Pumping unit

Abstract

The invention relates to a pump unit for a vacuum pump, in particular a turbomolecular vacuum pump, or for a vacuum system, with at least one Holweck pumping stage, which comprises one or more Holweck sleeves rotating about an axis of rotation during pumping operation, and one or more Holweck stators, each of which has at least one Holweck web on a side facing a Holweck sleeve, wherein the Holweck stator or - in the case of several Holweck stators - the outer, radially outermost Holweck stator comprises in an inflow region a plurality of, in particular two, three or four, radial inflow openings, which are arranged distributed in the circumferential direction and are separated from one another by support sections running in the axial direction.

Description

[0001] The invention relates to a pump unit for a vacuum pump, in particular a turbomolecular vacuum pump, or for a vacuum system, with at least one Holweck pumping stage, which comprises one or more Holweck sleeves rotating about an axis of rotation during pumping operation, and one or more Holweck stators, each of which has at least one Holweck web on a side facing a Holweck sleeve.

[0002] The invention further relates to a vacuum pump, in particular a turbomolecular vacuum pump, having at least one pump unit as disclosed herein. The invention also relates to a vacuum system having at least one vacuum chamber, at least one pump unit as disclosed herein, and at least one recipient to be evacuated.

[0003] Pump units of the type mentioned above are generally known and in practice usually have, in addition to at least one Holweck pump stage, one or more turbomolecular pump stages, whose rotating components - namely the rotor blades - rotate around the common axis of rotation during operation together with the Holweck sleeve(s).

[0004] Such a pump unit can be part of a standalone vacuum pump, which is fluidly connected to a specific vacuum chamber for a specific pumping application in order to evacuate it. The pump unit is then located in a separate pump housing, which forms the outer casing of the vacuum pump.

[0005] Such vacuum pumps are also known in the form of so-called split-flow pumps, in which the suction does not occur, or not only, via an axial suction port and thus parallel to the rotational axis. Instead, the pump housing, for example a so-called box-type housing, has one or more radial suction ports arranged at a distance from one another along the rotational axis. These radial suction ports of a split-flow pump are also referred to as radial taps, intermediate taps, ports, or intake ports. During operation, each radial suction port of the split-flow pump is connected to a corresponding port in the container to be evacuated.

[0006] Furthermore, pump units of the type mentioned above are known which also have a housing and are in principle independent vacuum pumps, but which in practice are inserted into another housing for pumping operation. Such pump units are also referred to as cartridge pumps and their housings are also referred to as cartridge sleeves or simply as pump housings. The additional housing can be a separate housing which, together with the pump unit accommodated therein, forms an independent vacuum pump. The additional housing can, for example, be a box-type housing, i.e. a standalone split-flow pump can contain in its box-type housing - i.e. the outer housing also simply referred to as the pump housing - either a pump unit without its own housing or a pump unit with its own housing, in particular a cartridge pump.

[0007] Alternatively, the further housing may be an integral part of a vacuum system which, in addition to a vacuum chamber serving to accommodate the pump unit, comprises a recipient which is in fixed flow connection to this vacuum pump and which can be evacuated with the pump unit accommodated in the vacuum chamber.

[0008] A pump unit with a housing (hereinafter also referred to as a base housing), in particular a cartridge vacuum pump, can therefore be accommodated, in particular inserted, into various additional housings, which will be collectively referred to as the "outer housing" below. The outer housing can either be a standalone housing—as in a pump unit without a base housing—or the outer housing can form an integral part of a vacuum system as a chamber housing.

[0009] In the present disclosure, the or each opening of a respective outer housing that is fluidly connected to a respective pump unit accommodated therein is uniformly referred to as a radial tapping. If the pump unit has its own base housing, i.e., in particular, it is a cartridge pump, then a respective opening of this base housing that is fluidly connected to a radial tapping of the outer housing is referred to in the present disclosure as a radial suction opening to avoid confusion.

[0010] Holweck pump stages have one or more Holweck stators. Radially inside the Holweck stator or – in the case of multiple Holweck stators – the outer, radially outermost Holweck stator is the Holweck sleeve, which rotates around the rotational axis during operation. When reference is made to "the Holweck stator" below, in the case of multiple Holweck stators, this refers to the outer, radially outermost Holweck stator.

[0011] On its side facing the Holweck sleeve, the Holweck stator is provided with one or more Holweck webs, each of which runs around the rotational axis along a curve with a non-zero gradient. As a result, the Holweck stator is provided with Holweck channels defined by the Holweck webs on its side facing the respective Holweck sleeve. These channels, together with the side facing the Holweck sleeve, form a pumping-active area of ​​the Holweck pumping stage.

[0012] To ensure that the gas to be pumped in a split-flow pump can flow from the radial tap of the outer casing into the active pumping area of ​​the Holweck pumping stage, an opening aligned with the radial tap is formed in the Holweck stator, which is referred to in this disclosure as a radial inflow opening. This inflow opening forms an inflow area of ​​the Holweck pumping stage, the axial position of which—relative to the rotational axis—is thus coordinated with the corresponding position of the radial tap.

[0013] The object of the invention is to increase the suction capacity at the inlet area of ​​the Holweck pumping stage in a pump unit of the type mentioned above and thus in particular to improve the vacuum performance of split-flow vacuum pumps which have one or more Holweck pumping stages.

[0014] This problem is solved by the features of the independent claims.

[0015] In the pump unit, it is provided according to the invention that the Holweck stator or - in the case of several Holweck stators - the outer, radially outermost Holweck stator in an inflow region comprises several, in particular two, three or four, radial inflow openings which are distributed in the circumferential direction and separated from one another by support sections running in the axial direction.

[0016] The multiple radial inlet openings increase the inlet area in the circumferential direction. Instead of a single radial inlet opening, there are several inlet openings distributed circumferentially. The support sections ensure the necessary mechanical stability of the Holweck stator.

[0017] The axial support sections can run exactly axially, i.e., parallel to the axis of rotation, or at an angle. In either case, the axial support sections connect the two stator sections axially adjacent to the inflow area.

[0018] Regarding the circumferential dimensions, it is possible, but not required, for all inlet openings to have the same circumferential length. The same applies to the support sections.

[0019] According to some embodiments, the radial inlet openings each have an elongated shape. The circumferential length of the inlet openings is thus greater than their axial height.

