Ring filter element assembly comprising two ring filter elements which are rotationally aligned relative to each other

Abstract

The invention relates to a ring filter element assembly comprising two ring filter elements through which a flow can pass serially. An outer ring filter element surrounds an inner ring filter element at least in a sub-region of the axial extension thereof. The rotational position of the two ring filter elements relative to each other is fixed in that an engagement element arranged between the two ring filter elements engages at least into one of the ring filter elements in the radial direction. The engagement element can be held on a central tube which extends between filter medium bodies of the ring filter elements. In one embodiment, the central tube is secured to one of the ring filter elements, and the engagement element engages into the other ring filter element. In another embodiment, the engagement element engages into the two ring filter elements, and the central tube can then be released from the two ring filter elements and can be secured to a filter housing. One of the ring filter elements or both ring filter elements can have bellows. The engagement element preferably engages into a fold which is spread out.

Description

[0001] Ring filter element arrangement with two rotationally aligned ring filter elements

[0002] This patent application claims priority from German patent application DE102023129017.7, filed with the German Patent and Trademark Office on October 23, 2023, the contents of which are hereby incorporated by reference.

[0003] Technical area

[0004] The invention relates to a ring filter element arrangement for arrangement in a filter housing, with a first ring filter element and a second ring filter element, each having a filter medium body which encloses an interior space, wherein the second ring filter element is at least partially accommodated in the interior space of the filter medium body of the first ring filter element, wherein an outer circumferential surface of the filter medium body of the second ring filter element and an inner circumferential surface of the filter medium body of the first ring filter element adjoin one another in an interface region.

[0005] State of the art

[0006] Such a ring filter element arrangement is known from WO 2015 / 092681 A1.

[0007] In various applications, it may be necessary to pass a fluid to be filtered, especially air, sequentially through two different filter media to remove all interfering components from the fluid. For a space-saving design, two annular filter media bodies can be used, with one of the filter media bodies located inside the other.

[0008] It is important that matching ring filter elements are used that are suitable for the respective application. Furthermore, it is often important that the two ring filter elements are correctly aligned. For example, air mass meters often react sensitively to changes in the alignment of filter elements. This also applies to essentially rotationally symmetrical ring filter elements, which exhibit certain manufacturing-related deviations from rotational symmetry when installed in different rotational positions.

[0009] US 2021 / 0069630 A1 describes a filter element with a filter bellows that extends along a longitudinal axis and surrounds an interior space. The filter bellows is formed from a folded filter material arranged on a support tube. The filter bellows can be designed as a round element. End plates are arranged at a first end and an opposite second end of the filter element, which seal the filter bellows at its end edges. The filter bellows has an external notch at each of its ends, the axial length of which in the direction of the longitudinal axis is shorter than the longitudinal extent of the filter bellows. The notches are locally limited and do not extend over the entire length of the bellows. The notches preferably have the greatest pleat edge spacing at the respective end plates and taper with increasing distance from the end plate.The notches widen the distance between two adjacent pleats, with the pleats extending over the entire length of the bellows. The notches allow the filter element to be installed in the correct position in a housing. US 2019 / 0308125 A1 discloses a round filter element comprising a filter medium body whose wall allows the fluid to be cleaned to flow through in the radial direction. A circumferential seal carrier is arranged on or adjacent to one end face, which supports a positioning element for a positive connection with an associated counter-positioning element on the housing side.

[0010] EP 2 535 550 A2 describes a ring filter element, in particular for a filter device of a fresh air system of an internal combustion engine, with an annular filter body made of a folded web material. End folds adjoining one another in the circumferential direction are directly or indirectly connected to one another to form a connecting region suitable for aligning the rotational position of the filter element. A radially outwardly open longitudinal groove can be formed in the connecting region, which can be easily sensed, in particular, from the outside and, for example, enables forced alignment. Alternatively, a radially inwardly open longitudinal groove can also be formed in the connecting region. The respective groove base of the longitudinal groove can, for example, be formed by the adjoining end folds.An alignment contour is formed on a housing which interacts with the connecting area when the ring filter element is inserted in order to force a predetermined rotational position of the ring filter element within the housing.

[0011] The aforementioned WO 2015 / 092681 A1 describes a filter element with two layers of filter material made of folded paper, which has a cylindrical shape. The two layers of filter material are permanently held together by being embedded in plastic seals in certain areas. The seals can be arranged in the form of end discs on both ends of the filter element.

[0012] It is an object of the invention to ensure that two interlocking ring filter elements are correctly aligned with each other.

[0013] Disclosure of the invention

[0014] This object is achieved by a ring filter element arrangement according to claim 1 and a filter device according to claim 14. This object is also achieved by uses according to claims 23 to 25 and a ring filter element according to claim 26. Preferred embodiments are specified in the respective subclaims and the description.

[0015] According to the invention, a ring filter element arrangement is provided with a first ring filter element and a second ring filter element. For use, the ring filter element arrangement can be arranged in a filter housing. The ring filter element arrangement is designed, in particular, for air filtration. Preferably, the ring filter element arrangement is designed for filtering the intake air of a fuel cell. In particular, the ring filter element arrangement can be used as a cathode air filter of a fuel cell.

[0016] The first ring filter element and the second ring filter element each have a filter medium body that encloses an interior space. The two ring filter elements are thus closed in the circumferential direction. Flow can preferably pass through the two ring filter elements serially (one after the other). Flow can preferably pass through the ring filter element arrangement from radially outside to radially inside. Alternatively, flow can be provided from radially inside to radially outside.

[0017] The second ring filter element is at least partially accommodated in the interior of the filter medium body of the first ring filter element. In other words, the first ring filter element surrounds the second ring filter element at least in an axial portion. This results in a compact ring filter element arrangement. Typically, the two ring filter elements are arranged detachably against one another. They can then be replaced individually.

[0018] The first ring filter element is also referred to below as the outer ring filter element; accordingly, the second ring filter element is also referred to below as the inner ring filter element. The filter medium body of the first ring filter element is also referred to as the first or outer filter medium body; the filter medium body of the second ring filter element is also referred to as the second or inner filter medium body.

[0019] A longitudinal axis of the respective filter medium body can extend through its interior. In other words, the filter medium body can enclose the respective longitudinal axis in a ring-shaped manner. Preferably, a common longitudinal axis of the two ring filter elements extends through the interior of their filter medium bodies. In other words, the two filter medium bodies can be arranged coaxially to one another. Directional specifications such as radial or axial refer to the, in particular common, longitudinal axis. An angular position of the ring filter elements can also be determined with respect to the common longitudinal axis.

[0020] An outer circumferential surface of the filter medium body of the second ring filter element and an inner circumferential surface of the filter medium body of the first ring filter element adjoin one another in an interface region. The interface region thus comprises the region in which the first ring filter element surrounds the second ring filter element. "Adjoin one another" herein encompasses both a directly and indirectly adjacent arrangement of the first and second ring filter elements and explicitly does not require that the first and second ring filter elements touch one another, but rather also encompasses the possibility that additional element(s) can be arranged in the interface region between the first and second ring filter elements.

[0021] According to the invention, a positioning device for, in particular, unambiguous, relative angular positioning of the two ring filter elements relative to one another is arranged in the interface region. The positioning device thus ensures that a rotational alignment of the two ring filter elements relative to one another does not change. This ensures the correct alignment of the two ring filter elements relative to one another. In other words, the positioning device holds the two ring filter elements in a defined angular position relative to one another. In addition, the positioning device allows installation of the two ring filter elements only in one or more, for example up to four, relative angular positions. In particular, the positioning device can allow installation of the two ring filter elements only in a single (unambiguous) relative angular position and secure this angular position.Furthermore, the invention provides that the positioning device has an engagement element, wherein the engagement element extends radially inward and engages with a corresponding (second) counter-engagement element of the second ring filter element and / or wherein the engagement element extends radially outward and engages with a corresponding (first) counter-engagement element of the first ring filter element. In this way, the desired angular position of the two ring filter elements relative to one another can be positively defined and secured. During assembly, the correct alignment can be easily established by rotating the two ring filter elements until the engagement element can be inserted into the counter-engagement element(s).

[0022] The engagement element can have a projection or a rib which points radially outwards and / or inwards. The counter-engagement element on the respective ring filter element can in particular have a recess, a depression or a groove. The engagement element and the counter-engagement element can extend over the entire length or a partial region of the length of the respective ring filter element. In particular, the engagement element can be shorter in the axial direction than the corresponding counter-engagement element. The engagement element and the counter-engagement element are coordinated with one another (i.e. they correspond with one another) in such a way that deformation of these elements during assembly is only required to a small extent or preferably not at all, but at the same time only slight or preferably no rotational play occurs. The former reduces the required force and avoids damage.The latter ensures the defined rotational alignment of the two ring filter elements relative to each other. The rotational play with respect to a central position can, for example, be a maximum of + / - 5°, preferably a maximum of + / - 3°, and particularly preferably a maximum of + / - 1°.

