Butterfly valve

Claim 1

A butterfly valve comprising a valve body of rigid material defining a circular cross-sectional fluid flow channel therethrough, an annular seat affixed by the radially outwardly portion thereof in said valve body to circumscribe said flow channel, said seat having a flexible radially inwardly portion protruding into said flow channel, a shaft aligned nondiametrically across said flow channel at a point axially displaced along said flow channel from said annular flexible seat, a valve disc mounted for rotation about the axis of said shaft, the circumferential surface of said disc constituting a segment of a continuous geometric surface converging at a point on the axis of said flow channel, said surface constituting a sealing surface adapted to cooperate with said annular seat, the radially inwardly portion of said annular flexible seat having an annular sealing surface adapted to cooperate with said circumferential sealing surface on said disc to block flow through said channel when said disc is rotated into the closed position perpendicular to the axis of said flow channel, another annular surface of said inwardly portion of said annular flexible seat, disposed noncolinearly to said annular sealing surface thereof, exposed to the fluid in said flow channel and adapted to augment the sealing effectiveness of said seat against said disc by the action of fluid pressure, said valve effectively controlling the flow of fluid therethrough at any desired proportion not greater than unity of the fluid pressure prevailing upstream thereof by rotation of said disc about the nondiametric axis to any flowcontrolling position at least about 15* from said closed position, an annular rigid-surfaced ring element axially displaced along said flow channel from said shaft and from said annular seat, but proximate to the latter, the annular opening thereof projecting radially inward to an extent short of intersecting with the locus of rotation of said disc but sufficient to assure that, when said disc is in said flow-controlling position, every point on said circumferential sealing surface on that portion of the disc rotated in, the axial direction toward said ring element is closer to said ring element than to any portion of said flexible seat, and another said ring element being positioned on the opposite side of said seat from the first said ring element, the respective extremities of said shaft being mounted in narrow-walled sleeve bearings inserted into cavities in said valve body, the materials from which said sleeve bearings and said flexible portion of said annular seat are formed having a heat-destruction temperature considerably lower than that of said valve body and said disc, the wall tHickness of said sleeve bearings being substantially the same as the clearance between the locus of rotation of said disc and said ring elements, whereby substantial sealing effectiveness is retained by said valve despite heat damage thereto.