Method and apparatus for manufacturing filter devices

Abstract

The invention relates to a method for producing a filter device (1) for filtering a hydrophilic liquid, having a planar filter element (10) which is permeable to the liquid, wherein the filter element (10) has a limited filter area (11) which is coated with a hydrophobic medium. The following steps are provided: a) providing the planar filter element (10), which in particular has a filter nonwoven (13) between a mesh support layer (14) and a spun-bond nonwoven (15), b) producing a ring-shaped, compressed boundary area (16) for the filter area (11), c) applying the medium to the filter area (11) of the filter element (10), (d) obtaining the filter device (1).

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a filter device for filtering hydrophilic liquids, the filter device having a surface filter element permeable to the liquid, wherein the filter element has a confined filter area coated with a hydrophobic medium.

[0002] Furthermore, the present invention relates to an apparatus for manufacturing such filter devices. Background Technology

[0003] Methods and apparatus of the type mentioned at the outset are known from the prior art. Therefore, publication DE 10 2012222 943A1 discloses a filter element for screening or filtering hydrophilic liquids, said filter element having at least one hydrophobic filter region at least during its predetermined first commissioning. The hydrophobic filter region in an otherwise hydrophilic filter element has the advantage that air can escape from the filter device during the initial filling of the chamber containing the filter element, particularly with an aqueous urea solution for exhaust gas aftertreatment. The hydrophobic filter region ensures that air penetration occurs for at least a sufficient duration, thus eliminating the need for active removal of air bubbles from the filter device. Typically, common filter devices surround a filter space, with a suction or extraction position leading to the filter space to ensure that only the filtered medium or filtered liquid reaches the extraction position. Since the filter space is closed, air can only escape from the filter space through the filter element. With an advantageous construction, targeted areas are provided for air to escape, enabling an advantageous filling process, especially during the initial filling of the chamber.

[0004] In order to form a hydrophobic filter area, the literature mentioned above suggests applying an oil-repellent agent (Epilamisierungsmittel) to the filter area. Summary of the Invention

[0005] The method according to the invention, having the features of claim 1, has the advantages that the hydrophobic filter region is manufactured in a simple and cost-effective manner while simultaneously allowing for very precise arrangement and construction of the filter region. According to the invention, a surface-type filter element is provided. This filter element particularly relates to a filter nonwoven fabric, as it has been used in known box-type devices, especially for exhaust gas aftertreatment agents. Preferably, the filter nonwoven fabric is located between a mesh support layer and a spunbond nonwoven fabric. The support layer is particularly used to shape the filter element, as the filter nonwoven fabric itself is almost shape-unstable. The support layer helps to maintain the overall shape stability of the filter device. The spunbond nonwoven fabric ensures that the filter element adheres to the support layer and thus advantageously expands the previously mentioned filter space or separates it from the rest of the box volume. Furthermore, an annular boundary region for the filter region is created in the filter element, in which the material of the filter element is compressed. This compression in the boundary region separates the filter region from the rest of the filter element. A hydrophobic medium is then applied to the filter region of the filter element, resulting in a filter device. The advantageous boundary region ensures that the medium applied to the filter area does not permeate the boundary region and can reach adjacent sections or areas of the filter element. Thus, the hydrophobic structure of the filter element is advantageously confined to the selected filter area.

[0006] According to a preferred extension of the invention, the filter element is compressed between a support element and a tubular punch, thereby creating an annular boundary region within the filter element where the material of the filter element is compressed by pressing. A hydrophobic medium is then applied to the filter region inside the tubular punch. The compression of the filter element between the tubular punch and the support element, and the resulting annular compression, creates a process where the medium enters the uncompressed filter material within the filter region and, because the compressed section of the filter element does not exit the filter region, enters adjacent regions of the filter element. Thus, the medium is retained within the filter region and can sufficiently act on the filter material to hydrophobically construct the filter element within the filter region. If sufficient medium has been applied or applied, the compression is released, the punch is removed from the support element, and the filter element is removed to obtain a filter device. If the filter element has been held between the support layer and the spunbond nonwoven fabric during compression, the filter device is now complete. If only the filter element is placed between the support element and the punch, then the filter element now treated with a hydrophobic medium can be between and connected to the support layer and the spunbond nonwoven fabric.

