Patent ID: 8162393

Claim:
A headrest comprising: a base member assembled to a seat back; a support plate assembled to the base member by a link mechanism; a lock mechanism which is unlocked when a vehicle is crashed from behind so that the link mechanism operates along with an unlocking operation of the lock mechanism, whereupon the support plate springs out to receive a back of a passenger's head; a return prevention mechanism configured to prevent the support plate from returning to an initial position thereof achieved before the support plate springs out, by a load imposed by the back of the passenger's head during the course of the support plate springing out, wherein the return prevention mechanism includes: a ratchet including a step at an outer peripheral surface there; and a stopper rotatably attached to the base member configured to engage with the step of the ratchet, wherein the stopper includes a hook portion, and wherein the stopper is provided to be switchable between a first state in which the stopper is urged in a first rotating direction to engage with the step of the ratchet and a second state in which the stopper is urged in a second rotating direction opposite to the first rotating direction, and wherein after the support plate has sprung out, while performing an operation for returning the sprung-out support plate to the initial position thereof, by switching an urging direction of the stopper from the first rotating direction to the second rotating direction, the step of the ratchet interferes with the hook portion of the stopper, whereupon the urging direction of the stopper switches from the second rotating direction to the first rotating direction.