Recyclable frame filter

Abstract

The invention refers to a recyclable frame filter comprising a frame and a nonwoven zig- zag folded filter medium, wherein the filter medium is connected to the frame by connecting means, and wherein the filter medium, the frame and the connecting means are at least substantially made of the same plastic material, in particular polypropylene.

Description

[0001] Recyclable frame filter

[0002] Related Applications

[0003] This application claims the benefit of priority of U.S. Provisional Application No. 63 / 533,556, filed on August 18, 2023, the entire contents of which application(s) are incorporated herein by reference.

[0004] Field of the Invention

[0005] The present invention relates generally to a recyclable frame filter with a frame and a nonwoven zig-zag folded filter medium, wherein the filter medium is connected to the frame by a connector or a connecting means.

[0006] Background of the Disclosure

[0007] Frame filters generally have a flat filter material which has been formed into a zig-zag shape in order to enlarge the filter surface. This results in the formation of pleats with angled pleat walls, each pleat wall being bounded by pleat ridges. Transverse to pleat ridges, an edge element is attached to the edges of the pleat walls forming the frame. On the one hand, the edge elements ensure dimensional stability of the filter element and, on the other hand, provide a seal which prevents unpurified supply air from flowing around the filter element in the filter housing in which the filter element is arranged.

[0008] Such a frame filter generally has a box-like shape. The filter material is usually made of nonwoven being produced in a melt blowing or melt spinning process based on plastic material.

[0009] The document EP 1 161 978 B1 refers to a filter arrangement for air which is recirculated in buildings, in particular in combination with air conditioners, comprising pleated filter material and a frame holding the filter material, the filter material and the frame comprising in particular polypropylene, characterized in that the filter material is continuous-fiber polypropylene nonwoven. of the Disclosure

[0010] It is an object of the invention to provide an improved frame filter. In particular, it is an object of the invention to simplify recycling of a frame filter.

[0011] In some of its aspects, this problem is solved by the teachings of the independent claims, for example. Advantageous embodiments are also defined in the dependent claims. A first exemplary aspect of the present invention includes a recyclable frame filter comprising a frame and a nonwoven zig-zag folded filter medium, wherein the filter medium is connected to the frame by a connecting means or a connector, and wherein the filter medium, the frame and the connecting means or wherein the filter medium, the frame and the connector are at least substantially made of the same plastic material, for example, polypropylene (PP). Suitable connecting means or connectors for use in the present invention include: beads or dots of attaching material, for example the plastic material.

[0012] A second exemplary aspect of the present invention includes a method for producing a recyclable frame filter of the present invention, comprising the steps of: providing a nonwoven filter medium made from a plastic material; embossing the filter medium; cutting the filter medium; zig-zag folding the filter medium; providing a frame for the filter medium made from the plastic material; and attaching or adhering the frame to the zig-zag folded filter medium by a connecting means or a connector made from the plastic material.

[0013] A preferred embodiment of the method for recycling a frame filter further comprises the step of: generating plastic granulate from the pieces. By drying the pieces of the plastic material to be recycled and then generating plastic granulate from those pieces by cutting and / or melting the pieces, the inventive frame filters can be completely recycled.

[0014] A third exemplary aspect of the present invention includes a method for recycling a frame filter, comprising the steps of: hackling or shredding the whole frame filter in pieces; and separating dirt particles from the plastic material by submerging the pieces in a liquid, preferably water, bath, wherein the pieces float to a surface of the liquid bath while the dirt particles mostly sink to a ground of the liquid bath.

[0015] A preferred embodiment of the method for recycling a frame filter further comprises the step of: setting the water in motion in order to support the separating. By applying motion, the dirt is separated from the plastic material to be recycled even better. A further embodiment of the method for recycling a frame filter further comprises the step of: drying the pieces. A “plastic” material as used herein is defined to encompass both single materials or blends of plastic materials. Preferably, the plastic material is polypropylene or polyethylene.

