초록 ▼

An improved manhole structure is disclosed which comprises a cover having a rim inclined inwardly at 45°, on which a plurality of protrusions are provided; a ring for elevating the cover, having an upright inner wall and outer wall and an upper face and lower face, both inclined inwardly at 45°, on

An improved manhole structure is disclosed which comprises a cover having a rim inclined inwardly at 45°, on which a plurality of protrusions are provided; a ring for elevating the cover, having an upright inner wall and outer wall and an upper face and lower face, both inclined inwardly at 45°, on the said upper face a plurality of holes are formed for engagement with the protrusions formed on the cover, and on the said lower face a plurality of protrusions are formed; and a base having an upper surface inclined inwardly at 45°, and a flat lower face, on the said upper surface a plurality of holes are formed for engagement with the protrusions formed on the lower face of the said ring.

대표청구항 ▼

An improved manhole structure, which comprises; (a) a circular cover having a rim inclined at 45°inwardly of the periphery of said cover to define a continuous conical contact surface, a plurality of lug protrusions extending from said contact surface; (b) a ring having an axial inner wall and an ax

An improved manhole structure, which comprises; (a) a circular cover having a rim inclined at 45°inwardly of the periphery of said cover to define a continuous conical contact surface, a plurality of lug protrusions extending from said contact surface; (b) a ring having an axial inner wall and an axial outer wall and an upper face and a lower face, both said upper and lower faces being inclined inwardly at 45°to define continuous conical surfaces, on the said upper face there are a plurality of holes so shaped and located to engage with the protrusions on the cover contact surface, and on the said lower face there are a plurality of lug protrusions, and (c) an annular base having an upper surface inclined inwardly at 45°and a flat lower face, on the said upper surface there are a plurality of holes so shaped and located to engage with the protrusions formed on the lower face of the said ring.