Patent ID: 8191970

Claim:
A backrest device in a chair, the backrest device comprising: a back frame including: a flexible back plate having a front major surface, a back major surface and a thickness measured from the front major surface to the back major surface, a right lower end and a left lower end, each of the right and left lower ends being supported by a backrest support member; and the flexible back plate including: a plurality of openings, one or more horizontal portions, each horizontal portion of the one or more horizontal portions positioned between a first opening of the plurality of openings and a second opening of the plurality of openings, the first opening adjacent the second opening in a vertical direction of the flexible back plate, the flexible back plate having a first thickness at each horizontal portion; and one or more vertical portions, each vertical portion positioned between the first opening and a third opening adjacent the first opening in a horizontal direction of the flexible back plate, the flexible back plate having a second thickness at the one or more vertical portions, wherein the first thickness is smaller than the second thickness.