| 摘要 |
<p>When drilling curved drill holes, there is used a drill bit whose axis of rotation forms an angle with the centre axis of a guide tube (1) carrying the drill bit. The orientation of the plane passing through the axis of rotation of the drill bit and the centre axis of the guide tube is determined by means of an arrangement in which a magnet (9) is mounted inside the guide tube (1) and arranged to co-act with a first sensing means (26, 27) which is driven by a motor (20) aroung a housing (11) inserted in the guide tube, and which produces a first position signal each it passes the magnet. Located in the housing (11) is a chamber (29) having arranged therein an electrically conductive liquid (30) and a second sensing means (28). The second sensing means (28) is driven round by the motor (20), and each time the sensing means is brought into contact with the liquid in the chamber it gives rise to a second position signal. The time difference between the first and second signals determines the inclination of the aforementioned plane relative to the vertical.</p> |
