Pipe couplings

Claim 1

A pipe coupling comprising a sleeve of resilient synthetic plastic material having a wall corrugated at each end of a cylindrical portion to define inwardly facing annular recesses for resilient sealing rings of radial thickness exceeding the depth of the recesses, characterized in that the recess at each end of said sleeve has a rectangular cross section, and in that each sealing ring comprises a body portion formed initially to fill its recess so as to afford a close fit of said body portion in the recess except for a portion corresponding to an annular groove of semicircular cross section in the sealing ring midway between the ends of the recess and adjacent the bottom wall of the recess, and an annular sealing head having at least the side facing the outer end of the recess bevelled and spaced from the outer side of the body portion, the volume of the sealing head being appreciably greater than the volume of the groove whereby, upon insertion of a pipe-end into one end of said sleeve, the sides of said body portion are further pressed against the ends of one of the recesses to resist any tendency for the sealing ring to be dislodged, and said sealing head being distorted inwardly of the sleeve for insuring good sealing contact with the pipe-end.