| 摘要 |
A boom hoisting device comprising a mast (8) having a pivotable front end portion connected to a front end portion of a boom (4) through a guy line (11), a mast-side spreader (9) provided at the front end portion of the mast a frame-side spreader (10) removably mounted to an upper rotating body (2) and with a hoisting rope being stretched between and spread on both mast-side spreader (9) and frame-side spreader (10), and a hoisting winch (7) adapted to unwind and wind the hoisting rope (12) to raise and lower the mast and the boom, the hoisting winch (7) being mounted to the mast (8) so that the mast (8) and the hoisting winch (7) are together removed from the upper rotating body (2) by separation of a base end portion of the mast (8a) from the upper rotating body (2).
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