| 摘要 |
The two or more connected sets of steps are driven by a motor with gearing wherein the upper step part in the useful state forms the drive member and the lowermost part in the useful state forms the coupling member. An intermediate link member forms the output member. The articulated gearing means that the unfolding and collapsing of the middle and lower step parts are coupled together. A crank fixed directly or indirectly to the upper step in the useful state prevents excessive strain in the gearing and motor. |
