The reason why the swivel chair can be lifted and lowered is because there is a gas pressure bar in the lifting device. The gas pressure bar is a kind of elastic element which can use the functions of support, buffering, braking, height adjustment and angle adjustment with gas and liquid as working medium. The basic principle is that the inside is filled with high-pressure nitrogen. Since the through hole is provided inside the piston, the gas pressure at both ends of the piston is equal, and the cross-sectional areas on both sides of the piston are different, one end is connected with the piston rod and the other end is not, under the action of gas pressure. The pressure on the side with a small cross-sectional area is generated, that is, the elastic force of the gas pressure bar. When the person sits up to the pressure of the lifting shaft, the lifting shaft is gently lowered, and the speed is uniform, and can be lowered to the lowest point. Without lifting the shaft, the lifting shaft is raised back to the highest point.

The gas spring can be stopped at any position in the stroke by means of the release device, and has a large locking force after stopping (can reach 10000 N or more).