Abstract: A drilling device comprises a drive motor (22), which sets a tool (36) in rotation, and a feed motor (14) which axially displaces the tool. Load sensors (12, 18, 20, 24) detect not only the tool feedrate (V) but also at least two of the three parameters, tool feed force (F), tool torque (M) and tool speed (U). An evaluation and control unit (70) evaluates the above-mentioned parameters and via control units (38, 42) activates the drive motor (22) and the feed motor (14) in such a way that the tool feed force (F) and the tool speed (U) or the tool torque (M) assume values at which the tool feedrate (V) for a specific ground hardness (H) is maximized.

Abstract: A boring tool with two driving heads which are used to sink a casing string and a borer string includes a controllable coupling mechanism fitted between the two driving heads. A mechanism is also provided for the lower driving head, such that the driving head is subjected to an additional downwards acting force. When both driving heads are coupled, the upper driving head is also subjected to an additional, downwards acting vertical force. In order to free the top end of the casing string, the coupling mechanism can be released so that the upper driving head can be fully raised, whilst the lower driving head remains in position adjacent to the ground.

Abstract: A drilling tool (10) of the displacing type comprises a displacing head (22) including a cylindrical mid head portion (24) and lower and upper frustoconical head portions (26, 28). A lower drill portion (12) carries a helical rib (16) which also extends over the lower head portion (26), all portions of this rib being of equal height. The upper head portion (28) is formed with spiroconical displacing walls (32).