Deadbolt mechanism for holding a door in a closed position and including a deadbolt pivotally connected to the mechanism housing for movement into and out of that housing to adopt inoperative and operative positions respectively. A pin tumbler lock is used to operate the deadbolt and the lock barrel...http://www.google.com/patents/US4387918?utm_source=gb-gplus-sharePatent US4387918 - Deadlock mechanism
