Patent Application
20200139289
Priority is claimed to European Patent Application No. EP 18 204 284.6, which was filed on Nov. 5, 2018 and is hereby incorporated by reference herein.
The present invention relates to a filter element with counter-fold, to a cassette filter comprising filter elements, and to a filter cartridge comprising a filter element.
Cassette filters are known from the prior art, for example from WO 2013/185878 A1 (see
Filter cartridges are also known from the prior art, for example from DE 20 2016 005 074 U1. In filter cartridges, at least one filter element is mounted between a base and a cover to yield a casing comprising a filter material which encloses a volume. Cylindrical, conical or cuboid embodiments are possible, for example. An opening is provided in the region of the cover, through which the air to be filtered can escape from the filter. The greater the edge region of the cover given a predetermined external diameter, and thus the smaller the opening, the higher the pressure differential of the filter. However, the width of the edge region is limited by the height of the filter element used. The base of a cartridge may also have an opening, for example when the filter cartridge is divided in its longitudinal direction, or a seal is provided in the holding device. A wide range of filter cartridges are known from the prior art, wherein either a filter element is used, or a plurality of filter elements is also assembled.
In an embodiment, the present invention provides a filter element including a folded filter medium. The filter medium includes two longitudinal edges and transverse edges, and a first fold. The first fold is a zigzag-shaped parallel fold in such a way that folded edges of a first type extend parallel to the transverse edges of the filter medium and folded sections of a first type are formed between fold peaks and fold troughs. The filter medium is provided with at least one second fold as a counter-fold. A folded edge of a second type is present in each folded section of a first type. Each folded edge of a second type is oriented at an obtuse angle to the folded edge of a first type in the fold trough such that triangular folded sections of a second type are formed.
The present invention will be described in even greater detail below based on the exemplary figures. The invention is not limited to the exemplary embodiments. All features described and/or illustrated herein can be used alone or combined in different combinations in embodiments of the invention. The features and advantages of various embodiments of the present invention will become apparent by reading the following detailed description with reference to the attached drawings which illustrate the following:
In order to realize narrower seals (discussed above), it is known to interlock the pleated filter elements. However, there is a problem in this regard since when glass fiber paper is used as the filter medium, there is a risk of the filter medium being destroyed due to its low mechanical strength. In an alternative solution, which provides a miter cut through the filter elements, a secure sealing of the filter elements in the region of their miter can only be achieved with difficultly. A potential leakage point can easily arise here.
Embodiments of the present invention create a filter element, which contributes to reducing the pressure differential of cassette filter and filter cartridges and thus to improving filtration performance. Embodiments further provide the filter element with inherently dimensionally unstable and optionally brittle materials as well, such as, for example, glass fiber paper. Embodiments provide cassette filters and filter cartridges with improved filtration performance.
In an embodiment, one or more (e.g., all) of the above advantages are achieved through a filter element including a folded filter medium. The filter medium includes two longitudinal edges and transverse edges, and a first fold. The first fold is a zigzag-shaped parallel fold in such a way that folded edges of a first type extend parallel to the transverse edges of the filter medium and folded sections of a first type are formed between fold peaks and fold troughs. The filter medium is provided with at least one second fold as a counter-fold. A folded edge of a second type is present in each folded section of a first type. Each folded edge of a second type is oriented at an obtuse angle to the folded edge of a first type in the fold trough such that triangular folded sections of a second type are formed.
An embodiment of a filter element according to the invention has a folded filter medium, the filter medium having two longitudinal edges and two transverse edges, that is, having a length and a width, and in particular being rectangular. The filter medium has a first fold as a zigzag-shaped parallel fold. The filter medium is thus pleated. This first fold is such that folded edges of a first type extend parallel to the transverse edges of the filter medium, and folded sections of a first type are formed between fold peaks and fold troughs. In the folded product, which is produced by folding of a first type, the folded sections of a first type have four corners, two corners in each case at one end A and at the other end B of the folded section of the folded product.
