In the 1990s, with the continuous development of chemical and pharmaceutical industry, semiconductor industry and liquid crystal display manufacturing technology, the requirements for clean vacuum environment are higher and higher. The problem of oil return of traditional oil sealed mechanical pump is increasingly acute, and a new type of vacuum pump with stable and reliable operation and complete oil-free pumping cavity is urgently needed. The dry screw vacuum pump is born in compliance. In 1890, Warren company of Massachusetts in the United States invented the first twin-screw pump in the world. Houttuin company of the Netherlands invented the first twin-screw pump in Europe in 1929. The utility model has the advantages of simple and compact structure, stable and reliable operation, direct air discharge, complete oil-free in the air extraction cavity, etc.
The multi head rotor profile originated from screw compressor started earlier, and some manufacturers directly use the rotor profile of screw compressor in vacuum pump. Hitachi has long used 4-6 screw rotor profiles in vacuum pumps. LG's vacuum pumps in Korea also use multiple rotor profiles at present. Because the top of the contact line of two engaged rotors cannot reach the intersection line of the cylinder holes of the male and female rotors, a space curved triangle will be formed between the top of the contact line and the rotor cylinder hole of the shell, that is, the leakage triangle. The gas will From the volume between teeth with higher pressure to the volume between adjacent teeth with lower pressure, due to the existence of this leakage triangle, the limit vacuum degree of the multi head screw vacuum pump is low. In addition, this kind of rotor is difficult to process and requires special machine tools, which is expensive, so it gradually exits the screw vacuum pump market.
In order to meet the market demand, companies began to develop single head equal pitch rotor profile. At present, the single head vacuum pump still occupies a large market.
Variable pitch screw pump is an upgraded product of equal pitch screw pump. Due to no internal compression process, the exhaust temperature of constant pitch screw pump is very high. If the cooling effect is not good, the rotor and casing will be deformed, which will affect the pumping effect. Richler, Kenny and Laibao all developed and put the products on the market on the basis of single head pitch rotor profile. The guide line (helix) of the earliest screw vacuum pump is constant, that is, the equal pitch screw. The medium (mainly gas) is transmitted in the same volume inside the pump body, and compressed at the exhaust port, which belongs to the external compression, with high energy consumption and noise. From the point of view of energy efficiency, the working gas can be compressed internally. Under the condition that the end face profile is unchanged, the internal compression can be realized by changing the lead of the helix, increasing the lead of the suction end, expanding the suction volume, reducing the lead of the exhaust end, reducing the gas backflow leakage, improving the exhaust capacity and reducing the energy consumption.
In the design of the screw rotor, the most important is the design profile, because the rotor profile basically determines the performance of the screw machine. The continuous improvement of screw mechanical properties and the continuous expansion of its market share are closely related to the development of rotor profile.
In the decade of the 21st century, under the leadership of Liu Xuejun, general manager with more than 20 years' experience in pharmaceutical and chemical production, Hebei VIP vacuum has absorbed foreign advanced technology and design concept to innovate in combination with domestic actual situation, developed and produced VP series vertical variable pitch screw vacuum pump, which has been widely received by customers after being put into the market. VEP vacuum will adhere to the working style of continuous improvement and meticulous, provide users with the optimized vacuum system solutions, and achieve the goals of energy saving, emission reduction, environmental protection and efficiency.