Composite vacuum pump and composite rotor

Abstract

The utility model belongs to the technical field of vacuum pumps, and particularly relates to a composite vacuum pump and a composite rotor. In order to overcome the defects that an existing vacuum pump combining a claw type vacuum pump and a screw rod is not suitable for application occasions with much dust due to the fact that the claw type vacuum pump is located on the air suction side and the screw rod is located on the air exhaust side, the utility model adopts the following technical scheme that the combined type vacuum pump comprises a pump body; the number of the composite rotors is two, and each composite rotor comprises a rotor shaft with the two ends extending out of the pump body, a screw rotor arranged on the rotor shaft and located in the pump body, a claw type rotor and a multi-blade roots rotor; a gear motor assembly; and an oil tank. The screw has the advantages that the screw and the claw type structure are combined, the screw structure is close to the air inlet side, and the claw type structure is close to the air outlet side; and for dust entering the pump or formed in the pump, the claw type structure with the high dust treatment capacity is used for treating the dust, so that the dust treatment capacity is higher.

Description

Technical Field

[0001] The utility model belongs to the technical field of vacuum pumps, and in particular relates to a composite vacuum pump and a composite rotor. Background Art

[0002] Existing vacuum pumps are mostly single type. In order to improve the vacuum degree or speed, different vacuum pumps are usually used in combination. For example, conventional Roots-screw vacuum units are composed of two independent Roots pumps and screw pumps connected in series. The Roots pumps and screw pumps are driven by their own motors, and often need to be powered and controlled by two independent frequency converters.

[0003] In order to solve the problems of complex structure, large space occupied and mismatch of the two pumps in the conventional Roots-screw vacuum unit, some existing solutions combine Roots and screw into one pump. However, vacuum pumps also have other forms such as claw type, but vacuum pumps with claw structure are rare in the prior art. Only a few can be retrieved, such as CN208816331U-compound pumps combining claw pumps and sliding valve pumps, and CN219529311U-Roots single-stage claw compound vacuum pumps.

[0004] Japanese patent application JP2002070776A provides a compound vacuum pump that combines claw and screw, achieving "a compound vacuum pump formed by configuring a claw pump on the suction side and a screw pump on the exhaust side, so that a vacuum pump with a high vacuum degree can be obtained that exhausts directly from the vacuum chamber to the atmosphere". At the same time, since its compound vacuum pump is composed of a pair of claw rotors and a pair of screw rotors, "it can be a compound vacuum pump with a small number of parts and a simple structure". In addition, since the screw pump that works in a relatively high-pressure area is used to further compress the gas compressed by the claw pump, "the required power can also be reduced".

[0005] In many engineering application fields of vacuum pumps, the pumped gas often contains solid dust or impurities that condense into solid particles. These solid dust particles brought into the pump cavity by the gas or generated in the pump cavity will accumulate in the pump cavity of the screw pump or adhere to the screw rotor, causing pollution, friction and jamming of the rotor or pump cavity, affecting the safe operation. In fact, the jamming of the screw rotor due to solid dust is one of the most common failures of screw pumps. The solution of the Japanese patent application places the claw in front of the screw, and the dust discharge is mainly completed by the screw, which is easy to cause the screw pump to fail. In addition, the solution of the Japanese patent application is greatly affected by temperature.

[0006] In addition, the existing compound pumps only combine two structures, and there is no compound pump that combines three structures (the multi-leaf Roots in the last stage used with the claw type, as an auxiliary distributor for the exhaust of the claw mechanism, is not considered to be a real compound). Summary of the invention

[0007] The utility model aims at the existing vacuum pumps that combine claw type and screw, where the claw type is located on the suction side and the screw is located on the exhaust side, and is not suitable for applications with a lot of dust. The utility model provides a composite vacuum pump that combines at least the claw type and the screw. By optimizing the layout of the claw type structure and the screw structure, the vacuum pump can better adapt to applications with a lot of dust. Furthermore, the three structures of the composite claw type, screw and Roots are provided. The utility model also provides a composite rotor.

