Gas Filter System

Abstract

The present invention relates to a gas filter system (10) comprising an outer filter element (20) having a first filter medium (22) disposed between a first end cap (24) and a second end cap (26), and an inner filter element (30) having a second filter medium (32) disposed between a third end cap (34) and a fourth end cap (36), wherein the first, third, and fourth end caps (24, 34, 36) are open, the outer filter element (20) is closed by the second end cap (26), and the first filter medium (22) is positionable to surround the second filter medium (32) such that the outer filter element (20) is sealed to the inner filter element (30) between the second end cap (26) and the fourth end cap (36).

Description

[Technical Field]

[0001] The present invention relates to a gas filter system comprising an outer filter element having a first filter medium disposed between a first end cap and a second end cap, and an inner filter element having a second filter medium disposed between a third end cap and a fourth end cap, wherein the first filter medium can be positioned to surround the second filter medium. [Background technology]

[0002] Such a filter system is known from DE 10 2018 215 603 A1 and US Pat. No. 5,415,677.

[0003] In some applications, a gas stream must be filtered through two filter elements. Typically, the gas flows through the first filter element, followed by the pre-filtered gas flowing through the second filter element. The filter elements can be located within a common housing. This type of filter system is used, for example, to filter combustion air for large combustion engines such as trucks and construction vehicles. Another application is filtering air for fuel cells.

[0004] German Patent Application Publication No. 102018215603 discloses a gas filter system having a first filter element surrounding a second filter element. At first axial ends, the open end caps of the two filter elements are associated with a clean air outlet. At second axial ends, the first (outer) filter element has an open end cap, and the second (inner) filter element has a closed end cap. The closed end cap of the inner filter element is arranged to close the opening of the end cap of the outer filter element at the second axial end.

[0005] The filter described in U.S. Patent No. 5,415,677 includes a primary air filter element and a secondary air filter element. At their rear ends, the primary and secondary air filter elements are closed by end caps. At their front ends, the primary and secondary filter elements are provided with open end caps. Annular gaskets are disposed in the open end caps to seal the primary and secondary filter elements to the canister in which the filter elements are disposed.

[0006] SUMMARY OF THE INVENTION It is an object of the present invention to provide a gas filter system with an improved seal between two filter elements suitable for joint use.

[0007] This is achieved by the use of a gas filter system according to claim 1 and a filter element according to claim 15. Advantageous embodiments are set out in the dependent claims and the description. Summary of the Invention

[0008] According to the present invention, a gas filter system is provided, comprising an outer filter element having a first filter medium disposed between first and second end caps, and an inner filter element having a second filter medium disposed between third and fourth end caps.

[0009] The first, third, and fourth end caps are open. The first, third, and fourth end caps typically have a central opening.

[0010] The inner filter element is closed by a fourth end cap, which may be a monolithic closure end cap, or a closure means may be permanently attached to the inner filter element to seal the fourth end cap.

[0011] The first filter medium can be arranged to surround the second filter medium. The filter medium can be hollow cylindrical or conical, preferably having a circular or elliptical cross section. The filter mediums each surround a longitudinal axis. In particular, the filter mediums are arranged concentrically about a common longitudinal axis. Directions such as radial and axial refer to the longitudinal axis. As a general rule, the first and third end caps are associated with the first axial end, and the second and fourth end caps are associated with the second axial end.

[0012] During use of the gas filter system, the gas flow typically first passes through the first filter medium of the outer filter element and then through the second filter medium of the inner filter element.

[0013] According to the present invention, when the outer filter element is placed around the inner filter element for use in a gas filter system, the outer filter element is sealed to the inner filter element, preferably in the radial direction, between the second end cap and the fourth end cap. The second and fourth end caps are sealed to each other, thereby sealing the intermediate space between the first and second filter media at the second end. Thus, the gas to be filtered flows continuously through the two filter media.

[0014] The fourth end cap of the inner filter element may have a (second) seal for sealingly abutting, preferably radially, against the outer filter element. Alternatively or additionally, the second seal may provide an axial seal. The second seal may be integral with the fourth end cap. Preferably, the fourth end cap with the second seal is a monolithic foam part.

[0015] Generally, the seals described in the context of the present invention are softer than the mating parts they seal. In particular, each seal is made of polyurethane, preferably foamed polyurethane. The respective mating parts may be made of hard plastic.