[0020] According to some developments, it can be provided that the radial inlet openings lie on a circle around the axis of rotation, wherein the radius of the circle is perpendicular to the axis of rotation. This is not mandatory, however. Alternatively, it can be provided that the radial inlet openings lie in a plane inclined with respect to the axis of rotation or on a curve running around the axis of rotation with a gradient other than zero. In particular, the radial inlet openings can lie on a helix. As a result, the course of the inlet openings around the axis of rotation consequently includes an axial component. With regard to pressure distribution within the Holweck pumping stage or the pump-active region of the Holweck pumping stage formed by the Holweck stator together with the respective Holweck sleeve, such a course of the radial inlet openings of the Holweck stator can be advantageous.

[0021] In the context of the present disclosure, a plane inclined with respect to the axis of rotation is to be understood as a plane which is not perpendicular to the axis of rotation, but rather oblique to the axis of rotation, so that a normal on the plane encloses an angle with the axis of rotation which is different from zero and which is less than 90°.

[0022] According to some embodiments, the support sections can each be designed as a web or strut. In particular, the support sections can each extend in the circumferential direction over an angle in the range of 3° to 30°, in particular from 5° to 20°, in particular over an angle of 10°. The narrower the support sections, the greater the openness of the Holweck stator in the inflow area provided jointly by all inflow openings. The thickness of the support sections can be minimized such that sufficient mechanical stability of the Holweck stator is ensured and the openness of the inflow area is maximized.

[0023] According to some developments, the radial inlet openings and / or the support sections can be at least partially free of Holweck webs. At least some of the Holweck webs can thus be interrupted in the inlet area. This can further increase the openness of the Holweck stator in the inlet area and thus further improve the suction capacity.

[0024] In some embodiments, the Holweck pumping stage may be surrounded by a base housing which has at least one radial suction opening axially at the level of the inflow area of ​​the Holweck stator.

[0025] As mentioned at the outset, a pump unit with a base housing can be designed in particular such that it can be accommodated, in particular inserted, into a further housing. Such pump units are also referred to as cartridge pumps. The base housing is also referred to as the pump housing or cartridge sleeve. As also already mentioned, the further housing is referred to as the outer housing in the present disclosure. The outer housing can be the pump housing of a stand-alone vacuum pump, e.g., a so-called box-type housing, or the outer housing can delimit a vacuum chamber serving to accommodate the pump unit, which is part of a vacuum system also comprising a recipient.

[0026] According to some embodiments, a radial gap circumferentially surrounding the rotational axis can be formed axially at the level of the inflow area of ​​the Holweck stator between the Holweck stator and the base housing. A flow entering the Holweck pumping stage via the base housing can be distributed circumferentially through this radial gap and thus reach the pumping-active area between the Holweck stator and the Holweck sleeve via all radial inflow openings of the Holweck stator and consequently practically over the entire circumference.

[0027] The radial gap can be located on a circle around the axis of rotation, in a plane inclined relative to the axis of rotation, or on a curve around the axis of rotation with a non-zero gradient, in particular on a helix. In particular, the shape of the radial gap can correspond to the shape of the inlet openings of the Holweck stator.

[0028] According to some embodiments, the base housing comprises a plurality of radial suction openings, in particular two, three, or four, arranged axially at the inflow area of ​​the Holweck stator, distributed in the circumferential direction and separated from one another by retaining sections extending in the axial direction. As a result, the base housing has a structure similar to the Holweck stator itself, axially at the inflow area of ​​the Holweck stator, and is thus also provided with an increased openness due to the plurality of radial suction 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 suction openings of the base housing.

[0030] Furthermore, it can be provided that the circumferential lengths of the radial inlet openings of the Holweck stator are each at least substantially equal to the circumferential length of each of the radial suction openings of the base housing.

[0031] According to some embodiments, the support sections of the Holweck stator and the holding sections of the base housing can be offset from one another in the circumferential direction. Such an arrangement can promote flow guidance, which leads to a further increase in suction capacity.

[0032] Possible further developments of the base housing with regard to the radial suction openings and the holding sections separating them from one another can correspond to the above-mentioned further developments of the Holweck stator with regard to the radial inlet openings and the support sections separating them from one another.

[0033] It can be provided that the radial suction openings of the base housing each have an elongated shape.

[0034] Furthermore, it can be provided that the radial suction openings of the base housing are located on a circle around the axis of rotation, or in a plane inclined relative to the axis of rotation, or on a curve running around the axis of rotation with a non-zero gradient, in particular on a helix. In particular, the course of the radial suction openings can correspond to the course of the radial inlet openings.

[0035] Furthermore, it can be provided that the holding sections of the base housing are each designed as a web or strut, in particular wherein the holding sections each extend in the circumferential direction over an angle in the range of 3° to 30°, in particular from 5° to 20°, in particular over an angle of 10°.

[0036] The cross-sections of the support sections of the Holweck stator and the cross-sections of the holding sections of the base housing can be rectangular. However, this is not mandatory. In principle, other cross-sectional shapes are also possible, designed specifically with flow optimization in mind, for example, a curved curve without corners. The cross-section can be circular or elliptical, or a rectangle or square with rounded corners.

[0037] A vacuum pump according to the invention, which is designed in particular 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, wherein the outer housing has a radial tap axially at the level of the inflow area of ​​the Holweck stator of the pump unit.

[0038] For example, the vacuum pump can be a split-flow vacuum pump with an outer housing, such as a so-called box-type housing. Such a vacuum pump can be used as a standalone pump and fluidically connected to the respective container 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 comprises a chamber housing as an outer casing, into which the pump unit is accommodated and which has a radial tap axially at the level of the inflow area of ​​the Holweck stator of the pump unit, which tap is in flow connection with the recipient.

[0040] The pump unit of the vacuum pump can have its own base housing, meaning it can 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 as well as in the case of a vacuum system, the outer housing can have a plurality of radial taps. In this case, it can be provided that a radial tap is assigned to one or more turbomolecular pump stages, or that a plurality of radial taps are assigned to several turbomolecular pump stages arranged one behind the other along the axis of rotation. Regardless of whether the outer housing has one or more radial taps, the outer housing can additionally have an axial suction opening. In the case of a pump unit with its own base housing, in particular a cartridge vacuum pump, the base housing can accordingly have an axial suction opening in addition to one or more radial suction openings. As already mentioned in the introduction, a flow entering through an axial suction opening runs at least essentially parallel to the axis of rotation of the pump unit.

