Patent ID: 7988127

Claim:
A valve device, comprising: a valve body having a cavity; a stopper member disposed in the cavity; a fluid passage in fluidic communication with the cavity when the valve device is in an open state; a stem coupled to the stopper member for driving the stopper member to open or close the valve; a stem aperture in the valve body for the stem to extend therethrough; a first self-expanding seal (SES) around the stem; a second SES and a third SES around the fluid passage, wherein the second SES is bounded by the third SES; a seat assembly for seating the stopper member and for forming a seal with the stopper member when the device is in a closed state, wherein the seat assembly is telescopically mounted into the cavity, wherein the second SES is an annular seal and has a substantially C-shaped cross section with an open end and an opposing closed end, and wherein the open end is substantially along a direction of the fluid passage and pointing away from the cavity such that the second SES is configured to expand in a radial direction to seal off a gap between the seat assembly and the valve body when the second SES is subject to a pressure from the fluid passage; wherein the seat assembly has a stepped recess for receiving the second SES, wherein the open end of the second SES is substantially flush with an outer surface of the valve body when the seat assembly is telescopically mounted into the cavity, and wherein the outer surface has a groove for receiving the third SES such that the third SES and the second SES are substantially concentric in a plane along the gap between the end cap and the valve body.