| 摘要 |
A magnetic jack comprising a body consisting of a series of slidably telescoped sections expandable along the jack axis, and a pair of electromagnets disposed between each successive pair of sections, each connected to one section, and having confronting poles of like polarity, so that they repel each other when electric current is supplied thereto, in order to extend the sections along the jack axis. The magnet pairs between successive pairs of body sections may be energized selectively, or the energizing current may be variably adjusted, in order to vary the height and force of the lift provided by the jack.
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