Multi-stage rotary vane vacuum pump
By introducing a fluid circulation channel and a check valve into the multi-stage rotary vane vacuum pump, the problem of high power consumption under high inlet pressure is solved, enabling a smaller, lighter, and more economical vacuum pump design.
Patent Information
- Authority / Receiving Office
- CN · China
- Patent Type
- Utility models(China)
- Current Assignee / Owner
- EDWARDS LTD
- Filing Date
- 2024-02-08
- Publication Date
- 2026-06-26
AI Technical Summary
Existing multistage rotary vane vacuum pumps consume a lot of power at high inlet pressures, and the motors are large, heavy, and expensive.
The system employs a fluid circulation channel and valve structure, including a circulation channel between the first and second pumping stages and a check valve, which allows fluid to circulate between the pump stages, reducing power requirements.
High inlet pressure reduces the power requirement of the vacuum pump, thereby reducing the size, weight, and cost of the motor.
Smart Images
Figure CN224413868U_ABST
Abstract
Description
Technical Field
[0001] This invention relates to a multi-stage rotary vane vacuum pump. Background Technology
[0002] Multistage rotary vane vacuum pumps are known. These pumps are typically driven by motors capable of maintaining full speed at all inlet pressures. These motors are often large, heavy, expensive, and have high power consumption. Utility Model Content
[0003] In one aspect, a multi-stage rotary vane vacuum pump is provided, which includes a fluid circulation channel having a valve disposed therein for allowing fluid circulation within the vacuum pump. This fluid circulation channel and valve tend to substantially reduce the power required by the pump, especially at high inlet pressures (such as pressures above 50 mbar).
[0004] In one aspect, a multi-stage rotary vane vacuum pump is provided, comprising: a first pumping stage including a first pump chamber and a first rotor rotatably mounted within the first pump chamber; a second pumping stage including a second pump chamber and a second rotor rotatably mounted within the second pump chamber; a first fluid passage between the first and second pump chambers for allowing fluid to be pumped from the first pump chamber to the second pump chamber; a second fluid passage (which may be different from the first fluid passage) between the first and second pumping stages for allowing fluid to be pumped from the second pumping stage back to the first pumping stage; and a valve disposed within the second fluid passage.
[0005] The second fluid passage can be arranged to allow fluid to be pumped from the second pump chamber back to the first pump chamber.
[0006] The second fluid passage can be a fluid passage between the inlet to the second pump chamber and the inlet to the first pump chamber.
[0007] The valve may include a valve member movable between a closed position and an open position, and a biasing device biasing the valve member toward the closed position.
[0008] The valve component can be configured to move linearly between a closed position and an open position along the direction of travel of the pumped fluid.
[0009] The multistage rotary vane vacuum pump may also include a housing defining a first pump chamber and a second pump chamber, wherein a second fluid passage is formed through the housing.
[0010] The valve may also include a valve seat for valve components, which is formed from the housing.
[0011] The valve can be a check valve.
[0012] The vacuum pump can be an oil-sealed multistage rotary vane vacuum pump.
[0013] The vacuum pump can be a two-stage or multi-stage rotary vane vacuum pump. The first pumping stage can be a high-vacuum stage, and the second pumping stage can be a low-vacuum stage.
[0014] Vacuum pumps can have a capacity of 30m 3 Maximum capacity of / hr or less. The first pumping stage can have 30m³ / hr. 3 / hr or less of the maximum capacity.
[0015] The capacity ratio between the first pumping stage and the second pumping stage can be at least 3:1.
[0016] The valve can open at a pressure between 250 mbar and 350 mbar.
[0017] The multistage rotary vane vacuum pump may also include a pressure relief valve disposed between the outlet of the first pumping stage and the exhaust port of the multistage rotary vane vacuum pump.
[0018] In another aspect, a method for pumping fluid in a multistage rotary vane vacuum pump is provided. The multistage rotary vane vacuum pump is a multistage rotary vane vacuum pump according to any of the foregoing aspects. The method includes: using one or more rotors to pump fluid from a first pump chamber along a first fluid passage toward a second pump chamber; and opening a valve to allow at least some of the pumped fluid to return from the second pumping stage to the first pump chamber. Attached Figure Description
[0019] Figure 1 This is a schematic side cross-sectional view (not drawn to scale) of an embodiment of a multistage rotary vane vacuum pump.
