| 摘要 |
A pipe spin-blast tool having a tubular handle with inflow and outflow ends. An inner pipe is rotatably mounted to the tubular handle and a jet head is fixed at the end of the inner pipe for rotation therewith. A sand-air mixture is caused to enter the inner pipe through the inflow end of the tubular handle, whereafter the mixture exits the pipe sand-blast tool through angularly aimed nozzles on the jet head. A stationary annular disc and a rotating annular disc are disposed between the jet head and the tubular handle coaxial to the inner pipe. The stationary disc is fixedly mounted to the outflow end of the tubular handle and includes a first set of permanent magnets having coinciding poles aligned parallel with the inner pipe. The rotating disc is mounted to the inner pipe so that it will rotate relative to the stationary disc and has a second set of permanent magnets having coinciding poles oriented opposite the poles of the first set. Thus, the magnets of the first set magnetically attract the magnets of the second set to define a condition of maximum disc stability when the sets of magnets are aligned. The drag which results from forced movement from this condition retards the rotational velocity of the inner pipe. The drag may be varied by axial displacement of the rotating disc relative to the stationary disc.
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