[0042] According to some embodiments, a radial gap extending axially around the rotational axis can be provided between the outer housing on the one hand and the Holweck stator or the base housing on the other hand, at the level of the radial tap of the outer housing. Such a radial gap creates a flow path extending radially outward around the pump unit, which promotes the distribution of an incoming flow over the entire circumference and thus the utilization of all inlet openings of the Holweck stator, thus further increasing the pumping capacity.

[0043] The axial height of the radial gap can be selected differently. The axial height can correspond to the axial height of the inlet area of ​​the Holweck stator. Alternatively, the radial gap can also have a smaller or larger axial height.

[0044] Furthermore, as with an optionally provided, aforementioned radial gap between the Holweck stator and the base housing, the radial gap provided between the outer housing and the Holweck stator or base housing can be arranged either on a circle around the rotational axis, in a plane inclined relative to the rotational axis, or on a curve extending around the rotational axis with a non-zero gradient, in particular on a helix. In particular, the course of this radial gap can correspond to the course of the inlet openings of the Holweck stator and / or the course of the radial intake openings of an optionally provided base housing.

[0045] In the case of a pump unit without its own housing, i.e. in particular if it is not a cartridge pump, but rather the at least one Holweck pump stage and optionally further pump stages, for example one or more turbomolecular pump stages, are accommodated in an outer housing forming the pump housing, such as in the case of a split-flow pump with a box-type housing forming the outer housing, the annular gap is consequently provided between the inside of this outer housing and the outside of the Holweck stator.

[0046] In a pump unit with its own base housing, for example a cartridge pump, the radial gap is then provided between the inside of the outer housing and the outside of the base housing.

[0047] The radial gap is limited axially in both directions, in particular to the axial area of ​​the inflow area of ​​the Holweck stator, ie the radial gap is located axially at the level of the inflow openings of the Holweck stator and - if a base housing is optionally provided - axially at the level of the radial suction opening or suction openings of the base housing.

[0048] Such an axial limitation of the radial gap arises, to a certain extent, automatically if, according to some embodiments of the invention, the radial gap is formed by a channel on the inside of the outer housing. Such a channel represents a circumferentially extending recess on the inside of the outer housing. The outer side of the Holweck stator can rest against the areas of the inside of the outer housing that axially border the circumferential channel. In addition, seals can be provided to ensure that the entire axial area of ​​the arrangement comprising the pump unit and outer housing, encompassing the inflow area of ​​the Holweck stator, is sealed in order to prevent any impairment of the suction capacity in this inflow area.

[0049] Accordingly, in the case of a pump unit with a base housing, it is the outer side of the housing that bears against those areas of the inner side of the outer housing which axially delimit the circumferential channel formed on this inner side.

[0050] The radial gap can alternatively be formed by a channel formed on the outside of the Holweck stator or the base housing. The outside of the Holweck stator is formed by its support sections located between the radial inlet openings. The channel on the outside of the Holweck stator, and thus the radial gap, can thus be formed by providing the support sections with a smaller radial thickness and recessing radially inward relative to axially adjacent areas of the outside of the Holweck stator.

[0051] Accordingly, in a pump unit with a base housing, it is the holding sections separating the radial suction openings that spring back radially inwards to form a circumferential channel and thus the radial gap relative to axially adjacent areas of the outside of the base housing.

[0052] A combination of both measures is also possible, ie the radial gap can be formed by a channel formed on the inside of the outer housing as well as by a channel formed on the outside of the Holweck stator or the base housing.

[0053] In general, a channel formed on the inside of the outer casing, i.e., its channel base, can be arranged on a circle, although this is not mandatory. Depending on the specific situation, e.g., the space available in a customer chamber, the radial depth of the channel can vary in the circumferential direction.

[0054] In principle, it is also possible to provide an annular gap without a channel being formed on the inside of the outer housing or on the outside of the Holweck stator or the base housing, namely by arranging the Holweck stator or the base housing at a radial distance from the inside of the outer housing and ensuring axial sealing of this intermediate space in such a way that an axially sealed radial gap is present axially at the level of the inflow area of ​​the Holweck stator.

[0055] Alternatively or in addition to a radial gap, however formed, it can be provided according to some embodiments that the outer housing has a recess on its inner side at least in the region of one of the support sections of the Holweck stator or of a holding section of the base housing, preferably in the region of each support section or holding section. By means of such a recess, the respective support section or holding section is exposed radially on the outside, so that the support section or holding section can be flowed around radially on the outside. Such recesses can thus also enable a distribution of an incoming flow over the entire circumference and thus a full utilization of the inflow area of ​​the Holweck stator, whereby the suction capacity of the pump unit can be further improved.

[0056] A turbomolecular pump stage, like the Holweck pump stage disclosed herein, can also have a radial inflow region. The configurations of the radially outer Holweck stator disclosed herein regarding its radial inflow region can thus also be provided in a turbomolecular pump stage, namely in a stator spacer sleeve, which is expressly disclosed here. The stator spacer sleeve is arranged between two stator blades or adjacent to a stator blade of the turbomolecular pump stage. Analogous to the radially outer Holweck stator, the stator spacer sleeve can thus comprise, in the radial inflow region, several, in particular two, three, or four, radial inflow openings, which are distributed in the circumferential direction and separated from one another by support sections extending in the axial direction.

[0057] Also disclosed hereby and claimed both in combination and independently is a pump unit for a turbomolecular vacuum pump or for a vacuum system, having at least one turbomolecular pump stage, which comprises rotor blades rotating about an axis of rotation during pumping operation, stator blades cooperating with these in a pumping-effective manner, and at least one stator spacer sleeve, which comprises a plurality of, in particular two, three or four, radial inlet openings in a radial inflow region, which are arranged distributed in the circumferential direction and separated from one another by support sections running in the axial direction.

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

[0059] Also disclosed and claimed is a turbomolecular vacuum pump having at least one such pump unit and having an outer housing in which the pump unit is accommodated, wherein the outer housing has a radial tap axially at the level of the inflow area of ​​the stator spacer sleeve of the pump unit.

