| 摘要 |
A jacking device for use with a thread bar having a plurality of couplers and nuts spaced longitudinally thereon. The jacking device is arranged to permit movement thereof longitudinally past the respective couplers and nuts while permitting utilization of the nuts by threaded movement thereof on the thread bar for supporting different portions of the jacking device relative to the thread bar in effecting the desired jacking operation. The jacking device may be utilized to climb the thread bar and, alternatively, may be utilized to pull the thread bar and lift a load associated therewith. The jacking device includes biased chuck elements movably carried to permit passing of the couplers and nuts and selective support thereof on the nuts in effecting the controlled jacking operation. |