[0008] To achieve the above purpose, the utility model adopts the following technical solution: a compound vacuum pump, the compound vacuum pump comprising:

[0009] The pump body comprises a pump casing with an air inlet and an air outlet at both ends, and an air inlet side end cover and an air outlet side end cover fixed to both ends of the pump casing;

[0010] There are two composite rotors, including a rotor shaft with both ends extending out of the pump body, a screw rotor, a claw rotor and a multi-leaf Roots rotor arranged on the rotor shaft and located in the pump body, wherein the screw rotor, the claw rotor and the multi-leaf Roots rotor are distributed from upstream to downstream along the airflow direction;

[0011] A reduction motor assembly, arranged at the end where the outlet side end cover is located, driving the rotor shaft;

[0012] The oil tank is arranged at the end where the air intake side end cover is located.

[0013] The composite vacuum pump of the utility model composites a screw and a claw structure, wherein the screw structure is close to the air inlet side and the claw structure is close to the air outlet side; for dust entering into the pump or formed in the pump, the claw structure with a strong dust handling ability is used to complete the dust handling ability; the utility model has a claw rotor, and utilizes the high compression ratio and pumping speed performance of the claw rotor in the range above 0.1 mbar to discharge the gas out of the pump; the utility model has a multi-leaf Roots rotor, and the gas passes through the last stage of the multi-leaf Roots rotor, maintaining a small pressure pulsation and reverse leakage, and is discharged out of the pump after compression; the shape and axial size of the last stage of the multi-leaf Roots can be changed according to different gas types to achieve lower pressure pulsation, reverse leakage, and higher pumping speed; the working range with a large compression ratio can be set in the claw structure, and there is no need to set a high compression ratio and number of stages for the screw structure, thereby reducing the manufacturing difficulty.

[0014] As an improvement, the composite rotor further comprises an air intake Roots rotor located upstream of the screw rotor. The air intake Roots rotor rapidly extracts gas in a range below 0.1 mbar.

[0015] As an improvement, the pump casing includes a screw chamber, a claw chamber and a multi-leaf Roots chamber from upstream to downstream along the direction of air flow movement, and the pump casing includes an upright screw claw partition wall and a claw Roots partition wall, a screw claw airflow channel is formed on the screw claw partition wall, and a claw Roots airflow channel is formed on the claw Roots partition wall.

[0016] As an improvement, the pump casing includes an air intake Roots chamber, a screw chamber, a claw chamber and a multi-leaf Roots chamber from upstream to downstream along the direction of air flow movement, and the pump casing includes an upright Roots screw partition wall, a screw claw partition wall and a claw Roots partition wall, a Roots screw airflow channel is formed on the Roots screw partition wall, a screw claw airflow channel is formed on the screw claw partition wall, and a claw Roots airflow channel is formed on the claw Roots partition wall.

[0017] As an improvement, the claw-type rotor is multi-stage, and the pump housing includes an upright inter-claw partition wall, on which an inter-claw airflow channel is formed.

[0018] As an improvement, the screw claw-type airflow channel and the inter-claw airflow channel are axially staggered: the claw-type Roots airflow channel and the inter-claw airflow channel are axially staggered.

[0019] As an improvement, the pump housing comprises an upper housing and a lower housing, the air inlet is arranged on the upper housing, and the air outlet is arranged on the lower housing.

[0020] As an improvement, a sealing groove is provided on the contact surface of the upper shell or the lower shell, a sealing member is provided in the sealing groove, and the sealing groove includes an axially extending groove, a radially extending groove radially inward from the axially extending groove, and an intermediate annular groove located in the radial middle.

[0021] As an improvement, the composite rotor is an integrally formed structure, or the composite rotor is an assembled structure; the screw rotor is a constant pitch or a variable pitch; and the claw rotor is a single-stage or multi-stage one.

[0022] As an improvement, an overflow valve is provided on the pump housing, an overflow channel is formed on the pump body, and the overflow channel is connected to the air outlet.

[0023] As an improvement, a gas ballast gas inlet is provided on the pump housing, and the gas ballast gas inlet is connected to a gas ballast valve.

[0024] As an improvement, cooling plates are provided on the upper and lower surfaces of the pump casing.

[0025] The composite rotor comprises a rotor shaft, a screw rotor, a claw rotor and a multi-leaf Roots rotor arranged on the rotor shaft, wherein the screw rotor, the claw rotor and the multi-leaf Roots rotor are distributed from upstream to downstream along the airflow moving direction.

[0026] As an improvement of the composite rotor, the composite rotor further includes an intake Roots rotor located upstream of the screw rotor; the composite rotor is an integrally formed structure, or the composite rotor is an assembled structure.

