| 摘要 |
A pipe joint for self aligning a drill string, tubing string or casing string of the type comprising a plurality of drill pipe, tubing or casing sections arranged in end to end relation from a location above the ground to a lower location adjacent a tool connected to a bottom end of the string and wherein the adjacent ends of the sections are connected to each other to form a plurality of spaced joints extending downwardly from the ground to the tool, the improvement wherein each joint comprises an upper section having at least one downwardly projecting extension and a lower section having a corresponding recess for receiving the extension and wherein the extension and the recess can fit together in only one way.
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