Gas filtration system

Abstract

The invention relates to a gas filtration system (10) comprising an outer filter element (20) having a first filter medium (22) arranged between a first end cap (24) and a second end cap (26); and an inner filter element (30) having a second filter medium (32) arranged between the third end cap (34) and the fourth end cap (36); the first filter media (22) may be arranged around the inner filter media (32); wherein the first end cap (24), the second end cap (26), the third end cap (34) and the fourth end cap (36) are open.

Description

Technical Field

[0001] The present invention relates to a gas filtering system, comprising:

[0002] - an outer filter element having a first filter medium disposed between a first end cap and a second end cap; and

[0003] - an inner filter element having a second filter medium disposed between a third end cap and a fourth end cap;

[0004] The first filter medium may be arranged to surround the second filter medium. Background Art

[0005] Such a filter system is known from DE 10 2018 215 603 A1.

[0006] In some applications, it is necessary to filter the gas flow with the aid of two filter elements. Typically, the gas flows through a first filter element, and then the pre-filtered gas flows through a second filter element. The filter element may be arranged in a common housing. Such filter systems are, for example, used to filter the combustion air of large combustion engines such as trucks, engineering vehicles, etc. Another application is the air filtration of fuel cells.

[0007] An air filter for an internal combustion engine is known from US 2006 / 0107836 A1. The air filter comprises a circular filter element which is arranged sealingly between an unfiltered air inlet and a filtered air outlet of a housing. In addition, an adsorber element is arranged on the inner wall of the housing so that the adsorber element is arranged inside the circular filter element.

[0008] WO 2015 / 092681A1 discloses a multi-layer filter element, which comprises two layers of filter material made of pleated paper. The two layers of filter material are non-detachably held together by a sealing gasket made of plastic material, and the paper of the layers is partially incorporated into the sealing gasket.

[0009] DE 10 2017 005 797 A1 discloses a filter system having a central tube in a housing. A secondary element is arranged inside the filter element and can slide along the central tube. In a first position, the secondary element opens a fluid path through the opening region of the central tube; in a second position, the secondary element closes the fluid path through the opening region of the central tube.

[0010] DE 10 2018 215 603A1 discloses a gas filter system having a first filter element surrounding a second filter element. At a first axial end, the open end caps of the two filter elements are associated with a clean air outlet. At a second axial end, the first (external) filter element has an open end cap, and the second (internal) filter element has a closed end cap. The closed end cap of the internal filter element is arranged to close the opening in the end cap of the external filter element at the second axial end.

[0011] The object of the present invention is to facilitate the production and installation of a gas filter system having two filter elements which are adapted to be used in conjunction.

[0012] This is achieved by the use of a gas filter system according to claim 1 and a filter element according to claim 17. Advantageous embodiments are given in the dependent claims and in the description. Summary of the invention

[0013] According to the present invention, a gas filtration system is provided. The gas filtration system comprises

[0014] - an outer filter element having a first filter medium disposed between a first end cap and a second end cap; and

[0015] - an inner filter element having a second filter medium disposed between the third end cap and the fourth end cap.

[0016] The first filter medium may be arranged to surround the second filter medium. The filter medium may be hollow cylindrical or conical, preferably with a substantially circular or oval cross-section. The filter media each surround a longitudinal axis. In particular, the filter media may be arranged concentrically with a common longitudinal axis. Directions such as radial or axial indications refer to the longitudinal axis of the filter system. In principle, the first end cap and the third end cap are associated with the first axial end; the second end cap and the fourth end cap are associated with the second axial end.

[0017] During use of the gas filtration system, gas flow is typically directed first through the first filter medium of the outer filter element and then through the second filter medium of the inner filter element. Suitable sealing of the filter elements toward the housing or between the filter elements may be provided as described below.

[0018] According to the present invention, the first end cap, the second end cap, the third end cap and the fourth end cap are open. The first end cap, the second end cap, the third end cap and the fourth end cap usually have a central opening. The material required for the open end cap is less than that of the closed end cap. In addition, the open end cap can be manufactured using simpler tools. The installation of the filter element is also facilitated by using the open end cap. In particular, the outer filter element can be extended from one axial end, while the inner filter element is inserted from the other axial end. In addition, the open end cap allows for visual inspection of the interior of the filter element before and during installation.