[0027] The beneficial effects of the composite vacuum pump of the utility model are as follows: the screw and the claw structure are compounded, the screw structure is close to the air inlet side, and the claw structure is close to the air outlet side; for dust entering the pump or formed in the pump, the claw structure with strong dust handling ability is used to complete the dust handling ability; it has a claw rotor, and utilizes the high compression ratio and pumping speed performance of the claw rotor in the range above 0.1 mbar to discharge the gas out of the pump; it has a multi-leaf Roots rotor, and the gas passes through the last stage of the multi-leaf Roots rotor, maintaining a small pressure pulsation and reverse leakage, and is discharged out of the pump after compression. The shape and axial size of the last stage of the multi-leaf Roots can be changed according to different gas types to achieve lower pressure pulsation, reverse leakage, and higher pumping speed; the working range with a large compression ratio can be set in the claw structure, and there is no need to set a high compression ratio and number of stages for the screw structure, thereby reducing the manufacturing difficulty.

[0028] The beneficial effects of the composite rotor of the utility model are as follows: when applied to a composite vacuum pump, the screw rotor is close to the air inlet side, and the claw rotor is close to the air outlet side. The dust entering the pump or formed in the pump is handled by the claw structure with strong dust handling capability, so as to better adapt to the occasions with more dust; it has a multi-leaf Roots rotor, and the gas passes through the last stage of the multi-leaf Roots rotor, maintaining smaller pressure pulsation and reverse leakage, and is discharged out of the pump after compression. The shape and axial size of the last stage of the multi-leaf Roots can be changed according to different gas types to achieve lower pressure pulsation, reverse leakage, and higher pumping speed; the working range with a large compression ratio can be set in the claw structure, and there is no need to set a higher compression ratio and number of stages for the screw structure, thereby reducing the manufacturing difficulty. BRIEF DESCRIPTION OF THE DRAWINGS

[0029] Figure 1 and Figure 2 It is a schematic diagram of the structure of the compound vacuum pump of the first embodiment of the utility model at different angles.

[0030] Figure 3 It is a structural exploded view of the compound vacuum pump of the first embodiment of the utility model.

[0031] Figures 4 to 6 sectional views of the composite vacuum pump of the first embodiment of the present utility model at different angles ( Figure 5 and Figure 6 The composite rotor in the middle is not cut away).

[0032] Figure 7 and Figure 8 It is a structural exploded view at different angles of the pump housing of the compound vacuum pump of the first embodiment of the utility model.

[0033] Fig. 9 It is a structural schematic diagram of the composite rotor of the composite vacuum pump of the first embodiment of the utility model.

[0034] Fig.10 It is a cross-sectional view of the compound vacuum pump of the second embodiment of the utility model.

[0035] In the figure, 1, pump body; 11, pump casing; 111, upper shell; 112, lower shell; 113, air inlet; 114, air outlet; 115, sealing groove; 116, gas ballast gas inlet; 12, air inlet side end cover; 13, air outlet side end cover; 14, Roots screw partition wall; 141, Roots screw air flow channel; 15, screw claw partition wall; 151, screw claw air flow channel; 16, inter-claw partition wall; 161, inter-claw air flow channel; 17, claw Roots partition wall; 171, claw Roots air flow channel; 18, overflow channel;

[0036] 2. Compound rotor; 21. Rotor shaft; 22. Inlet Roots rotor; 23. Screw rotor; 24. Claw rotor; 25. Multi-blade Roots rotor;

[0037] 3. Gear motor assembly;

[0038] 4. Fuel tank;

[0039] 5. Seals;

[0040] 6. Cooling plate;

[0041] 7. Overflow valve. DETAILED DESCRIPTION

[0042] The technical solutions of the embodiments of the present invention are explained and described below, but the following embodiments are only preferred embodiments of the present invention, not all. Based on the embodiments in the implementation mode, other embodiments obtained by those skilled in the art without creative work are all within the protection scope of the present invention.

[0043] Embodiment 1

[0044] See also Figures 1 to 9 , a compound vacuum pump according to the first embodiment of the utility model, the compound vacuum pump comprises:

[0045] The pump body 1 comprises a pump housing 11 with an air inlet 113 and an air outlet 114 at both ends, and an air inlet side end cover 12 and an air outlet side end cover 13 fixed to both ends of the pump housing 11;

[0046] The compound rotor 2 has two rotors, including a rotor shaft 21 with both ends extending out of the pump body 1, a screw rotor 23, a claw rotor 24 and a multi-leaf Roots rotor 25 arranged on the rotor shaft 21 and located in the pump body 1, and the screw rotor 23, the claw rotor 24 and the multi-leaf Roots rotor 25 are distributed from upstream to downstream along the airflow movement direction;

[0047] The reduction motor assembly 3 is arranged at the end where the outlet side end cover 13 is located, and drives the rotor shaft 21;

[0048] The oil tank 4 is arranged at the end where the air intake side end cover 12 is located.

