| 摘要 |
A settable control valve (13, 50, 113) has a closure member moveable within a passage-way (17, 71, 81A, 101, 117), there being at least one groove for fluid flow (25, 26, 44, 56, 57, 97, 98, 107, 108, 125, 126) in the wall of the passageway. The groove is of varying transverse cross-sectional area along its length and the closure member may be set at different positions so as to expose varying lengths of the groove to fluid flow, hence enabling different fluid flow rates to be established. |
