Patent ID: 7775593

Claim:
An adjusting device of a chair backrest, said adjusting device comprising: a movable base provided with an adjusting opening in a front wall, said adjusting opening having plural continual V-shaped grooves in two vertical sidewalls respectively, a bottom portion of said adjusting opening formed with a stopping groove and a top end of said adjusting opening formed with a projecting-downward portion, said movable base further having a sliding rail formed in two sides respectively; a connecting block fitted in said movable base and provided with a side wing formed at two vertical sides respectively for plugging inside said sliding rail of said movable base, a rectangular recess formed in a front wall of said connecting block and provided with a projection on an intermediate portion and a through hole bored below said projection; and a positioning unit assembled within said rectangular recess of said connecting block and provided with two upholding feet respectively bored with a pivotal hole, a pivotal pin used to be inserted through said pivotal holes of said upholding feet and said through hole of said connecting block and then fixed with a washer by pressing so as to keep said positioning unit jointed with said connecting block, one of said upholding feet provided with a locking projection corresponding to a locking groove provided in another said upholding foot, a spring installed between an inner wall of said upholding feet to expand said upholding feet to fit in one of plural pairs of said V-shaped grooves of said adjusting opening of said movable base.