[0007] According to a preferred extension of the invention, the boundary region is created, in addition to and instead of being compressed, by material locking connections, particularly by welding, between multiple layers of the filter element, especially the filter nonwoven fabric, and the support layer and spunbond nonwoven fabric. The material locking connection similarly compresses the filter element in the boundary region, preventing the still-liquid hydrophobic medium from escaping from the confined filter area of ​​the filter element into adjacent areas. This also produces the advantages mentioned earlier.

[0008] According to a preferred embodiment of the invention, the compression is maintained for a predetermined duration after the medium is applied to the filter area. This ensures that the medium is sufficiently widely dispersed in the filter material and permanently bonded to it, at least to the point that the medium does not immediately separate from the filter element upon initial filling of the tank or upon initial wetting of the filter element with liquid, but remains on the filter element for at least a considerable period until sufficient air escapes through the filter area of ​​the filter element.

[0009] Preferably, the filter element is annularly compressed between the support element and the tubular punch, as explained above. The annular shape creates a closed boundary for the filter region, which enables accurate arrangement of the filter region within the filter element. Here, the annular shape can be constructed circularly, elliptically, or polygonally.

[0010] Particularly preferably, an oil-repellent dispersant is used as the hydrophobic medium or a hydrophobically modified medium. This results in an advantageous hydrophobic structure in the filter area. In particular, a liquid, such as a volatile solvent, is used as the oil-repellent dispersant, in which the fluorinated polymer (fluoroplastic) is dissolved. After being applied to the filter area, the solvent evaporates and the fluoroplastic remains on the surface of the filter material in the filter area, resulting in reduced surface tension in the filter area, thereby creating a hydrophobic effect in the confined filter area. Furthermore, it is preferable to arrange the medium to be applied by means of a feed tube introduced into a punch, especially under pressure, so that the medium advantageously and rapidly enters the filter material of the filter element.

[0011] The apparatus according to the invention, having the features of claim 7, is particularly suitable for performing the methods mentioned above. Here, the apparatus is characterized by a means for creating an annular, compressed boundary region surrounding the filter region, and a means for applying media to the confined filter region. The annular boundary region created by the means reliably ensures the enclosure and separation of the filter region, which should function hydrophobically. The targeted application of the media to the confined filter region by this apparatus produces the advantages mentioned above. Here, the apparatus is particularly characterized by a support element (on which the filter element can be placed), a tubular punch (which can be arranged opposite the support element), and preferably also an actuator means for pressing the filter element between the punch and the support element. This produces the advantages already mentioned.

[0012] In particular, the support element is constructed flat, allowing the filter element to lie face-down on the support element. Optionally, the support element has a recess in the filter region or in a region located inside the punch, allowing the medium to completely penetrate the filter element, and in particular, to wet the underside of the filter element, which extends over the recess rather than lying face-down on the support element. Furthermore, the device preferably has a pressing device for applying the medium, particularly for pressing the medium into the filter element. The pressing device, for example, relates to a second punch whose outer profile substantially corresponds to the inner profile of a tubular punch, and which has a closed end face to press the applied medium into the filter element. Alternatively, the pressing device relates to a conveying device by which the medium is applied to the filter element at a sufficiently high hydraulic pressure, thereby allowing the medium to also enter the filter element. Attached Figure Description

[0013] Further advantages and preferred features, as well as combinations of features, arise particularly from the foregoing description and from the claims. The invention will now be explained in more detail with reference to the accompanying drawings, which illustrate:

[0014] Figure 1 A box-type device with an advantageous filter unit in a simplified side view.

[0015] Figure 2 A first embodiment of the filter device is shown in a simplified cross-sectional view.

