Beer keg protective device

Claim 1

A pressure control device for disposition in a gas passage between a gas pressure source and a pressure vessel comprising: an elongated housing having a gas inlet, a gas outlet, a first chamber and a valve seat; said inlet lying in communication with said first chamber and including an element receivable therein having an axial passageway and at least one radial aperture for delivery of gas from said passageway through said aperture into said chamber, the inner end of said element comprising said valve seat; a piston in said housing, said piston having a passage therethrough in communication on one side thereof with a second chamber defined at least in part by said housing and the face of said piston, said piston being movable axially betweeen first and second positions, said second chamber lying in communication with said housing outlet; said piston having a stem defining a part of the passage through said piston, said stem having an annular end defining an inlet for the passage through said piston; a spring for biasing said piston into said first position; said piston in said first position establishing communication between said first chamber and the passage in said piston for permitting flow of gas from said housing inlet through said chamber, the passage in said piston, and the second chamber to said outlet for pressures in said second chamber less than or equal to a predetermined pressure; said piston, in response to a gas pressure in said second chamber in excess of the predetermined pressure and acting thereon adjacent said outlet, being movable against the bias of said spring into said second position to seal said annular end of the piston stem against said seat thereby to preclude transmission of gas through the passage in said piston; said spring biasing said piston for movement from said second position to said first position, said piston being movable into said first position by said spring in response to a pressure in said second chamber less than or equal to the predetermined pressure, means for venting said first chamber externally of said housing in response to a pressure therein greater than the predetermined pressure, said venting means including an annular member forming an outer wall portion for said first chamber and movable axially in said housing between first and second positions, said member in said first position forming a seal with said housing for precluding venting said first chamber, means for biasing said member into said first position, means carried by said member and responsive to a pressure in said first chamber greater than said predetermined pressure for moving said member axially against said biasing means into said second position to vent said first chamber between said member and said housing; means cooperable between said housing and said element for adjusting the axial position of said element in said housing inlet and hence the axial spacing between said valve seat and the annular end of said stem in said first position of said piston, and a check valve carried by said housing adjacent said outlet and downstream of said piston for precluding backflow through said device, said check valve including a seat and a flexible member having an opening therethrough, said flexible member being downstream of said seat and engageable thereagainst to seal about said opening.