Lock assembly for automatically dead bolting a closure

A lock assembly for automatically dead bolting a closure, such as a fire safety door, to a closure frame, such as a fire safety door jamb, in the event of fire raising the ambient temperature about a predetermined temperature, said lock assembly comprising:

• A. striker plate means, for defining a bolt hole, mounted on one of said closure and closure frame;
• B. a cooperating latching assembly mounted on the other of said closure and closure frame and including:
• 1. a housing,
• 2. a bolt assembly mounted on said housing for reciprocal movement to and from a latched position projecting into said bolt hole and for further movement to an extreme dead bolted position projecting into said bolt hole beyond the latched position,
• 3. stop means operable when said bolt assembly is moved to the dead bolted position to prevent movement of said bolt assembly out of said dead bolted position,
• 4. means for urging said bolt assembly toward the dead bolted position;
• and
• 5. bolt actuator means for moving said bolt assembly to and from its latched position and ultimately to its dead bolted position, said actuator means comprising,
• a. crank means,
• b. substantially inextensible cable means for interconnecting said crank means and said bolt assembly, and
• c. means, disintegratable at the predetermined temperature,
• 1. for guiding said cable means through a first non-linear path of active length sufficient only to permit said bolt assembly to be reciprocated to its latched position;
• and
• 2. for disintegrating at the predetermined temperature to permit said cable means to traverse a second path of active length sufficient to permit said bolt assembly to be reciprocated to the dead bolted position.