| 摘要 |
PROBLEM TO BE SOLVED: To provide a locking device for a manhole lid, which enables a person to distinctly discriminate between a locked state and an unlocked state by determining whether or not a lock unit can be inserted. SOLUTION: This locking device makes a locking shaft 16 rotatively operated by using a lock operating implement 13, after the extraction of the lock unit 12. A driving part 14 of the lock operating implement 13 is formed on the bottom wall of a bit cylinder 21 which is attached and held to a main body part of the implement 13 by an attractive force of a magnet 20. A blocking protrusion 23, which gets into a diameter-enlarged retainer groove 10 of a fixed outer cylinder 4 via a longitudinal groove 22 in the inner peripheral surface of the outer cylinder 4, is provided on the outside surface of the bit cylinder 21. When the implement 13 is extracted from the outer cylinder 4 after a fastening metal body 19 is turned to an unlocking position, the blocking protrusion 23 abuts on a stepped wall surface 24 of the groove 10, so that the bit cylinder 21 can be separated from the main body part of the implement 13, and the bit cylinder 21 is left inside the outer cylinder 4. COPYRIGHT: (C)2007,JPO&INPIT
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