RING FILTER ELEMENT

Description

[0001] The present invention relates to a ring filter element for filtering a fluid, preferably a liquid, according to the preamble of claim 1.

[0002] A ring filter element of this type is known, for example, from DE 10 2014 213 796 A1. Such a ring filter element has an annular filter body made of a filter material, through which the fluid can flow for filtering. Furthermore, such a ring filter element has an annular frame, through which the fluid can flow, against which the filter body is radially supported and which has a longitudinal center axis. The frame is made with a band that is helically wound around the longitudinal center axis and has radial openings or holes through which the fluid can flow. The band has a longitudinal direction that extends helically around the longitudinal center axis and a transverse direction that extends perpendicular to the longitudinal direction.The holes form several adjacent rows in the strip's transverse direction, with the holes following each other in the strip's longitudinal direction. Within each row, the holes are spaced lengthwise along the strip. Holes in adjacent rows of holes in the strip's transverse direction are spaced crosswise along the strip's transverse direction. In the known ring filter element, the strip is made of a resin-impregnated fiber material. Furthermore, in the known ring filter element, the longitudinal hole spacing is greater than the transverse hole spacing. Here, the longitudinal hole spacing and the transverse hole spacing refer to the distance between the hole contours, not the distance between the hole centers. In other words, the longitudinal hole spacing and the transverse hole spacing describe the width of the remaining material between two holes in the respective longitudinal and transverse directions.The holes in the well-known ring filter element are circular in shape.

[0003] Other ring filter elements of this type are known from DE 10 2011 115 050 A1 and from EP 2 559 471 A2, in which, however, the holes are designed as elliptical elongated holes whose longitudinal direction of the holes is aligned parallel to the longitudinal direction of the belt.

[0004] From EP 2 151 268 B1, a filter arrangement is known that comprises two ring filter elements axially adjacent to one another. Both ring filter elements also have a frame wound with a perforated tape. In one ring filter element, the holes in the tape form exactly one row of holes, with the longitudinal spacing of the holes being greater than one pitch of the winding and thus also greater than the transverse spacing of the holes. The holes in this ring filter element are circular. In the other ring filter element, the holes are rectangular, with the holes in the tape forming several rows of holes. Here, too, the longitudinal spacing of the holes is greater than the transverse spacing of the holes. Furthermore, the rectangular holes, with their larger dimensions, extend parallel to the transverse direction of the tape.

[0005] US Patent 2003 / 0 230 127 A1 discloses a spiral-shaped filter tube made of sheet metal, the holes of which are punched into a sheet metal strip in such a way that protruding punch burrs are formed on one side of the strip. US Patents 2005 / 103701 A1, 2007 / 261377 A1, 2007 / 261377 A1, and 2006 / 137316 A1 disclose further ring filter elements from the prior art.

[0006] In a ring filter element, where the filter media flows radially from the outside to the inside during operation, the frame serves to support the filter media, preventing collapse even under high differential pressures between the outer, raw side and the inner, clean side. To support relatively large differential pressures, the frame can generally be made of metal or with a metal band. Frames manufactured with a band wound helically around the longitudinal center axis of the frame can also be called wound frames.

[0007] To design such a ring filter element sustainably and efficiently, a trade-off arises between material usage and flow resistance. The stability of the frame against the differential pressures occurring during operation depends not only on the material used for the belt and its wall thickness, but also significantly on the hole size and number of holes. The flow resistance of the frame also depends on the hole size, hole geometry, and the number of holes in the belt or frame. The larger the cross-sectional area of ​​the holes and the greater the number of holes, the lower the flow resistance due to an increasing open area. Conversely, smaller hole cross-sections and a reduced number of holes result in improved frame stability.In order to achieve sufficient stability for the frame with favorable flow resistance, a comparatively large wall thickness must be used for the hinge, which leads to a comparatively high material usage.

[0008] The present invention addresses the problem of providing an improved or at least an alternative embodiment of a ring filter element of the type mentioned above, which is characterized in particular by high efficiency and sustainability. In particular, a low flow resistance is sought, while at the same time a sufficiently stable frame is to be provided with minimal material expenditure.

[0009] This problem is solved according to the invention by the subject matter of the independent claim. Advantageous embodiments are the subject matter of the dependent claims.

