EP3396171B1 - Vacuum device having a shaft seal - Google Patents

Description

The present invention relates to a vacuum device, in particular a vacuum pump, with a lubricant-free space and a lubricant-containing space and with a rotatably mounted shaft which is arranged at least in sections in the two spaces.

Many vacuum devices, such as vacuum pumps in the fore-vacuum area of a vacuum system, have bearing and gear parts that are lubricated with a lubricant. Vacuum pumps for the fore-vacuum range are, for example, single-stage or multi-stage Roots pumps, which are also known as Roots pumps or multi-stage Roots pumps, screw pumps, claw pumps, scroll pumps or rotary vane pumps.

When the vacuum device is in operation, rooms in which the lubricant is located can also be evacuated. This creates a flow of a mixture of lubricant and gas into spaces of the vacuum device in which the lubricant is not desired, for example into a suction space of a vacuum pump. If such a suction chamber is connected to a high vacuum area of a vacuum system, contamination of the high vacuum area can occur due to the flow of the mixture of lubricant and gas or the migration of the lubricant into the suction chamber of the vacuum pump. Technological processes or scientific investigations that require a lubricant-free high vacuum range can therefore be severely disrupted by the migration of the lubricant into the suction chamber of the vacuum pump.

In addition, the migration of the lubricant causes a deterioration in the lubricating properties in the areas in which the shaft of the vacuum device is supported. This will shorten the life of the vacuum device. In extreme cases, the component to be lubricated and thus the vacuum device as a whole can even fail completely.

In order to separate a space in which a lubricant is not desired in a vacuum device from a space with lubricant and to prevent the migration of the lubricant, labyrinth seals are often used. These seals have a gap between the two spaces, the length of which is deliberately increased in order to lengthen the flow path for the lubricant or for a mixture of lubricant and gas. Reliably sealing labyrinth seals therefore require considerable axial and radial installation space.

From the EP 1 273 801 A2 a vacuum device according to the preamble of claim 1, 2 or 3 is known.

the DE 10 2005 015 212 A1 describes a similar vacuum device.

It is an object of the invention to provide a vacuum device with a compact sealing device in which migration of a lubricant from a space with lubricant into a space in which the presence of a lubricant is undesirable is reliably prevented.

This object is achieved by a vacuum device with the features of claim 1 and in particular in that a sealing device is provided between a lubricant-free space and a lubricant-containing space in which a rotatably mounted shaft is arranged at least in sections, through which the Shaft passes through. The sealing device comprises a rotor element which is connected to the shaft in a rotationally fixed manner, and a first stator element which is arranged in a rotationally fixed manner between the spaces.

According to the invention, a first gap with an inlet opening which is open to the space containing the lubricant is formed between the first stator element and the rotor element. The first gap also has an outlet opening which is opposite the inlet opening and is connected to a first expansion space which has a larger cross-sectional area than the first gap and which is formed by wall sections of the rotor element and the stator element.

The first expansion space is also connected to a lubricant sump. The connection between the first expansion space and the lubricant sump can be a direct connection if the first expansion space and the lubricant sump adjoin one another, or an indirect connection in which further elements and spaces of the sealing device are between the first expansion space and the lubricant sump and possibly lubricant channels are arranged. Overall, the sealing device is thus designed to separate a lubricant that originates from the space containing the lubricant and to divert it into the lubricant sump. Consequently, the sealing device also acts as a lubricant separator.

In the sealing device of the vacuum device according to the invention, a transition from the first gap to the first expansion space is thus provided, in which the cross-sectional area preferably increases abruptly. According to Bernoulli's law, this reduces the speed of the molecules of the lubricant which pass through the first gap from the space containing a lubricant into the first expansion space. They also occur in the first expansion room local negative pressure areas during operation of the vacuum device, which lead to turbulence in the flow of the molecules of the lubricant.

The reduction in the speed of the molecules of the lubricant and the turbulence lead to a significant increase in the probability of the molecules of the lubricant impinging on wall sections of the rotor element and of the stator element which form the first expansion space. As a result, in comparison to similarly compact sealing devices from the prior art, a larger amount of lubricant is separated and fed into the lubricant sump. Conversely, the probability is considerably reduced that molecules of the lubricant will pass through the sealing device as a whole and into the lubricant-free space.

