FOLDED FILTER MEDIUM

Abstract

A folded filter medium for a filter element is provided with a cellulose substrate impregnated with a phenolic resin and furthermore provided with an ePTFE layer arranged on the cellulose substrate. A filter element with such a filter medium is provided. A filter assembly with a filter element having such a filter medium is also provided. A method for producing such a filter medium includes the steps of impregnating the cellulose substrate with the phenolic resin; applying the ePTFE layer onto the cellulose substrate impregnated with the phenolic resin; folding the cellulose substrate with the ePTFE layer applied thereon; and curing the phenolic resin.

Claims

1. A folded filter medium for a filter element, the folded filter medium comprising: a cellulose substrate impregnated with a phenolic resin; and an ePTFE layer arranged on the cellulose substrate.

2. The folded filter medium according to claim 1, wherein the ePTFE layer is laminated onto the cellulose substrate.

3. The folded filter medium according to claim 1, further comprising a plurality of folds, wherein each fold of the plurality of folds comprises one or more embossments.

4. The folded filter medium according to claim 3, wherein the plurality of folds include a first fold and a second fold neighboring each other, wherein the one or more embossments of the first fold and the one or more embossments of the second fold are arranged such that a region is defined between the first fold and the second fold, wherein the first fold and the second fold do not contact each other in the region.

5. The folded filter medium according to claim 4, wherein the one or more embossments of the first folds and the one or more embossments of the second fold are positioned opposite each other at least partially.

6. The folded filter medium according to claim 3, wherein the one or more embossments are configured to reinforce the fold.

7. The folded filter medium according to claim 6, wherein the plurality of folds include a first fold and a second fold neighboring each other, wherein the one or more embossments of the first fold and the one or more embossments of the second fold are arranged such that a region is defined between the first fold and the second fold, wherein the first fold and the second fold do not contact each other in the region.

8. The folded filter medium according to claim 3, wherein the one or more embossments are selected from the group consisting of knob embossments, S embossments, pleat lock embossments, and combinations thereof.

9. The folded filter medium according to claim 8, wherein the plurality of folds include at least one fold comprising at least two of the pleat lock embossments, wherein between the at least two pleat lock embossments at least an S embossment or a knob embossment is provided.

10. The folded filter medium according to claim 3, wherein each fold comprises identical embossments.

11. A filter element comprising a folded filter medium, the folded filter medium comprising a cellulose substrate impregnated with a phenolic resin and further comprising an ePTFE layer arranged on the cellulose substrate.

12. A filter assembly comprising: a housing; a filter element received in the housing, wherein the filter element comprises a folded filter medium, the folded filter medium comprising a cellulose substrate impregnated with a phenolic resin and further comprising an ePTFE layer arranged on the cellulose substrate; wherein the folded filter medium of the filter element is configured to be cleaned by a reverse flow principle.

13. A vehicle comprising a filter element according to claim 11.

14. A vehicle comprising a filter assembly according to claim 12.

15. A method for producing a filter medium according to claim 1, the method comprising: impregnating the cellulose substrate with the phenolic resin; applying the ePTFE layer onto the cellulose substrate impregnated with the phenolic resin; folding the cellulose substrate with the ePTFE layer applied thereon; curing the phenolic resin.

16. The method according to claim 15, further comprising embossing embossments in folds of the cellulose substrate after folding the cellulose substrate with the ePTFE layer applied thereon and before curing the phenolic resin.

17. The method according to claim 15, wherein applying the ePTFE layer onto the cellulose substrate impregnated with the phenolic resin is done by laminating.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0036] FIG. 1 shows a perspective view of a filter assembly according to an embodiment.

[0037] FIG. 2 shows a section along the line A-A of FIG. 1.

[0038] FIG. 3 shows a perspective view of a section of a folded filter medium.

[0039] FIG. 4 shows a section along the line B-B of FIG. 3.

[0040] FIG. 5 shows a layer construction of the filter medium.

[0041] FIG. 6 shows a schematic illustration of a manufacturing method for a filter medium.

[0042] In the Figures, same or functionally the same elements are provided with the same reference characters, if nothing else is indicated.

