| 摘要 |
A four-stage upright having a fixed upright section, three telescopic upright sections, and a load carrier mounted on the inner telescopic section includes a first asymmetric lift cylinder assembly located in the upright off-center and adjacent to one side of the upright and a second asymmetric lift cylinder assembly mounted in the upright off-center and adjacent to the opposite side of the upright. The first cylinder assembly is supported from one of the telescopic upright sections and is operatively connected to the load carrier, while the second lift cylinder assembly is supported from the fixed upright section and is operatively connected to the three telescopic upright sections. The first cylinder assembly is, when collapsed, approximately one-half the height of the collapsed upright, and the second cylinder assembly is, when collapsed, approximately equal to the height of the collapsed upright. A unique balancing system is implemented in the combination of cylinder locations and respective reeving of lifting chains which maintains a substantial balance of force-moments in a transverse plane of the upright.
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