Abstract: A chair provided with a backrest for use in offices, etc., comprising an inner shell (2) and an outer shell (3). Conventional chairs of this type have a problem that there is little freedom in design with respect to strength and flexibility since only the inner shell serves as a structural member. An object of this chair is to increase the freedom. To this end, in the chair of this invention, the outer shell (3) as well as the inner shell (2) are formed as an integral body L-shaped in side view and comprising a seat portion (31) and a backrest portion (32), so that a three-dimensional shell structure is formed. In this chair, various measures are taken to solve the problem caused by the outer shell which is formed into an integral body. First, a fixed shell (6) is adopted for preventing a gap from being formed. Also, to obtain a required resiliency the shells (2, 3) are of such a construction as to allow a positional shift between the shells, and the inner shell (2) is supported by two brackets (118, 119).

Abstract: A chair with a backrest is arranged so that the seat can be shifted forwardly to a rest position upon a rearward inclination of the backrest. The front end of the seat is supported pivotably on a support base, and the seat is movable forwardly and rearwardly. A balancing member is provided below the seat, and the support base supports a fulcrum of the balancing member set between a front and rear point of action of the balancing member. A backrest is provided on the rear end of the balancing member, and a rear part of the seat is supported on the rear point of action of the balancing member through seat receiving means. An upward movement of the front point of action of the balancing member is translated by motion translating means to a forward movement of the seat.