| 摘要 |
<p>A valve assembly (1), for example, for controlling the flow of bulk material from a duct (2) to a pressure vessel (3), has a cylindrical passageway in which a valve aperture is defined by way of a shear ring (9). A closure member (104) is mounted by way of a support member (24) on a shaft (15) for pivotal movement between the closed position illustrated and an open position in which the passageway (100) is unobstructed. The closure member (104) has a substantially annular surface (105) which co-operates with a complementary surface on the shear ring (9). A deformable sealing ring (27) is housed in an annular recess formed in the outer surface (105) of the closure member. In the closed position of the valve assembly, fluid under pressure is fed to the recess (26) by way of ducts (5, 34) to apply pressure to the inner surface of the ring (27) and thereby deform it into sealing contact with the ring (9). As the deformation of the sealing ring is outwardly the sealing ring is subjected only to natural expansion forces. This enables sealing rings to be employed having characteristics appropriate to the application of the valve assembly.</p> |