[0016] “Non-adhesive joining” as used herein is defined to mean that a connection is between two elements is established without the use of glue or adhesive.

[0017] As used herein, the term “means” is intended to invoke 35 U.S.C. 112(f), such as “connector means”, for example. In contrast, terms that do not include the word “means”, such as “connector”, for example, are not intended to invoke 35 U.S.C. 112(f).

[0018] “Connecting means” and / or “stabilizing means” as used herein are optionally a bead or a dot of attaching material, in particular plastic material.

[0019] In another of its aspects, the present invention is based on the idea not only to use the frame and the filter medium of the same plastic material but to use only one single plastic material for the production of the whole frame filter, i.e. also those parts of the filter that connect and / or reinforce its components in addition to those that perform a filtering function. The present invention may achieve this by applying the plastic material on elements of the frame filter in a molten condition. After hardening, the plastic material forms the connecting means or the connector between the elements of the frame filter.

[0020] If the frame, the filter medium, and the connecting means or the connector are made from the same plastic material, the whole frame filter becomes mono-material. This makes recycling particularly easy since no different materials of the frame filter have to be separated before being able to start a recycling process. This saves time, energy, and cost. Furthermore, the use of an expensive glue for gluing plastic materials potentially harmful to the environment can be avoided.

[0021] Also, the use of the connecting means or the connector of the same plastic material to adhere the frame to the filter medium in a non-adhesive joining manner avoids problems with the adhesiveness of glues on some plastic materials: in particular polypropylene-glues are difficult to realize due to the physical surface properties of polypropylene.

[0022] The inventive method for producing a recyclable frame filter in accordance with the present invention has the further advantage, that the frame filter can be assembled in a fast and simple manner without having to use glue to connect the filter medium to the frame.

[0023] The inventive method for recycling a frame filter has the further advantage that dirt can be effectively separated from the plastic material to be recycled. Plastic such as PP has a smaller density than water and floats. Dust and dirt particles mostly sink to the ground in water. An advantage for a recycling process in accordance with the present invention is that the whole frame filter can be processed without having to separate its components, if possible at all.

[0024] In one preferred embodiment of the frame filter in accordance with the present invention, adjacent pleats of the zig-zag folded filter medium comprise a stabilizing means or a stabilizer which are formed from by the same plastic material. In other words, the stabilizing means or the stabilizer are made of the same plastic material as the filter medium, the frame and the connecting means or the connector. Preferably, the frame, the filter medium, the connecting means or the connector and the stabilizer or stabilizing means comprise the same material or even consist of the same material.

[0025] Depending on the material of the filter medium and the depth and width of the pleats, it is useful to provide a stabilizer stabilizing means in order to stiffen the filter medium. Also, the pleating angle can be optimized by those the stabilizer or stabilizing means. In order to enhance the advantages properties regarding recycling of the inventive frame filter, such a stabilizing means or a stabilizer are also made at least substantially of the same plastic material as the filter medium and frame. In particular stabilizers or stabilizing means which are disposed on the filtering surface of the filter medium are difficult to separate from the filter medium in recycling processes. Therefore, it is a highly advantageous if the stabilizer or stabilizing means are of the same plastic material as the filter medium. Preferably, the stabilizer or stabilizing means of the present invention are preferably an integral part of the filter medium or inserted in the filter medium. More preferably, the stabilizer or stabilizing means are struts or beams or beads or dots.

[0026] In a further preferred embodiment of the frame filter in accordance with the present invention, the connecting means or the connector and / or the stabilizer or stabilizing means are beads of the same plastic material as that of the filter medium and frame.

[0027] The beads of plastic material can be applied to the filter medium and / or the frame in a very effective manner. The beads can be continuous or intermittent. Particularly, the beads can be applied to a comparatively large surface in a small amount of time. This is advantageous, since the molten plastic material used for the connecting means or the connector may cool off fast.