[0049] In this embodiment, two composite rotors 2 are arranged horizontally in parallel.

[0050] In this embodiment, the composite rotor 2 further includes an air intake Roots rotor 22 located upstream of the screw rotor 23. The air intake Roots rotor 22 rapidly extracts gas in a range below 0.1 mbar.

[0051] In this embodiment, the pump housing 11 includes an air intake Roots chamber, a screw chamber, a claw chamber and a multi-leaf Roots chamber from upstream to downstream along the direction of air flow movement. The pump housing 11 includes an upright Roots screw partition wall 14, a screw claw partition wall 15 and a claw Roots partition wall 17. A Roots screw airflow channel 141 is formed on the Roots screw partition wall 14, a screw claw airflow channel 151 is formed on the screw claw partition wall 15, and a claw Roots airflow channel 171 is formed on the claw Roots partition wall 17.

[0052] In this embodiment, the claw rotor 24 is multi-stage, and the pump housing 11 includes a vertical inter-claw partition wall 16, and an inter-claw air flow channel 161 is formed on the inter-claw partition wall 16. In this embodiment, the claw rotor 24 has two stages, and the thickness of the downstream claw rotor 24 is smaller than that of the upstream claw rotor 24.

[0053] In this embodiment, the screw claw-type air flow channel 151 and the inter-claw air flow channel 161 are staggered in the axial direction; the claw-type Roots air flow channel 171 and the inter-claw air flow channel 161 are staggered in the axial direction.

[0054] In this embodiment, the pump housing 11 includes an upper housing 111 and a lower housing 112. The upper housing 111 is provided with the air inlet 113, and the lower housing 112 is provided with the air outlet 114. The upper housing 111 and the lower housing 112 are fixedly connected by screws.

[0055] In this embodiment, the end surface of the upper shell 111 in contact with the upper shell 111 is provided with a sealing groove 115, and a sealing member 5 is arranged in the sealing groove 115. The sealing groove 115 includes an axially extending groove, a radially extending groove radially inward from the axially extending groove, and an intermediate annular groove located in the middle of the radial direction. The number of the radially extending grooves and the intermediate annular grooves is consistent and consistent with the number of the Roots screw partition wall 14, the screw claw partition wall 15, the claw partition wall 16, and the claw Roots partition wall 17, which are four in this embodiment. The sealing member 5 includes two end seals 5 located at both ends of the radial direction and an intermediate seal 5 located in the middle of the radial direction. The intermediate seal 5 in the intermediate annular groove is not shown.

[0056] In this embodiment, the composite rotor 2 is an assembled structure to reduce the difficulty of processing. In other embodiments, the composite rotor 2 can also be integrally formed.

[0057] In this embodiment, the screw rotor 23 has a constant pitch or a variable pitch.

[0058] In this embodiment, an overflow valve 7 is disposed on the pump housing 11 , and an overflow channel 18 is formed on the pump body 1 . The overflow channel 18 is communicated with the air outlet 114 .

[0059] In this embodiment, a gas ballast gas inlet 116 is provided on the pump housing 11, and the gas ballast gas inlet 116 is connected to a gas ballast valve. The gas ballast valve is not shown in the figure. A through hole corresponding to the gas ballast gas inlet 116 is provided on the cooling plate 6. The gas ballast gas inlet 116 is a threaded hole, and the through hole on the cooling plate 6 is larger than the gas ballast gas inlet 116.

[0060] In this embodiment, cooling plates 6 are provided on the upper and lower surfaces of the pump housing 11 .

[0061] In this embodiment, the reduction motor assembly 3 includes a motor and a gear box.

[0062] In this embodiment, sealing rings are provided between the pump housing 11 and the air inlet side end cover 12 and the air outlet side end cover 13 .

