| 摘要 |
Detection signals from lever sensor (29), sit-down sensor (30) and vehicle speed sensor (31) are read into a controller (32). A control signal is produced by the controller (32) to switch a directional control valve (20) of a control valve unit (16) instantly from a floating position (c) to a neutral position (a) and to switch another directional control valve (21) from a neutral position (a) to a lowering position (d) when a dump truck (1) is in travel with the directional control valve (20) of the control valve unit (16) is switched in the floating position (c). Whereupon, a hoist cylinder (10) is contracted by a hydraulic pressure force to hold a vessel (3) in a sit-down position on a vehicle body (2), thereby preventing the vessel (3) from shaking movements like floating up while the dump truck (1) is in travel.
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