[0019] Preferably, the first end cap of the outer filter element and the third end cap of the inner filter element seal against each other. The first end cap may have a (second) sealing section for sealingly abutting against the third end cap, preferably in a radial direction. Alternatively, the third end cap may have a (second) sealing section for sealingly abutting against the first end cap, preferably in a radial direction. The second sealing section may be an integral part of the first end cap or the third end cap, respectively.

[0020] Generally speaking, the sealing section described within the context of the present invention is softer than the counterpart it should seal against. In particular, the respective sealing section can be made of polyurethane, preferably polyurethane foam. The respective counterpart can be made of rigid plastic.

[0021] Preferably, the second end cap of the outer filter element and the fourth end cap of the inner filter element seal against each other. The second end cap may have a (fourth) sealing section for sealingly abutting against the fourth end cap, preferably in a radial direction. Alternatively, the fourth end cap may have a (fourth) sealing section for sealingly abutting against the second end cap, preferably in a radial direction. The fourth sealing section may be an integral part of the second end cap or the fourth end cap, respectively.

[0022] The first end cap of the outer filter element may have a first sealing section for sealing abutment against the housing, preferably in an axial direction. Alternatively or additionally, the first sealing section may provide a radial sealing abutment against the housing. The first sealing section may be an integral part of the first end cap.

[0023] The third end cap of the inner filter element may have a third sealing section for sealing abutment against the housing, preferably in axial direction. Alternatively or additionally, the third sealing section may provide radial sealing abutment against the housing. The third sealing section may be an integral part of the third end cap.

[0024] Preferably, the gas filtration system further comprises a housing in which the internal filter element and the external filter element can be arranged. In an installed state, the filter element is arranged inside the housing. Typically, the housing comprises a first housing portion associated with the first end and a second housing portion associated with the second end. An inlet can be formed at the first housing portion or the second housing portion. Preferably, an outlet is formed at the first housing portion. The outlet can be in fluid communication with the clean side inside the internal filter element.

[0025] The housing may have a central tube, which, in the installed state of the filter system, extends into the inner filter element at the third end cap. The central tube provides guidance for the inner filter element and provides support for the second filter medium.

[0026] The housing may have a dome. Preferably, the dome protrudes into the central tube. In other words, the dome and the central tube may overlap each other in the axial direction. The dome may provide guidance during installation. With this design, undesired movement of the filter element during operation may be effectively reduced. In the event of severe vibrations, the central tube may bear against the dome in order to limit the vibration movement of the filter element.

[0027] The central tube can be held at the axial collar of the housing. This is advantageous for manufacturing the filter housing. A snap fit can be provided between the collar and the central tube.

[0028] The third end cap can be sealed against the collar or the central tube. In particular, the third sealing section of the third end cap can be sealingly adjacent to the collar or the central tube, in particular in radial direction. In this way, the interior of the inner filter element can be conveniently sealed toward the housing.

[0029] The central tube may have a closed bottom surface. This allows the central tube to be used to seal the filter element at the second end.

[0030] The fourth end cap may seal against the central tube. In particular, the fourth end cap may have a fifth sealing section for sealingly abutting against the central tube, preferably in radial direction. The fifth sealing section may be an integral part of the fourth end cap.

[0031] The second end cap may seal against the center pipe. In particular, the second end cap may have a sixth sealing section for sealing abutment against the center pipe, preferably in radial direction. The sixth sealing section may be an integral part of the fourth end cap.

[0032] Preferably, the outer filter element has a support tube. The support tube may have an end face facing radially inwards, which is embedded in the second end cap. The end face of the support tube reinforces the second end cap. Thereby, the sealing of the second end cap against the central tube is promoted.

