Self-locking manhole cover

A 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 that is 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;
• a biasing mechanism on said cover plate adapted to bias said locking member to said locked position;
• a rotatable locking mechanism on said cover plate engaging said locking member and having a locking rotational position wherein said locking member is in said locked position and an unlocking rotational position wherein said locking member is in said unlocked position;
• said locking mechanism having a security lock adapted to receive a security key that applies a rotational torque to said locking mechanism;
• and
• a latch on said cover plate adapted to releasably retain said locking mechanism in said unlocking rotational position without said security lock being engaged by a security key.

A 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 member 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 pin on said cover plate that is movable between a locked position in which said locking pin 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 pin is not adapted to engage said manhole frame;
• a spring mechanism adapted to bias said locking pin to said extended position;
• an off-center aperture in said cover plate;
• a fitting in said cover plate aperture having a rotatable lock bolt;
• a locking pin actuator operatively driven by said rotatable lock bolt, said locking pin actuator engaging said locking pin and having a locking rotational position wherein said locking pin is in said extended position and an unlocking rotational position wherein said locking pin 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 latch arm operatively driven by said rotatable lock bolt;
• and
• a 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.