DE202009000969U1 - filter element - Google Patents

Abstract

A filter element comprising a filter medium (11) and end discs (12), the filter medium (11) having a plurality of contiguous pleats (17) with a pleat base (25) and pleat tips (22) between the pleat base (25) and the fold tip (22) has a fold height (H), wherein the filter medium (11) is closed annularly, and wherein the end disks (12) are sealingly connected to the filter medium (11) at its end faces (19), characterized in that at least in a partial region of the filter medium (11) increases or decreases the pleat height (H) between the adjacent pleats (17) over a plurality of pleats (17).

Description

Technical area

The The invention relates to a filter element according to the preamble of the claim 1 and 10.

State of the art

From the EP 0754 483 a filter element is known, which has a folded filter medium with two end-side arranged end plates. The filter medium is closed annularly, wherein an inner diameter and an outer diameter are formed. The filter medium has a section in which the folds are made shorter. In this section, the constant height of the folds also forms a circular geometry, this radius being smaller than the radius of the outer diameter but larger than the inner diameter. Thus, a recess is formed within the outer cross section.

Of the Invention has for its object to provide a filter element, which is integrated in construction spaces with special geometries can be. Another object is to provide a filter element to create which with specially trained geometries over has a maximum filter area. According to one Another object is to provide a filter element which Loading distributions is customizable. Another task concerns the production of a filter element, which in special installation spaces can be used. Another task is a Produce specially shaped filter element cost.

These Tasks become due to the increasing or decreasing fold height solved several adjacent folds.

The cost-effective production of the filter element is by the variation of the feed ratio of the filter medium in relation to the rotational speed of the embossing rolls solved.

Disclosure of the invention

The Filter element according to the invention is for cleaning a gaseous or liquid fluid provided. In particular, the filter element for cleaning fluids, the Internal combustion engines, such as. B. in motor vehicles supplied be provided. Such fluids are z. As fuels, oils or Air. The filter element has end discs and a pleatable, annularly closed filter medium, which made of different materials, such. Cellulose, metallic or synthetic fibers or mixtures thereof can. The filter medium has a plurality of adjoining ones Wrinkles on, with a fold over a wrinkle bottom and has a fold tip. Between the fold bottom and the fold tip is the fold height formed. The fold height depends on a given folding division, which an angle between pleat legs conditional. With a small one Angle between the pleat legs is the pleat height larger, thereby reducing to a given area more wrinkles and thus a larger filter surface can be accommodated. At a big angle between the wrinkle legs, the wrinkle height is lower. in this connection However, only a few wrinkles can be provided by where the effective filter area is lower. Order at given, constant folding pitch, which optimal arrival or downstream conditions allows you to realize different levels of folds, the length of the pleat legs is varied. This wrinkle height takes at constant Faltenteilung at least in a partial area of the filter medium between the adjacent folds over several Fold away to or from. Thus, special geometric shapes, which deviate from the usual cylindrical shape, with maximum Filter surface feasible. Through the annular Join together the pleated filter media formed two end faces, which sealingly connected to end plates become. The end discs can be made of any shape-retaining Material, such. As metal or plastic, exist. Here can the filter medium connected by suitable methods with the end plates become. Preferably, the compound by z. B. welding, Gluing or melting into the end plate are formed. The End plates have a cross-sectional area, which is adapted to the particular geometry of the installation space and which the end face of the filter medium covered. By the increasing or decreasing fold height can create filter elements which, with maximum filter surface in confined spaces or in installation spaces with interference contours and interfering Component walls can be integrated. in this connection the pleat tips of the filter medium can follow space curves, without changing the folding pitch and filter area get lost.

at an advantageous embodiment takes the fold height the adjacent folds continuously to or from. So is a "seamless" transition reached between in the course of the pleat tips. The fold height increases or decreases in relation to the Fold height of the adjacent fold by less than half the adjacent fold height. Preferably the wrinkle height difference between the adjacent wrinkles less than ¼ of the fold height. Thus features the filter element over flowing contours, which advantageous for an optimal inflow and outflow are. Furthermore, the filter element can be optimally adapted to bends become.

According to one alternative embodiment takes the pleat height between the adjacent folds jump to and from. Here is the wrinkle height difference between the adjacent folds greater than or equal to ¼ of Wrinkle height being at a height jump between the adjacent folds also continuous increases or decreases of Can follow fold height. Thus, an adaptation of the Filter element with the largest possible filter surface, too in extremely cramped or complicated designed spaces possible.

