| 摘要 |
<p>A jack for raising a vehicle to provide access for undersealing is actuated by two electrically driven ball screws. The jack has two parallel cantilevers (4) which run on rollers on vertical guides (1). The guides (1) are held vertical by bracing members (2, 3). Ball nuts attached to the cantilevers (4) are engaged by vertical screws driven by an electric motor mounted on the upper cross beam (7). The two screws are synchronised by a device which compares the voltage from generators driven by each screw. A brake is then applied to reduce the speed of the faster running screw to maintain the cantilevers (4) at the same level.</p> |
