| 摘要 |
A telescopic bar of drill rig for drilling in general, where the telescopic sections (10, 11, 12) consist of concentric, substantially cylindrical pipes, each of them equipped with longitudinal internal (16,17) and external (13,14) toothed ribs arranged in such a way that the external rib of each pipe and the internal one of the external pipe are engaged when the bar is being rotated to lock the telescopic sections in position, and released when the bar is being rotated in the opposite direction to lift and withdraw the bar sections.
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