Task-Based Design of Manipulators: An Agent-Based Approach

A changeable combination key lock for safe deposit boxes and the like, wherein a guard key is insertable into a rotatable guard key plug to set guard key tumblers to permit retracting movement of a bolt, and a renter's key is insertable into a rotatable renter's key plug for engagement with normally coupled segmented tumblers to aline them to permit retraction of the bolt. A cam member is provided to be actuated by a change key which is inserted into the guard key plug when the guard key has been removed and the bolt is retracted, to disengage gating portions of the segmented tumblers from the remaining portions of such tumblers, whereupon a new renter's key may be inserted and the segmented tumblers set for the key configuration of the new renter's key.