[0060] Also disclosed and claimed is a vacuum system having at least one vacuum chamber, at least one such pump unit and at least one recipient to be evacuated, wherein the vacuum chamber comprises a chamber housing as an outer housing, in which the pump unit is accommodated and which has a radial tap axially at the level of the inflow area of ​​the stator spacer sleeve of the pump unit, which tap is in flow connection with the recipient.

[0061] Possible further developments of the turbomolecular vacuum pump and the vacuum system correspond to the further developments for the vacuum pump and the vacuum system disclosed herein with regard to the Holweck pumping stage.

[0062] In particular, one or more radial gaps can also be provided for the turbomolecular pump stage, as disclosed here for the Holweck pump stage.

[0063] The present disclosure relates, among other things, to the following embodiments: 1. A pump unit (11) for a vacuum pump (13), in particular a turbomolecular vacuum pump, or for a vacuum system (15), comprising at least one Holweck pump stage (17) comprising one or more Holweck sleeves (21) rotating about a rotational axis (19) during pumping operation, and one or more Holweck stators (23), each having at least one Holweck web (25) on a side facing a Holweck sleeve (21). The Holweck stator or—in the case of multiple Holweck stators—the outer, radially outermost Holweck stator (23) comprises, in an inflow region (26), a plurality of, in particular two, three, or four, radial inflow openings (27) arranged distributed in the circumferential direction and separated from one another by support sections (29) extending in the axial direction. 2. A pump unit (11) according to embodiment 1, wherein the radial inflow openings (27) each have an elongated shape. 3.Pump unit according to embodiment 1 or 2, wherein the radial inflow openings (27) lie on a circle around the axis of rotation (19) or in a plane inclined relative to the axis of rotation or on a curve running around the axis of rotation (19) with a non-zero gradient, in particular on a helix. 4. Pump unit according to one of embodiments 1 to 3, wherein the support sections (29) are each designed as a web or strut, in particular wherein the support sections (29) each extend in the circumferential direction over an angle in the range of 3° to 30°, in particular from 5° to 20°, in particular over an angle of 10°. 5. Pump unit according to one of embodiments 1 to 4, wherein the radial inflow openings (27) and / or the support sections (29) are at least partially free of Holweck webs. 6.Pump unit according to one of embodiments 1 to 5, wherein the Holweck pumping stage (17) is surrounded by a base housing (31) which has at least one radial suction opening (33) axially at the level of the inflow region (26) of the Holweck stator (23). 7. Pump unit according to embodiment 6, wherein a radial gap (35) extending around the rotational axis (19) is formed between the Holweck stator (23) and the base housing (31) axially at the level of the inflow region (26) of the Holweck stator (23). 8. Pump unit according to embodiment 6 or 7, wherein the base housing (31) comprises a plurality of, in particular two, three, or four, radial suction openings (33) arranged axially at the level of the inflow region (26) of the Holweck stator (23), distributed in the circumferential direction and separated from one another by holding sections (39) extending in the axial direction.Pump unit according to one of embodiments 6 to 8, wherein the number of radial inflow openings (27) of the Holweck stator (23) is equal to the number of radial suction openings (33) of the base housing (31), and / or wherein the support sections (29) of the Holweck stator (23) and the holding sections (39) of the base housing (31) are offset from one another in the circumferential direction. 10.Pump unit according to one of embodiments 6 to 9, wherein the radial suction openings (33) of the base housing (31) each have an elongated shape and extend around the axis of rotation (19), and / or wherein the radial suction openings (33) of the base housing (31) lie on a circle around the axis of rotation (19) or in a plane inclined with respect to the axis of rotation or on a curve running around the axis of rotation (19) with a non-zero gradient, in particular on a helix, and / or wherein the holding sections (39) of the base housing (31) are each designed as a web or strut, in particular wherein the holding sections (39) each extend in the circumferential direction over an angle in the range from 3° to 30°, in particular from 5° to 20°, in particular over an angle of 10°. 11.Vacuum pump (13), in particular a turbomolecular vacuum pump, with at least one pump unit (11) according to one of the embodiments 1 to 10 and with an outer housing (41) in which the pump unit (11) is accommodated, wherein the outer housing (41) has a radial tap (43) axially at the level of the inflow region (26) of the Holweck stator (23) of the pump unit (11). 12. A vacuum system (15) comprising at least one vacuum chamber (51), at least one pump unit (11) according to one of embodiments 1 to 10, and at least one recipient (53) to be evacuated, wherein the vacuum chamber (51) comprises a chamber housing as an outer housing (41) into which the pump unit (11) is accommodated and which has a radial tap (43) axially at the level of the inflow region (26) of the Holweck stator (23) of the pump unit (11), which tap is in flow connection with the recipient (53).Vacuum pump (13) according to embodiment 11 or vacuum system (15) according to embodiment 12, wherein a radial gap (55) extending around the axis of rotation (19) is present axially between the outer housing (41) on the one hand and the Holweck stator (23) or the base housing (31) on the other hand, at the level of the radial tap (43) of the outer housing (41). 14. Vacuum pump (13) or vacuum system (15) according to embodiment 13, wherein the radial gap (55) is formed at least partially by a channel (45) formed on the inside of the outer housing (41) and / or by a channel (24, 36) formed on the outside of the Holweck stator (23) or the base housing (31). 15. Vacuum pump (13) or vacuum system (15) according to embodiment 13 or 14, wherein the outer housing (41) is at least in the region of one of the support sections (29) of the Holweck stator (23) or of a holding section (39) of the base housing (31), preferably in the region of each support section (29) orHolding section (39), has a recess (47) on its inside. .

[0064] The invention is described below by way of example with reference to the drawings. They show: Fig. 1a and 1b each schematically show a possible pump configuration in which a pump unit according to the invention can be used, Fig. 2 different views of a conventional split-flow vacuum pump, the pump unit of which can be designed according to the invention, Fig. 3 different views of a conventional cartridge vacuum pump, the pump unit of which can be designed according to the invention, Fig. 4 two different views of a part of a cartridge vacuum pump according to the invention, Fig. 5a another partial view of the cartridge vacuum pump of Fig. 4 , Fig. 5b and 5cpossible designs of the cartridge vacuum pump of Fig. 4 , Fig. 6a, 6b and 6c each show schematically in a section perpendicular to the axis of rotation different embodiments according to the invention of a pump unit without its own base housing in an independent outer housing, Fig. 7a and 7b each show schematically in a section perpendicular to the axis of rotation different embodiments according to the invention of a pump unit with its own base housing in an outer housing, and Fig. 8a and 8b each show part of a split-flow vacuum pump in a section parallel to the axis of rotation according to an embodiment of the invention.