According to the invention takes the pleat height in such a way or from that in a circular Inner cross section of the annular closed filter medium through the pleat tips a non-circular outer cross-section is formed. The circular inner cross section is advantageous to easily connect the filter element to a connecting piece and seal. In this case, at least one of the end plates has over a circular opening, which is smaller as the inner cross section formed by the filter medium. By the Constant fold division can be an optimal inflow or outflow of the fluid to be cleaned to or from inside. Not circular outer cross-section, which through the Wrinkle tips is formed, z. B. notches or wave contours have, which allow optimal utilization of space.

According to one special embodiment of the invention is the non-circular Outer cross section of the pleat tips triangular formed, wherein the inner cross section is circular is. By this embodiment, the filter element in wedge-shaped Building spaces can be integrated without affecting the effective filter area is reduced. Thus, an optimal filter life, dirt pickup and Durchströmbarkeit realized with minimal pressure losses.

According to one alternative embodiment is the non-circular outer cross-section the fold tips clover-shaped. Thus, can the filter element with the greatest possible Filter surface in corresponding notched installation spaces to get integrated.

at a special embodiment of the invention take the fold heights in such a way that the case of a circular inner cross section of the annular closed filter medium a circular Outer cross section is formed by the pleat tips, wherein the inner cross section is eccentric to the outer cross section is arranged. In this embodiment, a cylindrically shaped Filter element integrated in a cylindrically designed space be, with the inlet and outlet, which with the end plate corresponds arranged eccentrically.

According to one alternative embodiment of the invention take the fold heights in such a way that the case of a circular outer cross section of Pleat tips a non-circular inner cross section is formed. Here, the end plate with a nozzle arbitrary Cross section can be connected without the filter surface is significantly reduced.

It It is advantageous that the pleat tips on a positional fixation are held stationary. Here, the position fixing, which z. B. by a glue bead, a filament winding or a support grid is formed, be associated with the pleat tips. This connection can z. B. generated by welding or gluing.

According to an alternative embodiment of the invention, the filter element is designed as a flat filter element, in particular for cleaning air. The filter element can in this case be used for cleaning the air required for combustion of an internal combustion engine or for a passenger compartment. The filter element has a filter medium which is folded in a zig-zag shape. The filter medium is surrounded by a circumferential seal, which as z. B. sealing bead or sealing tape is formed. Here, the sealing bead z. B. be formed from a polyurethane foam or rubber. The sealing tape may be formed from a paper, cardboard or filter media strip. The seal is the peripheral sides, in particular the front sides, the filter medium sealing the verbun. It is advantageous if the sides of the filter medium are sealingly enclosed by the sealing material. The filter medium is formed by a single integral web, in which fold edges are introduced. The fold edges are arranged at different distances in the filter medium, depending on how high a fold should be. Low wrinkles have folded creases closer together than higher creases. The folded edges form according to their arrangement after setting up a wrinkle bottom or a fold tip. According to the invention, the fold height between the adjacent folds increases or decreases over several folds, at least in a partial area of the filter medium, the fold pitch of the folds being constant. In this case, the wrinkle height of the successive wrinkles can increase or decrease continuously or the height of the wrinkles can suddenly be increased and this wrinkle height can be maintained over several folds. Thus, the filter element can have a sufficiently large filter surface and be integrated in tight spaces. Furthermore, the filter element can be adapted to particular load distributions. In this case, the filter surface in the areas in which a higher dirt holding capacity is required by an increased fold height, be increased. Such areas k nen z. B. be arranged in the region of the inlet for the fluid to be cleaned. The above-described embodiments of the annular closed filter elements can be analogously transferred to the flat filter element.

Brief description of the drawings

The Invention will be described below with reference to schematic embodiments explained in more detail. Hereby shows:

1 a filter element in perspective view with a partial section,

2a a detail of a filter element in plan view,

2 B a fold,

3 a round filter element with triangular outlet in plan view,

4 a cloverleaf-shaped filter element in plan view,

5 a triangular filter element in plan view,

6 an oval filter element in plan view,

7 a round filter element with eccentric outlet,

8th a freeform filter element in plan view,

9 a semicircular filter element in plan view,

10 a pleating device

11 a flat air filter element,

12 the flat air filter element according to 11 in section along the section line AA and

13 the flat air filter element according to 11 in section along the section line AA in an alternative embodiment.

