摘要 |
<p>A control valve device (16) comprises two direction control valves (20, 21). The direction control valve (20) has an extension-side variable throttle unit (20c) and a contraction-side throttle unit (20d). The direction control valve (21) has an extension-side variable throttle unit (21c) and a contraction-side throttle unit (21d). A controller (35) determines that a hoist cylinder (10) is approaching a stop position, when the hoist cylinder (10) extends to raise or lower a vessel (3) and the hoist cylinder (10) is approaching the stop position. Based on this determination, the controller (35) uses the variable throttle units (20C, 20D) to variably adjust the flowpath surface area of the direction control valve (20) or uses the variable throttle units (21C, 21D) to variably adjust the flowpath surface area of the direction control valve (21), so that the expansion/contraction speed of the hoist cylinder (10) is increased or decreased according to the weight on the vessel (3) side.</p> |