DESCRIPTION OF PREFERRED EMBODIMENTS

[0043] FIG. 1 shows a perspective view of an embodiment of a filter assembly 1. The filter assembly 1 can also be referred to as filter system. It is used as intake air filter in internal combustion engines for agricultural purposes, for example, a combine harvester. The filter assembly 1 comprises a housing 2 in which a filter element 3 is received, as can be seen in FIG. 2.

[0044] The housing 2 comprises furthermore a fluid inlet 4 and a fluid outlet 5. The fluid to be filtered, in this case the intake air L, enters the filter assembly 1 through the fluid inlet 4. The intake air L=purified by the filter element 3 exits from the filter assembly 1 through the fluid outlet 5.

[0045] As illustrated in FIG. 2, the filter element 3 comprises a folded filter medium 6 surrounding a support tube 7 and contacting it in such a way that the support tube 7 provides a supporting function for the filter medium 6 as flow passes through. The support tube 7 is grid-shaped and thus embodied to be fluid-permeable.

[0046] In the embodiment according to FIGS. 1 and 2, the filter element 3, the filter medium 6, and the support tube 7 are embodied of a cylindrical configuration with a circular cross section. However, it is also conceivable that the filter element 3, the filter medium 6, and the support tube 7 comprise a different cross section, for example, an oval cross section, and/or are conically embodied. A planar configuration is possible likewise.

[0047] The air L to be filtered passes from a raw side RO of the filter element 3 through the filter medium 6 and exits as purified air L=at a clean side RL of the filter element 3 surrounded by the support tube 7. The raw side RO is in fluid communication with the fluid inlet 4 and the clean side RL with the fluid outlet 5.

[0048] The filter medium 6 comprises an inflow side 8 and an outflow side 9. The inflow side 8 is the side of the filter medium 6 which is facing the raw side RO of the filter element 3. The outflow side 9 is the side of the filter medium 6 which is facing the clean side RL of the filter element 3.

[0049] The dust particles that are contained in the air L to be filtered are deposited at the inflow side 8 of the filter medium 6 so that the filter medium 6 is loaded. After a certain time, loading of the filter medium 6 is however so high that the pressure loss between its inflow side 8 and outflow side 9 is increased to such an extent that the filter element 3 must be replaced or the filter medium 6 cleaned.

[0050] The filter assembly 1 comprises means 10, 11 which serve for cleaning the filter medium 6 by reverse flow principle. The means 10, 11 are pipes 12, 13 which open at ends 14, 15 into the clean side RL of the filter element 3 and, at ends 16, 17 opposite the ends 14, 15, are connectable to a pressure source not illustrated here in detail. Valves 18, 19 are provided at the ends 14, 15 of the pipes 12, 13 for producing pressure pulses.

[0051] The filter medium 6 is a folded filter medium, as is shown in FIG. 3. It shows a perspective view of a section of the folded filter medium 6 with folds 20, wherein in FIG. 3 only one fold 20 is completely illustrated. Each fold 20 comprises two fold walls 21, wherein respective neighboring fold walls 21 are connected to each other at a common fold tip 22also referred to as upper fold edgeat the inflow side and at a common fold base 23also referred to as lower fold edgeat the outflow side.

[0052] The fold walls 21 in this embodiment comprise S embossments 24 as well as knob embossments 25.

[0053] The S embossments 24 are recesses or bulges which extend from a point shortly below the fold tip 22 down to the fold base 23. A fold wall 21 comprises a plurality of S embossments 24. The S embossments 24 are designed in an S-shape and arranged such that two S embossments 24 arranged at two neighboring fold walls 21 are symmetrically embodied. In this way, a region 26 in which the two fold walls 21 do not contact is defined between the S embossments 24.

[0054] The knob embossments 25 are bulges at the inflow side 8 of the fold wall 21. Each of the fold walls 21 comprises a plurality of knob embossments 25. The knob embossments 25 are also arranged such that two knob embossments 25 arranged at two neighboring fold walls 21 are symmetrically embodied. In this way, a region 27 in which the two fold walls 21 do not contact is defined between the knob embossments 25.

[0055] At the fold tips 22 of the folds 20, furthermore pleat lock embossments 28 are provided. These are indentations which serve to keep apart the fold tips 22 of neighboring folds 20.

