FILTER MATERIAL FOR A FLUID AND DRAINAGE LAYER FOR SUCH A FILTER MATERIAL INCLUDING A FILTER ELEMENT

Abstract

The invention relates to a filter material for a fluid, in particular in the form of a hydraulic fluid, said filter material comprising a multi-layer filter medium (10) through which a fluid can flow and which has at least one filter layer (20), a drainage layer (32) which forms a three-dimensional structure being designed to enlarge the flow channels formed for the fluid to flow through. Said drainage layer cooperates with an adjacent drainage layer and/or consists of individual line elements (33) that form a mesh or grid structure, those line elements being arcshaped or curved at least to some extent. The invention further relates to a drainage layer (32) as such and to a filter element based thereon.

Description

The invention relates to a filter material for a fluid, in particular in the form of a hydraulic fluid, which has a multi-layer filter medium, through which a fluid can flow, and which has at least one filter layer. The invention furthermore relates to a drainage layer, in particular provided for such a filter material, and to a filter element made with such a filter material.

Filter materials for producing replaceable filter elements in hydraulic systems are known in many different designs (US 2005/0269256 A1, US 2007/0175191 A1, etc.) and comprise, for example, a nonwoven filter, preferably composed of multiple layers, having a support layer on one, but preferably on both sides (upstream and/or downstream side). When fluid flows through the filter material, considerable pressure differences result to some extent between the raw side and the clean side.

To be able to withstand these pressure differences and also dynamic flow forces in the unfiltrate, the filter materials, of which corresponding filter elements are made, have so-called support layers. Such support layers or support structures are subject to an alternating pressure load during operation of the filter element. Known support structures can be formed of metal fabrics, in particular fabrics made of high-grade steel wires, which prove to be particularly stable. In the prior art, such fabrics are executed as standard fabrics (DE 600 34 247 T2), also in the manner of a so-called plain weave, wherein the threads are always woven so as to alternate above and then again below the next thread. Known filter materials having support layers and filter layers formed in this manner do not satisfy the requirements placed on them with regard to fluid permeability, which is as high as possible, with high mechanical stability, even if, in addition to support layers and filter layers, a fluid-guiding drainage layer is provided in the form of a grid or fabric, both on the fluid upstream as well as on the fluid downstream side of the filter material, or if larger mesh sizes or coarser grids are provided, so as to obtain lower flow resistances. The latter cases result in the disadvantage of the lower resilience against alternating pressure loads during operation.

With regard to this problem, the object of the invention is to provide a filter material that ensures a high fluid-permeability despite good structural strength.

According to the invention, this object is achieved by means of a filter material, which in each case has the features of claim 1 and of claim 4 in its entirety, by means of a drainage layer according to the feature design of claim 18 as well as by means of a filter element according to the feature design of claim 20.

According to the content of claim 1, an essential feature of the invention is that, in the layer composite of the filter material, in addition to at least one first drainage layer, which can also be formed from a support layer or a support grid, an additional drainage layer, forming a three-dimensional structure, is provided, in order to enlarge the flow channels formed for the fluid flowing through it. On the one hand, an additional three-dimensional structure effects the creation of additional flow channels, which leads to a decrease in the pressure differential, in particular on the downstream side of the filter material, where very narrow flow channels are created due to a star folding of the filter material. On the other hand, an increased resilience against alternating pressure loads also results on the upstream side of the filter material due to the stabilizing of the pleats by decreasing the pleat spacings, as it results from the presence of the drainage layer. Due to the formed additional flow channels of the additional further drainage layer, the pleat spacings of the pleated filter mat or of the pleated filter medium are decreased, which leads to an additional stabilization of the individual pleats. It has proven to be particularly advantageous if the additional drainage layer is flush with an adjacent drainage layer.

