US Patent 11220839 Dead locking latch assembly

A latch assembly is provided where the latch is moveable to open and close a door by operation of a dead lock assembly that blocks or unblocks movement of a bolt. In a blocked state, a blocking cartridge of the dead lock assembly is prevented from inward movement, blocking inward movement of the bolt. Turning a door knob or door handle causes a spindle extending through the dead lock assembly to move locking bars of the dead locking assembly, the locking bars moving further apart to permit the blocking cartridge to slide there between and move inwardly into the latch housing. The bolt can now move inward by force of the door jamb upon the bolt in order to clear the door jamb when opening and closing the door.