[0010] The invention is based on the general concept of arranging the holes in the tape such that they are more concentrated in less stressed areas of the tape and less concentrated in more stressed areas. This is achieved particularly easily by making the longitudinal spacing of the holes smaller than the transverse spacing. Furthermore, for high pressure differentials, it is proposed that the frame be expediently made of metal, so that the tape is preferably a metal tape.

[0011] The invention utilizes the fact that, during operation of the ring filter element, the differential pressure acts radially on the frame and is generally dissipated within the frame in the circumferential direction. However, since the frame is perforated, the holes are not available for transmitting the forces. Investigations have now shown that in wound frames with low flow resistance, characterized by a high number of holes and holes with a comparatively large opening cross-section, particularly large forces or stress peaks develop between holes of adjacent rows of holes. In these areas, the compressive strength of the tape material used is reached first in the event of an overload.The inventive proposal of selecting a larger transverse hole spacing than longitudinal hole spacing ensures that more tape material is available in the more heavily stressed areas of the frame, namely in the transverse direction, while less tape material is provided in the longitudinal direction, which is nevertheless available for the holes. This results in a helical, solid strip of material, i.e., one without holes, which is capable of absorbing the normal forces acting orthogonally to the central axis of the frame. Investigations have shown that this measure significantly reduces the stress peaks in the tape material between the holes of adjacent rows of holes. In particular, this measure makes it possible to achieve greater compressive strength for the frame with the same amount of material and the same cross-sectional area through which flow can occur, which is defined by the size and number of holes.This also makes it possible to reduce material usage and / or flow resistance while maintaining the same pressure stability. A larger cross-sectional area reduces material usage and flow resistance. A thinner belt wall reduces material usage. In summary, the ring filter element according to the invention is characterized by low flow resistance combined with low material usage and sufficient pressure stability, making the ring filter element particularly efficient and sustainable.

[0012] Depending on the filtration direction, the flow or differential pressure pushes the filter body radially inwards or radially outwards. The frame can be designed as an inner or outer frame, depending on the intended filtration direction for the ring filter element. The inner frame is arranged radially inside the filter body, allowing the filter body to be supported radially inwards against it. The outer frame is arranged radially outside the filter body, allowing the filter body to be supported radially outwards against it.

[0013] According to an advantageous embodiment, the holes can be designed as elongated holes, each with a longitudinal orientation. Designing the holes as elongated holes makes it particularly possible to enlarge the holes in the direction of the less stressed areas of the strip material and / or to reduce them in the direction of the more stressed strip material, while keeping the overall cross-sectional area through which the flow can pass constant or even increasing it, while improving the stability of the frame.

[0014] A particularly advantageous design involves inclined the longitudinal direction of the holes relative to both the longitudinal and transverse directions of the strip. This ensures that the elongated holes do not extend along either the strip's longitudinal or transverse direction, thus reducing the longitudinal spacing between the holes. Furthermore, this design leaves material webs running around the longitudinal center axis, which are optimally capable of absorbing forces acting normally on the frame's outer surface. These material webs can, in particular, extend in a closed ring shape within a plane perpendicular to the frame's longitudinal center axis, resulting in exceptionally high compressive strength.

[0015] A particularly advantageous embodiment is one in which the longitudinal direction of the holes is inclined relative to the longitudinal direction of the strip by an angle of inclination of a maximum of 45°, in particular a maximum of 40°, preferably a maximum of 30°. Such an angle of inclination has proven particularly advantageous for extending the holes towards the less stressed areas of the strip material.

[0016] The holes generally have a round cross-section or a rounded contour to avoid stress concentrations at the opening edge. The elongated holes can generally be oval or elliptical.

[0017] In an advantageous embodiment, the holes can be diamond-shaped and have two diagonals of different lengths in the free opening cross-section, with the longer diagonal defining the longitudinal direction of the hole. It is clear that the corners of diamond-shaped holes are rounded to avoid stress concentrations at the edge of the opening. Diamond-shaped holes with diagonals of different lengths also form elongated holes, so that, in particular, the above-mentioned alignment of the longitudinal direction of the hole can also be optionally implemented for diamond-shaped holes.

