| 摘要 |
PROBLEM TO BE SOLVED: To provide an eccentric type butterfly valve capable of holding fast a seat ring having an elliptical inside surface certainly, easily manufacturable, and capable of reducing the costs. SOLUTION: The eccentric type butterfly valve of three-fold type is equipped with a valve body penetrating a fluid passage approximately in the cylindrical shape, a disc-shaped valve element borne rotatably by a valve stem in the valve body, and a seat ring fixed to the inside surface of the body and put in tight attachment to the peripheral surface of the valve element, and is arranged so that the center of the valve element is separated from the center of the stem to generate primary eccentric condition, separated also from the center of the body to generate secondary eccentric condition, and that the center of the conical shape constituting the seal surfaces of the body and element is inclined from the center of the body so that a tertiary eccentricity is established, wherein the inside and outside surfaces of a seat holder to fix the seat ring to the body are formed circular, with a spacer made from a thin rigid sheet interposed between the seat holder and seat ring, and the inside surface of the spacer is shaped in a similar ellipse having a diameter some greater than the ellipse as the inside surface of the seat ring, and threads are formed on the peripheral surface of the seat holder so that it is engaged fast with the inside surface of the body.
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