[0033] The housing may have a first skirt that projects between the second end cap and the fourth end cap. The first skirt provides guidance and support for the filter element at the second end. The first skirt may present a radially outwardly facing sealing surface and / or a radially inwardly facing sealing surface.

[0034] The second end cap may seal against the first skirt. In particular, the second end cap may have a seventh sealing section for sealing abutment against the first skirt, preferably in radial direction. The seventh sealing section may be an integral part of the second end cap.

[0035] The fourth end cap may seal against the first skirt. In particular, the fourth end cap may have an eighth sealing section for sealing abutment against the first skirt, preferably in radial direction. The eighth sealing section may be an integral part of the fourth end cap.

[0036] The housing may have a second skirt that projects into the internal filter element at the fourth end cap. The second skirt provides guidance and support for the internal filter element at the second end. The second skirt may present a sealing surface that faces radially outward. The second skirt and the center tube may overlap each other in the axial direction. In particular, the center tube may extend into the second skirt.

[0037] The fourth end cap may seal against the second skirt. In particular, the fourth end cap may have a ninth sealing section for sealing abutment against the second skirt, preferably in radial direction. The ninth sealing section may be an integral part of the fourth end cap.

[0038] The first skirt or the second skirt is usually formed at the second housing part. The radial sealing of the second end cap and / or the fourth end cap against the first skirt and / or the second skirt can make the filter element attached to the second housing part when the housing is opened. In this way, the filter element can be easily removed and replaced. In order to install, the filter element can be kept at the first skirt and / or the second skirt. Therefore, the common installation of the filter element and the second housing part is realized.

[0039] The first filter medium or the second filter medium, in particular the second filter medium of the inner filter element, may have gas adsorption properties and preferably contain activated carbon. Typical harmful gases are SO 2 、NO x and NH 3 .

[0040] The first filter medium or the second filter medium, in particular the first filter medium of the outer filter element, can be made of cellulose.

[0041] The first filter medium and / or the second filter medium may be pleated.

[0042] The end cap with at least one sealing section may be made of polyurethane, in particular polyurethane foam.Preferably, the end cap with at least one sealing section is integral with its sealing section.

[0043] The end caps against which the sealing sections should abut may be made of rigid plastic.The rigid plastic end caps may be glued to the respective filter media.

[0044] As mentioned above, the invention also relates to the use of an external filter element and / or an internal filter element in a gas filter system according to the invention. The gas filter system can be used for cathode air filtration of a fuel cell in an electric vehicle. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] Other advantages and features of the invention will be apparent from the following description of embodiments of the invention, with reference to the accompanying drawings showing important details and according to the claims. In variations of the invention, the individual features as described above or explained below may be implemented individually or together in any useful combination.

[0046] Figure 1 A first embodiment of a gas filter system according to the invention is shown in a schematic cross-sectional view, the gas filter system comprising an outer filter element, an inner filter element and a housing;

[0047] Figure 2 Shown in a schematic cross-sectional view Figure 1 External filter elements of gas filtration systems;

[0048] Figure 3 Shown in a schematic cross-sectional view Figure 1 Internal filter elements of the gas filtration system;

[0049] Figure 4 Shown in enlarged view Figure 1 a first end of a filtration system;

[0050] Figure 5 Shown in enlarged view Figure 1 a second end of the filtration system;

[0051] Figure 6 A second end portion of a second embodiment of a filter system according to the invention is shown in a schematic cross-sectional view;

[0052] Figure 7 A first end portion of a third embodiment of a filter system according to the invention is shown in a schematic cross-sectional view;

[0053] Figure 8 A first end portion of a fourth embodiment of a filter system according to the invention is shown in a schematic cross-sectional view;

[0054] Fig. 9 A second end portion of a fourth embodiment of a filter system according to the invention is shown in a schematic cross-sectional view;

[0055] Fig.10 A first end portion of a fifth embodiment of a filter system according to the invention is shown in a schematic cross-sectional view;

[0056] Fig.11 A second end portion of a fifth embodiment of a filter system according to the invention is shown in a schematic cross-sectional view;

[0057] Fig.12 A second end portion of a sixth exemplary embodiment of a filter system according to the invention is shown in a schematic sectional view. DETAILED DESCRIPTION

[0058] Figure 1 A gas filtering system 10 is shown. The filtering system 10 comprises a housing 12. The housing has a first housing part 14 and a second housing part 16, which can be attached to each other. An inlet 18 allows gas to enter the housing 12. Here, the inlet is formed at the first housing part 14. An outlet 19 for filtered gas is also formed at the first housing part 14. The housing parts 14, 16 can be made of metal and / or rigid plastic.

