EP2401505A2

EP2401505A2 - Multi-inlet vacuum pump

Info

Publication number: EP2401505A2
Application number: EP10711634A
Authority: EP
Inventors: Christian Beyer; Markus Henry; Heinz ENGLÄNDER
Original assignee: Oerlikon Leybold Vacuum GmbH
Current assignee: Leybold GmbH
Priority date: 2009-02-28
Filing date: 2010-02-23
Publication date: 2012-01-04
Anticipated expiration: 2030-02-23
Also published as: JP2012519247A; TW201040394A; US20110311348A1; EP2401505B1; WO2010097384A3; US8926266B2; DE102009011082A1; JP5553847B2; WO2010097384A2

Abstract

The invention relates to a multi-inlet vacuum pump having a first pump device (10) provided with a first rotor element (18) comprising several first rotor disks (20) which are arranged successively in the conveying direction (36), and a second pump device (12) provided with a second rotor element (26) comprising several second rotor disks (28) which are arranged successively in the conveying direction (36). The diameter of the second rotor disks (28) is at least partially greater than the diameter of the first rotor disks (20). The claimed multi-inlet vacuum pump also comprises a main inlet (32) through which a first fluid flow (34) is suctioned by the first pump device (10) and is conveyed in the direction of the second pump device ( 12). Furthermore, said pump comprises an intermediate inlet (38) through which a second fluid flow (40) is suctioned by the second pump device (12) and is conveyed in the direction of a pump outlet. Both fluid flows (34, 40) are joined inside the second pump device (12), in particular between two adjacent rotor disks (28) of the second pump device (12).

Description

Multi-iniet vacuum pump

The invention relates to a multi-inlet vacuum pump.

Multi-inlet vacuum pumps have a plurality of pumping devices in a common housing, which may be, for example, turbomolecular pumps, in conjunction with a Holweck stage. The individual pumping devices are usually carried by a common rotor shaft and driven by a single electric motor. The pump housing has a main inlet through which a first fluid flow is sucked by the first pumping means. The first fluid stream is then conveyed after flowing through the first pumping device from the second pumping device and optionally further pumping devices in the direction of an outlet. Between the first and the second pumping means, an intermediate inlet is provided, through which a second fluid flow is sucked by the second pumping device. Thus, the first and second fluid flows in the direction of the outlet from the second pumping device. Possibly. a second intermediate inlet may be arranged between the second and a third pumping device. A corresponding third fluid flow is also conveyed by the third pumping device in the direction of the outlet, in which case all three fluid streams are then conveyed by the third pumping device.

From EP 0 919 726 a multi-inlet pump is known in which the outside diameter of the rotor disks of the first pump device is smaller, as the outer diameter of the rotor disks of the second pumping device. As a result, a relatively high pumping speed is realized at the intermediate inlet.

The object of the invention is to realize a multi-inlet vacuum pump with improved partial pressure and the possibility of increased pumping speed in the intermediate inlet.

The object is achieved according to the invention by a multi-inlet vacuum pump having the features of claim 1.

The multi-inlet vacuum pump according to the invention has a first pump device, which is in particular a turbomolecular pump. The first pumping device has a first rotor element with a plurality of rotor disks arranged one behind the other in the conveying direction. Furthermore, the multi-inlet vacuum pump has a further pumping device, which is preferably likewise a turbomolecular pump. This has a further rotor element with also several in the conveying direction one behind the other arranged rotor disks. A multi-inlet vacuum pump according to the invention has at least two pumping devices, it also being possible for a plurality of pumping devices to be provided. The multi-inlet vacuum pump has a main inlet, through which a first fluid flow is sucked in by the first pumping device and conveyed in the direction of the further, in particular second pumping device. The intake of a further fluid flow from the further pumping device takes place via an intermediate inlet. Possibly. a plurality of intermediate inlets and a plurality of pumping means are provided, wherein the intermediate inlets are preferably arranged between two adjacent pumping devices. The preferably two fluid streams are conveyed in the direction of a pump outlet.

