EP3112688B1 - Split flow vacuum pump and vacuum system with a split flow vacuum pump - Google Patents

Description

The invention relates to a vacuum pump in the design of a split flow pump.

So-called split-flow vacuum pumps are used in practice to simultaneously evacuate a plurality of chambers, for example a mass spectrometer system. The split-flow vacuum pumps make it possible to dispense with a pump system consisting of several individual pumps and to carry out the evacuation of several chambers with a single pump.
Split-flow vacuum pumps have the advantage that they only have a small space requirement for the vacuum system. The split-flow vacuum pumps are not only used in analytical instruments, but also, for example, in leak detectors whose analysis principle is also based on mass spectrometry.

From the prior art ( DE 43 31 589 A1 ) a turbomolecular pump is known, which has a plurality of suction ports, which is in each case connected to one of the vacuum chambers of a device, for example a mass spectrometer. The suction ports deliver gas to various axially spaced locations of the rotor. Along the rotor axis several so-called rotor-stator packages are arranged, each compressing gas. A high vacuum side stator pack creates a pressure ratio between its inlet and outlet. The inlet is connected to a first vacuum chamber. The outlet is connected to the inlet of the next rotor-stator pack. In addition, this area is connected between two rotor-stator packages with a second vacuum chamber. Due to the pressure ratio generated by the first rotor-stator pack and the poor conductance between the vacuum chambers, the pressure in the two vacuum chambers is different. By a corresponding number of rotor-stator packets more vacuum chambers can be evacuated to different pressures, each suction port is assigned a rotor-stator package. It turns out that compared to the diameter very long rotors are difficult to handle, since the rotors are operated at speeds in the range of some 10,000 revolutions per minute.

Another variant for evacuating a multiple vacuum pump assembly is each vacuum pump to be provided with its own flange. At this then a suitable for the pressure range vacuum pump is connected. This approach is unpopular due to the high cost of the plurality of vacuum pumps. There is also a need for compact devices. However, these can not be realized with a large number of vacuum pumps.

In a variety of applications, multiple vacuum chambers are arranged in series and interconnected by low conductance holes. From one to the other end of the row decreases the pressure prevailing within the vacuum chamber gas pressure. The bores are designed so that a particle beam can pass through them and thus through the row of vacuum chambers. The vacuum chamber with the lowest pressure often contains an analyzer, such as a mass spectrometer.

From practice, split-flow vacuum pumps are known, which have three or four radial inlets and which have at least four pumping stages. Pumping stages are usually turbomolecular pumping stages. These are often combined with other pumping stages, for example Holweckpumpstufen or Gaedepumpstufen.

In applications, it is necessary to provide more and more taps in the split-flow vacuum pumps with high pumping speed. This means that the number of rotor disks must be increased, which in turn leads to manufacturing difficulties, for example, when the rotor disks are stacked on the rotor from one side only.

By forming a variant with respect to the inner diameter of the rotor disks (wave guide diameter), a plurality of disk packages with multiple axial stops on the wave can be realized. This means, however, that many different disks must be present in the assembly of the pumps. This variety of different discs are also expensive to manufacture.

The prior art ( DE 10 2009 035 332 A1 and EP 2 789 889 A1 ) include vacuum pumps having multiple turbomolecular pumping stages. Inlets are provided between the turbomolecular pump stages to evacuate various chambers of a chamber system. In these state-of-the-art vacuum pumps, the inlets are arranged between or in front of the individual pumping stages. These state-of-the-art vacuum pumps can be further improved in terms of their pumping power and their potential applications.

Furthermore, the state of the art ( EP 2 378 129 A2 and EP 1 807 627 B1 ) Vacuum pumps in which also inlets are provided before and between pumping stages, which are designed as Hohlweckpumpstufen or turbomolecular pumping stages. These pumps can be further improved in terms of their applications.

The technical problem underlying the invention is to provide a split-flow vacuum pump in which the number of inlets is increased, without increasing the number of pump stages provided.

