1、 Overall structure type of pump

The placement structure of the vacuum pump determines the overall structure of the pump.

Vertical structure of the intake and exhaust port horizontal setting, installation and connection of the pipeline are more convenient. However, the center of gravity of the pump is high, and the stability is poor when working at high speed, so this type of pump is mostly used for small pumps.

The air inlet of horizontal pump is on, and the exhaust port is inferior. Sometimes, in order to facilitate the connection of the vacuum system pipeline device, the exhaust port can be connected from the horizontal direction, that is, the inlet and outlet directions are straight to each other. At this moment, the exhaust port can be opened from the left or right directions. In addition to one end of the exhaust pipe, the other end is blocked or connected with a bypass valve. This kind of pump has low center of gravity and good stability at high speed. General large and medium-sized pumps choose this structure.

The two rotor shafts of the pump are straight with the horizontal plane. The installation space of this structure is simple, the rotor is easy to install, and the pump occupies a small area. But the center of gravity of the pump is high and the gear is not easy to disassemble and assemble, and the smooth structure is also relatively disordered.

2、 Transmission method of pump

The two rotors of the vacuum pump work synchronously through a pair of high precision gears. The automatic shaft is connected with the motor through the coupling. There are mainly two kinds of transmission structure: one is that the motor and gear are placed on the same side of the rotor, as shown in the figure. The driven rotor is driven directly by the gear at the motor end, so that the change and deformation of the automatic rotor shaft is small, and the gap between the two rotors will not be changed due to the large change and deformation of the automatic shaft, so that the gap between the rotors is uniform in the working process.

The biggest defect of this transmission method is:

a. There are three bearings on the automatic shaft, which increases the difficulty of pump processing and installation, and the disassembly and adjustment of gears are not convenient;

b. The center of gravity of the pump inclines to the side of motor and gearbox.

3、 Features

(1) There is a large pumping speed in a wide range of pressure;

(2) The rotor has outstanding geometric symmetry, so it has small oscillation and stable operation. There are gaps between the rotors and between the rotors and the shell, so there is no need to be smooth and the collision loss is small. The driving power can be greatly reduced, and then the higher speed can be achieved;

(3) There is no need to seal and smooth the pump cavity with oil, which can reduce the pollution of oil vapor to the vacuum system;

(4) There is no tightening and exhaust valve in the pump chamber. The structure is simple and compact, and it is insensitive to dust and water vapor in the extracted gas;

(5) The surface of the rotor is a curve cylinder with disorderly shape, which is difficult to process and view.