Due to the presence of the first expansion space with an enlarged cross-sectional area compared to the first gap, no extension of the first gap is required in the sealing device according to the invention in order to improve the sealing effect of the sealing device. The rotor element and the first stator element, between which the first gap and the first expansion space are located, are therefore smaller in size compared to corresponding sealing devices from the prior art.

Furthermore, the sealing device comprises a second stator element which is arranged on that side of the rotor element that faces the lubricant-free space, while the first stator element is arranged on the opposite side of the rotor element that faces the space that contains the lubricant. The rotor element is thus arranged between two stator elements which each face the lubricant-free space and the space with lubricant. With the second stator element, further gaps and expansion spaces are formed between wall sections of the rotor element and the second stator element.

The second stator element thus almost doubles the probability that a molecule of the lubricant, which enters the sealing device from the space with lubricant, hits a wall section of the rotor element or of the first or second stator element. Furthermore, the path that a molecule of the lubricant has to cover from the space with lubricant to the lubricant-free space is considerably lengthened by the second stator element. Overall, the second stator element thus additionally improves the seal between the two spaces with lubricant or without lubricant.

The first and the second stator element are structurally identical. Alternatively or additionally, the first and the second stator element are constructed and / or arranged symmetrically with respect to the rotor element. A structurally identical and / or symmetrical design of the two stator elements simplifies their manufacture and their assembly on the vacuum device.

Furthermore, the rotor element is alternatively or additionally constructed symmetrically with respect to the first and the second stator element. The rotor element thus has the same geometry both in the direction of the first and the second stator element, in particular with the constrictions or constrictions described above, between which sections of the two stator elements are located. This doubles the number of gaps and expansion spaces between the rotor element and the stator elements, which further improves the effect of the sealing device.

Advantageous embodiments of the invention are specified in the subclaims, the description and in the drawing.

According to one embodiment, a second gap is formed between the first stator element and the rotor element, the inlet opening of which coincides with the first Expansion space communicating. The second gap has an outlet opening opposite the inlet opening, which is connected to a second expansion space, which in turn has a larger cross-sectional area than the second gap and, like the first expansion space, is formed by wall sections of the rotor element and the stator element.

In this embodiment, the sealing device thus has two transitions between a gap with a smaller cross-sectional area and an expansion space with a larger cross-sectional area along the path that molecules of the lubricant travel between the space containing a lubricant and the lubricant-free space. This double transition between a gap and an expansion space and the associated reduction in the velocity of the lubricant molecules thus further increases the probability that the gas molecules will hit wall sections of the rotor element or the stator element and be diverted into the lubricant sump.

Furthermore, further gaps and expansion spaces connected to them can be formed between the first stator element and the rotor element, so that overall there is a "cascading" of successive gaps and expansion spaces between the first stator element and the rotor element. As a result, the effect of the transition between the respective columns and expansion spaces is multiplied with their number.

The rotor element preferably has an inner section through which the shaft passes in an axial direction, a central section which adjoins the inner section in a radial direction with respect to the shaft, and an outer section which joins in the radial direction adjoins the middle section. The middle section has a smaller extension in the axial direction than the inner and outer sections. With In other words, in this embodiment, the rotor element is constricted in the central section when viewed in the radial direction.

As a result of this constriction or smaller extension of the central section in the axial direction, the rotor element has an enlarged surface with which the molecules of the lubricant can come into contact. Furthermore, due to the constriction, the molecules of the lubricant are reflected on an outer surface of the inner section, so that they are deflected in the direction of an inner surface of the outer section and impinge on the inner surface of the outer section. This in turn increases the likelihood that the molecules of the lubricant will hit wall sections of the rotor element and be guided in the direction of the lubricant sump.

An inner portion of the first stator element is preferably arranged in the radial direction between the inner and outer portions of the rotor element. Wall sections of the respective inner section of the first stator element and of the rotor element form the first gap. The first stator element and the rotor element thus have an "interlocking" arrangement. This leads to a lengthening of the path for the molecules of the lubricant between the space containing the lubricant and the lubricant-free space. This in turn improves the seal between these two spaces.

The first expansion space is formed in particular by wall sections of the inner section of the first stator element and by wall sections of the inner, middle and outer sections of the rotor element. The first expansion space has, for example, three moving wall sections which are formed by the rotor element. On the one hand, the movement of the wall sections increases the turbulence in the first expansion space. On the other hand, the molecules of the lubricant as a whole preferentially move in a radial direction Direction, because due to the larger area of the outer section located further out in the axial direction compared to the inner section of the rotor element, they are more likely to impinge on the outer section of the rotor element and adhere to or be diverted from it.

