| 摘要 |
A butterfly valve comprises a valve member 12 supported for angular movement relative to a valve seat (14, Fig. 1) about a pivot axis 18, the valve member 12 having a peripheral edge defining a sealing surface and a sealing line 12b. The sealing line 12b lies upon the surface of a notional sphere 12a and the pivot axis 18 is parallel to and offset from a plane of the valve member 12 and offset from a diameter of the valve seat 14 in a first direction. The valve seat 14 takes the form of a truncated cone 28 of circular cross-section, the notional apex 26 of the truncated cone 28 being eccentric to the valve seat. A notional line 26a passes through the apex 26 and extends parallel to the axis 24 of the valve seat 14 and is offset from the axis 24 of the valve seat in the first direction. A first part of the truncated cone 28 is tangential to the notional sphere 12a, and a second part of the truncated cone 28 is not tangential to the notional sphere 12a. |
