Joint for prestressed concrete pipe

Claim 1

A BELL AND SPIGOT JOINT FOR PRESTRESSED MOLDED CONCRETE PIPES COMPRISING A BELL AT THE END OF ONE PIPE AND A SPIGOT AT THE ADJACENT END OF AN ADJOINING PIPE, SAID ONE PIPE COMPRISING A MOLDED CONCRETE CORE INCLUDING SAID BELL, SAID BELL HAVING A SUBSTANTIALLY CYLINDRICAL INTERIOR WALL COMPRISING A SEALING SURFACE, A SHOULDER AT THE BOTTOM OF THE CYLINDRICAL INTERIOR WALL, A PRESTRESSED CONTINUOUS HELICAL COIL OF WIRE EXTENDING THROUGHOUT THE EXTERIOR OF THE CORE OF SAID ONE PIPE AND THE BELL THEREON, AN ANCHOR EMBEDDED IN THE OUTER END OF THE BELL SECURED TO SAID WIRE, AN ANCHOR FOR SAID WIRE EMBEDDED IN THE OPPOSITE EXTREMITY OF SAID ONE PIPE, AND A PROTECTING LAYER OF PLASTIC MATERIAL COVERING SAID WIRE, SAID ANCHORS AND THE CORE SURFACE, SAID ADJOINING PIPE COMPRISING A MOLDED CONCRETE CORE INCLUDING SAID SPIGOT, SAID SPIGOT COMPRISING AN ANNULAR FLANGE HAVING AN AXIAL BREADTH SUBSTANTIALLY LESS THAN THE AXIAL DEPTH OF SAID CYLINDRICAL INTERIOR WALL AND HAVING A DIAMETER LESS THAN THE DIAMETER OF SAID CYLINDRICAL INTERIOR WALL OF SAID ONE PIPE, SAID FLANGE HAVING A CONTINUOUS OUTER SURFACE OF THE MATERIAL FORMING SAID LAST CORE, A SUBSTANTIALLY CYLINDRICAL EXTERIOR SURFACE ON SAID LAST CORE, A PRESTRESSED HELICAL COIL OF WIRE ON SAID CYLINDRICAL EXTERIOR SURFACE, AN ANCHOR FOR THE WIRE IMMEDIATELY ADJACENT SAID FLANGE, AN ANCHOR FOR THE OTHER END OF SAID WIRE AT THE OPPOSITE EXTREMITY OF THE LAST CORE, A PROTECTING LAYER OF PLASTIC MATERIAL COVERING SAID LAST IDENTIFIED WIRE AND ANCHORS THEREFOR AND SAID LAST CORE, SAID PROTECTING LAYER HAVING AN EXTERIOR DIAMETER ADJACENT THE FLANGE LESS THAN THE DIAMETER OF SAID CYLINDRICAL INTERIOR WALL OF THE BELL AND PROVIDING A CLEARANCE BETWEEN SAID BELL IN THE FINISHED JOINT, MEANS FORMING A STEP IN THE OUTSIDE EDGE OF SAID FLANGE ADJACENT THE RESPECTIVE CYLINDRICAL EXTERIOR SURFACE, SAID STEP HAVING FORE AND AFT RADIAL FACES AND AN ANNULAR SEAL RING OF RESILIENT MATERIAL IN SAID STEP HAVING A SIDE SURFACE IN SEALING ENGAGEMENT WITH EACH OF SAID RADIAL FACES AND A PERIMETER PROTRUDING BEYOND THE PERIMETER OF THE FLANGE INTO A FLEXIBLE SEALING ENGAGEMENT WITH SAID CYLINDRICAL INTERIOR WALL, SAID SPIGOT HAVING A POSITION WITHIN THE BELL WHEREIN SAID FLANGE IS ADJACENT SAID SHOULDER AND SPACED A SUBSTANTIAL DISTANCE INWARDLY FROM THE OUTER END OF THE BELL, A PLURALITY OF LOOPS OF SAID LAST COIL OF WIRE HAVING A LOCATION WITHIN SAID CYLINDRICAL INTERIOR WALL AND WITHIN THE WIRE ON SAID BELL, WHEREBY TO PROVIDE AN OVERLAP OF LOOPS OF PRESTRESSED WIRES RESPECTIVELY OF THE BELL AND SPIGOT ENDS FORMING THE RESILIENT JOINT AND WHEREBY AXIAL COMPRESSION OF SAID SEAL RING BY FLUID WITHIN THE CONDUIT FORCES SAID SEAL RING AGAINST THE RADIAL FACE WHICH IS OUTWARD RELATIVE TO THE DIRECTION OF PRESSURE TO PREVENT SEEPAGE OF LIQUID TO THE REINFORCING WIRE AND TO PREVENT EXTRUSION OF THE SEAL RING.