According to the invention, the fluid flows are not combined directly in the area of the intermediate inlet. The association of two in particular Fluid flows thus occur outside the intermediate inlet but within the vacuum pump. Since the gas mixture sucked in through the main inlet possibly has a different composition than the gas mixture sucked through the intermediate inlet, the association of the fluid streams outside the intermediate inlet according to the invention is advantageous since the ratio of the partial pressures in the intermediate inlet is less affected. Preferably, the unifying of the fluid streams takes place only within the weathered pumping device, in particular between two adjacent rotor disks of the second pumping device. The joining preferably takes place between the first and second rotor disks of the further pumping device.

In the case of a multi-inlet pump with a second or further intermediate inlet, the area between the second and the third or between adjacent pumping devices can of course be designed accordingly. In this case, the second and third fluid streams are combined, for example, outside the corresponding intermediate inlet, preferably within the third pumping device, for example.

The diameter of the further, for example, second rotor disk is preferably at least partially larger than the diameter of the first rotor disks, preferably the diameter of a plurality of, in particular all rotor disks of the further pump device is greater than the diameter of the first rotor disks.

In a first preferred embodiment of the invention, at least the first rotor disk of the further pumping device has a passage opening in the conveying direction, that is to say preferably in the axial direction of the rotor shaft. Through the passage opening, the first fluid flow flows at least partially, preferably completely, into the further, for example, second pumping device. In this case, the passage opening is preferably radially within the first rotor disk carrying the blades arranged further pumping device. The association of the fluid flows thus takes place after the first fluid flow has passed through the passage opening. Since only the first rotor disk of the further pumping device

Having through openings, the association of the Fiuidströme between the two first rotor discs of the other Purnpeinrichtung, Ggf, can also be several rotor discs of the other pumping device

Have through holes, so that the unifying of the fluid flows not only between the first two rotor disks but also between other rotor disks of the other pumping device. If, according to a preferred embodiment of the invention, at least a portion of the rotor disks of the further pumping device has a larger diameter than the rotor disks of the first pumping device, the provision of such through-openings results in that the first fluid stream does not radially outwardly due to the change in the diameter of the rotor disks must be diverted so that directly in the area of the intermediate inlet no association of the two Fiuidströme takes place. Rather, a combination of the two fluid streams, for example, only between the first and second rotor disk of the second pumping device, It is also possible that further rotor disks of the second pumping means have passage openings, so that the unifying of the two fluid streams not only between two rotor disks, but between several rotor disks takes place. In this case, the total cross-sectional area of the passage openings in Förderrächtung decrease, so that always a part of the first fluid flow must unite with the second fluid flow between two adjacent rotor discs and a smaller part of the first fluid flow flows unvereinted and only between the two closest adjacent rotor discs with a club the second fluid flow takes place.

The passage opening in the at least first rotor disk of the further pumping device preferably has a plurality of inlet openings. These are arranged in particular along a circular line This ensures that that the stability of the rotor disks is not impaired by the provision of a plurality of individual openings, which are arranged in particular regularly on a circular line.

To avoid having a bigger Tei! of the first fluid flow does not flow through through-openings, but rather flows radially outward in the direction of the intermediate inlet, in a particularly preferred embodiment a housing wall is provided, in particular between radially adjacent pumping devices. The housing wall is preferably sealingly connected to a housing outer wall of the pump housing and protrudes are close to the passage opening or the Rotorwelie zoom. In particular, the housing wall is formed such that between the housing wall and the rotor shaft, an annular opening is formed, wherein the passage openings in the one or more rotor disks of the further pumping means in the flow direction, are arranged within this annular opening. This avoids a deflection of the first fluid flow between this annular opening and the passage openings. Thus, after leaving the first pumping device, the first fluid flow flows through the through-opening in the housing wall and subsequently through the through-opening of the first or several rotor blades of the further pumping device to then be united with the second fluid flow within the further pumping device.

