Improvements for systems with differential shaping of back supports of office chairs

摘要

An office chair comprises a seat (A) and a back (D) made with two independently-adjustable spinal support sections, one for the thoracic and the other for the lumbar region of the spine. The back is connected by a bar (3) to a control box (B) beneath the seat equipped with two torsion bars (1,5) - one for the bar (3) and the other for columns (6) pivoted to the lumbar support section of the seat back and having different levels of elastic resistance. The seat back is made from glass fibres embedded in polyester foam, and the two torsion bars are positioned so that they act in sequence, the second coming into operation after the first.