Sealing manhole cover for use on existing unsealed sanitary sewer manhole cover frames

Claim 1

A manhole cover for reception in a conventional manhole cover frame having a horizontal flange extending peripherally around an opening, said manhole cover having a horizontal peripheral portion adapted to rest on said ledge, the novelty comprising, an imperforate upper surface of said cover extending entirely across the cover broken only by a blind pocket to receive a manhole opening tool, and an O-ring groove extending around the lower surface of said horizontal peripheral portion of said cover at a location such that when the cover is installed in a standard manhole cover frame the O-ring groove will be located over the horizontal flange of a said frame, said groove being downward opening and rectangular in radial cross section, and spaced inwardly from the periphery of said cover, and an O-ring having a generally circular radial cross section with a diameter sufficiently greater than the radial width of said groove that said O-ring must be compressed slightly to place it in the groove, said groove having a vertical depth slightly more than half the diameter of the O-ring whereby the O-ring is retained in said groove by compression of its diameter and has a portion projecting downwardly from the groove whereby to engage the flange of a said manhole cover frame when said manhole cover is installed in a said frame.