[0065] Fig. 1a shows a pumping configuration in which a split-flow vacuum pump 13 is connected to a receiver 53 having several fluidically interconnected chambers in order to evacuate the receiver. From the perspective of the manufacturer of the vacuum pump 13, the receiver 53 is also referred to as a customer chamber, since in practice it is the pump manufacturer's customers who carry out a respective pumping application with their own receiver 53.

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

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

[0068] From the Holweck pump stage 17 in Fig. 1a For the sake of simplicity, only one Holweck sleeve 21 is shown schematically, while only the rotor blades 68 of the turbomolecular pump stages 63 are shown schematically.

[0069] Another pump configuration shows Fig. 1b There, the customer chamber comprises a recipient 53, again with several chambers fluidically connected to one another, and a vacuum chamber 51, wherein 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 part. However, it is not mandatory that the outer housing 41 be formed integrally with the housing of the recipient 53. The common housing can also have several separate sub-housings that can be connected to one another for a respective pumping application, one of which is the outer housing 41 for the pump unit 11.

[0070] The pump unit 11 is located in the vacuum chamber 51 and thus within the outer housing 41. The outer housing 41 of the pump unit 11 is therefore not an independent pump housing in this pump configuration.

[0071] The pump unit 11 is a so-called cartridge vacuum pump, which has a base housing 31, also referred to as a cartridge sleeve or simply as a pump housing, and in which the individual pump stages of the pump unit 11 are accommodated. In the example shown here, these pump stages are again a Holweck pump stage 17, of which only a Holweck sleeve 21 is shown schematically, and two turbomolecular pump stages 63, of which only the rotor blades 68 are shown schematically. These rotating components 21, 68 of these pump stages 17, 63 are attached to a common rotor 65.

[0072] The base housing 31 has an axial suction opening 37 which communicates with one of the chambers of the recipient 53, as well as two radial suction openings 33, each of which communicates with a radial tap 43 formed in the outer housing 41 and thus with the associated chamber of the recipient 53.

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

[0074] Not shown is a further pump configuration which can also be realized with a pump unit 11 according to the invention, in which the pump unit 11 again has its own base housing 31 and is designed in particular as a cartridge vacuum pump, but in which this pump unit 11 is not as in Fig. 1b is inserted into a customer chamber, but - insofar as in Fig. 1a - is located in a separate external housing such as a so-called box-type housing. Such a pump configuration corresponds to the configuration of Fig. 1a , but with the difference that the individual pump stages 17, 63 are located in a separate base housing 31 and can thus be handled as a unit - namely as a pump unit 11 - and inserted into an outer housing in order to form an independent split-flow vacuum pump.

[0075] An example of a split-flow vacuum pump 13 according to the pump configuration in Fig. 1a is in Fig. 2 shown.

[0076] The outer casing 41 of the vacuum pump 13, designed as a box-type casing, has in this example two radial taps 43. A base part 61 of the vacuum pump 13 closes the outer casing 41 at one end face. A rotor 65 (see lower illustration in Fig. 2 ) of a pump unit 11 is rotatably mounted by means of a rolling bearing. At its other end, the rotor 65 is rotatably mounted by means of a magnetic bearing. The pump unit 11 comprises a Holweck pump stage 17 and two turbomolecular pump stages 63 arranged at an axial distance from one another. One of the radial taps 43 is located - relative to the rotational axis 19 of the rotor 65 - between the two turbomolecular pump stages 63.

[0077] The stator parts of the individual pump stages that do not rotate during operation include stator blades 67 of the turbomolecular pump stages 63, a stator section 69 arranged between the two turbomolecular pump stages 63, and Holweck stators 23, 23a. The outer, radially outermost Holweck stator 23, as well as the stator blades 67 and the stator section 69, rest against the inside of the outer housing 41. Between the two Holweck stators 23, 23a and radially inside the inner Holweck stator 23a, there is a Holweck sleeve 21, 21a each, which is attached to a Holweck hub 20, which in turn is connected to the rotor 65.

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

[0079] The Holweck stators 23, 23a are provided with a structure of Holweck webs 25 on each side facing a respective Holweck sleeve 21, 21a, in order to form a respective pump-active region. Such an arrangement, as shown below in Fig. 2 and which comprises two radially nested Holweck sleeves 21, 21a with associated Holweck stators 23, 23a, is also referred to as a nested Holweck arrangement.

[0080] Fig. 2 serves to explain the structure of a possible example of a conventional split-flow vacuum pump and is not according to the invention, since no radial tapping is provided in the outer housing 41 for the Holweck pumping stage 17 and the Holweck pumping stage 17 is not designed according to the invention. Apart from that, a pump unit 11 according to the invention and thus a split-flow vacuum pump according to the invention can be designed as shown in Fig. 2 is shown.

[0081] Accordingly, Fig. 3 an example of a conventional cartridge vacuum pump, in which the Holweck pumping stage 17 is not designed according to the invention, but otherwise a pump unit 11 according to the invention can have a structure as shown in Fig. 3 is shown.

[0082] According to Fig. 3 The cartridge vacuum pump represents a pumping unit 11 which not only - corresponding to the pumping unit 11 according to Fig. 2 - a common rotor 65 with a Holweck pump stage 17 and two turbomolecular pump stages 63, but also a base housing 31 accommodating the rotor 65 and these pump stages 17, 63. The base housing 31 is closed at one end by a base part 61, in which, among other things, the rotor 65 is rotatably mounted by means of a rolling bearing. At its other end, the rotor 65 is rotatably mounted by means of a magnetic bearing.

[0083] According to the schematic representation in Fig. 1b The base housing 31 is provided with an axial suction opening 37 and two radial suction openings 33. One radial suction opening 33 is located—relative to the rotational axis 19 of the rotor 65—between the two turbomolecular pump stages 63. The other radial suction opening 33 is located axially at the level of the Holweck pump stage 17.

[0084] During pumping operation, the rotor blades 68 of the turbomolecular pump stages 63 and the Holweck hub 20 with the attached Holweck sleeves 21, 21a rotate together with the rotor 65. The stationary components of these pump stages 17, 63 are the stator blades 67 of the turbomolecular pump stages 63 and the Holweck stators 23, 23a of the Holweck pump stage 17.