[0018] A particularly advantageous configuration is one in which the hole diameter in the longitudinal direction is larger than both the longitudinal hole spacing and the transverse hole spacing. Similarly, a configuration is conceivable in which the diameter of circular holes or the smallest diameter of elongated holes, measured perpendicular to the longitudinal direction, is larger than both the longitudinal hole spacing and / or the transverse hole spacing. In particular, for diamond-shaped holes, the larger diagonal and especially the smaller diagonal can also be larger than both the longitudinal hole spacing and / or the transverse hole spacing.

[0019] The metal strip has two longitudinal edges running parallel to the strip's length and spaced apart in the strip's transverse direction. In a coiled frame, these longitudinal edges abut each other along a helically extending contact zone. In a coiled-seam frame, the longitudinal edges are joined along the contact zone by a flange or fold. In a coiled-welded frame, the longitudinal edges are welded together along the contact zone, i.e., connected by a weld. This weld can be formed by several successive, spaced-apart weld points or weld seams along the contact zone. A continuous weld seam along the contact zone is also conceivable.A coiled welding frame is preferred here, as it has been shown that the welded joint modifies the microstructure of the metal strip in the contact zone, resulting in improved stiffness and stability. The metal strip used to manufacture the coiled frame requires a certain degree of flexibility to allow for proper winding. The welded joint reduces this elasticity in the contact zone, leading to increased stiffness.

[0020] A particularly advantageous configuration is one in which the metal strip has a stiffening rib running along at least one longitudinal edge in the contact zone, which is integrated into the weld. The stiffening rib reinforces the respective longitudinal edge, and this reinforcement is further stabilized by the weld.

[0021] According to the present invention, the metal strip has at least one stiffening bead extending parallel to the longitudinal direction of the strip, which is arranged in the transverse direction between two longitudinal side edges of the metal strip that are parallel to the longitudinal direction and spaced apart from each other in the transverse direction. The stiffening bead represents a three-dimensional, linear elevation or depression on one side of the metal strip. Advantageously, the metal strip is wound such that the respective stiffening bead projects radially inwards at the frame when the frame is designed as an inner frame, and radially outwards when the frame is designed as an outer frame. In this way, an adverse interaction with the filter body can be avoided. Depending on the width of the strip measured in the transverse direction, one, two, or more such parallel stiffening beads can be incorporated into the metal strip.

[0022] The respective stiffening bead in the metal strip can be advantageously positioned so that it runs outside the rows of holes, i.e., with respect to the strip transverse direction between two adjacent rows of holes or between a row of holes and the adjacent longitudinal side edge.

[0023] According to another embodiment, the metal strip can have several stiffening bulges extending in both the longitudinal and transverse directions. These stiffening bulges also contribute to stiffening the frame. The stiffening bulges can be larger than the holes in both the longitudinal and transverse directions, such that each stiffening bulge is at least twice the size of a hole in the longitudinal direction and at least as large as a hole in the transverse direction. It can be provided that at least one row of holes passes through such a stiffening bulge. Alternatively, the bulges can be designed to lie between adjacent holes, particularly between four adjacent holes. In this configuration, the bulges can plastically deform the material between the adjacent holes to the greatest extent possible, without, however, reaching the edge contour of the holes themselves.The edges of the holes thus remain undeformed, forming a ring around each hole within the imaginary surface of the frame. Each stiffening bulge forms a depression or a protrusion on the metal strip. Advantageously, the stiffening bulges can be positioned on the metal strip so that they project from the same side. It is particularly advantageous if the metal strip is wound so that the stiffening bulges project radially inwards on the frame when the frame is designed as an inner frame, and radially outwards when the frame is designed as an outer frame. This prevents any adverse interaction with the filter body.

[0024] Provided the metal strip has at least one of the aforementioned stiffening beads, it may be advantageous to arrange the stiffening bulges in the transverse direction of the strip between such a stiffening bead and the adjacent longitudinal edge, or between two stiffening beads adjacent in the transverse direction. Accordingly, the stiffening beads do not extend through the stiffening bulges, but rather outside of them.

[0025] According to another advantageous embodiment, the holes can be punched in such a way that a punch burr is formed surrounding each hole, projecting from the metal strip on one side. Advantageously, the holes are punched so that the punch burrs of the punched holes project from the same side of the metal strip. Advantageously, the metal strip can then be wound so that the punch burrs of the punched holes project radially inwards on the frame if the frame is designed as an inner frame, and radially outwards if the frame is designed as an outer frame. This reduces, on the one hand, any adverse interaction with the filter body. On the other hand, it can promote the flow through the holes, which reduces the flow resistance.