[0016] Figure 3A and 3B A second embodiment of an advantageous filter device and equipment for its manufacture.

[0017] Figure 4 Another embodiment of the filter device. Detailed Implementation

[0018] Figure 1 A simplified side view shows an advantageous filter device 1 arranged in a storage container 2 of a box device 3. An aqueous urea solution 4 is maintained in the storage container 3, wherein the urea solution 4 only fills a portion of the storage container 2, thereby leaving an air-filled space 5 above the liquid urea solution.

[0019] A filter device 1 surrounds a space 7 inside a storage tank 2 and is arranged near the bottom 8 of the storage container 2. Furthermore, the filter device 1 is equipped with an extraction port 9, which opens at one end to the space 7 and connects at the other end to an extraction device, such as a transfer pump or the like. Through the extraction port 9, a liquid volume of the waste gas aftertreatment agent or an aqueous urea solution 4 can be extracted from the space 7. Here, the filter device 1 includes, for example, a housing 6, on which the extraction port 9 and the filter element 10 are arranged, thereby surrounding the space 7. According to the current embodiment, the filter element 10 constitutes the cover area of ​​the housing 6 or the filter device 1. In particular, the filter element 10 is held openly on the housing 6 in a plane.

[0020] The filter element 10 is substantially permeable (i.e., hydrophilic) to the liquid (i.e., the aqueous urea solution 4). Only in the filter region 11 is the filter element 10 constructed hydrophobically. This has the advantage that when the storage tank 2 is filled with liquid 4, air can escape from the filter device 1 through the hydrophobic filter region 11, as in… Figure 1 The liquid exits through the filter area 11 as indicated by the upward floating bubbles 12, while the liquid can pass through the remaining filter elements 10 into the filter device 1 or the space 7 of the filter device 1. This ensures that the filter device 1 is completely filled with liquid 4, and also ensures that liquid 4 can be drawn from the filter device 1 at any time through the extraction port 9.

[0021] Figure 2 A filter element 10 is shown in an enlarged cross-sectional view in the region of filter area 11. The filter element 10 is constructed in multiple layers. For this purpose, the filter element 10 has a filter nonwoven fabric 13 located between a mesh support layer 14 and a spunbond nonwoven fabric 15.

[0022] To separate the filter region 11 from the remaining filter elements 10, different layers 13, 14, 15 are material-locked together at the outer edge of the filter region 11, particularly by welding and / or bonding. This creates a boundary region 16, which extends in a ring shape around the filter region 11 and thus defines the filter region on the outside. Therefore, the boundary region 16 is constructed in a ring shape, elliptical shape, polygonal shape, or selectively as an irregular, at least closed linear region. Now, if a hydrophobic medium is applied to the filter region 11, for example by means of an inlet pipe or supply pipe 17 (as in... Figure 2 As indicated in the diagram, the medium remains within the filter region 11 and does not reach the area of ​​the filter element 10 adjacent to it, particularly in the filter nonwoven fabric 13. This ensures that the hydrophobic structure of the filter element 10 is confined and held within the desired filter region 11. In particular, to create the boundary region 16, layers 13, 14, and 15 are first compressed against each other, resulting in a smaller total height h1 in the boundary region 16 of the filter element 10 compared to the remaining regions. This compresses the boundary region 16 and improves the resulting seal between the filter region 11 of the filter element 10 and adjacent sections.

[0023] Figure 3 illustrates another embodiment of the filter element 10 and its manufacture, in which the material locking connection is omitted.