[0063] The beneficial effects of the composite vacuum pump of the first embodiment of the utility model are as follows: the screw and the claw structure are compounded, the screw structure is close to the air inlet side, and the claw structure is close to the air outlet side; for dust entering the pump or formed in the pump, the claw structure with a stronger dust handling ability is used to complete the dust handling ability; it has a claw rotor 24, and utilizes the high compression ratio and pumping speed performance of the claw rotor 24 in the range above 0.1 mbar to discharge the gas out of the pump; it has a multi-leaf Roots rotor 25, and the gas passes through the last stage of the multi-leaf Roots rotor 25 to maintain a small pressure pulsation and reverse leakage, and is discharged after compression In addition to the pump, the shape and axial size of the last stage of multi-leaf Roots can be changed according to different gas types to achieve lower pressure pulsation, reverse leakage, and higher pumping speed; the working range with large compression ratio can be set in the claw structure, and there is no need to set a higher compression ratio and number of stages for the screw structure, thereby reducing the manufacturing difficulty; the three structures of composite claw, screw and Roots, the intake Roots rotor 22, the screw rotor 23, the claw rotor 24 and the multi-leaf Roots rotor 25 are distributed from upstream to downstream, and the intake Roots rotor 22 is used to quickly extract gas in the range below 0.1 mbar.

[0064] Embodiment 2

[0065] See also Fig.10 , a compound vacuum pump according to the second embodiment of the utility model, the compound vacuum pump comprises:

[0066] The pump body 1 comprises a pump housing 11 with an air inlet 113 and an air outlet 114 at both ends, and an air inlet side end cover 12 and an air outlet side end cover 13 fixed to both ends of the pump housing 11;

[0067] The compound rotor 2 has two rotors, including a rotor shaft 21 with both ends extending out of the pump body 1, a screw rotor 23, a claw rotor 24 and a multi-leaf Roots rotor 25 arranged on the rotor shaft 21 and located in the pump body 1, and the screw rotor 23, the claw rotor 24 and the multi-leaf Roots rotor 25 are distributed from upstream to downstream along the airflow movement direction;

[0068] The reduction motor assembly 3 is arranged at the end where the outlet side end cover 13 is located, and drives the rotor shaft 21;

[0069] The oil tank 4 is arranged at the end where the air intake side end cover 12 is located.

[0070] The difference between the second embodiment and the first embodiment is that the second embodiment does not have an intake Roots rotor 22. For other structures of the second embodiment, see Fig.10 , Fig.10 Structural reference not shown Figures 1 to 9 .

[0071] The beneficial effects of the composite vacuum pump of the second embodiment of the utility model are as follows: the screw and the claw structure are compounded, the screw structure is close to the air inlet side, and the claw structure is close to the air outlet side; for dust entering the pump or formed in the pump, the claw structure with strong dust handling ability is used to complete the dust handling ability; it has a claw rotor 24, and the high compression ratio and pumping speed performance of the claw rotor 24 in the range above 0.1 mbar are utilized to discharge the gas out of the pump; it has a multi-leaf Roots rotor 25, and the gas passes through the last stage of the multi-leaf Roots rotor 25, maintaining a small pressure pulsation and reverse leakage, and is discharged out of the pump after compression. The shape and axial size of the last stage of the multi-leaf Roots can be changed according to different gas types to achieve lower pressure pulsation, reverse leakage, and higher pumping speed; the working range with a large compression ratio can be set in the claw structure, and there is no need to set a high compression ratio and number of stages for the screw structure, thereby reducing the manufacturing difficulty.

[0072] The embodiment of the utility model also provides a composite rotor 2, which includes a rotor shaft 21, a screw rotor 23, a claw rotor 24 and a multi-leaf Roots rotor 25 arranged on the rotor shaft 21, and the screw rotor 23, the claw rotor 24 and the multi-leaf Roots rotor 25 are distributed from upstream to downstream along the direction of airflow movement.

[0073] The embodiment of the utility model also provides a composite rotor 2, which includes a rotor shaft 21, a screw rotor 23, a claw rotor 24 and a multi-leaf Roots rotor 25 arranged on the rotor shaft 21, and the screw rotor 23, the claw rotor 24 and the multi-leaf Roots rotor 25 are distributed from upstream to downstream along the direction of air flow movement. The composite rotor 2 also includes an intake Roots rotor 22 located upstream of the screw rotor 23.

[0074] The above is only a specific implementation of the invention, but the protection scope of the invention is not limited thereto. Those skilled in the art should understand that the invention includes but is not limited to the contents described in the above specific implementation. Any modification that does not deviate from the functional and structural principles of the invention will be included in the scope of the claims.