Embodiment (s) of the invention

In 1 is a filter element 10 shown in perspective view with a partial section. The filter element 10 has a pleated filter medium 11 and two end discs 12 , The filter element 10 has an outer cross-section 13 , which of a circular cylindrical shape (shown in phantom) 14 differs. in these areas has the outer cross section 13 over indentations 20 , Here is the outer cross section 13 the projected area in plan view. By the deviation from the cylindrical shape 14 can the filter element 10 be integrated into spaces, which by surrounding components 15 (shown in dash-dotted lines) are deformed. Furthermore, the filter element has 10 via a circular inner cross-section 16 which passes through both the upper end disc 12 , as well as through the filter medium 11 is formed. In this inner cross section 16 a circular nozzle (not shown) can be plugged sealing. Through this nozzle, the fluid to be cleaned can be added to or removed. Accordingly, the filter medium becomes 11 flows from the inside to the outside and from the outside to the inside. The filter medium 11 is formed as a semifinished product as a rectangular path. After pleating, it has a variety of tick-shaped folds 17 , where the first fold 17 with the last fold 17 by means of a clip 18 is sealingly connected. The clip 18 can z. B. are formed by a thin metal sheet or a plastic rail, wherein the clip 18 z. B. may be pressed, glued or spot welded. Alternatively, the wrinkles can 17 also sewn, welded, glued or connected by other methods. Through this connection is the filter medium 11 closed in a ring. The filter medium 11 has an upper and a lower end face 19 , At these ends is the filter medium 11 sealing with the end discs 12 connected. The filter medium 11 has wrinkles 17 with different pleat heights H1 to H6, wherein these pleat heights H1 to H6 are only exemplary and on a real filter element 10 more or less wrinkles 17 can be provided with different fold heights H. The pleat height H1 corresponds to the maximum pleat height which is arranged in the areas where the outer cross section 13 is circular. According to the indentations 20 the fold heights H2 to H6 increase or decrease, whereby the increase or decrease on the previous fold 17 refers. The different fold heights H1 to H6 are "real" height differences, which arise during pleating and not by a change in the placement of the folds 17 are brought about. In the inner cross section 16 are the wrinkles 17 evenly distributed, with all folds 17 over substantially equal distances A (see 2 ) to each other. To the wrinkles 17 holding at the desired position is a glue bead 21 provided, which with the folds 17 in the area of pleat tips 22 connected is. The glue bead 21 is in the middle between the front sides 19 arranged. In other embodiments, also several glue beads 21 be provided, which at any point between or on one or both end faces 19 are arranged. Alternative to the glue bead 21 can also support grid or filament winding, in particular spiralför mige thread winding, be provided. This position fixation of the pleat tips 22 can of course be used in all other embodiments.

Follows the invention with reference to 2a which a section of a filter element 10 ' in plan view without the upper end plate 12 shows, respectively 2 B which is a fold 17 shows, explained in more detail. These basic statements apply in an analogous manner to all exemplary embodiments. Of the 1 corresponding elements are provided with the same reference numerals. In contrast to 1 is the filter element 10 ' angular, with the inner cross section 16 is circular. The end discs 12 have the same geometry as the filter media 11 formed (see dash-dotted lines 23 . 24 ), the end disc 12 has slightly larger outlines, around the end faces 19 of the filter medium 11 sure to cover. The wrinkles 17 extend between the inner dotted line 23 and the outer dot-dash line 24 , The distances A of the folds 17 at her wrinkle bottom 25 to each other, ie in the area of the inner dot-dash line 23 are equal, apart from manufacturing tolerances, resulting in a constant pleat pitch. This fold division is chosen such that the fluid to be filtered, the filter medium 11 can flow through optimally. The wrinkles 17 are aligned in such a way that their central axes 26 the center M (see 1 ) of the inner cross section 16 to cut. Starting from the fold bottom 25 pleat legs extend 27 to the fold tip 22 , Between the pleated legs 27 is a wrinkle angle 28 locked in. In the same way is between the pleat legs 27 , which are from the fold bottom 25 extend out, an angle 29 educated. The formed angles 29 are at all wrinkles 17 about the same size. In the same way are the wrinkle angles 28 also the same size, the size of the angle 29 different from the size of the wrinkle angle 28 can be. In special embodiments, the wrinkle angles 28 the same size as the angles 29 , The pleat height H is defined to be between the pleat tip 22 and at right angles to the central axis 26 projected wrinkle reason 25 is formed (see 2 B ).