[0026] In another advantageous embodiment, the holes in at least two adjacent rows of holes can be offset from one another in the longitudinal direction of the strip. This offset, as well as the frame diameter and the strip width of the metal strip measured in the transverse direction, can also be coordinated such that holes that follow one another in the longitudinal direction of the frame parallel to the longitudinal center axis are offset from one another in the circumferential direction of the frame around the longitudinal center axis. This embodiment is particularly advantageous when the filter material is pleated or folded, so that the filter body is designed as a pleated star. An inner fold of this pleated star extends in the longitudinal direction of the frame and rests against the frame.The aforementioned offset in the circumferential direction of holes that are adjacent in the longitudinal direction of the frame prevents all holes that follow one another in the longitudinal direction of the frame from being covered, even with a wide rebate.

[0027] Furthermore, additional material can be introduced into the helical weld seam to further stiffen the frame. This can be achieved by introducing filler metals into the weld pool, for example, by adding flux-cored wire. This can result in a weld seam with a greater material thickness than the sheet metal of the frame. This raised weld seam can be directed radially inwards, particularly in the case of an interior frame, or radially outwards, particularly in the case of an exterior frame. Alternatively, the weld seam can be raised on both sides. Another component can also be permanently joined to the frame during the welding process.In this process, a support body, projecting inwards or alternatively outwards and running helically along the weld seam, can be welded into the weld gap, i.e., between the side surfaces of the adjoining sheet metal strips. Both measures result in a helically shaped area that exhibits high stiffness against forces acting in the normal direction on the outer surface of the frame.

[0028] Further important features and advantages of the invention will become apparent from the dependent claims, the drawings and the associated description of the figures based on the drawings.

[0029] It is understood that the features mentioned above and those to be explained below can be used not only in the combinations specified, but also in other combinations or individually, without departing from the scope of the invention as defined by the claims. Components of a higher-level unit, such as a device, apparatus, or arrangement, mentioned above and those to be mentioned below, which are designated separately, can form separate parts or components of this unit or be integral areas or sections of this unit, even if this is depicted differently in the drawings.

[0030] Preferred embodiments of the invention are shown in the drawings and are explained in more detail in the following description, wherein identical reference numerals refer to identical or similar or functionally identical components.

[0031] They show, schematically, Figure 1 is a highly simplified side view of a ring filter element with a cut-away filter body and an exemplary embodiment of a frame; Figure 2 is a side view of a longitudinal section of the frame in another embodiment; Figure 3 is an enlarged section of the frame made of Figure 2 Figure 4 shows a side view of a longitudinal section of the frame in another embodiment, Figure 5 shows an enlarged section of the frame made of Figure 4 Figure 6 shows a cross-section of the frame in the area of ​​a hole in a further embodiment.

[0032] Accordingly Figure 1The system comprises a ring filter element 1, which serves to filter a fluid, preferably a liquid, and an annular filter body 2 made of a filter material 3, through which the fluid can flow for filtering. The flow through the ring filter element 1 or the filter body 2 during operation of the ring filter element 1 is Figure 1 The area is indicated by arrows and labeled 4. Accordingly, in the example shown, the flow through 4 of the ring filter element 1 is radial from the outside to the inside. It is clear that in another embodiment, the flow direction or filtration direction can also be reversed, i.e., from radially inside to the outside. The filter material 3 can advantageously be folded so that the filter body 2 forms a star of folds. Alternatively, the filter material 3 can also be wound around a longitudinal central axis 7 of the filter body 2. The filter material 3 can be single-layered or multi-layered.

[0033] The ring filter element 1 also comprises an annular frame 5. In the illustrated example, the frame 5 is designed as an inner frame and is arranged inside the filter body 2. With the filtration direction reversed, the frame 5 is advantageously designed as an outer frame and is arranged outside the filter body 2. Preferably, the frame 5 is made of metal. The frame 5 is permeable to fluid flow and has a longitudinal center axis 6. This longitudinal center axis 6 coincides with the longitudinal center axis 7 of the filter body 2 and with a longitudinal center axis 8 of the ring filter element 1. The radial direction is perpendicular to the longitudinal center axis 6. The ring filter element 1 also has two end plates 28 that seal the filter body 2 axially. The frame 5 can be attached to the end plates 28.At least one of the end discs 28 is configured as an open end disc, so that it has an opening that is open to the interior of the ring filter element 1, here the frame 5.

