Patent ID: 8888400

Claim:
A corrosion-resistant self-locking manhole cover, comprising: a cover plate comprising nonmetallic corrosion-resistant material adapted to rest on a manhole cover support surface of a manhole frame so as to be substantially flush with a top portion of said manhole frame and a surrounding surface in which said manhole frame is situated; an anchor on said cover plate comprising nonmetallic corrosion-resistant material, said anchor being adapted to engage said manhole frame at a first location in a manner that resists lifting of said cover plate proximate to said first location; a locking member on said cover plate comprising nonmetallic corrosion-resistant material, said locking member being movable between a locked position in which said locking member is adapted to engage said manhole frame at a second location in a manner that resists lifting of said cover plate proximate to said second location, and an unlocked position in which said locking member is not adapted to engage said manhole frame; and metallic components associated with said anchor and said locking member to perform mounting functions, rotary drive functions, and biasing functions, each of said metallic components comprising either a corrosion-resistant metal that is exposed to environmental gases or a metal that need not be corrosion-resistant but is sealed against exposure to environmental gases; wherein said support surface comprises an upper surface of an inwardly extending flange on said manhole frame and said anchor and said locking member are vertically adjustable to engage said manhole frame at or below a lower surface of said flange; wherein said anchor and said locking member are vertically adjustable to accommodate manhole frames with different flange depths; and wherein said anchor and said locking member are vertically adjustable between a first adjustment position wherein a first surface thereof is adapted to engage said manhole frame below said flange lower surface and a second adjustment position wherein said a second surface thereof is arranged to engage said flange lower surface of said manhole frame.