| 摘要 |
The device has under reamers (12), which are foldable and removable, and arranged to ends of a plough (5). The under reamers are connected to the plough by a pivot type link. The reamers are placed and maintained in the link in two separate positions, where in one first position the reamers are folded with respect to the plough and in another position the reamers extend the plough.
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