Joint construction

Claim 1

A coupling comprising two cylindrical members, a first of which is tubular and has two circumferentially spaced inclined internal ridges formed by depressing inwardly portions of the tubular member so as to form depressions having side walls and a bottom contiguous with the wall of said tubular member and the second of which has two parts rigidly secured together, the first part of said second cylindrical member having an overall diameter corresponding to the inner diameter of said first tubular member and having a cylindrical portion secured to said second part which is of larger diameter to form a shoulder, said first part having two ears at the opposite end of said first part from said shoulder and spaced circumferentially from each other and longitudinally from said cylindrical portion to provide a cylindrical groove between said ears and said cylindrical portion, the circumferential space between said ears being greater than the length of said ridges of said first tubular member and the width of said groove being at least as great as the maximum width of said ridges, the inner walls of said ears being spaced from said shoulder by a distance approximately equal to the distance between the free end of said first tubular member and the walls of said ridges opposite to said free end so that when said second cylindrical member is inserted into said first tubular member, the ears can pass between the circumferential spaces between said internal ridges and upon relative rotation of said cylindrical members, the inner walls of the ears engage behind the adjacent walls of said internal ridges with the end of said tubular member engaging said shoulder of said second member, the walls of said internal ridges engaging said inner walls of the ears being inclined with respect to a circumferential line lying on a plane perpendicular to the center axis of said members so that as said members are relatively rotated, the end of the tubular member is drawn tightly against the shoulder of the second cylindrical member, and the opposed walls of each internal ridge being inclined toward each other as they extend inwardly from the inner wall of the tubular member in which they are formed and the wall of each ridge facing the adjoining ear being inclined radially with respect to the opposed wall of said ear so as to accentuate the wedging action between said ridges and the walls of said ears facing said ridges.