Disc valve having plastic layer on resilient seating surface

Claim 1

A DISC VALVE FOR INSTALLATION BETWEEN TWO FLANGE FITTINGS COMPRISING A TUBULAR BODY; FLANGE FITTINGS DISPOSED AT EACH END OF THE BODY; AN ANNULAR SEAT MEMBER IN THE TUBULAR BODY COMPRISING A BODY OF RESILIENT, RUBBER-LIKE MATERIAL WITH A RELATIVELY THIN LAYER OF NONFRANGIBLE PLASTIC COVERING ITS INNER SURFACE AND A PORTION OF ITS ENDS, THE PLASTIC HAVING COLD FLOW CHARACTERISTICS AND BEING SOMEWHAT LESS PLIABLE AND RESILIENT THAN THE RUBBER-LIKE MATERIAL OF THE SEAT; SAID SEAT MEMBER BEING COMPRESSED BY THE FLANGE FITTINGS WHEN THE VALVE IS INSTALLED TO CAUSE THE BODY TO HOLD THE PORTIONS OF THE PLASTIC COVERING THE ENDS OF THE BODY IN SEALING ENGAGEMENT WITH THE FLANGE FITTINGS TO PROTECT THE BODY FROM THE FLUIDS FLOWING THROUGH THE VALVE; A VALVE DISC ROTATABLY MOUNTED WITHIN THE SEAT MEMBER TO COACT WITH THE SEAT MEMBER TO CONTROL THE FLOW OF FLUIDS THROUGH THE VALVE, THE OUTER DIAMETER OF THE DISC BEING LARGER THAN THE INNER DIAMETER OF THE SEAT MEMBER TO CAUSE THE DISC TO DEFORM THE BODY OF RESILIENT, RUBBER-LIKE MATERIAL AND HOLD THE LAYER OF PLASTIC IN SEALING ENGAGEMENT WITH THE DISC WHEN THE DISC IS IN A FULLY CLOSED POSITION.