Tubing union

Claim 1

A screw-together tubing union assembly for coupliNg the ends of a pair of thin walled tubes constructed of lightweight high strength materials of the type used in the aircraft industry comprising: a pair of tubes having their ends butted together in tight nesting engagement; a sleeve positioned centrally over said tube ends and having an internal surface containing a spaced series of circumferential lands and grooves each having a longitudinal width of a dimension equal to several times the thickness of the walls of said tubes and defining a square front tooth cross section in a plane parallel to the longitudinal axis of said tubing, the external surface of said sleeve having a central portion of enlarged diameter and a pair of tapered external surfaces decreasing in diameter from a maximum near said central portion to a minimum at opposite ends of said sleeve; a housing which entirely surrounds the central portion of said sleeve and has internal threads at one longitudinal end and an internal shoulder at the other end, said housing being additionally provided with an external wrenching surface; a swaging collar positioned in abutment relation with said internal shoulder of said housing and having a tapered inner surface for complementary engagement with one of the tapered surfaces of said sleeve; an insert, externally threaded for engagement with said internal threads of said housing and having a tapered inner surface for complementary engagement with the other of said tapered surfaces of said sleeve, said insert also being provided with an external wrenching surface; wherein upon tightening of said assembly by torsion forces applied and reacted at said wrenching surfaces the sleeve is radially compressed inwardly to deform both the inner and outer surfaces of the walls of said tubes in bending by action of the lands of said sleeve in permanently reducing the diameter of the walls of said tubing adjacent said lands by an equal amount which is of the order of the thickness of said walls, and the walls of said tubes are bent outwardly into the regions occupied by said grooves such that the tubes are formed into a series of ring joints involving indentations and convolutions corresponding to said lands and grooves to thereby effect a permanent union of said tube ends such that internal pressure within said tubing will aid in tightening and securing the ring joints within the grooves to enhance the tensile strength of said union.