[0023] If the engagement element engages a respective mating engagement element on both ring filter elements, the engagement element can typically be arranged fixedly to the housing. If the engagement element only engages a mating engagement element on one of the ring filter elements, the engagement element is generally arranged fixedly on the other ring filter element.

[0024] The first and / or second ring filter elements can have a hollow cylindrical shape. In particular, the two ring filter elements or their filter medium bodies can have a circular cross-section. Such ring filter elements can be manufactured efficiently and offer good space utilization. In certain embodiments, at least one of the ring filter elements can have an oval or long-oval cross-section. Alternatively or additionally, at least one of the ring filter elements can taper along its longitudinal axis. In other words, at least one of the ring filter elements can have an overall conical shape.

[0025] At least one of the filter medium bodies of the first and / or second ring filter element, preferably the filter medium body of the second ring filter element, can comprise an adsorbing gas filter medium, preferably containing activated carbon. In other words, the filter medium of at least one of the filter medium bodies can comprise an adsorbent. In this way, harmful gases can be removed from the air stream to be filtered and bound in the filter medium body. The filter medium body of the first ring filter element can comprise a (first) bellows. The first bellows or the first filter medium body can, in particular, be formed by a star-shaped pleated filter medium.

[0026] Alternatively or additionally, the filter medium body of the second ring filter element can have a (second) bellows. The second bellows or the second filter medium body can, in particular, be formed by a star-shaped pleated filter medium.

[0027] At least one fold of the bellows of the first ring filter element can protrude radially inward further on the inner circumferential surface than adjacent folds of the bellows in the circumferential direction, wherein the protruding fold at least co-forms the engagement element and engages with the counter-engagement element of the second ring filter element. In other words, the radially inner fold edges of a plurality of folds can have the same distance from the longitudinal axis, whereas the radially inner fold edges of one or more adjacent folds have a smaller distance from the longitudinal axis. In this way, the engagement element can be integrated into the bellows by simply varying the folding pattern.

[0028] The engagement element can be arranged on a central tube, which is located in the interface region. The central tube thus extends between the outer circumferential surface of the second ring filter element and the inner circumferential surface of the first ring filter element. The engagement element is preferably integral with the central tube.

[0029] In a preferred embodiment, the first ring filter element has a central tube fixed to the element, which is arranged on the inner circumferential surface of the filter medium body of the first ring filter element and is attached directly or indirectly to the filter medium body of the first ring filter element, wherein the engagement element is arranged on the central tube, in particular is integral with the central tube, and wherein the engagement element extends radially inward and engages with the counter-engagement element of the second ring filter element. On the one hand, the central tube supports the filter medium body of the outer ring filter element. On the other hand, the central tube effects the defined rotational alignment of the inner ring filter element relative to the outer ring filter element.

[0030] In an alternative embodiment, the ring filter element arrangement comprises a central tube that is detachably arranged in the interface region and, in a properly assembled state, can be arranged fixedly to the filter housing. The engagement element is arranged on the central tube that is fixed to the housing and extends both radially inward into the counter-engagement element of the second ring filter element and radially outward into the counter-engagement element of the first ring filter element. In this embodiment, the central tube is fastened to the filter housing, at least in the assembled state, preferably in a defined angular position. For example, the central tube can be rusted to the filter housing. The central tube can be permanently connected to a housing part of the filter housing. The two ring filter elements can be detachably arranged on the central tube. This can simplify the manufacture of the ring filter elements.When assembled, the two ring filter elements are rotationally aligned relative to the center tube by the engagement element engaging the respective mating engagement elements of both ring filter elements. If the support tube is attached to the filter housing at a defined angular position, the two filter elements are also angularly positioned relative to the filter housing via the center tube when assembled.

[0031] If the engagement element is arranged on a center tube, particularly in the two aforementioned embodiments, the center tube can have a recess on its end face for engagement with an axial projection fixed to the housing, in particular wherein the recess is formed in the region of the engagement element. In this way, a defined rotational alignment of the center tube with respect to the filter housing can be achieved. The center tube then aligns both the two ring filter elements in their angular position relative to one another and the two ring filter elements (angle-positioned relative to one another) together in their angular position relative to the filter housing. The alignment of the ring filter elements is then completely defined, which simplifies, for example, the calibration of air mass meters.

[0032] If the filter medium body of the first ring filter element has a bellows, the engagement element on the inner circumferential surface of the filter medium body of the first ring filter element can engage in a space between two adjacent folds of the bellows. In this respect, the space between the adjacent folds forms the counter-engagement element. This reduces the effort required to provide the counter-engagement element on the first filter medium body. This embodiment is particularly suitable if the engagement element is formed on a central tube that can be arranged fixedly to the housing and engages both ring filter elements. In particular, the counter-engagement element of the first ring filter element can be formed with a pleat spread. In other words, in the region of the engagement of the engagement element in the outer filter medium body, at least one fold of the bellows thereof is provided with a pleat spread.This creates space for the engagement of an engagement element that is wider in the circumferential direction. Furthermore, the locally present pleat spreading results in a defined angular position of the first ring filter element relative to the engagement element. A pleat angle and / or pleat spacing (distance measured in the circumferential direction from radially inner fold edges) can be larger in the area of ​​the pleat spreading on the inner surface of the outer ring filter element than with a plurality of pleats in the bellows. In particular, all pleats can have the same pleat angle or pleat spacing, apart from the area of ​​the pleat spreading.

[0033] If the filter medium body of the second ring filter element has a bellows, the engagement element on the outer circumferential surface of the filter medium body of the second ring filter element can engage in a space between two adjacent folds of the bellows. In this respect, the space between the adjacent folds forms the counter-engagement element. This reduces the effort required to provide the counter-engagement element on the second filter medium body. In particular, the counter-engagement element of the second ring filter element can be formed with a pleat spread. In other words, in the region of the engagement of the engagement element in the inner filter medium body, at least one fold of the bellows is provided with a pleat spread. This creates space for the engagement of an engagement element that is wider in the circumferential direction.In addition, the locally present pleat spreading results in a defined angular position of the second ring filter element relative to the engagement element. A pleat angle and / or pleat spacing (distance measured in the circumferential direction from the radially outer fold edges) can be larger in the area of ​​the pleat spreading on the outer surface of the inner ring filter element than with a plurality of pleats in the bellows. In particular, all pleats—apart from the area of ​​the pleat spreading—can have the same pleat angle or pleat spacing.

[0034] The first and / or the second ring filter element can have at least one end plate which sealingly delimits the respective filter medium body in the axial direction. The end plates can also seal the two ring filter elements against each other and / or against the filter housing. At one axial end, the end plate of at least one of the ring filter elements can be closed; in particular, the two end plates can be closed at one axial end. At the other axial end, both end plates are typically open (i.e., provided with a central opening). The end plates can be cast or glued onto the filter medium body. The end plates can be made, for example, of polyurethane, in particular polyurethane foam.

[0035] The counter-engagement element can be formed with a recess in the end plate of the first and / or second ring filter element. If a pleat spread is provided, the recess in the end plate can be aligned with the pleat spread. The recess in the end plate simplifies the arrangement of the respective ring filter element on the engagement element.

[0036] Also within the scope of the present invention is a filter device comprising a filter housing with at least one fluid inlet and at least one fluid outlet, and further comprising a ring filter element arrangement according to the invention as described above, which is arranged in the filter housing and separates the fluid inlet from the fluid outlet. The advantages of the ring filter element arrangement can be utilized in the filter device.

[0037] The filter device can have a central tube attached, in particular permanently attached, to the filter housing. An engagement element is arranged on the housing-fixed central tube, which extends both radially inward into the mating engagement element of the second ring filter element and radially outward into the mating engagement element of the first ring filter element. The central tube engages in the interface area between the two ring filter elements and aligns them relative to one another and preferably also relative to the filter housing.

[0038] The filter housing can have a first housing positioning device for, in particular, the clear, relative angular positioning of the first ring filter element relative to the filter housing, wherein the first housing positioning device has a first housing engagement element that extends radially inward and engages with a corresponding housing counter-engagement element of the first ring filter element. In this way, the outer ring filter element can be aligned and fixed relative to the filter housing. The inner ring filter element is then aligned relative to the filter housing at least via the positioning device acting between the two ring filter elements—indirectly via the outer ring filter element. This results in a completely angularly positioned arrangement of the ring filter element arrangement in the filter housing.In addition, the first housing engagement element ensures that only matching first ring filter elements can be used with a housing counter-engagement element. If the filter medium body of the first ring filter element has a bellows, the first housing engagement element can engage on the outer circumferential surface of the filter medium body of the first ring filter element in a space between two adjacent folds of the bellows. In this respect, the space between the adjacent folds forms the housing counter-engagement element. This reduces the effort required to provide the housing counter-engagement element on the first filter medium body. In particular, the housing counter-engagement element of the first ring filter element can be formed with a pleat spread. In other words, in the region of the engagement of the first housing engagement element in the outer filter medium body, at least one fold of the bellows is provided with a pleat spread.This creates space for the engagement of a housing engagement element that is wider in the circumferential direction. Furthermore, the locally present pleat spreading results in a defined angular position of the first ring filter element relative to the first housing engagement element. A pleat angle and / or pleat spacing (distance measured in the circumferential direction from radially outer fold edges) can be larger in the area of ​​the pleat spreading on the outer surface of the outer ring filter element than with a plurality of pleats in the bellows; in particular, apart from the area of ​​the pleat spreading, all pleats can have the same pleat angle or pleat spacing.