[0034] The frame 5 is made from a strip 9, preferably a metal strip, which is also referred to below as 9. The strip, or metal strip 9, is wound helically around the longitudinal center axis 6 of the frame and has radial holes 10 through which the fluid can flow through the frame 5. In the preferred flow direction 4, radially from the outside to the inside, the frame 5 encloses a clean-side interior, while the filter body 2 is enclosed by a raw-side exterior. The filter body 2 is supported radially on the inside of the frame 5, so that the ring filter element 1 tolerates comparatively high differential pressures between the outer raw side and the inner clean side.

[0035] The metal band 9 has a longitudinal direction 11 that extends helically around the longitudinal center axis 6 of the frame. The metal band 9 also has a transverse direction 12 that extends perpendicular to the longitudinal direction 11. The holes 10 form several adjacent rows 13 of holes in the metal band 9 along the transverse direction 12, which are located in the Figures 1 to 5These rows of holes 13 are indicated by a dashed line. They extend parallel to the longitudinal direction 11 of the strip, thus also helically with respect to the longitudinal center axis 6 of the frame. In the rows of holes 13, the holes 10 follow one another in the longitudinal direction 11 of the strip. Within each row of holes 13, adjacent holes 10 in the longitudinal direction 11 of the strip each have a longitudinal distance 14. Holes 10 in rows of holes 13 that are adjacent to each other in the transverse direction 12 of the strip have a transverse distance 15 from each other in the transverse direction 12 of the strip. In the ring filter element 1 presented here, the hole pattern of the metal strip 9 is configured such that the longitudinal distance 14 between the holes is smaller than the transverse distance 15 between the holes.

[0036] Here, the longitudinal hole spacing 14 and the transverse hole spacing 15 refer to the distance between the hole contours, not the distance between the hole centers. Thus, the longitudinal hole spacing 14 and the transverse hole spacing 15 describe the web width of the remaining material between two holes 10 in the longitudinal direction 11 and in the transverse direction 12, respectively.

[0037] The metal strip 9 has two longitudinal side edges 16 running parallel to the strip's longitudinal direction 11 and spaced apart from each other in the strip's transverse direction 12. These edges adjoin each other along a contact zone 17, which also extends helically with respect to the frame's longitudinal center axis 6. Along this contact zone 17, the adjacent longitudinal side edges 16 are fastened together to form the wound frame 5.

[0038] According to the Figures 2 to 5The holes 10 can be designed as elongated holes, each having a longitudinal direction 18. The longitudinal direction 18 is shown in the enlarged views of the Figures 3 and 5 shown. It is defined at each elongated hole 10 by the orientation of the longest or largest diameter. In the case of the Figures 2 and 3 In the embodiment shown, the holes 10 are configured oval or elliptical. In the embodiment shown Figures 4 and 5 In the embodiment shown, the holes 10 are configured in a diamond shape. Each diamond has two diagonals, which are of different lengths in the holes 10 shown here. The orientation of the longer diagonal defines the longitudinal direction 18 of the holes.

[0039] According to the Figures 2 to 5 In the preferred embodiments shown here, the longitudinal direction of the holes 18 is inclined both relative to the longitudinal direction of the strip 11 and relative to the transverse direction of the strip 12. In the example of the Figure 3The angle of inclination 19 between the longitudinal direction of the hole 18 and the longitudinal direction of the band 11 is approximately 25°. In the example of the Figure 5 This angle of inclination 19 is approximately 35°. The angle of inclination 19 can, for example, be in a range of 10° to 40° and preferably in a range of 20° to 35°, including the limits of each range. Furthermore, the angle of inclination 19 can be adjusted as desired to the metal strip width and the diameter of the frame 5 in order to achieve an individually optimized alignment of the holes 10 from a strength perspective. This is relevant because the pitch of the helical or helix-shaped sheet metal winding varies with varying metal strip width and varying diameter of the frame 10, which in turn affects the alignment of the holes 10 with respect to the longitudinal center axis 6 of the frame.

