An adjustment device for a chair, comprising an oscillating mechanism composed of a first plate, associated with a central gas-operated post for the height adjustment of a seat. A second plate is articulated to the first plate so that it can oscillate, by means of a pair of first pivots and is fixed to a backrest. A linkage is articulated to the first plate, by means of a second pivot, and is in turn articulated, by a third pivot, to a third plate, with which the seat can be associated. The third plate is articulated to the second plate. Elements are associated with the linkage for connection to at least one slat or leaf spring, which is arranged on a plane that is substantially parallel to the plane of the seat and is adapted to elastically contrast the inclination of the second plate with respect to the first plate.

An adjustment device for a chair, comprising an oscillating mechanism composed of a first plate, associated with a central gas-operated post for height adjustment of a seat, to which a second plate, fixed to a backrest, is articulated so that it can oscillate by a first pivot.

A third plate is articulated and interposed, respectively by a second pivot and a third pivot, between the first plate and the second plate, and can be associated with the seat.

The first plate has elements for connection to at least one slat or leaf spring which is adapted to elastically contrast the inclination of the second plate with respect to the first plate.

A body support structure includes a base, a seat and a backrest, with the backrest connected to the base with a torsion leaf spring. The torsion leaf spring may be configured with a plurality of fingers, and/or one or more flex regions. One or more struts may be connected between the seat or backrest and the base. In another aspect, the seat and/or backrest may be supported with one or more links that provide a counter-intuitive motion. In another aspect, a link may be coupled to a support with a flexible blade.

A chair, comprising, a backrest, a seat coupled with the backrest, a column coupled with the seat, a linkage statically attached to the backrest and rotatably attached below the seat, a leaf spring statically attached at one end and in contact with the linkage to provide a resistance to tilting of the backrest relative to the column, a first structure. A portion of the first structure has an arc shape that includes one or more teeth, and a second structure in contact with the first structure. The chair is configured such that, when a weight is applied to the seat, one or more teeth of the second structure move along the one or more teeth of the first structure to provide an increased resistance to tilting of the backrest relative to the column.

Disclosed herein is a chair that includes a backrest portion, a seat portion coupled with the backrest portion, a column portion coupled with the seat portion, a linkage coupled with the backrest portion, a leaf spring in direct contact with the linkage, an arc-shaped toothed structure fixed translationally relative to the column portion, and a different toothed structure in contact with the arc-shaped toothed structure. The chair is also configured such that when a weight is applied to the seat portion, a fulcrum point of the leaf spring moves as the different toothed structure moves along the arc-shaped toothed structure to thereby shorten a working length of the leaf spring and provide an increased resistance to tilting of the backrest portion relative to the column portion. A process for assembling the chair and a weight-based tilt-resistance assembly for use with the chair are also described herein.

A seating arrangement includes a seat portion, a back portion, a support member caused to move between first and second positions, and a back recline lock arrangement that includes an actuator, a lock member caused to move between a locked position when the actuator is in an engaged position where the lock member prevents the support member from moving from the first position toward the second position, and an unlocked position when the actuator is in a disengaged position, and wherein the actuator is configured to move from the disengaged position to the engaged position when the chair back is in the reclined position, and the lock member is prevented from moving from the unlocked position to the locked position until the back assembly is moved from the reclined position to the upright position.

A chair includes a base, a receptacle coupled to an upper end of the base, and a seat shell forming a seat surface. The seat shell is supported by the receptacle. The chair also includes a back shell forming a back surface. The back shell is connected to the seat shell on both sides of the seat surface and on both sides of the back surface. The back shell includes an extension extending from the back surface to the receptacle under the seat shell. The extension is elastically deformable.

A seating arrangement includes a seat portion, a back portion, a support member caused to move between first and second positions, and a back recline lock arrangement that includes an actuator, a lock member caused to move between a locked position when the actuator is in an engaged position where the lock member prevents the support member from moving from the first position toward the second position, and an unlocked position when the actuator is in a disengaged position, and wherein the actuator is configured to move from the disengaged position to the engaged position when the chair back is in the reclined position, and the lock member is prevented from moving from the unlocked position to the locked position until the back assembly is moved from the reclined position to the upright position.

A body support structure includes a base, a seat and a backrest, with the backrest connected to the base with a torsion leaf spring. The torsion leaf spring may be configured with a plurality of fingers, and/or one or more flex regions. One or more struts may be connected between the seat or backrest and the base. In another aspect, the seat and/or backrest may be supported with one or more links that provide a counter-intuitive motion. In another aspect, a link may be coupled to a support with a flexible blade.

A body support assembly includes a seat assembly and backrest assembly supported by a tilt control assembly. Methods of using and assembling the body support assembly are provided.