| 摘要 |
1333860 Taking up slack in flexible elements VETCO OFFSHORE INDUSTRIES Inc 11 Aug 1971 [4 Sept 1970] 37618/71 Heading B8B [Also in Divisions E1 and F1] Means for maintaining constant stress in a pipe or cable comprising: cylinder means having piston means, one of the means being connectible to the pipe or cable; and means for maintaining liquid under pressure on one side of the piston means, the means for maintaining the liquid under pressure comprising gas exerting pressure on the liquid. Fig. 3 shows the invention applied to sub-aqueous drilling to maintain constant stress in a drill string (not shown) supported by a floating vessel. The pistons 14 are connected to a member 10 carrying the hook (not shown), the cylinders 13 are connected to a member 11 supported by the travelling block E, and accumulators 17 supply the liquid to the undersides of the pistons. The parts 21, 22 of the accumulators are filled with the liquid and the gas (nitrogen), respectively, pistons 24 being interposed between the liquid and gas. Gas from storage cylinders 29 is supplied through a pressure regulator 34 to the parts 22. Liquid from a tank 38a is supplied to the parts 21 by a pump 40, the supply being controlled by a differential pressure switch 48 actuating a valve 49 and subjected to the pressures of the gas and liquid. Should the liquid pressure drop below that of the gas in the parts 22 due to the pistons 24 contacting the bottoms of the accumulators, the switch 48 closes and liquid is pumped to the parts 21. If the liquid pressure is greater than that of the gas in the accumulators, the excess pressure is reduced by a differential valve 80. Should the liquid pressure become excessive due to the pistons 24 contacting the tops of the accumulators, the valve 80 opens to reduce the liquid pressure. The cylinders 13 above the piston 14 are filled with nitrogen from a cylinder 62, a pressure gauge 68 giving an indication of the position of the piston 14. Fig. 4 shows the invention applied to crane used for loading a barge, a load supported by the hook 103 having a reduced impact action on the barge when floating in heavy seas. A line 105 running between the travelling block 104 and the drawworks 112 passes round a pulley 108 on the rod 109 of the piston 110 working in the cylinder 111 which is fixed to the frame of the crane, and liquid in the cylinder below the piston is maintained at a substantially constant pressure by means of a system similar to that of Fig. 3.
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