In 3 is a round filter element 30 with a triangle outlet 31 shown in plan view. The round filter element 30 corresponds to the filter element 10 respectively. 10 ' , Identical elements are provided with the same reference numerals. The round filter element 30 has the cylindrical shape and contrary to 1 , are no indentations 20 available. Through the triangle outlet 31 with a triangular inner cross section 16 ' is the dash-dotted line 23 ' also triangular. Thus, different wrinkle heights H in the wrinkles 17 required. In this embodiment, it may be necessary that the uniform fold pitch, or the same distances A, not on the inner dot-dash line 23 but at the outer dot-dash line 24 is applied. In this case, the determination of the pleat height H becomes the intersection of the central axis 26 ' with the line 24 based.

In 4 is a cloverleaf-shaped filter element 10 '' with a circular inner cross section 16 shown in plan view. Elements which correspond to the preceding figures are provided with the same reference numerals. The outer cross section 13 gives way to the indentations 20 from the cylinder shape 14 from, whereby the cloverleaf is formed. In this case, the fold height H varies between an outline shown in phantom 24 whose maximum extent is defined by a maximum diameter 33 is limited, and a minimum diameter 32 (shown in phantom). From the minimum diameter 32 from takes the pleat height H of the subsequent fold 17 steadily until the fold 17 to the maximum diameter 33 pushes and thus has reached the maximum wrinkle height Hmax. After reaching the maximum pleat height Hmax, the pleat height H is reduced steadily until the minimum pleat height Hmin is reached again. Thus, the pleat height H of the subsequent fold 17 is either larger or smaller than the fold height H of the preceding fold 17 , whereby the cloverleaf is formed. In the area of the circular inner cross section 16 have the wrinkles 17 over equal distances to each other, whereby the flow conditions can be optimally adjusted.

In 5 is a triangular filter element 34 shown in plan view. Elements that correspond to the preceding figures are provided with the same reference numerals. In this embodiment, the wrinkles extend 17 between the minimum diameter 32 and the maximum diameter 33 , The inner cross section 16 is circular. Analogous to 4 the pleat height H increases from the smallest pleat height Hmin up to the greatest pleat height Hmax, wherein the pleat heights H are selected such that the pleat tips 22 a linear outer contour, namely a triangular leg 35 of the triangular filter element 34 is formed. Also in this embodiment, the folding pitch is in the area of the inner dot-dash line 23 evenly arranged.

The triangular filter element 34 could only have two triangular legs 35 dispose and the third side could be along the maximum diameter 33 run. In this embodiment, a cake piece-shaped filter element would then result, which can be integrated into wedge-shaped space.

In 6 is an oval filter element 36 shown in plan view. Elements that correspond to the preceding figures are provided with the same reference numerals. The oval shape varies between the minimum diameter 32 and the maximum diameter 33 , Inside the oval filter element 36 is a circular inner cross-section 16 arranged. The even wrinkle distribution is in the area of the inner cross section 16 arranged. Due to the variation of the fold heights H, the oval shape is formed on the outside, wherein the inner cross section 16 is circular. The real end disk 12 has an outer contour, which is slightly larger than that of the pleat tips 22 formed outer cross section 13 is to ensure a secure sealing of the end faces. Incidentally, this applies to all embodiments.

In 7 is a round filter element 30 ' with eccentrically arranged circular inner cross section 16 , which serves as an outlet for the filtered fluid, shown. Elements that correspond to the preceding figures are provided with the same reference numerals. The center M of the inner cross section 16 is as a reference point for the distribution of wrinkles 17 intended. Around this center M around the minimum diameter extends 32 and the maximum diameter 33 wherein the fold heights H are of minimum diameter 32 up to the maximum diameter 33 increase steadily and then from the maximum diameter 33 to the minimum diameter 32 lose weight again. Due to the different levels of wrinkles 17 is at the pleat tips 22 the cylindrical shape 14 formed, which frontally of a circular end plate 12 is completed. The through the pleat tips 22 formed cylinder shape 14 has a middle 37 which extends over a distance E axially to the center M of the inner cross section 16 is spaced.

