| 摘要 |
An earthmoving vehicle has an operating arm that is raised and lowered by a hydraulic system. The hydraulic system includes a drain line and at least one actuator connected to the operating arm. The actuator defines a variable-volume chamber connectable to the drain line to lower the operating arm. The hydraulic fluid discharged from the chamber flows through a proportional safety valve adjacent to the actuator and a distributor valve that is driven by a pilot control valve to allow free flow to the drain line. Thus, the lowering of the operating arm is controlled solely by the proportional safety valve.
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