[0016] The second end cap of the outer filter element may be a monolithic closed end cap, which may be constructed from a hard plastic and is preferably bonded to the first filter medium.

[0017] Alternatively, a closure means may be permanently attached to the outer filter element for sealing the second end cap. The monolithic closure end cap may be constructed from a hard plastic.

[0018] Preferably, the outer filter element includes a support tube. The support tube reinforces the outer filter element. The support tube can be partially embedded in the first and / or second end caps. The support tube can be made of a hard plastic.

[0019] Particularly preferably, the support tube has a radially inward end face that closes the outer filter element at the second end cap. In this way, the support tube serves two functions: as a reinforcing means and as a closure means. Providing a closed end face facilitates the manufacture of the second end cap, since less material is required. In particular, the second end cap can be made of polyurethane, preferably foamed polyurethane, which can be molded directly onto the first filter medium, preferably the support tube.

[0020] In the installed state, the fourth end cap may be sealed to the support tube. In particular, the second seal may sealingly abut against the support tube. The support tube may have an annular seal strip for sealingly abutting the second seal. This facilitates sealing the outer and inner filter elements between the second and fourth end caps. Preferably, the seal strip on the support tube has a radially inward-facing seal surface. The radial seal allows for slight axial displacement of the inner filter element relative to the outer filter element.

[0021] The outer filter element has an axial protrusion on the second end cap that protrudes into the inner filter element. The protrusion provides a guide between the filter elements, particularly during installation. The protrusion typically protrudes axially beyond the fourth end cap of the inner filter element. The protrusion can be formed on the end face of the monolithic second end cap or the support tube.

[0022] The first end cap of the outer filter element may have a first seal for sealingly abutting, preferably axially, against the housing. Alternatively or additionally, the first seal may provide a radial sealing abutment against the housing.

[0023] The third end cap of the inner filter element may have a third seal for sealingly abutting against the housing, preferably in a radial direction, and alternatively or additionally, the third seal may provide an axial sealing abutment against the housing.

[0024] Preferably, the gas filter system further includes a housing in which the inner and outer filter elements can be disposed. In the installed state, the filter elements are disposed within the housing. Typically, the housing includes a first housing portion associated with the first end and a second housing portion associated with the second end. The inlet may be formed in either the first or second housing portion. The outlet is preferably formed in the first housing portion. The outlet may be in fluid communication with the clean side of the inner filter element.

[0025] Preferably, the housing has a protruding dome on the protrusion, which can provide guidance during installation and, in particular, additional support for the outer filter element during use of the filter system.

[0026] The housing may have a central tube that extends into the inner filter element at the third end cap when the filter system is installed, the central tube providing a guide for the inner filter element and supporting the second filter medium.

[0027] The central tube can be held in an axial collar of the housing, which is advantageous in manufacturing the filter housing, and a snap fit may be provided between the collar and the central tube.

[0028] Preferably, the protrusion and the central tube overlap each other in the axial direction, which allows mutual guidance and support between the central tube and the outer filter element, which also facilitates installation of the filter system. In particular, the protrusion may be engaged with the central tube. In other words, the central tube may surround the protrusion radially outward.

[0029] Furthermore, the dome and the central tube may be arranged to overlap each other in the axial direction. This design effectively prevents undesired movement of the filter element during operation. In the event of large vibrations, the central tube can contact the dome via a protrusion disposed between the central tube and the dome.

[0030] At least two of the housing inner wall, the second end cap, the fourth end cap, the protrusion, the center tube, and the dome can have a protrusion / recess arrangement that provides a circumferentially defined location, for example, a radially inward protrusion on the housing wall protrudes into a recess on the outer periphery of the second end cap.

[0031] The first or second filter medium, especially the second filter medium of the inner filter element, may have gas adsorption properties and preferably comprises activated carbon. Typical harmful gases include SO2, NO X , NH3.

[0032] The first or second filter medium, particularly the first filter medium of the outer filter element, may be composed of cellulose.

[0033] The first and / or second filter media may be pleated.

[0034] The present invention also relates to the use of the outer filter element and / or the inner filter element in a gas filter system according to the invention, as described above, which can be used for cathode air filtration in fuel cells of electric vehicles.

