| 摘要 |
<P>PROBLEM TO BE SOLVED: To provide a manhole cover having a required strength, lower in weight and cost than conventional manholes, and usable for arterial roads. <P>SOLUTION: Parallel cross-shaped reinforcement ribs 7 are formed on the lower surface of the plate part 6 of a cast manhole cover body 5. A surrounding part 8 is formed at the center of the reinforcement ribs 7. Auxiliary ribs 9, 9 the lower edges of which have a height h lower by approximately half the height H of the surrounding part 8 extend radially from the center of a plate part 6 in an X-shape on the inside of the surrounding part 8. <P>COPYRIGHT: (C)2010,JPO&INPIT |
