Patent ID: 7364231

Claim:
A self locking device of an active headrest, the active headrest comprising a panel disposed inside a seat back frame, a panel link coupled to the panel to support the panel and rotate in response to a raising of the panel, and a frame which is raised by the panel, wherein the self locking device comprises: a guide cylinder configured to be disposed in the seat back frame such that the guide cylinder is covered by the panel link at a non-operated position of the active headrest and exposed at an operated position of the active headrest, and defining a receiving indentation therein; a return spring in the receiving indentation; and a locking piston in the receiving indentation, a first end of the locking piston being coupled to the return spring, and a second end of the locking piston being exposed to outside the guide cylinder, wherein the locking piston is kept in the guide cylinder by the panel link at the non-operated position of the active headrest, and pressed outside of the guide cylinder by the return spring to restrain rotation of the panel link at the operated position of the active headrest.