ROTATION ACTIVATED DOWNHOLE ORIENTATION SYSTEM AND METHOD

摘要

A rotation activated orientation system 10 for a ground drill is operated by action of magnetic fields. The system 10 incorporates a magnetically operated orientator 12 having a free state where the orientator 12 provides a substantially instantaneous indication of a position of a reference bearing of a hole being drilled by the ground drill, and a locked state where the orientator maintains the indication. The system 12 also includes a magnetic actuator 14 operatively associated with the magnetically operated orientator 12. When the rotational speed of the ground drill is greater than a threshold speed the magnetic actuator 14 supplies a magnetic field effective to place the orientator 12 in the free state. When the rotational speed of the drill is less than the threshold speed the magnetic actuator 14 does not supply a magnetic field effective to operate the orientator so that the orientator 12 reverts to or remains in the locked state.