[0020] Figure 2 This is a schematic diagram of the front cross-section of a multistage rotary vane vacuum pump (not drawn to scale);
[0021] Figure 3 This is a schematic diagram (not drawn to scale) showing the valves of a multistage rotary vane vacuum pump.
[0022] Figure 4 This is a process flow diagram illustrating some steps of a method for pumping fluid using a multistage rotary vane vacuum pump;
[0023] Figure 5 It is a schematic block diagram showing the fluid flow path of the pumped fluid; and
[0024] Figure 6 This is a schematic illustration of a curve (not drawn to scale). Detailed Implementation
[0025] Figure 1 This is a schematic side cross-sectional view (not drawn to scale) of an embodiment of a multistage rotary vane vacuum pump 100.
[0026] Figure 2 This is a schematic diagram of the front cross-section of a multistage rotary vane vacuum pump 100 (not drawn to scale).
[0027] Vacuum pump 100 is a two-stage rotary vane vacuum pump, which includes a housing 102 and has a first stage 104 and a second stage 106. The first stage 104 is a high vacuum stage. The second stage 106 is a low vacuum stage or a pre-vacuum stage.
[0028] Each stage 104, 106 of the vacuum pump 100 includes a corresponding pumping chamber (hereinafter referred to as the first pump chamber 108 and the second pump chamber 110) and a corresponding rotor contained therein (hereinafter referred to as the first rotor 112 and the second rotor 114). More specifically, the first stage 104 includes the first pump chamber 108, and the second stage includes the second pump chamber 110. The first pump chamber 108 and the second pump chamber 110 are defined by the inner surface of the housing 102. The first pump chamber 108 and the second pump chamber 110 are separated by a plate 116.
[0029] In this embodiment, the capacity ratio between the first pumping stage and the second pumping stage is at least 3:1. That is, the ratio between the corresponding capacities of the first pump chamber 108 and the second pump chamber 110 is at least 3:1. More preferably, this ratio is at least 4:1 or at least 5:1.
[0030] In this embodiment, the first stage 104 of the vacuum pump 100 has a capacity of 30m. 3 / hr or less maximum capacity. Therefore, in embodiments where the capacity ratio between the first and second pumping stages is at least 3:1, the second stage 106 of the vacuum pump 100 has a capacity of 10m³ / hr or less. 3 / hr or less of the maximum capacity.
[0031] The vacuum pump 100 also includes a shaft 118 extending longitudinally through the housing 102. The shaft 118 is supported by a bearing 120 connected between the housing 102 and the shaft 118. A first rotor 112 and a second rotor 114 are fixedly attached (e.g., keyed) to the shaft 118 such that rotation of the shaft 118 causes the rotors 112, 114 to rotate within their respective pump chambers 108, 110.
[0032] Shaft 118 and rotors 112, 114 are eccentrically mounted for rotation within housing 102. Each of housing 102 and rotors 112, 114 defines a corresponding crescent-shaped working space within a respective pump chamber. Each rotor 112, 114 includes a corresponding plurality of blades, which are slidably received in radial slots of rotor 112, 114 and contact housing 102 during use, thereby dividing the crescent-shaped working space into multiple compression units. During use, the distal ends of the blades form a sealing contact with the pump chamber surface (i.e., the inner wall of the housing) at all angular positions of the respective rotor.
[0033] For example, refer to Figure 2 The shaft 118 and the first rotor 112 are eccentrically mounted for rotation within the first pump chamber 108. The inner wall of the housing 102 and the first rotor 112 define a first crescent-shaped working space 200 within the first pump chamber 108. The first rotor 112 includes a plurality of blades 202 slidably received in radial slots 204 of the first rotor 112. In this embodiment, the first rotor 112 includes exactly two blades 202. The blades 202 contact the inner wall of the housing 102, thereby dividing the first crescent-shaped working space 200 into a plurality of compression units. In use, the distal ends of the blades 202 are in sealing contact with the surface of the first pump chamber 108 at all angular positions of the first rotor 112.
