Patent ID: 7441835

Claim:
An angle-adjustable backrest device for a chair that includes a leg frame and a seat connected to the leg frame, said angle-adjustable backrest device comprising: a backrest frame; and an angle-adjusting device operable for connecting said backrest frame to the chair and for adjusting an angular position of the backrest frame relative to the leg frame, said angle-adjusting device including a mounting seat operable for mounting on the leg frame, the mounting seat having an inner side wall provided with a plurality of positioning components, a pivot seat operable for mounting on the seat, the pivot seat being connected to said backrest frame and pivoted to said inner side wall of said mounting seat, the adjustment of the angular position of the backrest frame relative to the leg frame resulting in rotation of the pivot seat relative to the mounting seat causing a simultaneous angular movement of the seat relative to the leg frame, and a locking unit including a slide member mounted slidably on said backrest frame, the slide member having one side formed with a positioning groove, said slide member being movable on said backrest frame from an engaging position, where said positioning groove engages a selected one of said positioning components on said mounting seat to lock said backrest frame at a desired angle relative to the leg frame, and a disengaging position, where said positioning groove is disengaged from said positioning components on said mounting seat to permit adjustment of the angle of said backrest frame relative to the leg frame, a first biasing member for biasing said slide member to the engaging position, and an actuator unit connected to said slide member, the actuator unit being operable to drive movement of said slide member from the engaging position to the disengaging position.