| 摘要 |
A valve member (40) includes a wedge shaped obturator (42) having sealing regions (46, 48). Below dashed lines A1-A1/A2-A2, the obturator comprises a part-circular-cylindrical outer surface with the axis of the cylinder extending perpendicularly to a stem (12) and inclined planes (43, 44) being tangential to the outer surface. A butt seal region (50) of the obturator includes a central region (52) which extends parallel to the axis of the cylindrical surface. Adjoining regions (54, 56, 58, 60) extend from the region (52) across the cylindrical surface, obliquely to the axis thereof, so as to meet the sealing regions (46, 48). Thus, faces of the wedge above lines A1-A1/A2-A2, blend into the cylindrical surface below the line so that there is a smooth transition between sealing regions (46, 48) and the butt seal region (50). In another embodiment described, an obturator includes two part-circular-conical surfaces spaced apart by an arcuate surface instead of the part-circular-cylindrical outer surface of valve member (40). |
