A chair includes a base having two sideboards. Each sideboard includes first and second coupling portions respectively at rear and front portions thereof. A seat is mounted on the base. A third coupling portion and a fourth coupling portion are provided on each lateral side of the seat. Each fourth coupling portion is coupled to one of the second coupling portions of the base. The seat is movable in a longitudinal direction and has a front end supported by the second and fourth coupling portions. A positioning device is coupled with the third coupling portion of the seat and the base, providing support for the rear end of the seat. The positioning device positions the seat relative to the base. A backrest is mounted to a rear of the base and is pivotably connected to the rear end of the seat and the sideboards.

A gravity self-adapted chassis of chair has the first plug pin, second plug pin, third plug pin, forth plug pin, tilting plate, first connecting rod, and the second connecting rod of the chassis form into a four-point connecting rod mechanism so as to form the conduction of the force, the backrest is fixedly connected with the tilting plate to offer the driving force of the four-point connecting rod mechanism, the gravity applied onto the seat by the users forms into the reset force applied onto the four-point connecting rod mechanism through the third plug pin hinged with the bracket, and the driving force and the reset force of the four-point connecting rod mechanism form into the confrontation relationship.

A seating unit component assembly comprises a support component that includes a first surface adapted to abut a seated user, a second surface opposite the first surface, a first end surface, a second end surface opposite the first end surface, and a pair of side surfaces extending between the first and second end surfaces, and a cover having a plurality of sides that cooperate to form an interior space that receives the support component therein, wherein the cover includes a first portion comprising a non-fabric substantially flexible thermoplastic material covering at least a portion of at least one of the side surfaces of the support component, a second portion comprising a fabric covering at least a portion of the first surface and at least a portion of the first end surface of the support component, and a third portion comprising a substantially rigid overlay covering at least a portion of the second end surface and at least a portion of the second surface.

A mechanism for an office chair has a base support which is placeable on a chair column. A seat support is arranged on the base support and is movable relative to the base support. A backrest support is coupled with the seat support. Pivoting the backrest causes the seat support to move relative to the base support. An alternative solution for adjusting the tilting resistance of the seat support of an office chair is provided where the tilting resistance of the seat support is influenced by the pivoting resistance of the backrest support.

A seat structure comprises a base configured to be a chair base assembly; a seat support located above the base, wherein a front part of the seat support has rotary connection with the front part of the base through a transition link; a chair back assembly having rotary connection with a rear part of the base through a pivot; a lever driving member linked between the chair back assembly and the seat support, and having rotary connection with a rear part of the seat support, wherein the lever driving member and the seat support are approximately on the same surface. When the chair back assembly rotates rearward around the pivot from the initial position, the rear part of the seat support is raised diagonally to the rear through the lever driving member, meanwhile the transition link and the front part of the seat support are pulled up.

An adjusting mechanism is provided for selectively setting a restoring force acting on a backrest of a chair. In a biasing unit of the adjusting mechanism, a spring segment is disposed between a head end and a follower end to bias the follower end to the remote position. The follower end is angularly movable on a cam surface between distal and proximate positions. In response to movement of a backrest of the chair from a normal position to an inclined position to permit the follower end to be forced by the cam surface to move from the remote position to a close position, two different restoring forces can be set by adjusting the follower end between the distal and proximate positions.

A device for adjusting the tilt of a chair backrest having a backrest frame rotatable with respect to the base frame of the chair is provided. The device includes elastic means for returning the backrest and/or countering the rotation thereof, in addition to means for controlling the preload of the elastic means. The means for controlling the preload include at least one first connecting rod and at least one first crank. The first connecting rod is hinged to the first crank and constrained to the elastic means so as to move the point of application of the returning and/or countering force with respect to the backrest. Adjusting means to adjust the position of the first crank determine at least two distinct stable positions of the first crank corresponding to two distinct positions of the mentioned point of application of the returning and/or countering force with respect to the base frame.

An oscillation mechanism for chairs includes a support frame, a structure coupled to the support frame to rotate about a first axis, an elastic element interposed between the support frame and the structure and configured to oppose a reaction force to an oscillation of the structure. The reaction force generates a reaction moment acting on the structure with respect to the first axis. An oscillation adjustment system is able to vary the reaction moment with the oscillation being unchanged. The adjustment system includes a pin movably coupled to the structure and a movement system of the pin for varying the distance between the pin and the first axis. The elastic element is directly fastened to the pin so that the reaction force is transmitted to the structure with the application point corresponding to the pin and with direction and orientation unchanged.

A flexible support device for chair back tilting contains: a supporting frame, a seat mounting, and a base. The supporting frame includes a back portion, two peripheral extensions, two rotatable edges, two first coupling orifices, and two second coupling orifices. The seat mounting includes a first fixing portion, a second fixing portion, two connecting fences, two rotatable locating portions, two defining orifices, two joining elements, two slide orifices, and a drive protrusion. The base includes two locating fringes with two first positioning orifices, two second positioning orifices, a holder connected with a first end of a spring, and a second end of the spring is connected with a flexible sheet. The flexible sheet has two peripheral sections. The base further includes two connection segments, and the two connection segments have two openings. Two connectors are configured to accommodate the flexible sheet and have two pegs.

A tiltable chair includes a flexible seat body including an integrally formed seat back and seat surface supported on a seat frame disposed on upper parts of legs, and the seat back connected to a back frame allowing tilting rearwards, the position of the connection being in an area around the upper part of the pelvis of a person seated thereon. A guide rail having an arc-shaped groove is fixed to the seat frame, and guide members which engage and roll in the arc-shaped grooves are pivotably supported on a shaft bracket of the rear surface of the seat surface. The arc-shaped groove has a high center so that the seat surface undergoes curved motion forward and upward such that the ischium is positioned lower than the lower part of the knees when the seat back tilts rearwards.