Modular utility vault

Claim 1

A utility vault comprising a pair of like semicircular sections of a molded plastic material having a high strength-toweight ratio, such as fiberglass, each of said sections comprising an axially elongate generally semicylindrical shell of relatively thin uniform wall thickness, a plurality of radially offset circumferentially inwardly extending ribs integrally formed in each of said shells, the ribs on the respective shells being axially aligned with each other to extend continuously around the periphery of the tubular vault, each rib having a flat substantially horizontal first wall extending radially inwardly from the semicylindrical shell wall and a frusto-conical second wall integral with and inclined outwardly from the radially inner edge of said first wall to the semi-cylindrical shell wall, the first walls of said ribs being disposed on the upper side of said ribs when said tubular vault is in an upright position, to define a plurality of peripherally extending shelves in the interior of the vault, the uppermost one of said shelves being located in adjacent spaced relationship to the upper end of the vault to constitute a closure seat, said ribs further defining frustoconical channels in the exterior walls of said shell with the upper wall of said channels being substantially horizontal, means on the vertical edges of each of said sections for securing said sections together to form a tubular vault, and a cover closure comprising an upper and a lower member of sheet plastic material having a high strength-to-weight ratio, such as fiberglass, said lower layer being interconnected to said upper layer and having vertically extending rib sections having a depth substantially equal to the vertical spacing between said upper end of said vault and said uppermost one of said shelves.