[0040] The orientation of the longitudinal direction of the holes 18 relative to the longitudinal direction of the strip 11 ensures that, with sufficient cross-sectional area for flow, the holes 10 are primarily located in areas of the metal strip 9 that are subject to less stress under compressive load. The free surface of the frame 5 is thus situated in areas of lower stress within the material. In this way, more material is available within the metal strip 9 between the holes 10 in areas where increased stresses occur due to the force flow, thereby reducing or preventing the formation of stress concentrations.

[0041] For increased stability of the frame 5, it can optionally be provided that the longitudinal side edges 16 adjoining each other in the contact zone 17 are welded together. A corresponding welded joint is shown in Figure 1The weld joint 20 is preferably a weld seam extending continuously along the contact zone 17. It is also conceivable to perform the weld joint 20 using several spot welds or weld seams that follow one another along the contact zone 17 and are spaced apart from each other in the longitudinal direction 11 of the strip. In the contact zone 17, the longitudinal side edges 16 can butt against each other and be welded together. It is also conceivable that the longitudinal side edges 16 overlap in the contact zone 17 in the transverse direction 12 of the strip or in a longitudinal direction 21 of the frame running parallel to the longitudinal center axis 6 of the frame.

[0042] Furthermore, additional material can be introduced into the area of ​​the helically shaped weld seam 20 to further stiffen the frame 5. This can be achieved by introducing welding consumables into the weld pool, for example, in the form of flux-cored wire. This can result in a weld seam 20 that has a greater material thickness than the adjacent sheet metal strip of the frame 5. This raised weld seam 20 can project inwards and / or outwards. Alternatively, another component can be firmly joined to the frame during the welding process. In this case, a support body projecting inwards or outwards, helically extending along the weld seam 20, can be welded into the weld gap, i.e., between the side surfaces of the adjacent sheet metal strips.Both measures result in a helically shaped area which exhibits high stiffness in the direction of forces acting on the outer surface of the frame 5 in the normal direction.

[0043] According to the Figures 2 to 5 The metal strip 9 can have a stiffening bead 22 at least on one of its two longitudinal edges 16, which is expediently integrated into the weld joint 20. Additionally or alternatively, the metal strip 9 can have at least one further stiffening bead 22 that runs parallel to the longitudinal direction 11 of the strip and is arranged in the transverse direction 12 of the strip at one or more arbitrary positions between the two longitudinal edges 16. In the examples of Figures 2 and 4Three such stiffening beads 22 are provided, located between the two longitudinal side edges 16 with respect to the transverse direction 12 of the band. Additionally, at least one further stiffening bead 22 is arranged on at least one of the longitudinal side edges 16, i.e., in the contact zone 17. Each stiffening bead 22 extends between two adjacent rows of holes 13 with respect to the transverse direction 12 of the band. Preferably, each stiffening bead 22 projects radially inwards on the inside of the frame 5, which is designed here as an inner frame. In the case of a frame 5 designed as an outer frame, each stiffening bead 22 projects radially outwards.

[0044] The metal band 9 can also have several stiffening bulges 23, which also stiffen the metal band 9. For illustration, in Figure 2, 3Such stiffening bulges 23 are indicated by a dashed line. It is clear that these stiffening bulges 23 also exist in the embodiment of the Figures 3 and 4are usable. Furthermore, the stiffening bulges 23 can also have geometries other than the elliptical and rectangular geometries shown as examples. The stiffening bulges 23 project radially from the metal strip 9, preferably such that they project radially inwards on the frame 5 designed as an inner frame. On a frame 5 designed as an outer frame, the stiffening bulges 23 then project radially outwards. The stiffening bulges 23 extend in the longitudinal direction 11 and in the transverse direction 12 of the strip and are therefore planar, while the aforementioned stiffening beads 22 are linear. The stiffening bulges 23 can be dimensioned such that at least one row of holes 13 passes through such a stiffening bulge 23.If stiffening bulges 23 and stiffening beads 22 are used simultaneously, an embodiment is preferred in which the stiffening bulges 23 are arranged in the band transverse direction 12 between adjacent stiffening beads 22 or between the contact zone 17 and the adjacent stiffening bead 22. In addition to stiffening bulges 23, which, due to their large dimensions, are penetrated by the holes 10 of the frame 5, smaller stiffening bulges 23 are also conceivable, which are arranged between the holes 10, wherein, in particular, the edge region of the holes 10 remains undeformed. A purely exemplary example of such a smaller stiffening bulge 23 is shown in [reference missing]. Figure 3 Indicated by a broken line. This stiffening bulge 23 can be seen extending between four adjacent holes 10.

