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Title:
PATCHING ELEMENT, FILTER ELEMENT AND METHOD OF REPAIRING FILTER ELEMENT
Document Type and Number:
WIPO Patent Application WO/2017/207867
Kind Code:
A1
Abstract:
The invention relates to a patching element, a filter element and a method of repairing a filter element. The patching element (6) comprises a first element (7) configured to be arranged within a mounting opening (18) formed to a filter element (1). Size and shape of the first element and the mounting opening correspond to each other. The patching element further comprises a second element (8) which is fastened on top of the first element and is larger in size than the first element. The second element comprises a fastening portion for mounting it against surface area of the filter element surrounding the mounting opening.

Inventors:
OKSANEN, Esa (Keilasatama 5, Espoo, 02150, FI)
SAARI, Paula (Keilasatama 5, Espoo, 02150, FI)
Application Number:
FI2017/050347
Publication Date:
December 07, 2017
Filing Date:
May 04, 2017
Export Citation:
Click for automatic bibliography generation   Help
Assignee:
VALMET TECHNOLOGIES OY (Keilasatama 5, Espoo, 02150, FI)
International Classes:
B07B1/46; B01D29/01
Foreign References:
DE1248444B1967-08-24
US4222162A1980-09-16
US3664907A1972-05-23
US1998033A1935-04-16
US1927826A1933-09-26
Other References:
None
Attorney, Agent or Firm:
KOLSTER OY AB (P.O.Box 204, Helsinki, Helsinki, 00181, FI)
Download PDF:
Claims:
CLAIMS

1. A patching element for repairing a solid-liquid filtering element

(1).

characterized in that

the patching element (6) comprises a first element (7) and a second element (8) which are superimposed and fastened to each other to form a double-layer configuration;

the first element (7) has first edges (10) defining the shape and size of the first element (7);

the second element (8) has second edges (11) defining the shape and size of the second element (8);

the second element (8) is greater in size compared to the first element (7) and comprises a fastening portion (9) between the edges (10, 11) of the first and second elements (7, 8) in such a manner that the second element has an edge area which is not covered by the first element and the edge area forms the fastening portion between the edges of the first and second elements;

the second element (8) has a leading edge portion (12) and a trail- ing edge portion (13); and

at least the leading edge portion (12) comprises at least one mechanical fastening element (16).

2. The patching element as claimed in claim 1, character- i z e d in that

the patching element (6) comprises a filtering portion defined by the edge (10) of the first element (7), whereby the filtering portion is surrounded by the fastening portion (9). 3. The patching element as claimed in claim 1 or 2, characterize d in that

the first element (7) has a circular shape and a circular edge (10).

4. The patching element as claimed in any of the preceding claims 1 to 3, characterized in that the second element (8) has a leading edge portion (12) and a trailing edge portion (13); and

the first element (7) is located at a greater distance from the leading edge portion (12) of the second element (8) compared to the trailing edge por- tion (13) of the second element, whereby the first element (7) is located asymmetrically relative to the second element (8).

5. The patching element as claimed in any of the preceding claims 1 to 4, characterized in that

the second element (8) has a hexagonal shape.

6. The patching element as claimed in any of the preceding claims 1 to 5, characterized in that

the fastening portion (9) of the second element (8) is provided with adhesive agent (23).

7. A filter element for solid-liquid filtering, the filter element comprising:

a base structure made of solid-liquid filtering textile and comprising a first side surface (4a) and a second side surface (4b); and

at least one patch fastened to the first side surface (4a) of the base structure;

characterized in that

the filter element (1) is provided with at least one patching element (6), which is in accordance with any of the preceding claims 1 to 6;

the base structure of the filter element (1) is provided with an opening (18) at the patching element (6), wherein shape and size of the opening (18) is in accordance with the shape and size of the first element (7) of the patching element (6); and

the fastening portion (9) of the patching element (6) is fastened against the first surface (4a) of the base structure.

8. The filter element as claimed in claim 7, characterized in that

the filter element (1) is made of woven solid-liquid filtering fabric comprising several longitudinal yarns (2) and several transverse yarns (3); the patching element (6) comprises a woven first element (7) and a woven second element (8) both comprising longitudinal yarns and transverse yarns; and

the longitudinal yarns of the patching element (6) and the filter ele- ment (1 ) are parallel, and correspondingly the transverse direction yarns of the patching element (6) and the filter element (1 ) are parallel.

