Locking mechanism for armrest

Claim 1

A locking mechanism for an armrest, in which the armrest is rotatably mounted on a lateral wall of a seat back of a seat so as to be vertically rotatable between a non-use upright position and a use horizontal position, said locking mechanism comprising: a shaft provided at said lateral wall of said seat back, said shaft being adapted to rotatably support said armrest; an arcuate slot formed at said lateral wall of said seat back such said slot lies forwardly of said shaft and a center of a circle along which said arcuate slot lies is disposed at said shaft coaxially; an upper catching means and a lower catching means, each being formed at an upper end of said arcuate slot and a lower end of said arcuate slot, respectively, in such a manner that said upper catching means has a part-way open communication with said upper end of said arcuate slot, and that said lower catching means has a part-way open communication with said lower end of said arcuate slot; a pair of first opposed projections projecting from said arcuate slot for defining a first narrow space between said upper catching means and said upper end of said arcuate slot; a pair of second opposed projections projecting from said arcuate slot for defining a second narrow space between said lower catching means and said lower end of said arcuate slot; a stopper pin provided on said armrest, said stopper pin being slidably inserted through said arcuate slot; and an elastic means mounted on said stopper pin, said elastic means being resiliently deformable and adapted to cause said stopper to be securely caught in either of said upper and lower catching means, whereby, when said armrest is rotated downwardly to said use horizontal position, said stopper pin and elastic means are slidably displaced along said arcuate slot, with said elastic means being resiliently deformed at said second narrow space, and then securely caught in said lower catching means due to a resilient recovery force of said elastic means, and when said armrest is rotated upwardly to said non-use upright position, said stopper pin and elastic means are slidingly displaced along said arcuate slot, with said elastic means being resiliently deformed at said first narrow space, and then securely caught in said upper catching means due to said resilient recovery force of said elastic means.