The fold lengths of the first fold, i.e. the distance between fold peak and fold trough, can be uniform so that all fold lengths have the same value. Folded sections of a first type, which are the same size and are in particular rectangular, then result. Advantageously, the filter medium of the filter element can be additionally at least provided with a second fold as a counter-fold. The counter-fold can be such that a folded edge of a second type is present in the folded sections of a first type, each folded edge of a second type being oriented at an obtuse angle α to the folded edge of a first type in the fold trough. This forms folded sections of a second type, which have a triangular shape.
The height of the filter element thus produced—seen in the direction of the original longitudinal edge of the filter medium—is different at the two ends A, B of the filter element. On the side of the filter element A, on which the second fold has been introduced as a counter-fold, the filter element has a lower height. The folded edges of a second type arising from the second fold form, in particular, fold troughs, and the folded edge of a first type between two folded sections of a second type is shaped by the fold of a second type to form a fold peak in each case. In other words, a first corner of the folded section of a first type is folded in by the second fold, that is, the corner is folded over in such a way that it is laid down on the surface of the first folded section, that is to say a first corner of the folded section of a first type is folded inwards by the second folding, that is, the folded edge of a first type is folded in the opposite direction in the region of the fold of a second type.
An advantage of such a filter element is its greater stability compared to a filter element which only has folds of a first type.
The terms “fold trough” and “fold peak” should be considered as follows: The position of the observer with respect to the filter element and the observer's perspective thereof decide whether a folded edge is a fold peak or a fold trough. If, for example, the filter element is turned 180 degrees, a fold trough becomes a fold peak, and vice versa. In the previous and future use of the terms “fold peak” and “fold trough”, the terms serve to provide a clear description of an embodiment of the filter element. The intention is not to introduce a limitation to the effect that the filter element can only be visible or may only be used in a specific installation position. As such, the terms are not intended to limit the filter element to a particular orientation.
In an advantageous embodiment of the filter element according to the invention, the folded edges of a second type extend in the transverse direction of the filter medium only over a small part of the width of the filter medium, in particular over a maximum of one quarter of the width. This is particularly advantageous for the use of the filter elements in cassette filters.
When contrastingly using the filter element in a filter cartridge, however, it can be advantageous if the folded edges of a second type extend over the entire width of the filter medium, i.e., from the cover to the base of the filter cartridge. Creases of the filter element in the inner region of the filter cartridge are thus avoided.
It has been found to be advantageous to provide the filter element with a further fold of a second type, this fold being introduced into the folded section of a first type opposite the fold of a second type and dividing the height of the folded section of a first type opposite the fold of a second type. Each folded edge formed by this fold is at an obtuse angle to the folded edge of a first type in the fold peak such that triangular folded sections of a second type are formed. This fold advantageously ensures that the height of the folded filter element is reduced not only at one end A but also at the other end B. In other words, not only a first corner of the folded section of a first type but also a second corner of the folded section of a first type is folded in or folded inwards, the second corner being at the other end B of the folded section of a first type.
In an embodiment, a further counter-fold can be provided. This counter-fold is such that a further folded edge is present in each folded section of a first type, this folded edge being oriented at an obtuse angle β to the folded edge of a first type in the fold peak, so that further triangular folded sections are formed. The fold is such that the further folded edges form fold peaks, and the folded edge of a first type between two such further triangular folded sections is transformed into a fold trough. This further counter-fold divides the same longitudinal edge of the folded section of a first type, just like the fold of a second type. The filter elements folded in this way thus have a tip at the end A at which the further counter-fold is introduced. In other words, not only a first corner of the folded section of a first type but also the second corner of the folded section of a first type is folded in or folded inwards, which likewise lies at the same end A of the folded section of a first type.
In order to be able to further reduce the height of the filter element in the region of the end already provided with a counter-fold and in order to avoid a projecting of folded sections of a second type beyond the folded edges of a first type, it has been recognized as advantageous to provide the filter element with a further counter-fold, a fold of a third type. This is introduced as a counter-fold into the triangular folded sections of a second type.