This technical problem is solved by a split-flow vacuum pump with the features according to claim 1.

The split-flow vacuum pump according to the invention having at least three radial inlets and at least four pumping stages, wherein at least two pumping stages are designed as turbomolecular pumping stages, is characterized in that the at least three inlets are designed as main inlets, which are arranged in the axial direction between the turbomolecular pumping stages, wherein additionally at least one radial Secondary inlet is provided, which is arranged in the region of at least one turbomolecular pumping stage and that the at least one secondary inlet between two stator disks or between two rotor disks or between a stator and a rotor disk at least one turbomolecular pumping stage is arranged.

The inventive design of the vacuum pump, it is possible to provide at least one secondary inlet in addition to the main inlets. The main inlets are located between the pumping stages as known in the art. A novelty of the invention is to provide at least one further inlet, which is arranged in the region of at least one turbomolecular pumping stage. This means that a so-called tap, that is the inlet is not arranged between the turbomolecular pumping stages, but that the tap leads radially into a disk pack of the at least one turbomolecular pumping stage.

This results in significantly more taps, ie inlets with a single pump on a given axial length. By the invention it is possible to evacuate as many chambers of a multi-chamber system on a short axial length.

The rotor may be formed in one piece or in several pieces.

According to an advantageous embodiment of the invention, the at least one secondary inlet has a central axis and the central axis is arranged between a first and a last slice of the at least one turbomolecular pumping stage.

This means that the secondary inlet leads between the disks of the disk package of the at least one turbomolecular pumping stage. As a result, in addition to the state of the art inlets, which are arranged between the pumping stages, additional inlets created, so that a larger number of vacuum chambers can be evacuated.

According to the invention, it is provided that the at least one secondary inlet is arranged between two stator disks or between two rotor disks or between a stator disk and a rotor disk of at least one turbomolecular pumping stage. According to a further advantageous embodiment of the invention it is provided that the secondary inlet is arranged between the disks of a stator, while a main inlet is arranged between the stator.

If several secondary inlets are provided, they can also be arranged radially offset from one another at the same axial height of the rotor. The secondary inlets are arranged in this case in a disk package between two rotor disks and distributed radially on the circumference. However, they can also be on one level.

According to the invention, the at least one secondary inlet is arranged between two adjacent stator disks or between adjacent rotor disks or between a stator disk and an adjacent rotor disk of at least one turbomolecular pumping stage. This means that the secondary inlets are chosen to be relatively small in diameter and arranged between the discs.

It is advantageously provided that a pumping speed of the at least one secondary inlet is less than the suction capacity of a main inlet.

The secondary inlets serve to increase the number of taps of a multi-chamber system to be evacuated.

Between the individual pumping stages, that is to say between the individual disk packages or other pumping stages, for example Gaede or Holweck pumping stages, there is a relatively large amount of space, so that the main inlets can have a relatively large cross section. The secondary inlets lead between disks of turbomolecular pumping stages and therefore have only a relatively small cross-section.

In accordance with a further advantageous embodiment of the invention, it is provided that n-1 secondary inlets are provided in the case of n disks.

This means that the number of secondary inlets is less than the number of slices. If a disk pack of the turbomolecular pumping stage is formed from two disks, a secondary inlet can be provided between these two disks.

However, it is also possible to provide a plurality of radial secondary inlets in the region of a turbomolecular pumping stage. Likewise, it is also possible to provide one or more secondary inlets at multiple turbomolecular pumping stages in each of these turbomolecular pumping stages. Various turbomolecular pumping stages may be formed with and without secondary inlets.

It is advantageously provided that, in addition to the at least one turbomolecular pumping stage, at least one Holweck pumping stage and / or one Siegbahn pumping stage and / or one Gaedepumpstufe and / or a Seitenkanalpumpstufe and / or a Gewindepumpstufe is provided.

Split-flow pumps usually consist of one or more turbomolecular pumping stages and at least one other of said pumping stages.

