The Concept of Vacuum Bellows
The so-called vacuum bellows refers to an axially symmetrical tubular shell, the busbar of which is corrugated and has a certain degree of flexibility, so it is also called a flexible tube or a flexible tube. Due to the characteristics of its geometric shape, the bellows can realize the axial length change of the bellows under the action of pressure, axial force, lateral force and bending moment. The length of the bellows is extended under the action of tensile force; the length of the bellows is shortened under the action of compression force. The length or bendable amount of the bellows is determined by factors such as the value and direction of the force, and the performance parameters of the bellows. The difference between it and the smooth tube (plate tube) is that in addition to a certain strength and rigidity, it also has greater flexibility and high fatigue resistance. These properties make the bellows have a very wide range of applications.
Basic types of vacuum bellows
Vacuum bellows can be divided into spiral bellows and ring bellows according to the shape of the wave: a spiral bellows is a tubular shell with corrugations arranged in a spiral shape, and there is a spiral between the corrugations and the corrugations. When the angle is raised, all the corrugations can be connected by a spiral line; the ring-shaped corrugated pipe is a tube-shaped shell with the corrugation in a closed circular ring shape. Ring bellows can be divided into u-shaped, c-shaped, s-shaped, v-shaped and Q-shaped corrugated pipes due to the nature of the waveform. In order to improve the intercepting capacity, multi-layer (mostly double and three layers) corrugated pipes and corrugated pipes with stiffeners in the middle have been continuously developed.
Corrugated pipes can be divided into metallic corrugated pipes and non-metallic corrugated pipes according to their materials. Metal bellows include metal bellows, corrugated expansion joints, and metal corrugated hoses. The metal corrugated pipe is mainly used as a component of the corrugated pipe elastic component. According to the processing technology, it can be divided into hydraulic forming bellows, welding forming bellows, electrodeposition bellows, nuclear rubber forming bellows, spinning forming bellows, pressing forming bellows and mechanical bulging bellows, etc.
Non-metallic bellows include quartz bellows, rubber bellows, polyester bellows and plastic bellows. Non-metallic corrugated pipe has the advantages of corrosion resistance, heat resistance and aging resistance. Among them, the bellows made of quartz, rubber, polyester and PTFE in the plastic bellows are generally used as a part of the elastic component, which mainly completes different functions such as measurement, connection, compensation, sensing, sealing, and shock absorption. . The plastic corrugated pipe introduced in this chapter refers specifically to a new type of plastic pipe used in piping, transportation, water supply and drainage, installation and other applications.