[0059] The filter system 10 also includes an external filter element 20, see also Figure 2 The outer filter element 20 includes a first filter medium 22. The first medium 22 is contained between a first end cap 24 and a second end cap 26. The first filter medium 22 surrounds a longitudinal axis 28 in a circular manner. The first filter medium 22 may be made of pleated cellulose paper.

[0060] The filter system 10 also includes an internal filter element 30, see also Figure 3 The inner filter element 30 includes a second filter media 32. The second media 32 is contained between a third end cap 34 and a fourth end cap 36. The second filter media 32 also circularly surrounds the longitudinal axis 28. The second filter media 32 may include activated carbon to achieve gas adsorption properties.

[0061] The inner filter element 30 is arranged inside the outer filter element 20. Both filter elements 20, 30 are arranged inside the housing 12. Here, the first filter medium 22 and the second filter medium 32 are concentric with each other and with the longitudinal axis 28.

[0062] At the first end of the filter system 10, the first end cap 24 is arranged to surround the third end cap 34, see also Figure 4 The first end cap 24 and the third end cap 34 each have a central opening, see also Figure 2 and Figure 3The outlet 19 is in fluid communication with the clean side 40 within the inner filter element 30, see Figure 1 .

[0063] The first sealing section 42 protrudes axially from the first end cap 24. The first sealing section 42 sealingly adjoins the first housing part 14 in the axial direction. Here, the first end cap 24 and the first sealing section 42 are made integrally from polyurethane foam.

[0064] A third sealing section 44 protrudes axially from the third end cap 34. The third sealing section 44 sealingly abuts the first housing part 14 in the radial direction. In particular, the third sealing section 44 rests sealingly against a collar 46 which protrudes axially into the housing 12 at the outlet 19. Here, the third end cap 34 and the third sealing section 44 are made integrally from polyurethane foam.

[0065] At the second end of the filter system 10, the second end cap 26 is arranged to surround the fourth end cap 36, see also Figure 5 The second end cap 26 and the fourth end cap 36 each have a central opening, see also Figure 2 and Figure 3 .

[0066] The second end cap 26 and the fourth end cap 36 seal against each other. In the illustrated embodiment, a radial seal is established. The fourth end cap 36 has a fourth sealing section 48 at its outer periphery. The fourth sealing section 48 sealingly abuts the second end cap 26 in the radial direction.

[0067] The second end cap 26 may be made of a rigid plastic and is preferably glued to the first filter medium 22. The second housing portion 16 may have a bottom support protrusion 50 that abuts against the second end cap 26 in the axial direction.

[0068] The central tube 52 of the housing 12 is retained at the axial collar 46. The central tube 52 extends through the opening of the third end cap 34 and beyond the fourth end cap 36. The central tube 52 can be made of a rigid plastic. In the first embodiment, the central tube 52 has a closed bottom surface 54, see in particular Figure 1 and Figure 5 .

[0069] In the first embodiment, the fourth end cap 36 is sealed against the center tube 52. A fifth sealing section 56 is formed at the opening of the fourth end cap 36. The fifth sealing section 56 sealingly abuts the center tube 52 in the radial direction. The center tube 52 may have an annular protrusion 58, which is arranged to exceed the closed bottom surface 54, as seen from the first end with the outlet 19. At the annular protrusion 58, a radially outwardly facing sealing surface for abutting the fifth sealing section 56 is formed.

[0070] The fourth end cap 36 and the fourth sealing section 48 and the fifth sealing section 56 may be made of polyurethane foam in one piece. In other words, the fourth end cap 36 and its sealing sections 48, 56 may be a one-piece component.

