| 摘要 |
<p>An electrohydraulic doser actuator of the kind comprising a step piston the axial position of which is variable as a function of metered doses of pressurized fluid which are vented to or from a control chamber by a first on-off valve connecting the latter to a high pressure source or a second on-off valve connecting it to a low pressure source, said valves being normally closed and thus establishing a hydraulic lock on the piston to maintain same in its last reached axial position. In order to improve the precision of positioning of the piston (58, 60), the invention provides for a pair of additional on-off valves (52, 53) mounted in parallel relationship to the main on-off valves (51, 54), respectively, and having a smaller opening than said main valves for the control of small adjustments of the position of the piston. For use particularly in gas turbine control systems.</p> |
