DE102016004317A1 - Filter element and filter assembly - Google Patents

Abstract

A filter element (11), in particular a secondary filter element, which is receivable in a main filter element (3) with an engagement portion (18) adapted to engage a corresponding mating engagement portion (28) of a filter housing (2) of the filter element (11) for positively connecting the filter element (11) to the filter housing (2), the filter element (11) having an oval cross-section (33).

Description

Technical area

The present invention relates to a filter element and a filter assembly with such a filter element.

State of the art

A filter element arrangement, for example for filtering air or liquid equipment of a vehicle, may comprise a main filter element and a secondary filter element accommodated in the main filter element. The secondary filter element essentially serves to prevent contamination of a clean side of the filter element arrangement with raw fluid to be filtered when replacing the main filter element.

EP 2 227 307 B1 describes such a filter arrangement, wherein both the secondary filter element and the main filter element have a cylindrical geometry with a circular cross-section. The secondary filter element accommodated in the main filter element is screwed into a filter housing of the filter arrangement.

Disclosure of the invention

It is therefore an object of the present invention to provide an improved filter element.

Accordingly, a filter element, in particular a secondary filter element, which is receivable in a main filter element proposed. The filter element comprises an engagement portion adapted to engage a corresponding mating engagement portion of a filter housing of the filter element to positively connect the filter element to the filter housing, the filter element having an oval cross-section.

The filter element is in particular adapted to filter fluids, such as air or other gases, liquids, in particular liquid operating means of a vehicle, in particular of a motor vehicle, such as oil, water, diesel, gasoline, kerosene or urea solution. In particular, the filter element is an air filter element. The filter element is particularly suitable for filtering combustion air of an internal combustion engine, in particular for an agricultural machine, a truck or a construction machine. In this respect, the filter element in embodiments is an air filter element for combustion air of an internal combustion engine in a motor vehicle. The filter element may find application in automobiles, watercraft, rail vehicles, agricultural vehicles, construction machinery, aircraft or the like. Furthermore, the filter element can be used in immobile applications, such as in building services.

The filter element may also be referred to as a second filter element, secondary element, secondary element or secondary filter element. The main filter element may also be referred to as first filter element, primary filter element, primary element or main element. Preferably, the filter element within the main filter element can be arranged. In particular, the filter element is arranged in an installed or operating state within a volume enclosed by a filter medium of the main filter element. Preferably, a filter medium of the filter element is arranged in the installation or operating state with respect to a downstream side of the filter medium of the main filter element. In comparison to externally arranged secondary filter elements thereby an enlarged filter area and thus a lower pressure loss are achieved during flow.

As an oval cross-section - in particular transversely to the longitudinal axis of the filter element - is understood a cross-section which has a deviating from a circle perimeter and in particular is round-convex. The circumferential line preferably has a curvature without change of sign. It is conceivable z. B. an ellipse or stadium shape.

In the present case, oval can also be understood as meaning a rectangular cross section with rounded corners, an elliptical cross section or a cross section formed from a plurality of circular arcs. The cross section is preferably closed and comprises a main axis of symmetry and a side axis of symmetry positioned perpendicular to the main axis of symmetry. The cross section is z. B. constructed symmetrically. That is, the cross section is symmetrical with respect to both the main axis of symmetry and the minor axis of symmetry. A longitudinal extent of the cross section in the direction of the main axis of symmetry is preferably greater than a longitudinal extent of the cross section in the direction of the minor axis of symmetry.

Characterized in that the secondary filter element is positively connected to the filter housing, an unwanted removal of the secondary filter element is prevented from the filter housing with an exchange of the plugged onto the secondary filter element main filter element. Secondary filter elements with an oval cross section are usually accommodated in the corresponding filter housing without a positive connection. Characterized in that the secondary filter element has an oval cross section and positive fit can be connected to the filter housing, a secure hold in the filter housing is guaranteed even with such secondary filter elements. Due to the oval geometry of the filter element, a lower pressure loss can be achieved in comparison to a filter element with a circular cross-section with an enlarged filter surface.

In embodiments, the filter element can be positively connected to the filter housing by means of a rotational movement. An angle of the rotational movement is preferably 45 ° to 360 °, d. h., one-eighth to full turn. More preferably, the angle of rotation is 90 ° to 180 °, d. h., a quarter to half turn.

