| 摘要 |
A device for extracting/introducing borehole tubes 8, used in ground drilling and the like, from/into the ground comprises rotating rollers 5 for engagement with tubes for the purpose of moving the latter. The rollers have a plane of mirror symmetry extending at right angles to their axis of rotation. The jacket surface of each of the rollers is provided with a number of peripheral bulges which are designed such that two adjoining bulges situated on the same side of the said plane of symmetry have their tops touching a borehole tube of a certain diameter. This borehole tube diameter increases with the distance of the said bulges from the plane of symmetry, so that the two outermost bulges of the roller are intended to touch a borehole tube of greater diameter than bulges situated nearer the plane of symmetry. <IMAGE> |
