| 摘要 |
Modules of eg. 3 steps, bolted to the cage walls, themselves of modular construction, are only lightly fixed (10) to the central column (11), a hollow tube supporting an inner worm shaft (5) on top and bottom bearings (22, 20) and bottom thrust bearing (26). Three nuts on the shaft are attached, by horizontal fixings passing through a helical guide slot (17) to an external part-cylindrical plate (15), supporting (14) a fold-up seat (28), foot-rest (29) and safety bar (30). Rotating the worm gear by belt-drive (27) from a motor (13) causes the nuts, and hence the attached support and seat, to rise and fall, on a helical path, dictated by the guide-slot, parallelling the stair's.
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