[0045] The holes 10 can, in principle, be produced in any way. However, punching the holes 10 is preferred, as this is particularly cost-effective. Figure 6 Figure 1 shows a cross-section of the metal strip 9 or the frame 5 in the area of ​​a punched hole 10. When the holes 10 are punched, a punch burr 24 is formed, which surrounds the respective hole 10 and which protrudes or stands out from the metal strip 9 on one side 25. Figure 6For clarity, this punched burr 24 is exaggerated. The wall thickness 26 of the metal strip 9 is also exaggerated here. A preferred configuration or design is one in which the punched burrs of the 24 holes 10 on the same side 25 of the metal strip 9 protrude from the metal strip 9. The metal strip 9 is further wound onto the frame 5 such that the punched burrs 24 on the frame 5 project radially towards the clean side. In the frame 5 shown here, which is designed as an inner frame, the punched burrs 24 project radially inwards. If the frame 5 is designed as an outer frame, the punched burrs 24 advantageously project radially outwards. This promotes flow from the radial outside to the inside. Furthermore, this avoids adverse interactions with the filter material 3 or with the filter body 2. A remaining punch burr 24 also leads to an increase in stiffness and thus to an increase in the load-bearing capacity of the frame 5.

[0046] In the filter body 2, the filter material 3 can be folded or pleated in a zigzag pattern, thus forming a pleated star shape in the filter body 2. To ensure that an inner fold of the filter body 2 covers as little of the flow-through cross-section of the holes 10 as possible when it rests against the frame 5, the following can be done according to the Figures 2 and 3 It is provided that the holes 10 in adjacent rows of holes 13 have an offset 29 to each other in the longitudinal direction 11 of the strip. Such an offset 29 is exemplified in Figure 3 marked. This offset 29 and one in Figure 2 registered frame diameter 28, which is preferably the inner diameter 28 of the frame 5, and a band width 30 of the metal band 9 measured in the band transverse direction 12, which is exemplified in Figure 1 The items listed can now be appropriately coordinated so that, according to Figure 3Holes 10, which follow one another on the frame 5 in the longitudinal direction 21 of the frame, in a direction that Figures 1 to 5 The frame circumference direction 31, indicated by a double arrow and which runs around the frame longitudinal center axis 6, is offset from each other.

[0047] In contrast to the one in Figure 6 In the illustration shown, the wall thickness 26 of the metal strip 9 is expediently less than 66% and preferably less than 33% of the maximum diameter of the respective hole 10. The number and size of the holes 10 are expediently selected such that the sum of the opening cross-sections of the holes 10 in the metal strip 9 occupies at least 15%, preferably at least 25%, of the area of ​​the metal strip 9.

Claims

1. Ring filter element (1) for filtering a fluid, preferably a liquid, - with an annular filter body (2) of a filter material (3) and through which the fluid can flow in order to filter the fluid, - with an annular frame (5) through which the fluid can flow and on which the filter body (2) is radially supported, the frame having a frame longitudinal center axis (6), - wherein the frame (5) is produced with a strip (9) which is wound in a helical manner about the frame longitudinal center axis (6) and which has radial holes (10) through which fluid can flow through the frame (5), - wherein the strip (9) has a longitudinal strip direction (11) which extends helically about the frame longitudinal center axis (6) and a transverse strip direction (12) which extends transversely relative to the longitudinal strip direction (11), - wherein the holes (10) in the strip (9) form multiple hole rows (13) which are adjacent in the transverse strip direction (12) and in which the holes (10) follow each other in the longitudinal strip direction (11), - wherein the holes (10) within the respective hole row (13) have a longitudinal hole spacing (14) from each other in the longitudinal strip direction (11), - wherein the holes (10) of hole rows (13) which are adjacent in the transverse strip direction (12) have a transverse hole spacing (15) from each other in the transverse strip direction (12), - wherein the strip (9) is a metal strip (9), - wherein the longitudinal hole spacing (14) is smaller than the transverse hole spacing (15), and - wherein the metal strip (9) has at least one reinforcement bead (22) which extends parallel with the longitudinal strip direction (11) and which is arranged in the transverse strip direction (12) between two longitudinal side edges (16) of the metal strip (9) which extend parallel with the longitudinal strip direction (11) and which are spaced apart from each other in the transverse strip direction (12).

