An oscillation system (1) for chairs includes a backrest support (3) oscillating about a rotation axis (4), a first support element (6) of the seat coupled to the frame (2) to assume, in the at rest position of the backrest support (3), a plurality of relative vertical positions with respect to the frame (2) depending on, and by effect of, a weight force applied to the first support element (6). A first elastic element (21) opposes an elastic reaction to the backrest support oscillation with respect to an at rest position of the backrest support (3). A lever (31) connects to the first support element (6) to be rotated by the first support element (6) during variation of the relative position, and connects to the first anchoring end (22) to displace the first anchoring end (22). A fulcrum axis (60) does not coincide with the rotation axis (4).

An armchair includes a base, a backrest pivotally connected to the base by a first rotating shaft, an armrest connected to the base and an elastic assembly fixed on the armrest. The backrest and the elastic assembly are pivotally connected by a second rotating shaft. The elastic assembly is configured to provide elastic force when the backrest swings around the first rotating shaft. The elastic assembly arranged between the backrest and the armrest permits the backrest to be able to swing relative to the base. In use, the elastic assembly controls the swing amplitude of the backrest according to the pressure exerted by the user's back on the backrest. When the user reclines backward, the elastic assembly acts as a cushion to support the backrest to slowly swing backward due to the elastic force. When the user rises, the elastic force of the elastic assembly urges the backrest to reset.

A spring actuated rocking mechanism can be attached to the legs of a collapsible chair to allow for the user to rock in the collapsible chair. The mechanism may be attached at the factory or retrofitted to the chair. The rocking mechanism can be attached to the end of a leg or disposed within a leg, having a leg portion above and below the mechanism.

A motion seat is described that includes a chassis, a seat frame, a seat cushion, a backrest, and a resilient hinge. The seat frame is attached to the chassis and the seat cushion and the backrest are each attached to the seat frame. The resilient hinge formed as a unitary body and may be formed from a resilient polymer. The seat cushion and/or the backrest is pivotably attached to the seat frame with the resilient hinge

A chair according to the present invention has a reference position P located midway in a front-back direction in a movable range of a seat 2. The chair includes a return force generation mechanism 4 configured to generate a return force in a direction to return the seat 2 moved from the reference position P at least in the front-back direction to the reference position P. The return force generation mechanism 4 includes an elastic member 40 configured to increase the return force in the direction to return the seat to the reference position P as the amount of movement of the seat from the reference position P increases.

A chair can include a chair back, or backrest, that is coupled to a base of a chair above a seat of the chair. A tilt mechanism can attach the backrest to the base. In some embodiments, the tilt mechanism can be configured so that the backrest rotates about multiple pivots as it reclines from an upright position to a reclined position to drive motion of the seat during recline of the backrest.

A motion seat is described that includes a chassis, a seat frame, a seat cushion, a backrest, and a resilient hinge. The seat frame is attached to the chassis and the seat cushion and the backrest are each attached to the seat frame. The resilient hinge formed as a unitary body and may be formed from a resilient polymer. The seat cushion and/or the backrest is pivotably attached to the seat frame with the resilient hinge.

A chair assembly includes a supporting frame disposed above a base and including a first guiding groove. A seat is pivotably connected to a backrest. Lower and front guiding wheels are mounted to rear and front ends of the seat, respectively. At least one operating board includes rear and front ends respectively having second and third guiding grooves. The lower guiding wheel is movably received in the first and second guiding grooves. The front guiding wheel is movably received in the third guiding groove. A first operating rod is pivotably connected between the supporting frame and the seat. When the operating rod retracts, the lower guiding wheel is located in rear ends of the first and second guiding grooves, and the front guiding wheel is located in a rear end of the third guiding groove. The seat moves downwards and rearwards, and the front end of the seat inclines upwards.

An armrest device for adjusting an inclination angle of a backrest. The armrest device includes a side connecting bracket and an armrest. A lower end of the side connecting bracket is fixedly connected with a seat cushion. Right ends of the side connecting bracket and the armrest are rotatably connected with the backrest. An upper end of the side connecting bracket is fixedly connected with a positioning seat. An upper end of the positioning seat extends to an inner cavity of the armrest. The positioning seat shifts the inclination angle of the backrest and limits a position of the backrest through a positioning mechanism. A first spring limiting a movement of the armrest in an X direction and a second spring limiting a movement of the armrest in a Z direction are disposed between the positioning seat and the armrest.

A spring actuated rocking mechanism can be attached to the legs of a collapsible chair to allow for the user to rock in the collapsible chair. The mechanism may be attached at the factory or retrofitted to the chair. The rocking mechanism can be attached to the end of a leg or disposed within a leg, having a leg portion above and below the mechanism.