[0039] If at least one fold of the bellows of the first ring filter element protrudes radially inward further on the inner surface than circumferentially adjacent folds of the bellows, and the protruding fold at least co-forms the engagement element and engages with the counter-engagement element of the second ring filter element, the first housing engagement element can engage with the fold protruding radially inward further. Preferably, the first housing engagement element extends radially inward into the counter-engagement element of the second ring filter element. The first housing engagement element then defines the angular position of both ring filter elements by engaging with their respective housing counter-engagement element or counter-engagement element. In this case, the engagement element of the first ring filter element also engages with the counter-engagement element of the second ring filter element.Thus, both the engagement element of the first ring filter element and the first housing engagement element engage in the counter engagement element of the second ring filter element.

[0040] The filter housing can have a second housing positioning device for, in particular, the clear, relative angular positioning of the second ring filter element relative to the filter housing, wherein the second housing positioning device has a second housing engagement element that extends radially outward and engages with a corresponding housing counter-engagement element of the second ring filter element. In this way, the inner ring filter element can be aligned and fixed relative to the filter housing. The outer ring filter element is then aligned relative to the filter housing at least via the positioning device acting between the two ring filter elements—indirectly via the inner ring filter element. This results in a completely angularly positioned arrangement of the ring filter element arrangement in the filter housing.In addition, the second housing engagement element ensures that only matching second ring filter elements can be used with a housing counter-engagement element. The filter device can have a support tube that is fastened to the filter housing, in particular non-detachably fastened, and that engages into the interior of the filter medium body of the second ring filter element, wherein the second housing engagement element is arranged on the support tube, in particular is integral with the support tube. On the one hand, the support tube supports the filter medium body of the inner ring filter element. On the other hand, the support tube effects the defined rotational alignment of the inner ring filter element relative to the filter housing. For this purpose, the support tube can be fastened to the filter housing in a defined angular position.The support tube is generally arranged detachably in the interior of the second ring filter element in order to enable replacement of the ring filter element arrangement, in particular the second ring filter element.

[0041] If the filter medium body of the second ring filter element has a bellows, the second housing engagement element can engage on the inner circumferential surface of the filter medium body of the second ring filter element in a space between two adjacent folds of the bellows. In this respect, the space between the adjacent folds forms the housing counter-engagement element. This reduces the effort required to provide the housing counter-engagement element on the second filter medium body. In particular, the housing counter-engagement element of the second ring filter element can be formed with a pleat spread. In other words, in the region of the engagement of the second housing engagement element in the inner filter medium body, at least one fold of its bellows is provided with a pleat spread. This creates space for the engagement of a circumferentially wider housing engagement element.In addition, the locally present pleat spreading results in a defined angular position of the second ring filter element relative to the second housing engagement element. A pleat angle and / or pleat spacing (distance measured in the circumferential direction from radially inner pleat edges) can be larger in the area of ​​the pleat spreading on the inner surface of the inner ring filter element than with a plurality of pleats in the bellows. In particular, all pleats—apart from the area of ​​the pleat spreading—can have the same pleat angle or pleat spacing.

[0042] The filter housing can have an axial projection that engages in a frontal recess of a center tube, on which center tube the engagement element is arranged. This ensures that only suitable center tubes are used. If the center tube is firmly connected to one of the ring filter elements, in particular the outer ring filter element, the use of a suitable ring filter element is simultaneously ensured. Furthermore, the engagement of the axial projection in the recess ensures that the center tube is aligned in a defined angular position on the filter housing. The two ring filter elements are also aligned in a defined angular position on the filter housing via the center tube and its engagement element.

[0043] The invention also relates to the use of a filter device according to the invention described above as a cathode air filter of a fuel cell.

[0044] The present invention further includes a fuel cell having an anode and a cathode, between which an electrolyte is arranged, and having a filter device according to the invention described above, through which air can be conducted to the cathode. Fuel cells often require two-stage filtration of the air supplied to the cathode, particularly where harmful gases as well as particles are to be retained. Furthermore, angular positioning of the ring filter elements for precise metering of the supplied air by means of an air mass meter in fuel cells is advantageous for their efficiency. The filter device according to the invention enables this through its advantageous design described above.

[0045] Also within the scope of the present invention is the use of a ring filter element comprising a filter medium body enclosing an interior space and having a counter-engagement element on its inner circumferential surface as the first ring filter element of a filter device according to the invention as described above, wherein the engagement element of the positioning device extends radially outward into the counter-engagement element of the first ring filter element. Through the engagement of the engagement element in the counter-engagement element of the (first) ring filter element, the latter is angularly positioned relative to the second ring filter element, in particular unambiguously. In other words, the two ring filter elements are angularly positioned relative to one another.

[0046] Furthermore, the scope of the present invention includes the use of a ring filter element comprising a filter medium body enclosing an interior space and having a counter-engagement element on its outer surface as the second ring filter element of a filter device according to the invention described above, wherein the engagement element of the positioning device extends radially inward into the counter-engagement element of the second ring filter element. Through the engagement of the engagement element in the counter-engagement element of the (second) ring filter element, the latter is angularly positioned relative to the first ring filter element, in particular unambiguously. In other words, the two ring filter elements are angularly positioned relative to one another.

[0047] Finally, the scope of the present invention includes a ring filter element for a filter device according to the invention as described above. The ring filter element comprises a filter medium body enclosing an interior space, wherein the filter medium body comprises a bellows provided with a pleat spread on an inner surface. The bellows or the filter medium body can, in particular, be formed by a star-shaped pleated filter medium.

[0048] If the ring filter element is a first ring filter element for the filter device, the pleat spreading forms at least one counter-engagement element for engagement of an engagement element of a positioning device for the relative angular positioning of the first ring filter element with respect to a second ring filter element.

[0049] If the ring filter element is a second ring filter element for the filter device, the pleat spreading forms a housing counter-engagement element for engaging a housing engagement element of a housing positioning device for the relative angular positioning of the ring filter element with respect to the filter housing at least.

[0050] The ring filter element can have at least one open end plate that sealingly defines the filter medium body in the axial direction. The end plate has at least one recess on an inner circumference that is aligned with the pleat spread. The end plate with the recess typically borders the pleat spread. The recess and the pleat spread then jointly form the counter-engagement element or the housing counter-engagement element. At the other axial end, the ring filter element can have another open or, preferably, a closed end plate that sealingly defines the filter medium body in the axial direction.

[0051] According to yet another embodiment, the second ring filter element can have a central tube fixed to the element, which is arranged on the inner circumferential surface of the filter medium body of the second ring filter element and is directly or indirectly attached to the filter medium body of the second ring filter element. The central tube of the second ring filter element can, in particular, have a recess on the end face for engagement with a further axial projection fixed to the housing. This enables further positioning, in particular with regard to the angular position, of the ring filter element arrangement relative to the housing.