According to the content of claim 4, an essential feature of the invention is that the drainage layer, which is provided for increasing the fluid flow and which forms a three-dimensional structure with the line elements, which are used and which form the mesh or grid for the drainage layer, are arc-shaped or curved, at least to some extent. This creates a particularly high structural stability for this drainage layer and therefore for the entire filter medium in a desired manner, and additional flow channels having a particularly large cross section are furthermore created, which leads to a decrease of the pressure differential, in particular on the downstream side of the filter material, where very narrow flow channels are created due to the common star folding of the filter material. The fact that, due to being curved, a helical guide for the fluid is obtained, also contributes to this, which leads to an energy input having improved flow through the filter medium.

On the other hand, an increased resilience to alternating pressure loads results due to the stabilizing of the pleats by decreasing the pleat spacings on the upstream side of the filter material, as follows from the presence of the drainage layer having the curved, helical arcs for the line elements.

In the case of a preferred embodiment of the solution according to the invention, two line elements, which run adjacent to one another in an arc-shaped manner at least to some extent, are provided to define a flow chamber between two consecutive cross points such that the largest opening width of said flow chamber is formed between two apexes of the curved course, which are spaced apart from one another. Preferably, provision is made thereby for said flow chamber to be shaped as approximately circular, elliptical or in the manner of a rhombus, between two adjacent curved courses. A particularly good compromise with regard to good stability characteristics and high fluid permeability can be realized thereby, wherein the flow chambers form individual flow channels, which, being defined by the line elements, provide for an optimal, helical flow guide within a filter element that is equipped with the filter material according to the invention.

Particularly preferably, provision is furthermore made for at least one support layer to be composed of line-shaped grid or mesh elements, which border individual outlets at the edges thereof. In this respect, a particularly good support for the entire filter material or filter medium is then attained by means of the arc-shaped courses of the line-shaped elements of the drainage layer. In this regard, the respective support layer assumes the function of a common first drainage layer, which interacts with the additional drainage layer, preferably in the case of a flat arrangement.

Further advantageous embodiments of the filter material according to the invention are the subject matter of the other dependent claims.

According to the content of claim 18, a drainage layer, in particular provided for the above-described filter material, is also the subject matter of the invention, wherein the individual line elements of the drainage layer are arc-shaped or curved at least to some extent, which, particularly preferably, are arranged within a repeating pattern so as to be curved in an S-shape at least to some extent.

According to the content of claim 20, the filter element, which is provided for use in a filter device for fluid, in particular for hydraulic fluid, and which has a filter material according to one of claims 1 to 17, and particularly preferably a drainage layer according to claims 18 and/or 19 is also subject matter of the invention.

The invention shall be explained in detail below, based on the drawings. Therein:

FIG. 1 shows the upper part of a filter element having a filter material according to the prior art in a partially sectional, schematically simplified drawing;

FIG. 2 shows an enlarged top view of a partial area of a filter material according to the prior art;

FIG. 3 shows a top view, similar to that of FIG. 2, of a filter material according to an exemplary embodiment of the invention;

FIG. 4 shows an enlarged, perspective diagonal view of only a partial area of the filter material, which adjoins pleat tips, according to the exemplary embodiment of FIG. 3 and

FIG. 5 shows a top view of a second exemplary embodiment of the filter material, which is similar to FIG. 3.

The filter element partially illustrated in FIG. 1, as it belongs to the prior art, has a filter mat 10 as the filter material, having a predefinable surface area and predefinable filter characteristics. The filter mat 10 is pleated, as illustrated in FIG. 1, with individual filter pleats 12, which, in a tight package sequence, extend between an inner fluid-permeable support tube 14 and an outer cylindrical housing shell 16, which is likewise fluid-permeable. For the sake of a better depiction, the individual filter pleats 12 are depicted slightly pulled apart, and the individual layer structure of the pleated filter mat 10 is revealed from the partial depiction facing the observer. The filter pleats 12 form a W-shape or V-shape and define fluid gaps between one another, the volume of which increases towards the upstream side, which is directed outward.

