The mechanical pump of the vacuum coating machine is also called the backing pump. The mechanical pump is the most widely used low vacuum pump. It uses oil to maintain the sealing effect and continuously changes the volume of the suction cavity in the pump by mechanical methods. The volume of the gas in the pumped container expands continuously to obtain a vacuum. There are many kinds of mechanical pumps, and the commonly used four types are spool valve type, piston reciprocating type, fixed vane type and rotary vane type.

Vacuum coating machine

       The composition of the mechanical pump of the vacuum coating machine. The mechanical pump is often used to remove dry air, but it cannot remove the gas with high oxygen content, explosive and corrosive gas, and the mechanical pump is generally used to remove the permanent gas. , but it does not have a good effect on water vapor, so it cannot remove water vapor. The main parts of the rotary vane pump are the stator, rotor, shrapnel, etc. The rotor is inside the stator but has a different mandrel from the stator, like two inscribed circles. It is ensured that the shrapnel is tightly attached to the inner wall of the stator.

       The two shrapnel of the mechanical pump of the vacuum coating machine alternately play two roles. On the one hand, the gas is sucked in from the air inlet, and on the other hand, the gas that has been sucked in is compressed and the gas is discharged out of the pump. The pump completes two suctions and two discharges for each rotation of the rotor. When the pump continuously rotates clockwise, the rotary vane pump continuously inhales gas through the air inlet, and continuously discharges it from the exhaust port to achieve the purpose of pumping the container. In order to improve the ultimate vacuum degree of the pump, the stator of the pump is immersed in the oil, so that enough oil is always kept in the gaps and harmful spaces everywhere to fill the gaps, so the oil plays a lubricating role on the one hand, and on the other hand. On the one hand, it plays the role of sealing and blocking gaps and harmful spaces, preventing gas molecules from flowing back into the space with low pressure through various channels.

       The mechanical pump of the vacuum coating machine starts to work from the atmosphere. Its main parameters are the ultimate vacuum and the pumping rate, which are the important basis for the design and selection of the mechanical pump. The single-stage pump can pump the container from the atmosphere to the ultimate vacuum of 1.0*10-1PA, and the two-stage mechanical pump can pump the container from the atmosphere to 6.7*10-2PA, or even higher.

The pumping rate refers to the volume of gas that can be discharged per unit time when the rotary vane pump operates at the rated number of revolutions, which can be calculated by the following formula:

Sth=2nVs=2nfsL

fs represents the cross-sectional area of ​​the cavity at the end of inhalation, L represents the length of the cavity, the coefficient represents that the rotor has two exhausting processes per revolution, and Vs represents that when the rotor is in a horizontal position, the inhalation ends, and the volume in the cavity is the largest at this time. , the speed is n.

       The exhaust effect of the mechanical pump of the vacuum coating machine is also related to the speed of the motor and the tightness of the belt. When the belt of the motor is relatively loose and the speed of the motor is very slow, the exhaust effect of the mechanical pump will also become worse, so it is necessary to often Maintenance, inspection, the sealing effect of mechanical pump oil also needs to be inspected frequently. If the oil is too little, the sealing effect will not be achieved, and the pump will leak air. Generally, the oil level is 0.5 cm below the line.