It has been found to be advantageous if the filter element is cut such that the cut passes through the triangular folded sections of a second type. Edges arising in the various folds can thus be cut off in the region of the end faces of the filter elements in order to minimize an offset in height.
Embodiments of the invention also relate to a cassette filter comprising a frame and a plurality of filter elements as described above. The filter elements can be accommodated in the frame in such a way that in each case at least two filter elements adjoining one another are arranged at an acute angle ϕ to one another, wherein the folded edges of a first type of one of the adjoining filter elements each form the legs of the acute angle. The filter elements thus have a V-shaped arrangement. In an advantageous embodiment, at least every second filter element is formed within the pair of filter elements of a V-shaped arrangement as described above and has at least one counter-fold. The respective other filter element has at least one first fold, i.e. a parallel fold, as explained above.
The use of the filter elements according to the invention advantageously achieves a reduction of the areas in which no air can flow through the filter, namely the boundary regions in which the filter elements adjoin one another and are sealed. Depending on the dimensions of the filter element and the folds used, this interfering region can be significantly reduced. The reduction results in a lower pressure loss of the cassette filter and thus a better filtration performance.
In a particularly advantageous embodiment of the cassette filter according to the invention, two filter elements forming a V-shaped arrangement each have the smallest distance from one another in the region of their folded edges of a second type and/or in the region of the further folded edges. To prevent the respective filter elements from rubbing against one another and thus possibly causing destruction or at least damage to the filter medium, a minimum distance between the two filter elements can nevertheless still be provided.
It has been found to be advantageous if the folded edges of a second type of two filter elements adjoining one another in each case are at a minimal distance apart, in particular a maximum of three millimeters. This enables a particularly narrow arrangement of the filter elements, the filter elements nevertheless not interfering with one another. In this case, adjoining each other does not necessarily mean touching each other, but rather to be positioned directly next to one another.
In an alternative embodiment, the folded edges of a second type of two filter elements adjoining one another in each case, which form a V-shaped arrangement, are positioned at such a small distance from one another that they touch one another. Such an arrangement is recommended primarily when the filter medium is tolerant to contact. An example of a suitable filter medium for this purpose is made of polypropylene.
In a particularly advantageous embodiment of the cassette filter, two filter elements adjoining each other are glued indirectly or directly to one another. In the case of an indirect adhesive bond, a cross-member can be provided into which an adhesive is introduced. In the case of a direct adhesive bond, no further elements are required, the adhesive is applied directly to the filter elements, and they are directly connected to one another. The adhesive bond extends in particular only on the end faces of the filter elements. The effective filter surface thus remains virtually unchanged, and the filtration performance is hardly impaired. The adhesive bond, in particular with cross-members of the frame, ensures that there are no leakage points between the filter elements and the air to be filtered, not without experiencing any filtration through the filter medium, can flow through the filter through the leakage points. It is considered advantageous to realize the adhesive bond by means of cast PUR.
An embodiment of the invention also relates to a filter cartridge having a base, a cover provided with a central recess, and at least one filter element arranged between the base and the cover. The filter element is designed as described above and thus has a filter medium provided with a fold and a counter-fold. The filter element is shaped in such a way that a casing comprising a filter material is produced which encloses a volume. Cylindrical, conical or cuboid embodiments are possible, for example. For example, the filter element may be rolled into a cylindrical or frustoconical shape, so that a cylindrical or frustoconical filter cartridge is formed. The at least one counter-fold of the filter element is advantageously oriented towards the recess of the cover. That end of the filter element into which the at least one counter-fold is inserted thus adjoins the cover. The use of a counter-folded filter element advantageously enables a larger recess in the cover, that is, a hole with a larger diameter. The pressure loss of the filter cartridge can thus be substantially reduced, and the filtration performance of the filter cartridge increased.
