Fluid-pressure-loaded seal for butterfly valves

In a butterfly valve of the type having a valve body with a cylindrical fluid passage therethrough, and a substantially disc-shaped closure member mounted in the fluid passage for rotation between an open position and a closed position about an axis transverse to the fluid passage, and wherein the closure member further has a peripheral sealing surface, the improvement comprising a seal for tightly sealing the peripheral sealing surface of the closure member, such seal comprising:

• in the valve body, an annular groove circumscribing the fluid passage and disposed substantially in alignment with the peripheral sealing surface of the closure member when the closure member is in the closed position;
• the annular groove, in cross section, being generally T-shaped, with a substantially rectangular cavity forming the cap of the T and a narrower sleeve portion extending between that cavity and the surface of the fluid passage and forming the shank of the T;
• a resilient seat ring member disposed in and projecting from the annular groove into the fluid passage;
• the seat ring member, in cross section, having at least a first leg and a second leg such legs being joined together at a first end of each and diverging therefrom, and a stem portion projecting from the first and second legs at their joined ends;
• the second ends of the first and second legs of the seat ring member sealingly bearing against the top wall of the cap of the T defining said rectangular cavity;
• the stem portion of the seat ring member disposed in and projecting through the sleeve portion of the groove into the fluid passage;
• the stem portion of the seat ring member being smaller in cross-sectional width than the sleeve part of the groove, to permit fluid from the upstream side of the passage to enter the rectangular cavity and apply lateral pressure against a corresponding one of said first and second legs of the seat ring member;
• and
• said one of said first and second legs of the seat ring member being movable laterally toward the other of such legs responsive to fluid pressure created within the rectangular cavity thereby elastically deforming the seat ring member and urging the stem portion of the seat ring member against the peripheral sealing surface of the disc, the second ends of the first and second seat ring legs remaining in bearing relation against the top wall of the cap of the T defining said rectangular cavity, whereby fluid pressure enhances the contact pressure and, thus, the sealing action, between the seat ring member and the closure member as well as between the seat ring member and the groove.