In a further preferred embodiment, in which it is a further realization of the principle according to the invention that the association of the two fluid streams does not take place within a Zwischeneiniasεes, is between Strömungskana adjacent pumping devices! educated. The at least one Strömungskana! is formed such that an outlet of the first pumping device via the Strömungskana! is connected to a region within the further pumping device. This is preferably done such that the at least one flow channel is at least partially disposed within a rotor shaft which carries the rotor elements. In a preferred embodiment, the rotor shaft to form a flow channel on a particular extending in the longitudinal direction groove. When providing a plurality of Strömungskanäie thus several preferably parallel to each other in the longitudinal direction of the rotor shaft extending grooves are provided. The grooves are in this case preferably arranged symmetrically on the circumference of the rotor shaft. The grooves are preferably introduced into an outer circumferential surface of the rotor shaft, for example by milling. In order to form a flow channel closed in the circumferential direction, in preferred embodiments the grooves are closed by a sleeve and / or an inner side of a rotor element. In this particularly preferred embodiment, the first fluid flow flows after passing through the first pumping device, in particular completely into the preferably a plurality of flow channels. The first fluid stream flows through the flow channels and then exits from the flow channels, preferably within a further, in particular the adjacent pumping device. As a result, the first fluid flow is combined with another fluid flow drawn in through an intermediate inlet not within the intermediate inlet, but within the second pumping device.

In a further embodiment, the rotor shaft is designed as a hollow shaft. After flowing through the first pump device, the first fluid flow preferably flows into the flow channel or the rotor shaft through one or more first transverse bores arranged in the rotor shaft. Preferably, a plurality of first transverse bores are arranged, which are provided distributed radially on the circumference of the hollow shaft. Over at least one, preferably a plurality of second transverse bores, the first fluid stream is preferably introduced from the flow channel or the interior of the hollow rotor shaft into the further pumping device. This is done in a particularly preferred embodiment between two adjacent Rotor disks of the second pumping device, in particular in the conveying direction between the first and second rotor disk. It is also possible to arrange the second transverse bores such that the inflow of the first Fiuidstroms takes place in several areas of the second pumping means, that is, for example, between the first and the second Rotorscheϊbe and also between the second and third rotor disk.

In a development of these flow channels, in particular grooves having embodiment of the invention, a sealing disc is arranged in the outlet region of the first pumping device. This, preferably radially extending sealing disc, ensures that the first fluid flow is mostly directed in particular completely in the direction of the at least one flow channel. The sealing disk can in this case be designed or arranged corresponding to the stator disks which are arranged between adjacent rotor disks. The sealing disk can be held in the housing corresponding to the stator disks via a stator ring or fixedly connected to the housing. The sealing disk protrudes close to the Rotorweüe, so that a narrow sealing gap is formed between the sealing disc and the rotor shaft. When a sealing disk is provided, the inlet of the groove or grooves is preferably arranged in the conveying direction between the last rotor disk of the first pumping device and the sealing disk.

In a further preferred embodiment, instead of providing a sealing disk, at least the last rotor disk of the first pumping device is designed such that a counterflow is generated. The conveying direction of this last rotor disk of the first pumping device is thus opposite to the main conveying direction of the vacuum pump. Through this rotor disk, a part of the further fluid flow sucked in through the intermediate inlet is conveyed counter to the main conveying direction, ie in the direction of the first pumping device. In this further preferred embodiment, the first transverse bores and / or the inlet of the grooves between the two last rotor disks of the first pumping device, that is, between the last counter-flow generating rotor disk, and the last rotor disk of the pumping device, which promotes in the main conveying direction arranged. Due to the generated countercurrent is ensured that the first fluid flow is deflected in the direction of the flow channel, in particular in the direction of the grooves or the first transverse bores. A sealing washer can be dispensed with in this embodiment.

In a preferred embodiment of the invention, a sucked by a Zwischeneiniass fluid flow is divided, in which case a part of this further fluid flow flows in the opposite direction. In this embodiment, not only the last rotor disk of the first pumping device is designed to generate a counterflow, but preferably a plurality of rotor disks generate a counterflow. In this case, not only the generation of a countercurrent but at the same time also a compression of the part of the further fluid flow flowing into the countercurrent takes place through these rotor disks. The countercurrent flowing part of the further fluid flow is combined within the first pumping means with the first fluid flow. The first fluid flow flows together with the part of the further fluid flow conveyed in the opposite direction into flow channels. The flow channels are preferably in turn arranged in the Rotorwelie longitudinal grooves and / or transverse bores, as described above. The first fluid flow then flows together with the part of the further fluid flow through the flow channels in the direction of another pumping device. Within the further pumping device, this fluid flow again emerges from the at least one flow channel, so that a combining of this fluid flow with the second part of the further fluid flow sucked in through the intermediate inlet occurs within the further pumping device.

