| 摘要 |
A jacking assembly for moving a load, in steps, axially of a pipe comprises two pawl boxes having lateral platens and which are mounted at axially spaced positions on the pipe. The pawls of the boxes slope towards the pipe and exert a grip on it which allows relative movement between the boxes and the pipe to occur in one direction only. Inflatable hoses connected to a low pressure water supply are sandwiched between the platens and exert a thrust, when dilated, which increases non-linearly with water pressure, to move whichever of the pawl boxes is carrying the load. This movement, which provides the working stroke, is followed by a recovery stroke during which the pawl box not carrying the load is moved up to the other pawl box under the action of springs or a second inflatable hose. The assembly is able to lift a heavy load with a low pressure water supply and has no moving seals. Its operation in parallel with other such assemblies is also described for house building and slip forming purposes.
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