| 摘要 |
<p>The present invention relates to system (1) for controlling a hydraulic actuator (2) for the rise and descent of a load, comprising a directional valve (6) for distributing a pressurized working fluid, from which the following branch out: a first working duct (7) associated with a first chamber (4) of the actuator (2) adapted to actuate the descent of the load if supplied and a second working duct (8) associated with a second chamber (5) of the actuator which is adapted to actuate the rise of the load if supplied, and a descent control valve (9) for controlling the descent of the load which is arranged along the second working duct (8), is normally closed in the discharge direction and can be opened in the direction for supplying the second chamber (5) and is driven hydraulically to open in the direction for discharge of the second chamber during descent of the load. The control system comprises a line (10) for driving the descent control valve (9) which is in fluid connection with the second chamber (5) and is flow controlled by a downstream pressure control valve (11), which is normally closed hermetically and is switched to open by actuation means (12), operable by an operator to obtain a preset pressure reduction, and has at least one inlet (13) associated with the second chamber (5) and at least one outlet (14) associated with the descent control valve (9) to drive opening of the valve (9).</p> |
