Pump unit

Abstract

To improve a vacuum performance of a split-flow vacuum pump having a Holweck pump stage by increasing a discharge velocity in an inflow region of the Holweck pump stage of a vacuum pump, especially a turbo molecular vacuum pump or a pump unit for a vacuum system.SOLUTION: A unit comprises a Holweck pump stage 17, and the Holweck pump stage has a Holweck sleeve 21 rotating around a rotation axial line 19 as a center during a pump operation, and a Holweck stator 23. The Holweck stator has a Holweck web 25 on a side facing the Holweck sleeve. The Holweck stator, or the radially outermost Holweck stator if there are plural Holweck stators, has plural radial inflow openings 27 in an inflow region 26. The inflow openings are dispersed in a circumferential direction, and separated from one another by a support part extending in an axial direction.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a pump unit for a vacuum pump, in particular a turbomolecular vacuum pump or a vacuum system, comprising at least one Holweck pump stage, which has one or more Holweck sleeves that rotate about a rotation axis during pump operation, and one or more Holweck stators, each having at least one Holweck web on the side facing the Holweck sleeve.

[0002] Furthermore, the present invention relates to a vacuum pump, in particular a turbomolecular vacuum pump, comprising at least one pump unit as disclosed herein.The present invention further relates to a vacuum system comprising at least one vacuum chamber, at least one pump unit as disclosed herein, and at least one recipient to be evacuated. [Background technology]

[0003] Pump units of the type mentioned at the outset are basically known and in practice often have, in addition to at least one Holweck pump stage, one or more turbomolecular pump stages, the rotating components of which, i.e., the rotor blades, rotate together with one or more Holweck sleeves around a common axis of rotation during operation.

[0004] Such a pump unit may be part of a stand-alone vacuum pump that is flow-technically connected to the respective recipient for the respective pump application in order to evacuate the recipient, in which case the pump unit is located in its own pump housing that forms the outer housing of the vacuum pump.

[0005] This type of pump unit is also known in the form of a so-called split-flow pump, in which intake is not, or is not only, performed via an axial intake opening, and therefore parallel to the axis of rotation, but the pump housing of the split-flow pump, for example a so-called box-type housing, has one or more radial intake openings spaced apart from one another along the axis of rotation. These radial intake openings of the split-flow pump are also called radial extractors, intermediate extractors, ports, or intake ports. During operation, each radial intake opening of the split-flow pump is connected to a corresponding opening in the recipient to be evacuated.

[0006] Furthermore, pump units of the aforementioned type are known which also have a housing and in principle form a stand-alone vacuum pump, but which in practice are inserted into another housing for pumping operation. Pump units of this type are also called cartridge pumps, and their housings are also called cartridge sleeves or simply pump housings. The other housing may be a separate housing which, together with the pump unit accommodated therein, forms the stand-alone vacuum pump. The other housing may be, for example, a box-type housing, i.e., a stand-alone split-flow pump may have a pump unit without its own housing or a pump unit with its own housing, in particular a cartridge pump, in its box-type housing, i.e., in an outer housing also referred to simply as a pump housing.

[0007] Alternatively, the separate housing may be an integral component of a vacuum system having a vacuum chamber used to house the pump unit as well as a recipient in rigid fluid connection to the vacuum pump, the recipient being able to be evacuated by the pump unit housed within the vacuum chamber.

[0008] Therefore, pump units, i.e. in particular cartridge vacuum pumps, having a housing, hereinafter also referred to as a base housing, can be accommodated, in particular inserted, in various other housings, which in the following should be understood under the general term "outer housing". The outer housing may be a stand-alone housing, as in the case of pump units without a base housing, or the outer housing may form an integral component of a vacuum system, such as a chamber housing.

[0009] In the present disclosure, the or each opening of the outer housing which is flow-technically connected to the pump unit housed therein is referred to as a radial extraction opening. When the pump unit has its own base housing, i.e. in particular a cartridge pump, then the or each opening of the base housing which is flow-technically connected to the radial extraction opening of the outer housing is referred to in the present disclosure as a radial intake opening, thereby avoiding confusion.

[0010] A Holweck pump stage has one or more Holweck stators. A Holweck sleeve is located radially inward of the Holweck stator, or the outermost Holweck stator if there are multiple Holweck stators, and rotates about the rotation axis during operation. When referring to a "Holbeck stator" hereinafter, the outermost Holweck stator is meant if the Holweck pump stage has multiple Holweck stators.

[0011] On the side facing the Holweck sleeve, the Holweck stator is provided with one or more Holweck webs, each extending along a curve having a gradient different from zero about the axis of rotation, so that on the side facing the Holweck sleeve, the Holweck stator is provided with a Holweck channel defined by the Holweck webs, which together with the side of the Holweck sleeve facing it form the pumping region of the Holweck stage.

[0012] In the case of a split-flow pump, the Holweck stator is provided with openings aligned with the radial extractions in the outer housing so that the gas to be pumped can reach this pumping region of the Holweck pump stage from the radial extractions, which openings are referred to in the present disclosure as radial inlet openings, and thus form the inlet region of the Holweck pump stage, the axial position of which, relative to the axis of rotation, is adjusted to the corresponding orientation of the radial extractions. Summary of the Invention [Problem to be solved by the invention]

[0013] The object of the present invention is to increase the pumping speed in the inlet region of a Holweck pump stage in a pump unit of the type mentioned at the beginning and thus to improve the vacuum performance, in particular of a split-flow vacuum pump having one or more Holweck pump stages. [Means for solving the problem]

[0014] The solution to this problem is achieved by the features of the respective independent claims.

[0015] In the pump unit, according to the invention, the Holweck stator, or if there are several Holweck stators, the outermost Holweck stator located radially outward, has several, in particular two, three or four, radial inlet openings in the inlet region, which are distributed around the circumference and separated from one another by support portions extending in the axial direction.

[0016] The multiple radial inlet openings provide a circumferential expansion of the inlet area. Instead of a single radial inlet opening, there are multiple inlet openings distributed around the circumferential direction. The support section provides the required mechanical stability of the Holweck stator.

[0017] The axial support sections may each extend exactly axially, i.e. parallel to the axis of rotation, or may also extend obliquely, connecting the two axially adjacent stator sections in the inlet region.

[0018] With regard to the circumferential dimension, it is conceivable, but not necessary, for all inlet openings to have the same circumferential length, and this applies correspondingly to the support part.

[0019] According to some embodiments, the radial inlet openings each have an elongated shape, such that the circumferential length of the inlet opening is greater than its axial length.

[0020] According to some developments, it may be provided that the radial inlet openings lie on a circle about the rotation axis, the radius of the circle lying perpendicular to the rotation axis. However, this is not essential. Alternatively, it may be provided that the radial inlet openings lie in a plane inclined to the rotation axis or on a curve extending about the rotation axis and having a gradient different from zero. In particular, the radial inlet openings lie on a spiral. This therefore results in the course of the inlet openings about the rotation axis including an axial component. Such a course of the radial inlet openings of the Holweck stator may be advantageous with regard to the pressure distribution within the Holweck pump stage or in the pumping region of the Holweck pump stage formed by the Holweck stator together with the respective Holweck sleeve.

