This invention relates to valves and more particularly to valves of the type known as disc or BUTTERFLY VALVES. Heretofore in the art to which my invention relates, difficulties have been encountered in providing a proper seal between the disc edge and the annular seat surface, particularly in the region where the stem portions extend from the disc into journal openings through the annular seat. It has been a common practice to employ a permanent compression of the disc edge against the annular valve seat in the region where the stem portions extend from the disc in both the open position and closed position. The transition from this permanent compression fit to the compression which occurs only on the closure of the valve has been very difficult to achieve heretofore due to the fact that the valve disc has thickened hub portions at the junctures of the disc and stem portions for the purpose of providing a convex annular sealing surface. This annular, convex surface is necessary to provide a continuous sealing member from the narrow disc edge on one side of the stem to the narrow disc edge on the other side of the stem. Accordingly, it has been very difficult to provide fluid-tight seal between the disc and the annular flow passage, particularly in the area where the stem or shaft projects from the valve disc, thus exposing the stem or shaft to the fluids flowing through the flow passage.

To overcome the above and other difficulties, I provide a Butterfly Valves having a disc with a lip seal around the entire periphery thereof and struck on a spherical radius substantially equal the radius of the annular seat in the flow passageway which is engaged by the lip seal. To provide an effective seal between the stem portions or shaft portions of the disc and the valve seat which surrounds the shaft, I provide an outwardly facing convex seal surface surrounding the shaft and provide an inwardly facing concave seal surface in the annular seat with both seal surfaces being in the shape of a segment of a sphere struck on substantially the same radius as the radius of the annular seat whereby the adjacent seal surfaces surrounding the shaft engage each other with sufficient pressure to provide a fluid-tight seal therebetween regardless of the position of the valve disc relative to the flow passage. Butterfly Valves To provide a further seal between the valve seat and the adjacent surface of the shaft and the adjacent sealing surface of the disc, I provide an O-ring groove in the valve seat adjacent the shaft with the entire bottom of the O-ring groove being an equal distance from the axial center of the flow passageway through the valve whereby the O-ring groove is of the same depth all the way around the shaft.

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