[0052] Short description of the drawings

[0053] Further features and advantages of the invention will become apparent from the following detailed description of exemplary embodiments of the invention, from the patent claims, and from the figures of the drawing, which illustrate details of the invention. The aforementioned and further detailed features can be implemented individually or in combination in any desired, expedient combinations in variants of the invention. The features shown in the drawing are presented in such a way that the special features of the invention can be clearly seen. In the drawing:

[0054] Fig. 1 shows a first embodiment of a filter device according to the invention with a ring filter element arrangement according to the invention comprising an outer and an inner ring filter element, in a schematic longitudinal section;

[0055] Fig. 2 shows the outer ring filter element of the filter device of Figure 1, in a schematic longitudinal section;

[0056] Fig. 3 shows the inner ring filter element of the filter device of Figure 1, in a schematic longitudinal section;

[0057] Fig. 4 is a schematic cross-section through the filter device of Figure 1;

[0058] Fig. 5 is an enlarged section of Figure 4;

[0059] Fig. 6 is an enlarged section of Figure 1;

[0060] Fig. 7 shows a second embodiment of a filter device according to the invention with a ring filter element arrangement according to the invention comprising an outer and an inner ring filter element, in a schematic longitudinal section;

[0061] Fig. 8a shows the filter device of Figure 7 in a schematic, partially sectioned cross-sectional view along section line BB;

[0062] Fig. 8b shows an enlarged section of Figure 8a;

[0063] Fig. 9 shows a lower housing part of the filter device of Fig. 7, in a schematic perspective view;

[0064] Fig. 10 shows the outer ring filter element of the filter device of Figure 7, in a schematic cross-section; Fig. 11 shows the inner ring filter element of the filter device of Figure 7, in a schematic perspective view;

[0065] Fig. 12 shows a second ring filter element for a filter device similar to that of Figure 1, in a schematic longitudinal section, wherein a counter-engagement element is formed in the region of an open end plate;

[0066] Fig. 13 shows a third embodiment of a filter device according to the invention with a ring filter element arrangement according to the invention comprising an outer and an inner ring filter element, in a schematic cross-section which is stepped, so that a positioning device between the ring filter elements and a housing positioning device on the outer ring filter element can be seen, although they are arranged at different axial ends;

[0067] Fig. 14 shows a section of the filter device of Fig. 13 in the area of ​​the housing positioning device, in a schematic cross-section;

[0068] Fig. 15 shows a section of the outer ring filter element of the filter device of Fig. 13, in a schematic longitudinal section;

[0069] Fig. 16 shows a fourth embodiment of a filter device according to the invention with a ring filter element arrangement according to the invention comprising an outer and an inner ring filter element, in a schematic cross section;

[0070] Fig. 17 shows an enlarged section of Figure 16;

[0071] Fig. 18 shows a section of the filter device of Fig. 16, in a schematic longitudinal section;

[0072] Fig. 19 shows a first ring filter element of the filter device of Fig. 16, in a schematic longitudinal section;

[0073] Fig. 20 shows a fifth embodiment of a filter device according to the invention with a ring filter element arrangement according to the invention comprising an outer and an inner ring filter element, in a schematic cross-section which is stepped, so that a positioning device between the ring filter elements and a first housing positioning device on the outer ring filter element as well as a second housing positioning device on the inner ring filter element can be seen, although they are arranged at different axial ends;

[0074] Fig. 21 is an enlarged section of Figure 20;

[0075] Fig. 22 shows a section of the filter device of Figure 20, in a schematic longitudinal section, in the region of the second housing positioning device on an open end plate of the inner ring filter element;

[0076] Fig. 23a shows a section of the filter device of Figure 20, in a schematic longitudinal section, in the region of closed end plates with the positioning device between the two ring filter elements and the first housing positioning device;

[0077] Fig. 23b is a longitudinal section of an alternative to Fig. 23a, wherein the second ring filter element has a central tube fixed to the element, which has a front-side recess for engagement of a further axial projection fixed to the housing;

[0078] Fig. 24 shows the second ring filter element of the filter device of Fig. 20, in a schematic perspective view;

[0079] Fig. 25 shows a second ring filter element according to the invention for a filter device according to the invention, in a schematic perspective view; Fig. 26 shows a sixth embodiment of a ring filter element arrangement according to the invention, comprising an outer and an inner ring filter element, in a schematic longitudinal section;

[0080] Fig. 27 shows the filter device of Figure 26, in a schematic longitudinal section with the cutting plane rotated by 90° compared to Figure 26;

[0081] Fig. 28 shows a seventh embodiment of an inventive ring filter element arrangement having an outer and an inner ring filter element, in a schematic longitudinal section;

[0082] Fig. 29 shows the filter device of Figure 28, in a schematic longitudinal section with the cutting plane rotated by 90° compared to Figure 28;

[0083] Fig. 30 is a schematic diagram of an inventive use of a filter device according to the invention as a cathode air filter of a fuel cell.

[0084] Embodiments of the invention

[0085] Figure 1 shows a filter device 10.1, here in the form of an air filter. A filter housing 12 of the filter device 10.1 has an upper housing part 14 and a lower housing part 16, which are releasably attached to one another. A ring filter element arrangement 20 is accommodated in the filter housing 12. The ring filter element arrangement 20 separates a fluid inlet 22 for unfiltered air from a fluid outlet 24 for filtered air. The fluid inlet 22 and the fluid outlet 24 are formed here, for example, on the upper housing part 14.

[0086] The ring filter element arrangement 20 comprises a first or outer ring filter element 26 (see also Figure 2) and a second or inner ring filter element 28 (see also Figure 3), through which flow can pass in series from the radial outside to the radial inside. The two ring filter elements 26, 28 each have a filter medium body 30 or 32, which encloses a respective interior space 34 or 36. The filter medium bodies 30, 32 are each hollow-cylindrical with a circular cross-section. An outer surface of the first filter medium body 30 is provided with the reference numeral 38, and an inner surface of the first filter medium body 30 is provided with the reference numeral 40. An outer surface of the second filter medium body 32 is provided with the reference numeral 42, and an inner surface of the second filter medium body 32 is provided with the reference numeral 44.

[0087] In the assembled state, the two ring filter elements 26, 28 are arranged coaxially to one another, see Figure 1 and Figure 4. Longitudinal axes 46a, 46b of the filter medium bodies 30, 32 extending through the respective interior spaces 34, 36 coincide in a common longitudinal axis 46.

[0088] The two filter medium bodies 30, 32 are each designed as a bellows, which is obtained by folding a flat filter medium in a star-shaped manner. Some of the respective folds are shown in Figure 4. The filter medium, in particular of the second ring filter element 28 arranged downstream in the flow direction, can contain an adsorbent, for example activated carbon, in order to remove harmful gases from the air stream to be filtered. The axial end faces of the two filter medium bodies 30, 32 are each sealed by an end plate 48, 50, 52, 54. In the present case, closed end plates 50, 54 are provided at one end. Open end plates 48, 52 are provided at the other end, on the one hand to enable the inner ring filter element 28 to be inserted into the outer ring filter element 26, and on the other hand to enable the filtered air to escape through the fluid outlet 24.Here, the open end plates 48, 52, in the assembled state, each lie sealingly against the upper housing part 14.

[0089] On the inner circumference, the first ring filter element 26 has a central tube 56, which is embedded at its axial ends in the two end plates 48, 50. The central tube 56 is thus an integral part of the first ring filter element 26.

[0090] As already indicated above, the second ring filter element 28 is accommodated (here over the majority of its longitudinal extent) in the first ring filter element 26, see Figure 1. In other words, the first filter medium body 30 surrounds the second filter medium body 32, see also Figure 4. An annular gap is formed between the inner surface 40 of the first filter medium body 30 and the outer surface 42 of the second filter medium body 32. The region between the inner surface 40 of the first filter medium body 30 and the outer surface 42 of the second filter medium body 32 is also referred to as an interface region 58 in the context of the present invention.

[0091] A positioning device 60 acts between the first and second ring filter elements 26, 28, which holds the two ring filter elements 26, 28 relative to one another in a defined angular position (rotational position) with respect to the longitudinal axis 46, see Figures 1 and 4. The positioning device 60 has an engagement element 62, which is arranged in the interface region 58 between the two ring filter elements 26, 28, see also Figure 5.

[0092] In this embodiment, the engagement element 62 is a radially inwardly pointing projection on the center tube 56 of the outer (first) ring filter element 26, see also Figure 2. The engagement element 62 and the center tube 56 are here designed integrally with one another as a common injection-molded part.

[0093] The inner (second) ring filter element 28 has at least one corresponding counter-engagement element 64. The counter-engagement element 64 is formed here by a recess 65 in the closed end plate 54 (see in particular Figure 3) and a pleat spread 66 on the outer surface 42 of the star-folded filter medium body 32 (see in particular Figure 5). The recess 65 and the pleat spread 66 are aligned with one another, see in particular Figure 3.

[0094] In the area of ​​the pleat spread 66, a pleat spacing, measured in the circumferential direction, between radially outer fold edges 68 of the second filter medium body 32 is increased compared to the pleat spacing of adjacent outer fold edges 68. Here, the pleat spread 66 is limited to a single outwardly open fold. Due to the pleat spread 66, a pleat angle 70 is also increased compared to the adjacent folds. In this case, the pleat spread 66 does not extend over the entire axial length of the second filter medium body 32, but is limited to less than one-third of its total length.

[0095] The engagement element 62 extends into the counter-engagement element 64. In particular, the engagement element 62 engages in the radial direction between the two spread outer folded edges 68, see in particular Figure 5. In addition, the engagement element 62 engages in the radial direction into the recess 65 of the end plate 54, see in particular Figure 6, which shows detail X from Figure 1.

[0096] In the filter device 10.1, the positioning device 60 is arranged in the region of the closed end plates 50, 54. It is understood that, in a modified embodiment, the positioning device 60 could also be arranged in a corresponding manner in the region of the open end plates 48, 52, see Figure 12, which shows a corresponding second ring filter element 28. Here, a recess 65' of the counter-engagement element 64 is formed in the open end plate 52. A pleat spread 66 adjoins the recess 65' below the end plate 52, flush with the recess, and extends over less than one-third of the axial length of the filter medium body 32.