In the case of filter elements, which are constructed in such a manner that the filter mat 10 typically comprises a first support layer 18, a second layer 20 as protective nonwoven, a third layer 22 as main nonwoven or filter layer, optionally a further, likewise adjoining, not depicted, layer of a protective nonwoven, or further filter layer and, in any event, a fourth layer of a new support layer 24, which runs on the inner circumference. Said support layers 18, 24 can consist of a wire fabric, a plastic grid or a plastic fabric, among others. One of the layers can additionally be used as drainage layer. The protective nonwoven layers 20 are routinely composed of a plastic nonwoven, and the main nonwoven or filter layers 22 are composed of materials such as glass fiber paper, synthetic filter material (melt-blown fibers), cellulose paper, or the like. Said layers can also be made of so-called composite materials of the same or of different types. As a function of the layer structure and of the respective used filter materials, the filter mat 10 has predefinable filter characteristics, in accordance with the filtration task, wherein, on principle, a high pressure differential stability is desired, as well as a high beta stability across a wide pressure differential range, as well as predefinable filter fineness, wherein sufficient flow channels should be available at the filter element for decreasing the pressure differential, while a good resilience against changing compressive loads should be ensured at the same time.

Seen from the perspective of FIG. 1, the fluid flows through the filter mat 10, in the case of the known filter element, from the outside (upstream side) to the inside (downstream side) and is supported on the inner circumference at its respective pleat deflections against the outer circumference of the support pipe 14 with its annular apertures. However, it is also possible for the fluid, which is to be cleaned, to flow through differently designed filter elements in the reverse direction, so that the above-mentioned upstream side becomes the downstream side and vice versa. The filter mat ends are, in each case, accommodated in an end cap, wherein only the upper end cap 26 is illustrated partially in FIG. 1, which incidentally comprises a spring-loaded bypass valve 28, which, for safety reasons, makes it possible for a fluid to pass through, even if the filter mat 10 should be clogged, thus blocked by contaminants.

FIG. 2 shows a top view of a filter material in the form of a filter mat 10 according to the prior art, having a standard support layer 24, which is formed by means of a metallic grid. Such a grid, optionally having a further inner support layer, which is not visible in FIG. 2, serves as drainage layer, so as to create flow channels for allowing the fluid to flow through.

In contrast, the exemplary embodiment of the filter material according to the invention shown in FIG. 3 differs therefrom in that a drainage layer 32, which is also referred to as an additional drainage layer 32, is provided for an additional drainage function by forming enlarged flow channels. To provide such additional flow channels in the area of the downstream side of the filter mat 10, the drainage layer 32 is provided directly below the outer support layer 24 in the exemplary embodiment of FIG. 3, where the downstream side of the filter mat 10 is visible. To create clearances, this drainage layer 32 is a three-dimensional structure element, and in the present example, a grid-like structure made of plastic, for example of polybutylene terephthalate, polypropylene or polyester, is provided. A metallic fabric or plastic fabric, which, can provide for an electric voltage discharge, can likewise be provided.

In addition to the drainage effect, the drainage layer 32, which is disposed on the inside in the case of the exemplary embodiment of FIGS. 3 and 4, contributes to the pleat stabilization. As can be derived from FIG. 4, the additional volume of the drainage layer 32, which represents a three-dimensional formation, has the result that the filter pleats 12 adjoin the pleat tips of the upstream side more closely with smaller spacings 34 (see FIG. 4). The additional drainage layer 32 thus also forms a further support layer for the filter mat 10.

In the case of the exemplary embodiment of FIG. 5, the drainage layer 32 is disposed as an outer layer on the downstream side of the filter mat 10. In the case of the depicted example, the drainage layer 32 is formed by means of an irregular grid structure made of plastic. When disposed on the downstream side of the filter mat 10, where very narrow flow channels result due to the star folding (pleating), the drainage layer 32 makes a particularly effective contribution to decreasing the flow resistance and thus the pressure differentials, which are created during operation.