[0071] The housing may have a dome 60, see Figure 1 and Figure 5 Here, the dome 60 is formed at the second housing part 16, which may be a removable cover. The dome 60 extends toward the interior of the inner filter element 30. In particular, the dome 60 extends axially into the center tube 52 at the annular protrusion 58. In other words, the center tube 52 and the dome 60 overlap each other in the axial direction. The closed bottom surface 54 of the center tube 52 is arranged slightly higher than the dome 60.

[0072] The second end cap 26 and the fourth end cap 36 can have a circular cross section. In order to install the filter element 20, 30 in a defined position in the circumferential direction, the end caps 26, 36 and the housing can have a radially directed projection-receiving portion arrangement. For example, the radially outwardly directed projection on the fourth end cap 36 can protrude into a recess in the second end cap 26. Similarly, the outwardly directed projection on the second end cap 26 can protrude into a recess in the wall of the housing, or the projection on the inner wall of the housing can protrude into a recess in the outer circumference of the second end cap 26.

[0073] A second embodiment of the gas filtration system 10 (a first end portion of which is shown in FIG. Figure 6 ) corresponds roughly to Figures 1 to 5 And the first embodiment of the gas filtration system 10 described above.

[0074] In the second embodiment, the second skirt 62 is formed at the second housing portion 16. The second skirt 62 protrudes into the inner filter element 30 at the fourth end cap 36. The center tube 52 and the second skirt 62 overlap each other in the axial direction. In particular, the center tube 52 extends into the second skirt 62 with its end section, and the diameter of the end section can be smaller than the middle section of the center tube 52.

[0075] In the second embodiment, the fourth end cap 36 is sealed against the second skirt 62. A ninth sealing section 64 is formed at the opening of the fourth end cap 36. The ninth sealing section 64 sealingly abuts the second skirt 62 in the radial direction.

[0076] A third embodiment of the gas filtration system 10 (the second end portion of which is shown in FIG. Figure 7 ) corresponds roughly to Figures 1 to 5 And the first embodiment of the gas filtration system 10 described above.

[0077] In the third embodiment, the first end cap 24 and the third end cap 34 seal against each other. Here, a radial seal is established. The third end cap 34 has a second sealing section 66. The second sealing section 66 sealingly abuts the first end cap 24 in the radial direction.

[0078] The third end cap 34 and the second sealing section 66 and the third sealing section 44 can be made of polyurethane foam in one piece. In other words, the third end cap 34 and its sealing sections 44, 66 can be a one-piece component.

[0079] The first end cap 24 may be made of a rigid plastic and is preferably glued to the first filter medium 22. The first housing portion 14 may have a top support tab 68 that bears against the first end cap 24 in the axial direction.

[0080] A fourth embodiment of the gas filtration system 10 (with its first end and second end portions shown in FIG. Figure 8 and Fig. 9 in its basic structure corresponds to Figures 1 to 5 And the first embodiment of the gas filtration system 10 described above.

[0081] In the fourth embodiment, the third end cap 34 of the inner filter element 30 seals against the center tube 52, see Figure 8 The third sealing section 44 radially delimits the opening of the third end cap 34. The third sealing section 44 sealingly abuts the center pipe 52 of the housing 12 in the radial direction. Here, the third end cap 34 and the third sealing section 44 are integrally made of polyurethane foam.

[0082] As in the first embodiment, in the fourth embodiment, the fourth end cap 36 of the inner filter element 30 is also sealed against the central tube 52 via the fifth sealing section 56, see Fig. 9 .

[0083] However, in the fourth embodiment, the first skirt 70 of the second housing portion 16 protrudes axially between the second end cap 26 and the fourth end cap 36. The second end cap 26 seals against the first skirt 70. The seventh sealing section 72 radially delimits the opening of the second end cap 26. The seventh sealing section 72 sealingly adjoins the first skirt 70 in the radial direction. Here, the second end cap 26 and the seventh sealing section 72 are made integrally of polyurethane foam.

