Application and principle of modern technology vacuum coating machine pump system
Vacuum coating machine vacuum, must use mechanical pump, mechanical pump is also called fore pump, mechanical pump is the most widely used low vacuum pump oil to maintain the sealing effect and rely on mechanical methods to continuously change the volume of the pump suction cavity, so the gas in the container The volume expands to obtain a vacuum. There are many kinds of mechanical pumps, commonly used four types: spool valve type, reciprocating piston type, fixed plate type and rotary plate type.
Mechanical pumps are often used to remove dry air, but cannot remove excess oxygen, explosive and corrosive gases. Mechanical pumps are generally used to remove permanent gases, but they are not effective for water gas, so water gas cannot be removed. The components that play an important role in the rotor pump process are stator, rotor, shrapnel, etc. The rotor is different from the stator shaft and stator, like two inner rings, the rotor slot is provided with two shrapnel, and a spring in the middle of the two shrapnel ensures that the shrapnel tightly attached to the inner wall of the stator.
Its two shrapnel alternately play two roles, on the one hand, the gas is sucked in, and on the other hand, the compressed gas has been sucked in and the gas is discharged from the pump. Each time the rotor rotates, the pump completes two suctions and two discharges. When the pump continues to rotate 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 suctioning the container. In order to improve the limit of vacuum pump, the pump stator is soaked in oil, and the ubiquitous gap in the harmful space is often kept enough oil to fill this gap, oil lubrication, on the one hand, on the other hand, seals and fills the harmful effect of the empty space, preventing Gas molecules flow back into the low-pressure space through various channels.
The mechanical pump starts to work from the atmosphere, and its main parameters are ultimate vacuum degree and pumping speed, which is an important basis for the design and selection of mechanical pumps. 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 the ultimate vacuum of 6.7* 10-2Pa or higher.
The pumping capacity refers to the amount of gas discharged per unit time when the rotary vane pump runs at the rated speed, which can be calculated by the following formula:
something = 2 national front nvs = 2
f represents the cross-sectional area of the air-time cavity at the suction end, L represents the length of the cavity, and the coefficient represents the exhaust process twice per rotation cycle of the rotor. v indicates the end of inspiration when the rotor is in a horizontal position. The volume of this cavity is , and the velocity is N.
The effect of mechanical pump exhaust is related to the speed of the motor and the loose belt. When the belt of the motor is loose and the motor speed is slow, the exhaust effect of the mechanical pump will become worse, so frequent maintenance, tally, and frequent inspection of the mechanical Pump oil seal, too little oil, can not meet the sealing effect, leakage in the pump, too much oil, blocked oil suction holes, unable to inhale and exhaust, generally the oil level is at 0.5 cm in the pipeline.
Roots pump: There is a pair of synchronous high-speed double-blade shape or mechanical lobe lobe pump, because it works like a Roots blower, which can also be called a root vacuum pump, the pump has a pressure extraction speed of 100-1 mpa, which makes up for the mechanical pump The defect of insufficient exhaust capacity is in this range, the pump in the atmosphere cannot start to work and cannot be directly discharged into the atmosphere, its function is only to increase the pressure difference between the intake port and the exhaust port, and the rest of the mechanical pump needs to be completed. , therefore, it must be used with a mechanical pump as the front of the pump.
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