The middle section of the rotor element preferably comprises an inner, a middle and an outer section, the middle section having a greater extent in the axial direction than the inner and the outer section. The middle section of the rotor element, which is constricted in comparison to the inner and outer sections of the rotor element, is thus divided into three further subsections, of which the middle subsection is widened in the axial direction compared to the two further subsections. In this embodiment, the rotor element thus has two constrictions, seen in the radial direction, which are located in the area of the inner and outer subsections of the central section.

As a result of these constrictions and a corresponding arrangement of sections of the first stator element, further gaps and expansion spaces can thus be formed between the first stator element and the rotor element. In addition, the path between the space containing the lubricant and the lubricant-free space is again lengthened by the two constrictions. The multiple gaps and expansion spaces between the first stator element and the rotor element, as well as the extension of the path between the two spaces, in turn increase the likelihood that molecules of the lubricant will hit wall sections of the first stator element or the rotor element, so that the lubricant-free space is sealed is improved over the space with lubricant.

According to a further embodiment, the first stator element has at least one axial recess within which a recess extending in the axial direction Section of the rotor element is arranged. The first stator element and the rotor element thus in turn have an "interlocking" arrangement in which the path for the molecules of the lubricant between the space with lubricant and the lubricant-free space is lengthened. This in turn improves the seal between the two spaces, since the molecules of the lubricant are more likely to hit wall sections.

The rotor element preferably has at least one constriction in a direction that is axial with respect to the shaft, in which an axial projection of the stator element is arranged in such a way that the first and second gap and the first and the second gap as well as the first and the second expansion space are formed. In this embodiment, the meshing of the rotor element and the stator element thus leads to the formation of two gaps and two expansion spaces. This gives the sealing device a compact structure in which, however, two transitions are provided between a respective gap and an expansion space. Despite the compact design, the sealing device still has the advantage described above, due to the two transitions between a respective gap and expansion space, that the probability of molecules of the lubricant hitting wall sections is increased and thereby the seal between the lubricant-free space and the space is increased Lubricant is improved.

The first stator element also preferably has at least one drain opening which is in communication with the lubricant sump. The outflow opening is arranged in particular on an outer circumference of the stator element. The first expansion space, which is formed by wall sections of both the rotor element and the stator element, is only indirectly connected to the lubricant sump in this embodiment. The lubricant is thus by means of the Drain opening canalized in the direction of the lubricant sump, in particular the rotational movement of the rotary element and the associated preferred direction of the lubricant in the radial direction is used.

The vacuum device has, in particular, a housing within which the first and / or the second stator element are arranged in a rotationally fixed manner and the rotor element is rotatably arranged. The housing also has an outflow channel for the lubricant, which is in connection with at least one outflow opening of the first and / or the second stator element and with the lubricant sump. The drainage channel of the housing thus serves to “collect” the lubricant, in particular when the first and / or the second stator element have several drainage openings.

The first and / or the second stator element and / or the rotor element preferably have inclined surfaces which are provided for guiding and / or for dripping off the lubricant. The inclined surfaces can also enlarge the expansion space or the expansion spaces between the rotor element and the two stator elements. Furthermore, the inclined surfaces can be arranged in such a way that they support the transport of the lubricant due to the rotation of the rotor element in the radial direction. In addition, an edge can be formed between an inclined surface and a straight surface, on which the lubricant drips off in a preferred direction.

Fig. 1

eine Explosionsansicht eines Abschnitts einer ersten Ausführungsform eines erfindungsgemäßen Vakuumgeräts,

Fig. 2

eine vergrößerte Perspektivansicht einer Dichtvorrichtung des Vakuumgeräts von Fig. 1,

Fig. 3A

eine Vorderansicht auf den Abschnitt des Vakuumgeräts von Fig. 1,

Fig. 3B

eine Schnittansicht entlang der in Fig. 3A dargestellten Linie,

Fig. 3C und 3D

einen vergrößerten Ausschnitt von Fig. 3B, der dort mit A bezeichnet ist,

Fig. 3E

einen vergrößerten Ausschnitt von Fig. 3D, der dort mit B bezeichnet ist,

Fig. 4A

eine Vorderansicht auf einen Abschnitt einer zweiten Ausführungsform eines erfindungsgemäßen Vakuumgeräts,

Fig. 4B

eine Schnittansicht entlang der in Fig. 4A dargestellten Linie und

Fig. 4C

einen vergrößerten Ausschnitt von Fig. 4B, der dort mit A bezeichnet ist.

