| 摘要 |
A lifting jack for lifting loads and exerting a pulling force between two locations includes an I-beam standard having a series of uniformly shaped and evenly spaced apertures, an upper runner disposed about the standard and carrying a first climbing pin which is adapted to fit within a corresponding one of the various apertures, a lower runner disposed about the standard and carrying a second climbing pin also adapted to fit within a corresponding one of the various apertures. The upper and lower runners are connected together by a pitman and these three components are further assembled to a lever which is pivotally attached so as to provide a jacking action to the upper and lower runners. The lever has a pair of fulcrum points only one of which is used with any one jacking cycle, depending upon which runner is advancing and which climbing pin is to be inserted into a corresponding aperture. The pitman is arranged into a single-piece, U-shaped lateral cross-section configuration providing greater strength and durability at a very critical point in the construction. A reversing switch and reversing latch combination are arranged relative to the upper and lower runners so that the direction of movement of these runners may be reversed.
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