By combining different pumping stages, the pressure conditions in the chambers to be evacuated can be adjusted accordingly.

For example, it is possible to provide a main inlet between the pumping stages, for example between two turbomolecular pumping stages, and for example additionally to arrange a Holweck pumping stage. According to the invention, at least one further secondary inlet is additionally arranged in the region of the at least two turbomolecular pumping stages.

According to a further advantageous embodiment of the invention, it is provided that a turbomolecular pump stage is formed from one or more rotor disks and / or from one or more stator disks.

A pumping stage usually consists of at least one stator disk and at least one rotor disk. Often, a plurality of stator disks and a plurality of rotor disks, which engage alternately, are provided. According to the invention, it is advantageously provided that n-1 secondary inlets are provided for n disks. For example, if a stator disk and a rotor disk are provided which form a turbomolecular pump stage, the inlet is arranged between these disks.

A further advantageous embodiment of the invention provides that a stator disk and an adjacent rotor disk of a turbomolecular pumping stage define an axial length L, and that a distance between two turbomolecular pump stages at least as long as this length L.

As a result, it is defined that at least one stator disk and / or one rotor disk form at least one turbomolecular pumping stage. If the distance between adjacent stator disks and / or adjacent rotor disks is so great that the length L is exceeded, a new turbomolecular pumping stage commences according to the invention. An inlet in this area between the turbomolecular pumping stages is considered to be the main inlet. An inlet in the area of the turbomolecular pumping stage itself is considered as a secondary inlet.

According to a further embodiment of the invention, it is provided that a turbomolecular pump stage is formed from at least one rotor disk.

The embodiment according to the invention with regard to the inlets can in principle also be used in a turbomolecular pump.

Advantageously, a pumping stage consists of at least one rotor disk and at least one stator disk. In this case, the secondary inlet is arranged between the rotor disk and the stator disk.

According to a further advantageous embodiment of the invention, a vacuum system is provided with at least one vacuum pump and at least one recipient, in which between the vacuum pump and the recipient a detachable Connection is provided, wherein for sealing the connection to the atmosphere side at least one elastomeric seal and in the direction of vacuum side at least one gap seal are provided, which is characterized in that between the elastomeric seal and the gap seal at least one suction channel and / or at least one suction opening is / is provided ,

This embodiment has the advantage that an elastomeric seal is used at the sealing points on the atmosphere side. This is advantageously designed as an O-ring. At least one gap seal is used as the second sealing element between the elastomer seal and the, for example, ultra-high vacuum connection. The surfaces of the recipient (chamber) and a surface of the pump housing are pressed against each other.

Fig. 1

einen Längsschnitt durch eine Anordnung mit einer nicht zur Erfindung gehörenden Vakuumpumpe;

Fig. 2

eine schematische Darstellung eines Rotors mit Scheibenpaketen mit Haupt- und Nebeneinlässen einer nicht zur Erfindung gehörenden Vakuumpumpe;

Fig. 3

eine Splitflow-Vakuumpumpe im Längsschnitt;

Fig. 4

eine Prinzipskizze eines Rotors mit auf dem Rotor angeordneten Rotorscheiben;

Fig. 5

eine Prinzipskizze eines Rotors einer Splitflow-Vakuumpumpe gemäß dem Stand der Technik;

Fig. 6

ein geändertes Ausführungsbeispiel;

Fig. 7

eine Vakuumpumpe in perspektivischer Ansicht mit Vakuumanschluss.

Fig. 8

ein geändertes Ausführungsbeispiel eines Rotors mit zwei Nebeneinlässen;

Fig. 9

ein geändertes Ausführungsbeispiel einer Pumpe mit zwei Nebeneinlässen;

Fig. 10

ein geändertes Ausführungsbeispiel mit Rotorscheiben mit Bund.

