It refers to the axisymmetric tubular shell, whose generatrix is corrugated and has certain bendability, so it is also called flexible pipe or flexible pipe. Because of its geometric characteristics, the bellows can change its axial length under the action of pressure, axial force, transverse force and bending moment. Under the action of tensile force, the length of bellows extends; under the action of compressive force, the length of bellows shortens. The length or bending capacity of the bellows is determined by the value and direction of the force, the performance parameters of the bellows and other factors. It has not only a certain strength and stiffness, but also a large flexibility and high fatigue resistance. These properties make bellows have a very wide range of applications
Vacuum bellows basic types
According to the shape of waves, vacuum bellows can be divided into two categories: spiral bellows and ring bellows: spiral bellows is a pipe shell with spiral arrangement of waves, and there is a helix rising angle between the waves. All waves can be connected by a helix; ring bellows is a pipe shell with closed circular waves, and between the waves It is made of a series of circular ripples. The annular bellows can be divided into U-shaped, C-shaped, S-shaped, V-shaped and q-shaped bellows. In order to improve the capacity of bearing and cutting, the bellows with multi-layer (multi-layer or three-layer) and the bellows with stiffener in the middle are continuously opened.
Bellows can be divided into metal bellows and non-metal bellows according to materials. Metal bellows include metal bellows, corrugated expansion joint, metal corrugated hose and so on. Metal bellows is mainly used as one of the elastic components of bellows. According to the processing technology, it can be divided into hydraulic forming bellows, welding forming bellows, electrodeposition bellows, core rubber forming bellows, spinning forming bellows, pressing forming bellows and mechanical expansion bellows, etc.
Non metallic bellows include quartz bellows, rubber bellows, polyester bellows and plastic bellows. Nonmetallic bellows have the advantages of corrosion resistance, heat resistance and aging resistance. Among them, the bellows made of PTFE in quartz, rubber, polyester and plastic bellows are generally used as a part of the elastic components, mainly for measuring, connecting, compensating, sensing, sealing, shock absorption and other different functions. The plastic corrugated supervisor introduced in this chapter refers to a new type of plastic pipe used for piping, transportation, water supply and drainage, installation and other applications.