The present invention relates to a BUTTERFLY VALVES in which a disk-like valve member rotates about a valve stem acting as a shaft.

The prior art to which the invention is directed includes the art of Butterfly Valvesbeing of a type in which a usually circular vane or disc is rotatable in the valve passage between an open and a closed position. When in the closed position, a valve member engages with a valve seat to cooperate to provide a seal against leakage of the fluid in the pressurized line intended to be controlled by the valve. It is essential in valves of this type that the seal is effective on each occasion of valve closing throughout the life of the valve to continuously provide positive shut off without frequent maintenance and servicing of the seat. Since the seat is commonly subjected to wearing conditions by factors such as corrosion and temperature changes and the like, it is desirable to provide an ideal seat which is completely unaffected by these factors.

A valve stem is provided so as to pass through the valve seat and thus wearing is caused between the stem and the seat. Accordingly, it is desirable to provide a sealing assembly capable of sealing the fluid against leakage from between the valve stem and the valve seat.

Further, it is desirable to provide a valve seat which is adapted to be fitted onto the inner circumferential surface of a valve body, and to contact with tubular flange members with the valve being held between the tubular flange members, whereby the valve body and the tubular flange members in close contact with each other can provide a seal of the fluid against leakage.

An important object of the present invention is to provide a Butterfly Valves in which the central portion of a valve seat is formed in a raised shape, whereby a valve member in a closed position is resiliently urged at its peripheral edge by the raised portion of the seat.

Another important object of the present invention is to provide a butterfly valve in which an annular groove is provided in the inner circumferential surface of a hole provided in a valve seat through which the valve stem extends, and a sealing assembly comprising an annular holder and an O-ring adapted to be inserted inside the holder is placed in the groove.

A further important object of the present invention is to provide a butterfly valve in which a dovetail is provided in the inner circumferential surface of a valve body; a dovetail groove to correspond to the dovetail is formed in the outer circumferential surface of a valve seat, and each of two opposing faces of two annular projections so as to define the dovetail groove in the valve seat has a round shape while the outer circumferential surface of each projection is tapered with a larger diameter on the side of the opposing face.

A further object of the present invention is to provide a butterfly valve in which the end portion of the cylindrical portion of a valve member through which a valve stem extends define a plane extending to the periphery of the valve member, while a valve seat is formed in a shape as fits with the valve member.

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