[0028] In a further preferred embodiment of the frame filter of the present invention, the stabilizer or stabilizing means may extend substantially parallel to the long edges of the frame filter. In a further preferred embodiment of the frame filter of the present invention, the stabilizer or stabilizing means are arranged on both sides or only on one side of the filter medium.

[0029] If the stabilizer or stabilizing means are arranged on only one side of the filter medium, the production process is a simplified. If the stabilizer or stabilizing means are arranged on both sides of the filter medium, the filter medium is further stiffened. In this case, preferably, the stabilizer or stabilizing means is then arranged neighboring each other on both sides of the filter medium.

[0030] In a further preferred embodiment of the frame filter of the present invention, the stabilizer or stabilizing means are embossings disposed in the filter medium. Embossings give a relatively high rigidity to the filter medium while not deteriorating the recyclability of the frame filter.

[0031] In a further preferred embodiment of the frame filter of the present invention, the stabilizer or stabilizing means extends at least substantially perpendicular to pleat ridges of the zigzag folded filter medium. This orientation enhances stability with respect to forces in a direction in which the stabilizer or stabilizing means extend while the stability in the direction of the pleat ridges is provided by the pleat ridges.

[0032] In a further preferred embodiment of the frame filter, the stabilizer or stabilizing means connects adjacent pleats at least on one side of the filter medium by non-adhesive joining, wherein a plurality of fibers of the nonwoven filter medium are joined at respective intermediate areas of contacting adjacent pleats.

[0033] When the stabilizer or stabilizing means connects adjacent pleats, the angle of a V formed by the pleat can be exactly defined. Therefore, beads on the adjacent pleats may be brought into contact and form a spacer when hardening. Preferably, two beads are applied on each pleat arranged on each other such that the spacer becomes larger. This has the effect that larger angles of the Vs formed by the pleat can be achieved.

[0034] In a further preferred embodiment of the frame filter of the present invention, the connecting means or the connector and / or the stabilizer or stabilizing means are formed by hardening from the molten plastic material.

[0035] Forming the stabilizing means or a stabilizer from the molten plastic material provides a high degree of flexibility regarding adjustment of the angle of a V formed by the pleats. Furthermore, the contour of the pleats remains firm after hardening and does not require any further retaining. Although, a relatively high firmness of the pleats of the filter medium in the frame filter is achieved. In a further preferred embodiment of the frame filter of the present invention, the frame is formed in one single piece.

[0036] By forming the frame in one piece, the frame filter is further solidified. This is especially advantageous if the frame is relatively flexible, e.g., has a foamed finishing or nonwoven finishing. In combination with such flexible finishing or material, the process of fixing the filter medium to the frame can be accelerated by forming the frame in one piece.

[0037] In a further preferred embodiment of the frame filter of the present invention, the frame is formed by the plastic material in a foldable finishing.

[0038] If the plastic material is foldable, the frame can be applied to the size of a filter element formed by the pleated filter medium having a rectangular, quadratic, or tetragonal shape. This simplifies the production process and also accelerates the time span for fixing the frame to the filter element.

[0039] In a further preferred embodiment of the frame filter of the present invention, the frame is formed by the plastic material in a foamed finishing or nonwoven finishing, or an injection molded or extruded finishing. Especially the foamed finishing and nonwoven finishing are flexible in a manner that they can be folded. However, extruded finishings may be advantageous where a high degree of stiffness of the frame is desired.

[0040] In a further preferred embodiment of the frame filter of the present invention, the frame has the form of a strip and is wrapped around the filter medium along a first terminal pleat, a first face side, a second terminal pleat and a second face side of the filter medium and is connected to the first terminal pleat, the first face side, the second terminal pleat and the second face side of the filter medium.

[0041] By wrapping the frame around the filter medium, a particularly simple and fast manner of installing the frame to the filter medium is realized. Furthermore, the beads of molten plastic material can be applied to the strip in one or several lines which is preferably the production direction of the frame.