In 8th is a freeform filter element 38 shown in plan view. Elements that correspond to the preceding figures are provided with the same reference numerals. The wrinkles 17 extend between the minimum diameter 32 and the maximum diameter 33 , where the maximum diameter 33 of the free-form element 38 only achieved in a few places. Inside is the inner cross section 16 circular, with the folds 17 in the area of the inner dotted line 23 are arranged at regular intervals A.

In 9 is a semi-circular filter element 10 ''' shown in plan view. This filter element 10 ''' has, like most of the preceding embodiments, a circular inner cross-section 16 , The center M is through the distance E from the center 37 of the filter element 10 ''' spaced. Due to the increasing or decreasing fold heights H is due to the pleat tips 22 a straight string 39 educated. Thus, the filter element 10 ''' be attached very close to flat surfaces.

In 10 a pleating device is shown schematically. The pleating device has two embossing rollers 40 , which have a surface structure. This surface structure is for introducing Faltkanten in the filter medium 11 suitable. The filter medium 11 is as a continuous material on a roll 41 wound. Furthermore, the pleating device has a controller 42 , which with the embossing rollers 40 and a media guide 43 connected is.

To the filter medium 11 to fold, the filter medium 11 the embossing rollers 40 fed at a feed rate v. This feed rate v is through the media guide 43 certainly. The embossing rollers 40 rotate at a predetermined speed D. At constant speed D and feed speed v arise wrinkles with the same pleat legs 27 and thus the same fold heights H. If the ratio between the feed rate v and speed D is changed, so different sized pleat legs 27 and thus different fold heights H. For exact control of the desired size of the pleat legs 27 It is advantageous if only one parameter, ie either feed rate v or speed D is varied. If, however, very different fold heights H are to be generated, a simultaneous change of both parameters may also be necessary.

If at constant speed D, the feed rate v through the media guide 43 is lowered, the embossed fold edges are closer to each other. Thus, the resulting fold height H is lower. At an increased feed rate v becomes more filter medium 11 between the embossing rollers 40 passed, whereby the folding edges are farther apart. Thus, larger fold heights H are realized.

Alternatively or in addition to the variation of the feed rate v, the rotational speed D can also be changed. At a higher speed D, shorter pleat legs become 27 and thus produces smaller fold heights H. At lower speeds D, longer pleat legs become 27 and thus formed greater fold heights H.

By controlling the speed D or medium guide 43 the distances of the embossed fold edges can be varied, which form different fold heights H after setting up the folds. Thus, filter elements with different fold heights H can be realized, which over unre have regular outer cross sections, as described above, have.

In 11 is a flat air filter element 45 shown, which has a rectangular outer cross section 13 ' features. As an alternative to the illustrated rectangular shape, the flat air filter element 45 also have other outer cross-sections over others. These can be z. B. triangular, trapezoidal, round or oval. Furthermore, outer cross sections with irregularly extending sides are possible, which are arranged at an angle to each other and "potato" -like outer cross-sections forms. The flat air filter element 45 can z. B. be used as an intake air filter for internal combustion engines or cabin air filters for passenger compartment. The flat air filter element 45 has a filter medium 11 , z. B. from cellulose, synthetic fibers or from a mixture thereof, which is pleated. The filter medium 11 is from a circumferential sealing bead 46 surround. The sealing bead 46 is by an elastic material, such. As rubber or polyurethane foam formed. The sealing bead 46 encloses the filter medium 11 at its peripheral edges, in particular end faces 19 ' sealing, with the sealing bead 46 is designed such that it can be inserted into a filter housing (not shown) and this contacted sealingly. The flat air filter element 45 has areas with different levels of wrinkles 17 ' , where the folds 17 ' be generated from a single continuous web. Here, the folding edges are analogous to 10 stamped and set up at different intervals.

In 12 is the flat air filter element 45 according to 11 shown in section along the section line AA. Of the 11 corresponding components are provided with the same reference numerals. The filter medium 11 has wrinkles 17 ' , which have different fold heights H. The illustrated pleat heights H1 to H5 are selected by way of example, therefore, more or less wrinkles can occur with real filter elements 17 ' be provided with different fold heights H. In the illustrated flat air filter 45 First, the fold height H1 to H5 increases linearly. After the maximum pleat height H5 has been reached, the pleat height H decreases again continuously until a defined pleat height H is reached, which over the further course of the filter medium 11 stays the same. In other embodiments, it may come to new changes in the wrinkle height H, which run continuously or suddenly. Because the fold height H of the folds 17 ' is greater than the height of the sealing bead 46 it is necessary that the wrinkles 17 ' on their faces 19 ' are closed. This can be done by gluing or welding the filter medium 11 on the front sides 19 ' or by attaching a fold closure (not shown), z. As a strip-shaped band of a filter medium, paper or plastic, take place. By changing the pleat height H, more filter medium can be used in defined areas 11 accommodated or the filter element can be adapted to special geometries.

