摘要 |
<p>A safety valve assembly includes a pair of parallel-connected directional control valves controlled by solenoid-operated preliminary control valves; each directional control valve has a working piston and a valve member movable in a separate bore; the bores are interconnected by crossing passages and each passage is branched into a preliminary control channel communicating via a valve seat of the preliminary control valve with the working piston to admit sufficient amount of pressure medium against the working piston to switch the same over when the preliminary control valves are simultaneously operated.</p> |