In embodiments, the filter element further comprises a connection section for connecting the filter element to a fluid outlet of the filter housing, wherein the connection section has a circular cross-section. The connection section is preferably tubular. The engagement portion is preferably provided on the terminal portion. The engagement portion may be, for example, a single-start or multi-start thread. The engagement portion may also be part of a bayonet closure. A bayonet lock is a quick to produce and detachable mechanical connection of two cylindrical parts in their longitudinal axis. The parts, in this case the connection section and a fluid outlet of the filter housing, are connected by nesting and counter rotating and thus separated again.

In embodiments, the filter element further comprises a transition section which forms a transition between the oval cross section of the filter element and the circular cross section of the connection section. Preferably, a cross-sectional area of the cross section of the terminal portion is equal to or larger than a cross-sectional area of the cross section of the secondary filter element.

In embodiments, the filter element further comprises a support structure provided on the outside and / or inside of a filter medium of the filter element. The support structure is preferably lattice-shaped and fluid-permeable. The support structure may be molded onto the filter medium in an injection molding process. The support structure may be formed integrally with the connection portion and the transition portion. This ensures a very simple and cost-effective manufacturability of the secondary filter element. The support structure prevents direct contact of the main filter element with the filter medium of the secondary filter element. This prevents fiber abrasion and the formation of holes in the filter medium of the secondary filter element. The filter medium is preferably a nonwoven material. In particular, the filter medium is smooth, d. H. unfolded. On the other hand, a filter medium of the main filter element is preferably folded.

In embodiments, the filter element further comprises a sealing element, in particular an O-ring, for radial sealing of the filter element with respect to the filter housing. The sealing element is preferably made of an elastically deformable material, for example of a rubber material or a thermoplastic elastomer. The sealing element is pressed radially between the connection section of the secondary filter element and the fluid outlet of the filter housing.

Further, a filter assembly, in particular an air filter assembly, proposed with a filter housing and such a filter element, wherein the filter element is positively connected to the filter housing. The filter housing may have a removable service cover, through which the secondary filter element and / or the main filter element are interchangeable. The maintenance cover can be firmly connected by means of quick fasteners with a receiving portion of the filter housing.

In embodiments, the engagement portion is an external thread and the counter-engagement portion is an internal thread or the engagement portion and the counter-engagement portion form a bayonet lock. The external thread is preferably provided on the connection section of the secondary filter element and the internal thread is provided on the inside on the fluid outlet of the filter housing. The threads can be catchy or multi-threaded. As a result, a quick replacement of the secondary filter element is possible.

In embodiments, the filter element has a first positioning element and the filter housing has a second positioning element, wherein the first positioning element abuts the second positioning element in an end position of the filter element and wherein in the end position a main axis of symmetry of the oval cross section of the filter element is parallel to a main axis of symmetry of an oval cross section of the filter element Filter housing is positioned. In particular, the oval cross-sections are each symmetrical, ie, they each comprise a main axis of symmetry and a secondary axis of symmetry, the secondary axis of symmetry being shorter than the main axis of symmetry associated therewith. The main axes of symmetry are preferably positioned perpendicular to the minor axes of symmetry. With the aid of the positioning elements, the secondary filter element is preferably in an end position or operating position in the filter housing when the positioning elements touch positioned. In the end position, the oval cross section of the secondary filter element is positioned in particular in the oval cross section of the filter housing such that an outer contour of the oval cross section of the secondary filter element is circumferentially constantly spaced from an outer contour of the oval cross section of the filter housing. Furthermore, in particular both the main axes of symmetry and the secondary axes of symmetry in the end position are congruent or at least parallel. With the help of the positioning thus a simple and reproducible positioning of the secondary filter element is ensured in the filter housing. That is, an angular position of the secondary filter element in the filter housing is fixed by means of the positioning elements in the end position. An incorrect assembly of the secondary filter element is therefore excluded.

In embodiments, the filter assembly further includes a main filter element received in the filter housing, wherein the filter element is disposed within the main filter element. In particular, the main filter element is releasably attached to the filter element. Preferably, the main filter element is replaced at shorter intervals than the secondary filter element. Due to the positive connection of the secondary filter element with the filter housing, however, an accidental pulling out of the secondary filter element is reliably prevented during the replacement of the main filter element.

