| 摘要 |
PROBLEM TO BE SOLVED: To provide a speed control apparatus for a hydraulic winch using a variable displacement motor having no fear of causing hunting of control although a high speed mode and a low speed mode are switched and selected manually when designated conditions are satisfied regardless of the stroke position of a winch operating lever. SOLUTION: In the hydraulic winch of a crane using a variable capacity motor in which the capacity required for one rotation is switched to switch the rotating speed to the supply flow to a high speed mode and a low speed mode, hoist load computed immediately before the start of lowering the winch operating lever by an overload preventing device is stored as an actual operation hoist load until the end of lowering operation. When the actual operation hoist load is smaller than a designated value, the lowering operation is performed and switching to the high speed mode is manually selected, the variable capacity motor is switched from the low speed mode to the high speed mode.
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