| 摘要 |
<p>Two or more flow control valves (140a, 140b) may be used to provide redundant flow control for a hydraulic actuator (111) or servoactuator. The flow control valves include a sleeve (142a, 142b) control spool (146a, 146b). Under normal operating conditions, each bypass control spool is stationary relative to the sleeve and the flow control valve functions as a four-way hydraulic flow control valve. Each flow control valve is connected to a bypass-shutoff valve (160a, 160b) including a bypass spool that is moveable from a shut-off position to a bypass position. Upon supply pressure failure to one flow control valve, the bypass spool moves to the bypass position, reducing pressure in the corresponding actuator piston chambers. When a primary control spool (146a, 146b) becomes jammed, the corresponding bypass control spool moves within its sleeve (142a, 142b) allowing a bypass groove to port control pressure to the return line, thereby reducing pressure in the corresponding actuator piston chambers.</p> |