[0097] In the filter device 10.1, the engagement element 62 has a recess 72 on its end face (in the region of the end plate 50), see Figures 2 and 6. The otherwise closed end plate 50 is also perforated in the region of the recess 72. However, the engagement element 62 is fluid-tight and sealingly embedded in the end plate 54, so that the first ring filter element 26 remains sealed at the bottom.

[0098] A housing-fixed axial projection 74, which here is formed integrally with the housing lower part 16, engages in the recess 72 of the engagement element 62, see Figures 1 and 6. In other words, the axial projection 74 extends through the end plate 54 into the hollow engagement element 62.

[0099] The engagement of the axial projection 74 into the recess 72 of the engagement element 62 establishes a defined angular position of the first ring filter element 26 relative to the filter housing 12. Through the engagement of the engagement element 62 into the counter-engagement element 64 of the second ring filter element 28, the second ring filter element 28 is also angularly positioned relative to the filter housing 12 (indirectly via the first ring filter element 26). The engagement element 62, which is firmly connected to the first ring filter element 26, thus effects an angular positioning of the two ring filter elements 26, 28 of the ring filter element arrangement 20 relative to one another, as well as of the ring filter element arrangement 20 as a whole relative to the filter housing 12.

[0100] A support tube 76 which can be arranged fixedly to the housing, for example, which can be locked to the upper housing part 14, can support the second ring filter element 28 radially inwardly on its inner circumferential surface 44, see Figure 1 .

[0101] Figure 7 shows a second filter device 10.2. The filter device 10.2 of Figure 7 corresponds in many aspects to the filter device 10.1 shown in Figures 1 to 6 and described above. The differences are primarily explained below; otherwise, reference is made to the above description. The filter device 10.2 also has a ring filter element arrangement 20 with two ring filter elements 26, 28 arranged coaxially to a common longitudinal axis 46 in a filter housing 12 (see also Figure 8a). Here, too, filter medium bodies 30, 32 of the two ring filter elements 26, 28 are formed by star-shaped folded filter bellows. Also as described above, the second (inner) ring filter element 28 has a counter-engagement element 64 which comprises a recess 65 in a closed end plate 54 and a pleat spreading 66 on the outer circumferential surface 42, see also Figure 11 .Here, the pleat spread 66 extends over the entire axial length of the second filter medium body 32, up to an open end plate 52.

[0102] On the inner circumferential surface 40 of the first (outer) ring filter element 26, a radially inner folded edge 78a projects into the interior space 34 beyond the adjacent radially inner folded edges 78b, see Figure 10. In the present case, all inner folded edges 78b have the same distance from the longitudinal axis 46a, whereas the distance of the projecting folded edge 78a from the longitudinal axis 46a is smaller.

[0103] A central tube 56, which is firmly connected to the first ring filter element 26, has a radially inward projection 80 in the region of the radially inwardly projecting fold. The central tube 56 thus follows the contour of the inner surface 40 of the first filter medium body 30.

[0104] The protruding folded edge 78a and the projection 80 together form an engagement element 62 of the first ring filter element 26. Here, the engagement element 62 extends over the entire axial length of the first filter medium body 30.

[0105] In the assembled state, the engagement element 62 of the first ring filter element 26 engages the counter-engagement element 64 of the second ring filter element 28, see Figures 7 and 8b. Both the projection 80 of the center tube 56 and the protruding folded edge 78a of the filter medium body 30 extend radially inward into the pleat spread 66 of the second filter medium body 32. Thus, the two ring filter elements 26, 28 are aligned in a defined angular position relative to one another.

[0106] In order to align the ring filter element arrangement 20 relative to the filter housing 12 in its angular position with respect to the longitudinal axis 46, a (first) housing positioning device 82 is provided in the filter device 10.2 (see Figures 7 and 8a). The housing positioning device 82 has a first housing engagement element 84. The housing engagement element 84 is designed here in the form of a wedge-shaped rib, which, for example, is integral with the housing lower part 16 (see Figures 7 and 8a / 8b and in particular Figure 9). In the present case, the housing engagement element 84 tapers upwards and protrudes radially inwards to a lesser extent. In the axial direction, the height of the housing engagement element 84 is limited to less than a quarter of the length of the first filter medium body 30.

[0107] The housing engagement element 84 engages with a (first) housing counter-engagement element 86 on the first ring filter element 26. The first housing counter-engagement element 86 here comprises a pleat spread 88 on the outer circumferential surface 38 of the first filter medium body 30 and a recess 90 in its closed end plate 50, see in particular Figures 7, 8a / 8b, 10 and 15. In the region of the pleat spread 88, a pleat spacing, measured in the circumferential direction, between radially outer fold edges 92 of the first filter medium body 30 is increased compared to the pleat spacing of adjacent, outer fold edges 92. Here, the pleat spread 88 is limited to a single outwardly open fold. Due to the pleat spread 88, a pleat angle 94 is also increased compared to the adjacent folds. In the present case, the pleat spreading 88 extends over the entire axial length of the first filter medium body 30.

[0108] The radially inwardly projecting folded edge 78a of the first ring filter element 26 can extend inwardly so far that the housing engagement element 84 can also extend into the counter-engagement element 64 of the second ring filter element 28, see Figures 7 and 8b. In particular, the housing engagement element 84 can engage radially inwardly into the recess 65 of the end plate 54 and / or into the pleat spread 66.

[0109] Figure 13 shows a third filter device 10.3. The filter device 10.3 of Figure 13 corresponds in many aspects to the filter device 10.1 shown in Figures 1 to 6 and described above. The differences are primarily explained below; otherwise, reference is made to the above description.

[0110] The filter device 10.3 also has a ring filter element arrangement 20 with two ring filter elements 26, 28 arranged coaxially to a common longitudinal axis 46 in a filter housing 12. Here, too, the filter medium bodies 30, 32 of the two ring filter elements 26, 28 are formed by star-shaped folded filter bellows. As with the filter device 10.1, the filter device 10.3 includes a positioning device 60 between the two ring filter elements 26, 28 with an engagement element 62 in the form of a radially inwardly facing projection on a central tube 56 firmly connected to the outer ring filter element 26. The engagement element 62 engages a counter-engagement element 64 on the inner ring filter element 28, which here, too, is formed with a pleat spread 66 on the outer circumferential surface 42 of the second filter medium body 32 (see also Figure 5 in this respect).In addition, the counter-engagement element 64 can have a recess 65 or 65' aligned with the fold spread 66, on the closed end plate 54 or on the open end plate 52 (see also Figures 3 and 12).

[0111] In the filter device 10.3 (similar to the filter device 10.2 of Figure 7), a first housing positioning device 82 is also provided, which aligns the first ring filter element 26 relative to the filter housing 12 in a defined angular position with respect to the longitudinal axis 46.

[0112] The housing positioning device 82 has a first housing engagement element 84. The housing engagement element 84 is also designed here in the form of a wedge-shaped rib, which, for example, can be integral with the housing lower part 16 (see also Figure 9 and Figure 14). Here, too, the housing engagement element 84 tapers upwards and protrudes radially inward to a lesser extent. In the axial direction, the height of the housing engagement element 84 is limited to less than a quarter of the length of the first filter medium body 30. The housing engagement element 84 engages a (first) housing counter-engagement element 86 on the first ring filter element 26. The first housing counter-engagement element 86 also comprises a pleat spreading 88 on the outer surface 38 of the first filter medium body 30 and a recess 90 in its closed end plate 50, see also Figure 15.Here, the pleat spreading 88 does not extend over the entire axial length of the first filter medium body 30, but is limited to less than one third of its total length.

[0113] In the area of ​​the pleat spread 88, a pleat spacing measured in the circumferential direction between radially outer fold edges 92 of the first filter medium body 30 is increased compared to the pleat spacing of adjacent outer fold edges 92, see Figure 13. Here, the pleat spread 88 is limited to a single outwardly open fold. Due to the pleat spread 88, a pleat angle 94 is also increased compared to the adjacent folds, see also Figure 10.

[0114] Figure 16 shows a fourth filter device 10.4. The filter device 10.4 of Figure 16 corresponds in many aspects to the filter device 10.1 shown in Figures 1 to 6 and described above. The differences are primarily explained below; otherwise, reference is made to the above description.

[0115] The filter device 10.4 also has a ring filter element arrangement 20 with two ring filter elements 26, 28 arranged coaxially to a common longitudinal axis 46 in a filter housing 12. Here, too, the filter medium bodies 30, 32 of the two ring filter elements 26, 28 are formed by star-shaped folded filter bellows. Also as described above, the second (inner) ring filter element 28 has a counter-engagement element 64, which includes a recess 65' in an open end plate 52 and a pleat spread 66 on the outer circumferential surface 42 (see also Figure 12).

