US Patent 7815257 Adjustment device for adjustable chairs

Adjustment device for chairs, comprising a back support capable of rotating around a shaft fastened to a support base, said support for the backrest being provided with a blocking plate having a plurality of openings, an insert capable of limited movement in a defined track in the support base to engage and disengage said openings, and an actuator connected to said insert, in which the actuator is operated by a rod connected to a handle that can be operated by the user, said actuator being movable between a release position and a lock position, in which said insert is selectively engaged in one of said openings.