| 摘要 |
<p>A fluid flow control valve which is responsive to the pressure drop occurring across the valve in order to maintain a substantially constant volume of fluid flow regardless of the pressures appearing at the upstream and downstream sides of the valve has a valve casing (2) with an inner face (2C) that widens outwardly from a fluid inflow end to a fluid outflow end, and a valve member (3) which is convex towards the fluid inflow end of the casing and is axially movable relatively to the casing (2) in order to vary the annular gap between the valve member (3) and the valve casing (2C). Means (25, 26) for sensing the fluid pressures at points spaced from the valve member (3) on the upstream and downstream sides thereof are coupled to a fluid pressure actuating mechanism (32, 33, 4) for acting directly upon the axially movable valve member in order to vary the axial position of the valve member (3) in accordance with the pressure drop across the valve. The valve is biased towards its open position by a biasing means (51, 52) presenting a force proportional to the closing movement of the valve member, and the shape of the inner face (2C) of the valve casing is so profiled that the coefficient of resistance presented by the valve is directly proportional to the linear closing movement of the valve member (3). This enables direct adjustment of the valve member in response to the sensed pressure drop, without the requirement for any intermediate control mechanism to compensate for the characteristics of the valve. </p> |