Further possible implementations of the filter element and / or the filter arrangement also include combinations of characteristics or method steps described above or below with respect to the exemplary embodiments which are not explicitly mentioned. The person skilled in the art will also add individual aspects as improvements or additions to the respective basic form of the filter element and / or the filter arrangement.

Further embodiments of the filter element and / or the filter arrangement are the subject of the dependent claims and the embodiments of the filter element and / or the filter arrangement described below. In the following, the filter element and / or the filter arrangement will be explained in more detail on the basis of exemplary embodiments with reference to the enclosed figures.

Brief description of the drawings

It shows:

1 a schematic partial perspective sectional view of an embodiment of a filter assembly;

2 a further schematic partial perspective sectional view of the filter assembly according to 1 ;

3 a schematic perspective view of an embodiment of a first filter element and a second filter element for the filter assembly according to 1 ;

4 a schematic perspective view of an embodiment of a second filter element for the filter assembly according to 1 ;

5 a schematic perspective view of another embodiment of a second filter element for the filter assembly according to 1 ;

6 a schematic sectional view of the filter assembly according to 1 ;

7 a schematic sectional view of another embodiment of a filter assembly according to 1 ;

8th an enlarged detail of the sectional views according to 6 and 7 ;

9 an enlarged detail of the perspective views according to 4 and 5 ;

10 an enlarged detail of the perspective view according to 1 ; and

11 a further schematic sectional view of the filter assembly according to. 1 ,

In the figures, identical or functionally identical elements, unless otherwise indicated, have been given the same reference numerals.

Embodiment (s) of the invention

1 shows a schematic partial perspective sectional view of an embodiment of a filter assembly 1 , 2 shows a further schematic partial perspective sectional view of the filter assembly 1 , 6 and 7 each show schematic sectional views of different embodiments of the filter assembly 1 that differ only in their dimensions.

The filter arrangement 1 includes a filter housing 2 and one in the filter housing 2 arranged first filter element 3 , The filter housing 2 can also be referred to as a housing, recording or filter recording. The first filter element 3 is also in the 2 . 3 and 6 to 8th shown. The filter arrangement 1 preferably used in motor vehicles, heavy goods vehicles, construction vehicles, watercraft, rail vehicles, agricultural machinery or vehicles or aircraft application. The first filter element 3 is particularly suitable for filtering combustion air of an internal combustion engine. Preferably, the first filter element 3 an air filter.

The first filter element 3 , which may also be referred to as primary filter element, primary element, main filter element or main element, comprises a filter medium 4 that is a support tube or center tube 5 surrounds. For example, the filter medium 4 on the center tube 5 be wound up. The center tube 5 is preferably lattice-shaped and thus fluid-permeable. The filter medium 4 is preferably folded. The filter medium 4 is for example a filter fabric, filter fabric or a filter fleece. In particular, the filter medium 4 be prepared in a spunbond or meltblown process. Next, the filter medium 4 felted or needled. The filter medium 4 may comprise natural fibers, such as cellulose or cotton, or synthetic fibers, for example of polyester, polyvinyl sulfite or polytetrafluoroethylene. The fibers may be oriented in, skewed and / or transversely to the machine direction during processing.

The first filter element 3 has a first end plate 6 and a second end plate 7 on. The end discs 6 . 7 are preferably made of a plastic material. For example, the end discs 6 . 7 be designed as cost plastic injection molded components. The end discs 6 . 7 For example, they may be made of a polyurethane material. The end discs 6 . 7 can contact the filter medium 4 to be infused. The filter medium 4 is between the end discs 6 . 7 arranged. On a the filter medium 4 facing away from the front 8th the first end disk 6 is a sealing device 9 for sealing the first filter element 3 opposite the filter housing 2 intended. The sealing device 9 is designed to be the first filter element 3 , in particular radially and / or axially, relative to the filter housing 2 seal.

