| 摘要 |
A work platform (10) is guided for up and down movement along support columns (12). Advance/retract cylinders (50, 52) are interconnected between a portion (26) of the platform (10) and a first support (28). Advance/retract cylinders (64, 66) are interconnected between the platform (10) and a second support (30). Each support is in the nature of a clamping mechanism. Each includes a pair of clamp members (32, 34) and (54, 56) which are pivotally connected together. Hydraulic cylinders (46, 48) and (60, 62) move the members (32, 34) and (54, 56) together and apart. When these members (32, 34) and (54, 46) are moved apart, they move grip pads (44, 58) into gripping contact with the support column (12). When they are moved together, they move the gripping pads (44, 58) out of contact with the support column (12). In use, one support (28, 30) is clamped to the support column (12) while the other is unclamped. The advance/retract cylinders (50, 52) or (64, 66) associated with the clamped support (28) or (30) are either advanced or retracted, for the purpose of moving the platform (10) relatively along the support column (12). At the same time, the other set of advance/retract cylinders (50, 52) or (64, 66) are either fully retracted or fully advanced, to a start position.
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