bore defined by an inner surface; a valve body mounted in said bore and subdividing the same into an inlet compartment and an outlet compartment, said valve body having an outer circumferential surface in sliding sealing contact with said inner surface and a channel forming a throttling gap and establishing the only communication between said compartments; inlet means communicating said inlet compartment with said source; outlet means communicating said outlet compartment with said user; venting means communicating said outlet compartment with the ambient atmosphere; biasing means urging said valve body toward an open position in which said outlet compartment communicates with said venting means, the throttling effect of said throttling gap resulting in a pressure differential across and displacement of said valve body into a sealing position in which said outer circumferential surface prevents communication between said outlet compartment and said venting means so that the hydraulic fluid passes from said outlet compartment through said outlet means to said user; control valve means in said outlet means operative for establishing communication between said outlet compartment and said user when said valve body is in said sealing position thereof and for preventing such communication upon return of said valve body into said open position in response to cessation of flow of the hydraulic fluid through said throttling gap; and means for actuating said control valve means so as to establish communication between said user and said outlet compartment when said valve body is in said open position thereof so as to vent the spent hydraulic fluid through said venting means.