Lockset with motorized system for locking and unlocking

A door lock, preferably operable both by a mechanical key with a key cylinder and by an electronic signal and having inside and outside handles mounted on inside and outside hollow spindles, for mounting on a door having an inside face and an outside face, has a cylindrical lock chassis with a provision for retracting a latch bolt in response to rotation of either of the hollow spindles; a member for selectively locking the outside spindle against rotation; a reversible electric motor mounted coaxially within the inside spindle, the motor being secured against rotation but free to slide axially against resistance provided by a biasing member, and having a motor shaft extending through the cylindrical lock chassis to operably engage the member for locking the outside spindle; a power supply for the motor; and a mechanism for selectively moving the member between locked and unlocked positions.