In 13 is the flat air filter element 45 ' according to 11 shown in section along the section line AA in an alternative embodiment. The illustrated flat air filter element 45 ' is intended for the cleaning of passenger compartments of motor vehicles, in particular of passenger cars or trucks. Here is the sealing bead 46 ' as a circumferential sealing tape 47 formed, which preferably consists of the same material as the filter medium 11 , The sealing tape 47 is with the front ends 19 ' of the filter medium 11 sealingly bonded or welded, creating a dense composite is produced. The sealing tape 47 contacts the filter housing (not shown), whereby leakage air currents are greatly reduced or completely prevented. The filter medium 11 has wrinkles 17 ' which are divided into three areas. In the first and third areas, the pleat height H1 corresponds to the height of the sealing strip 47 , In the second area, the wrinkle height H2 is greater than the height of the sealing strip 47 , Therefore, the wrinkles must be 17 '' in this area on the front sides 19 ' be sealed separately. This can be done according to the 12 executed variants carried out.

QUOTES INCLUDE IN THE DESCRIPTION

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Cited patent literature

• EP 0754483 [0002]

Claims (10)

Filter element comprising a filter medium ( 11 ) and end discs ( 12 ), whereby the filter medium ( 11 ) a plurality of contiguous folds ( 17 ) with a fold bottom ( 25 ) and pleat tips ( 22 ), wherein between the fold bottom ( 25 ) and the fold tip ( 22 ) a fold height (H) is formed, wherein the filter medium ( 11 ) is closed annularly, and wherein the end discs ( 12 ) with the filter medium ( 11 ) at its end faces ( 19 ) are sealingly connected, characterized in that at least in a partial region of the filter medium ( 11 ) the fold height (H) between the adjacent folds ( 17 ) over several folds ( 17 ) increases or decreases. Filter element according to claim 1, characterized in that the pleat height (H) between the adjacent pleats ( 17 ) increases or decreases continuously. Filter element according to claim 1, characterized in that the pleat height (H) between the adjacent pleats ( 17 ) increases or decreases abruptly. Filter element according to one of claims 1 to 3, characterized in that the fold heights (H) increase or decrease in such a way that in the case of a circular inner cross-section (FIG. 16 ) of the annular closed filter medium ( 11 ) through the pleat tips ( 22 ) a non-circular outer cross-section ( 13 ) is formed. Filter element according to claim 4, characterized in that the non-circular outer cross-section ( 13 ) of the pleat tips ( 22 ) is triangular in shape. Filter element according to claim 4, characterized in that the non-circular outer cross-section ( 13 ) of the pleat tips ( 22 ) is clover-shaped. Filter element according to one of claims 1 to 3, characterized in that the fold heights (H) in such a way or decrease, that in a circular inner cross-section ( 16 ) of the annular closed filter medium ( 11 ) a circular outer cross-section ( 13 ) through the pleat tips ( 22 ) is formed, wherein the inner cross section ( 16 ) eccentric to the outer cross section ( 13 ) is arranged. Filter element according to one of claims 1 to 3, characterized in that the fold heights (H) in such a way or decrease, that in a circular outer cross-section ( 13 ) of the pleat tips ( 22 ) a non-circular inner cross-section ( 16 ) is formed. Filter element according to one of the preceding claims, characterized in that the pleat tips ( 22 ) via a position fixation ( 21 ) are held stationary. Flat filter element ( 45 ), comprising a filter medium ( 11 ) and a seal ( 46 . 46 ' ), whereby the filter medium ( 11 ) a plurality of contiguous folds ( 17 ) with a fold bottom ( 25 ) and pleat tips ( 22 ), wherein between the fold bottom ( 25 ) and the fold tip ( 22 ) a fold height (H) is formed, and wherein the seal ( 46 . 46 ' ) with the filter medium ( 11 ) at its end faces ( 19 ) are sealingly connected, characterized in that at least in a partial region of the filter medium ( 11 ) the fold height (H) between the adjacent folds ( 17 ) over several folds ( 17 ) increases or decreases.