| 摘要 |
<p>A valve assembly for controlling the flow of fluid is disclosed. The valve assembly comprises a ball (1) defining a ball volume and being engageable with a valve seating region (4) to prevent the flow of fluid through a conduit (3) having an internal wall, biasing means (5) for urging the ball (1) into engagement with the valve seating region (4), and a piston (6) defining a piston volume and being located between the biasing means (5) and the ball (1) and arranged, in use, to move within the conduit (3) against the force of the biasing means (5) when the ball (1) is acted on by fluid under pressure entering the valve assembly. The ball (1) is made from a first material and the piston (6) is made from a second material. The density of the second material is greater than the density of the first material. The mass of the ball (1) is defined by the product of the ball volume and the density of the first material, and the mass of the piston (6) is defined by the product of the piston volume and the density of the second material. The combined mass of the ball (1) and the piston (6) is equal to or greater than the product of the ball volume and the density of the second material.</p> |