[0021] A plane inclined relative to the axis of rotation may be understood within the scope of the present disclosure as a plane that does not extend perpendicularly to the axis of rotation but extends at an angle relative to the axis of rotation, so that the normal to the plane forms an angle with the axis of rotation that is different from zero and smaller than 90 degrees.

[0022] According to some embodiments, it can be provided that the support portions are each formed as a web or stay. In particular, the support portions may each extend over an angle in the circumferential direction in the range of 3 to 30 degrees, in particular in the range of 5 to 20 degrees, in particular over an angle of 10 degrees. The narrower the support portions, the greater the openness of the Holweck stator in the inlet region, which is provided in common by all inlet openings. The thickness of the support portions can be minimized so that sufficient mechanical stability of the Holweck stator is guaranteed and the openness of the inlet region is maximized.

[0023] According to some developments, at least some of the radial inlet openings and / or the support parts can be free of Holweck webs, and thus at least some of the Holweck webs can be interrupted in the inlet region, which allows for a further increase in the openness of the Holweck stator in the inlet region and thus a further increase in the exhaust speed.

[0024] According to some embodiments, the Holweck pump stage may be surrounded by a base housing having at least one radial inlet opening axially at the level of the inlet region of the Holweck stator.

[0025] As mentioned at the beginning, the pump unit having a base housing may be configured in particular to be accommodated, in particular to be inserted, into another housing. Such a pump unit is also referred to as a cartridge pump. The base housing is also referred to as a pump housing or a cartridge sleeve. As also already mentioned, the other housing is referred to in the present disclosure as an outer housing. The outer housing may be a pump housing of a stand-alone vacuum pump, for example a so-called box-type housing, or the outer housing may define a vacuum chamber used to accommodate the pump unit, the vacuum chamber being part of a vacuum system further comprising a recipient.

[0026] According to some embodiments, it can be provided that, axially at the level of the inlet area of ​​the Holweck stator, a radial gap circumferentially around the axis of rotation is formed between the Holweck stator and the base housing, such that the flow reaching the Holweck pump stage via the base housing can be distributed circumferentially by this annular gap and thus reach the pumping area between the Holweck stator and the Holweck sleeve over all radial inlet openings of the Holweck stator, and therefore practically over the entire circumference.

[0027] The radial gap may lie on a circle about the axis of rotation, or in a plane inclined to the axis of rotation, or on a curve extending about the axis of rotation and having a gradient different from zero, in particular on a spiral. In particular, the course of the radial gap may correspond to the course of the inlet openings of the Holweck stator.

[0028] According to some embodiments, the base housing has, axially at the level of the inlet region of the Holweck stator, a plurality of, in particular two, three or four, radial inlet openings that are distributed in the circumferential direction and separated from one another by axially extending retaining portions, so that, axially at the level of the inlet region of the Holweck stator, the base housing has a structure similar to the Holweck stator itself and therefore also has an increased openness due to the plurality of radial inlet openings.

[0029] In particular, it can be provided that the number of radial inlet openings of the Holweck stator is equal to the number of radial inlet openings of the base housing.

[0030] It may further be contemplated that the circumferential length of the radial inlet openings of the Holweck stator is at least substantially equal to the circumferential length of each of the radial inlet openings of the base housing, respectively.

[0031] According to some embodiments, it may be provided that the support portion of the Holweck stator and the holding portion of the base housing are offset relative to each other in the circumferential direction, which may promote flow guidance that leads to a further increase in the exhaust velocity.

[0032] Possible developments of the base housing with respect to the radial intake openings and the holding parts separating the intake openings from one another can correspond to the developments of the Holweck stator already described above with respect to the radial inlet openings and the supporting parts separating the inlet openings from one another.

[0033] It may therefore be envisaged that the radial intake openings of the base housing each have an elongated shape.

[0034] It may further be provided that the radial intake openings of the base housing lie on a circle about the axis of rotation, or in a plane inclined to the axis of rotation, or on a curve extending about the axis of rotation with a gradient different from zero, in particular helically. In particular, the course of the radial intake openings may correspond to the course of the radial inlet openings.

[0035] Furthermore, it may be provided that the holding portions of the base housing are each configured as webs or stays, and in particular in this case the holding portions each extend over an angle in the circumferential direction in the range of 3° to 30°, in particular in the range of 5° to 20°, in particular over an angle of 10°.

[0036] The cross-section of the support part of the Holweck stator and the cross-section of the support part of the base housing can be rectangular, but this is not essential. In principle, other cross-sectional shapes are also conceivable, which are designed in particular with regard to flow optimization and have, for example, curved curves without corners. The cross-section can be, for example, circular or elliptical, or rectangular or square with rounded corner areas.

[0037] A vacuum pump according to the invention, in particular configured as a turbomolecular vacuum pump, comprises at least one pump unit as disclosed herein and an outer housing, in which the pump unit is accommodated, the outer housing having a radial extraction section axially at the level of the inlet area of ​​the Holweck stator of the pump unit.

[0038] For example, the vacuum pump may be a split-flow vacuum pump having an outer housing, for example a so-called box-type housing. Such a vacuum pump can be used as a stand-alone pump and can be flow-technically connected to the respective recipient to be evacuated.

[0039] A vacuum system according to the invention comprises at least one vacuum chamber, at least one pump unit as disclosed herein, and at least one recipient to be evacuated, the vacuum chamber having a chamber housing as an outer housing, in which the pump unit is accommodated, the chamber housing having, axially at the level of the inlet area of ​​the Holweck stator of the pump unit, a radial extraction section, which is flow-connected to the recipient.

[0040] The pump unit of the vacuum pump may have its own base housing, i.e. may in particular be a cartridge vacuum pump. This also applies to the pump unit of the vacuum system.

[0041] In both cases, i.e., in the case of a vacuum pump and in the case of a vacuum system, the outer housing may have several radial extractions. In this case, it is possible for a radial extraction to be assigned to one or several turbomolecular pump stages, or for several radial extractions to be assigned to several turbomolecular pump stages arranged one after the other along the rotation axis. Regardless of whether the outer housing has one or several radial extractions, the outer housing may additionally have an axial intake opening. In the case of a pump unit with its own base housing, in particular a cartridge vacuum pump, the base housing may correspondingly have an axial intake opening in addition to the one or several radial intake openings. As already mentioned at the beginning, the flow entering through the axial intake opening runs at least approximately parallel to the rotation axis of the pump unit.

[0042] According to some embodiments, a radial gap may be provided between the outer housing on the one hand and the Holweck stator or the base housing on the other hand, circumferentially about the axis of rotation, at the height of the radial extraction of the outer housing in the axial direction. Such a radial gap forms a flow path leading radially outward to the periphery of the pump unit. The flow path promotes the distribution of the incoming flow over the entire circumference, thus promoting the utilization of all inlet openings of the Holweck stator, and thus resulting in a further increase in the pumping speed.

