| 摘要 |
A double slewing crane comprises a vertical support or column which is adapted to be fixed in position, for example on a ship between two cargo hatches. A first crane arm or cantilever arm is pivotally mounted on the support for pivotal movement about a vertical axis and a second crane arm or cantilever arm is pivotally mounted on the support for pivotal movement about the same vertical axis. Each crane arm carries a jib which is pivotally mounted at its inner end about a horizontal axis and one of the jibs may be made shorter than the other. The pivotal mounting includes a ring gear which, for example, may be fixed with respect to the support, and each cantilever arm portion carries a drive motor with a drive pinion which engages the ring gear to effect the individual rotative motion of the associated cantilever arm. Drive motors of the two cantilever arms may be synchronized so that the arms rotate together about the fixed ring gear. Each cantilever arm carries a crane tower, turret, or mast with the jib and the towers may be spaced apart from each other by positioning their associated supporting arms at a respective angle from an extension of the common vertical axis. Alternately a first crane and tower, turret, or mast may be mounted for pivotal movement about an axis directly above the supporting member and the second crane may be carried on a cantilever arm at the outer end thereof so that it pivots about the common vertical axis at a location spaced radially from the first vertical axis.
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