[0024] For this purpose, an advantageous device 18 is used, which also has an inlet pipe 17. Furthermore, device 18 has a support element 19 on which the filter element 10 can be placed in a face-on manner. A tubular punch 20 is arranged opposite the support element 19, with its end face facing the support element 19, such that the annular end wall 21 of the punch 20 is opposite to the support element 19. Here, the outer diameter of the support element 19 is at least as large as the outer diameter of the punch 20. The punch 20 and / or the support element 19 can move toward and away from each other, as by means of... Figure 3A The double arrow 22 indicates the location. To manufacture the filter element 10, it is placed on the support element 19 between the support element 19 and the punch 20. Then, it is pressed between the punch 20 and the support element 19, for example, by moving the punch 20 toward the support element 19, as shown in the image. Figure 3AAs shown in the diagram. Here, the layers 13, 14, and 15 of the filter element 10 are pressed against each other, more specifically, against each other, particularly along the annular end wall 21 of the tubular punch 20. This creates an annular compression region or boundary region 16 in the filter element 10, through which the filter region 11 located within the tubular punch 20 is sealed relative to the external section of the filter element 10. Now, under compression, a hydrophobic medium, especially a hydrophobic liquid, is filled into the punch 20 by means of the inlet pipe 17 and thus applied to the filter element 10 in the filter region 11. Here, the hydrophobic medium enters the filter element 10 in the filter region 11 to achieve the previously mentioned effect. Compression prevents it from reaching adjacent areas of the filter element 10.

[0025] After a predetermined duration, the punch 20 and the support element 19 move away from each other again, thus releasing the filter element 10, as in Figure 3B As shown in the diagram. Here, the compression is released, thereby releasing the seal of the filter region 11 of the filter element 10 relative to the adjacent region. Here, the duration is selected such that the compression is released only when the hydrophobic medium dries out or the filter element 10 has been sufficiently wetted and coated.

[0026] In particular, by using an oil-repellent agent, especially a volatile solvent, as a hydrophobic medium, the fluorinated polymer (fluoroplastic) is dissolved in the volatile solvent.

[0027] If the punch 20 and the support element 19 are moved apart from each other, the filter element 10 is made and has a filter region 11, which also functions hydrophobically at least during the first filling process and ensures that air exits from the filter device 1, as described above.

[0028] The manufacturing method described last has the following advantages: unlike previous manufacturing methods, the filter element 10 is generally constructed flat and, in particular, does not have a usable position with a reduced height h. More specifically, the filter element 10 returns to its initial height h0 after the manufacturing process of the filter region 11, which is greater than the height h1. This results in a flat filter element 10, which can be advantageously integrated into the housing device 2.

[0029] Optionally, the support element 19 also has a recess 23 in the region of the filter area 11, so that the hydrophobic medium can also wet the back or underside of the filter element 10.

[0030] Figure 4A magnified cross-sectional view shows the filter element 10 in the region of filter region 11 in an alternative embodiment. The filter element 10 is similar to that according to... Figure 2 The implementation method is a multi-layered structure. For this purpose, the filter element 10 has a filter nonwoven fabric 13 located between a mesh support layer 14 and a spunbond nonwoven fabric 15. Similarly, a boundary region 16 is provided. In addition to according to... Figure 2 In addition to the implementation method, additional compression regions 41 are provided, particularly point-like, substantially centrally arranged compression regions surrounded by boundary regions 16. The compression regions 41 are used to bring different layers (i.e., the filter nonwoven fabric, the support layer, and the spunbond nonwoven fabric) together so closely that, given the lateral extension of the filter region 11, the maximum height h12 of the free space between the support layer 14 and the filter nonwoven fabric 13 and / or the maximum height h23 of the free space between the filter nonwoven fabric 13 and the spunbond nonwoven fabric 15 in the filter region 11 is preferably between 0 mm and 0.8 mm, and extremely preferably about 0.6 mm. This is especially true when the filter region 11 has an average diameter of about 1 cm. The point-like configuration of the additional compression regions 41 with a diameter of about 4 mm is particularly suitable for this purpose. This (i.e., the sufficient proximity between the three layers 14, 13, and 15 in the region of filter region 11) ensures that all three layers 14, 13, and 15 are saturated with the oil-repellent and, therefore, can be impregnated when the oil-repellent is applied from one side. The sufficient proximity between the three layers ensures that the oil-repellent diffuses or penetrates sufficiently well through all three layers in the region of filter region 11, and thereby ensures the desired effect (i.e., hydrophobicity through all three layers in filter region 11) occurs, allowing air to reliably pass through the three layers into filter region 11 during initial operation of the filter device.

