| 摘要 |
PURPOSE: A manhole is provided to stably and firmly fix a manhole cover with a support frame and to compact the structure by integrally forming a protruded piece and a combining recess through casting. CONSTITUTION: A manhole comprises a support frame(10) and a cover(20) placed on the support frame. Many fixing pieces(15) are formed on the inner circumference between the upper end of the support frame and a placing sill(14) at a regular interval. The height from the placing sill to the upper end of the support frame is a thickness. The upper portion of the side of the cover is formed in the size the same as the upper inner diameter of the support frame. An insertion portion is formed in the lower portion of the side of the cover. Many protruded portions(22) are formed on the lower end circumference of the insertion portion at the interval of the fixing pieces.
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