In further preferred embodiments, the individual embodiments described above are at least partially with each other combined. In particular, the provision of a passage opening in at least the first rotor disk of the further pumping device described with reference to the first embodiment can be combined with the provision of at least one flow channel, so that a part of the first fluid stream flows through the at least one passage opening and a part through the at least one flow channel.

The invention will be explained in more detail below with reference to preferred embodiments with reference to the accompanying drawings.

Show it :

1 is a schematic sectional view of a first embodiment of a part of a Muiti-inlet vacuum pump,

2 shows a schematic sectional view of a second embodiment of a part of a multi-inlet vacuum pump,

3 is a schematic sectional view of a third embodiment of a part of a multi-inlet vacuum pump,

Fig. 4 is a schematic sectional view of a fourth embodiment of a part of a multi-inlet vacuum pump, and

Fig. 5 is a schematic sectional view taken along the line V-V in Fig. 4th

Fig. 1 shows the essential part of the invention Teii a Muiti-Iniet- vacuum pump. This is a first pumping device 10 and a further or second pumping device 12, which are arranged in a common housing 14. In addition, in the housing on the in Fig. 1 right side, a third pumping device, such as a Holweckstufe be provided.

The first pumping device 10 has a rotor element 18 arranged on a rotor shaft 16. The rotor element 18 has in the illustrated embodiment, five radially verSaufende rotor disks 20. The rotor disks 20 have rotor fins for transporting fluid, in particular gas. Between adjacent rotor disks 20 stationary stator disks 22 are arranged. The stator disks 22 are held firmly in the housing 14, for example via rings.

Furthermore, another or second rotor element 26 of the second pump device 12 is supported by the rotor shaft 16, which is mounted in the illustrated exemplary embodiment via two bearings 24. The second rotor element 26 likewise has five rotor disks 28 in the exemplary embodiment shown. Between the rotor disks 28 are in turn stationary if necessary, arranged on stator with the housing 14 stator disks 30 are arranged. The rotor disks 28, in an outer region, shown unshaded in FIG. 1, again have wings for transporting fluid.

The first pumping device 10 sucks the gas through a main aisle 32 in the housing 14. This results in a first fluid flow 34 in the direction of the second pumping device 12, or in the conveying direction 36. The conveying direction 36 corresponds to the main conveying direction of the main aisle 32 in the direction of an outlet downstream of the last pumping device in the conveying direction, that is to say on the right in FIG Side is provided in the housing.

Furthermore, the housing 14 has a Zwischeneiniass 38. The intermediate inlet is disposed in the housing 14 between the first pumping device 10 and the second pumping device 12. Through the intermediate inlet 38, a second fluid flow 40, also in the conveying direction 36 generated. The second fluid flow 40 is conveyed by the second pumping device 12 and a possibly further downstream pumping device in the direction of Purnpenauslasses. In the case of multi-inlet pumps, in particular a high vacuum is present at the main inlet 32 and a somewhat lower vacuum at the intermediate inlet 38. In order to be able to generate the highest possible pumping speed, that is to say a low vacuum, also at the intermediate inlet 38, the radius of the rotor discs 28 of the second pumping device 12 is greater than the radius of the rotor discs 20 of the first pumping device 10 in the illustrated embodiment.