[0085] The Fig. 4 and 5aeach show a part of a vacuum pump 13 according to the invention, which is designed as a cartridge vacuum pump. Apart from the region of the Holweck pumping stage designed according to the invention, which is described in more detail below, this cartridge vacuum pump 13 can have a structure as described above in connection with Fig. 3 has been explained.

[0086] Fig. 4 shows in the upper illustration a perspective view of a section made slightly above the base part 61 perpendicular to the rotational axis 19 of the rotor, whereby the lower illustration in Fig. 4 a plan view of the part of the vacuum pump 13 shown in the upper illustration.

[0087] In Fig. 4 Only the outer pumping-active region of the Holweck pumping stage is shown, 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 helically extending Holweck webs 25 on its side facing this rotor sleeve 21. This structure of a Holweck pumping region is basically known.

[0088] A special feature compared to known Holweck pump stages is that the Holweck stator 23 has an inflow area 26 of great openness. This is because the inflow area 26 comprises several, in this embodiment, three, radial inflow openings 27, which are distributed in the circumferential direction and separated from one another by support sections 29 extending in the axial direction. The support sections 29 are comparatively narrow, thus having a small circumferential length compared to the inflow openings 27.

[0089] The base housing 31 has a corresponding structure. In this axial region of the vacuum pump 13, i.e., axially at the level of the inflow area 26 of the Holweck stator 23, the base housing 31 is also provided with three suction openings 33. Two suction openings 33 arranged consecutively in the circumferential direction are separated from each other by a retaining section 39 extending in the axial direction.

[0090] The support sections 29 of the Holweck stator 23 on the one hand and the holding sections 39 of the base housing 31 on the other hand are offset from one another in the circumferential direction, in such a way that in each case a support section 29 is arranged approximately centrally between two holding sections 39 in the circumferential direction.

[0091] Furthermore, a radial gap 35 is present between the support sections 29 and the holding sections 39, which results from the fact that the radial outer sides of the support sections 29 lie on a cylinder around the axis of rotation 19, the radius of which is smaller than a cylinder around the axis of rotation 19, on which the radial inner sides of the holding sections 39 lie, which each have a reduced radial thickness compared to the axially adjacent regions of the base housing 31, i.e. they spring back radially outwards.

[0092] Due to this construction, the vacuum pump 13 has an open structure axially at the level of the Holweck pump stage 17 over its entire circumference, which is only interrupted by the comparatively narrow support sections 29 of the Holweck stator 23 and the comparatively narrow holding sections 39 of the base housing 33.

[0093] Like the side view of the Fig. 5a As shown, the radial suction openings 33 of the base housing 31 have a greater axial height than the radial inlet openings 27 of the Holweck stator 23. However, both the suction openings 33 and the inlet openings 27 each have an elongated shape, i.e., the circumferential length of each opening 33, 27 is a multiple of their respective axial height. Furthermore, the support sections 29 and the holding sections 39 are each comparatively narrow, i.e., the circumferential length of each opening 33, 27 is a multiple of the circumferential length of a respective support section 29 or holding section 39.

[0094] How Fig. 5a As further shown, the support sections 29 and the holding sections 39 do not each have a constant width over their axial length, but rather they widen in the direction of the axially adjacent regions of the base housing 31 or the Holweck stator 23.

[0095] The specific shape, width and radial thickness of the support sections 29 or holding sections 39 is selected in particular such that sufficient mechanical stability is provided, which ensures a sufficient supporting effect and optimal vibration behavior.

[0096] In Fig. 5a The Holweck sleeve 21, which cooperates with the Holweck stator 23 in a pumping manner, is shown through the radial suction openings 33 of the base housing 31 and the radial inflow openings 27 of the Holweck stator 23.

[0097] Holweckstege, on the other hand, are in Fig. 5a This is because the Holweck stator 23 is Fig. 5a according to the example in Fig. 5c is designed such that the Holweck webs 25 are interrupted in the inflow region 26, so that the radial inflow openings 27 of the Holweck stator 23 and also its support sections 29 are free of Holweck webs 25 in this region. However, such a design is not mandatory. Fig. 5b shows an alternative embodiment in which the Holweck webs 25 are not interrupted in the inflow area 26. In the embodiment according to Fig. 5a und 5c results in a difference compared to the design in Fig. 5b even more open design of the inflow area 26.

[0098] Although a cartridge vacuum pump 13 according to Fig. 3 and also according to the Fig. 4 As already mentioned, such a cartridge vacuum pump is fundamentally functional in its own right, such a cartridge vacuum pump is, in practice, inserted into an outer housing. This outer housing has a radial tap in the inflow area 26 of the Holweck stator 23 and thus in the suction area formed by the radial suction openings 33 of the base housing 31, through which a gas to be pumped can pass from a respective recipient into the Holweck pumping stage.

[0099] In order to be able to use the entire circumference of the Holweck pumping stage for the inflow of the gas to be pumped, so that the gas can reach the pump-active area between the Holweck stator 23 and the Holweck sleeve 21 via all radial inflow openings 27 distributed in the circumferential direction, the above-explained and in Fig. 4 and Fig. 5a shown radial gap 35 is provided between Holweck stator 23 and base housing 31.

[0100] An additional measure that further promotes the distribution of an inlet flow in the circumferential direction is shown schematically using the example of a cartridge vacuum pump in Fig. 7b This measure concerns the area between the base housing 31 and the outer housing 41. In this area, further measures are also possible, which are also applicable to a pump unit 11 without its own base housing, i.e. in a configuration according to Fig. 1a , can be applied. Therefore, these measures will be described below based on the Fig. 6a, 6b und 6c explained using a split-flow vacuum pump 13 shown only schematically in a section perpendicular to the axis of rotation 19.

[0101] Fig. 6a shows a configuration in which the pump unit does not have its own base housing, but is housed in an outer housing 41, which has a radial tap 43 in the area of ​​the Holweck pump stage shown here. 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 its side facing the Holweck sleeve 21, the Holweck stator 23 is provided with Holweck webs 25.

[0102] In the illustrated inflow area, the Holweck stator 23 has three radial inflow openings 27 distributed in the circumferential direction, which are separated from one another by support sections 29.