9. A method of repairing a filter element, the method comprising: examining the filter element (1 ) made of solid-liquid filtering textile; detecting at least one damaged point on a first side surface (4a) of the filter element; and

fastening a patch on the first side surface of the filter element for repairing the detected damaged point;

c h a r a c t e r i z e d by

forming a mounting opening (18) to the filter element (1 ) by removing damaged material around the detected damaged point;

patching the formed mounting opening by means of a patching element (6) comprising a first element (7) and second element (8) being connected to each other to form a double-layer configuration;

and wherein the first element (7) has a pre-determined shape and size, and wherein size of the second element (8) is larger than the first element (7), whereby the second element (8) comprises a leading edge portion (12), a trailing edge portion (13) and a fastening portion (9) between edges (10, 1 1 ) of the first and second elements in such a manner that the second element has an edge area which is not covered by the first element and the edge area forms the fastening portion between the edges of the first and second elements andjhe second element (8) has a leading edge portion (12) and a trailing edge portion (13);

matching the size and shape of the mounting opening (18) with the size and shape of the first element (7);

positioning the first element (7) of the patching element (6) to the mounting opening (18);

fastening the fastening portion (9) of the second element (8) to the first side surface (4a) of the filter element (1 ) at a portion surrounding the mounting opening (18), and fastening at least one mechanical fastening element (16) at least to the leading edge portion (12).

Description:
PATCHING ELEMENT, FILTER ELEMENT AND METHOD OF REPAIRING FILTER

ELEMENT

Background of the invention

The invention relates to a patching element, which is intended for repairing a filter element used in solid-liquid filtering.

The invention relates also to a filter element and a method of repairing a filter element.

The field of the invention is defined more specifically in preambles of the independent claims.

Solid-liquid filtering is used for separating particulate solids and liquid from a sludge. Typical solid-liquid filtering devices used in mining industry are for example tower presses and belt filters. The separation is achieved in the filtering devices by means of filter elements, which are permeable filter fabrics or corresponding filter media, which allow the liquid to penetrate through them and which capture the solid particles. The filter element may be a longitudinal element which is arranged to move in a longitudinal direction during filtering process or between filtering cycles of the filtering device. The filter elements are operated in harsh conditions and are subjected to high loads and wear. The filter elements may be damaged and through holes may be formed. The filter elements may be patched by fastening a patch on the damaged point. However, the known patches and repairing methods have shown to contain some problems.

Brief description of the invention

An object of the invention is to provide a novel and improved patch- ing element, filter element and method of repairing a filter element.

The patching element of the invention is characterized by features of characterized portion of a first independent apparatus claim.

The filter element of the invention is characterized by features of characterized portion of a second independent apparatus claim.

The method of the invention is characterized by features of characterized portion of independent method claim.

An idea of the disclosed solution is that the patching element comprises a first element and a second element, which are superimposed and fastened to each other so that the patching element has a two-part or double- layer configuration. The first and second elements are flat bendable elements. The patching element has a top side intended to face away from the filter element to be patched, and a bottom side facing towards the filter element. The first element is fastened on the bottom side of the second element. Size of the second element is greater than the size of the first element, whereby the sec- ond element comprises on the bottom side an edge area not being covered by the first element. This uncovered edge free area serves as a fastening portion for the patching element. Size and shape of the fastening portion is defined by shapes and sizes of edges of the first and second elements.

For the mounting of the patching element a mounting opening is formed to the filter element by removing damaged material around a detected damaged point of the filter fabric. The size and shape of the mounting opening and the first element correspond to each other, whereby a good form-fitting exist between them. During mounting of the patching element the first element is inserted inside the formed opening and the fastening portion is overlapped over the edges of the mounting opening.

At least the fastening portion of the second element on the bottom side of the patching element is intended to be fastened against the outer surface of the filter element. On a first side of the repaired filter element the second element is visible and on a second side of the filter element the first ele- ment is visible.

An advantage of the disclosed solution is that the patching element has a stabile structure and improved fastening properties due to the double- layer structure. The first element may be arranged inside a hole to be patched, whereby it is supported against edges of the hole. Thereby, the first element within the hole may also participate in receiving forces directed to the patching element during the use of the filter element. The hole and the first element inside the hole form a kind of shape-locking between the patching element and the filter element and are thereby capable in receiving sharing forces.

