| 摘要 |
PROBLEM TO BE SOLVED: To provide a fixed structure of an underground structure which does not get loose even if a bolt fixing the lid to a frame oscillates due to comings and goings of vehicles and people and in which rainwater or the like does not intrude. SOLUTION: A protrusion 2a having a bolt hole 3 is formed in a shelf 2 of a frame 1 and bolt hole 5 is formed to face a hole 3 of the projection 2a of the frame 1 in the lid 4 also. The upper part of the hole 5 is shaped to have a widened hole 6. A protruded recess is formed in the widened hole 6. A right polygonal bolt 7 in the head is inserted in holes 3, 5. The inside face of the ring is so serrated that the same radius with a radius extending from the center of the head 8 of the bolt 7 to the corner and a shorter radius than that are alternnately arranged. A stopper 9 in which a protrusion 11 which can insert in a protruded recess of the widened hole 6 is provided is fitted to the head 8 of the bolt 7 and the protrusion 11 is inserted in the protruded recess 12 and further, a rubber cap 10 is fitted to the upper part of the head 8 of the stopper 9 and the bolt 7. COPYRIGHT: (C)2004,JPO
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