Further features and advantages of the invention will become apparent from the accompanying drawings, in which several embodiments of a vacuum pump according to the invention are shown by way of example only. In the drawing show:

Fig. 1

a longitudinal section through an arrangement with a not belonging to the invention vacuum pump;

Fig. 2

a schematic representation of a rotor with disk packages with main and secondary inlets of a not belonging to the invention vacuum pump;

Fig. 3

a split-flow vacuum pump in longitudinal section;

Fig. 4

a schematic diagram of a rotor with arranged on the rotor rotor discs;

Fig. 5

a schematic diagram of a rotor of a split-flow vacuum pump according to the prior art;

Fig. 6

a modified embodiment;

Fig. 7

a vacuum pump in perspective view with vacuum connection.

Fig. 8

a modified embodiment of a rotor with two secondary inlets;

Fig. 9

a modified embodiment of a pump with two secondary inlets;

Fig. 10

a modified embodiment with rotor discs with collar.

Fig. 1 shows a vacuum pump 1, which is designed as a so-called split-flow vacuum pump. The vacuum pump 1 is connected to a multi-chamber vacuum system 2. The multi-vacuum system 2 has four chambers 3, 4, 5, 6, which are to be evacuated by the vacuum pump 1. The gas pressure in the chambers 3, 4, 5, 6 is increasing in this order. The chambers 3, 4, 5, 6 are separated by partitions 7, 8, 9, wherein holes 9, 10, 11 establish a connection. These bores 9, 10, 11 are arranged and dimensioned, for example, such that a particle beam passes through all the chambers 3, 4, 5, 6 can. In particular, the first partition 7 separates the first chamber 3 and the second chamber 4, while the second partition 8 separates the second chamber 4 from the third chamber 5 and the third partition 9 separates the third chamber 5 from the fourth chamber 6. The dashed arrows in the Fig. 1 illustrate the gas flow.

The vacuum pump 1 has a shaft 13 which carries rotor disks 14 to 19. The rotor disks 14 to 19 are in engagement with stator disks 20. The rotor disks 14, 15, 16 form a first disk package 21 and the rotor disks 17 to 19 form a second disk package 22. The disk package 22 forms a high-vacuum-side rotor stator package with the stators 20. The disk package 21 forms with the stator 20 a Zwischenvakuumseitiges rotor stator. The blades in both packages are, as known in the art, both stator and rotor side attached to support rings or integrally formed with this. A first gas inlet 23 is located in front of the high-vacuum-side rotor stator packet, and a second gas inlet 24 is located in front of the forward-vacuum-side rotor stator packet.

From the multichamber vacuum system, a first main inlet 23 leads into the vacuum pump 1. From the second chamber 4, a second main inlet 24 leads into the vacuum pump 1. From the vacuum chamber 5, a further main inlet 25 leads into the vacuum pump 1 and from the vacuum chamber 6, a further main inlet 26 in the vacuum pump. 1

The main inlets 23, 24, 25, 26 are arranged between the turbomolecular pumping stages 21, 22.

In the area of the turbomolecular pump stage 22, a first secondary inlet 27 is arranged, which is separated from the vacuum chamber 5 leads into the vacuum pump 1. In addition, a further secondary inlet 28 leads from the vacuum chamber 6 in the region of the turbomolecular pumping stage 21 into the vacuum pump 1.

Thus, the number of inlets through the secondary inlets 27, 28 is increased. The secondary inlets 27, 28 are arranged in the region of the turbomolecular pumping stages 21, 22.

The rotor shaft 13 has areas with different diameters.

A first region 29 is a region with the largest diameter. On both sides of the shaft 13, two areas 30, 31 with smaller diameters join. This is in turn followed by regions 32, 33 with an even smaller diameter of the shaft 13. In the region 29 of the largest diameter of the shaft 13, no rotor disks are arranged. In the area 30, the rotor disk 16 is arranged, which is determined by a stop 34, which formed by the step-shaped shoulder between the region 29 and the region 30, locally unique.

The same applies to the rotor disk 15, which is determined by a stop 35 between the areas 30, 32.

