Corrosion-Resistant Self-Locking Manhole Cover

A corrosion-resistant self-locking manhole cover, comprising:

• a cover plate 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 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 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;
• said anchor, said locking member and said cover plate comprising nonmetallic corrosion resistant material;
• fasteners securing said anchor and said locking member to said cover plate, said fasteners being made of metal and sealed against exposure to environmental gases;
• a rotary drive mechanism operable to move said locking member between said locked position and said unlocked position, said rotary drive mechanism comprising a rotatable security lock made of metal and sealed against exposure to environmental gases;
• and
• a biasing mechanism operable to bias said locking member to said locked position, said biasing mechanism comprising one or more springs made of corrosion-resistant metal and being exposed to environmental gases.

A corrosion resistant self-locking manhole cover, comprising:

• a nonmetallic corrosion-resistant cover plate 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;
• a first nonmetallic corrosion-resistant locking member on said cover plate that is movable between a locked position in which said first locking member is 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, and an unlocked position in which said first locking member is not adapted to engage said manhole frame;
• a second nonmetallic corrosion-resistant locking member on said cover plate that is movable between a locked position in which said second 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 second locking member is not adapted to engage said manhole frame;
• a spring mechanism adapted to bias said first locking member and said second locking member to said extended position;
• an aperture in said cover plate;
• a fitting in said cover plate aperture having a metallic rotatable lock bolt with a nonmetallic corrosion-resistant exterior on a bottom side of said cover plate;
• a first drive arm operatively driven by said rotatable lock bolt, said first drive arm operatively engaging said first locking member and having a locking rotational position wherein said first locking member is in said extended position and an unlocking rotational position wherein said first locking member is in said retracted position;
• a second drive arm operatively driven by said rotatable lock bolt, said second drive arm operatively engaging said second locking member and having a locking rotational position wherein said second locking member is in said extended position and an unlocking rotational position wherein said second locking member is in said retracted position;
• said rotatable lock bolt comprising a security lock disposed in said cover plate aperture and adapted to receive a security key tool that applies a rotational torque to said locking pin actuator;
• a nonmetallic corrosion-resistant latch arm operatively driven by said rotatable lock bolt;
• and
• a nonmetallic corrosion-resistant latch on said cover plate adapted to releasably retain said latch arm in said unlocking rotational position without said security lock being engaged by said security key tool.