GB813715A - Improvements in or relating to tube fittings - Google Patents

Abstract

813,715. Pipe joints. IMPERIAL BRASS MANUFACTURING CO. March 22, 1957 [March 27, 1956], No. 9424/57. Class 99(1). A metal tube fitting comprises a body 10 havin an annular seating surface 10e at one end, a nut 11 which screws on the body and has a stepped bore for receiving a tube end 20 and a camming surface 11c, and a sleeve 12 which fits over the tube and has co-operating surfaces 12b, 12c which are engaged by the seating 10e and camming surface 11c respectively so that when the nut is tightened the surfaces 10e, 12b are in fluid-tight relationship, the sleeve is prevented from rotating and a radial force constricts the end of the sleeve so that ribs on the inner surface of the sleeve are forced to bite into the pipe end provide a fluid seal. The sleeve 12 is preferably formed of low carbon steel and is provided at its inner end with a flange 12a. Its inner surface from a point approximately midway between its ends is provided with an outwardly opening frusto-conical surface 12d from which extends longitudinally spaced annular biting ribs the internal diameter of which are equal to or slightly greater than the external diameter of the tube. To prevent rotation of the sleeve and to effect a sealing engagement between surfaces 12b and 10e, the surfaces are inclined to their common axes no greater than 15 degrees; preferably 12 degrees approximately. The camming surface 11c of the nut comprises a discontinuous frusto-conical portion 11f. To minimise the tendency to rotate the sleeve 12, the surface 11d is inclined at approximately 22¢ degrees to the axis. The diameter of the surface 11e is such that the dimension between it and the tube exterior is comparable with the thickness of the sleeve nose 12i so that the ribs will have fully penetrated into the tube when the nose is radially within surface 11e. Further movement of the nut produces considerably camming force tending to collapse the tube 20, and to obtain a positive "screwed home " condition the angle of outer surface 11f is made preferably 22¢ degrees. The inclination of surface 12c to the sleeve axis is made approximately 8 degrees and the inclination of surface 12d is made approximately 5 degrees. Each of the ribs, inner 12f, middle 12g and outer 12h have frusto-conical longitudinal inner surfaces and longitudinal frusto-conical outer surfaces. The junctures of the surfaces are such that each of the ribs present an acute angle so as to consititute a sharp biting element and is so arranged that the pivotal deformation in the outer end of sleeve 12 causes only radial constriction of the rib and precludes scraping and gouging of the tube and is so formed that the inner frusto-conical surface is only slightly inclined to a plane perpendicular to the axis of the sleeve and increases from the inner to the outer rib. The inner surface of 12f may be at 50 degrees; 12g at 10 degrees and 12h at 20 degrees to a plane perpendicular to the sleeve axis. The outer surfaces of the ribs are arranged at substantial angles to planes perpendicular to the axis of the sleeve, the smallest angle being on the outer rib 12h, and are preferably 50 degrees approximately for surfaces 12f and 12g and 40 degrees approximately for 12h. The ribs are longitudinally spaced from each other, the outer rib 12h spaced from the outer end of sleeve 12 at a distance approximately equal to twice the distance between the ribs. In an example, the inner tips of the ribs are spaced apart approximately 0À03 inch and the distance inwardly of rib 12h from the outer end of sleeve 12 is approximately 0À0625 inch; the tube having an outside diameter of five-eighths inch.