| 摘要 |
A special tool for use in fishing operations during well drilling when a so-called string shot is used. The tool is made up of a hollow sub that may be connected into a string of pipe for lowering in the well. And, it includes a sliding sleeve in the sub. There is a gate in the wall of the hollow sub that is held in place by the sliding sleeve so as to leave the hollow sub open when a preliminary fishing opertion is attempted. And, there is means associated with the sleeve for sliding it to a different position so that the gate will be shifted in order to guide a string shot to the outside in case the inside of the fish is plugged.
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