| 摘要 |
A lifting mechanism comprises a mounting structure12and an arm8attached to the mounting structure through a pivot (10). The arm8is arranged for movement about the pivot between a first position and a second position. The mechanism further includes a hydraulic drive means14for rotating the arm8about the pivot and a hydraulic circuit for supplying drive fluid to the hydraulic drive means, said hydraulic circuit including a valve20for controlling the flow of hydraulic fluid through the circuit. The valve20has a first operational condition in which flow is permitted and a second operational condition in which flow is prevented. An actuator24for actuating the valve20is constructed and arranged to move the valve from the first operational condition to the second operational condition when the arm8moves from the first position to the second position.
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