[0084] A fifth embodiment of the gas filtration system 10 (with its first end and second end portions shown in FIG. Fig.10 and Fig.11 ) corresponds roughly to Figure 8 and Fig. 9 And the fourth embodiment of the gas filtration system 10 described above.

[0085] In the fifth embodiment, an axial seal is established between the third end cap 34 and the first housing portion 14, see Fig.10 The third sealing section 44 protrudes axially from the third end cap 34. The third sealing section 44 sealingly adjoins the first housing part 14 in the axial direction. Here, the third end cap 34 and the third sealing section 44 are made integrally from polyurethane foam.

[0086] As in the first and fourth embodiments, in the fifth embodiment, an axial seal between the first end cap 24 and the first housing portion 14 is also established via the first sealing section 42 .

[0087] As in the fourth embodiment, in the fifth embodiment, a radial seal between the second end cap 26 and the first skirt 70 is also established via the seventh sealing section 72. However, in the fifth embodiment, the fourth end cap 36 is also sealed against the first skirt 70. An eighth sealing section 74 is formed at the outer periphery of the fourth end cap 36. The eighth sealing section 74 sealingly abuts the first skirt 70 in the radial direction. Here, the fourth end cap 36 and the eighth sealing section 74 are integrally made of polyurethane foam.

[0088] Since a radial seal is established at the second end (second end cap 26 and fourth end cap 36) and an axial seal is established at the first end (first end cap 24 and third end cap 34), when the housing is opened, the filter elements 20, 30 will remain at the second housing portion 16. This facilitates maintenance of the gas filtration system and replacement of the filter elements 20, 30.

[0089] The sixth embodiment of the gas filtration system 10 (the second end portion of which is shown in FIG. Fig.12 ) corresponds roughly to Figures 1 to 5 The first embodiment of the gas filtration system 10, or see Figure 8 and Fig. 9 and the fourth embodiment described above.

[0090] As in the first or fourth embodiment, in the sixth embodiment, the radial seal between the fourth end cap 36 and the center tube 52 is also established via the fifth sealing section 56. It should be noted that the center tube 52 can also be closed circumferentially slightly above the closed bottom surface 54 for sealing abutment of the fifth sealing section 56.

[0091] In the sixth embodiment, the second end cap 26 of the outer filter element 20 is sealed against the central tube 52. The outer filter element 20 is longer (in the axial direction) than the inner filter element 30. The outer filter element 20 may include a support tube 76. Here, the support tube 76 has an end face 78, which extends radially inward at the second end cap 26. In particular, the end face 78 is embedded in the second end cap 26. The sixth sealing section 80 radially defines the opening in the second end cap 26. It should be noted that the sixth sealing section 80 is arranged radially inside the end face 78. The sixth sealing section 80 is sealingly adjacent to the central tube 52 in the radial direction. In particular, the sixth sealing section 80 can be placed against the annular protrusion 58 of the central tube 52. Here, the second end cap 26 and the sixth sealing section 80 are made of polyurethane foam in one piece.

[0092] Reference numerals

[0093] Gas filtration system 10

[0094] Housing 12

[0095] First housing part 14

[0096] Second housing part 16

[0097] Entrance 18

[0098] Exit 19

[0099] External filter element 20

[0100] First filter medium 22

[0101] First end cap 24

[0102] Second end cap 26

[0103] Longitudinal axis 28

[0104] Internal filter element 30

[0105] Second filter medium 32

[0106] The third end cap 34

[0107] Fourth end cap 36

[0108] Clean side 40

[0109] First sealing section 42

[0110] The third sealing section 44

[0111] Ring 46

[0112] Fourth sealing section 48

[0113] Bottom support protrusion 50

[0114] Center tube 52

[0115] Bottom 54

[0116] Fifth sealing section 56

[0117] Protrusion 58

[0118] Dome 60

[0119] Second skirt 62

[0120] Ninth sealing section 64

[0121] Second sealing section 66

[0122] Top support protrusion 68

[0123] First skirt 70

[0124] Seventh sealing section 72

[0125] Eighth sealing section 74

[0126] Support tube 76

[0127] End face 78

[0128] Sixth sealing section 80

Claims

1. A gas filtration system (10), comprising: - an outer filter element (20) having a first filter medium (22) arranged between a first end cap (24) and a second end cap (26); and - an inner filter element (30) having a second filter medium (32) arranged between a third end cap (34) and a fourth end cap (36); The first filter medium (22) can be arranged to surround the inner filter medium (32); in, The first end cap (24), the second end cap (26), the third end cap (34) and the fourth end cap (36) are open.