[0035] Other advantages and features of the present invention will be apparent from the following description of embodiments of the invention, with reference to the drawings showing important details, and from the claims. The individual features as described above or below may be implemented individually or in any useful combination in variants of the invention. [Brief explanation of the drawings]

[0036] [Figure 1] 1 is a schematic cross-sectional view of a gas filter system including an outer filter element, an inner filter element, and a housing according to the present invention. [Figure 2] 2 is a schematic cross-sectional view of an outer filter element of the gas filter system of FIG. 1. [Figure 3] 2 is a schematic cross-sectional view of an inner filter element of the gas filter system of FIG. 1. [Figure 4] FIG. 2 is an enlarged view of a first end of the filter system of FIG. 1. [Figure 5] FIG. 2 is an enlarged view of a second end of the filter system of FIG. 1. DETAILED DESCRIPTION OF THE INVENTION

[0037] 1 illustrates a gas filter system 10. The filter system 10 includes a housing 12. The housing has a first housing portion 14 and a second housing portion 16 that are attachable to one another. An inlet 18 allows gas to enter the housing 12. Here, the inlet is formed in the first housing portion 14. A filtered gas outlet 19 is also formed in the first housing portion 14. The housing portions 14, 16 may be made of metal and / or rigid plastic.

[0038] The filter system 10 further includes an outer filter element 20 (see also FIG. 2). The outer filter element 20 has a first filter medium 22. The first filter medium 22 is housed between a first end cap 24 and a second end cap 26. The first filter medium 22 circumferentially surrounds a longitudinal axis 28. The first filter medium 22 may be constructed from pleated cellulose paper.

[0039] The filter system 10 further includes an inner filter element 30 (see also FIG. 3). The inner filter element 30 has a second filter medium 32. The second filter medium 32 is housed between a third end cap 34 and a fourth end cap 36. The second filter medium 32 also circumferentially surrounds the longitudinal axis 28. The second filter medium 32 may include activated carbon for gas adsorption properties.

[0040] The inner filter element 30 is disposed inside the outer filter element 20. Both filter elements 20, 30 are disposed within the housing 12, where the first and second filter media 22, 32 are concentric with each other and with respect to the longitudinal axis 28.

[0041] At the first end of the filter system 10, a first end cap 24 is positioned to surround a second filter media 32 around a third end cap 34 (see also FIG. 4). The first end cap 24 and the third end cap 34 each have a central opening (see FIGS. 2 and 3, respectively). The outlet 19 is in fluid communication with a clean side 40 within the inner filter element 30 (see FIG. 1).

[0042] The first seal portion 42 protrudes axially from the first end cap 24. The first seal portion 42 is in axial sealing contact with the first housing portion 14. Here, the first end cap 24 having the first seal portion 42 is integrally formed from foamed polyurethane.

[0043] The third seal 44 projects axially from the third end cap 34. The third seal 44 sealingly abuts radially against the first housing part 14. In particular, the third seal sealingly abuts against a collar 46 that projects axially into the housing 12 at the outlet 19. Here, the third end cap 34 and the third seal 44 are integrally formed from foamed polyurethane.

[0044] A central tube 48 of the housing 12 is retained in the axial collar 46. The central tube 48 extends through an opening in the third end cap 34 toward the fourth end cap 36. The central tube 48 may be constructed of a hard plastic.

[0045] The outer filter element includes a support tube 50 (see FIGS. 1, 2, 4, and 5). The support tube extends from the first end cap 24 to the second end cap 26, inside the first filter media 22. The support tube 50 may be constructed of a hard plastic.

[0046] The support tube 50 can be partially embedded in the first and / or second end caps 24, 26. In particular, the second end cap 26 is in sealing contact with the support tube 50. Here, the second end cap 26 is constructed from foamed polyurethane and can be molded to the first filter media 22 and the support tube 50 to provide a permanent connection.

[0047] At the second end, support tube 50 has a closed end face 52. Closed end face 52 extends radially inwardly of a central region of first filter media 22. Outer filter element 20 is thereby closed by end face 52 of support tube 50 to second end cap 26.

[0048] At a radial region within second filter medium 32, closed end surface 52 of support tube 50 defines a protrusion 54 (see FIGS. 1, 2 and 5) that extends through a central opening in fourth end cap 36 into inner filter element 30.

[0049] The central tube 48 of the housing 12 and the protrusion 54 of the inner filter element 30 overlap one another along the longitudinal axis 28. The central tube 48 may surround the protrusion 54.

