| 摘要 |
A jacking device includes a base member, an upper member, and, at least one intermediate member. Each member includes screw threads adapted to engage a respective screw thread of an adjacent member. Drive means is included to permit movement of the members, and to thereby raise or lower an upper surface of the jacking device. The intermediate member may rotate as the drive means operates, but the upper and lower surfaces are preferably prevented from undergoing rotational movement. A plurality of such jacking devices may be operated simultaneously to raise or lower a load or other object. |
