| 摘要 |
PROBLEM TO BE SOLVED: To perform 'a derricking separate operation control', 'winch separate operation control', 'under-hook length constant expansion and contraction control', 'hook height constant expansion and contraction control' and 'hook length constant derricking operation control' by constituting a control mode to change over from a first mode to a second mode or vice versa. SOLUTION: A controller is provided with a mode changing over means 20, which can change over the current mode from the first control mode to the second control mode or vice versa. In the first mode, 'derricking separation control', 'under-hook length constant expansion and contraction control', and 'winch separate operation control' are made, and in the second mode, 'hook length constant derricking control', 'hook height constant expansion and contraction control', and 'winch separate operation control are made'.
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