Safety mechanism for preventing the locking up of persons in cabinets

Claim 1

A strong room structure including a frame member providing an entrance opening, a door member mounted in said frame member, and a mechanism for preventing unauthorized closing of said door when at least one person is present on the floor of said room, said mechanism comprising a primary bolt carried by one of said frame and door members and displaceable between a retracted inoperative position and a protruded operative position whereby in said operative position said primary bolt prevents closing of said door by abutment against the other one of said frame and door members, first spring means normally urging said primary bolt toward said operative position, a first electromagnet having sufficient strength when energized to retain said primary bolt in said inoperative position against the action of said first spring means, an auxiliary bolt carried by said one of said frame and door members and displaceable between a retracted inoperative position and a protruded operative position for preventing retraction of said primary bolt from the operative position of said primary bolt, second spring means normally urging said auxiliary bolt towards its operative position, a second electromagnet having sufficient strength when energized to retain said auxiliary bolt in said inoperative position against the action of said second spring means, an electric circuit for actuating said first and second electromagnets and including a normally closed first switch adapted to be automatically opened by the weight of a person entering said room and a second independently operable switch for actuating said first and second electromagnets.