| 摘要 |
<p>PURPOSE:To generate an effective magnetic field and to prevent breakage of a magnetic field induction cable by coating the magnetic field induction cable with a cover formed of a non-magnetic body. CONSTITUTION:A rectangular facing is formed at a predetermined position at the front face of a shielding machine 1a, with a magnetic field induction cable at the bottom thereof. A rectangular loop is thus formed. The cable 2 is coated with a cover 5a of a non-magnetic body. It may also be possible that the cable is coated with a square rod 5b having a groove 5b1. Accordingly, the cable 2 is prevented from being disconnected by the abrasion due to the rock and sand, and an effective magnetic field is obtained for a position detecting sensor.</p> |
