Expansible tube valves

Claim 1

In an expansible tube valve comprising: a housing with inlet and outlet flow passageways therein: a core of circular cross-section in said housing with opposite open ends thereof aligned with said flow passageways; said core having two axially spaced series of inlet and outlet slots therearound; a barrier across said core intermediate said inlet and outlet slots having a sealing surface therearound; an expansible tube on said core having an intermediate sealing portion normally snugly embracing said sealing surface; and a port in said housing for admitting pressure fluid therein against said expansible tube to construct it around said sealing surface; the improvement comprising: an annular groove with relatively sharp outer side edges extending completely around said sealing surface: and venting slots in and around said barrier, from within said annular groove to the downstream side of said barrier communicating with outlet slots; said slots tapering from said groove to a greater depth at the downstream surface of said barrier to provide gradually increasing flow passages as said expansible tube expands away from said sealing surface progressively from the upstream thereof.