Abstract: The chair of the present invention includes a seat, a backrest, an elastic member, and a support structure. The elastic member is configured to elastically deform in a vertical direction and a first direction due to rotation of the backrest, and is configured to apply a restoring force caused by the elastic deformation to the seat and the backrest to return the seat and the backrest to an initial position.

Abstract: The chair of the present invention includes a seat, a backrest, and a support structure supporting the seat and the backrest. The backrest includes an arm portion and a back support portion. The support structure includes a first shaft portion, a second shaft portion, a third shaft portion, a fourth shaft portion, a support base, an arm support portion, and a support link.

Abstract: A rotatable office chair comprises at least two seat carriers, each further comprising an upper arched guide and a lower arched guide, and at least two back rest carriers, each further comprising a restrictedly guided region, and a back rest arranged on back rest carriers, wherein the restrictedly guided region of the at least one back rest carrier is guided between the upper arched guide and the lower arched guide of the at least one seat carrier, thus allowing the at least one back rest carrier to be inclined relative to the seat carrier, wherein the upper arched guide and the lower arched guide are embodied at least in certain regions as an arc of a circle portion and wherein the arc of a circle portion of the upper arched guide and the arc of a circle portion of the lower arched guide have the same center of a circle.

Abstract: The present invention relates to a chair or armchair, in particular a rotatable office chair, comprising: at least two seat carriers, each further comprising an upper arched guide and a lower arched guide, and at least two back rest carriers, each further comprising a restrictedly guided region, and a back rest arranged on back rest carriers, wherein the restrictedly guided region of the at least one back rest carrier is guided between the upper arched guide and the lower arched guide of the at least one seat carrier, thus allowing the at least one back rest carrier to be inclined relative to the seat carrier, wherein the upper arched guide and the lower arched guide are embodied at least in certain regions as an arc of a circle portion and wherein the arc of a circle portion of the upper arched guide and the arc of a circle portion of the lower arched guide have the same centre of a circle H.