Security chain lock for doors

摘要

A security chain lock for doors features a chain housing and guideway attached to the interior side of the door and coupled securely to door lock cylinder housing means. An extension of the chain housing laps the edge of the door through which the door lock bolt projects and is firmly anchored to such edge. A keeper mounting bracket is rigidly secured to the inner face and to the edge of the door frame which faces the door edge. A keeper housing is pivotally secured to said mounting bracket and receives a spring-urged keeper projecting from a reciprocatory release element joined to the keeper housing and adapted to enter an inaccessible chamber of the door frame when the keeper housing is pivoted in response to partial door opening from the inside while the chain lock is active. A coacting latch element connected with the extensible and retractable chain means is shiftable by an interior knob into active coupling engagement with the keeper in the keeper housing. The latch element and chain means are resiliently biased to retracted positions within the chain housing.