[0031] Similar to boundary region 16 (as the boundary region is in) Figure 1 As already explained in section 3, the additional compression zone 41 can only exist during the manufacturing process (i.e., until the impregnation / oil diffusion is completed) or can be permanently introduced into the material. The latter can be achieved mechanically (and if necessary, thermally), chemically, or through a welding process.

Claims

1. A method for manufacturing a filter device (1) for filtering hydrophilic liquids, said filter device having a surface filter element (10) permeable to the liquid, wherein, The filter element (10) has a confined filter area (11) coated with a hydrophobic medium, characterized by the following steps: a) Provide the surface-type filter element (10). b) Create an annular, compressed boundary region (16) for the filter region (11). c) Applying the hydrophobic medium to the filter region (11) of the filter element (10), d) The filter device (1) is obtained.

2. The method according to claim 1, characterized in that, The surface filter element has a filter nonwoven fabric (13) located between a mesh support layer (14) and a spunbond nonwoven fabric (15).

3. The method according to claim 1, characterized in that, The boundary region (16) is manufactured by squeezing the filter element (10) between a support element (19) and a tubular punch (20), and the hydrophobic medium is applied to the filter element (10) under the squeezed state.

4. The method according to any one of claims 1 to 3, characterized in that, The boundary region (16) is manufactured by a material-locked connection of multiple layers of the filter element (10).

5. The method according to claim 4, characterized in that, The boundary region (16) is manufactured by welding together multiple layers of the filter element (10).

6. The method according to claim 3, characterized in that, The extrusion is maintained for a predetermined duration after the introduction of the hydrophobic medium.

7. The method according to claim 3, characterized in that, The filter element (10) is annularly compressed between the support element (19) and the tubular punch (20).

8. The method according to any one of claims 1 to 3, characterized in that, Use an oil-repellent agent as a hydrophobic medium.

9. The method according to claim 2, characterized in that, A compression region (41) is created in the filter region (11), which is surrounded by the boundary region (16), so that when the hydrophobic medium is applied, the hydrophobic medium can hydrophobize not only the filter nonwoven fabric (13) but also the support layer (14) and the spunbond nonwoven fabric (15) because the filter nonwoven fabric (13) is sufficiently close to the support layer (14) on the one hand and the spunbond nonwoven fabric (15) on the other hand.

10. The method according to claim 9, characterized in that, The compression area (41) is a point-like, centrally located compression area.

11. The method according to claim 2, characterized in that, The maximum height (h12) of the free space between the support layer (14) and the filter nonwoven fabric (13) in the filter region (11) and / or the maximum height (h23) of the free space between the filter nonwoven fabric (13) and the spunbond nonwoven fabric (15) in the filter region is between 0 mm and 0.8 mm.

12. The method according to claim 11, characterized in that, The maximum height (h23) of the free space is 0.6 mm.

13. An apparatus (18) for manufacturing a filter device (1) for filtering hydrophilic liquids, wherein, The filter device (1) has a surface filter element (10) that is permeable to liquid, wherein the filter element (10) is provided with a hydrophobic medium in a confined filter area (11), characterized in that it is provided with means for generating an annular, compressed boundary area (16) surrounding the filter area (11) and means for applying the hydrophobic medium to the confined filter area (11).

14. The device according to claim 13, characterized in that, The device has a tubular punch (20) and a support element (19), and the filter element (10) can be arranged between the tubular punch and the support element and is squeezed by the punch (20) and the support element (19) to create the boundary region (16).

15. The device according to claim 13 or 14, characterized in that, The device is configured to establish a material-locking, annular connection extending around the filter region (11).

16. The device according to claim 15, characterized in that, The device is configured to establish a material-locked, annular welded connection extending around the filter region (11).

17. The device according to claim 14, characterized in that, The support element (19) is constructed on flat ground or has a recess (23) in the area of ​​the filter region (11).

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