The bellows introduced in this paper can be used in the ultra-high vacuum systems to achieve bending, telescoping and eccentricity (as follow picture), which requires a reliable sealing performance and service life of the bellows.
Bellows are usually divided into two types of bellows and welded bellows, and the material of bellows used in ultra-high vacuum system is generally stainless steel.
To make a slightly larger caliber shaped bellows, the stainless steel plate is first rolled into a tube and welded at the interface. The cylinder is inserted into the bellows mold, and the forming bellows is completed by hydraulic pressure.
In the ultra-high vacuum systems, the bellows connecting the molecular pump and the mechanical pump uses a formed bellows with NW flanges at both ends.
The advantage of forming bellows is that it is simple to produce and low cost. The shortcoming is the lack of flexibility. The welded bellows are insufficient to make up the forming bellows.
Welded bellows are thin-walled pleated hoses made by alternately welding inner and outer diameters of an annular stainless steel sheet (as follow picture). The welding method is plasma welding. This kind of bellows has great flexibility and is an indispensable component in the connection of ultra-high vacuum systems and various kinds of motion introducers. The natural length of bellows should be reasonably selected, and its service life can reach more than ten thousand times.