The invention is explained in the following purely by way of example on the basis of possible embodiments of the invention with reference to the accompanying drawings. Show it:

Fig. 1

an exploded view of a portion of a first embodiment of a vacuum device according to the invention,

Fig. 2

FIG. 8 is an enlarged perspective view of a sealing device of the vacuum device of FIG Fig. 1 ,

Figure 3A

FIG. 3 is a front view of the portion of the vacuum device of FIG Fig. 1 ,

Figure 3B

a sectional view along the in Figure 3A shown line,

Figures 3C and 3D

an enlarged section of Figure 3B , which is designated there by A,

Figure 3E

an enlarged section of Figure 3D , which is designated there with B,

Figure 4A

a front view of a section of a second embodiment of a vacuum device according to the invention,

Figure 4B

a sectional view along the in Figure 4A shown line and

Figure 4C

an enlarged section of Figure 4B , which is labeled A there.

In Fig. 1 a section of a vacuum device is shown, which is, for example, a vacuum pump, for example a Roots pump. A shaft 13, which can be rotated about a shaft axis 14, is arranged in a housing 11 of the vacuum device. The shaft 13 is supported by a bearing 15 which is shown in Figure 3B is shown schematically and which is located in a space 17 containing a lubricant within the housing 11.

Furthermore, the shaft 13 extends through a lubricant-free space 19 which is connected to a suction chamber, not shown, of the vacuum device or the vacuum pump. When operating the vacuum device or the vacuum pump the shaft 13 is driven to rotate by means of a motor in order, for example, to convey a gas from an inlet of the vacuum device or the vacuum pump to an outlet. As a result, the pump chamber and also the lubricant-free chamber 19 are evacuated during the operation of the vacuum device or the vacuum pump. The pressure in the lubricant-free space 19 is consequently lower than in the space 17 containing the lubricant.

To seal the lubricant-free space 19 from the space 17 with lubricant, a sealing device 21 is provided through which the shaft 13 passes and which is arranged between the two spaces 17, 19. The sealing device 21 comprises a first stator element 23 and a second stator element 25, which are arranged non-rotatably in the housing 11. Furthermore, the sealing device 21 comprises a rotor element 27 which is connected to the shaft 13 in a rotationally fixed manner. The rotor element 27 is arranged in the axial direction between the first and the second stator element 23, 25 and is enclosed by these after the assembly of the sealing device 21. The first and the second stator element 23, 25 as well as the rotor element 27 are ring-shaped and are arranged centered with respect to the shaft axis 14 (cf. Figures 1 to 3B ).

The first and second stator elements 23, 25 have a plurality of drainage openings 29 for the lubricant on the outer circumference, which are dimensioned and distributed in such a way that at least one drainage opening 29 is connected to a drainage channel 31 in the housing 11. This facilitates assembly, since the relative angular position of the stator elements 23, 25 is then only of subordinate importance. Via the outflow openings 29 of the first and second stator elements 23, 25, lubricant passes from the sealing device 21 into the outflow channel 31 and further into a lubricant sump (not shown).

As in Fig. 2 , 3B and 3C As can be seen, the rotor element 27 has an inner section 33 which is connected to the shaft 13. In the area of the inner In section 33, the rotor element 27 has the greatest extent or width in an axial direction, ie parallel to the shaft axis 14. In a radial direction with respect to the shaft axis 14, the inner section 33 of the rotor element 27 is adjoined by a central section 35, in which the rotor element 27 has the smallest extension or width in the axial direction.

In addition, the rotor element 27 comprises an outer section 37 which, compared to the central section 35, in turn has a greater extension or width in the axial direction, but which is smaller than the extension of the inner section 33 in the axial direction. The outer section 37 of the rotor element 27 also has a stepped profile on the outside, i.e. viewed in the radial direction, which is formed by inclined surfaces 39 and surfaces 41 running in the radial direction.