[0034] In this embodiment, the vacuum pump 100 is an oil-sealed vacuum pump. The peripheral space between the second-stage pump chamber 110 and the wall of the housing 102 defines an oil reservoir 121. The vacuum pump 100 includes one or more oil passages (not shown) between the oil reservoir 121 and the pump chambers 108, 110, thereby allowing oil to flow from the oil reservoir 121 into the pump chambers 108, 110 in a controlled fluid manner. During operation, oil is pumped from the oil reservoir 121 into the pump chambers 108, 110. This oil coats the rotors 112, 114, blades 204, and the inner surfaces of the pump chambers 108, 110 to perform lubrication and sealing functions. For example, the oil often provides an improved seal between the blades 202 and the surface of the first pump chamber 108. Furthermore, a gap may exist between the outer surface of the first rotor 112 and the surface of the first pump chamber 108 at its uppermost portion; this gap can be filled or sealed with oil. In some embodiments, the outer surface of the first rotor 112 may form a sealed contact with the surface of the first pump chamber 108 at the uppermost part of the first pump chamber 108.
[0035] The vacuum pump 100 also includes a fluid inlet passage 122 in fluid communication with the first pump chamber 108. The fluid inlet passage 122 is an inlet to the vacuum pump 100 through which fluid (which is gas in this embodiment) can enter the vacuum pump 100 and flow into the first pump chamber 108.
[0036] The vacuum pump 100 also includes a passage (hereinafter referred to as "first fluid passage" 124) between the first pump chamber 108 and the second pump chamber 110. The first fluid passage 124 is located between the outlet 126 of the first pump chamber 108 and the inlet 128 of the second pump chamber 110. The first fluid passage 124 is a passage through which fluid can be pumped from the first pumping stage 104 to the second pumping stage 106 (e.g., from the first pump chamber 108 to the second pump chamber 110).
[0037] The vacuum pump 100 also includes a fluid outlet passage 130 in fluid communication with the second pump chamber 110. The fluid outlet passage 130 is the outlet of the vacuum pump 100 (e.g., including an exhaust port) through which fluid can leave the vacuum pump 100.
[0038] The vacuum pump 100 also includes a passage (hereinafter referred to as "second fluid passage" 132) between a first pumping stage 104 and a second pumping stage 106. The second fluid passage 132 is fluidly connected to the first pump chamber 108 and the second pump chamber 110. The second fluid passage 132 is different from the first fluid passage 124. The second fluid passage 132 allows fluid to flow from the second pumping stage 106 back to the first pumping stage 104. For example, the second fluid passage 132 may be arranged to allow fluid to be pumped from the second pump chamber 110 back to the first pump chamber 108. In this embodiment, the second fluid passage 132 is a fluid passage between an inlet 128 to the second pump chamber 110 and an inlet 122 to the first pump chamber 108.
[0039] In this embodiment, a second fluid channel 132 is formed through the housing 102.
[0040] Valve 134 is disposed within the second fluid passage 132.
[0041] The second fluid passage 132 can be considered a circulation or recirculation passage, which allows the pumped fluid to circulate or recirculate between stages 104 and 106 of the pump 100. Valve 134 can be considered a circulation or recirculation valve.
[0042] Figure 3 This is a schematic illustration of valve 134 (not drawn to scale). In this embodiment, valve 134 includes a valve member 300 movable between a closed position and an open position. In the closed position, valve member 300 abuts and seals against valve seat 302. Valve seat is formed or defined by housing 102. Figure 3 The valve member 300 is shown in the closed position. In the open position, the valve member 300 is spaced apart from the valve seat 302.
[0043] Valve 134 also includes a biasing device 304. In this embodiment, the biasing device 304 biases the valve member 300 toward the valve seat 302, that is, toward the closed position. In this embodiment, the biasing device 304 is a spring.
[0044] In this embodiment, valve 134 is configured such that valve member 300 can move linearly between a closed position and an open position (e.g., Figure 3 (Indicated by the double arrow and reference numeral 306). The linear movement 306 is substantially aligned with or parallel to the direction of travel of the pumped fluid through the second fluid channel 132.
[0045] In this embodiment, valve 134 is a backflow preventer. Therefore, the backflow of fluid along the second fluid passage 132 (i.e., along the direction from the first pumping stage 104 to the second pumping stage 106) is typically blocked or prevented.
