Throttling valve and seats therefor

Claim 1

A THROTTLING VALVE COMPRISING, A VALVE BODY HAVING COAXIALLY ALIGNED INLET AND OUTLET PORTS AND A CONTROL CHAMBER THEREBETWEEN, A GUIDE SEAT WITHIN SAID CHAMBER AT THE OUTLET END OF SAID INLET PORT, A THROTTLING SEAT WITHIN SAID CHAMBER AT THE INLET END OF THE OUTLET PORT, SAID SEATS BEING OF RIGID MATERIAL AND HAVING CIRCULAR PASSAGEWAYS THERETHROUGH IN COAXIAL ALIGNMENT WITH SAID PORTS AND OPPOSED ARCUATE FACES ADJACENT THE PLUG, A PLUG ROTATABLY MOUNTED WITHIN SAID CHAMBER BETWEEN SAID SEATS AND IN ENGAGEMENT WITH THE ARCUATE FACES THEREOF TO CONTROL FLUID FLOW THROUGH THE VALVE, SAID PLUG BEING CYLINDRICAL AND HAVING A TRANSAXIALLY EXTENDING CUT-OUT PORTION ADAPTED TO COACT WITH THE INLET END OF THE CIRCULAR PASSAGEWAY OF SAID THROTTLING SEAT TO DEFINE A THROTTLING ORIFICE WHILE MAINTAINING FULL FLUID FLOW THROUGH THE INLET PORT AND GUIDE SEAT, A RESILIENT, ELASTOMERIC MEMBER OVER THE ENTIRE ARCUATE FACE OF SAID THROTTLING SEAT, A CONTINUOUS, ELASTOMERIC, RESILIENT LIP PORTION INTEGRAL WITH SAID MEMBER AND PROJECTING OUTWARDLY THEREFROM TO DEFINE A STEPPED SURFACE HAVING RELATIVELY SHARP OPPOSITE EDGES AND SUCH A WIDTH THAT GREATER THAN LINE SEALING CONTACT IS MADE WITH THE CONTACTING PORTIONS OF SAID PLUG AGAINST FLUID LOSS.