Work Principle of Rotary Vacuum Pump
The rotary pump can pump the dry dases from the sealed container. If to add the gas down device, it can also pump definite quatity coagulative gases. But it isn't suitable to pump those gases containing much oxygen and some dust granules, or being corrosive to the metal, or easy rises chemical reaction with the oil.
The rotary pump is one of the basic equipments to obtain the vacuum in the vacuum technology. Most of the rotary pumps are small or middle size. The rotary pumps can be classified to single-stage and double-stages pumps. The so called double-stages pump is designed its structure with two single-stage pumps connecting in series. In generation, the rotary pump is made to double-stages structure in order to obtain the higher vacuum. The relation between the rotary pump speed and the inlet pressure is regulated as bellow:
when the inlet pressure is 1333Pa,1.33Pa or 1.33×10-1（Pa), its' speed data couldn't be lower than the pump's rated speed's 95%, 50%, or 20%.
See the right picture: the work principle sketch
map of the rotary pump. The rotary pump is composed of casing, rotator,
vanes, end shields, and the spring etc.. A rotator is set eccentrically
in the pump's cavity, the rotator out round is tangent with the inner
surface of the cavity (notes: there is a little clearence between them),
and two vanes with spring are set in the rotary groove. When the rotator
rotates, by the centrifugal force and spring tension action, the top of
the vane and the inner wall of the pump cavity keeps touch, and the vanes
are driven by the rotary to glide along the inner wall of the cavity.
The crescent space which shapes by the rotator, cavity and two end shields
is devided into A, B, C three parts by the two vanes. When the rotator
turns along the arrow direction, the space A volume communicating with
the inlet port becomes larger and larger and it is in the inhaling process.
Meantime, the volume of space C becomes smaller and smaller and it is
in the discharge process. And the volume of the mildle space B also becomes
smaller and smaller, and is in the discharge process, too. Because the
volume of the space A becomes larger step by step(i.e.inflation), the
gases pressure decreases, and the outside pressure of the inlet position
is higher than the pressure in space A, thus the gases are pumped in.
When the space A is isotated with the inlet port, i.e. the rotator turns
to the space B, the gases begins to be pressed and the volume of the space
B decrease till it communicates with the discharge port. When the gases
pressure exceeds the discharge pressure, the gases flow will push the
discharge valve on and discharge out to the atmosphere by passing the
oil box. If the discharge gases passes the gas line to enter the other
pump (i.e.low vacuum pump), then are pumped by the low vacuum pum, finally,
discharges out to the atmosphere. i.e. the double-stages pump is formed.
At the moment, the total compressure rate is shared by the two pumps and
the limited vacuum is improved largely.
Announcement：we don't produce the rotary vacuum pump and the documents above is only referrence.
