Pipe expansion joint

Claim 1

A COUPLED FOR JOINING TOGETHER LARGE DIAMETER PIPES, COMPRISING: AN ANNULUS OF FLEXIBLE MATERIAL HAVING A CENTRAL PASSAGEWAY EXTENDING LONGITUDINALLY THERETHROUGH AND END SECTIONS TELESCOPING RESPECTIVELY OVER ADJACENT STRAIGHT PIPE SECTIONS TO BE JOINED TO PERMIT CONTINUOUS FLUID FLOW BETWEEN THE JOINED PIPES, SAID PIPE SECTIONS HAVING A GENERALLY UNINTERRUPTED OUTER SURFACE, SAID END SECTIONS OF SAID ANNULUS EACH HAVING AN INWARDLY FACING ANNULAR GROOVE ADJACENT THE OUTER UNINTERRUPTED SURFACE OF EACH PIPE SECTION; A METAL RING SECURED TO THE OUTER SURFACE OF EACH JOINED PIPE SECTION WITH EACH RING RESPECTIVELY REPOSING IN ONE OF SAID INWARDLY FACING GROOVES; SEALING MEANS IN SAID GROOVES BESIDE SAID METAL RINGS AND SEALINGLY ENGAGING RESPECTIVELY THE OUTER UNINTERRUPTED SURFACE OF SAID PIPE SECTIONS, THE METAL RING AND THE ANNULUS UNDER FLUID PRESSURE; AND METALLIC BACKING MEANS URGING SAID END SECTIONS OF SAID COUPLER RADIALLY INWARDLY AND TIGHTLY ABOUT SAID PIPE SECTIONS THROUGHOUT 360* ABOUT SAID PIPE SECTIONS, SAID BACKING MEANS BEING POSITIONED IN RADIAL ALIGNMENT WITH SAID SEALING MEANS IN SAID GROOVE TO PREVENT CHANGE IN THE SIZE OF SAID GROOVE PERMITTING SAID SEALING MEANS TO BE FORCED BY INTERNAL PRESSURE AGAINST SAID PIPE SECTION OUTER SURFACE AND SAID METAL RING, SEALING THE COUPLER TO THE PIPE SECTIONS.