The filter medium 4 can with the end discs 6 . 7 fused, glued or welded. The second end disk 7 is plate-shaped and fluid-impermeable. In the first end disk 6 is a receiving opening 10 intended. To be cleaned fluid L flows during operation of the filter assembly 1 from a raw side RO of the first filter element 3 through the filter medium 4 through as filtered fluid L into one of the center tube 5 surrounded cavity on a clean side RL of the first filter element 3 ,

The first filter element 3 has an oval cross-section in a longitudinal direction LR thereof. The cross section may be from the first end plate 6 in the direction of the second end disk 7 decrease, leaving the first filter element 3 tapered. Preferably, however, the first filter element 3 an oval or elliptical cross section. That is, the first filter element 3 is cylindrical with an oval base. In the present case, a rectangular cross section with rounded corners, an elliptical cross section or a cross section formed from a plurality of circular arcs can be understood here as oval. The cross section is symmetrical.

In the first filter element 3 can be a second filter element 11 be included. The second filter element 11 may be referred to as a secondary filter element, secondary element, sub-filter element or sub-element. The first filter element 3 and the second filter element 11 are arranged so that during operation of the filter assembly 1 first the first filter element 3 and then the second filter element 11 is traversed by the fluid to be cleaned L. Preferably, the second filter element 11 in the receiving opening 10 added. The second filter element 11 preferably also has an oval cross-section. The first filter element 3 may be the second filter element 11 include. The second filter element 11 has a filter medium 12 and a first end disc 13 on. The first end disk 13 can be made of an elastically deformable plastic material, for example of a foamed polyurethane material. The filter medium 12 may be a filter fleece. The second filter element 11 also has a second end plate or transition section 14 on. The filter medium 12 is between the first end disc 13 and the transition section 14 positioned. The filter medium 12 may be supported on the inside by a support tube. The filter medium 12 is preferably smooth, ie unfolded.

The second filter element 11 can, as in 2 and 5 to 8th shown on the outside of the filter medium 12 provided support structure 15 exhibit. The support structure 15 is lattice-shaped and fluid-permeable. Alternatively, as in 4 shown, also on the support structure 15 be waived. The support structure 15 is made of a plastic material. The support structure 15 can in a plastic injection molding process to the filter medium 12 be sprayed. In particular, the support structure 15 integral with the transition section 14 be educated. That is, the support structure 15 can along with the transition section 14 in a plastic injection molding process to the filter medium 12 be sprayed. Because of the support structure 15 on the outside of the filter medium 12 is attached, is when pushing the first filter element 3 on the second filter element 11 and / or during removal of the same from the second filter element 11 a fiber abrasion on the filter medium 12 prevented. That is, the center tube 5 only contacts the support structure 15 and not the filter medium 12 , As a result, damage and in particular a hole formation in the filter medium 12 reliably prevented.

The second filter element 11 comprises a tubular connection portion 16 , The connection section 16 has a circular cross-section. The connection section 16 is preferably material integral with the transition section 14 and the support structure 15 formed, wherein the transition section 14 between the support structure 15 and the connection section 16 is arranged. The transition section 14 forms a transition between the oval cross section of an interior 17 of the second filter element 11 and the circular cross section of the terminal section 16 , wherein a cross-sectional area of the interior 17 is preferably the same size as a cross-sectional area of the connection portion 16 ,

At the connection section 16 is an engaging section 18 intended. The engaging section 18 can also be referred to as engagement geometry, engagement contour, connection geometry or connection contour. The engaging section 18 is how in 1 to 10 shown at the connection section 16 provided external thread. Alternatively, the engagement portion 18 also be part of a bayonet catch. In particular, the engagement portion 18 be a catchy or multi-threaded. At the connection section 16 is also a sealing element 19 provided that over the connection section 16 slipped over. The sealing element 19 is preferably made of an elastic plastic material, in particular a thermoplastic elastomer, or a rubber material. The sealing element 19 can be an O-ring. Preferably, the sealing element 19 between the transition section 14 and the engaging portion 18 arranged. Preferably, the sealing element 19 at a transition between the connection section 16 and the transition section 14 intended. The connection section 16 forms a Fluidausströmöffnung 20 of the second filter element 11 ,

The filter housing 2 includes a receiving section 21 for receiving the first filter element 3 and the second filter element 11 , The recording section 21 is preferably made of a plastic material. Alternatively, the receiving section 21 be made of sheet metal, in particular made of sheet steel. For example, the receiving section 21 be designed as a low-cost plastic injection molded component. Furthermore, the filter housing 2 one of the receiving section 21 removable maintenance cover 22 on. Over the maintenance cover 22 can be the first filter element 3 and the second filter element 11 from the receiving section 21 be removed. The maintenance cover 22 can with the help of quick fasteners 23 with the receiving section 21 be connected. Between the maintenance cover 22 and the receiving section 21 a sealing device can be provided.

