| 摘要 |
A lift system for raising and lowering a load including a rigid platform, four spaced fixed supports positioned around corners of the platform, and a power source connected to a first of the supports. First and second inextensible lines are each preferably fastened at one end to a third support diagonally opposing the first support, and at another end thereof to the power source. The first line preferably extends from the power source to the third support, passing to a plurality of four pulleys each attached to a corner of the platform and over a pulley attached to the second support. The second line preferably extends from the power source to the third support, passing to a plurality of four pulleys each attached to a corner of the platform and over a pulley attached to the fourth support. The lift system produces a mechanical advantage of four. |
