Retained key double cylinder deadbolt

A retained key double cylinder lock deadbolt including:

• a. a locking deadbolt assembly with a deadbolt slidable from a retracted position to a locking position;
• b. a pair of cylinder lock assemblies, one being an outside cylinder lock and the other being an inside cylinder lock;
• c. a locking cylinder in each cylinder assembly;
• d. deadbolt actuating means operated by either locking cylinder when the locking cylinder is operated with a proper key for moving the deadbolt from retracted position within the housing to locking position;
• e. a pair of proper keys, one for each of the inside locking cyclinder and one for the outside locking cylinder;
• with means for retaining the inside key by the improvements comprising:
• f. notch means in the inside key only;
• g. mechanical latch means adjacent the locking deadbolt assembly and cooperating with the cylinder lock assemblies to be operable by the outside locking cylinder, the mechanical latch means cooperating with the notch means in the inside key to retain the inside key in the inside locking cylinder unless released by operation of the outside locking cylinder under operation of the outside key;
• h. and means preventing operation of the inside locking cylinder by the outside key.