| 摘要 |
A backrest adjusting device is provided to completely protect the user's waist with a curved part and to enable a user to move the waist by moving a backrest to the left or right side or turning the backrest while the user leans against the backrest. In the backrest adjusting device having a backrest of which the lower end is fixed or rotatably connected to the end of a back plate support board(1) installed in the rear side of a seat(20) of a general chair, a sitting-down type chair, or a rocking chair, the back plate support board is extended upward. A hinge(3) is installed at the upper end of the back plate support board and rotatably combined to a hinge shaft(7) protruded in the middle of a back plate(5). A spring support shaft(9) is installed at the lower end of the back plate. A spring(12) is mounted on the rear side of the back plate support board and joined by a fixing nut(14). A curved part(18) is formed in the front side of a lower end of the backrest.
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