[0042] In a further preferred embodiment of the frame filter of the present invention, the strip has embossed folding edges, wherein the distances of the embossed folding edges on the strip are adapted to the respective dimensions of the first face side, the second terminal pleat and the second face side of the filter medium. If the strip is embossed to define the folding edges, the folding around a rectangular, quadratic, or tetragonal filter element is simplified and accelerated. In a further preferred embodiment of the frame filter of the present invention, the strip has three or four embossed folding edges extending at least substantially perpendicular to a longitudinal direction of the strip. The number of the embossed folding edges depends on the form of the element of the filter medium.

[0043] In a further preferred embodiment of the frame filter of the present invention, the short edges of the strip border on each other, in particular are connected with each other. This provides a particularly stable frame.

[0044] In a further preferred embodiment of the frame filter of the present invention, the frame has seams that enclose the zig-zag folded filter medium in a form fitting manner.

[0045] Preferably, the frame forms a U-shaped profile that surrounds the filter element formed by the pleated medium. In this case, the pleated filter medium has a stable and tight seat in the frame.

[0046] In a further preferred embodiment of the frame filter of the present invention, the seams are embossed along the long edges of the strip. If the seams are defined on the body of the frame by embossings, formation of the U-shaped profile is simplified and accelerated.

[0047] In a further preferred embodiment of the frame filter of the present invention, the seams of the frame are at least partly mitered in the region of the edges of the frame, whereby overlapping parts, if any, are connected, in particular thermobonded.

[0048] In a further preferred embodiment of the frame filter of the present invention, overlapping parts of the seams of the frame, partly mitered or not, are also pressed and / or molten at the same time to make sure the overlapping parts are at the same height as the remaining frame. The flat surface of the filter frame helps seal the filter to a holding frame in its application.

[0049] By mitering the seams, the frame has the same thickness in the region of the edges of the frame as in the other regions of the frame. This enhances the precision and evenness of the frame filter dimensions. This is important, e.g., if the frame filter is to be installed in a surrounding of standardized size, such as a holding fixture.

[0050] In a further preferred embodiment of the frame filter of the present invention, the connecting means or the connector is formed by applying beads of the plastic material in molten condition onto the strip of the filter medium and only thereafter wrapping the strip with the applied beads of plastic material around the zig-zag folded filter medium. Preferably, the beads cross folding edges of the strip. Then, the molten plastic material hardens while connecting the frame with the pleated filter medium.

[0051] The connecting means or the connector according to this embodiment can be particularly firm and easy to install.

[0052] In a further preferred embodiment of the frame filter of the present invention, the stabilizer or stabilizing means is formed by applying beads of the melted plastic material onto a flat layer of the filter medium and only thereafter folding the filter medium into a series of parallel pleats so as to realize the zig-zag folded filter medium. Preferably, the beads cross the pleat ridges in a substantially perpendicular direction. Thereafter, the molten plastic material hardens stabilizing the filter medium, in particular the pleats.

[0053] The stabilizer or stabilizing means, in particular spacers, according to this embodiment can be particularly firm and easy to install.

[0054] In a further preferred embodiment of the frame filter of the present invention, a first surface and / or a second surface of respective adjacent pleats, at least in part, comprise loops and / or hooks, in particular in a region of embossings, which are designed to engage upon the non-adhesive joining at the respective intermediate area of contacting pairs of embossings and which in particular are formed by at least one of the plurality of fibers forming the nonwoven filter medium.

[0055] Preferably, this advantageous embodiment is of a type of hook-and-loop or Velcro® brand fastening. This type of non-adhesive joining enables the joining process to be of particularly simple design since the adjacent layers only need to be pressed together when the filter medium is pleated.

[0056] In a further preferred embodiment of the frame filter of the present invention, the plurality of fibers of the nonwoven filter medium of contacting pairs of embossings are partially fused at respective intermediate areas of contacting adjacent pleats. Individual fibers of at least one of the adjacent pleats thereby fuse with one or more fibers of the other adjacent pleat. Preferably, individual fibers of both adjacent pleats respectively fuse with individual fibers of the respective other adjacent pleat and vice versa.