Further, the first element fills the hole in the filter element and the second element fastens the patching element to an edge surface area of a hole of the filter element. Thus, properties of the second element may be selected in accordance with fastening properties whereby the second element may be relative thin. The first element may be selected so that it properly fills the hole in the filter fabric.

In conclusion, the disclosed patching element provides improved and reliable fastening and ensures cost-effective and efficient repair of the filter elements. When the patching work is quickened, downtime of the filtering device may be shorter.

According to an embodiment, the first element of the patching element serves as a filtering portion. The filtering portion is defined by the edges of the first element. Then, the filtering portion is surrounded by the fastening portion. The first element and the second element may be of liquid permeable material and the fastening means may be selected so that they do not clog the structure at the filtering portion whereby at least the filtering portion may participate in filtering.

According to an embodiment, thickness of the first element corresponds to thickness of the filter element to be patched.

According to an embodiment, the first element is of solid-liquid filtration textile material and is thereby liquid permeable. The first element may be made of a woven solid-liquid filtration fabric comprising several first yarns and several transverse second yarns crossing with the first yarns.

According to an embodiment, the first element is of the same solid- liquid filtering fabric than the filter element to be patched. The second element is of different fabric, which is thinner than the one of the first element since the second element serves only as fastening means. Thanks to the use of a thin second element, the patching element is flat which has positive influence to fastening and durability of the patching element.

According to an embodiment, the second element is of liquid permeable material. The second element may be made of a textile material.

According to an embodiment, the second element is of liquid im- permeable material. Then, the second element may be made of a coated textile or fabric material, or alternatively, it may be made of impermeable sheetlike material. In this embodiment the patching element does not participate in filtering when being installed.

According to an embodiment, the first element and the second ele- ment both comprise several first yarns and several transverse second yarns. The first yarns of the first element and the second element are parallel, and also, the transverse second yarns of the elements are parallel. Thus, the first and second elements are orientated relative to each other so that directions of the yarns systems of the first and second element match. The first and second elements may be of woven material and their weave patterns may correspond to each other. An advantage of the proper orientation is that the elements fit properly against each other and the patching element does not cause runna- bility problems in the filtering device.

According to an embodiment, the first element and the second element are connected to each other by means of stitches. Thus, the elements are permanently fastened to each other. The stiches may form predetermined stitching patterns, which may be designed by taking into account direction of movement of the patching element during use of the filter element, and further, shapes of the elements. This way, proper and wear resistant fastening between the connected elements may be ensured. An advantage of the sewing is that it is a fast and reliable method for connecting textile elements together. Further, the generated stitches have no significant effect on filtering properties at the area of the first element of the patching element, which is beneficial in solutions where the first element is intended to act as a filtering media.

According to an embodiment, the first element and the second ele- ment of the patching element are connected to each other by means of welding techniques, such as using ultrasonic welding. Alternatively, the elements may be fastened to each other by using suitable bonding agent.

According to an embodiment, the first element has a circular shape and a circular first edge. The circular first element and the corresponding cir- cular mounting opening are easy to cut by means of cutting die tool, for example. The circular rotationally symmetrical shapes of the first element and the mounting opening allow final orientation of the patching element before the actual fastening. In other words, orientation of the patching element is not defined already when cutting the mounting hole, whereby execution of the cut- ting is easier.

According to an embodiment, the first element has a predetermined shape and size corresponding to a mounting opening being cut to a filter element. Thus, the first element may alternatively be oval-shaped or rectangular, for example. In this solution, orientation of the mounting opening defines ori- entation of the patching element.

According to an embodiment, the second element has a hexagonal shape. One of the corners of the hexagonal second element serves as a leading edge and is intended to be directed towards a moving direction of the filter element. In other words, the patching element has a wedge shaped leading edge portion. An advantage of this solution is that the leading edge forms a streamlined shape for the patching element in the driving direction and has positive effect on durability and fastening properties of the pathing element.

According to an embodiment, the second element has a shape of an elongated hexagon. The elongated hexagon has a central part with two parallel edge lines having greater length compared to lengths of the other four edge lines forming a leading edge portion and a trailing edge portion of the second element.

According to an embodiment, the first and second elements both have circular shapes. Then, diameter of the circular second element is dimen- sioned to be greater than diameter of the circular first element. The first element being smaller in size may be located asymmetrically relative to the second element.