This also applies to the rotor disk 17 which is fixed by a stop 36 on the shaft 13 and the rotor disk 18 which is fixed by a stop 37 on the shaft 13. Between the rotor disks 14, 15 and the rotor disks 18, 19, a spacer sleeve 38 is arranged in each case. By means of the stops 34 to 37, the rotor disks 14 to 19 are exactly placed on the shaft 13, so that narrow gaps can be formed between the rotor disks 14 to 19 and the stator disks 20.

Another advantage of the invention is that the rotor disks 14 to 19 are placed exactly on the shaft, whereby very small gaps can be formed. This increases the pumping power of the vacuum pump 1. By using many identical parts, the pump is inexpensive to manufacture. In the present embodiment, in each case two rotor disk packs each having the same inner diameter are arranged on the two sides of the region 29 of the shaft 13 with the largest diameter.

A further advantageous embodiment of the invention is an embodiment in which in the region of the largest diameter 29 grooves 39, 40 are arranged, which reduce the mass of the shaft. Since the split-flow vacuum pumps have a very long length, the modal behavior of the rotor and in particular of the rotor shaft is critical. For this reason, according to the invention, the mass and thus the weight of the shaft is reduced while maintaining rigidity.

The vacuum pump 1 has a housing 41. In order to reduce thermal transitions between the high-vacuum side and the fore-vacuum side in the housing 41, the housing 41 has a constriction 42. This constriction reduces the thermal conductivity. It is possible to additionally provide a reinforcement, not shown, in the region of the constriction 42. The housing may also be designed to be divided in the region of the constriction 42, and a thermal seal may be arranged between the two parts of the housing.

The shaft 13 is supported by a magnetic bearing 43 on one side. In a holder 43 a only schematically shown abutment 43 b are arranged. On the other side, the camp is not shown. For example, during storage on the side not shown, it may be an oil-lubricated ball bearing.

In Fig. 1 only turbomolecular pumping stages 21, 22 are shown.

It is also possible, in addition to the turbomolecular pumping stages, to provide a Holweck pumping stage and / or a Siegbahn pumping stage and / or a Gaedepump stage and / or a side channel pumping stage and / or a threaded pumping stage.

The rotor disk 15 and the stator disk 20 have an axial length L as viewed in the axial direction. The distance between the turbomolecular pump stages 21, 22 is greater than the length L.

Fig. 2 shows the shaft 13 with rotor disk packages 44, 45, 46 which form turbomolecular pumping stages 44, 45, 46 with stator disk packages (not shown). The gas flow is shown by an arrow 47.

Arrows 48 represent the gas flow which is supplied from two main inlets 24, 25 to the turbomolecular pumping stages 45, 46. The arrows 49 indicate the gas flow which is supplied from two secondary inlets 27, 28 in the region of the turbomolecular pumping stages 44, 45 to the pumping system.

The secondary inlets 27, 28 are arranged in the region of the turbomolecular pumping stages 44, 45, while the main inlets 24, 25 have their supply between the turbomolecular pumping stages 44, 45 and 46.

Fig. 3 shows vacuum pump 1 with the once again clarified, the turbomolecular pumping stages 44, 45, 46, 49 has. The turbomolecular pump stages 44, 45, 46, 49 consist of rotor disks and stator disks, which are arranged intermeshing. In addition, main inlets 23, 24, 25, 26 are provided, which are arranged in front of the pumping stage 44 or between the pumping stages 44, 45, 46, 49.

The shaft 13 is supported by means of a magnetic bearing 43 and a ball bearing 50. The ball bearing 50 is an oil lubricated ball bearing. The shaft 13 is driven by a motor 51.

In the area of the turbomolecular pumping stage 44, a secondary inlet 27 is provided. A secondary inlet 28 is provided in the region of the turbomolecular pumping stage 45, and a secondary inlet 52 is provided in the region of the turbomolecular pumping stage 46.

