Abstract: A fire-retardant pivoted door assembly with fire activated latching members includes a metal door frame having jambs and a header in which a fire-retardant door is mounted by a hinge assembly with a lower temperature resistance that the door and frame. Fire actuated latch bolt assemblies in the door are spaced vertically along the hinge side of the door, and include a housing providing an elongated cavity opening at the edge of the door. A latch bolt is slidably seated in the cavity and is biased towards the opening of the cavity. A fusible closure extends across the opening of the cavity and retains the latch bolt against the biasing pressure, and the hinge jamb has a spaced recess formed therein to receive the latch bolt upon melting of the fusible closure.

Abstract: A door latch assembly 10 includes a rack 102 which is moved upon depression of a thumbpiece 12. Movement of the rack 102 results in rotation of an enmeshed pinion 136 and an assembled spindle 152. As the spindle 152 rotates, a latch 26 is moved from a latched position to an unlatched position to thereby permit opening of a door 20 on which the door latch assembly is mounted.When it is desired to lock the door 20, a key-operated lock cylinder 16 is operated to place into motion facilities for moving the rack 102 into a disabled poisition whereafter depression of the thumbpiece 12 will not result in movement of the rack.As the rack 102 is moved to the disabled position, teeth 104 of the rack remain enmeshed with teeth 138 of pinion 136. When the rack 102 is again moved to the enabled positon, the teeth 104 and 138 remain enmeshed and thereby avoid any deleterious reactions had they been separated upon disablement of the rack 102 and re-enmeshed upon enablement thereof.