[0103] The outer sides of the support sections 29 and the inner side of the outer housing 41 lie on a common cylinder around the rotation axis 19.

[0104] To ensure that gas flowing in via the radial tap 43 can reach the pump-active region between the Holweck stator 23 and the Holweck sleeve 21 over the entire circumference, i.e., via all three radial inlet openings 27, the outer housing 41 is provided with a recess 47 on its inner side in the region of each support section 29. This allows a flow entering via the radial tap 43 to pass radially outward past the support sections 29 and then enter the pump-active region via the next radial inlet opening 27.

[0105] The recesses 47 can extend over the entire axial height of the inflow area of ​​the Holweck stator 23 formed by the radial inflow openings 27. A smaller or larger axial extension of the recesses 47 is also possible. The profile of the recesses 47, i.e., their circumferential extension, can, in principle, be designed as desired. The simplest and most cost-effective manufacturing and optimal flow guidance can be relevant criteria for the design of these recesses 47.

[0106] When configuring according to Fig. 6b there are no recesses 47 according to Fig. 6a provided. In order to nevertheless achieve a distribution of an inlet flow in the circumferential direction, the support sections 29 are provided with a reduced radial thickness, i.e. they are radially set back from the axially adjacent sections 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 formed by the outside of the support sections 29, and thus a radial gap between the outer housing 41 and the Holweck stator 23. Via this annular gap formed by the channel 24, a distribution of an inflowing gas in the circumferential direction can be achieved. For such a configuration, machining of the inside of the outer housing 41 is not necessary.

[0107] As an alternative to the measure under Fig. 6b A circumferential annular gap can be created by Fig. 6c a circumferential channel 45 is formed on the inside of the outer housing 41. A reduction in the radial thickness of the support sections 29 is not necessary with this measure.

[0108] Both the one in connection with Fig. 6b mentioned channel 24 as well as channel 55 according to Fig. 6c can extend over the entire axial height of the inflow area of ​​the Holweck stator 23 formed by the inflow openings 27. A smaller or larger axial extension of the channel 24 or 55 is also possible.

[0109] Combinations of the above-mentioned Fig. 6a, 6b und 6c Any of the measures explained are possible. In addition to a radial reduction of the support sections 29, for example, recesses 47 according to Fig. 6a Furthermore, in addition to a channel 24 according to Fig. 6b a circumferential channel 45 on the inside of the outer casing 41 according to Fig. 6c be provided, ie the annular gap between the Holweck stator 23 and the outer housing 41 can be formed jointly 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, the Fig. 7a und 7b each a configuration with a cartridge-type pump unit having its own base housing 31 and inserted into an outer housing 41 having a radial tap 43 axially in the region of the inflow area of ​​the Holweck stator 23 formed by the inflow openings 27.

[0111] The design of this cartridge vacuum pump in the inlet area corresponds to the structure of the Fig. 4 and 5a and 5c. According to the illustrations in Fig. 6a, 6b und 6c The radially outer Holweck pumping area is shown with the outer Holweck stator 23 and the Holweck sleeve 21 associated with it. The Holweck stator 23 has three radial inlet openings 27 distributed in the circumferential direction, and the base housing 31 has three radial suction openings 33 distributed in the circumferential direction, which are offset in the circumferential direction relative to the inlet openings 27 of the Holweck stator 23. The inlet openings 27 of the Holweck stator 23 are separated by comparatively narrow support sections 29, while holding sections 39 of the base housing 31 each separate two circumferentially successive radial suction openings 33 of the base housing 31 from one another.

[0112] The holding sections 39 of the base housing 33 rest with their outer sides against the inner side of the outer housing 41. Nevertheless, gas flowing in via the radial tapping 43 of the outer housing 41 can be distributed in the circumferential direction, since flow paths leading to all three radial inlet openings 27 of the Holweck stator 23 are present. The distribution is facilitated by the already Fig. 4 and 5a explained radial gap 35 between Holweck stator 23 and base housing 31, which is created by a reduction in the radial thickness of the holding sections 39, i.e. by the fact that these spring back radially outwards compared to axially adjacent areas of the base housing 31.

[0113] This openness of the overall structure with several radial inlet openings 27 of the Holweck stator 23 and several radial suction openings 33 of the base housing 31 already ensures an increase in the suction capacity compared to known designs.

[0114] A further improvement in the absorbency can be achieved if, according to Fig. 7b according to the already based on Fig. 6c In the embodiment explained above, a circumferential channel 45 is formed on the inside of the outer housing 41, creating a radial gap between the base housing 31 and the outer housing 41, through which a gas flowing in through the radial tapping 43 can be distributed in the circumferential direction. The radial gap 45 allows gas to flow radially outward past the holding sections 39 of the base housing 31.

[0115] With regard to possible additional or alternative embodiments of the embodiments according to Fig. 7a und 7b will also refer to the above in connection with Fig. 4 , Fig. 5a, 5b und 5c as well as Fig. 6a, 6b und 6c For example, in the configuration according to Fig. 7a on the inside of the outer casing 41 recesses corresponding to the recesses 47 according to Fig. 6a be provided in order to allow a flow around the holding sections 39.

[0116] The Fig. 8a und 8b each partially show a split-flow vacuum pump 13 in a section parallel to the rotation axis, wherein only the radially outer Holweck stator 23 of the Holweck pump stage is shown, which is arranged in an outer housing 41 designed as a box-type housing, which is provided with radial taps 43. The Fig. 8a und 8b serve, among other things, to illustrate different courses of the radial inlet openings 27 of the Holweck stator 23, as already mentioned elsewhere.

[0117] Accordingly Fig. 5c Here, the Holweck webs 25 are interrupted in the inflow area of ​​the Holweck stator 23, so that the radial inflow openings 27 of the Holweck stator 23 and also its support sections 29 are free of Holweck webs 25 in this area.

[0118] Accordingly Fig. 6c Here, a circumferential channel 45 is formed on the inside of the outer housing 41 in order to achieve a distribution of an input flow entering through the radial tap 43 in the circumferential direction.