By this embodiment, the number of inlets from the four main inlets 23, 24, 25, 26 to a total of seven inlets, namely plus the three side inlets 27, 28, 52 increases.

Fig. 4 shows a partial section through the shaft 13. The shaft 13 has the in Fig. 1 shown areas 29 having the largest diameter, the adjoining areas 30, 31 with a smaller diameter and in turn adjoining areas 32, 33 with a further reduced diameter. In the areas 30, 31, the rotor disks 16, 17 are arranged. In the areas 32, 33, the rotor disks 15, 18, 19 are arranged. The rotor disks 15, 18, 19 have the same inner diameter. The rotor disks 16, 17 have the same inner diameter on. This makes it possible to build a low-cost pump by a large number of identical parts.

The difference in diameter between the areas 29, 30 forms the stop 34. Between the areas 29, 31 of the stopper 36 is provided. Between the areas 30, 32 of the stop 35 is arranged and between the areas 31, 33 of the stop 37 is provided.

The mounting direction of the discs 15, 16 is indicated by the arrow A. The mounting direction of the rotor disks 17, 18, 19 is indicated by the arrow B. M denotes a central axis of the shaft 13. The shaft 13 and the rotor disks 15, 16, 17, 18, 19 are constructed rotationally symmetrically about the center axis M.

Fig. 5 shows a shaft 13 with two turbomolecular pumping stages 21, 22, which are arranged in a housing 41 of a split flow pump. The housing 41 has an inlet 24.

This prior art embodiment shows that a customer housing 60 has an inlet 61 formed radially offset from the inlet 24. The axial length of the pump and the customer chamber 60 do not match.

According to Fig. 6 a solution is shown how nevertheless the highest possible conductance can be achieved. For this purpose, the housing 41 has a web 62 in the region of the inlet 24. Due to the design of the web on which the stator disks (not shown) can be attached, one obtains a larger cross section and thus a higher conductance in the region of the inlet 24.

Fig. 7 shows a vacuum pump 1 with vacuum ports 72, 73, 75. The vacuum port 72 has an elastomeric seal 76 and a gap seal 77 on. Between the elastomeric seal 76 and the gap seal 77, a suction channel 78 is arranged, are arranged in the Zwischenabsaugungen 79. In the vacuum port 75, a suction opening 80 is arranged. The Zwischenabsaugungen 79 lead into a feedthrough bore 81, which is guided to the intermediate stage 73. For a seal arrangement of the vacuum connection 75, a connection channel 82 is provided, so that the vacuum connection 75 is also evacuated via the suction opening 80 via the feed-through bore 82.

Fig. 8 shows a rotor 126, which is shown only schematically with rotor disks 14, 15, 16, 17. Between the rotor disks 16, 17, two secondary inlets 27, 28 are arranged. The secondary inlets 27, 28 are radially spaced apart and both lead between the rotor disks 16, 17th

Fig. 9 shows a housing 60 of a vacuum pump with the vacuum ports 72, 73. There are two secondary inlets 27, 28 are provided, which are arranged in a plane.

Fig. 10 shows the rotor shaft 126, on which rotor disks 14, 15 are arranged. Between the rotor disks 14, 15, a stator 20 is schematically arranged. The rotor disks 14, 15 each have a collar 127. The collar 127 replaces the spacer sleeve 38, which in Fig. 1 is shown.