As is shown in particular in FIG. 5, at least the line elements 33 of the drainage layer 32 are provided with an arc-shaped or curved course. In particular, the arc-shaped or curved course within a repeating pattern, in the case of which the weave pattern repeats, is embodied in the manner of S-shaped line elements 33. Between two consecutive cross points 35, two line elements 33, which run adjacent to one another in an arc-shaped manner, define a flow chamber 37, the largest opening width of which is between two apexes 39, which are spaced apart from one another, of the arc-shaped courses. The flow chamber 37 formed in this manner, between two adjacent curved courses of the line elements 33, is embodied thereby, approximately, in the manner of an ellipsis or of a rhombus.

Provision is furthermore made that, at the cross points 35, in the case of which the arc-shaped line elements 33 rest against one another, on top of one another, said curved line elements in each case form an angle α, which changes continuously within predefinable angle limits within a repeating pattern, increasing continuously downwards, in particular when seen from the perspective depicted in FIG. 5.

The support layer 18 or 24, which is disposed thereunder, is formed of line-shaped grid or mesh elements 41, which border on individual outlets 43 for the fluid at the edges. The outlets 43 of the respective support layers 18, 24 have a rectangular or rhombic shape thereby; in the shown exemplary embodiment according to FIG. 5 in the manner of a rectangle.

The flow chambers 37 of the drainage layer, in turn, are designed in the manner of channel-like flow guides, which are bordered, at least to some extent, on the edge side by the line elements 33, which run in an arc-shaped manner. Helically formed flow channels, which ensure an improved fluid entry into the other layers of the filter material, including the respective support layer 18, 24 thereof, are created in such a way. Particularly preferably, provision is thereby made for the free flow cross section of the flow chambers 37 of the drainage layer 32 to be dimensioned to be equal to or preferably larger than, particularly preferably twice as large as, the flow openings 43 of the support layer 18 or 24 located thereunder.

The individual line elements 33; 41, which are connected to one another in a mesh-shaped manner, of drainage layer 32 or of the respective support layer 18 or 24, respectively, are embodied as filaments, threads, yarns or fibers made of plastic and/or metal materials and are part of a screen, braided fabric, knitted fabric, fabric or, as illustrated, in the form of a mesh-like grid.

As already specified, the drainage layer 32 can support itself directly at a support grid 18 or 24, which can be assigned thereto, in that the line elements 33; 41 are in direct contact with one another at least to some extent. However, it is likewise possible to dispose the drainage layer 32 between two other layers, preferably between a further drainage layer (not depicted) in the layer composite and one of the support layers 18, 24. In particular, provision can also be made to not only arrange the drainage layer 32 on the downstream side within the filter material, but instead also on the upstream side. Particularly preferably, however, the drainage layer 32 is disposed on the downstream side, upstream of the inner further support layer 24, wherein this kind of drainage layer 32 can additionally or alternatively also be disposed in the outermost area, in the flow direction upstream of the first support layer 18.

As specified above, the mentioned drainage layer 32, together with the filter material described therein, can be combined to form a filter element in accordance with the depiction in FIG. 1. However, it is also possible to use the drainage layer 32 as an independent component with other filter media or filter materials, also in non-pleated form, for a fluid filtration, also in the form the beverage filtration.

Claims

1. A filter material for fluids, in particular hydraulic fluids, which has a multi-layer filter medium (10), through which a fluid can flow, and which has at least one filter layer (20) as well as at least one drainage layer, characterized in that an additional drainage layer (32) is provided, which forms a three-dimensional structure, to enlarge the flow channels formed for the fluid to flow through.

2. The filter material for fluids according to claim 1, characterized in that the additional drainage layer (32) is disposed on the fluid downstream side of the filter material.

3. The filter material for fluids according to claim 1, characterized in that the additional drainage layer (32) is flush with an adjacent drainage layer.

