An Overview of Office Chair Parts 1
- Board, Armrest and Tilt Mechanism

1 Wood Board of office chair

1.1 The types of seat wood board

The wood boards that are applicated in office chairs mainly include the following two types: conjoined board and split board. These 2 applications are common in office chairs.

(1) The conjoined board are also called one-piece molding board.

(2) The split board means that the seat pan and back are separated. And there are several types of split board: the hyperbolic (two curvatures), single curve (forward curve), radius (900R) and so on.

1.2 The characteristics of the board

Molded plywood: a non-planar plywood formed by molding the glued veneer into a blank according to certain technical requirements.

Composite plywood: a non-planar plywood made of non-wood or veneer materials as a core board, covered with veneer or other sheet materials, and glued and molded.

Curved surface: a surface that is smooth and continuously deviates from the horizontal plane.

Curved wood boards are formed by bonding layers of veneers with glue and then hot pressing under high temperature and high pressure. In the case of the same thickness, the thinner the veneer, the better the strength! Under normal circumstances, curved wood is formed by hot pressing of 1.3mm 9-layer wood. Solid wood is natural wood. While curved wood is relatively non-deformed and more reasonable to use.

At present, the market and customers have higher requirements. They also limit the harmful substances in wood furniture, mainly formaldehyde content (quality of glue), preservatives, heavy metals and combustion performance.

1.3 Inspection key points

① Strength requirements: Wood board strength testing machine, 3 air pressures, 147 kg, and hold for 3 to 5 seconds.

② Thickness requirement: 1.2cm.

③ Deformation, cutting and size. The conjoined panels are partitioned in order to maintain the same angle for the same group of chairs.

2 Armrests of office chair

2.1 Materials of Armrests

In terms of material, the armrests are divided into PP, PU, aluminum alloy, iron parts (electroplating, baking varnish), and wooden armrests (curved wood, solid wood). 

2.2 Features of armrests that are made of different materials

(1) PP armrest: It’s made of hard plastic with impact resistance, pressure> 136kg.

(2) PU armrest: It’s made by cast molding. Its shape is determined by the mold, or extrusion molding, containing iron parts.

(3) Aluminum alloy armrest: It is made of aluminum alloy die-casting and polishing.

(4) Curved wooden armrest: Large loss, many processes, high costs, and easy to be affected by climate. But it’s beautiful and high-end, and popular in the American market.

2.3 Functions of armrests

2.4 Inspection key points

(1) Dimensions (contrast drawings)

(2) Whether the surface is intact.

(3) Whether the functions of each part are normal.

All armrests are divided into two-point type (connecting the seat back) and separate type in terms of application.

There are inspection standards for office chair armrests.

3 Tilt Mechanisms of office chair

3.1 Function of tilt mechanisms

Chair Tilt mechanisms can be divided into TG, STG, KTG, etc. in terms of function.

(1) TG: fixed chassis with basic tilt + pneumatic rod (lift + tilt + single lock)

(2) STG: stepless synchronous tilting mechanism + pneumatic rod (lifting + tilting + five-segment locking, simple STG such as split plate)

(3) KTG: Front tilting mechanism + pneumatic rod (inner hexagon spring steel, lifting + tilting + single lock, with two handles)

3.2 The development of the tilt mechanism and its functions

(1) In the beginning, the prototype of the mechanism was just a fixed chassis, which only had the function of simply supporting the body.

(2) With the exchange and development of technology, the mechanism has developed from the original fixed chassis to a tiltable mechanism (TG).

The TG mechanism is the most basic synchronized tilting, rotating mechanism. It has the basic synchronized tilting function, but the pivoting support point for tilting is in the middle of the seat cushion. Then, the tilting thigh muscles are easily compressed. It’s not an ideal institution.


(3) KTG mechanism is a cantilever tilting mechanism, which is called Knee tilt. The pivotal support point is moved to the knee closest to the human body when tilting, thereby greatly reducing the pressure on the thigh muscles when tilting. However, the seat and back cushions of the chair are tilted synchronously and the angle of the seat back cushion is fixed. Besides, the sitting posture of the human body is relatively fixed, and the human body’s groin cannot be stretched when tilted. In order to solve those problems, a kind of STG organization have been developed.

(4) The STG mechanism is a stepless (usually five-stage) synchronous tilt mechanism, which is called Synchronous tilt. This mechanism can well solve the shortcomings of TG and KTG-type institutions. People sitting on a chair can make various parts of the body stretch well through certain mediation, and solve people’s fatigue when sitting and working.

In terms of tilting results, there are 3 types of tilt mechanisms: back tilt mechanisms, seat tilt mechanisms, and synchro tilt mechanisms

3.3 The differences between KTG and STG Mechanisms

Both of these two mechanisms have the characteristics of synchronous tilting. The only difference is that the STG can be locked in sections and within the tilt angle range at will. It is a stepless or fixed-angle locking. KTG does not have this function.

3.4 The characteristics of synchro tilt mechanism

(1) The synchro tilt mechanism is a highly user-friendly and conceptual function, which breaks through the uncomfortable design of the previous tilting mechanism after the long-time sitting. With a synchro tilt mechanism, the chair seat can be completely adapted to the human body’s tilting action, bringing it to the user synchronized health and comfort.

(2) When the general seat is tilted back, both feet will be tilted up at the same time with the feet hanging in the air. Therefore, the legs will generate downward pressure, which causes the blood circulation of the legs to be unsmooth, and the thigh muscles are tight.

(3) When using a synchro tilt mechanism, the seat and back of the chair work at the same time are at an angle of 1:2:5. So when your chair tilts back, the seat will rise slightly. And you only need to put your feet on it gently, then you can stretch your tired body arbitrarily. Besides, it can also eliminate the phenomenon of clothes being pulled up on the back.

3.5 Parts that are connected to the mechanisms

What is the relationship between STG and KTG and other mechanisms?

STG must be a split body, and the back tilt mechanism is also a split body. KTG does not have to be, but the seat back must be at a fixed angle.

What is the setting of L iron? L iron is the back steel plate. The L iron is set according to the mechanism and the angle of the chair.

The outer tube of the gas cylinder with different lengths and tapers are equipped with different mechanisms.

The difference of the gas cylinder and the mechanism will directly affect the seat height of the chair.

Office Chair Tilt-Mechanisms

3.6 Key points of inspection

Special inspection fixture (function, taper)

Size, surface, sound.


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