| 摘要 |
In a telescopic arrangement wherein a plurality of telescoped tubes are provided for retraction and protraction; the tubes each include a nut element, said nut element being axially aligned, and means for causing one tube to engage respective outer one, the combination of a first main drive and working spindle onto which the nut elements are threaded to cause protraction and retraction of the respective tube, the nut elements disengaging one by one from the thread of the spindle as the respective next tube is caused to protract and its nut travels on the first spindle; a second nut retention spindle onto which the nuts of those tubes are threaded which are not yet to be extended or which have been retracted; there is a threadfree space between the two spindles to be traversed by that one of the nuts next to be threaded onto the first spindle and prior to that one of the nuts that travels on the first spindle leaving that first spindle; the two spindles are driven in unison but at a particular ratio so that a nut on the first spindle travels essentially for the length of the first spindle while the nut on the second spindle moves only for a short distance.
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