Public highway manhole cover for vertical shaft has a sub-surface with a curved ridge resting on a sub-frame to prevent rocking

摘要

A public highway has sub-surface installations to which access is provided by a vertical shaft with a manhole cover. The manhole cover rests on a sub-frame. The manhole cover sub-surface has a curved ridge that prevents rocking when the cover is subjected to the weight of a passing heavy vehicle. Also claimed is a commensurate castor-mounted lifting frame for removal of the cover for access.