According to an embodiment, the second element is a diamond- shaped quadrangle. One corner of the second element serves as a leading edge and is intended to be directed towards a moving direction of the filter element. The diamond-shaped element has a first diagonal line and a second diagonal line having different lengths. Length of the first diagonal line is greater than length of the second diagonal line. The first diagonal line passes through a leading edge and a trailing edge of the second element. The first element is located asymmetrically on the first diagonal line. The first element is located at a greater distance from the leading edge than from the trailing edge.

According to an embodiment, the first element and the second element are positioned asymmetrically on a central axis of the patching element. The second element has a leading edge portion and a trailing edge portion intended to be facing towards direction of movement of the filter element. The first element is located at a greater distance from the leading edge portion compared to the trailing edge portion, whereby the first element is located asymmetrically relative to the second element. Since the second element is located asymmetrically, the fastening portion has a greater fastening surface area at the leading edge portion compared to the trailing edge portion. The leading edge portion of the patching element is subjected to greater loads relative to the trailing edge portion, whereby it is beneficial to arrange greater fastening surface area in front of the first element. Thus, the asymmetrical po- sitioning of the elements compensates for the differences in distribution of the loads. According to an embodiment, the patching element comprises at least one marking identifying the leading edge portion or direction of use of the patching element. The marking may be an arrow indicating direction of movement of a filter element during filtering process. Any other visible indica- tion may also be utilized.

According to an embodiment, the patching element comprises at least two different fastening systems or means for fastening the patching element to the filter fabric. The fastening systems are fabric-made, whereby the patching element itself comprises all the needed fastening means without a need to add any separate fastening means when executing the repair at the work site. Thus, the patching element may be a complete set ready for use.

According to an embodiment, the second element of the patching element has a leading edge portion and a trailing edge portion. The leading edge portion comprises one or more mechanical fastening elements. Since greatest forces and wear are subjected to the leading edge portion, use of the mechanical fastening elements at the leading edge is reasonable. Furthermore, the mechanical fastening elements may shield the outer edge of the second element from mechanical forces caused by cleaning devices, such as doctor blades. However, in some cases, the mechanical fastening elements may also be arranged to other edge portions of the second element.

According to an embodiment, the patching element is provided with at least one mechanical fastening element, which comprises at least one first hook and at least one second hook. By means of the hooks a simple and reliable fastening may be achieved. The mechanical fastening element may be pre-fastened to the patching element by means of the at least one first hook and the at least one second hook is available to be mounted to a filter element.

According to an embodiment, the mechanical fastening element is made of metallic material. The metallic fastening element may comprise fas- tening hooks or corresponding elements, which may be bent and locked to the second element and to the filter element. The metallic hooks may be pushed through the filter element and may thereafter be pressed or hammered conveniently to their bent locking position. Further, the metallic mechanical fastening elements are durable and inexpensive. According to an embodiment, the mechanical fastening element comprises an upper surface facing away from the patching element. The upper surface of the mechanical fastening element extends above an upper surface of the second element. Thus, the mechanical fastening element is config- ured to protect the leading edge area of the patching element. A protruding head of the mechanical fastening element may cause a doctor blade of a filtering device to be lifted when facing the mechanical fastening element at the leading edge portion. This way, the doctor blade cannot damage the leading edge of the patching element. Further, the protruding mechanical fastening element may serve as a sacrificial wear element.

According to an embodiment, one or more substantially tapered mechanical fastening elements are utilized for fastening the patching element to the filter element. The mechanical fastening element may have a basic shape resembling a shape of a truncated triangle. Thus, the mechanical fas- tening element is narrower at one edge and wider at the opposite second edge. Further, the mechanical fastening element may have a predetermined orientation relative to the driving direction of the filter element. Then, the wider edge of the mechanical fastening element is fastened to a leading edge of the second element and the narrower edge may be fastened to the filter element. In other words, the mechanical fastening element has a leading edge directing towards the movement direction of the filter element and a trailing edge on the opposite edge. The leading edge has a first width and several first hooks and the trailing edge has a second width and several second hooks. The width of the leading edge is narrower compared to the trailing edge, and further, num- ber of first hooks at the leading edge is lower that the number of second hooks at the trailing edge.