[0057] This advantageous embodiment is characterized by the non-adhesive joining substantially occurring only at the surface of the filter material, particularly by the fibers forming the surface of the nonwoven filter medium. This substantially preserves the material structure, in particular the fibrous structure, of the filter medium. The effective filtration area is also enlarged in this advantageous embodiment by realizing the embossings, particularly the first and second embossing, with particle filtration and the flow of fluid to be filtered still being possible even at the intermediate area formed by adjoining embossings of adjacent pleats.

[0058] Preferably, this filter medium for a frame filter is obtained or obtainable by thermal treatment of a surface of the filter medium by way of a first heating device at least partly melting fibers of opposite first embossings and joining the first embossings.

[0059] In a further preferred embodiment of the frame filter of the present invention, the stabilizer or stabilizing means is obtained or obtainable by brushing a first surface of the filter medium such that loops and / or hooks are produced on the surface of the filter medium, preferably on the embossings, which engage at a first intermediate area of contacting adjacent pleats and form the non-adhesive joining.

[0060] Such a Velcro®-like connection can be easily fastened and unfastened by pressing pleats or pulling apart pleats.

[0061] The features and effects described with respect to each of the above individual aspects of the present invention apply also to all the other aspects of the invention, alone or in combination, and vice-versa.

[0062] In a preferred embodiment of the method for producing a recyclable frame filter in accordance with the present invention, providing a frame comprises the further sub-steps of: providing a layer made from the plastic material; embossing the layer; and cutting the layer in at least one strip; and wherein adhering the frame comprises the further steps of: applying first beads of the plastic material in molten physical condition to the strip; and folding the strip around the zig-zag folded filter medium such that the first beads form the connecting means or the connector connecting the strip to the filter medium after hardening and that the strip forms the frame for the filter medium.

[0063] The use of plastic beads as the connector or as the connecting means between the filter medium and the frame is a tricky task, since plastic materials in the molten state are more difficult to process than conventional plastic glues which are offered by chemical industry in a great variety. In particular, the time to cure is very short for PP, while the open or working time of conventional adhesives is increased and made flexible by admixtures of other materials. In addition, when hot PP at a temperature above the melting temperature touches other PP components, those other PP components could also melt as a result.

[0064] However, by the particular manufacturing process found by the inventors, the connecting means or the connector between the frame and the filter medium can be formed based on a plastic material. On the one hand, the time between application of the plastic beads to the layer and the connection with the filter medium can be kept very short. The melting of other PP components is circumvented by small contact areas and high heat dissipation, once the plastic beads are in contact with the frame and the filter medium.

[0065] A further preferred embodiment of the method for producing a recyclable frame filter comprises the step of: applying second beads of the plastic material in molten physical condition to at least one side of the filter medium, wherein the second beads form a stabilizing means or a stabilizer connecting adjacent pleats after the filter medium has been zigzag folded. According to this preferred embodiment, also the stabilizer or stabilizing means or spacers can be formed without the use of a plastic glue.

[0066] Brief Description of the Drawings

[0067] Further features and advantages of the invention are described in the following with respect to the figures. These depict at least partly schematically:

[0068] Figure 1 schematically illustrates an exemplary configuration of a perspective view of an embodiment of a pleated filter medium;

[0069] Figure 2 schematically illustrates an exemplary configuration of a perspective view of an embodiment of a frame filter with a pleated filter medium of figure 1 ;

[0070] Figure 3 schematically illustrates a top view of the frame filter of figure 2;

[0071] Figure 4 schematically illustrates an exemplary configuration of a detailed section of one pleat of the pleated filter medium of figure 1 ;

[0072] Figure 5 schematically illustrates an exemplary configuration of a top view of an embodiment of a strip for forming a frame filter according to figures 2 and 3;

[0073] Figure 6 schematically illustrates an exemplary configuration of an enlarged top view of the area A of the strip of figure 5; Figure 7 illustrates an exemplary configuration of a block diagram of an embodiment of a method for producing a recyclable frame filter; and

[0074] Figure 8 illustrates an exemplary configuration of a block diagram of an embodiment of a method for recycling a frame filter.