[0116] In the filter device 10.4, an engagement element 62 of a positioning device 60 is formed on a central tube 96 rigidly connected to the filter housing 12 (see also Figure 18). The central tube 96 can, for example, be locked in a fixed angular position with the housing upper part 14. This angular position can be defined by the engagement of an axial projection fixed to the housing in a frontal recess on the central tube (not shown in detail). The two ring filter elements 26, 28 can be pushed onto the central tube 96 for assembly and pulled off the central tube 96 for disassembly.

[0117] The engagement element 62 protrudes, on the one hand, radially inward into the counter-engagement element 64 of the second ring filter element 28. This fixes an angular position of the second ring filter element 28 with respect to the longitudinal axis 46 relative to the filter housing 12. On the other hand, the engagement element 62 protrudes radially outward into a further counter-engagement element 98 of the first ring filter element 26. This fixes an angular position of the first ring filter element 26 with respect to the longitudinal axis 46 relative to the filter housing 12. Since the engagement element 62 of the center tube 96 engages the counter-engagement elements 64, 98 of both filter elements 26, 28, they are also fixed relative to one another with respect to the longitudinal axis 46 in a defined angular position; this also applies if the center tube is rotatably mounted on the filter housing 12.The counter-engagement element 98 of the first ring filter element 26 comprises a recess 100, which here is formed radially inward on the open end plate 48, see also Figure 19. In addition, the counter-engagement element 98 comprises a pleat spread 102, aligned with the recess 100, on the inner circumferential surface 40 of the first filter medium body 30. Here, the pleat spread 88 does not extend over the entire axial length of the first filter medium body 30, but is limited to less than one third of its entire length.

[0118] In the area of ​​the pleat spread 102, a pleat spacing, measured in the circumferential direction, between radially inner fold edges 104 of the first filter medium body 30 is increased compared to the pleat spacing of adjacent inner fold edges 104, see in particular Figure 17. Here, the pleat spread 102 is limited to a single inwardly open fold. Due to the pleat spread 102, a pleat angle 106 is also increased compared to the adjacent folds.

[0119] Figure 20 shows a fifth filter device 10.5. The filter device 10.5 of Figure 20 corresponds in many aspects to the filter device 10.1 shown in Figures 1 to 6 and described above. The differences are primarily explained below; otherwise, reference is made to the above description.

[0120] The filter device 10.5 also has a ring filter element arrangement 20 with two ring filter elements 26, 28 arranged coaxially to a common longitudinal axis 46 in a filter housing 12. Here, too, the filter medium bodies 30, 32 of the two ring filter elements 26, 28 are formed by star-shaped folded filter bellows. As with the filter device 10.1, the filter device 10.5 includes a positioning device 60 between the two ring filter elements 26, 28 with an engagement element 62 in the form of a radially inwardly facing projection on a central tube 56 firmly connected to the outer ring filter element 26 (see also Figure 23a). The engagement element 62 engages in a counter-engagement element 64 on the inner ring filter element 28, which is also formed here with a pleat spread 66 on the outer surface 42 of the second filter medium body 32 (see also Figure 5).In addition, the counter-engagement element 64 has a recess 65 on the closed end plate 54 that is aligned with the fold spread 66, see Figure 24.

[0121] Similar to the filter device 10.3 of Figure 13, a first housing positioning device 82 is provided, which aligns the first ring filter element 26 relative to the filter housing 12 in a defined angular position with respect to the longitudinal axis 46 (see Figures 20 and 23). The housing positioning device 82 has a first housing engagement element 84, which here too is designed in the form of a wedge-shaped rib, which, for example, can be integral with the housing lower part 16 (see also Figure 9). Here, too, the first housing engagement element 84 tapers upwards and protrudes radially inward to a lesser extent. In the axial direction, the height of the first housing engagement element 84 is limited to less than a quarter of the length of the first filter medium body 30.

[0122] The first housing engagement element 84 engages with a (first) housing counter-engagement element 86 on the first ring filter element 26. Here, the first housing counter-engagement element 86 also comprises a pleat spread 88 on the outer circumferential surface 38 of the first filter medium body 30 and a recess 90 in its closed end plate 50, see Figure 23a and additionally Figure 15. Here, the pleat spread 88 does not extend over the entire axial length of the first filter medium body 30, but is limited to less than one-third of its total length.

[0123] In the area of ​​the pleat spread 88, a pleat spacing measured in the circumferential direction between radially outer fold edges 92 of the first filter medium body 30 is increased compared to the pleat spacing of adjacent outer fold edges 92 (see Figure 13). Here, the pleat spread 88 is limited to a single outwardly open pleat. Due to the pleat spread 88, a pleat angle 94 is also increased compared to the adjacent pleats (see also Figure 10).

[0124] Additionally, the filter device 10.5 includes a second housing positioning device 108, which aligns the second ring filter element 28 relative to the filter housing 12 in a defined angular position with respect to the longitudinal axis 46 (see Figure 20). The second housing positioning device 108 has a second housing engagement element 110 (see also Figures 21 and 22). The second housing engagement element 110 is designed in the form of a radially outwardly facing projection on a support tube 76 fixed to the housing. The support tube 76 can be locked to the housing upper part 14 in a defined angular position.

[0125] The second housing engagement element 110 engages with a second housing counter-engagement element 112 on the second ring filter element 28. The second housing counter-engagement element 112 comprises a pleat spread 114 on the inner circumferential surface 44 of the second filter medium body 32 (see in particular Figure 21) and a recess 116 radially inward on its open end plate 52, see also Figure 24. Here, the pleat spread 88 does not extend over the entire axial length of the first filter medium body 30, but is limited to less than a quarter of its entire length, see Figure 22. The counter-engagement element 64 can be offset in the circumferential direction relative to the second housing counter-engagement element 112, for example by 90°, see Figures 20 and 24.

[0126] In the area of ​​the pleat spread 114, a pleat spacing, measured in the circumferential direction, between radially inner fold edges 118 of the second filter medium body 32 is increased compared to the pleat spacing of adjacent, inner fold edges 118, see Figure 21. Here, the pleat spread 114 is limited to a single inwardly open fold. Due to the pleat spread 114, a pleat angle 120 is also increased compared to the adjacent folds.

[0127] As an alternative to the embodiment of Figure 23a, Figure 23b shows an embodiment in which the second ring filter element 28 has a central tube 77 fixed to the element, which is arranged on the inner circumferential surface 44 of the filter medium body 32 of the second ring filter element 28 and is directly or indirectly fastened to the filter medium body 32 of the second ring filter element 28. The central tube 77 fixed to the element of the second ring filter element 28 has a recess 72 on its end face for engagement with a further axial projection 74' fixed to the housing. The recess 72 of the central tube 77 is part of a housing counter-engagement element 112 of the second ring filter element 28 and extends in particular radially outward into a pleat spread 114 on the inner circumferential surface 44 of the filter medium body 32 of the second ring filter element 28.The closed end plate 54 of the second ring filter element 28 can comprise an opening through which the further housing-fixed axial projection 74' extends in order to engage the end-face recess 72 of the element-fixed central tube 77 of the second ring filter element 28. Furthermore, a closed end plate 50 of the first ring filter element 26 can also comprise an opening that is aligned with the opening of the closed end plate 54 of the second filter element 28.

[0128] Figure 25 shows a second ring filter element 28 for a filter device that essentially corresponds to the filter device 10.5 of Figure 20. The ring filter element 28 also has, on its inner circumferential surface 44, a second housing counter-engagement element 112 with a pleat spread 114 and a recess 116 in the open end plate 52. In the ring filter element 28 of Figure 25, a counter-engagement element 64 for a positioning device 60, which acts between the two ring filter elements 26, 28, is also formed with a recess 65' on the open end plate 52 and an adjacent pleat spread 66; see Figure 12 or Figure 18 and the respective associated description.

[0129] The end plate 52 has an axially protruding sealing bead 122 for engagement with the housing upper part 14. In the ring filter element 28 of Figure 25, the sealing bead 122 deviates in the region of the recesses 65' and 116 into a radially inward indentation 124 and a radially outward indentation 126. In this respect, the otherwise circular sealing bead 122 deviates from a circular shape in these regions.

[0130] Figures 26 and 27 show a sixth filter device 10.6, which corresponds in many aspects to the filter device 10.3 of Figure 13. The differences are primarily explained below; otherwise, reference is made to the above description.

[0131] The filter device 10.6 also features a positioning device 60 acting between the ring filter elements 26, 28. An engagement element 62, which is formed on a central tube 96 fixed to the housing, engages corresponding mating engagement elements 64, 98 radially inward and radially outward on open end plates 48, 52 of the second and first ring filter elements 28, 26, respectively (see Figure 26).

