Patent ID: 7758124

Claim:
A seat apparatus for a vehicle, comprising: a seat cushion; a lower arm supported on the seat cushion; a seat back; an upper arm supported on the seat back; an intermediate arm having a first hinge shaft and a second hinge shaft on which the lower arm and the upper arm are rotatably mounted, respectively; a reclining mechanism disposed between the lower arm and the intermediate arm, the reclining mechanism selectively restraining and allowing the intermediate arm to rotate around the first hinge shaft relative to the lower arm for adjusting a tilt angle of the seat back relative to the seat cushion within a predetermined angular range; and a lock mechanism disposed between the intermediate arm and the upper arm, the lock mechanism selectively restraining and allowing the upper arm to rotate around the second hinge shaft relative to the intermediate arm for establishing a forward folding movement of the seat back onto the seat cushion; the lock mechanism including a first plate member, a second plate member, and a pawl gear, the first plate member being fixed to one of the upper arm and the intermediate arm, the first plate member being provided therein with a plurality of circumferentially spaced internal tooth sections each of which has a plurality of teeth with different face widths, the second plate member fixed to the other one of the upper arm and the intermediate arm, the second plate member supported by the first plate member to rotate relative thereto, the pawl gear slidably supported by the second plate member and having a circumferentially arranged external tooth section each of which has a plurality of teeth with different face widths for engaging with and disengaging from one of the internal tooth sections.