According to the invention, in the embodiment illustrated in FIG. 1, the two fluid streams 34, 40 are joined only within the second pumping device 12. In the exemplary embodiment shown in FIG. 2, this is achieved by the first rotor disk 28 of the second in FIG Pumping device 12 has a passage opening 42. The passage opening 42 preferably has a plurality of individual openings arranged on a circle line concentric with the rotor shaft. By providing the passage opening 42, the first fluid flow 34 first flows through the through-opening 42 into the region between the two left-hand rotor disks 28 of the second pumping device 12. The first between the first and left-hand rotor disks 28 of the second pumping device 12 flows Fluid flow, as shown by the arrow 44 then radially outward, so that a unification of the two fluid streams 34, 40 between the two first Rotorscheϊben 28 of the second pumping device 12 takes place. Since no mixing of the two fluid streams 34, 40 takes place in the region of the intermediate inlet 38, it is possible to achieve favorable partial pressures in the region of the intermediate inlet 38. This is particularly advantageous when 38 different gas mixtures are sucked through the main inlet 32 and the intermediate inlet. The passage opening 42 or the insertion openings of the passage opening 42 are provided within the area in which the wings of the first rotor disk 28 are arranged. In the figure, the area of the wings is unshaded dargesteift.

In order to ensure that the first fluid flow 34 flows as completely as possible through the passage opening 42 and thus prevents the two fluid streams from merging in the region of the intermediate inlet 38, a housing wall 46 is additionally provided in the exemplary embodiment shown. The housing wall 46 is arranged between the two pumping devices 10, 12 and extends radially. The housing wall 46 is fixedly connected to the housing 14 and extends in the direction of the rotor shaft 16. The first fluid flow 34 thus flows after passing through the first pumping device 10 through a kreϊsringförmige openings 50 and then through the through holes 42 of the first rotor disc 28 to between the two first rotor disks 28 of the second pumping device 12 to get into this.

In the second preferred embodiment shown in FIG. 2, identical and similar components are identified by the same reference numerals.

The essential difference between the second embodiment shown in FIG. 2 is that the first rotor disk 28 of the second pumping device 12 has no passage openings 42. Rather, the first fluid flow 34 at the end of the first pumping device is deflected radially inwards (arrow 52). For this purpose, a sealing washer 54 is connected to the housing or the stator rings. This runs similarly to the housing wall 46, in the embodiment shown in FIG. 1 radially inwardly and is sealed off from the rotor shaft 16 by a sealing gap 56. Another special feature of the embodiment shown in FIG. 2 is that the shaft 16 is designed as a hollow shaft, so that the first Fluid flow 34 through Querbohrungeπ 58 flows into the interior 60 of the hollow shaft 16, (arrow 62). Preferably, a plurality of transverse bores 58 are arranged symmetrically on the circumference of the hollow shaft 16 in particular.

Downstream of the first transverse bores 58 in the flow direction 36, second transverse bores 64 are arranged in the hollow shaft. Preferably, a plurality of second transverse bores 64 are in turn arranged symmetrically distributed on the circumference. The position of the second transverse bore 64 is selected such that the fluid flows in the direction of an arrow 67 through the transverse bores 64 in the second pumping means 12, wherein in the illustrated embodiment, the fluid between the first two rotor discs 28 of the second pumping device 12 flows. Thus, in the illustrated embodiment, a Strömungskana! 58, 60, 64, wherein the flow channel connects an outlet of the first pumping device with a region within the second pumping device, wherein in the illustrated embodiment is the area between the two first rotor disks 28 of the second pumping device 12. The second transverse bores 64 may, for example, also end between the second and third, third and fourth, etc. rotor disks 28 of the second pump device 12. It is also possible that a plurality of levels of transverse bores are provided, so that transverse bores end, for example, both between the first and second and between the second and third rotor disk 28.

The second fluid flow 40, as in the embodiment shown in FIG. 1, flows through the intermediate inlet 38 and is conveyed by the second pumping device 12 in the direction of the outlet, not shown, of the multi-inlet vacuum pump. The combining of the two fluid streams 34, 40 takes place, as in the first exemplary embodiment (FIG. 1), for example, between the first two rotor disks 28 of the second pumping device 12. The third embodiment shown in Fig. 3 is similar to the second embodiment shown in Fig. 2, so that identical and similar components are identified by the same reference numerals.