[0043] The axial height of the radial gap may be selected in various ways. The axial height may correspond to the axial height of the inlet region of the Holweck stator. Alternatively, the radial gap may have a smaller or larger axial height.

[0044] Furthermore, as in the case of the radial gap between the Holweck stator and the base housing described above, it can be provided that the radial gap between the outer housing and the Holweck stator or the base housing is located on a circle about the axis of rotation, or in a plane inclined to the axis of rotation, or on a curve extending about the axis of rotation with a gradient different from zero, in particular on a spiral. In particular, the course of the radial gap can correspond to the course of the inlet openings of the Holweck stator and / or to the course of the radial intake openings of the optionally present base housing.

[0045] In pump units that do not have their own housing, particularly in the case of split-flow pumps that are not cartridge pumps but have a box-type housing that forms the outer housing, when at least one Holweck pump stage and possibly further pump stages, for example one or more turbomolecular pump stages, are accommodated in an outer housing that forms the pump housing, and therefore an annular gap is provided between the inside of this outer housing and the outer housing of the Holweck stator.

[0046] In pump units with their own base housing, ie for example cartridge pumps, a radial gap is provided between the inside of the outer housing and the outside of the base housing.

[0047] The radial gap is limited in both axial directions, in particular in the axial region of the inlet region of the Holweck stator, i.e. the radial gap is located axially at the height of the inlet opening of the Holweck stator and, optionally when a base housing is provided, axially at the height of one or more radial intake openings of the base housing.

[0048] According to some embodiments of the present invention, such axial restriction of the radial gap is to some extent self-imposed when the radial gap is formed by a channel formed on the inside of the outer housing. Such a channel forms a circumferentially extending recess on the inside of the outer housing. The Holweck stator abuts on its outside against an area on the inside of the outer housing axially adjacent to the circumferential channel. Additionally, a seal may be provided, which serves to seal the axial area of ​​the unit consisting of the pump unit and the outer housing as a whole, including the inlet area of ​​the Holweck stator, thereby avoiding any adverse effects on the pumping speed in the inlet area.

[0049] Correspondingly, in a pump unit having a base housing, the outside thereof abuts against an inner region of an outer housing, which axially defines a circumferential channel formed therein.

[0050] Alternatively, the radial gap may be formed by a channel formed on the outside of the Holweck stator or the base housing, the outside of which is formed by a support portion of the Holweck stator located between the radial inlet openings. The channel provided on the outside of the Holweck stator, and thus the radial gap, may therefore be formed by the support portion having a smaller radial thickness and being recessed radially inward relative to an axially adjacent region of the outside of the Holweck stator.

[0051] Correspondingly, in a pump unit having a base housing, the retaining portion of the base housing that separates the radial intake openings is recessed radially inward relative to the axially adjacent area on the outside of the base housing to form a circumferential channel and thus a radial gap.

[0052] A combination of both measures is also possible, i.e. the radial gap may be formed by both a channel formed inside the outer housing and a channel formed outside the Holweck stator or base housing.

[0053] In general, it can be envisaged that the channel formed inside the outer housing, i.e., its channel bottom, may be located on a circle, but this is not essential: depending on the respective situation, for example the space conditions in the guest chamber, the radial depth of the channel may vary in the circumferential direction.

[0054] In principle, it is also possible to provide an annular gap without forming a channel inside the outer housing or outside the Holweck stator or base housing, in particular by having the Holweck stator or base housing arranged at a radial distance from the inside of the outer housing and acting in such a way that an axially sealing radial gap exists at the height of the inlet area of ​​the Holweck stator in the axial direction in order to seal this intermediate space axially.

[0055] Alternatively or additionally to the conventionally formed radial gaps, in some embodiments, it can be provided that the outer housing has a recess on its inner side at least in the region of one of the support parts of the Holweck stator or the holding part of the base housing, preferably in the region of each support part or holding part. Such a recess opens the respective support part or holding part radially outward, so that a flow can pass around the support part or holding part radially outward. Such a recess can therefore also be realized in order to distribute the incoming flow over the entire circumference, and thus to utilize the inlet area of ​​the Holweck stator over the entire circumference, which can further increase the pumping speed of the pump unit.

[0056] The turbomolecular pump stage may also have radial inlet openings, as in the Holweck pump stage disclosed herein. Therefore, the configuration of the radially outer Holweck stator with respect to its radial inlet region disclosed herein may also be provided in the turbomolecular pump stage, i.e., in the stator spacer sleeve, and this is hereby explicitly disclosed. The stator spacer sleeve is arranged between two stator vanes or adjacent to the stator vanes of the turbomolecular pump stage. Thus, the stator spacer sleeve, like the radially outer Holweck stator, may have a plurality of radial inlet openings, in particular two, three, or four, in the radial inlet region, which are distributed around the circumference and separated from one another by axially extending support portions.

[0057] A pump unit for a turbomolecular vacuum pump or vacuum system is also disclosed herewith, and is required both in combined form and in mutually independent form, the pump unit comprising at least one turbomolecular pump stage, which has rotor blades that rotate about a rotation axis during pumping operation, stator vanes that interact with the rotor blades to provide a pumping action, and at least one stator spacer sleeve, which has a plurality of, in particular two, three or four, radial inlet openings in its radial inlet area, which are distributed around the circumferential direction and separated from one another by axially extending support portions.

[0058] Possible developments of the turbomolecular pump stage correspond to the developments of the Holweck pump stage disclosed herein.

[0059] A turbomolecular vacuum pump is also disclosed and claimed, which comprises at least one such pump unit and an outer housing, the outer housing accommodating the pump unit, wherein the outer housing has a radial extraction portion axially at the level of the inlet area of ​​the stator spacer sleeve of the pump unit.

[0060] A vacuum system is also disclosed and claimed, comprising at least one vacuum chamber, at least one such pump unit, and at least one recipient to be evacuated, wherein the vacuum chamber has a chamber housing as an outer housing, in which the pump unit is accommodated, and the chamber housing has a radial extraction section axially at the level of the inlet region of the stator spacer sleeve of the pump unit, the extraction section being flow-connected to the recipient.

[0061] Possible developments of the turbomolecular vacuum pump and vacuum system correspond to the developments for the vacuum pump or vacuum system, respectively, disclosed herein for the Holweck pump stage.

[0062] In particular, turbomolecular pump stages may also be provided with one or more radial gaps, as disclosed herein for Holweck pump stages.