[0056] FIG. 4 shows a section along the line B-B of FIG. 3. In FIG. 4, the knob embossments 25, S embossments 24, and pleat lock embossments 28 can be seen. Also, the region 27 defined by the oppositely positioned knob embossments 25 of two neighboring fold walls 21 can be seen well in FIG. 4.

[0057] FIG. 5 shows a layer construction of the filter medium 6. The filter medium 6 comprises a cellulose substrate 29 which is impregnated with a phenolic resin 30 and an ePTFE layer 31 arranged on the cellulose substrate 29.

[0058] The cellulose substrate 29 provides for the mechanical stability of the filter medium 6. The cellulose substrate 29 is arranged at the outflow side 9 of the filter medium 6.

[0059] The ePTFE layer 31 which can also be applied as a membrane onto the cellulose substrate 29 is arranged at the inflow side 8 of the filter medium 6. The ePTFE layer 31 serves as an upper filtration layer for the filter medium 6, wherein dust particles are deposited thereon. The ePTFE layer 31 comprises in addition a reduced adhesive force and therefore a reversible particle deposition so that cleaning of the filter medium by the reverse flow principle is simplified. The ePTFE layer 31 is laminated onto the cellulose substrate 29 in the present embodiment.

[0060] The phenolic resin 30 with which the cellulose substrate 29 is impregnated, serves in addition as a binding agent between the cellulose substrate 29 and the ePTFE layer 31. After curing, the phenolic resin 30 is no longer deformable by heat action. The risk of a fold collapse is reduced in normal operation of the filter assembly 1 as well as in cleaning operation by reverse flow principle.

[0061] FIG. 6 shows schematically a manufacturing method for producing the folded filter medium 6. In a step S1 of the method, a cellulose substrate 29 is impregnated with phenolic resin 30. The phenolic resin 30 is comprised of a mixture of a base component and a curing agent which are provided in weight ratios relative to each other well known to a person of skill in the art.

[0062] After the cellulose substrate 29 has been impregnated with phenolic resin 30, the ePTFE layer 31 is arranged on the cellulose substrate 29 (step S2). The ePTFE layer 31 can be arranged by various methods on the cellulose substrate 29.

[0063] In particular, lamination is conceivable as a method. In lamination, the ePTFE layer 31 is applied onto the cellulose substrate 29 and the cellulose substrate 29 with the ePTFE layer 31 arranged thereon is then compressed by means of rolls. The rolls can be preheated in order to improve the adhesion of the ePTFE layer 31 on the cellulose substrate 29. In this case, one speaks of hot lamination. When the rolls are not preheated, one speaks of cold lamination.

[0064] In step S3 of the method, the cellulose substrate 29 with the ePTFE layer 31 attached thereto is folded.

[0065] In step S4 of the method, the folds 20 can be provided with embossments. These are S embossments or knob embossments 24, 25 which are embossed into a fold wall 21 or pleat lock embossments 28 by means of which fold tips 22 are indented.

[0066] Finally, the phenolic resin 30 is cured (step S5). Preferably, phenolic resin is cured by the action of heat. Due to curing of the phenolic resin 30, on the one hand, the cellulose substrate 29, thus the filter medium 6, becomes stiffer. On the other hand, the ePTFE layer 31 is connected to the cellulose substrate 29.

[0067] For producing a ring-shaped closed filter element, the filter medium can be applied onto a support tube and provided with end disks, wherein the end folds are connected to each other for forming the hollow body.

REFERENCE CHARACTERS

[0068] 1 filter assembly [0069] 2 housing [0070] 3 filter element [0071] 4 fluid inlet [0072] 5 fluid outlet [0073] 6 filter medium [0074] 7 support tube [0075] 8 inflow side [0076] 9 outflow side [0077] 10, 11 means [0078] 12, 13 pipes [0079] 14, 15 end [0080] 16, 17 opposite end [0081] 18, 19 reverse pressure valves [0082] 20 fold [0083] 21 fold wall [0084] 22 fold tip [0085] 23 fold base [0086] 24 S embossments [0087] 25 knob embossments [0088] 26, 27 region [0089] 28 pleat lock embossment [0090] 29 cellulose substrate [0091] 30 phenolic resin [0092] 31 ePTFE layer [0093] L air [0094] L=purified air [0095] RO raw side [0096] RL clean side [0097] S2 to S5 method steps