Claims

1. A compound vacuum pump, characterized in that: The compound vacuum pump comprises: A pump body (1) comprises a pump casing (11) with an air inlet (113) and an air outlet (114) respectively provided at two ends, and an air inlet side end cover (12) and an air outlet side end cover (13) fixed to two ends of the pump casing (11); The composite rotor (2) has two rotors, including a rotor shaft (21) with both ends extending out of the pump body (1), a screw rotor (23) disposed on the rotor shaft (21) and located in the pump body (1), a claw rotor (24) and a multi-leaf Roots rotor (25), wherein the screw rotor (23), the claw rotor (24) and the multi-leaf Roots rotor (25) are distributed from upstream to downstream along the direction of airflow movement; A reduction motor assembly (3), arranged at the end where the outlet side end cover (13) is located, driving the rotor shaft (21); The oil tank (4) is arranged at the end where the air intake side end cover (12) is located.

2. A compound vacuum pump according to claim 1, characterized in that: The composite rotor (2) further comprises an air intake Roots rotor (22) located upstream of the screw rotor (23).

3. A compound vacuum pump according to claim 1, characterized in that: The pump housing (11) comprises a screw cavity, a claw cavity and a multi-leaf Roots cavity from upstream to downstream along the airflow movement direction. The pump housing (11) comprises an upright screw claw partition wall (15) and a claw Roots partition wall (17). A screw claw airflow channel (151) is formed on the screw claw partition wall (15), and a claw Roots airflow channel (171) is formed on the claw Roots partition wall (17).

4. A compound vacuum pump according to claim 2, characterized in that: The pump housing (11) comprises an air intake Roots chamber, a screw chamber, a claw chamber and a multi-leaf Roots chamber from upstream to downstream along the airflow movement direction. The pump housing (11) comprises an upright Roots screw partition wall (14), a screw claw partition wall (15) and a claw Roots partition wall (17). A Roots screw airflow channel (141) is formed on the Roots screw partition wall (14), a screw claw airflow channel (151) is formed on the screw claw partition wall (15), and a claw Roots airflow channel (171) is formed on the claw Roots partition wall (17).

5. A compound vacuum pump according to claim 3 or 4, characterized in that: The claw-type rotor (24) is multi-stage, and the pump housing (11) comprises an upright inter-claw partition wall (16), wherein an inter-claw airflow channel (161) is formed on the inter-claw partition wall (16).

6. A compound vacuum pump according to claim 5, characterized in that: The screw claw-type airflow channel (151) and the inter-claw airflow channel (161) are axially staggered; the claw-type Roots airflow channel (171) and the inter-claw airflow channel (161) are axially staggered.

7. A compound vacuum pump according to claim 1 or 2, characterized in that: The pump housing (11) comprises an upper housing (111) and a lower housing (112); the air inlet (113) is provided on the upper housing (111), and the air outlet (114) is provided on the lower housing (112); A sealing groove (115) is provided on the contact surface of the upper shell (111) or the lower shell (112), a sealing member (5) is provided in the sealing groove (115), and the sealing groove (115) comprises an axially extending groove, a radially extending groove extending radially inward from the axially extending groove, and an intermediate annular groove located in the radial middle.

8. A compound vacuum pump according to claim 1 or 2, characterized in that: The composite rotor (2) is an integrally formed structure, or the composite rotor (2) is an assembled structure; The screw rotor (23) has a constant pitch or a variable pitch; The claw-type rotor (24) is one-stage or multi-stage; The pump housing (11) is provided with an overflow valve (7), the pump body (1) is formed with an overflow channel (18), and the overflow channel (18) is connected to the air outlet (114); A gas ballast gas inlet (116) is provided on the pump housing (11), and the gas ballast gas inlet (116) is connected to a gas ballast valve; Cooling plates (6) are provided on the upper and lower surfaces of the pump casing (11).

9. A composite rotor (2), characterized in that: It comprises a rotor shaft (21), a screw rotor (23), a claw rotor (24) and a multi-leaf Roots rotor (25) arranged on the rotor shaft (21), wherein the screw rotor (23), the claw rotor (24) and the multi-leaf Roots rotor (25) are distributed from upstream to downstream along the direction of airflow movement.

10. The composite rotor (2) according to claim 9, characterized in that: The composite rotor (2) further comprises an air intake Roots rotor (22) located upstream of the screw rotor (23); the composite rotor (2) is an integrally formed structure, or the composite rotor (2) is an assembled structure.

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