[0063] The invention will now be described, by way of example only, with reference to the drawings, in which: [Brief explanation of the drawings]

[0064] [Figure 1a] 1 shows diagrammatically possible pump configurations in which the pump unit according to the invention can be used; [Figure 1b] 1 shows diagrammatically possible pump configurations in which the pump unit according to the invention can be used; [Figure 2] 1A-1C show different views of a conventional split-flow vacuum pump, the pump unit of which may be constructed in accordance with the present invention; [Figure 3] 1A-1C show different views of a conventional cartridge vacuum pump, the pump unit of which may be formed in accordance with the present invention; [Figure 4] 1 shows a portion of a cartridge vacuum pump according to the invention in two different viewing directions; [Figure 5a] 5 shows a portion of the cartridge vacuum pump of FIG. 4 from another viewing angle. [Figure 5b] 5 shows a possible implementation of the cartridge vacuum pump of FIG. 4. [Figure 5c] 5 shows a possible implementation of the cartridge vacuum pump of FIG. 4. [Figure 6a] 1A and 1B show diagrammatically in cross section perpendicular to the axis of rotation various configurations according to the invention of a pump unit without its own base housing in a stand-alone outer housing; [Figure 6b] 1A and 1B show diagrammatically in cross section perpendicular to the axis of rotation various configurations according to the invention of a pump unit without its own base housing in a stand-alone outer housing; [Figure 6c]1A and 1B show diagrammatically in cross section perpendicular to the axis of rotation various configurations according to the invention of a pump unit without its own base housing in a stand-alone outer housing; [Figure 7a] 1 shows a schematic cross-section perpendicular to the axis of rotation of a pump unit according to the invention having its own base housing within an outer housing, in accordance with the invention; [Figure 7b] 1 shows a schematic cross-section perpendicular to the axis of rotation of a pump unit according to the invention having its own base housing within an outer housing, in accordance with the invention; [Figure 8a] 1 shows a partial view of a split-flow vacuum pump in cross section extending parallel to the axis of rotation according to one embodiment of the present invention. [Figure 8b] 1 shows a partial view of a split-flow vacuum pump in cross section extending parallel to the axis of rotation according to one embodiment of the present invention. DETAILED DESCRIPTION OF THE INVENTION

[0065] 1a shows a pumping arrangement in which a split-flow vacuum pump 13 is connected to a recipient 53 for evacuating the recipient 53 having several flow-technically interconnected chambers. From the point of view of the manufacturer of the vacuum pump 13, the recipient 53 is also referred to as a guest chamber, since it is in fact the customer of the pump manufacturer who uses the pump with his or her own recipient 53 in each case.

[0066] The vacuum pump 13 has a stand-alone pump housing 41. The pump housing 41 may be a so-called box-type housing, also referred to in the present disclosure as an outer housing. Within the pump housing is a pump unit 11, which includes, among other things, one Holweck pump stage 17 and two turbomolecular pump stages 63, each having a common rotor 65 for these pump stages 17, 63.

[0067] Each pump stage is assigned a radial extraction section 43 formed in the outer housing 41, which during pump operation communicates with an opening 54 of a respective chamber of the recipient 53.

[0068] For clarity of the drawing, only the Holweck sleeve 21 of the Holweck pump stage 17 is shown diagrammatically in FIG. 1a, whereas only the rotor blades 68 of each turbomolecular pump stage 63 are shown diagrammatically.

[0069] Another pump configuration is shown in Figure lb, where the guest chamber comprises a recipient 53 and a vacuum chamber 51, which also comprise several chambers connected to each other in terms of flow technology, and in this case the recipient 53 and the vacuum chamber 51 have a common housing, of which the outer housing 41, which forms the chamber housing of the vacuum chamber 51, is an integral component. However, it is not essential that the outer housing 41 is formed integrally with the housing of the recipient 53. The common housing may also have several separate sub-housings, which can be connected to each other for the respective pump applications, one of which is the outer housing 41 for the pump unit 11.

[0070] The pump unit 11 is located within the vacuum chamber 51 and therefore within the outer housing 41. The outer housing 41 of the pump unit 11 is therefore not a stand-alone pump housing in this pump configuration.

[0071] The pump unit 11 is a so-called cartridge vacuum pump. It has a base housing 31, also called a cartridge sleeve or simply a pump housing, in which the individual pump stages of the pump unit 11 are accommodated. In the example shown here, the pump stages are also one Holweck pump stage 17 and two turbomolecular pump stages 63, of which only the Holweck sleeve 21 of the Holweck pump stage 17 is shown diagrammatically, and of which only the rotor blades 68 of each turbomolecular pump stage 63 are shown diagrammatically. The rotating components 21, 68 of the pump stages 17, 63 are mounted on a common rotor 65.

[0072] The base housing 31 has an axial intake opening 37 and two radial intake openings 33, the axial intake opening 37 communicating with one of the chambers of the recipient 53, and the radial intake openings 33 each communicating with a radial extraction section 43 formed in the outer housing 41 and therefore communicating with an assigned chamber of the recipient 53.

[0073] The two pump configurations according to FIGS. 1a and 1b are known per se and serve to illustrate the various situations in which the pump unit 11 according to the invention can be used.

[0074] Another pump configuration, not shown, which can also be realized by the pump unit 11 according to the invention, is one in which the pump unit 11 has its own base housing 31 and is configured in particular as a cartridge vacuum pump, but in which the pump unit 11 is not inserted into a guest chamber as in Fig. 1b, but is instead located in a stand-alone outer housing, for example in a so-called box-type housing, as in Fig. 1a. Such a pump configuration therefore corresponds to the configuration of Fig. 1a, with the difference that the individual pump stages 17, 63 are located in their own base housing 31 and are therefore operable as a unit, i.e. as the pump unit 11, and can be inserted into the outer housing, thus forming a stand-alone split-flow vacuum pump.

[0075] An example of a split flow vacuum pump 13 according to the pump configuration of FIG. 1a is shown in FIG.

[0076] The outer housing 41 of the vacuum pump 13, configured as a box-type housing, has two radial extraction sections 43 in this example. A base part 61 of the vacuum pump 13 closes the outer housing 41 at its end face. In this base part 41, inter alia, a rotor 65 of the pump unit 11 (see the lower drawing in FIG. 2 ) is rotatably supported by a rolling bearing. At the other end, the rotor 65 is rotatably supported by a magnetic bearing. The pump unit 11 has a Holweck pump stage 17 and two turbomolecular pump stages 63 arranged axially spaced apart from one another. One of the radial extraction sections 43 is located between the two turbomolecular pump stages 63 with respect to the rotation axis 19 of the rotor 65.

[0077] The stator members of the individual pump stages, which do not rotate during operation, include the stator vanes 67 of the turbomolecular pump stage 63, a stator portion 69 arranged between the two turbomolecular pump stages 63, and the Holweck stators 23, 23a. The radially outermost Holweck stator 23, the stator vanes 67, and the stator portion 69 are located inside the outer housing 41. Between the two Holweck stators 23, 23a and radially inside the inner Holweck stator 23a, one Holweck sleeve 21, 21a is located, respectively, and the Holweck sleeve 21, 21a is attached to a Holweck hub 20, which is again connected to the rotor 65.

