| 摘要 |
916,257. Ramps; substructures for oil well derricks. MOORE CORPORATION, LEE C. Dec. 20, 1960 [May 10, 1960], No. 43727/60. Classes 78 (3) and 78 (4). A ramp structure for raising a vehicle 14 adjacent an oil well drilling mast 1 comprises a pair of tracks 15, connected by cross-members 16, 17 and supported by braced links 21, which are pivoted at 25 to the base 4, and rollers 37 running on fixed tracks 36. The inclination of the tracks 36 is such that, on raising the tracks 15 by a cable 28 and winch 34 from the position shown, the tracks 15 are substantially horizontal in their fully raised position, Fig. 2 (not shown). In the raised position, the links 21 are slightly over-centre and lugs 41 on the tracks 15 may be connected to lugs 42 on the mast 1 by pins.
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