[0075] Detailed Description of the Disclosure

[0076] Referring now to the figures, wherein like elements are numbered alike throughout, Figure 1 shows a perspective view of an embodiment of a pleated filter medium 3 forming a filter element for a frame filter 1 (not depicted).

[0077] The filter medium 3 has pleats 5A, 5B of a folded nonwoven which is capable of filtering particles such as dirt from a fluid, for example from water or air. The material of the nonwoven is preferably polypropylene or polyethylene or any other plastic material being suitable for forming nonwovens.

[0078] The filter medium 3 is preferably reinforced by beads 6 of the same material as the nonwoven extending substantially in a direction perpendicular to the ridges of the pleats 5A, 5B and forming a stabilizing means or a stabilizer for the filter medium. Preferably, the beads 6 are arranged on only one side of the filter medium 3. However, it is also possible to arrange the beads 6 on both sides of the filter medium 3. The beads 6 preferably form a line and have been applied in a molten physical condition. Preferably, the beads 6 extend in an at least substantially perpendicular direction to pleat ridges 17 of the filter medium 3. When hardening from the molten state, the beads 6 connect to the filter medium 3 forming the stabilizer or stabilizing means.

[0079] As shown in figure 1 , adjacent pleats 5A, 5B of the filter medium 3 are connected by the beads 6 which extend in the spaces between adjacent pleats 5A, 5B. As is the case in the embodiment of figure 1 , the filter element formed by the pleated filter medium 3 is often a cuboid having large upstream and downstream faces and smaller faces which are denominated in the following as first terminal pleat 7, first face site 8, second terminal pleat 9, and second face side 10.

[0080] Figure 2 is a perspective view of an embodiment of a frame filter 1 with a pleated nonwoven filter medium 3 according to figure 1 .

[0081] In addition to the filter medium 3, the frame filter 1 comprises a frame 2. The frame 2 encloses the filter medium 3, preferably as a U-shaped profile. The frame 2 is at least predominantly made from the same material as the filter medium 3 and the beads 6. The frame 2 is fixed to the filter element of pleated filter medium 3 by further beads 4 (not visible in this view but in Fig. 6) forming the connecting means or the connector. Also the further beads 4 are at least predominantly made from the same material as the nonwoven of the filter medium 3 and the frame to 2. As the other beads 6 forming the stabilizing means or a stabilizer, the further beads 4 are preferably applied in a molten physical condition and connect to the filter medium 3 and the frame 2 when hardening. After hardening, the further beads 4 therefore form the connecting means or the connector between the filter medium 3 and the frame 2.

[0082] The frame 2 may be injection molded or extruded. Alternatively, the frame 2 may have a foamed finishing or nonwoven finishing. In the latter case, the frame 2 is comparatively flexible and can be formed departing from a layer of plastic material. This layer of plastic material is cut and embossed and then folded or wrapped around the filter medium 3. Preferably, the layer of plastic material has seams 13 which are folded around the edges of the pleated filter medium 3 and are also fixed to the filter medium 3. These seams 13 preferably form the limbs of the U-shaped profile. This will be explained in greater detail with respect to figures 5 and 6. Overlapping parts 16 of the seams 13 overlapping at the edges or corners of the pleated filter medium 3 are preferably joined by thermobonding.

[0083] In any case, the frame 2 is preferably one single piece and not assembled from several components.

[0084] Figure 3 is a schematic top view of the frame filter 1 according to figure 2.

