| 摘要 |
PROBLEM TO BE SOLVED: To provide a light-weighted cast manhole cover which can be replaced by utilizing an existing frame without replacing the existing frame. SOLUTION: On the rear surface of a manhole cover 1, ribs are arranged concentrically with a circumferential edge 11 of the cover at a constant pitch, and bolt space 18 and a bolt hole 19 are formed at an intersecting point of the six ribs 14 which radially divides the rear surface into six portions. A through hole for a pin 3 is perforated in each rib 14 at a location spaced a predetermined distance away from the bolt hole, and a lever 2 is fixed to the through hole by the pin 3. Further, the bolt 4 is inserted from the bolt hole 19 through a spherical washer 5 into a hole 25 of a boss 22, and then screwed into a square nut 6, and a spring 7 is installed onto a location between washers 9, 9 to fasten a nut 8, followed by driving a detent pin P. Then, the spring 7 is always biased so as to be in a compressed state to support the lever 2, and the bolt 4 is fastened in a fastening direction to move the lever 2 upward, whereby a front tip engaging portion 20 is press-fitted into the internal wall of a hole H1 of a frame 10 to be linked thereto.
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