The essential difference between the embodiment illustrated in FIGS. 2 and 3 is that the third embodiment (FIG. 3) has no sealing disk 54. Instead, a last, in Fig. 3 right rotor disk 68 of the first pumping device 10 is formed such that the rotor disk 68 promotes fluid against the Hauptförderrϊchtung 36 of the multi-inlet vacuum pump in the direction of arrow 70. This is realized in that the wings of the rotor blade 68 point in the opposite direction. Due to the conveying direction of the rotor disk 68, the first fluid flow can not pass through the rotor disk 68. As a result, the first fluid flow 34 according to the second embodiment (FIG. 2) is conveyed radially inwards (arrow 52) and flows through the first transverse bores 58 into the interior 60 of the hollow rotor shaft 16. The rotor disk 68, through which a small portion of the second fluid stream 40 is conveyed in the opposite direction to the main conveying direction 36, thus has a good sealing effect. This prevents the two fluid streams 34, 40 from already being combined in the region of the intermediate inlet 38. According to the second embodiment (FIG. 2), the first fluid flow is conveyed through the flow channel 58, 60, 64 within the second pumping device 12. The second transverse bores 64 are in this case arranged in the hollow shaft 16, that the first fluid flow between the two first rotor discs 28 of the second pumping device 12 enters into this.

In the in Figs. 4 and 5 illustrated fourth preferred embodiment, identical and similar components with the same reference numerals.

In the further preferred embodiment of the invention shown in FIG. 4, the fluid flow 40 drawn in through the intermediate part aisle 38 becomes _ IS -

divided immediately after entering the vacuum pump into two fluid streams 70, 71. According to the embodiment shown in Fig. 3, the TeiS fluid stream 70 is conveyed against the main conveying direction 36. This results in the first pumping device 10, a counterflow, this is generated by the blades of the rotor disk 21 and the stator 14 fixedly connected to the housing. In the illustrated embodiment, the rotor disk 21 and the associated stator disk 23 has a larger diameter than the other rotor disks 20 and stator disks 22 of the first pumping device. In particular, the outer diameter of the rotor disk 21 and the stator disk 23 are essentially corresponding to the rotor disks 28, and / or the stator disks 30 of the second or further pump apparatus 12.

Due to the countercurrent that is generated by the partial flow 70, the first fluid flow 34 does not exit the first pumping device in the region of the intermediate inlet 38. Instead, the partial fluid flow 70 and the first fluid flow 34 are combined into a region 72 of the first pumping device 10. The region 72 is a substantially annular region.

The combined fluid flow from the first fluid flow 34 and the partial fluid flow 70 then flows through flow channels formed as grooves 74 in the embodiment illustrated. The grooves 74 may in this case be arranged directly in the shaft 16. In the illustrated Ausführungsbeϊspiel an intermediate element 76 is disposed on the WeNe 16. The intermediate member 76 is fixedly connected to the shaft 16, for example, by shrinking. By providing the intermediate member 76, it is possible to displace the flow channels 74 radially outwardly with respect to the shaft 16. This has the advantage that the flow channels or grooves 74 are arranged such that the first fluid stream 34 without having to be deflected, flows into the grooves 74. To form the flow channels 74, a sleeve 78 is arranged around the intermediate element 76. Instead of a Zwischenelemeπts 76, the rotor shaft 16 may be formed as a stepped shaft.

The circular cylindrical sleeve 78 not only serves to form the flow channels 74, but serves in the illustrated Ausführungsbeispie! in addition to supporting the rotor disk 21, which generates the counterflow 70.

In the illustrated embodiment, a first rotor disk 77 of the second pumping device 12 is not supported by the second rotor element 26 but also by the sleeve 78. This has the advantage that it is ensured in a simple manner that the medium flowing through the grooves 74 only unites with the further fluid flow or the partial fluid flow 71 within the second pumping device. In the illustrated embodiment, the union of the fluid flows between the rotor disk 27 and the adjacent rotor disk 28 takes place, wherein it is rotor disks of the second pumping device 12 in both rotor disks 27, 28.

The flow channels formed as grooves (74) described with reference to the fourth embodiment (FIGS. 4 and 5) can also be provided in the embodiments illustrated in FIGS. 2 and 3. In this case, instead of or in addition to the transverse bores 58, 64, a rotor shaft 16 provided with grooves according to the fourth embodiment (FIGS. 4 and 5) would then be provided.

