| 摘要 |
As part of a well derrick system using pairs of elongated hydraulic cylinders mounted on the derrick face for well pipe elevating, in which an equalizer beam bridges the cylinder ram heads to maintain equality of advance of the rams, the beam being pivoted on a horizontal pivot above the ram heads, the beam carries a lower centrally aligned horizontal pivot sheave from which a cable extends downwardly to suspend a travelling beam from which depend any of various pipe manipulating tools. In some species additional sheave means on the travelling beam and on an intermediate fixed beam provide for multiple wrappings of the cable whereby force or distance multiplication may be obtained.
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