Patent ID: 7134722

Claim:
A chair comprising a backrest having a backrest body comprising a hollow core material made of elastic material forming an outer share of the backrest and surrounded by an upholstery material, the backrest body further comprising an upper reinforcing member comprising a rigid material shaped as a downward facing channel and arranged at an upper backside of the backrest body, wherein the backrest is transformable, the backrest further comprising a lumbar support portion, an upper portion above the lumbar support portion and supported by the upper reinforcing member, and a lower portion between the lumbar support portion and a bottom end of the backrest wherein the lumbar support portion that is not supported by the upper reinforcing member can be transformed, and the lumbar support portion is bent to project forward to provide lumbar support; a backrest supporting portion for supporting the lower portion of the backrest in a slidable manner, wherein the lower portion slides in a slanted upward and forward direction; and an operating portion that selects and fixes a position A at which the backrest is slid, wherein the upper portion of the backrest is supported in a rotatable manner around a horizontal axis or in a slidable manner and the backrest can be transformed in compliance with the position A fixed by the operating portion, wherein the backrest supporting portion further comprises a guide mechanism for guiding the lower portion of the backrest in a linearly slidable manner in a slanted upward and forward direction perpendicular to the thickness direction of the lower portion, wherein when sliding, the lower portion of the backrest does not transform and remains oriented in the same direction.