Self sealing coupling with full flow relief valve

A self sealing quick disconnect fluid coupling fitting for use with a pressurized fluid system adapted to be selectively coupled and uncoupled to another fitting characterized by its ability to function as a pressure relief valve when uncoupled, comprising, in combination, a tubular body having an axial passage defined therein, a conduit connection end and a coupling end, coupling means defined on said body adjacent said coupling end for coupling said body to said another fitting, valve structure mounted upon said body adjacent said coupling end adapted to automatically open and close upon said body being coupled and uncoupled at said coupling end, respectively, with respect to said another fitting, said valve structure comprising first and second valve members within said passage relatively movable between open and closed positions controlling fluid flow through said passage, one of said members being fixed relative to said body, positioning means supporting the other member on said body for axial movement thereto between a closed position engaging said one member and an open position axially spaced from said one member, said other member being engaged by said another fitting upon coupling of said fittings moving said other member to said open position, said other valve member further including at least one radially extending surface exposed to fluid pressure within said passage when said other member is in said closed position so oriented to said other member that fluid pressure exerted thereon produces an axial force on said other valve member in the direction of said member open position, and spring means axially biasing said other member in the direction of said member closed position counter to the fluid pressure force, the area of said surface and the force of said spring means being preselected to permit the fluid pressure within said passage to axially displace said other valve member to said open position upon the fluid pressure reaching a predetermined value whereby fluid pressure is released through said body coupling end.