[0078] The Holweck sleeves 21, 21a and the rotor blades 68 of the turbomolecular pump stage 63 rotate together with the rotor 65 during operation.

[0079] On the side facing the respective Holweck sleeve 21, 21a, the Holweck stator 23, 23a is provided with a structure consisting of a Holweck web 25, which thus forms the respective pumping area. Such an arrangement, with two radially inner and outer Holweck sleeves 21, 21a, to which a Holweck stator 23, 23a is assigned, as shown in the lower part of Figure 2, is also called a nested Holweck arrangement.

[0080] 2 is used to illustrate one possible example of the construction of a conventional split-flow vacuum pump and is not in accordance with the present invention, since the Holweck pump stage 17 does not have a radial extraction in the outer housing 41 and is not configured in accordance with the present invention. Apart from that, the pump unit 11 in accordance with the present invention, and thus the split-flow vacuum pump in accordance with the present invention, may be configured as shown in FIG.

[0081] Correspondingly, FIG. 3 shows an example of a conventional cartridge vacuum pump, in which the Holweck pump stage 17 is not configured according to the invention, but in this case the pump unit 11 according to the invention may otherwise have the configuration as shown in FIG. 3.

[0082] According to Figure 3, the cartridge vacuum pump corresponds to the pump unit 11 according to Figure 2 and not only has a common rotor 65 with one Holweck pump stage 17 and two turbomolecular pump stages 63, but also a base housing 31 that accommodates the rotor 65 and the pump stages 17, 63. The base housing 31 is closed at its end by a base part 61 in which, inter alia, the rotor 65 is rotatably supported by a rolling bearing. At the other end, the rotor 65 is rotatably supported by a magnetic bearing.

[0083] lb, the base housing 31 is provided with an axial intake opening 37 and two radial intake openings 33. One of the radial intake openings 33 is located between the two turbomolecular pump stages 63 with respect to the rotational axis 19 of the rotor 65. The other radial intake opening 33 is located axially at the level of the Holweck pump stage 17.

[0084] Together with the rotor 65, during pump operation, the rotating blades 68 and Holweck hub 20 of the turbomolecular pump stage 63 again rotate with the Holweck sleeves 21, 21 a attached thereto. The fixed components of these pump stages 17, 63 are again the stator vanes 67 of the turbomolecular pump stage 63 and the Holweck stators 23, 23 a of the Holweck pump stage 17.

[0085] Figures 4 and 5a each show a portion of a vacuum pump 13 according to the invention configured as a cartridge vacuum pump, which may have a structure as described above in relation to Figure 3, except for the region of the Holweck pump stage formed according to the invention, which will be described in more detail below.

[0086] Figure 4 shows in an upper drawing a perspective view of a cut plane taken somewhat above the base portion 61, perpendicular to the rotor's axis of rotation 19, where the lower drawing of Figure 4 is a plan view of the portion of the vacuum pump 13 shown in the upper drawing.

[0087] 4 shows only the outer pumping region of the Holweck pump stage, which is formed by the outer, radially outermost Holweck stator 23 and the outer Holweck sleeve 21. As already explained, the Holweck stator 23 is provided with a helically extending Holweck stage 25 on its side facing the rotor sleeve 21. This design of the Holweck pump region is basically known.

[0088] A special feature with respect to the known Holweck pump stage is that the Holweck stator 23 has a large open inlet area 26, since the inlet area 26 has a plurality of, in this example three, radial inlet openings 27, which are distributed around the circumference and separated from one another by axially extending support portions 29. In this case, the support portions 29 are relatively narrow, i.e. have a short circumferential length compared to the inlet openings 27.

[0089] The base housing 31 has a corresponding configuration. In this axial region of the vacuum pump 13, i.e. axially at the level of the inlet region 26 of the Holweck stator 23, the base housing 31 is likewise provided with three intake openings 33. Every two adjacent intake openings 33 in the circumferential direction are separated from one another by a retaining portion 39 extending in the axial direction.

[0090] In this case, the support parts 29 of the Holweck stator 23 on the one hand and the retaining parts 39 of the base housing 31 on the other hand are offset relative to one another in the circumferential direction, specifically so that each one of the support parts 29 is positioned approximately in the center between two of the retaining parts 39 in the circumferential direction.

[0091] Furthermore, a radial gap 35 exists between the support portion 29 and the retaining portion 39. The radial gap 35 results from the fact that the radially outer portions of the support portions 29 each lie on a cylinder centered on the rotation axis 19 that has a reduced radial thickness compared to the axially adjacent regions of the base housing 31, i.e., is recessed radially outward, and has a smaller radius than the cylinder centered on the rotation axis 19 on which the radially inner portions of the retaining portions 39 lie.

[0092] With this configuration, the vacuum pump 13 has an open structure axially at the height of the Holweck pump stage 17 and over its entire circumference, interrupted exclusively by the relatively narrow support portion 29 of the Holweck stator 23 and the relatively narrow holding portion 39 of the base housing 33.

[0093] As the side view of Figure 5a shows, the radial inlet openings 33 of the base housing 31 have a greater axial height than the radial inlet openings 27 of the Holweck stator 23. Both the inlet openings 33 and the inlet openings 27 have an elongated shape, i.e., the circumferential length of each opening 33, 27 is several times its axial height. Furthermore, the support portion 29 and the retaining portion 39 are each relatively narrow, i.e., the circumferential length of each opening 33, 27 is several times the circumferential length of the respective support portion 29 or retaining portion 39.

[0094] As Figure 5a further shows, the support portion 29 and the retaining portion 39 do not each have a constant width over their axial length, but rather the support portion 29 and the retaining portion 39 extend towards axially adjacent regions of the base housing 31 or Holweck stator 23, respectively.

[0095] The specific shape, width and radial thickness of the support portion 29 or the holding portion 39 are selected in particular to provide sufficient support and sufficient mechanical stability to ensure optimal vibration characteristics.

[0096] FIG. 5 a shows the Holweck sleeve 21 interacting in a pumping manner with the Holweck stator 23 through the radial intake openings 33 in the base housing 31 and the radial inlet openings 27 in the Holweck stator 23 .

[0097] In contrast, the Holweck web is not shown in Fig. 5a. This is because, according to Fig. 5a, the Holweck stator 23 is configured in a manner corresponding to the embodiment of Fig. 5c, in which the Holweck web 25 is interrupted in the inlet region 26, so that in this region the radial inlet openings 27 of the Holweck stator 23 and their support parts 29 are also free of the Holweck web 25. However, this is not essential. Fig. 5b shows an alternative embodiment in which the Holweck web 25 is not interrupted in the inlet region 26. The configurations of Fig. 5a and 5c result in a more open inlet region 26 configuration compared to the configuration of Fig. 5b.