reference numerals

1

vacuum pump

2

Multi-chamber vacuum pump system

3

chamber

4

chamber

5

chamber

6

chamber

7

partitions

8th

partitions

9

partitions

10

drilling

11

drilling

12

drilling

13

wave

14

rotor discs

15

rotor discs

16

rotor discs

17

rotor discs

18

rotor discs

19

rotor discs

20

stator

21

Turbomolecular pumping stage with disc package

22

Turbomolecular pumping stage with disc package

23

main inlet

24

main inlet

25

main inlet

26

main inlet

27

Besides inlet

28

Besides inlet

29

Area of the shaft 13 with the largest diameter

30

Area of the shaft 13 with a smaller diameter

31

Area of the shaft 13 with a smaller diameter

32

Area of the shaft 13 with the smallest diameter

33

Area of the shaft 13 with the smallest diameter

34

attack

35

attack

36

attack

37

attack

38

shell

39

groove

40

groove

41

casing

42

constriction

43

magnetic bearings

43a

holder

43b

thrust bearing

44

Turbomolecular pump stage with rotor disk packages

45

Turbomolecular pump stage with rotor disk packages

46

Turbomolecular pump stage with rotor disk packages

47

Arrow gas flow

48

Arrow gas flow

49

Turbo molecular pump stage

50

ball-bearing

51

engine

52

Besides inlet

53

groove

54

groove

55

drilling

56

intersection

57

groove

58

groove

59

shell

60

casing

61

inlet

62

web

72

vacuum connections

73

vacuum connections

75

vacuum connections

76

elastomer seal

77

gap seals

78

suction

79

Zwischenabsaugungen

80

suction

81

By guide bore

82

connection

126

rotor

127

Federation

A

arrow

B

arrow

L

axial length

M

central axis

Claims (8)

1. A split flow vacuum pump (1) with at least three radial inlets (24, 25, 26) and with at least four pump stages (21, 22, 44, 45, 46), wherein at least two pump stages are formed as turbomolecular pump stages (44, 45, 46),

   - characterised in that the at least three inlets (24, 25, 26) are formed as main inlets, which are arranged in axial direction between the turbomolecular pump stages (44, 45, 46),

   - wherein there is provided in addition at least one radial auxiliary inlet (27, 28, 52), which is arranged in the region of at least one turbomolecular pump stage (44, 45, 46)

   - and in that the at least one auxiliary inlet (27, 28, 52) is arranged between two stator discs (20) or

   - between two rotor discs (14 to 19) or

   - between a stator disc (20) and a rotor disc (14 to 19) of at least one turbomolecular pump stage (1).
2. A split flow vacuum pump according to claim 1, characterised in that the at least one auxiliary inlet (27, 28, 52) has a central axis and in that the central axis is arranged between a first and a last disc (14 to 19; 20) of the at least one turbomolecular pump stage (21, 22, 44, 45, 46).
3. A split flow vacuum pump according to claim 1 or 2, characterised in that at least two auxiliary inputs (124, 125) are arranged radially of offset to each other.
4. A split flow vacuum pump according to claim 1, characterised in that the at least one auxiliary inlet (52) is arranged between two adjacent stator discs (20) and/or between two adjacent rotor discs (14 to 19) and/or between a stator disc (20) and an adjacent rotor disc (14 to 19) of at least one turbomolecular pump stage (1).
5. A split flow vacuum pump according to any one of the preceding claims , characterised in that a suction capacity of the at least one auxiliary inlet (27, 28, 52) is smaller than the suction capacity of a main inlet (23, 24, 25, 26).
6. A split flow vacuum pump according to any one of the preceding claims, characterised in that with n discs (14 to 19, 20) there are provide n-1 auxiliary inlets (27, 28, 52).
7. A split flow vacuum pump according to any one of the preceding claims, characterised in that a stator disc (20) and an adjacent rotor disc (14 to 19) of a turbomolecular pump stage (21, 22, 44, 45, 46) determines an axial length (L), and in that a spacing between two turbomolecular pump stages (21, 22, 44, 45, 46) is at least as large as the length (L).
8. A vacuum system with at least one split flow vacuum pump according to any one of the preceding claims , and at least one container in which between the vacuum pump and the container there is provided a releasable connection, wherein there are provided for sealing the connection with respect to the atmospheric side at least one elastomeric seal (76) and in the direction of the vacuum side at least one gap seal (77), characterised in that between the elastomeric seal (76) and the gap seal (77) at least one suction channel and/or at least one suction opening (80) is/are provided.

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