Patent ID: 6857300

Claim:
A locking device for a door a latch mechanism comprising a latch bolt, latch bar coupled to the latch bolt and rotatable to retract the latch bolt, and door handles connected to opposite ends of the latch bar for rotating the latch bar to cause retraction of the latch bolt, the locking device being operable in response to turning of one door handle to prohibit turning of the latch bar by the other door handle, the locking device comprising: rotatable first locking means comprising first coupling means for coupling to the latch bar; second locking means for engaging said rotatable first locking means and preventing turning thereof; and cam means for controlling operation of said second locking means, said cam means comprising second coupling means for coupling to the latch bar; said rotatable first locking means and said cam means being turnable relative to one another when coupled to the latch bar by the respective first and second coupling means thereof so that said second locking means is operable to engage said rotatable first locking means in response to turning of said cam means in one direction relative to said rotatable first locking means and so that whereafter said second locking means is operable to disengage from said rotatable first locking means upon turning said cam means in an opposite direction; said rotatable first locking means comprising a rotatable locking member and detent means on a periphery thereof, and said second locking means comprising a movable locking member operatively controlled by said cam means for engagement with said detent means.