| 摘要 |
A column hoist for elevation of vehicles and the like for maintenance comprises a pair of upright columns (11, 12) supported on a base (14) having a pair of rollers (18) and steerable pneumatically tyres wheels (19). An electric drive motor (43) is mounted atop columns (11, 12) and is coupled to a screw threaded drive shaft (37) extending downwardly between columns (11, 12). A slidable carriage (24) is cantilevered from columns (11, 12) for movement therealong in an upright direction. Shaft (37) is coupled to carriage (24) by a pair of recirculating ball bearing assemblies (48a, 48b), the upper of which normally supports a load on the carriage (24). In the event of failure of upper bearing assembly (48a), load is transferred to the lower bearing assembly (48b) and a sensing switch (60) activates motor (43) to rotate shaft (37) only in a direction which effects lowering of carriage (24). Shaft (37) is suspended from an upper thrust bearing (35) to avoid bowing of the shaft under load.
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