The Comparison of the Office Chair Lift : Mechanical Screw, Hydraulic and Gas

History of office chair lifting rods

The office chair lifting rods are constantly being improved as people’s needs change. And it gradually derives the following three main types of lifting rods. They respectively are:

①Mechanical screw lift

②Hydraulic lift

③Gas lift (cylinder)

Let’s see how smart people improve our office chair step by step in order to work more comfortably and efficiently.

Mechanical Screw Lift

Early computer chairs were mostly with a mechanical screw lift, that is, a solid steel rod with screws that supports the seat.

When people need to adjust the height of the computer chair, they must put down the chair. Then, loosen the screws of the fixing bolts and tighten them after adjustment. 

The advantages of this kind of computer chair are :

  • Simple design
  • Low price
  • Pure threaded mechanical lifting structure
  • Good safety (no explosion)

But it also has disadvantages like the troublesome adjustment method. Re-adjustment is very inconvenient.

Although there have been various improvements later, the adjustment is still not simple and direct, and the adjustment efficiency is low. For office workers who want efficiency, such a computer chair is not a good choice.

Hydraulic Lift

In order to make up for the lack of direct convenient adjustment of the mechanical office chair and the cumbersome adjustment, a hydraulic office chair using the principle of hydraulic transmission appeared subsequently.

The lifting of this chair can be adjusted stepless linear through a hydraulic rod valve.

Its advantages are

  • The adjustment method is simple and direct.
  • The fineness of adjustment is higher than that of the mechanical type.

The disadvantage is that if the hydraulic rod is faulty, the leaked oil droplets are difficult to deal with. Besides, the hydraulic structure makes the chair expensive. 

Therefore, hydraulic lifting chairs are more common in service industries such as beauty salons, medical care, etc.

In the domestic market that is more cost-sensitive, there are few hydraulic work chairs that use hydraulic lifting. In addition, the hydraulic swivel chair requires multiple braking to complete the lifting function. The barber needs to step on the switch multiple times to complete the lifting function, and the adjustment efficiency is still not high.

Gas Lift

Now, it is the gas cylinder (gas spring) used by most computer chairs in the world.

First, let’s learn about what a gas cylinder  is. A gas cylinder is an elastic element that uses gas as a working medium. It can support, buffer, brake, adjust chair height and angle. It consists of a pressure tube, a piston, a piston rod and several connecting parts.

The basic principle is that the inside is filled with high-pressure nitrogen. Because there is a through hole inside the piston, the gas pressure at both ends of the piston is equal.

But the cross-sectional area on both sides of the piston is different. One end is connected with a piston rod and the other end is not.

Under the action of gas pressure, a pressure to the side with a smaller cross-sectional area is generated. That is, the elastic force of the gas spring. The elastic force can be set differently by setting different nitrogen pressure or piston rods of different diameters. (For details, please refer to the structure of chair gas cylinder).

At present, this product has been widely used in medical equipment, automobiles, furniture, textile equipment, processing industries and other fields. According to different characteristics and application fields, gas springs are also called support rods, angle adjusters, pneumatic rods, dampers, etc.

According to the structure and function of gas springs, they mainly include free gas springs, self-locking gas springs, random stop gas springs, traction gas springs, and dampers.

Self locking gas springs, the most used gas lift

Among them, self-locking gas springs (angle adjusters, pneumatic rods) are most used in medical equipment, lifting and rotating seats and other products. This kind of gas spring can stop at any position in the stroke with the help of some release mechanisms. And after stopping, it has a large locking force (which can reach more than 10000N).

The lifting part of the self-locking pneumatic bar lift chair has the following characteristics: When the lift valve switch is pressed, then if a person sits up and puts pressure on the lift shaft, the lift shaft will drop gently. Its speed is uniform and it can be lowered to the lowest point. If no external force is applied to the lifting shaft, then the lifting shaft will rise back to the highest point.

When the valve switch is not pressed (or released in the middle of pressing): the lifting shaft remains at the current position, and neither compression nor stretching can make it move relative to the outer sleeve.

The Comparison of the Lift : Mechanical Screw VS Hydraulic VS Gas

Unlike mechanical springs, gas springs have a nearly linear elastic curve.

Most of the characteristics are the same as the hydraulic type, but the cost is cheaper than that of the hydraulic type.

Besides, the air rod can be raised or lowered only by one brake during adjustment. And that is much more convenient than the hydraulic adjustment.

Compared with the mechanical threaded chair lift and the hydraulic chair lift, the pneumatic rod lift chair has achieved a better balance between performance and economy.

Therefore, most office chairs on the market currently use the pneumatic rod.

Office chair lifting rod -Gas Cylinder

How to choose a safe Gas Cylinder?

In the past, there were some cases of inferior chair lift gas spring explosions. With the needs of work and life, everyone is concerned about the safety of gas springs for chair lifts, office computer chairs, and home office computer chairs. How to choose a safe gas cylinder(gas lift)?

Generally, the load test and impact test resistance of a qualified gas rod is 200-250 kg. And it can be lifted and lowered 300,000 times without damage, which is equivalent to five to eight years of normal use.

The nitrogen concentration of a qualified barometric gas lift is generally above 90%. As for the gas lifts in which the rectal burst event occurred, there should be the following two causes:

First, the material of the pressure chamber container wall is inferior, and the pressure chamber is not tightly sealed

Second, the purity of the nitrogen in the pressure chamber is not enough. If the purity of the nitrogen reaches more than 90%, safety can be guaranteed. On the contrary, if the purity of the nitrogen is not enough, once the chair is raised and lowered frequently, the temperature of the air pressure chamber will rise sharply. What’s more, the pressure will increase, which may cause an explosion. 

In addition to emphasizing the safety of the gas lifts, good office chairs will also have some special designs. Such as installation of a whole piece of steel plate with a thickness of 2-4 mm under the seat surface. That is used to further protect the screw and the accidental explosion of the outer pipe end plug of the gas lift. This greatly increases the safety of the product.

For the seats without steel plate protection, we have checked various reports. So far, there are probably less than 10 reports about the explosion of the gas lift. Taking into account the market share of more than 90% of the gas lift chair, the probability of an explosion is still very low.

Therefore, we should buy the gas lift chairs from the trustworthy and experienced manufacturer.



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