Pipe coupling

Claim 1

A FLEXIBLE PIPE COUPLING COMPRISING A NIPPLE HAVING AN EXTERNAL CIRCUMFERENTIAL GROOVE WITH AT LEAST ONE WALL THEREOF SLOPING OUTWARDLY, A SLEEVE HAVING A SMOOTH INNER SURFACE OF SUBSTANTIALLY THE SAME CROSS SECTIONAL COMPLEMENTAL SHAPE AS THE EXTERIOR SURFACE OF THE NIPPLE, MEANS FOR CONNECTING SAID NIPPLE TO SAID SLEEVE WHEREBY SAID SLEEVE ENCIRCLES THE NIPPLE AND IS FREELY MOVABLE IN AXIAL RELATIONSHIP THERETO, AND A SEALING RING POSITIONED WITHIN AND PROJECTING RADIALLY OUT OF THE GROOVE, THE SEALING RING HAVING AN OUTSIDE RADIAL DIMENSION NO GREATER THAN THE INSIDE RADIAL DIMENSION OF THE SLEEVE WHERE THE SLEEVE ENCIRCLES THE GROOVE AND OTHERWISE SO CONSTRUCTED THAT THE SEALING RING IS MECHANICALLY UNCOMPRESSED BETWEEN ANY OF THE SURFACES OF THE GROOVE AND THE SLEEVE AND ABLE TO MOVE FREELY WITHIN THE CONFINES OF THE GROOVE WHEN NO PRESSURE DIFFERENTIAL EXISTS BETWEEN THE INTERIOR AND EXTERIOR OF THE COUPLING AND IS ABLE TO BE POSITIONED INTO A SEALING RELATIONSHIP BETWEEN THE SLOPING WALL OF THE GROOVE AND THE INTERIOR SURFACE OF THE SLEEVE SOLELY BY FLUID FORCES CREATED BY A PRESSURE DIFFERENTIAL BETWEEN THE INTERIOR AND EXTERIOR OF THE COUPLING; SAID SEALING RING BEING CONSTRUCTED OF A MATERIAL WHICH IS CONFORMABLE TO THE SMOOTH INTERIOR SURFACE OF THE SLEEVE AND TO THE SURFACE OF THE SLOPING WALL, EXPANDABLE, AND RESISTANT TO SUBSTANTIAL DEFORMATION WHEN ACTED ON BY FLUID FORCES CREATED BY A PRESSURE DIFFERENTIAL EXISTING BETWEEN THE INTERIOR AND EXTERIOR OF THE COUPLING.