Transition fitting

Claim 1

A TRANSITION JOINT FOR CONNECTING A METAL PIPE TO A PLASTIC PIPE COMPRISING IN COMBINATION: A GENERALLY CYLINDRICAL PLASTIC ADAPTER INCLUDING A FIRST SMOOTH BORE PORTION ADAPTED TO SLIDABLY RECEIVE THE END OF A PLASTIC PIPE; A RADIALLY INWARDLY EXTENDING SHOULDER DEFINING AN ABUTMENT SURFACE AT THE INNER END OF SAID FIRST BORE, A SECOND BORE EXTENDING FROM SAID SHOULDER TO THE OTHER END OF SAID ADAPTER, SAID SECOND BORE INCLUDING AN INTERIORLY THREADED PORTION, AND FIRST, SECOND AND THIRD AXIALLY EXTENDING COUNTERBORES, SAID THREADED PORTION EXTENDING FROM ADJACENT SAID SHOULDER AXIALLY TO SAID FIRST COUNTERBORE, SAID FIRST COUNTERBORE PORTION TERMINATING AT A RADIALLY OUTWARDLY EXTENDING FIRST RADIAL WALL DEFINING THE INNER END OF SAID SECOND COUNTERBORE AND SAID SECOND COUNTERBORE TERMINATING AT A RADIALLY OUTWARDLY EXTENDING SECOND RADIAL WALL DEFINING THE INNER END OF SAID THIRD COUTERBORE; A METAL COUPLER ADAPTED TO BE JOINDED AY ONE END TO METAL PIPE AND INCLUDING AT ITS OTHER END AN EXTERIORLY THREADED PORTION OF A DIAMETER LESS THAN THE DIAMETER OF SAID FIRST COUNTEBORE PORTION THREADEDLY ENGAGED WITH SAID INTERIORLY THREADED PORTION OF SAID ADAPTER; A SMOOTH EXTERIOR SURFACE SPACED RADIALLY INWARDLY FROM THE INNER END OF BORE EXTENDING AXIALLY INWARDLY FROM THE INNER END OF SAID EXTERIORLY THREADED PORTION OF SAID COUPLER TO A RADIALLY OUTWARDLY EXTENDING SHOULDER, SAID SMOOTH EXTERIOR SURFACE INCLUDING A TAPERED PORTION TAPERING RADIALLY OUTWARDLY AS IT EXTENDS INWARDLY FROM SAID EXTERIORLY THREADED PORTION AND A CYLINDRICAL PORTION MERGING WITH SAID TAPERED PORITON, SAID RADIALLY OUTWARDLY EXTENDING SHOULDER HAVING AN ANNULAR RADIAL ABUTMENT SURFACE IN ENGAGEMENT WITH SAID SECOND RADIAL WALL OF SAID ADAPTER AND A CYLINDRICAL EXTERIOR SURFACE NESTED WITHIN SAID THIRD COUNTERBORE, THE LENGTH OF SAID METAL COUPLER BETWEEN SAID ANNULAR RADIAL ABUTMENT SURFACE AND SAID OTHER END THEREOF BEING LESS THAN THE DISTANCE BETWEEN SAID SECOND RADIAL WALL OF SAID ADAPTER AND THE SHOULDER FROM WHICH SAID SECOND BORE OF SAID ADAPTER EXTENDS; AND A RESILIENT SEALING RING IN THE ANNULAR SPACED DEFINED BY SAID FIRST RADIAL WALL AND SAID SECOND COUNTERBORE OF SAID ADAPTER AND SAID CYLINDRICAL PORTION AND SAID RADIAL ABUTMENT SURFACE OF SAID COUPLER AND COMPRESSED RADIALLY BETWEEN SAID SECOND COUNTERBORE AND SAID CYLINDRICAL PORTION TO FORM A SEAL BETWEEN SAID ADAPTER AND SAID COUPLER.