[0098] Although both the cartridge vacuum pump 13 according to Figure 3 and the cartridge vacuum pump 13 according to Figures 4 and 5a, 5b and 5c are functional in principle on their own, such cartridge vacuum pumps are, as already mentioned, in practice inserted into an outer housing which has, in the inlet region 26 of the Holweck stator 23 and thus in the intake region formed by the radial intake openings 33 of the base housing 31, a radial extraction, via which the gas to be pumped can reach the Holweck pump stages from the respective recipient.

[0099] The radial gap 35 described above and shown in Figures 4 and 5a is provided between the Holweck stator 23 and the base housing 31 so that the entire circumference of the Holweck pump stage is available for the inflow of the gas to be pumped, and therefore so that the gas can reach the pumping area between the Holweck stator 23 and the Holweck sleeve 21 through all the radial inlet openings 27 distributed around the circumference.

[0100] Additional measures for further promoting the circumferential distribution of the inflow will now be explained schematically using the example of a cartridge vacuum pump in Fig. 7b. These measures relate to the region between the base housing 31 and the outer housing 41. Further measures are possible in this region, which can also be applied to pump units 11 that do not have their own base housing, i.e., the configuration according to Fig. 1a. These measures will therefore first be explained below with reference to Figs. 6a, 6b and 6c, based on a split-flow vacuum pump 13, each shown only diagrammatically in a cross section perpendicular to the axis of rotation 19.

[0101] 6a shows an arrangement in which the pump unit does not have its own base housing but is accommodated in an outer housing 41 with a radial extraction 43 in the area of ​​the shown Holweck pump stage. The radially outer pumping area of ​​the Holweck pump stage is formed by the outer Holweck stator 23 and the outer Holweck sleeve 21. On the side facing the Holweck sleeve 21, the Holweck stator 23 is provided with a Holweck web 25.

[0102] In the illustrated inlet region, the Holweck stator 23 has three radial inlet openings 27 distributed in the circumferential direction, the inlet openings 27 being separated from one another by support portions 29 .

[0103] The outside of the support portion 29 and the inside of the outer housing 41 are positioned on a common cylinder centered on the rotation axis 19 .

[0104] In order to enable the gas entering via the radial extractions 43 to reach the pumping area between the Holweck stator 23 and the Holweck sleeve 21 via the entire circumference, i.e. via all three radial inlet openings 27, the outer housing 41 is provided on its inside with recesses 47 in the area of ​​each support part 29. This allows the flow entering via the radial extractions 43 to pass by the support parts 29 radially outward and then reach the pumping area via the respective next radial inlet opening 27.

[0105] The recesses 47 may extend over the entire axial height of the inlet region formed by the radial inlet openings 27 of the Holweck stator 23. A smaller or larger axial extension of the recesses 47 is likewise possible. The contour shape of the recesses 47, i.e., the circumferential course of the recesses 47, may in principle be configured arbitrarily. The simplest and most economical possible manufacturability and optimal flow guidance may form relevant criteria for the configuration of these recesses 47.

[0106] In the configuration according to FIG. 6b, the recesses 47 according to FIG. 6a are not provided. Nevertheless, to achieve circumferential distribution of the incoming gas, the support portion 29 has a reduced radial thickness, i.e., is recessed radially relative to the axially adjacent portion of the Holweck stator 23. This creates a channel 24 on the outside of the Holweck stator 23 between the inside of the outer housing 41 and the outside of the Holweck stator 23, which is formed by the outside of the support portion 29, thereby creating a radial gap between the outer housing 41 and the Holweck stator 23. Circumferential distribution of the incoming gas can be achieved via the radial gap formed by the channel 24. With such a configuration, machining of the inside of the outer housing 41 is not necessary.

[0107] As an alternative to the solution according to Figure 6b, according to Figure 6c a circumferential annular gap can be formed by forming a circumferential channel 45 inside the outer housing 41. With this solution, it is not necessary to reduce the radial thickness of the support part 29.

[0108] Both the channel 24 mentioned with reference to Figure 6b and the channel 55 according to Figure 6c may extend over the entire axial height of the inlet area formed by the inlet openings 27 of the Holweck stator 23. A smaller or larger axial extension of the channels 24 or 55 is likewise possible.

[0109] 6a, 6b and 6c are optionally possible. In addition to the radial reduction of the support portion 29, a recess 47 according to Fig. 6a may be provided, for example. Furthermore, in addition to the channel 24 according to Fig. 6b, a circumferential channel 45 may be provided on the inside of the outer housing 41, as shown in Fig. 6c, i.e. the radial gap between the Holweck stator 23 and the outer housing 41 may be formed in common by a channel on the outside of the Holweck stator 23 and a channel on the inside of the outer housing 41.

[0110] As mentioned above, Figures 7a and 7b each show an arrangement with a cartridge-type pump unit having its own base housing 31 and inserted into an outer housing 41 with a radial extraction section 43 in the region of the inlet area formed axially by the intake openings 27 of the Holweck stator 23.

[0111] The cartridge vacuum pump configuration corresponds in the inlet region to the vacuum pump configuration shown in Figures 4, 5a, and 5c. Corresponding to the drawings in Figures 6a, 6b, and 6c, the radially outer Holweck pump region is shown, which includes the outer Holweck stator 23 and its associated Holweck sleeve 21. The Holweck stator 23 has three radial inlet openings 27 distributed circumferentially, and the base housing 31 has three radial inlet openings 33 distributed circumferentially, the inlet openings 33 being circumferentially offset relative to the inlet openings 27 of the Holweck stator 23. The inlet openings 27 of the Holweck stator 23 are separated by relatively narrow support portions 29, while a retaining portion 39 of the base housing 31 separates each pair of adjacent radial inlet openings 33 of the base housing 31 from one another.

[0112] The retaining portion 39 of the base housing 33 abuts on its outer side against the inside of the outer housing 41. Nevertheless, the gas entering through the radial extraction portion 43 of the outer housing 41 can be dispersed circumferentially because there are flow paths leading to all three radial inlet openings 27 of the Holweck stator 23. Dispersion is facilitated by the radial gap 35 between the Holweck stator 23 and the base housing 31, which has already been explained in connection with Figures 4 and 5a. The radial gap 35 is created by reducing the radial thickness of the retaining portion 39, i.e., by the retaining portion 39 being recessed radially outward with respect to the axially adjacent regions of the base housing 31.

[0113] Already, such openness of the overall structure, with multiple radial inlet openings 27 in the Holweck stator 23 and multiple radial intake openings 33 in the base housing 31, results in an increase in exhaust velocity compared to known configurations.

[0114] A further improvement in the pumping speed is achieved, according to Fig. 7b, if, corresponding to the configuration already described with reference to Fig. 6c, a circumferential channel 45 is formed on the inside of the outer housing 41, which forms a radial gap between the base housing 31 and the outer housing 41, via which the gas flowing in through the radial extraction section 43 can be dispersed in the circumferential direction. The radial gap 45 allows the gas to flow radially outwardly past the holding section 39 of the base housing 31.