The first and the second stator element 23, 25 each have an inner section 43 with a projection 45 on the inner circumference (cf. Figure 3C , 3D and 3E ), which extends in the axial direction and in the direction of the central section 35 of the rotor element 27. At one end facing the middle section 35 of the rotor element 27, the projection 45 of the first and second stator elements 23, 25 each has an extension 47 which extends radially outward from the projection 45 of the stator element 23, 25 . The inner section 43 of the first and the second stator element 23, 25 thus has an L-shape which comprises the projection 45 and the extension 47.

The projection 45 and the extension 47 of the respective stator element 23, 25 are thus arranged in the area of a constriction of the rotor element 27, which is formed by the central section 35 of the rotor element 27. Conversely, the outer section 37 of the rotor element 27 is also arranged in a recess 49 of the respective stator element 23, 25. After the sealing device 21 has been installed, wall sections of the rotor element 27 thus form with wall sections of the first and second stator elements 23, 25 have a labyrinth-like structure with cross-sectional areas of different sizes.

A first gap 51 is formed between the projection 45 of the first stator element 23 and the inner section 33 of the rotor element 27, which gap 51 has a small cross-sectional area and an inlet opening 53 and an outlet opening 55. The inlet opening 53 of the first gap 51 is open to the space 17 containing the lubricant, while the outlet opening 55 is connected to a first expansion space 57.

The first expansion space 57 has a larger cross-sectional area than the first gap 51. Furthermore, the first expansion space 57 is formed by a respective wall section of the inner, middle and outer sections 33, 35, 37 of the rotor element 27 and by a wall section of an inner section 43 of the first stator element 23, this wall section being formed by the projection 45 and the extension 47 is formed.

Since the pressure in the lubricant-free space 19 is lower than in the lubricant-containing space 17 during operation of the vacuum device or the vacuum pump, a mixture of a gas and lubricant enters the inlet opening 53 of the first gap 51, as shown in Figure 3E is shown. Figure 3E FIG. 8 shows an enlarged area of the rotor element 27 and the first stator element 23, which is shown in FIG Figure 3D is denoted by B.

It was recognized that there is an almost laminar flow of the mixture of gas and lubricant within the first gap 51. When molecules of the lubricant flow past walls of the first gap 51, molecules of the lubricant deposit on these walls. However, due to the almost laminar flow of the mixture of lubricant and gas, the Molecules of the lubricant that move in a central area of the first gap 51 between the walls, not on the walls. These molecules of the lubricant would consequently continue to get into the lubricant-free space 19 if the spaces 17, 19 were only connected by a gap with a constant cross-sectional area, as is customary in the prior art.

However, if the mixture of gas and lubricant emerges from the outlet opening 55 of the first gap 51 in the sealing device 21 according to the invention, its speed is reduced according to Bernoulli's law, since the cross-sectional area of the first expansion space 57 is larger than the cross-sectional area of the first gap 51. Furthermore, turbulence occurs in the first expansion space 57 due to local negative pressure areas. This leads to the fact that in the first expansion space 57 the probability of molecules of the lubricant impinging on the wall sections of the rotor element 27 or of the first stator element 23 is significantly increased compared to the first gap 51.

A second gap 59 is also formed between an inner surface of the outer section 37 of the rotor element 27 and the extension 47 on the projection 45 of the first stator element 23. An inlet opening 61 of the second gap 59 is connected to the first expansion space 57, while an outlet opening 63 of the second gap 59 is connected to a second expansion space 65. The second expansion space 65 again has a larger cross-sectional area than the second gap 59, so that the speed of the mixture of gas and lubricant is again reduced when it enters the second expansion space 65. Furthermore, turbulence also occurs in the second expansion space 65 due to local negative pressure areas.

The second expansion space 65 is formed by wall sections of the outer section 37 of the rotor element 27 and by opposing wall sections of the first stator element 23. Due to the profiled outer surface of the outer Section 37 of the rotor element 27 with surfaces 41 running in the radial direction and inclined surfaces 39, the second expansion space 65 has an inner structure with constrictions and widenings, each of which has cross-sectional areas of different sizes. As a result, the turbulence within the second expansion space 65 is additionally increased compared to the first expansion space 57. The second expansion space 65 is also adjoined by one of the outflow openings 29 of the first and second stator elements 23, 25 in the radial direction and by a further expansion space of the second stator element 25 in the axial direction.