[0132] In addition, the filter device 10.6 has a first housing positioning device 82, see Figure 27. As with the filter devices 10.3 and 10.5, a first housing engagement element 84 formed on the housing lower part 16 engages radially inwardly with a corresponding, radially outwardly open housing counter-engagement element 86 in the region of the closed end plate 50 of the first ring filter element 26; in this respect, reference is made to the above description and Figures 13, 14, 15 and 20, 23.

[0133] Furthermore, the filter device 10.6 has a second housing positioning device 108 (see also Figure 27). As with the filter device 10.5, a second housing engagement element 110 formed on the upper housing part 14 engages radially outwardly with a corresponding, radially inwardly open housing counter-engagement element 112 in the region of the open end plate 52 of the second ring filter element 28; in this respect, reference is made to the above description and Figures 20, 21, and 22. The second ring filter element 28 of the filter device 10.6 corresponds to the ring filter element 28 shown in Figure 25 and described above. Figures 28 and 29 show a seventh filter device 10.7, which corresponds in many aspects to the filter device 10.5 of Figure 20. The differences are primarily explained below; otherwise, reference is made to the above description.

[0134] A positioning device 60 between the two ring filter elements 26, 28 is formed with an engagement element 62 in the form of a radially inwardly facing projection on a central tube 56 firmly connected to the outer ring filter element 26 (see Figure 28). The engagement element 62 engages with a counter-engagement element 64 on the inner ring filter element 28, which here too is formed with a pleat spread 66 on the outer circumferential surface 42 of the second filter medium body 32 (see also Figure 5 in this respect). A radially outwardly facing projection is also formed on the engagement element 62, which engages with a pleat spread 102 on the inner circumferential surface 40 of the first filter medium body 30. The engagement element 62 is provided with two end-face recesses 72, one in each of the projections projecting inwardly and outwardly from the central tube 56. An axial projection 74 of the filter housing 12 engages in each of the recesses 72.Here, the axial projections 74 are integral with the housing base 16.

[0135] In addition, the filter device 10.7 has a first housing positioning device 82, see Figure 29. As with the filter devices 10.3 and 10.5, a first housing engagement element 84 formed on the housing lower part 16 engages radially inwardly with a corresponding, radially outwardly open housing counter-engagement element 86 in the region of the closed end plate 50 of the first ring filter element 26; in this respect, reference is made to the above description and Figures 13, 14, 15 and 20, 23.

[0136] Furthermore, the filter device 10.7 has a second housing positioning device 108 (see also Figure 29). As with the filter device 10.5, a second housing engagement element 110 formed on the housing upper part 14 engages radially outwardly with a corresponding, radially inwardly open housing counter-engagement element 112 in the region of the open end plate 52 of the second ring filter element 28; in this respect, reference is made to the above description and Figures 20, 21, and 22. The second ring filter element 28 of the filter device 10.7 corresponds to the ring filter element 28 shown in Figure 24 and described above.

[0137] Figure 30 shows a fuel cell 186. The fuel cell 186 has an anode 188, a cathode 190, and an electrolyte 192 arranged therebetween. The anode 188 and the cathode 190 can each be adjacent to a gas diffusion layer 193 on the outside. The anode 188 and the cathode 190 can be accommodated between side parts 194, 196 of a bipolar plate 198. Hydrogen can be conducted from a hydrogen inlet 200 to the anode 188 through the side part 194 of the bipolar plate 198. Oxygen or oxygen-containing air can be conducted from an air inlet 202 to the cathode 190 through the side part 196 of the bipolar plate 198. Between the air inlet 202 and the cathode 188, a filter device 10, for example one of the filter devices 10.1 to 10.7 described above, is provided with a ring filter element arrangement 20 arranged in a filter housing 12. The filter device 10 thus functions as a cathode air filter.Water generated in the fuel cell 186 can be drained away through a water outlet 204. Electrical connections of the fuel cell 186 are not shown in detail. In summary, the invention relates to a ring filter element arrangement with two ring filter elements through which flow can occur in series. An outer ring filter element surrounds an inner ring filter element at least in a partial region of its axial extent. A rotational position of the two ring filter elements relative to one another is fixed by an engagement element arranged between the two ring filter elements engaging in the radial direction with at least one of the ring filter elements. The engagement element can be held on a central tube that extends between the filter medium bodies of the ring filter elements. In one embodiment, the central tube is fastened to one of the ring filter elements, and the engagement element engages with the other ring filter element.In another embodiment, the engagement element engages both ring filter elements; the center tube can then be detachable from both ring filter elements and secured to a filter housing. One or both ring filter elements can have bellows. Preferably, the engagement element engages in a spread-out fold.

[0138] List of reference symbols

[0139] Filter device 10.1; 10.2; 10.3; 10.4; 10.5; 10.6; 10.7; 10

[0140] Filter housing 12

[0141] Upper housing part 14

[0142] Housing base 16

[0143] Ring filter element arrangement 20

[0144] Fluid inlet 22

[0145] Fluid outlet 24 first or outer ring filter element 26 second or inner ring filter element 28

[0146] Filter medium body 30 of the first ring filter element 26

[0147] Filter medium body 32 of the second ring filter element 28

[0148] Interior 34 of the first ring filter element 26

[0149] Interior 36 of the second ring filter element 28

[0150] Outer surface 38 of the first filter medium body 30

[0151] Inner surface 40 of the first filter medium body 30

[0152] Outer surface 42 of the second filter medium body 32

[0153] Inner surface 44 of the second filter medium body 32

[0154] Longitudinal axis 46a of the first ring filter element 26

[0155] Longitudinal axis 46b of the second ring filter element 28 common longitudinal axis 46 open end plate 48 of the first ring filter element 26 closed end plate 50 of the first ring filter element 26 open end plate 52 of the second ring filter element 28 closed end plate 54 of the second ring filter element 28

[0156] Middle tube 56 of the first ring filter element 26

[0157] Interface area 58

[0158] Positioning device 60

[0159] Engagement element 62

[0160] Counter-engagement element 64 of the second ring filter element 26

[0161] Recess 65 radially outside in the end plate 54

[0162] Recess 65' radially outside in the end plate 52

[0163] Fold spreading 66 on the outer surface 42 of the second filter medium body 32 radially outer fold edges 68 of the second filter medium body 32

[0164] Fold angle 70

[0165] Recess 72

[0166] Axial projection 74 on filter housing 12

[0167] Support tube 76

[0168] Element-fixed central tube 77 of the second ring filter element 26 protruding radially inner folded edge 78a of the first filter medium body 30 radially inner folded edges 78b of the first filter medium body 30

[0169] Projection 80 of the element-fixed central tube 56 first housing positioning device 82 first housing engagement element 84 first housing counter-engagement element 86

[0170] Pleat spreading 88 on the outer surface 38 of the first filter medium body 30

[0171] Recess 90 radially outside in the end plate 50 radially outer folded edges 92 of the first filter medium body 30

[0172] Fold angle 94 housing-fixed center tube 96

[0173] Counter-engagement element 98 of the first ring filter element 26

[0174] Recess 100 radially inside in the end plate 48

[0175] Fold spreading 102 on the inner surface 40 of the first filter medium body 30 radially inner fold edges 104 of the first filter medium body 30

[0176] Pleat angle 106 second housing positioning device 108 second housing engagement element 110 second housing counter-engagement element 112 on the second ring filter element 28 Pleat spread 114 on the inner surface 44 of the second filter medium body 32

[0177] Recess 116 radially inside in the end plate 52 radially inner folded edges 118 of the second filter medium body 32

[0178] Fold angle 120

[0179] Sealing bead 122

[0180] Indentation 124

[0181] Bulge 126

[0182] Fuel cell 186

[0183] Anode 188

[0184] Cathode 190

[0185] Electrolyte 192

[0186] Gas diffusion layer 193

[0187] Side panels 194, 196

[0188] Bipolar plate 198

[0189] Hydrogen inlet 200

[0190] Air intake 202

[0191] Water outlet 204

Claims

Claims 1. Ring filter element arrangement (20) for arrangement in a filter housing (12), in particular for air filtration, in particular for filtering the intake air of a fuel cell (186), with a first ring filter element (26) and a second ring filter element (28), each having a filter medium body (30, 32) which encloses an interior space (34, 36), wherein the second ring filter element (28) is at least partially received in the interior space (34) of the filter medium body (30) of the first ring filter element (26), wherein an outer circumferential surface (42) of the filter medium body (32) of the second ring filter element (28) and an inner circumferential surface (40) of the filter medium body (30) of the first ring filter element (26) adjoin one another in an interface region (58), characterized in that in the interface region (58) a positioning device (60) for, in particular, unambiguous, relative angular positioning of the two ring filter elements (26, 28) are arranged against each other,and that the positioning device (60) has an engagement element (62), wherein the engagement element (62) extends radially inward and engages with a corresponding counter-engagement element (64) of the second ring filter element (28) and / or extends radially outward and engages with a corresponding counter-engagement element (98) of the first ring filter element (26).

