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　　Roots vacuum pump, also known as mechanical booster pump, is a rotary volume vacuum pump.

　　There are two 8-shaped rotors in Roots vacuum pump which are installed on a pair of axes in parallel, and are driven by a pair of synchronous gears with transmission ratio to rotate at the same speed. The rotors and the rotors, the rotors and the pump housing all keep a certain gap and do not contact with each other, so the friction loss is very small, the friction consumption power is very small, and it can be realized. Now it runs at high speed. The internal structure of Roots vacuum pump refers to Fig. 1-2. The two rotors of the pump are supported in the rolling bearings on the two end caps of the pump housing. By means of a pair of separable synchronous gears, the two rotors always maintain a certain mutual position when rotating at high speed, while the end clearance between the rotor and the end cap is near the fixed end (near the motor side). The special structure guarantees that the pump can only expand to one end of the gear box when it is heated. Four sets of PTFE piston ring sealing devices in the two end caps can prevent lubricating oil from entering the pump chamber on both sides of the tank, and the balanced mechanical seal at the outlet of the shaft can prevent air from leaking into the pump chamber.

　　The cooling mode of the pump is usually air-cooled. If the pump is used in the high pressure range, the pump with water-cooled structure is recommended. The power of the motor is transmitted to the driving shaft through the coupling, and then the driven shaft is driven to rotate by the driving shaft through the synchronous gear. ZJ series Roots vacuum pumps are of horizontal structure. The pumps are directly connected with motors by coupling. But the pump with special requirements can adopt triangular belt drive structure.

　　Roots vacuum pump internal structure diagram:

　　ZJP Roots vacuum pump with bypass valve is a product of ZJ Roots vacuum pump. The principle of pumping is the same as that of ZJ pump. It also uses a pair of 8-shaped rotors to keep a certain gap in the pump shell and rotate in the opposite direction at the same speed to produce the function of suction and exhaust. The difference is that the inlet and outlet of ZJP Roots vacuum pump with bypass valve are connected, and a gravity valve is installed vertically in the passage of the two pumps. Maximum pressure difference for reliable operation. Therefore, this kind of valve is actually an overload automatic protection valve, which is also the greatest advantage of ZJP Roots vacuum pump. In theory, ZJP Roots pump can start pumping at the same time with the front pump at atmospheric pressure. If the volume of the system is large, the bypass valve of ZJP Roots pump will be opened for a long time, and the effective pumping speed of the pump will be small. Therefore, it is not economical to start ZJP Roots pump at atmospheric pressure for large systems. 。 It is suggested that ZJP Roots vacuum pump be started when the front pump reaches a certain pressure. Notice in use: Roots vacuum pump has the advantage of higher pumping rate at lower inlet pressure, but it can not be used alone. There must be a front-stage vacuum pump in series. Roots vacuum pump can start work only when the pressure in the pumped system is pumped to the allowable starting pressure of Roots vacuum pump by the front-stage vacuum pump. Electric contact vacuum gauge is allowed to work at high pressure difference, otherwise the Roots vacuum pump will be overloaded and overheated and damaged. Therefore, the front vacuum pump must be selected reasonably when using Roots True Exhaust Air Pump, and the front vacuum pump must be equipped with necessary protection equipment. Front-stage vacuum pumps are generally oil-sealed mechanical pumps, but if the limit pressure is not high, other forms of crude vacuum pumps can be used as front-stage pumps, especially in the extraction of gas containing a large amount of water vapor, water ring vacuum pumps are selected.