Pipe couplings

Claim 1

A pipe coupling comprising a first pipe-encircling member having a bore therein adapted to receive the pipe and having an outwardly extending projection, a recess coaxial with said bore and a sealing element disposed within the recess and of said first member to provide a seal between the member and a pipe, a second pipe-encircling member having an internal bore provided with an internal shoulder and an outwardly extending projection, a pipe-gripping collar within the bore in the second member and having an external frusto-conical surface so arranged that, upon axial movement of the second member towards the first member, the collar is contracted radially to grip the pipe, adjustable clamping means engageable with said projections on the first and second members to move the second member axially towards the first member without relative rotation between the members, a slip ring located within the bore of the second member against the internal shoulder of said second member and having an internal frusto-conical surface which coacts with the external frusto-conical surface of the collar, a washer having one side in surface-to-surface engagement with an end surface of the collar and the other side in surface-to-surface engagement with the first pipe-encircling member, the washer having a metal body, a body of rubber encapsulating the metal body of the washer, a peripheral rubber flange integral with said encapsulating body of rubber for engagement with the bore in said second member to retain the collar and the slip ring within the bore of the second member, and a resilient rubber backing ring integral with said encapsulating body of rubber which extends into and cooperates, in use, with said recess and the sealing element to prevent extrusion of the material of the sealing element under high pressure conditions.