| 摘要 |
The fishing tool for removing iron-bearing chips from cased deep-drill holes comprises a number of permanent magnets (12) which are arranged on an axially extending, central, tubular mandrel body (5) provided with a top and bottom connecting thread (3, 4) and made of magnetic, high-strength steel. The mandrel body (5) can be inserted as a load-transmitting intermediate connection into a drill stem (6, 7) carrying a working tool at its bottom end, and the permanent magnets (12) are combined in groups in the fishing-tool working sections (11) surrounding the mandrel body (5) in an annular manner. The permanent magnets (12) allocated to a group have an identical axial length corresponding to the length of their working section (11) and are distributed over the periphery of the mandrel body (5) at a uniform mutual distance apart. In this arrangement, the permanent magnets (12) have a radial north-pole/south-pole orientation and within a group alternately present their magnetic north pole (N) or their magnetic south pole (S) on their outside. <IMAGE>
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