| 摘要 |
An extensible interlocking structure suitable for tower cranes, scaffolding towers and the like is of multilateral cross-section and has two sets of main members which engage one another in end-to-end relation when the structure is extended. Tie members are pivoted to the main members, with the free ends of the tie members interlocking automatically with the main members during extension to provide diagonal bracing. On retraction the members may be stored on drums or in a rack.
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