The filter housing 2 or the receiving section 21 has a fluid inlet 24 to the inlet of the fluid to be filtered L in the filter housing 2 and a fluid outlet 25 to the outlet of the filter elements 3 . 11 filtered fluid L from the filter housing 2 on. The fluid inlet 24 and the fluid outlet 25 are preferably tubular and may have a circular cross-section. The fluid L to be filtered enters the fluid inlet in an inflow direction E. 24 one. The fluid L occurs in an outflow direction A preferably parallel to the longitudinal direction LR of the first filter element 3 from the fluid outlet 25 out. The inflow direction E is oriented perpendicular to the outflow direction A. In the filter housing 2 and in particular in the receiving section 21 is an intervention area 26 provided in the the sealing device 9 of the first filter element 3 intervenes. The intervention area 26 can the fluid outlet 25 completely circulate.

On the maintenance cover 22 can be a particle discharge opening 27 be provided. The particle discharge opening 27 is preferably tubular. About the particle discharge opening 27 can from the fluid L pre-separated particles from the filter housing 2 be dissipated. The particle discharge opening 27 may have a valve.

The filter housing 2 includes one to the engagement portion 18 of the second filter element 11 corresponding counter-engagement section 28 , The counter-engagement section 28 is preferably inside on the fluid outlet 25 intended. The engaging section 18 is adapted to form fit in the counter-engagement section 28 intervene, leaving the second filter element 11 positive fit with the filter housing 2 and in particular with the receiving section 21 is connectable. The counter-engagement section 28 can also be referred to as a counter-engagement geometry, counter-engagement contour, connection geometry or connection contour. The counter-engagement section 28 is one at the fluid outlet 25 inside provided internal thread. Alternatively, the counter-engagement portion 28 also be part of a bayonet catch. That is, it is between the second filter element 11 and the filter housing 2 provided a rotary coupling. In particular, the counter-engagement section 28 be a catchy or multi-threaded.

In one in the filter housing 2 screwed state of the second filter element 11 is the sealing element 19 between one the connection section 16 fully encircling paragraph 29 and the counter-engagement portion 28 positioned. The sealing element 19 is then between the connection section 16 and the fluid outlet 25 compressed radially. That is, the sealing element 19 seals the second filter element 11 radially opposite the filter housing 2 from.

On the second filter element 11 and in particular at the paragraph 29 is how in 9 and 10 shown, a first positioning element 30 intended. On the filter housing 2 and in particular at the fluid outlet 25 is one to the first positioning element 30 corresponding second positioning element 31 arranged. In the in the filter housing 2 screwed state of the second filter element 11 contacts the first positioning element 30 , as in 10 shown, the second positioning element 31 , As a result, the rotatability of the second filter element 11 opposite the filter housing 2 limited. That is, with the aid of the positioning elements 30 . 31 ensures that the second filter element 11 in only a predetermined positioning relative to the filter housing 2 can be arranged.

The filter housing 2 points as in 11 shown only very schematically, an oval cross-section 32 and the second filter element 11 has an oval cross-section 33 on. The cross sections 32 . 33 are shown in simplified form as ellipses. The oval cross sections 32 . 33 are each symmetrical, ie they each comprise a main axis of symmetry 34 . 35 and a minor axis of symmetry 36 . 37 , wherein the minor axis of symmetry 36 . 37 each shorter than their associated main axis of symmetry 34 . 35 is. The main axes of symmetry 34 . 35 are perpendicular to the minor axes of symmetry 36 . 37 arranged. With the help of positioning elements 30 . 31 is the second filter element 11 then when the positioning elements 30 . 31 touch, in an end position or operating position in the filter housing 2 positioned. In the final position is the oval cross-section 33 of the second filter element 11 so in the oval cross-section 32 of the filter housing 2 positioned that an outer contour 38 of the oval cross-section 33 of the second filter element 11 from an outer contour 39 of the oval cross-section 32 of the filter housing 2 circumferentially constantly spaced. Furthermore, both the main axes of symmetry 34 . 35 as well as the minor symmetry axes 36 . 37 in the final position congruent or at least parallel.