According to an embodiment, the mechanical fastening element is a piece made of plastic material. The mechanical fastening element may be an elongated strip or a form piece covering the leading edge of the second ele- ment. The plastic shielding or covering piece may be provided with fastening hooks or rivets, or alternatively it may be glue bonded. The plastic element ensures fastening of the patching element and may lift mechanical element of a cleaning device during the operation of a filtering device.

According to an embodiment, the fastening portion of the second element is provided with adhesive agent. The adhesive agent may be applied to the second element already during manufacture of the patching element, whereby the patching element is ready for fast and easy mounting at the work site. During the mounting there is no need to apply any additional adhesive, which simplifies the mounting. Further, since the adhesive agent is applied in good factory conditions to the patching element, quality of the glue joint may be ensured. The applying process of the adhesive may also be automated.

According to an embodiment, the fastening portion of the second element is provided with hot melt adhesive i.e. hot glue. The hot glue may be applied to the second element during manufacture of the patching element whereby during mounting there is no need to add any adhesive. This way, the mounting may be quickened and facilitated. Practical tests have shown that the hot glue suits surprisingly well for the fastening of the patching elements. The use of the hot glue allows rapid repair since curing time of the hot glue is shorter relative to conventional adhesive agents.

According to an embodiment, a patching element is provided with hot melt adhesive at least on the fastening portion of the second element. The surface applied with the hot melt adhesive is pressed against the first side surface of the filter element by means of a pushing tool heated above melting temperature of the hot melt adhesive. The pushing tool may be heated by means of electrical heating elements, for example.

According to an embodiment, the outer edge of the first element of the patching element is provided with an adhesive agent. Thus, between the edge of the first element and an edge of the mounting opening is an adhesive joint. In other words, a transition region between the filter element and the first element of the patching element comprises a second fastening portion. Thanks to the adhesive joint of the second fastening portion, the fastening of the patching element may be further improved. This embodiment may be utilized together with differing fastening methods disclosed in this patent application.

According to an embodiment, the patching element comprises a fil- tering portion defined by the outer edge of the first element. The filtering portion is without an adhesive agent. Thus, the filtering portion is not clogged by the adhesive, whereby filtered liquid may penetrate through it. When the patching element is fastened by gluing then the adhesive agent is applied only to the fastening portion of the second element.

According to an embodiment, the patching element is mounted to a filter element intended for solid-liquid filtering. The filter element comprises a base structure made of solid-liquid filtering textile. The filter element further comprises a first surface, which is facing towards sludge to be filtered in a filtering device, and an opposite second surface. The patching element may be fastened on the first surface of the base structure. The base structure of the filter element is provided with a mounting opening at the patching element, wherein shape and size of the opening is in accordance with the shape and size of the first element of the patching element. The first element fills the mounting opening and at least a fastening portion of the patching element is fastened against the first surface of the base structure. Between the fastening portion of the patching element and the first surface of the filter element may be an adhesive joint. Alternatively, or in addition to, edges of the second element may be fastened by means of several mechanical elements such as hooks, staples or studs extending to an opposite second side surface of the filter element. Further, the fastening between the patching element and the filter element may utilize combination of the mechanical fastening and adhesive fastening.

According to an embodiment, the filter element and the elements of the patching element are made of fabric material and all comprise several machine direction yarns and several transverse yarns. The machine direction yarns the filter element and the elements of the patching element are parallel and correspondingly the transverse direction yarns of the filter element and the elements of the patching element are parallel. The disclosed orientation of the yarn systems may avoid possible running problems during use of the filter element.

According to an embodiment, the mounting opening is cut by means of a cutting die. Further, it is possible to utilize in the patching an opening tool set comprising several tools having different sizes, and a patching element set comprising several patching elements having first elements with different sizes. The sizes of the tools for making the mounting openings and the sizes of the first elements for pathing the formed mounting openings match with each other in the mentioned sets. One opening tool is selected from the tool set in response to detected size of the damage point of the filter element. A patching element corresponding to the selected opening tool is selected for the patching. This way, a complete and easily usable arrangement for the patching is disclosed. According to an embodiment, the mounting opening is formed by utilizing high temperature and a heated tool. The tool may be heated by means of electrical heating elements, for example.

According to an embodiment, material of the filter element removed during formation of the mounting opening is utilized as a sample of the filter element. This facilitates monitoring of condition of the filter element.

