Reclining device of seat

Claim 1

A reclining device of a seat which has a seat cushion and a seatback, said reclining device comprising: a base member secured to said seat cushion; a hinge arm secured to said seatback and pivotally connected through a first pivot pin to said base member so that said seatback is pivotal relative to said seat cushion; a lock plate member movable with said hinge arm, said lock plate member being formed with a first toothed portion; a lock lever pivotally connected through a second pivot pin to said base member, said lock lever being formed with a second toothed portion which is latchingly engageable with said first toothed portion of the lock plate member when said lock lever assumes a given angular position; an operation lever pivotally connected through a third pivot pin to said base member for actuating said lock lever, said operation lever being pivotal between a first position to render said lock lever to achieve a latched engagement with said lock plate member through said first and second toothed portions and a second position to render said lock lever to cancel said latched engagement; first means for biasing said operation lever in a direction to bias said lock lever to achieve said latched engagement with said lock plate member; second means for urging said lock lever to keep the latched engagement between said lock lever and said lock plate member when, with said operation lever assuming said first position, an external force is applied to said lock lever in a direction to separate said lock lever from said lock plate member, said second means comprising a part of said lock lever, said part being formed with a recess which leaves at both sides thereof first and second lugs, and arm section integrally and non-movably formed on said operation lever, said arm section extending into said recess of the lock lever, wherein due to the work of said first means, said arm section is pressed against said first lug of said lock lever thereby to bias said lock lever in a direction to achieve the latched engagement with said lock plate member; and said hinge arm, said lock lever and said operation lever are so arranged that when said operation lever assumes said first position, said arm section of said operation lever is placed on an opposite side of said second pivot pin of the lock lever with respect to an imaginary line which passes through both said first pivot pin of the hinge lever and said third pivot pin of said operation lever and, when said operation lever assumes said second position, said arm section of said operation lever is placed on the same side as said second pivot pin with respect to said imaginary line.