| 摘要 |
The auto-erection tower crane possesses a tie-free jib, mounted at the summit of a mast and extended, toward the rear of its connection point to the summit of the mast, by a counter-jib, the end of which is connected, by a rear tie, to a bogie truck element of the crane. For the transport of the crane, the counter-jib is folded up in a vertical plane on the rear part of the jib. The unfolding and folding-up of the counter-jib are realized automatically, simultaneously with the automatic erection or dismantling of the crane. The structure of the counter-jib also allows adjustment of the working position, horizontal or inclined, of the jib.
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