According to an embodiment, the patching element comprises at least one remotely readable electronic device, such as a RFID tag. Alternatively, operation of the tag may be based on any other wireless data transmis- sion technology. The patching element may comprise at least an ID tag for remote identification. The tags make it possible to monitor service life of the patches and number of patches of the filter element, as well as other interesting features.

Let it be mentioned that the disclosed patching element and patch- ing method is suitable also for filter elements which are not moved in their longitudinal direction. Furthermore, the patching element may alternatively be fastened on a second side surface of the filter element, i.e. on the filtrate side surface.

The above disclosed embodiments may be combined in order to form suitable solutions provided with necessary features.

Brief description of the figures

Some embodiments are described in more detail in the accompanying drawings, in which

Figure 1 is a schematic view of a part of a longitudinal filtering element seen from above, and wherein a first side surface of the filter element is provided with a patching element,

Figure 2 shows the patching element disclosed in Figure 1 schematically and seen from a bottom surface side of the patching element,

Figures 3 and 4 are schematic views of alternative patching elements seen from bottom surface sides of the elements,

Figure 5 is a schematic view of a second side surface of the filter element provided with a patching element,

Figures 6a - 6d are schematic cross sectional views showing steps of repair of a filter element, Figure 7 is a schematic cross sectional view of a patching element comprising a pre-fastened mechanical mounting element at a leading edge of a second element,

Figure 8 shows schematically and in cross section fastening of the patching element of Figure 7 on a side surface of a filter element, and

Figure 9 is a schematic top view of a mechanical fastening element having tapered shape and being provided with several bendable elements at opposite ends of the element.

For the sake of clarity, the figures show some embodiments of the disclosed solution in a simplified manner. In the figures, like reference numerals identify like elements.

Detailed description of some embodiments

Figure 1 shows a filter element 1 for solid-liquid filtration. The filter element 1 may be an elongated object made of solid-liquid filtering material and is moved during operation longitudinally in a moving direction A. The filter element 1 may be used in a belt filter or tower press, for example. The filter element 1 may be of textile material, such as a woven fabric, comprising several longitudinal yarns 2 and transverse yarns 3. The filter element 1 has a first side surface 4a against which slurry to be filtered is directed. The slurry contains solid particles and liquid. Liquid of the slurry passes through a structure of the filter element 1 . An opposite second side surface 4b of the filter element 1 is on a filtrate side. The filter element 1 is subjected during its use to harsh conditions and high loads, whereby holes 5 and other damages may be formed to the structure. Damaged area may be repaired by fastening a patching element 6 at the damaged area. The patching element 6 may be mounted on the first side surface 4a of the filter element 1 . A mounting opening is formed to the filter element 1 for removing the damaged material around the hole 5. The patching element 6 comprises two elements which are arranged one on the other. A first element 7 is mounted to the mounting opening and a second element 8 covers the first element and forms a fastening portion 9 for fastening the patching element 6 against the first side surface 4a of the filter element 1 . The first element 7 has a first outer edge 10 defining size and shape of the first element 7, and correspondingly, the second element has a second outer edge 1 1 defining size and shape of the second element 8. Sur- face area of the second element 8 between the outer edges 10 and 1 1 serves as a fastening portion 9, which may have an adhesive joint with the first side surface 4a of the filter element 1 . As can be noted, the shape of the first element 7 may be circular and the shape of the second element 8 may be hexagonal. However, the elements 7, 8 may also have other suitable shapes. The first element 7 and the second element 8 may be made of textile material, such as woven fabric.

Further, the second element 8 of the patching element 6 may comprise a leading edge portion 12 facing towards the direction of movement A, and a trailing edge portion 13 at the opposite edge area. In Figure 1 the sec- ond element 8 has a hexagonal configuration and one of its corners 14 forms the leading edge portion 12. Thus, frontal part of the second element 8 tapers towards the direction of movement A and provides the patching element 6 with a streamlined and smooth transition section.

Figure 1 further discloses that the first element 7 may be located asymmetrically relative to the leading edge portion 12 and the trailing edge portion 13. However, in some cases the first element 7 may also be located symmetrically.

In Figure 1 the patching element 6 is seen from a top side and in Figure 2 the same patching element 6 is seen from a bottom side. Figure 2 shows that the first element 7 is permanently fastened against a bottom surface of the second element 8 by means of stitches 15. Stitching patterns may be selected in accordance with the shape of the first element 7, and also by taking into account the intended moving direction A of the patching element 6. Figure 2 further discloses in broken lines a mechanical fastening element 16, which may be pre-mounted to the leading edge portion 12. In order to facilitate orientation, the patching element 6 may comprise an arrow or corresponding marking 17 indicating direction of movement of the filter element.

