Dual seal butterfly valve

Claim 1

In a butterfly valve having a valve body presenting a flow through passageway therein; a spherical segment contour in the flow through passageway of the valve body; a valve disc supported within the spherical segment contour in the fluid flow through passageway in the valve body for movement to a closed position to block fluid flow through the passageway or to an open position to permit the flow of fluid through said passageway, said valve disc having a concave upstream face surface and a concave downstream face surface to provide flow surfaces offering minimum resistance to fluid flow through passage when the valve disc is open; a valve seal receiving groove in the peripheral edges of the concave edge surfaces of said valve disc, said valve seal receiving grooves being formed to present circular inwardly located capture grooves; a valve seal of a non-elastomer material having exterior inclined wall surfaces terminating to form a relatively flat sealing surface adapted to engage the spherical contoured segment in the fluid flow through passageway, said valve seals also having circular radially outwardly entending bottom flange portions, said valve seals also being provided with a backside circular groove which in cross section presents a truncated triangle configuration having side walls so as to render said seals more readily deformable; a split metallic ring of stainless steel material having continuous continuity disposed within said backside groove of each of said valve seals in contact only with the tapered side walls without fully entering the truncated groove and operable to exert a radial outwardly acting force on the side walls of said valve seals thereby causing the relatively flat contacting surface of said valve seals into intimate sealing engagement with the spherical contour segment surface of said fluid flow through passageway in said valve body; a plurality of force applying screws threadedly engaged in the peripheral edges of said valve disc and in position to engage said split metallic ring to apply a force thereto to expand said metallic ring to thereby adjust the seal pressure of valve seals; and a single removable retainer ring for each valve seal operative to secure its associated valve seal within the associated groove in said valve disc in fluid sealing contact with the wall of the fluid flow through passageway in said valve body when said valve disc is in a closed position.