| 摘要 |
1. Screw gear for expanding of a telescopic crane jib consisting of a fixed element and a number of elements expandable by means of a screw gear with screws placed inside of each other and equipped with screw caps fastened to cross-bars, and the cross-bars in turn are fixed to the expandable elements, characterised by the fact that the it has an immovable screw (5) mounted on the lower part of the fixed element (1) that is protected from turning and has a powering mechanism (10) connected to the expandable element (2).<IMAGE>
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