Figure 3 discloses feasible alternative shapes of the elements 7, 8 of the patching element 6. The first element 7 may have a rectangular shape and the second element 8 may have a shape of an elongated hexagon. Also in this solution, one corner of the second element 8 forms the front most part of the leading edge portion 12.

Figure 4 discloses a patching element, wherein the first element 7 and the second element 8 both have circular shapes. The first element 7 is located asymmetrically. Figure 5 shows that on the second surface side of the filter element the first element 7 of the patching element 6 is visible through a mounting opening being cut to the filter element 1 . The second element 8 is located on the first surface side and is therefore shown in Figure 5 by means of broken lines. The second element 8 may have a shape of a diamond and one edge 14 of the quadrangle piece forms a leading edge 12 of the second element 8. Figure 5 further shows that the filter element 1 has a first yarn system YS1 , the first element 7 has a second yarn system YS2 and the second element 8 has a third yarn system YS3. Thereby, they all may be textile structures com- prising several longitudinal and transverse yarns. Orientation of the yarn systems YS2 and YS3 match with each other and they are also oriented in accordance with the first yarn system YS1 . The first element 7 may be made of the same solid-liquid filtering textile as the filter element, whereby it has the same thickness and properties as the filter element 1 . The second element 8 may be made of a textile material having different properties and it may also be thinner.

Figure 6a discloses a filter element 1 wherein a hole 5 has been detected when examining condition of the filter element. Surrounding area of the hole 5 is at first cleaned, where after a mounting opening 18 is formed. The mounting opening may be cut to the filter element 1 by means of a cutting die 19, which is pressed with force F1 against a mating piece 20. Alternatively, any other tool or method may be utilized for making the mounting opening 18. Figure 6b shows that the mounting opening 18 has predetermined edge surfaces 21 after executing the cutting. The removed piece 22 of the filter ele- ment may be utilized as a sample piece for monitoring condition of the filter element. Figure 6c shows that a prefabricated patching element 6 may comprise adhesive agent 23, preferably hot melt adhesive, on the bottom surface of the second element 8. Thereby, fastening portion of the second element 8 may be glued against surfaces surrounding the mounting opening 18 on the first surface 4a. In addition to, outer edges 10 of the first element 7 may comprise the same adhesive agent, whereby a glue joint may also be formed between the edge surfaces 10 and 21 . In Figure 6d the first element 7 of the patching element 6 is arranged inside the mounting opening 18 and the patching element 6 is oriented in accordance with the direction of movement A. Thereafter, the patching element 6 is pressed against the filter element 1 with second force F2. When the adhesive agent is hot melt glue, the fastening sur- faces are heated H simultaneously for melting the pre-applied adhesive. A combined pressing and heating tool may be used for executing the fastening in one go.

Figure 7 discloses a patching element 6 comprising a mechanical fastening element 16 at a leading edge portion 12. The mechanical fastening element 16 may comprise one or more bendable first hooks 24a and second 24b. The first hooks 24a may be pre-fastened to the second element 8 and the second hooks 24b are ready to be pushed through the filter fabric and to be bent after that. In addition to the mechanical fastening elements 16 adhesive agent 23 may be utilized for the fastening. Figure 7 also discloses that the patching element 6 may comprises a remote readable tag 25 for identifying and monitoring purposes.

Figure 8 demonstrates that a mechanical fastening element 16 which is located at a leading edge 12 may protect the patching element 6 from mechanical forces of cleaning devices 26, such as doctor blades. The mechanical fastening element 16 may lift the cleaning device in upward direction so that the front edge of the second element 8 is not influenced by the cleaning device 26.

Figure 9 discloses a mechanical fastening element 16 having a ta- pered shape, which is demonstrated by means of broken lines 27. The element 16 is wider at a trailing end 12 than at a leading end 13. The element 16 is provided with several bendable first portions 28 at a leading edge 12 and several bendable second portions 29 at the opposite end. The bendable portions 28, 29 may comprise tip parts 30 facilitating penetration.

The drawings and the specification associated thereto is merely intended to illustrate the idea of the invention. The details of the invention may vary within the scope of the claims.