4. A filter material for a fluid, in particular in the form of a hydraulic fluid, having a multi-layer filter medium (10), through which a fluid can flow, and having at least one filter layer (20), wherein a drainage layer (32) is provided, which forms a three-dimensional structure, to enlarge the flow channels formed for the fluid to flow through and which is composed of individual line elements (33) forming a mesh or grid structure, characterized in that the line elements (33) are arc-shaped or curved, at least to some extent.

5. The filter material according to claim 4, characterized in that two line elements (33), which run adjacent to one another, in an arc-shaped manner at least to some extent, define a flow chamber (37) between two consecutive cross points (35), with the largest opening width of said flow chamber being formed between two apexes (39) of the arc-shaped courses, which are spaced apart from one another.

6. The filter material according to claim 4, characterized in that the flow chamber (37) is shaped as approximately circular, elliptical or in the manner of a rhombus between two adjacent arc-shaped line elements (33).

7. The filter material according to claim 4, characterized in that, at the cross points (35), in the case of which the arc-shaped line elements (33) rest against one another, on top of one another, said arc-shaped line elements form an angle (α), which changes continuously within predefinable angle limits within a repeating pattern.

8. The filter material according to claim 4, characterized in that at least one of the support layers (18, 24) is comprised of line-shaped grid or mesh elements (41), which border individual outlets (43) for the fluid at the edges and which in each case form a drainage layer.

9. The filter material according to claim 4, characterized in that the outlets (43) of the respective support layers (18, 24) are rectangular or rhombic in shape.

10. The filter material according to claim 4, characterized in that the flow chambers (37) are designed in the manner of channel-like flow guides, which are bordered, at least to some extent, at the edges by the line elements (33), which run in an arc-shape.

11. The filter material according to claim 4, characterized in that the flow cross section of the flow chambers (37) of the drainage layer (32) is dimensioned to be equal to or preferably larger than, particularly preferably twice as large as, the flow openings (43) of the respective support layer (18, 24).

12. The filter material according to claim 4, characterized in that the individual line elements (33; 41) of the drainage layer (32) and/or support layer (18, 24), designed as filaments, threads, yarns or fibers made of plastic and/or metal materials, which are connected to one another in the manner of a mesh, are part of a screen, braided fabric, knitted fabric, or grid.

13. The filter material according to claim 4, characterized in that the drainage layer (32) is supported directly at a support grid (18, 24), which can be assigned thereto, in that the line elements (33; 41) are in direct contact with one another, at least to some extent.

14. The filter material according to claim 4, characterized in that the drainage layer (32) is arranged between two other layers, preferably between a further drainage layer in the layer composite and one of the support layers (18, 24).

15. The filter material according to claim 4, characterized in that the drainage layer (32) having the line elements (33), which run in an arc-shape, is disposed as an outer layer of the layer composite on the upstream side.

16. The filter material according to claim 4, characterized in that the diameter for the individual line elements (33) of the drainage layer (32) is selected to be greater than the diameter of the line-shaped grid or mesh elements (41) for the respective support layer (18, 24).

17. The filter material according to claim 4, characterized in that the layer structure in the flow direction of the fluid through the filter medium (10), viewed from outside to inside, has the following structure: additional drainage layer (32), at least oneadjacently disposed drainage layer and/orsupport layer (18), at least onefilter layer (20), at least onefurther drainage layer and/or, as an alternative to this, further drainage layer, at least onefurther support layer (24).

18. A drainage layer, in particular provided for a filter material according to claim 4, which is composed of individual line elements (33) forming a mesh or grid structure, characterized in that the individual line elements (33) are arc-shaped or curved, at least to some extent.

19. The drainage layer according to claim 4, characterized in that the line elements (33) of the drainage layer (32) assume an S-shaped course within a repeating pattern of the grid or of the mesh structure.

20. A filter element, which is provided for use in a fluid device for fluids, in particular for hydraulic fluids, and which has a filter material according to claim 1 and/or a drainage layer.