The first and the second stator element 23, 25 are structurally identical and are only arranged on different sides of the rotor element 27. The first and the second stator element 23, 25 are also arranged symmetrically to one another with respect to the rotor element 27. How to get in Figure 3C and 3D can see, the sequence of two further expansion spaces and two further gaps is repeated between the rotor element 27 and the second stator element 25 as between the rotor element 27 and the first stator element 23, but in the reverse order. Thus, the molecules of the flow of gas and lubricant that enter the inlet opening 53 of the first gap 51 must go through a comparatively long and labyrinth-like path on the way to entering the lubricant-free space, within which several transitions between a respective gap with a small cross-sectional area and a respective expansion space with a larger cross-sectional area are arranged.

Compared to one or more gaps with a constant cross-sectional area, the probability within the sealing device 21 according to the invention is therefore significantly increased that molecules of the lubricant will strike a wall section of the rotor element 27 or the first or second stator element 23, 25. The molecules of the lubricant are also driven by the rotational movement of the rotor element 27 is accelerated outward in the radial direction. As a result, they move along the surfaces 41 running in the radial direction, along the inclined surfaces 39 of the outer section 37 of the rotor element 27 and along an inclined surface 67 of the first and second stator elements 21, 23 to the outflow opening 29 of the stator element 23, 25 and into the outflow channel 31 in the housing 11, which in turn is connected to the lubricant sump, not shown. The sealing device 21 according to the invention thus improves the separation of gas and lubricant which enter the sealing device 21 from the space 17 containing the lubricant.

In Figures 4A, 4B and 4C a second embodiment of the vacuum device according to the invention is shown. This differs from the in Figures 1 to 3E illustrated embodiment on the one hand in that the middle section 35 of the rotor element 27 is divided into three sections, namely into an inner section 71, a middle section 73 and an outer section 75 greater width than the inner and outer subsections 71, 75. Since the first and the second stator element 23, 25 have corresponding projections, a structure with a total of ten columns and ten expansion spaces is thus formed overall between the rotor element 27 and the first or second stator element 23, 25.

In addition, in contrast to the first embodiment, the expansion spaces of the second embodiment have additional inclined surfaces which are formed by corresponding wall sections of the first and second stator elements 23, 25, respectively. Due to the larger number of gaps and expansion spaces compared to the first embodiment, the probability of molecules of the lubricant hitting wall sections of the rotor element 27 or of the first or second stator element 23, 25 is further increased in the second embodiment. This will make the seal of the lubricant * Free space 19 compared to the space 17 containing the lubricant with the sealing device 21 according to the second embodiment improved again.

List of reference symbols

11

casing

13th

wave

14th

Shaft axis

15th

camp

17th

Space containing lubricant

19th

lubricant-free space

21

Sealing device

23

first stator element

25th

second stator element

27

Rotor element

29

Outflow opening of the stator element

31

Drainage channel

33

inner portion of the rotor element

35

middle section of the rotor element

37

outer portion of the rotor element

39

Inclined surface of the rotor

41

surface of the rotor extending in the radial direction

43

inner section of the stator element

45

Projection of the stator element

47

Appendix

49

Recess of the stator element

51

first gap

53

Entry opening of the first gap

55

Exit opening of the first gap

57

first expansion room

59

second gap

61

Entry opening of the second gap

63

Outlet opening of the second gap

65

second expansion space

67

Inclined surface of the stator

71

inner section

73

middle section

75

outer section

Claims (15)

1. A vacuum device, in particular a vacuum pump, comprising a lubricant-free space (19); a space (17) including a lubricant; and a rotatably supported shaft (13) which is at least sectionally arranged in the two spaces (17, 19), wherein a sealing apparatus (21), through which the shaft (13) passes, is provided between the spaces (17, 19), wherein the sealing apparatus comprises:

   a rotor element (27) which is rotationally fixedly connected to the shaft (13);

   a first stator element (23) which is rotationally fixedly arranged between the spaces (17, 19);

   wherein a first gap (51) having an inlet opening (53) is formed between the first stator element (25) and the rotor element (27), said inlet opening (53) being open toward the space (17) including the lubricant,

   wherein the first gap (51) has an outlet opening (55) disposed oppositely to the inlet opening (53), said outlet opening (55) being connected to a first expansion space (57) which has a larger cross-sectional surface than the first gap (51) and which is formed by wall sections of the rotor element (27) and of the first stator element (23), and

