Butterfly valve sealing means having an improved O-ring groove

In a butterfly valve having a body with an internal circumferential sealing surface and a disc rotatably supported in the valve body, the disc having a circumferential sealing surface therearound, the disc being rotatable so that when the valve is in the closed condition the disc sealing surface is adjacent to or in physical contact with the body sealing surface, the improvement comprising a groove formed in the valve disc sealing surface, the groove in cross section having an outer portion communicating with the disc sealing surface and an inner portion, the groove outer portion having paralleled sidewalls in said cross section, the inner portion being also defined in part by paralleled sidewalls in said cross section, the width of the inner portion between its sidewalls being at least 140% of the width of the outer portion between its sidewalls, the cross-sectional area of the inner portion in said cross section being at least 140% of the cross-sectional area of the groove outer portion in said cross section, the juncture of the inner and outer portions in said cross section providing opposed ledge surfaces in a common plane;

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• an O-ring gasket received in said groove, the cross-sectional area of the total of the groove inner and outer portions being about 105% of the cross-sectional area of the O-ring gasket, the O-ring gasket when in position in the groove normally extending slightly beyond the disc sealing surface to compressibly engage the valve body sealing surface when the valve is in the closed condition.