[0046] The opening pressure of valve 134 can be any suitable value, depending on the application. Preferably, the opening pressure of valve 134 is between about 20 mbar and about 500 mbar. More preferably, the opening pressure of valve 134 is between about 100 mbar and about 400 mbar. More preferably, the opening pressure of valve 134 is between about 150 mbar and about 380 mbar. More preferably, the opening pressure of valve 134 is between about 200 mbar and about 370 mbar. More preferably, the opening pressure of valve 134 is between about 250 mbar and about 350 mbar. An opening pressure between about 250 mbar and about 350 mbar tends to provide a good compromise between peak pump speed and peak power.
[0047] Figure 4 This is a process flow diagram illustrating certain steps of a method 400 for pumping fluid using a multistage rotary vane vacuum pump 100.
[0048] Figure 5 It is a schematic block diagram showing the fluid flow path of the pumped fluid.
[0049] It should be noted that Figure 4 Some process steps depicted in the flowchart and described below may be omitted, or such process steps may be performed in accordance with... Figure 4 The different sequences of execution shown and presented below. Furthermore, although all process steps have been depicted as discrete time-sequential steps for convenience and ease of understanding, in reality some process steps may be executed simultaneously, or at least overlap to some extent in time.
[0050] At s402, a motor (not shown) drives shaft 118, thereby rotating rotors 112, 114 in their respective pump chambers 108, 110. The rotation of the first rotor 112 within the first pump chamber 108... Figure 2 The arrows and reference numeral 206 are used to indicate this.
[0051] At s404, as the first rotor 112 rotates in the first pump chamber 108, the volume of the working chamber of the first pump chamber 108 increases along the direction of rotation of the first rotor 112, and air is drawn in from the fluid inlet passage 122. The volume of this working chamber is defined by the first rotor 112, the surface of the first pump chamber 108, and the blades 202. This flow of fluid into the first pump chamber 108... Figure 1 The arrows and reference numerals 450 and 452 indicate this, and... Figure 5The figure is marked with 500.
[0052] At s406, as the first rotor 112 rotates in the first pump chamber 108, the gas in the working chamber of the first pump chamber 108 is compressed and forced out of the outlet 126 of the first pump chamber 108, and enters the first fluid passage 124 towards the second pumping stage 106. This flow of fluid from the first pump chamber 108 to the second pump chamber 110... Figure 5 The arrow and reference numeral 502 are used to indicate this.
[0053] At s408, as the second rotor 114 rotates in the second pump chamber 110, the volume of the working chamber of the second pump chamber 110 increases along the rotation direction of the second rotor 114, and air is drawn in from the inlet 128. The volume of this working chamber is defined by the second rotor 114, the surface of the second pump chamber 110, and the blades of the second rotor 114. This flow of fluid from the inlet 128 to the second pump chamber 110... Figure 1 The arrow and reference numeral 454 are used to indicate this.
[0054] At s410, as the second rotor 114 rotates within the second pump chamber 110, the gas in the working chamber of the second pump chamber 110 is compressed and forced out of the second pump chamber 110 via the fluid outlet passage 130. This flow of fluid exiting the second pump chamber 110... Figure 5 The arrow and reference numeral 504 are used to indicate this.
[0055] At s412, the pressure difference across valve 134 (i.e., the pressure difference between the first pumping stage 104 and the second pumping stage 106) exceeds the opening pressure of valve 134. Therefore, valve 134 opens, meaning that valve component 300 is linearly displaced away from valve seat 302 under the action of fluid flow.
[0056] At s414, due to the pressure difference between the first pumping stage 104 and the second pumping stage 106, at least some fluid travels along the second fluid passage 132, passes through valve 134, and flows from the second pumping stage 106 to the first pumping stage 104. More specifically, in this embodiment, fluid travels from inlet 128 along the second fluid passage 132 into the fluid inlet passage 122, and then returns to the first pump chamber 108. This flow of fluid into the first pump chamber 108... Figure 1 The arrows and reference numerals 456 and 452 indicate this, and... Figure 5 The figure is indicated by reference numeral 506.
[0057] At s416, the pressure difference across valve 134 can be reduced below the opening pressure of valve 134. Therefore, valve 134 is closed, i.e., bias member 304 forces valve member 300 against valve seat 302, thereby sealing the second fluid passage 132 and preventing fluid from flowing through it.
[0058] Therefore, a method 400 for pumping fluid using a multi-stage rotary vane vacuum pump 100 is provided.
