Patent ID: 6966537

Claim:
A valve comprising: a valve body having a closure member and a closure member chamber therein, said valve body defining inlet and outlet passages extending through said valve body in communication with said closure member chamber to define a flow path through said valve body, said valve body having a respective pocket surrounding said inlet and outlet passages adjacent to said closure member chamber; a telescoping seat assembly in each of said pockets recesses, each said telescoping seat assembly comprising, an outer seat element for sealing within said pocket of said valve body, an inner seat element relatively moveable with respect to said outer seat element for sealing engagement with said closure member, said outer seat element and said inner seat element defining surfaces therebetween whereby pressure in at least one of said inlet and outlet passages acting thereon during operation of said valve urges said outer seat element to move relatively away from said inner seat element to enhance respective sealing with said pocket and said closure member, and a seal disposed in a groove within at least one of said outer seat element or said inner seat element, said groove comprising therein a tapered surface such that said seal is moveable along said tapered surface, whereby pressure acting on a first side of said seal produces a force on said seal which wedges said seal into a sealing engagement position, said seal in said sealing engagement position being positioned so as to seal at least one between said outer seat element and said pocket or between said outer seat element and said inner seat element, and pressure acting on an opposite second side moves said seal along said tapered surface out of said sealing engagement position.