| 摘要 |
PROBLEM TO BE SOLVED: To easily adjust the angle of a backrest by providing an operation member for separating a slider restricting the rotation of a nut which is locked in a lower bracket from the lower bracket. SOLUTION: An operation handle 71 is rotated by a half degree in a lock state. When a backward load is added to backrest in this lock release state, the seat back is gradually inclined backward since the nut A9 of an upper bracket 1 is screwed onto the lead screw part of a connection shaft 3. When the operation handle 71 is returned to an original state after the backward inclination of backrest, the slider 5 is moved by the elastic force of compression coil spring 35 and a spring 6, the rotation of the nut B4 is restricted and the lock state is obtained. Besides, unless the backward load is added to the backrest in the lock release state, the seat back is rotated by the elastic force of a return spring 12 in a forward inclining direction. In this case, it is gradually rotated since the nut A9 of the upper bracket 1 is screwed onto the lead screw part of the connection shaft 3.
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