[0059] The aforementioned vacuum pumps include an internal circulation or recirculation channel (including a circulation valve or recirculation valve) that allows the pumped fluid to circulate or recirculate between stages of the pump. Advantageously, this circulation channel and valve often provide a reduction in the pump's power requirements, especially at higher inlet pressures.
[0060] Figure 6 This is a schematic illustration of graph 600 (not drawn to scale). Graph 600 plots (i) pump inlet pressure 602 (in mbar) and pump speed 604 (in m). 3 The relationship between (i) pump inlet pressure 602 (in mbar) and pump power consumption / demand 606 (in W) is also included.
[0061] The first plotted line 608 in graph 600 shows the pump speed of a two-stage rotary vacuum pump without a circulation channel and circulation valve. The second plotted line 610 in graph 600 shows the pump speed of a two-stage rotary vacuum pump with a circulation channel and circulation valve, as shown in the reference above. Figures 1 to 3 Pump 100 is described in more detail. As can be seen from graph 600, the circulation channel and circulation valve tend to provide a reduced pump speed, especially at higher inlet pressures (such as pressures above about 90-100 mbar).
[0062] The third plotted line 612 in graph 600 shows the power requirement of a two-stage rotary vacuum pump without a circulation channel and circulation valve. The fourth plotted line 614 in graph 600 shows the power requirement of a two-stage rotary vacuum pump with a circulation channel and circulation valve, as shown in the reference above. Figures 1 to 3 Pump 100 is described in more detail. As can be seen from graph 600, the circulation passage and circulation valve tend to provide reduced power requirements, especially at higher inlet pressures (such as pressures above about 100 mbar).
[0063] Using circulation channels and valves often reduces the peak power requirements of rotary vane pumps. For example, Figure 6 As shown, in the RV12 pump with a stage ratio of approximately 3:1, a peak power reduction of about 105 W has been demonstrated. For higher stage ratios (such as 6:1 or higher), even greater power reductions are often achievable.
[0064] The reduction in peak power often allows for the use of smaller, lower-power motors, resulting in corresponding advantages in size, weight, and cost.
[0065] This valve allows gas to return from the inlet or the outlet of the high vacuum (HV) stage to the inlet of the inlet stage, such as... Figure 1 The proposed valve is located inside the pump cylinder. Figure 2 An embodiment is shown in which the valve is located in the exhaust port or in the low vacuum (LV) stator.
[0066] Advantageously, the valve uses a pump body / housing as the valve housing. The valve can be fitted with a valve pad and / or spring from the gas ballast inlet, thereby reducing manufacturing difficulty and cost.
[0067] The circulation channel and valve are conveniently integrated into the valve body of the recirculation valve for rotary vane pumps.
[0068] Using a direct circulation channel often reduces pump complexity.
[0069] The circulation channels and valves are suitable for a variety of pump capacities and stage ratios.
[0070] Depending on the application, different valve opening pressures can be used.
[0071] In the above embodiment, the vacuum pump is a two-stage rotary vane vacuum pump. However, in other embodiments, the vacuum pump has a different number of pumping stages, for example, more than two stages, such as three or four stages. Corresponding circulation channels and valves can be implemented between any pair of pumping stages (e.g., between each pair of successive pumping stages). In embodiments with multiple circulation channels and valves, the valves can have different opening pressures, depending on the application.
[0072] In the above embodiments, each rotor includes two blades. However, in other embodiments, one or more rotors include a different number of blades, such as more than two blades.
[0073] In the above embodiments, each rotor includes slidably mounted blades. However, in other embodiments, the blades are not slidably mounted to the rotor. For example, flexible blades may be used.
[0074] In the above embodiments, the capacity ratio between the first pumping stage and the second pumping stage is at least 3:1, that is, greater than or equal to 3:1. However, in other embodiments, the capacity ratio is less than 3:1.
[0075] In the above embodiment, the vacuum pump has a capacity of 30m. 3 / hr or less maximum capacity. However, in other embodiments, the vacuum pump has a capacity greater than 30m³ / hr. 3 Maximum capacity per hr.
