| 摘要 |
An overhead crane which includes an improved hoist drum and redundant means for supporting the hoist drum such that the hoist drum will be rotatably operable despite failure of the hoist drum or hoist drum support means. The hoist drum includes an outer cylindrical drum, an inner hollow cylinder positioned within the outer drum, and a pair of bearing shafts rigidly secured to and projecting from opposite ends of the inner hollow cylinder. A first pair of bearing assemblies are provided to rotatably support the bearing shafts and to function as the primary means for rotatably supporting the opposite ends of the hoist drum. A second pair of bearing assemblies, independently supported by the trolley, support the opposite ends of the hoist drum and function to provide independent means for directly rotatably supporting the hoist drum in the event of a failure of one of the bearing shafts or of the first pair of bearing assemblies. When the hoist drum is supported by the first pair of bearing assemblies, the second pair of bearing assemblies are supported by the hoist drum. However, when there is a failure of the first pair of bearing assemblies or bearing shafts and a consequent drop of the hoist drum, the second bearing assembly is received against a support structure in supporting engagement and functions to rotatably support the hoist drum.
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