| 摘要 |
<p>A hydraulic control system comprising a hydraulic actuator (20) and a variable displacement pump (22). A pilot pressure operated meter-in valve (27) controls the direction and velocity of the actuator through a pair of actuator lines (A, B). A pilot pressure operated meter-out valve (34d, 35d) is associated with each actuator line (A, b) for controlling the flow out of the actuator when that actuator line returns the flow to tank. A spring loaded poppet valve (41, 42) is associated with each actuator line (A, B) and a passage (90) extends from at least one of the poppet valves (41) to the meter-out valve (34d) and is operable, when the meter-out valve (34d) is closed after being open, to reduce the pressure holding the meter-out valve (34d) closed, thereby permitting the spring loaded poppet valve (41) to open at a relatively low pressure developed in one (A) of the lines associated with the one meter-out valve (34d), thereby allowing the one meter-out valve (34d) to open.</p> |