[0119] The two versions of the Fig. 8a und 8b differ in that according to Fig. 8a the radial inlet openings 27 lie on a circle around the rotation axis 19, the radius of which is perpendicular to the rotation axis 19, while according to Fig. 8b The radial inlet openings 27 are arranged on a helix around the rotational axis 19, wherein the direction of rotation of the helix is ​​opposite to that of the Holweck webs 25. The direction of rotation of the helix and the direction of rotation of the Holweck webs 25 can alternatively also be the same. Alternatively, the radial inlet openings can also be arranged in a plane inclined relative to the rotational axis 19. The channel 45 on the inside of the outer housing 41 follows the course of the inlet openings 27, and in these embodiments is accordingly arranged on a circle around the rotational axis 19 ( Fig. 8a ) or on a helix around the axis of rotation ( Fig. 8b ).

[0120] Both courses - i.e. on a circle according to Fig. 8a and on a helix according to Fig. 8b - can also be provided with a Holweck stator 23, in which Fig. 5b the Holweckstege 25 are not interrupted. Bezugszeichenliste

[0121] 11 Pump unit 13 Vacuum pump 15 Vacuum system 17 Holweck pump stage 19 Rotation axis 20 Holweck hub 21 Holweck sleeve 21a Holweck sleeve 23 Holweck stator 23a Holweck sleeve 24 Channel 25 Holweck web 26 Inflow area 27 Radial inflow opening of the Holweck stator 29 Support section of the Holweck stator 31 Base housing 33 Radial suction opening of the base housing 35 Radial gap 36 Channel 37 Axial suction opening of the base housing 39 Holding section of the base housing 41 Outer casing, pump casing 43 Radial tapping 45 Channel 47 Recess 51 Vacuum chamber 53 Recipient 54 Opening 55 Radial gap 61 Base part 63 Turbomolecular pump stage 65 Rotor 67 Stator blade 68 Rotor blade 69Stator section

Claims

1. Pump unit (11) for a vacuum pump (13), in particular a turbomolecular vacuum pump, or for a vacuum system (15), with - at least one Holweck pumping stage (17) which comprises one or more Holweck sleeves (21) rotating about an axis of rotation (19) during pumping operation, and one or more Holweck stators (23), each having at least one Holweck web (25) on a side facing a Holweck sleeve (21), wherein the Holweck stator or - in the case of several Holweck stators - the outer, radially outermost Holweck stator (23) comprises in an inflow region (26) a plurality of, in particular two, three or four, radial inflow openings (27) which are arranged distributed in the circumferential direction and separated from one another by support sections (29) running in the axial direction, and wherein the support sections (29) are each designed as a web or strut.

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

3. Pump unit according to claim 1 or 2, wherein the radial inflow openings (27) are located on a circle around the axis of rotation (19) or in a plane inclined relative to the axis of rotation or on a curve extending around the axis of rotation (19) with a gradient different from zero, in particular on a helix.

4. Pump unit according to one of the preceding claims, in particular wherein the support sections (29) each extend in the circumferential direction over an angle in the range from 3° to 30°, in particular from 5° to 20°, in particular over an angle of 10°.

5. Pump unit according to one of the preceding claims, wherein the radial inflow openings (27) and / or the support sections (29) are at least partially free of Holweck webs.

6. Pump unit according to one of the preceding claims, wherein the Holweck pumping stage (17) is surrounded by a base housing (31) which has at least one radial suction opening (33) axially at the level of the inflow area (26) of the Holweck stator (23).

7. Pump unit according to claim 6, wherein a radial gap (35) extending around the rotational axis (19) is formed axially at the level of the inflow region (26) of the Holweck stator (23) between the Holweck stator (23) and the base housing (31).

8. Pump unit according to claim 6 or 7, wherein the base housing (31) comprises, axially at the level of the inflow region (26) of the Holweck stator (23), a plurality of, in particular two, three or four, radial suction openings (33) arranged distributed in the circumferential direction and separated from one another by holding sections (39) extending in the axial direction.

9. Pump unit according to one of claims 6 to 8, wherein the number of radial inflow openings (27) of the Holweck stator (23) is equal to the number of radial suction openings (33) of the base housing (31), and / or wherein the support sections (29) of the Holweck stator (23) and the holding sections (39) of the base housing (31) are offset from one another in the circumferential direction.

10. Pump unit according to one of claims 6 to 9, wherein the radial suction openings (33) of the base housing (31) each have an elongated shape and extend around the axis of rotation (19), and / or wherein the radial suction openings (33) of the base housing (31) lie on a circle around the axis of rotation (19) or in a plane inclined with respect to the axis of rotation or on a curve running around the axis of rotation (19) with a gradient other than zero, in particular on a helix, and / or wherein the holding sections (39) of the base housing (31) are each designed as a web or strut, in particular wherein the holding sections (39) each extend in the circumferential direction over an angle in the range from 3° to 30°, in particular from 5° to 20°, in particular over an angle of 10°.

11. Vacuum pump (13), in particular a turbomolecular vacuum pump, with at least one pump unit (11) according to one of the preceding claims and with an outer housing (41) in which the pump unit (11) is accommodated, wherein the outer housing (41) has a radial tap (43) axially at the level of the inflow area (26) of the Holweck stator (23) of the pump unit (11).

12. Vacuum system (15) with at least one vacuum chamber (51), at least one pump unit (11) according to one of claims 1 to 10, and at least one recipient (53) to be evacuated, wherein the vacuum chamber (51) comprises a chamber housing as an outer housing (41) into which the pump unit (11) is accommodated and which has a radial tap (43) axially at the level of the inflow area (26) of the Holweck stator (23) of the pump unit (11), which is in flow connection with the recipient (53).

13. Vacuum pump (13) according to claim 11 or vacuum system (15) according to claim 12, wherein between the outer housing (41) on the one hand and the Holweck stator (23) or the base housing (31) on the other hand, there is a radial gap (55) running around the axis of rotation (19) axially at the level of the radial tap (43) of the outer housing (41).

14. Vacuum pump (13) or vacuum system (15) according to claim 13, wherein the radial gap (55) is formed at least partially by a channel (45) formed on the inside of the outer housing (41) and / or by a channel (24, 36) formed on the outside of the Holweck stator (23) or the base housing (31).

15. Vacuum pump (13) or vacuum system (15) according to claim 13 or 14, wherein the outer housing (41) has a recess (47) on its inner side at least in the region of one of the support sections (29) of the Holweck stator (23) or of a holding section (39) of the base housing (31), preferably in the region of each support section (29) or holding section (39).

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