| 摘要 |
PROBLEM TO BE SOLVED: To prevent a lid for an underground structure from being forcibly opened by a malicious third person. SOLUTION: A tool insertion hole 21 is formed at the peripheral edge of a cover body 2, fitted to the upper end opening of a receiving frame 1. A locking body 3 is rotatably supported on the rear surface of the cover body 2 in proximity to the tool insertion hole 21. A hooking part 31 engaged with the inner peripheral portion of the receiving frame 1 is formed on the locking body 3. A closing plate 4 for closing the tool insertion hole 21 via an elastic member 5 is so installed between the cover body 2 and the locking body 3 as to be pushed down. A barrier projection 42 is formed on the closing plate 4, adjacent to a plug part 41 fitted to the tool insertion hole 21 and at the position nearer the center of the cover body 2 than the plug part. When the closing plate 4 is lowered by the pressing of the plug part 41, the barrier projection 42 is positioned at the upper side closer to the center of the cover body 2 than the tool insertion hole 21, and closer to the rear surface of the cover body 2 than the plug part 41 by the rotation of the locking body 3. COPYRIGHT: (C)2009,JPO&INPIT
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