| 摘要 |
<p>The step ladder (1) can be moved along without involving need to climb down and remount. It rests on one side on drive rollers (2) and on the other on running rollers (3), one of the former being linked to a ratchet wheel (4). A push-rod (5) passes through the steps on one side, with treadboards (6) fitted above. In its top setting, the rod is pressed by a cylinder spring (7). Treading on a board causes the rod to move downwards, with its bottom end pressing on a wheel tooth, to turn it slightly, and repeated treading causes the ladder to move along. A braking strip (8), fixed to a board, prevents unintentional movement.</p> |