As shown in
Fold peaks 15.1 and fold troughs 15.2 arise by the fold of a first type 11, as shown in
According to an embodiment of the invention, a filter medium 1 provided with such a first fold 11 is further processed by at least one further fold 12. Different variants of a filter element 10 according to the invention having a first fold 11 and at least one further fold 12, 13, 14 are depicted in
In the filter element 10 shown in
The second fold 12 forms folded sections of a second type which have a triangular shape 17.2. In order to clarify the position of a triangular folded section of a second type 17.2, it is shown hatched. The second fold 12 and folded edges of a second type 16.2 extend only over a small part of the width b of the filter medium 1 in the design variant shown in
The second fold 12 results in the filter element 10 having a lower height hA in the region of the second fold 12 at the end A than the height hB at the end B of the filter element 10.
The filter element 10 shown in
This further fold of a second type 12 and its folded edge of a second type 16.2 divides the longitudinal edge of the folded section of a first type 17.1 opposite the fold of a second type described with reference to
The filter element 10 shown in
Further triangular folded sections 17.4 thus ensue by means of the further counter-fold 14. In the region of the filter element 10, in which the filter medium 1 is provided with the second fold 12 and the further counter-fold 14, the filter element 10 is designed pointed in its side view with a tapered height.
In addition to the filter element 10 shown in
In the variant shown in
In an embodiment, to prevent the filter elements 10 from rubbing against one another and damage to the filter medium 1, the filter elements 10 are at a distance a from one another. This distance can be in the range of a few millimeters.
In the arrangement variant depicted via the embodiment of
In the arrangement variant depicted via the embodiment of
In the arrangement variant depicted via the embodiment of
In the arrangement variant depicted via the embodiment of
In the boundary region, where the filter elements 10 adjoin one another and are sealed against one another, strip-shaped cross-members 21 are provided in this example. In order to seal the filter elements 10 with respect to the frame 20 and the cross-members 21 and for there to be no by-passes where air L can pass through the filter 200 without passing through the filter elements 10, the filter elements 10 can be glued together in the region of the cross-member 21.
Such an adhesive bond V which can be created, for example, by a casting with PUR adhesive, is indicated in
In order to simplify the adhesive bond V and reduce the need for adhesive, the height offset in the region of the counter-folds 12, 13, 14 can be minimized in which a cut section S is created by the folded section of a second type 17.2. This is shown in
In
The air L to be filtered can escape from the filter 300 through the recess, that is, the opening 32 in the cover 31. The larger the edge region of the cover 31, and thus the smaller the opening 32, the higher the pressure differential of the filter 300. However, the width D of the edge region is limited by the height of the filter element 10.1 used, that is to say the fold height of the filter element 10.1 used, that is to say the height of the folded section of a first type 17.1.
Filter cartridges 300 are also shown in
While the counter-fold 12 and thus the folded edges of a second type 16.2 according to
While the invention has been illustrated and described in detail in the drawings and foregoing description, such illustration and description are to be considered illustrative or exemplary and not restrictive. It will be understood that changes and modifications may be made by those of ordinary skill within the scope of the following claims. In particular, the present invention covers further embodiments with any combination of features from different embodiments described above and below. Additionally, statements made herein characterizing the invention refer to an embodiment of the invention and not necessarily all embodiments.
The terms used in the claims should be construed to have the broadest reasonable interpretation consistent with the foregoing description. For example, the use of the article “a” or “the” in introducing an element should not be interpreted as being exclusive of a plurality of elements. Likewise, the recitation of “or” should be interpreted as being inclusive, such that the recitation of “A or B” is not exclusive of “A and B,” unless it is clear from the context or the foregoing description that only one of A and B is intended. Further, the recitation of “at least one of A, B and C” should be interpreted as one or more of a group of elements consisting of A, B and C, and should not be interpreted as requiring at least one of each of the listed elements A, B and C, regardless of whether A, B and C are related as categories or otherwise. Moreover, the recitation of “A, B and/or C” or “at least one of A, B or C” should be interpreted as including any singular entity from the listed elements, e.g., A, any subset from the listed elements, e.g., A and B, or the entire list of elements A, B and C.
| Number | Date | Country | Kind |
|---|---|---|---|
| 18 204 284.6 | Nov 2018 | EP | regional |