Thereby, that the second filter element 11 positive fit with the filter housing 2 is connected, it is ensured that the second filter element 11 upon removal of the first filter element 3 from the same not from the fluid outlet 25 is pulled out. Contamination of the clean side RE with fluid L to be filtered is thereby prevented. Due to the support structure 15 is further when replacing the first filter element 3 a damage of the second filter element 11 and in particular the filter medium 12 locked out. With the help of positioning elements 30 . 31 is a simple and reproducible positioning of the second filter element 11 in the filter housing 2 guaranteed. That is, an angular position of the second filter element 11 in the filter housing 2 is using the positioning elements 30 . 31 set in the final position.

LIST OF REFERENCE NUMBERS

1

A filter assembly

2

filter housing

3

filter element

4

filter media

5

center tube

6

end disk

7

end disk

8th

front

9

sealing device

10

receiving opening

11

filter element

12

filter media

13

end disk

14

Transition section

15

support structure

16

connecting section

17

inner space

18

engaging portion

19

sealing element

20

fluid outflow port

21

receiving portion

22

maintenance cover

23

quick release

24

fluid inlet

25

fluid outlet

26

engagement area

27

Particle outlet opening

28

Against engaging section

29

paragraph

30

positioning

31

positioning

32

cross-section

33

cross-section

34

Main axis of symmetry

35

Main axis of symmetry

36

In addition to the axis of symmetry

37

In addition to the axis of symmetry

38

outer contour

39

outer contour

A

outflow

e

inflow

L

fluid

LR

longitudinal direction

RL

clean side

RO

unfiltered side

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• EP 2227307 B1 [0003]

Claims (10)

Filter element ( 11 ), in particular secondary filter element, which in a main filter element ( 3 ) is receivable, with an engaging portion ( 18 ), which is adapted to a corresponding counter-engagement section ( 28 ) of a filter housing ( 2 ) of the filter element ( 11 ) to engage the filter element ( 11 ) in a form-fitting manner with the filter housing ( 2 ), the filter element ( 11 ) an oval cross section ( 33 ) having. Filter element according to claim 1, wherein the filter element ( 11 ) by means of a rotational movement form-fitting manner with the filter housing ( 2 ) is connectable. Filter element according to claim 1 or 2, further comprising a connection portion ( 16 ) for connecting the filter element ( 11 ) to a fluid outlet ( 25 ) of the filter housing ( 2 ), wherein the connection section ( 16 ) has a circular cross-section. Filter element according to claim 3, further comprising a transition section ( 14 ), which forms a transition between the oval cross-section ( 33 ) of the filter element ( 11 ) and the circular cross section of the connection section ( 16 ). Filter element according to one of claims 1-4, further comprising an outside and / or inside of a filter medium ( 12 ) of the filter element ( 11 ) provided support structure ( 15 ). Filter element according to one of claims 1-5, further comprising a sealing element ( 19 ), in particular an O-ring, for radial sealing of the filter element ( 11 ) opposite the filter housing ( 2 ). Filter arrangement ( 1 ), in particular air filter arrangement, with a filter housing ( 2 ) and a filter element ( 11 ) according to any one of claims 1-6, wherein the filter element ( 11 ) in a form-fitting manner with the filter housing ( 2 ) connected is. Filter assembly according to claim 7, wherein the engaging portion ( 18 ) an external thread and the counter-engaging portion ( 28 ) is an internal thread or wherein the engagement portion ( 18 ) and the counter-engagement section ( 28 ) form a bayonet lock. Filter arrangement according to claim 7 or 8, wherein the filter element ( 11 ) a first positioning element ( 30 ) and the filter housing ( 2 ) a second positioning element ( 31 ), wherein the first positioning element ( 30 ) in an end position of the filter element ( 11 ) on the second positioning element ( 31 ) and wherein in the end position a main axis of symmetry ( 34 ) of the oval cross section ( 33 ) of the filter element ( 11 ) parallel to a main axis of symmetry ( 35 ) of an oval cross section ( 32 ) of the filter housing ( 2 ) is positioned. Filter arrangement according to one of claims 7-9, further comprising a main filter element ( 3 ) located in the filter housing ( 2 ), wherein the filter element ( 11 ) within the main filter element ( 3 ) is arranged.

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