[0115] For possible additional or alternative configurations of the embodiment according to Figures 7a and 7b, reference is also made to the configurations described above in connection with Figures 4, 5a, 5b, 5c and 6a, 6b, 6c. Thus, for example, in the configuration according to Figure 7a, a recess corresponding to recess 47 according to Figure 6a may be provided on the inside of outer housing 41, thereby allowing flow around retaining portion 39 accordingly.

[0116] 8a and 8b each show a portion of the split-flow vacuum pump 13 in a cross section extending parallel to the axis of rotation, in which only the radially outer Holweck stator 23 of one of the Holweck pump stages is shown. The radially outer Holweck stator 23 is arranged in an outer housing 41 configured as a box-type housing and is provided with a radial extraction section 43. Figures 8a and 8b serve, inter alia, to illustrate the various courses of the radial inlet openings 27 of the Holweck stator 23, as already mentioned elsewhere.

[0117] Corresponding to Figure 5c, here the Holbeck webs 25 are interrupted in the inlet region of the Holbeck stator 23, so that the radial inlet openings 27 of the Holbeck stator 23 and their supporting parts 29 are not provided with the Holbeck webs 25 in this region.

[0118] Corresponding to Figure 6c, here a circumferential channel 45 is formed inside the outer housing 41, thereby achieving a circumferential dispersion of the incoming flow entering through the radial extraction section 43.

[0119] The two embodiments of Figures 8a and 8b differ in that, according to Figure 8a, the radial inlet openings 27 lie on a circle about the axis of rotation 19, the radius of the inlet openings 27 lying perpendicular to the axis of rotation 19, while according to Figure 8b, the radial inlet openings 27 lie on a spiral about the axis of rotation 19, the winding direction of the spiral being opposite to the winding direction of the course of the Holweck web 25. Alternatively, the winding direction of the spiral and the winding direction of the course of the Holweck web 25 may be identical. Alternatively, the radial inlet openings may lie in a plane inclined to the axis of rotation 19. The channels 45 provided on the inside of the outer housing 41 respectively follow the course of the inlet openings 27, i.e. in this embodiment, they lie correspondingly on a circle about the axis of rotation 19 (Figure 8a) or on a spiral about the axis of rotation 19 (Figure 8b).

[0120] Two paths, namely a circle according to FIG. 8a and a spiral path according to FIG. 8b, may also be provided with a Holweck stator 23 in which the Holweck web 25 is uninterrupted, corresponding to FIG. 5b. The present application relates to the invention described in the claims, but also includes the following as other aspects. 1. In a vacuum pump (13), in particular a turbomolecular vacuum pump or a pump unit (11) for a vacuum system (15), at least one Holweck pump stage (17), said Holweck pump stage (17) having one or more Holweck sleeves (21) and one or more Holweck stators (23) which rotate about a rotation axis (19) during pump operation, said Holweck stators (23) each having at least one Holweck web (25) on the side facing said Holweck sleeves (21); A pump unit (11) in which the Holweck stator, or in the case of a plurality of Holweck stators, the outermost Holweck stator (23) located radially outward, has a plurality of, in particular two, three or four, radial inlet openings (27) in the inlet region (26), the inlet openings (27) being distributed in the circumferential direction and separated from one another by support portions (29) extending in the axial direction. 2. The pump unit (11) according to claim 1, wherein each of said radial inlet openings (27) has an elongated shape. 3. 3. A pump unit according to claim 1 or 2, wherein the radial inlet openings (27) are located on a circle centered on the axis of rotation (19), or in a plane inclined to the axis of rotation (19), or on a curve extending about the axis of rotation (19) with a gradient different from zero, in particular on a spiral. 4. 4. The pump unit according to any one of claims 1 to 3, wherein the support portions (29) are each formed as a web or stay, and in particular the support portions (29) each extend over an angle in the circumferential direction in the range of 3 to 30 degrees, in particular 5 to 20 degrees, in particular 10 degrees. 5. 5. The pump unit according to any one of claims 1 to 4, wherein at least a part of the radial inlet opening (27) and / or the support portion (29) is free from a Holweck web. 6. 6. The pump unit according to any one of claims 1 to 5, wherein the Holweck pump stage (17) is surrounded by a base housing (31) having at least one radial intake opening (33) axially at the height of the inlet region (26) of the Holweck stator (23). 7. 10. The pump unit of claim 6, wherein a radial gap (35) circumferentially circumferentially about the rotation axis (19) is formed between the Holweck stator (23) and the base housing (31) at the height of the inlet region (26) of the Holweck stator (23) in the axial direction. 8. 8. A pump unit according to claim 6 or 7, wherein the base housing (31) has a plurality of, in particular two, three or four, radial intake openings (33) which are circumferentially distributed in the axial direction at the height of the inlet region (26) of the Holweck stator (23) and separated from one another by axially extending retaining portions (39). 9. the number of the inlet openings (27) in the radial direction of the Holweck stator (23) is the same as the number of the inlet openings (33) in the radial direction of the base housing (31); and / or 9. The pump unit according to any one of claims 6 to 8, wherein the support portion (29) of the Holweck stator (23) and the holding portion (39) of the base housing (31) are circumferentially offset from each other. 10. the radial intake openings (33) of the base housing (31) each have an elongated shape and extend about the rotation axis (19); and / or the radial air intake openings (33) of the base housing (31) lie on a circle centered on the axis of rotation (19) or in a plane inclined to the axis of rotation or on a curve extending about the axis of rotation (19) with a gradient different from zero, in particular a spiral; and / or 10. Any one of the pump units 6 to 9 above, wherein the retaining portions (39) of the base housing (31) are formed as webs or stays, and in particular the retaining portions (39) extend in the circumferential direction over an angle ranging from 3 to 30 degrees, in particular from 5 to 20 degrees, in particular over an angle of 10 degrees. 11. In a vacuum pump (13), in particular a turbomolecular vacuum pump, A vacuum pump (13) comprising at least one pump unit (11) according to any one of 1 to 10 above, and an outer housing (41), wherein the pump unit (11) is accommodated within the outer housing (41), and the outer housing (41) has a radial extraction portion (43) axially at the height of the inlet region (26) of the Holweck stator (23) of the pump unit (11). 12. In a vacuum system (15), At least one vacuum chamber (51), at least one pump unit (11) according to any one of 1 to 10 above, and at least one recipient (53) to be evacuated; The vacuum chamber (51) has a chamber housing as an outer housing (41), in which the pump unit (11) is accommodated, and the chamber housing has a radial extraction section (43) axially at the level of the inlet area (26) of the Holweck stator (23) of the pump unit (11), and the extraction section (43) is flow-connected to the recipient (53). 13. The vacuum pump (13) of claim 11 or the vacuum system (15) of claim 12, wherein a radial gap (55) is provided between the outer housing (41) on the one hand and the Holweck stator (23) or the base housing (31) on the other hand, circling around the rotation axis (19) at the height of the extraction portion (43) in the radial direction of the outer housing (41). 14. The vacuum pump (13) or vacuum system (15) of claim 13, wherein the radial gap (55) is formed at least in part by a channel (45) formed inside the outer housing (41) and / or a channel (24, 36) formed outside the Holweck stator (23) or the base housing (31). 15. 15. The vacuum pump (13) or vacuum system (15) of claim 13 or 14, wherein the outer housing (41) has a recess (47) inside the outer housing (41) at least in the region of one of the support portions (29) of the Holweck stator (23) or in the region of the holding portion (39) of the base housing (31), preferably in the region of each of the support portions (29) or holding portions (39). [Explanation of symbols]

