Metal Bellows Assembly Its characteristic is to generate corresponding displacement under the action of pressure, axial force, lateral force or bending moment, pressure resistance, vacuum sealing, corrosion resistance, temperature stability and long service life. Therefore, it has been widely used in many industrial fields. It is mainly used in the following aspects.

　　Elastic sensing element for instruments:

　　High requirements are placed on the elastic characteristics of the bellows as an elastic sensing element. The bellows used as an elastic sensing element basically converts pressure into displacement output or pressure into concentrated force output. The bellows that convert pressure into concentrated force output have almost no deformation or almost no displacement, so the stress generated on the bellows is less than the stress on the bellows with displacement output, and it has no effect on elastic aftereffect and hysteresis. Therefore, the reliability and accuracy of instruments using force balance bellows as elastic sensing elements can be very high. This is why multiple force balance bellows are used as elastic sensing elements in measuring instruments. Bellows that convert pressure into displacement output will generate greater pressure on the bellows. Attention should be paid to the design. At the same time, elastic aftereffect and hysteresis have a certain impact on the elasticity of the bellows.

　　Vacuum sealing of vacuum switches:

　　A vacuum switch is a switching device that switches current on and off in a vacuum. Its main contacts are located in the vacuum circuit breaker. The bellows is a key component of the vacuum arc extinguishing chamber. Only after using the metal bellows assembly is it possible to use mechanical force to move the moving contacts from the outside of the vacuum arc extinguishing chamber and keep the vacuum arc extinguishing chamber shell completely sealed. Each time the vacuum switch is turned on or off, the bellows will have a large displacement. Large amplitude and frequent axial displacement can easily damage the bellows due to fatigue. The bellows is an important part of the vacuum arc extinguishing chamber shell. If damaged, the service life of the vacuum arc extinguishing chamber will be terminated due to air leakage. Other parts of the vacuum arc extinguishing chamber are not easily damaged during normal operation, so the fatigue life of the bellows also determines the mechanical life of the vacuum arc extinguisher. In addition, the contact opening distance of the vacuum switch is equal to the actual axial displacement of the bellows, so the allowable axial displacement of the bellows also determines the large contact opening distance that can be obtained.

　　The fatigue life of the metal bellows assembly is related to its structure and material and the operating conditions. The working stroke of the bellows for vacuum switches has a great influence on its fatigue life. For the same type of bellows and vacuum switch, if you want to obtain a longer fatigue life, you can only reduce the working stroke of the bellows or the contact opening distance. Conversely, if the working stroke or contact opening distance of the bellows increases, the fatigue life of the bellows will be greatly shortened. Therefore, the main performance of the bellows for vacuum switches is axial displacement and vacuum sealing. Vacuum switches have two operating states, open or closed. When open, the bellows needs to stretch and deform. When closed, the bellows needs to compress and deform. In order to ensure the service life of the vacuum switch, the stretching and compression displacement of the bellows must be reasonably designed.

　　Both hydraulically formed bellows and welded bellows can meet the operating requirements of ordinary vacuum switches. Considering the manufacturing cost, hydraulically formed bellows are used for ordinary vacuum switches. Only vacuum switches that require long service life and large contact stroke can use welded bellows.