2. Ring filter element arrangement (20) according to claim 1, wherein a common longitudinal axis (46) of the two ring filter elements (26, 28) extends through the interior (34, 36) of their filter medium bodies (30, 32).

3. Ring filter element arrangement (20) according to one of the preceding claims, wherein the first and / or the second ring filter element (28) have a hollow cylindrical shape.

4. Ring filter element arrangement (20) according to one of the preceding claims, wherein at least one of the filter medium bodies (30, 32) of the first and / or second ring filter element (28) comprises an adsorbing gas filter medium.

5. Ring filter element arrangement (20) according to one of the preceding claims, wherein the filter medium body (30) of the first ring filter element (26) has a bellows, wherein at least one fold of the bellows on the inner circumferential surface (40) protrudes radially inward further than circumferentially adjacent folds of the bellows, and wherein the protruding fold at least co-forms the engagement element (62) and engages in the counter-engagement element (64) of the second ring filter element (28).

6. Ring filter element arrangement (20) according to one of claims 1 to 5, wherein the first ring filter element (26) has a central tube (56) fixed to the element, which is arranged on the inner circumferential surface (40) of the filter medium body (30) of the first ring filter element (26) and is attached directly or indirectly to the filter medium body (30) of the first ring filter element (26), wherein the engagement element (62) is arranged on the central tube (56), in particular is integral with the central tube (56), and wherein the engagement element (62) extends radially inward and engages in the counter-engagement element (64) of the second ring filter element (28).

7. Ring filter element arrangement (20) according to one of claims 1 to 5, wherein the ring filter element arrangement (20) has a central tube (96) which is detachably arranged in the interface region (58) and, in a proper assembly state, can be arranged fixedly to the housing on the filter housing (12), wherein the engagement element (62) is arranged on the central tube (96) fixed to the housing, in particular is integral with the central tube (96) fixed to the housing, and extends both radially inwardly into the counter-engagement element (64) of the second ring filter element (28) and radially outwardly into the counter-engagement element (98) of the first ring filter element (26).

8. Ring filter element arrangement (20) according to one of the preceding claims, wherein the engagement element (62) is formed on a central tube (56, 96), which central tube (56, 96) is arranged in the interface region (58) and has a recess (72) on the end face for engagement of an axial projection (74) fixed to the housing, in particular wherein the recess (72) is formed in the region of the engagement element (62).

9. Ring filter element arrangement (20) according to one of the preceding claims, wherein the filter medium body (30) of the first ring filter element (26) has a bellows, and wherein the engagement element (62) on the inner circumferential surface (40) of the filter medium body (30) of the first ring filter element (26) engages in a space between two adjacent folds of the bellows, in particular wherein the counter-engagement element (98) of the first ring filter element (26) is formed with a fold spread (102).

10. Ring filter element arrangement (20) according to one of the preceding claims, wherein the filter medium body (32) of the second ring filter element (28) has a bellows, and wherein the engagement element (62) on the outer circumferential surface (42) of the filter medium body (32) of the second ring filter element (28) engages in a space between two adjacent folds of the bellows, in particular wherein the counter-engagement element (64) of the second ring filter element (28) is formed with a fold spread (66).

11. Ring filter element arrangement (20) according to one of the preceding claims, wherein the first and / or the second ring filter element (28) have at least one end plate (48, 50, 52, 54) which sealingly delimits the respective filter medium body (30, 32) in the axial direction.

12. Ring filter element arrangement (20) according to one of the preceding claims, wherein the counter-engagement element (64; 98) comprises a recess (65; 100) in the end plate (48, 54) of the first and / or second ring filter element (28), in particular wherein the recess (65; 100) in the end plate (48, 54) is aligned with a pleat spread (66; 102).

13. Ring filter element arrangement (20) according to one of the preceding claims, wherein the second ring filter element (28) has a central tube (77) fixed to the element, which is arranged on the inner circumferential surface (44) of the filter medium body (32) of the second ring filter element (28) and is fastened directly or indirectly to the filter medium body (32) of the second ring filter element (28), wherein in particular the central tube (77) fixed to the element of the second ring filter element (28) has a recess (72) on its end face for engagement of a further axial projection (74') fixed to the housing.

14. Filter device (10.1-10.7) comprising a filter housing (12) with at least one fluid inlet (22) and at least one fluid outlet (24) and a ring filter element arrangement (20) according to one of the preceding claims, which is arranged in the filter housing (12) and separates the fluid inlet (22) from the fluid outlet (24).

15. Filter device (10.4; 10.6) according to claim 14, further comprising a central tube (96) fixed to the housing, in particular fixed non-releasably to the filter housing (12), wherein an engagement element (62) is arranged on the central tube (96) fixed to the housing, which extends both radially inwardly into the counter-engagement element (64) of the second of the second ring filter elements (28) and radially outwardly into the counter-engagement element (98) of the first ring filter element (26).

16. Filter device (10.2; 10.3; 10.5; 10.6; 10.7) according to claim 14 or 15, wherein the filter housing (12) has a first housing positioning device (82) for, in particular, unambiguous, relative angular positioning of the first ring filter element (26) with respect to the filter housing (12), wherein the first housing positioning device (82) has a first housing engagement element (84) which extends radially inward and engages in a corresponding housing counter-engagement element (86) of the first ring filter element (26).

17. Filter device (10.2; 10.3; 10.5; 10.6; 10.7) according to claim 16, wherein the filter medium body (30) of the first ring filter element (26) has a bellows, and wherein the first housing engagement element (84) on the outer circumferential surface (38) of the filter medium body (30) of the first ring filter element (26) engages in a space between two adjacent folds of the bellows, in particular wherein the housing counter-engagement element (86) of the first ring filter element (26) comprises a fold spreader (88).

18. Filter device (10.2) according to claim 17, comprising a ring filter element arrangement (20) according to claim 5, wherein the first housing engagement element (84) engages in the fold projecting further radially inward, preferably wherein the first housing engagement element (84) extends radially inward into the counter-engagement element (86) of the second ring filter element (28).

19. Filter device (10.5; 10.6; 10.7) according to one of claims 14 to 18, wherein the filter housing (12) has a second housing positioning device (108) for, in particular, unambiguous, relative angular positioning of the second ring filter element (28) with respect to the filter housing (12), wherein the second housing positioning device (108) has a second housing engagement element (110) which extends radially outward and engages in a corresponding housing counter-engagement element (112) of the second ring filter element (28).

20. Filter device (10.5; 10.6; 10.7) according to claim 19, comprising a support tube (76) fastened, in particular non-detachably fastened, to the filter housing (12) which engages into the interior (36) of the filter medium body (32) of the second ring filter element (28), wherein the second housing engagement element (110) is arranged on the support tube (76).

21. Filter device (10.5; 10.6; 10.7) according to claim 19 or 20, wherein the filter medium body of the second ring filter element (28) has a bellows, and wherein the second housing engagement element (110) on the inner circumferential surface (44) of the filter medium body (32) of the second ring filter element (28) engages in a space between two adjacent folds of the bellows, in particular wherein the housing counter-engagement element (112) of the second ring filter element (28) comprises a fold spreader (114).

22. Filter device (10.1; 10.5; 10.7) according to one of claims 14 to 21, in particular comprising a ring filter element arrangement (20) according to claim 8, wherein the filter housing (12) has an axial projection (74) which engages in an end-face recess of a central tube (56), on which central tube (56) the engagement element (62) is arranged.

23. Use of a filter device (10.1-10.7) according to one of claims 14 to 22 as a cathode air filter of a fuel cell (186).

24. Use of a ring filter element (26) having a filter medium body (30) which encloses an interior space (34) and which has a counter-engagement element (98) on its inner circumferential surface (40), as the first ring filter element (26) of a filter device (10.4; 10.6) according to one of claims 14 to 22, wherein the engagement element (62) of the positioning device (60) extends radially outward into the counter-engagement element (98) of the first ring filter element (26).

25. Use of a ring filter element (28) having a filter medium body (32) which encloses an interior space (36) and which has a counter-engagement element (64) on its outer circumferential surface (42), as a second ring filter element (28) of a filter device (10.1-10.7) according to one of claims 14 to 22, wherein the engagement element (62) of the positioning device (60) extends radially inward into the counter-engagement element (64) of the second ring filter element (28).

26. Ring filter element (26, 28) for a filter device according to one of claims 14 to 22, preferably second ring filter element (28) for a filter device according to claim 21, comprising a filter medium body (30, 32) which encloses an interior space (34, 36), wherein the filter medium body (30, 32) has a bellows which is provided with a pleat spread (102; 1 14) on an inner circumferential surface (40, 44).

27. Ring filter element (26, 28) according to claim 26, wherein the ring filter element (26, 28) has at least one open end plate (48, 52) which sealingly delimits the filter medium body (30, 32) in the axial direction, wherein the end plate (48, 52) has at least one recess (100; 116) on an inner circumference which is aligned with the pleat spread (102; 114).

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