[0121] 11 Pump unit 13 Vacuum pump 15 Vacuum System 17 Holbeck pump stage 19 Rotation axis 20 Holbeck Hub 21 Holbeck Sleeve 21a Holbeck Sleeve 23 Holbeck Stator 23a Holbeck Sleeve 24 channels 25 Holbeck Webb 26 Inflow area 27 Radial inlet opening of Holweck stator 29 Holweck stator support 31 Base Housing 33 Radial intake openings in base housing 35 Radial clearance 36 channels 37 Axial intake opening in base housing 39 Base housing retaining part 41 Outer housing, pump housing 43 Radial extraction section 45 channels 47 Recess 51 Vacuum Chamber 53 Recipient 54 Aperture 55 Radial clearance 61 Base part 63 Turbomolecular pump stage 65 rotor 67 Stator blade 68 Moving blade 69 Stator part

Claims

1. A pump unit (11) for a vacuum pump (13) or a vacuum system (15), at least one Holweck pump stage (17), said Holweck pump stage (17) having one or more Holweck sleeves (21) and one or more Holweck stators (23) which rotate about a rotation axis (19) during pump operation, said Holweck stators (23) each having at least one Holweck web (25) on the side facing said Holweck sleeves (21); the Holweck stator, or if there are several Holweck stators, the outermost one (23) in the radial direction, has in its inlet region (26) a plurality of radial inlet openings (27), the inlet openings (27) being distributed in the circumferential direction and separated from one another by axially extending support portions (29); The Holweck pump stage (17) is surrounded by a base housing (31) having at least one radial intake opening (33) at the level of the inlet area (26) of the Holweck stator (23) in the axial direction, The base housing (31) has a plurality of radial intake openings (33) that are circumferentially distributed in the axial direction at the height of the inlet region (26) of the Holweck stator (23) and separated from each other by axially extending retaining portions (39).

2. 2. A pump unit (11) according to claim 1, wherein the radial inlet openings (27) each have an elongated shape.

3. 2. A pump unit according to claim 1, wherein the radial inlet openings (27) lie on a circle centered on the axis of rotation (19), or in a plane inclined relative to the axis of rotation (19), or on a curve extending about the axis of rotation (19) with a gradient different from zero, or on a spiral.

4. 2. A pump unit according to claim 1, wherein the support portions (29) are formed as webs or stays, respectively.

5. A pump unit as described in claim 4, wherein the support portions (29) each extend over an angle of 3 to 30 degrees in the circumferential direction.

6. 2. A pump unit according to claim 1, wherein at least a portion of the radial inlet openings (27) and / or the support portions (29) are free from Holweck webs.

7. 2. The pump unit according to claim 1, wherein a radial gap (35) circumferentially circumferentially about the rotation axis (19) is formed between the Holweck stator (23) and the base housing (31) at the height of the inlet region (26) of the Holweck stator (23) in the axial direction.

8. 2. The pump unit according to claim 1, wherein the number of the inlet openings (27) in the radial direction of the Holweck stator (23) is the same as the number of the inlet openings (33) in the radial direction of the base housing (31), and / or the support part (29) of the Holweck stator (23) and the holding part (39) of the base housing (31) are offset from each other in the circumferential direction.

9. the radial intake openings (33) of the base housing (31) each have an elongated shape and extend about the rotation axis (19); and / or the radial air intake openings (33) of the base housing (31) are located on a circle centered on the axis of rotation (19), or in a plane inclined relative to the axis of rotation, or on a curve extending about the axis of rotation (19) with a gradient different from zero, or on a spiral; and / or 2. The pump unit according to claim 1, wherein the retaining portions (39) of the base housing (31) are formed as webs or stays, respectively.

10. A pump unit as described in Claim 9, wherein the retaining portions (39) each extend over an angle of 3 degrees to 30 degrees in the circumferential direction.

11. In the vacuum pump (13), 11. A vacuum pump (13) comprising at least one pump unit (11) according to any one of claims 1 to 10 and an outer housing (41) in which the pump unit (11) is accommodated, the outer housing (41) having a radial extraction section (43) axially at the level of the inlet area (26) of the Holweck stator (23) of the pump unit (11).

12. In a vacuum system (15), at least one vacuum chamber (51), at least one pump unit (11) according to any one of claims 1 to 10, and at least one recipient (53) to be evacuated, The vacuum chamber (51) has a chamber housing as an outer housing (41), in which the pump unit (11) is accommodated, and the chamber housing has a radial extraction section (43) axially at the level of the inlet area (26) of the Holweck stator (23) of the pump unit (11), the extraction section (43) being flow-connected to the recipient (53).

13. 12. The vacuum pump (13) according to claim 11, wherein a radial gap (55) is provided between the outer housing (41) on the one hand and the Holweck stator (23) or the base housing (31) on the other hand, in the axial direction at the height of the extraction portion (43) in the radial direction of the outer housing (41), and around the axis of rotation (19).

14. 14. A vacuum pump (13) according to claim 13, wherein the radial gap (55) is formed at least in part by a channel (45) formed inside the outer housing (41) and / or a channel (24, 36) formed outside the Holweck stator (23) or the base housing (31).

15. 14. A vacuum pump (13) according to claim 13, wherein the outer housing (41) has a recess (47) on the inside thereof at least in the region of one of the support portions (29) of the Holweck stator (23), or in the region of a holding portion (39) of the base housing (31), or in the region of each of the support portions (29) of the Holweck stator (23), or in the region of each of the holding portions (39) of the base housing (31).

16. 13. The vacuum system (15) according to claim 12, wherein a radial gap (55) is provided between the outer housing (41) on the one hand and the Holweck stator (23) or the base housing (31) on the other hand, circumferentially about the axis of rotation (19) at the height of the extraction portion (43) in the radial direction of the outer housing (41).

17. 17. The vacuum system (15) of claim 16, wherein the radial gap (55) is at least partially formed by a channel (45) formed inside the outer housing (41) and / or a channel (24, 36) formed outside the Holweck stator (23) or the base housing (31).

18. 17. The vacuum system (15) according to claim 16, wherein the outer housing (41) has a recess (47) on the inside thereof at least in the region of one of the support portions (29) of the Holweck stator (23), or in the region of a holding portion (39) of the base housing (31), or in the region of each of the support portions (29) of the Holweck stator (23), or in the region of each of the holding portions (39) of the base housing (31).

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