Damping and air-purging means for relief valve

Claim 1

A relief valve comprising a housing, a valve element reciprocally mounted in said housing, a normally closed chamber in said housing being formed by a piston connected to said valve element and said housing, spring means mounted in said chamber for urging said valve element in a first direction for normally closing an inlet to prevent liquid flow through said relief valve to an outlet thereof, and damping means for damping movement of said valve element in a second direction, opposite to said first direction, when said inlet is opened to communicate with said outlet, said damping means comprising first passage means comprising a passageway through said valve element for communicating said liquid to said chamber to resist movement of said valve element in said second direction, restricted passage means, independent of said first passage means, including a clearance between said piston and said housing for automatically relieving the pressure of the liquid in said chamber when such pressure exceeds a predetermined level, and further including at least one port extending through said housing, check valve means normally closing said at least one port, and said valve means including an annular groove circumscribing the exterior of the housing and communicating with said port, and an elastic ring disposed in said groove to normally close said port.