The Best Tilting Angle 115° of Chair Tilt Mechanisms

Since 2005, we have served many customers who manufacture chairs and provided them with the core chair tilt mechanisms.

They often discuss with us about the comfortable structure of chairs. The most important suggestion we give to them is that the tilting angle of the chair back adjusted by the tilt mechanism should not exceed 115 °. Such a seat setting is the best for the users, and the users still can keep their healthy even they sit on an office chair for a long time.

Multifunction-Tilt-Mechanism-NT002E

Office Chair Multifunction Tilt Mechanism NT002E

  • Applied to gas lift
  • Lever A for seat height adjustment
  • Lever B for locking back tube at any degree
  • Tension knob for adjusting the height of the chair back
  • Initial angle range of seat : 0°
  • Angle range of back : 85°-115°

Why should the tilt of the chair back adjusted by tilt mechanism not exceed 115 degrees?

Let me introduce Shi Zhenyu, a famous chair designer, told us how he designed the comfortable chair.

The design of a good chair must take comfort and health as the primary goal. However, he can’t define the general comfort. So in order to design a best office chair in China, Mr. Shi went to the Xiehe Hospital to ask doctors about the concept of comfort. In this way, he understood the standard of comfort: the spine kept in a natural state will be comfortable.

And we can know from his research that the seat back tilt adjusted by the chair tilt mechanism should be no more than 115 degrees, which is very important for the user’s health.

What does the chair design pursue for?

Through research, it is found that the design of most furniture puts comfort as the first priority, while health is the second one.

Only the design of office chairs and beds must take health as the first appeal, and comfort the second. Because for the office workers, one-third of their time is spent sitting in an office chair. Sitting for a long time is depleted to the health of the human body.

Therefore, the primary task of chair designers is to design ergonomic chairs to ensure human health. Their research on the healthy seat design is also a kind of care and maintenance of human rights.

The same is true for the bed. While for the other kinds of furniture, their application time is not so much, and people can constantly change postures on them to maintain comfort.

What is the natural state of the spine?

The natural state of the spine of every individual is different. How to find a unified standard?

Keeping the lumbar spine and pelvis straight is the natural state of the spine.

The human spine is composed of cervical vertebrae, thoracic vertebrae, lumbar vertebrae, sacrum and coccyx.

When sitting, the lumbar spine transmits the force to the pelvis, and then from the ischium under the hip bone to the seat surface. At this time, the backrest of the office chair forms a linkage relationship with the human lumbar spine and pelvis.

  • When the human body is sitting upright, the pelvis remains in a natural upright state.
  • While the human body is tilted, the pelvis inclines at the same time.

This is the connection relationship between the pelvis and the spine when the human body is active.

When the body is active, the verticality of the pelvis and the spine can make the pressure on the human intervertebral disc and the pressure distribution of each segment of the spine in the best state. It can reduce the probability of lumbar disc herniation due to prolonged sitting, so as to keep healthy.

The-force-of-sitting-upright

Knowing from the video, pictures, and slice studies, it is preliminarily found that in various angles of sitting postures,

  • If the seated person’s torso is tilted back to about 115° between the thighs, the maximum verticality of the pelvis and the spine can be maintained.
  • If the tilting is more than 115°, the human body will lean backward. And it tends to be lying in an unbalanced state, making thelumbar spine stressed suddenly.

The relationship between people and chair activities

After the establishment of the 115° standard, the A-ONE design team led by Mr. Shi Zhenyu further conducted research on the relationship between people and chair activities.

The tilt movement of the human body is the joint movement of the knee bone, femur and scapula with the ankle bone as the fixed point. They depicted the linkage form of the ankle bone, knee bone, femur, and scapula in a ratio of 1:5.

Based on this, they obtained the basic size range and movement mode of the seat surface, seat cushion and backrest adjustment of the human body during tilting activities.

The parameters that should be the design goals of the office chair

The A-ONE team spent over a year on such a picture. This picture is about the synchronized tilting and it is drawn with a 1:5 ratio. It shows the tilting angle of the human body in a sitting state. Besides, it also specifies the parameters that should be the design goals of the office chair:

Human form: adopting the German man-machine standard DIN95%.

*Note:

  • The height of the human body is 187 cm
  • The seat surface is 480 mm from the ground
  • The armrest height is 260 mm from the chair surface
Drawings-of-human-sitting-activities-and-chair-activities-range-and-methods

Study drawings of human sitting activities and chair activities range and methods ( from Decor Magazine)

Design points for DIN5% of people

In order to adapt to DIN5% of people, the following points must be met:

  • The distance between the seat surface and the ground should be no less than 100 mmwith the adjustment of 380-480 mm.
  • The armrest should be no less than 70 mm away from the chair surface with the adjustment amount of 190-260 mm.
  • The backrest has a downward adjustment of more than 70 mm.
  • When the human body is tilted, the chair surface is moved back 55 mm, the chair surface is tilted 6 degrees, the back of the chair is 30 degrees, and the back of the chair is expanded 115 degrees.

Only the spine and pelvis in various sitting positions are consistent, can it be in a comfortable and healthy state.

The-Synchronous-Inclination-Activities

Research on Synchronous Inclination Activities ( from Decor Magazine)

The design and manufacture of our NT series tilt mechanism is based on the principle discovered by Mr. Shi Zhenyu: The angle of about 115° formed by the reclining of the sitting persons torso and his thigh is the maximum value that can maintain the verticality of the pelvis and the spine.

The starting and rear angle of the tilt mechanism should be between 85 degrees and 115 degrees. Then, the spine and the pelvis can be kept perpendicular to the pelvis as much as possible, so that the seater can obtain the greatest comfort.

Chair-core-mechanism

A research drawing of the working principle of the chair core mechanism. ( from Decor Magazine)

Research and development of a movement tilt mechanism with independent intellectual property rights

Please check our chair tilt mechanisms of the NT series:

Our NT series chair tilt mechanisms

Multifunction-Tilt-Mechanism-NT002E
Multifunction Tilt Mechanism NT002E
Multifunction-Tilt-Mechanism-NT002H
Multifunction Tilt Mechanism NT002H
Multifunction-Tilt-Mechanism-NT007G
Multifunction Tilt Mechanism NT007G

In addition, in the above data from the Shi Zhenyu’s research team, we can also know that in order to adapt to DIN5% of the population, the seat back should be have an adjustment of more than 70 mm.

Another highlight of our NT series tilt mechanisms is that the height of the seat back can be adjusted independently. It is anther kind of user-friendly design for seats of different heights.

For the chairs of different styles, we also provide various types of BACK BAR.

Different-types-of-back-bar-1
Different-types-of-back-bar-2

In conclusion

If you are also designing a new office or medical chair, please also consider “115° principle”. Such a chair design is the best for users.

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