| 摘要 |
PROBLEM TO BE SOLVED: To eliminate requirement of a clutch and a brake for free fall, and secure a good operation feeling with a free fall characteristic approximated to a mechanical brake which applies speed adjustment (deceleration, stopping) operation with dropping a hoisted load by the hoisted load weight. SOLUTION: While lowering rotation of a winch drum 1, a control valve 5 is operated to the lowering side by a free fall valve 11 in a state that capacity of a hydraulic motor 2 is set to be a small capacity, and thereby, the hydraulic motor 2 is rotated to the lowering side at a high speed. At this time, simultaneously by controlling a motor holding pressure by a holding pressure control valve 18 according to operation amount of the free fall valve 11, the hydraulic motor 2 is adjusted in rotation speed and is stopped.
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