Manner null of assembling the sheet ring and the said sheet ring of decentering die butterfly

摘要

PROBLEM TO BE SOLVED: To provide a seat ring to hold a seal function without damage, such as wear, and to provide an increased life and to provide an assembly method therefor, in an eccentric butterfly valve. ;SOLUTION: In an eccentric type butterfly valve having an annular seat ring located between a valve element and a peripheral edge, a seat part 12c in an angle shape in cross section to bring the peripheral edge part of a valve element into pressure contact with an annular seat ring 12a during closing of a valve is continuously formed at an annular seat ring 12a along a circumferential direction. The position in a circumferential direction of a point 21 with which the whole periphery of the peripheral edge of the valve element 14 during closing of a valve makes approximate simultaneous contact is formed from a straight line 21a in the vicinity of a position part parallel to a valve spindle insertion part in a developed state. Other section than the vicinity of a valve spindle insertion parallel part formed from the straight line 21a is formed from a cosine curve 21b. A second chevron seat part 12h is formed from a straight line and a cosine curve such that a portion between the approximate simultaneous contact point 21 of the first angle part 12, where an approximate simultaneous contact 21 with the peripheral edge of a valve element is formed, to the lower part of the first angle seat part 12c is reinforced.;COPYRIGHT: (C)1999,JPO