An improved fluid coupling, comprising:
- a first fluid coupling part having a central through passage, said central through passage comprising a first portion with a first diameter and a second portion with a second, larger diameter;
- a second fluid coupling part adapted to extend into said central through passage;
- a tube valve, slidably and rotatably received in said central through passage between said coupling parts, for sliding movement between open and closed positions upon insertion and removal of said second coupling part, said valve comprising a third portion with a third diameter for insertion into said first portion and a fourth portion with a fourth, larger diameter for insertion into said second portion, there being a radially extending transition surface between said third and fourth portions, and a radially-extending flange extending from said fourth portion, said flange having a first face, said valve comprising an inner chamber open to said second coupling part and at least one bore extending from said inner chamber and opening into said central through passage when said valve is in said open position;
- bore seal means between said valve and said first coupling part for preventing flow of fluid through said at least one bore when said valve is in said closed position;
- spring means for acting on said first face of said radially projecting flange and biasing said valve into said closed position;
- first auxiliary seal means between said valve and said first coupling part on the opposite side of said at least one bore from said bore seal means for preventing passage of fluid between the interfacing surfaces of said valve and said first coupling part, whereby when said valve is in said open position, fluid pressure is prevented from acting on said first face of said radially projecting flange of said valve to create a force tending to close said valve;
- said first auxiliary seal means comprising an annular sealing element between said valve and said central through passage, said sealing element being disposed in an internal annular groove in said first coupling part, said annular groove being defined by first and second side walls, said second sidewall having a lesser height than said first sidewall and being downstream of said first sidewall from fluid pressure exerted within said tube valve, said first wall extending to the inner surface of said first portion of said first fluid coupling part, and said second wall extending to the inner surface of said second portion of said first fluid coupling part, said first auxiliary sealing element further being positioned to be engaged in said open position by said radially extending transition surface of said valve, whereby relative rotation between said valve and said first coupling part is facilitated in said open position.