Abstract: An office chair is provided. The office chair includes an eccentric adjustment of the tilt of the seat surface. In order to prevent against undesired tilt adjustments, it is provided to use a rotating shaft with a manipulation part and a functional part for the eccentric adjustment and to control a disengageable locking catch, which blocks any rotating angle adjustment of the functional part of the rotating shaft in the non-disengaged state by the manipulation part in a first rotating angle region.

Abstract: An office chair is provided. The office chair includes a seat back that can follow the motions of the upper body of a person seated in the seat. The seat back of the office chair includes a restoring spring in the form of a mechanical screw pressure spring. A piston is coaxially disposed in the screw pressure spring. The piston inserts in a piston sleeve, whereby the piston has locking pieces that can be extended radially to the outside, which are placed on the peripheral edge of the piston sleeve in the hooked-out state and in a largely extended position of the piston.