| 摘要 |
A telescopic boom for a crane, access platform or the like comprises at least three telescopic boom sections the intermediate section being arranged to be extended by a hydraulic ram while the outer section being arranged to be extended by a pulley and chain arrangement. A telescoping boom safety system includes a wire rope and a pair of linked drag chains which extend from a first anchorage on the outer section around a guide to a second anchorage on the base section. Failure of the pulley and chain arrangement causes the safety system to prevent or contain relative movement of the outer and intermediate sections and thereby stop sudden and catastrophic retraction of the outer section.
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