Claims

claims

1. Multi-Iniet Vacuum Pump, with

a first pumping device (10) having a first rotor element (18), with a plurality of first rotor disks (20, 21) arranged one behind the other in the conveying direction (36),

at least one further pumping device (12) with a further rotor element (26), with a plurality of further rotor disks (27, 28) arranged successively in the conveying direction (36),

a main inlet (32) through which a first Fiutdstrom (34) is sucked by the first pumping means (10) and is conveyed in the direction of the further pumping means (12) and

at least one intermediate inlet (38) through which a second fluid flow (40) is sucked in by the second pumping device (12) and conveyed in the direction of a pump outlet,

d a d u r c h e s e n c i n e s, d a s s

a union of the two fluid streams (34, 40) taking place outside the intermediate inlet (38) takes place within the vacuum pump

2. Multi-inlet vacuum pump according to claim 1, characterized in that the association of the two fluid streams at least mainly within the at least one further pumping device (12) in particular between two adjacent further rotor discs (28; 27, 28) of the further pumping device (12) he follows. _ I ₈ _

3. Muiti-inlet vacuum pump according to claim 1 or 2, characterized in that the diameter of the second rotor discs (27, 28) is at least partially larger than the diameter of the first rotor discs (20).

4. Muiti-inlet vacuum pump according to one of claims 1 to 3, characterized in that in the conveying direction (36) at least the first rotor disc (28) of the further pumping means (12) has a through-opening (42) through which the first fluid flow ( 34) flows into the second pumping device (12).

5. Muiti-inlet vacuum pump according to claim 4, characterized in that the passage opening (42) is arranged radially within the wing carrying the first rotor disc (28) of the second pumping device (12).

6. MuSti Inlet vacuum pump according to one of claims 1 to 5, characterized by a, in particular radially arranged housing wall (46) between the first pumping means (10) and the second pumping means (12), which is preferably tightly connected to a housing outer wall.

7. Multi-inlet vacuum pump according to claim 6, characterized in that a narrow sealing gap (48) is provided between the housing wall (46) and a rotor shaft (16).

8. Multi-inlet vacuum pump according to claim 1, characterized by at least one flow channel (58, 60, 64, 74) which connects the first pumping device (10) with a region within the further pumping device (12). _ ig _

9. Multi-inlet vacuum pump according to claim 8, characterized in that the flow channel (58, 60, 64, 74) is at least partially disposed within a rotor shaft (16) carrying the first rotor element (18) and the second rotor element (26) , which is preferably formed as a hollow shaft.

10. Multi-inlet vacuum pump according to claim 8 or 9, characterized in that the at least one flow channel (58, 60, 64, 74) is formed by at least one longitudinally extending in the rotor shaft groove (74), wherein the at least one Groove (74) is preferably radially closed by a sleeve (78) and / or a Rotoreiement (18).

11. Multi-inlet vacuum pump according to claim 10, characterized in that the rotor shaft (16) has a plurality of in particular symmetrically distributed around the circumference arranged in the longitudinal direction of the rotor shaft extending grooves (74).

12. Multi-inlet vacuum pump according to one of claims 9 to 11, characterized by at least one in the rotor shaft (16) arranged first transverse bore (58) in the region of an outlet of the first pumping means (10) and preferably at least one in the rotor shaft (16 ) arranged second transverse bore (64) which ends between two adjacent rotor discs (28) of the second pumping means (12)

13. Multi-inlet vacuum pump according to one of claims 8 to 12, characterized by a in the outlet region of the first pumping means (10) arranged sealing disc (54) extending from the pump housing (14) to the rotor shaft (16).

14, multi-inlet vacuum pump according to claim 13, characterized in that the first transverse bore (58) in the conveying direction (36) between the last rotor disc (20) of the first pumping means (10) and the sealing disc (54) is arranged.

Multi-injection vacuum pump according to one of claims 8 to 14, characterized in that at least the last rotor disc (68) of the first pumping device (10) is designed such that it forms part of the second fluid flow sucked through the intermediate inlet (38) (40) against the conveying direction (36) in the direction of the first pumping device (10) promotes.