2. The gas filtration system (10) according to claim 1, wherein: The first end cap (24) of the outer filter element (20) and the third end cap (34) of the inner filter element (30) are sealed against each other.

3. The gas filtration system (10) according to claim 2, wherein: The third end cap (34) has a second sealing section (66) for sealingly abutting against the first end cap (24), preferably in a radial direction.

4. The gas filtration system (10) according to any one of the preceding claims, wherein: The second end cap (26) of the outer filter element (20) and the fourth end cap (36) of the inner filter element (30) are sealed against each other.

5. The gas filtration system (10) according to claim 4, wherein: The fourth end cap (36) has a fourth sealing section (48) for sealingly abutting against the second end cap (26), preferably in a radial direction.

6. The gas filtration system (10) according to any one of the preceding claims, wherein: The first end cap (24) of the outer filter element (20) has a first sealing section (42) for sealing abutment against the housing (12), preferably in an axial direction.

7. The gas filtration system (10) according to any one of the preceding claims, wherein: The third end cap (34) of the inner filter element (30) has a third sealing section (44) for sealing abutment against the housing (12).

8. The gas filter system (10) according to any of the preceding claims, further comprising a housing (12), in which the outer filter element (20) and the inner filter element (30) are arrangeable.

9. The gas filtration system (10) according to claim 8, wherein: The housing (12) has a center tube (52) that extends into the inner filter element (30) at the third end cap (34).

10. The gas filtration system (10) according to claim 9, wherein: The housing (12) has a dome (60) that protrudes into the center tube (52).

11. The gas filtration system (10) according to claim 9 or 10, wherein: The center tube (52) is retained at an axial collar (46) of the housing (12).

12. The gas filtration system (10) according to claim 11, wherein: The third end cap (34) seals against the collar (46) or the center tube (52).

13. The gas filtration system (10) according to any one of claims 8 to 12, wherein: The fourth end cap (36) has a fifth sealing section (56) for sealingly abutting against the center tube (52), preferably in a radial direction.

14. The gas filtration system (10) according to any one of claims 8 to 13, wherein: The second end cap (26) has a sixth sealing section (80) for sealingly abutting against the center tube (52), preferably in a radial direction.

15. The gas filtration system (10) according to claim 14, wherein: The outer filter element (20) has a support tube (76), wherein the support tube (76) has an end surface (78) facing radially inwards, which end surface (78) is embedded in the second end cap (26).

16. The gas filtration system (10) according to any one of claims 8 to 15, wherein: The housing (12) has a first skirt (70) that protrudes between the second end cap (26) and the fourth end cap (36).

17. The gas filtration system (10) according to claim 16, wherein: The second end cap (26) has a seventh sealing section (72) for sealingly abutting against the first skirt (70), preferably in a radial direction.

18. The gas filtration system (10) according to claim 16 or 17, wherein: The fourth end cap (36) has an eighth sealing section (74) for sealingly abutting against the first skirt (70), preferably in a radial direction.

19. The gas filtration system (10) according to any one of claims 8 to 18, wherein: The housing (12) has a second skirt (62) that projects into the inner filter element (30) at the fourth end cap (36).

20. The gas filtration system (10) of claim 19, wherein: The fourth end cap (36) has a ninth sealing section (64) for sealingly abutting against the second skirt (62), preferably in a radial direction.

21. Use of an outer filter element (20) and / or an inner filter element (30) in a gas filter system (10) according to any of the preceding claims.

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