2. Ring filter element (1) according to claim 1, characterized in that - the holes (10) are configured as elongate holes and in each case have a longitudinal hole direction (18), - the longitudinal hole direction (18) is inclined with respect to the longitudinal strip direction (11) and with respect to the transverse strip direction (12).

3. Ring filter element (1) according to claim 2, characterized in that - the longitudinal hole direction (18) is inclined with respect to the longitudinal strip direction (11) through an inclination angle (19) of a maximum of 45°.

4. Ring filter element (1) according to claim 2 or 3, characterized in that - the holes (10) are configured in a diamond-shaped manner and have two diagonals of different lengths, wherein the longer diagonal defines the longitudinal hole direction (18).

5. Ring filter element (1) according to any one of the preceding claims, characterized in that - the metal strip (9) has two longitudinal side edges (16) which extend parallel with the longitudinal strip direction (11) and are spaced apart from each other in the transverse strip direction (12), the side edges adjoining each other along a helically extending contact zone (17) and being welded to each other.

6. Ring filter element (1) according to claim 5, characterized in that - the metal strip (9) has at least at one longitudinal side edge (16) a reinforcement bead (22) which extends in the contact zone (17) and which is incorporated in the weld connection (20).

7. Ring filter element (1) according to any one of the preceding claims, characterized in that - the metal strip (9) has multiple reinforcement bumps (23) which extend in the longitudinal strip direction (11) and in the transverse strip direction (12).

8. Ring filter element (1) according to claim 7, characterized in that - the reinforcement bumps (23) are arranged in the transverse strip direction (12) between such a reinforcement bead (22) and the adjacent longitudinal side edge (16) or between two reinforcement beads (22) which are adjacent in the transverse strip direction (12).

9. Ring filter element (1) according to claim 7 or 8, characterized in that - the reinforcement bumps (23) are sized and arranged in such a manner that they are located exclusively between adjacent holes (10) or - in that the reinforcement bumps (23) are sized and arranged in such a manner that at least one hole (10) is located therein.

10. Ring filter element (1) according to any one of the preceding claims, characterized in that - the holes (10) are stamped so that a stamping burr (24) which surrounds the respective hole (10) and which protrudes from the metal strip (9) at a side (25) of the metal strip (9) is formed, - in that the stamping burrs (24) of the stamped holes (10) protrude at the same side (25) of the metal strip (9), - in that the metal strip (9) is wound in such a manner that the stamping burrs (24) of the stamped holes (10) protrude radially on the frame (5).

11. Ring filter element (1) according to claim 10, characterized in that - the frame (5) is configured as an inner frame which is arranged within the filter body (2), wherein the stamping burrs (24) protrude radially inwards on the inner frame, or - in that the frame (5) is configured as an outer frame which is arranged outside the filter body (2), wherein the stamping burrs (24) protrude radially outwards on the outer frame.

12. Ring filter element (1) according to any one of the preceding claims, characterized in that - the holes (10) in at least two adjacent hole rows (13) have an offset (29) from each other in the longitudinal strip direction (11), - in that this offset (29), a frame diameter (28) of the frame (5) and a strip width (30) measured in the transverse strip direction (12) of the metal strip (9) are adapted to each other in such a manner that holes (10) which follow each other on the frame (5) in a frame longitudinal direction (21) which extends parallel with the frame longitudinal center axis (6) are offset from each other in a circumferential frame direction (31) which extends about the frame longitudinal center axis (6).

13. Ring filter element (1) at least according to claim 5, characterized in that - the region of the weld connection (20) is configured to be raised radially inwards and / or radially outwards during welding by means of a supplementary material feed, and / or - in that during welding materials which, when the weld bath hardens, bring about a local brittleness and consequently a local increase in rigidity are melted into the weld connection (20).

14. Ring filter element (1) at least according to claim 5, characterized in that - in the contact zone (17) a supplementary element which protrudes radially from the frame (5) is inserted and welded along the contact zone (17) to the two longitudinal side edges (16) so that the supplementary element is incorporated in the weld connection (20).