| 摘要 |
A manhole structure comprising a circular frame formed with a pair of diametrically opposite inwardly and upwardly open recesses traversed by respective pivot pins and a further pair of diametrically opposite brackets having inwardly and upwardly open recesses. A pair of semicircular cover heads, each has three radially projecting lugs including a pivot lug engaging a respective one of the pins and a pair of support lugs at opposite ends of the rectilinear edge of the cover half. The pivot lug has a pocket receiving the pin and communicating with a narrow slot whereby the pivot lug is inserted over the pin, the pocket being shaped so that when the cover is swung open, it can be braced between the pin and an edge of the recess. All of the recesses have wedge-forming inclined flanks which engage inclined flanks of the cover halves to support the latter in their closed positions. |