[0076] In some embodiments, the vacuum pump also includes a pressure relief valve or bypass valve. Such a pressure relief valve may be located between the outlet of the first stage (e.g., outlet 126 or first fluid passage 124) and the pump exhaust port (i.e., the outlet of the last stage of the vacuum pump, which may be the second stage). The pressure relief valve may have any suitable opening pressure, depending on the application. When the pressure difference across the pressure relief valve exceeds its opening pressure, the pressure relief valve allows gas to flow from the outlet of the first stage of the pump to the pump exhaust port, bypassing the second stage and any subsequent pumping stages. Using a pressure relief valve often prevents the generation of interstage pressures above a threshold pressure (such as one atmosphere) in the inlet stage, which would often unnecessarily consume power.
[0077] Figure Labels
[0078] 100-Vacuum Pump
[0079] 102-Shell
[0080] 104 - Level 1
[0081] 106 - Level Two
[0082] 108-First Pump Chamber
[0083] 110-Second Pump Room
[0084] 112-First Rotor
[0085] 114-Second Rotor
[0086] 116-board
[0087] 118-shaft
[0088] 120-bearing
[0089] 121-Oil Storage
[0090] 122-Fluid Inlet Channel
[0091] 124 - First Fluid Channel
[0092] 126 - Outlet of the first pump chamber
[0093] 128 - Inlet of the second pump chamber
[0094] 130-Fluid outlet channel
[0095] 132 - Second Fluid Channel
[0096] 134-valve
[0097] 200 - First Crescent-Shaped Workspace
[0098] 202-blade
[0099] 204-slot
[0100] 206-Direction of Rotation
[0101] 300-Valve Components
[0102] 302-valve seat
[0103] 304 - Bias Device
[0104] 306 - Direction of Movement
[0105] 400-method
[0106] s402–s416 - Method Steps
[0107] 450–456 - Flow direction
[0108] 500–504 - Flow Direction
[0109] 600-line graph
[0110] 602-Inlet Pressure
[0111] 604 - Pump Speed
[0112] 606 - Power Consumption / Demand
[0113] 608 - First Drawing Line
[0114] 610 - Second drawing line
[0115] 612 - Third Drawing Line
[0116] 614 - Fourth Drawing Line
Claims
1. A multi-stage rotary vane vacuum pump, characterized in that, It includes: The first pumping stage includes: First pump chamber; and A first rotor that can be rotatably mounted in the first pump chamber; The second pumping stage includes: Second pump chamber; and A second rotor that can be rotatably mounted in the second pump chamber; A first fluid passage, located between the first pump chamber and the second pump chamber, is used to allow fluid to be pumped from the first pump chamber to the second pump chamber; A second fluid passage, located between the first pumping stage and the second pumping stage, allows fluid to be pumped from the second pumping stage back to the first pumping stage; and A valve installed in the second fluid channel.
2. The multi-stage rotary vane vacuum pump according to claim 1, characterized in that, The second fluid passage is arranged to allow fluid to be pumped from the second pump chamber back to the first pump chamber.
3. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The second fluid passage is the fluid passage between the inlet to the second pump chamber and the inlet to the first pump chamber.
4. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The valve includes: Valve components capable of moving between closed and open positions; and A biasing device that biases the valve component toward the closed position.
5. The multi-stage rotary vane vacuum pump according to claim 4, characterized in that, The valve component is configured to move linearly between the closed position and the open position along the direction of travel of the pumped fluid.
6. The multi-stage rotary vane vacuum pump according to claim 4, characterized in that, It also includes a housing defining the first pump chamber and the second pump chamber, wherein the second fluid passage is formed through the housing.
7. The multi-stage rotary vane vacuum pump according to claim 6, characterized in that, The valve also includes a valve seat for the valve component, the valve seat being formed by the housing.
8. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The valve in question is a check valve.
9. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The vacuum pump is an oil-sealed multistage rotary vane vacuum pump.
10. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that: The vacuum pump is a two-stage multi-stage rotary vane vacuum pump; The first pumping stage is a high vacuum stage; and The second pumping stage is a low-vacuum stage.
11. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The first pumping stage has a 30m 3 / hr or less of the maximum capacity.
12. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The capacity ratio between the first pumping stage and the second pumping stage is at least 3:
1.
13. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, The valve's opening pressure is between 250 mbar and 350 mbar.
14. The multi-stage rotary vane vacuum pump according to claim 1 or 2, characterized in that, It also includes a pressure relief valve disposed between the outlet of the first pumping stage and the exhaust port of the multi-stage rotary vane vacuum pump.