   wherein the first expansion space (57) is in connection with a lubricant sump,

   wherein the sealing apparatus (21) comprises a second stator element (25) which is arranged at that side of the rotor element (27) which faces the lubricant-free space (19), while the first stator element (23) is arranged at the oppositely disposed side of the rotor element (27) which faces the space (17) including a lubricant,
   characterized in that

   the first and second stator elements (23, 25) are of the same construction.
2. A vacuum device in accordance with the preamble of claim 1,
   characterized in that
   the first and second stator elements (23, 25) are designed and/or arranged symmetrically with respect to the rotor element (27).
3. A vacuum device in accordance with the preamble of claim 1,
   characterized in that
   the rotor element (27) is designed symmetrically with respect to the first and second stator elements (23, 25).
4. A vacuum device in accordance with claim 1,
   characterized in that
   the first and second stator elements (23, 25) are designed and/or arranged symmetrically with respect to the rotor element (27).
5. A vacuum device in accordance with claim 1 or claim 2,
   characterized in that
   the rotor element (27) is designed symmetrically with respect to the first and second stator elements (23, 25).
6. A vacuum device in accordance with at least one of the preceding claims,
   characterized in that
   a second gap (59), whose inlet opening (61) is in connection with the first expansion space (57), is formed between the first stator element (23) and the rotor element (27), and in that the second gap (59) has an outlet opening (63) disposed oppositely to the inlet opening (61), said outlet opening (63) being connected to a second expansion space (65) which has a larger cross-sectional surface than the second gap (59) and which is formed by wall sections of the rotor element (27) and of the first stator element (23).
7. A vacuum device in accordance with at least one of the preceding claims,
   characterized in that
   the rotor element (27) has an inner section (33) through which the shaft (13) passes in an axial direction, a central section (35) which adjoins the inner section (33) in a direction which is a radial direction with respect to the shaft (13), and an outer section (37) which adjoins the central section (35) in the radial direction, with the central section (35) having a smaller extent in the axial direction than the inner and outer sections (33, 37).
8. A vacuum device in accordance with claim 7,
   characterized in that
   an inner section (43) of the first stator element (23) is arranged between the inner and outer sections (33, 37) of the rotor element (27) in the radial direction and wall sections of the respective inner section (43) of the first stator element (23) and of the rotor element (27) form the first gap (51).
9. A vacuum device in accordance with claim 7 or claim 8,
   characterized in that
   the first expansion space (57) is formed by wall sections of the inner section (43) of the first stator element (23) and by wall sections of the inner, central and outer sections (33, 35, 37) of the rotor element (27).
10. A vacuum device in accordance with at least one of the claims 7 to 9,
    characterized in that
    the central section (35) of the rotor element (27) comprises an inner, a central and an outer part section (71, 73, 75), with the central part section (73) having a greater extent in the axial direction than the inner and outer part sections (71, 75).
11. A vacuum device in accordance with at least one of the preceding claims,
    characterized in that
    the first stator element (23) has at least one axial cut-out (49) within which a section (37) of the rotor element (27) extending in the axial direction is arranged.
12. A vacuum device in accordance with at least one of the claims 6 to 11,
    characterized in that
    the rotor element (27) has, in a direction which is an axial direction with respect to the shaft (13), at least one constriction (35) in which an axial projection (45) of the first stator element (23) is arranged such that the first and second gaps (51, 59) and the first and second expansion spaces (57, 65) are formed by the constriction (35) of the rotor element (27) and by the axial projection (45) of the first stator element (23).
13. A vacuum device in accordance with at least one of the preceding claims,
    characterized in that
    the first stator element (23) has at least one outflow opening (29) which is in connection with the lubricant sump and which is in particular arranged at an outer periphery of the stator element (23).
14. A vacuum device in accordance with at least one of the preceding claims,
    characterized by
    a housing (11) within which the first and/or second stator element (23, 25) is/are rotationally fixedly arranged and the rotor element (27) is rotatably arranged and which has an outflow passage (31) for the lubricant which is in connection with at least one outflow opening (29) of the first and/or second stator element (23, 25) and with the lubricant sump.
15. A vacuum device in accordance with at least one of the preceding claims,
    characterized in that
    the rotor element (27) and/or the first and/or second stator element (23, 25) have inclined surfaces (39, 67) which are provided for guiding and/or for dripping the lubricant.

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