[0050] The housing 12 may have a dome 56. Here, the dome 56 is formed on the second housing portion 16, which may be, for example, a removable cover. The dome 56 extends toward the inside of the inner filter element 30. In particular, the dome 56 extends into the protrusion 54 of the outer filter element 30. More particularly, the dome 56, the protrusion 54, and the central tube 48 overlap one another along the longitudinal axis 28.

[0051] The fourth end cap 36 is sealed to the outer filter element 20 (see FIGS. 1 and 5). In the illustrated embodiment, a radial seal is established. The fourth end cap 36 has a second seal 58 at its outer periphery (see also FIG. 3). The fourth end cap 36 with the second seal 58 can be integrally formed from foamed polyurethane. In other words, the fourth end cap 36 with the seal 58 can be a monolithic part.

[0052] The fourth seal portion 58 is in sealing radial contact with a seal strip 60 (see also FIG. 2) of the support tube 50. The seal strip 60 is formed at the same axial height as the second end cap 26. This allows the second end cap 26 and the fourth end cap 36 to seal against the seal strip 60 from the radially outer side and inner side, respectively. [Explanation of symbols]

[0053] Gas filter systems 10 Housing 12 First housing part 14 Second housing part 16 Inlet 18 Outlet 19 Outer filter element 20 First filter element 22 First End Cap 24 Second End Cap 26 Longitudinal axis 28 Inner filter element 30 Second filter element 32 Third End Cap 34 4th end cap 36 Clean side 40 First seal portion 42 Third seal 44 Color 46 central tube 48 Support tube 50 End face 52 Projection 54 Dome 56 Second seal part 58 Seal Strip 60

Claims

1. A gas filter system (10) comprising: an outer filter element (20) having a first filter medium (22) disposed between a first end cap (24) and a second end cap (26); an inner filter element (30) having a second filter medium (32) disposed between a third end cap (34) and a fourth end cap (36); the first, third, and fourth end caps (24, 34, 36) are open; The outer filter element (20) is closed with the second end cap (26), the first filter medium (22) is positionable to surround the second filter medium (32) such that the outer filter element (20) is sealed to the inner filter element (30) between the second end cap (26) and the fourth end cap (36); The gas filter system (10) includes an outer filter element (20) having an axial protrusion (54) on the second end cap (26), the protrusion (54) protruding into the inner filter element (30).

2. 2. The gas filter system (10) of claim 1, wherein the fourth end cap (36) has a second seal (58) for sealingly abutting against the outer filter element (20).

3. The gas filter system (10) of claim 1 or 2, wherein the second end cap (26) is a monolithic closed end cap.

4. 3. The gas filter system of claim 1, wherein the outer filter element has a support tube having a radially inward end face that closes the outer filter element at the second end cap.

5. 5. The gas filter system (10) of claim 1, wherein the first end cap (24) of the outer filter element (20) has a first seal (42) for sealingly abutting, preferably axially, against a housing (12).

6. A gas filter system (10) as claimed in any one of claims 1 to 5, wherein the third end cap (34) has a third seal portion (44) for sealingly abutting against the housing (12), preferably in a radial direction.

7. The gas filter system (10) of any one of claims 1 to 6, further comprising a housing (12) in which the inner and outer filter elements (20, 30) are positionable.

8. The gas filter system (10) of claim 7, wherein the housing (12) has a dome (56) that projects into the protrusion (54).

9. 9. The gas filter system (10) of claim 7 or 8, wherein the housing (12) has a central tube (48) that extends into the inner filter element (30) at the third end cap (34).

10. The gas filter system (10) of claim 9, wherein the protrusion (54) and the central tube (48) axially overlap one another.

11. 11. The gas filter system (10) of claim 8, wherein the dome (56) and the central tube (48) overlap one another in the axial direction.

12. The gas filter system (10) according to any one of claims 1 to 11, wherein the first or second filter medium (22, 32), in particular the second filter medium (32) of the inner filter element (30), has gas adsorption properties and preferably comprises activated carbon.

13. 13. The gas filter system (10) according to any one of claims 1 to 12, wherein the first or second filter medium (22, 32), in particular the first filter medium (22) of the outer filter element (20), is made of cellulose.

14. Use of an outer filter element and / or an inner filter element (20, 30) in a gas filter system (10) according to any one of claims 1 to 13.

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