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.