[0085] As can be seen in figure 3, the beads 6 forming the stabilizer or stabilizing means of adjacent pleats 5A, 5B come into contact in intermediate areas 14 of the pleats 5A, 5B in the space between these pleats 5A, 5B. The pleats are delimited by pleat ridges 17 of the pleats 5A, 5B, extending substantially perpendicular to the beads 6. The beads 6 are represented as elongated continuous cluster of plastic material. However, the beads 6 may also be dots of plastic material.

[0086] Preferably, these intermediate areas 14 are connected by non-adhesive joining.

[0087] Instead of beads, stabilizer or stabilizing means 6 can be formed by other non-adhesive joinings at respective intermediate areas 14 of adjacent pleats 5A, 5B, such as fused fibers of the nonwoven filter medium on the surfaces of the pleats 5A, 5B or hook-and-loop or Velcro fastening on the surfaces of the pleats 5A, 5B. In addition, to a non-adhesive joining, the stabilizer or stabilizing means 6 may be formed by stabilizing embossings in the pleats 5A, 5B. These stabilizing embossings preferably not only serve as a stabilizing means or a stabilizer 6 but also as spacers to keep a defined distance between adjacent pleats and to keep the legs of a pleat in a defined angle with respect to each other.

[0088] Preferably, the stabilizing embossings form a macrostructure such as a triangular prism. In particular, the stabilizing embossings may have rounded edges in order to ease the embossing process in the filter medium 3.

[0089] Also in this embodiment, the adhesive joinings and / or the stabilizing embossings forming the stabilizer or stabilizing means 6 extend preferably in an at least substantially perpendicular direction to pleat ridges 17 of the filter medium 3.

[0090] Figure 4 is a schematic section of a single pleat 5 in the area of a bead 6 forming the stabilizing means or a stabilizer of filter medium 3 in figure 3.

[0091] In figure 4, a pleat ridge 17 of the pleat 5 is a folding edge. However, this pleat ridge 17 may also be rounded or embossed or include even two or more embossed folding edges. On the filter medium forming the pleat 5, a stabilizing means or a stabilizer 6A, 6B is arranged. As demonstrated in figure 4, this bead 6 forming the stabilizing means or a stabilizer may include a first bead 6A and a second bead 6B which is situated on the first bead 6A.

[0092] With this arrangement, the bead 6 forming the stabilizer or stabilizing means can serve as a spacer between the adjacent pleats 5A, 5B, providing for a larger space between adjacent pleats 5A, 5B, and i.e. a larger angle between the legs of one pleat 5A, 5B, compared to a single bead.

[0093] Figure 5 is a top view of an embodiment of a strip 2 for forming a frame of a frame filter 1 presented in figures 2 and 3.

[0094] As mentioned above, the strip 2 is preferably made from a layer of plastic material. In order to be foldable around the pleated filter medium 3, the strip has to be made from a flexible material. Examples of such flexible materials are foamed plastic materials or nonwoven plastic materials. Preferably, in the case of a nonwoven plastic material, this material can be further compacted.

[0095] When the strip 2 is in place around the pleated filter medium 3, forming the frame, short edges 12 of the strip 2 border on each other, in particular are connected with each other.

[0096] The strip 2 presented in figure 5 is adapted for a quadratic or square frame filter 1 (not shown). Therefore, each element of the strip 2 has the same longitudinal dimension. Each of the elements is separated from the neighboring elements by a folding embossing 11.

[0097] These folding embossings 11 serve as folding edges.

[0098] Figure 6 is an enlarged view of the area A according to figure 5.

[0099] The elements of the strip 2 also have seams 13 that are formed by embossings 15 extending in the longitudinal direction of the strip 2. As explained above, these seams 13 serve to enclose the filter medium 3 in the frame formed by the folded strip 2. The seams 13 are for this purpose also folded at the folding edges formed by embossings 15.

[0100] The dotted lines with the reference numeral 4 represent the further beads of plastic material that are placed in a molten physical condition on the strip 2, before the strip 2 is folded around a pleated filter medium 3 to form the frame of the frame filter 1 . The further beads 4 are represented as elongated continuous cluster of plastic material. However, the further beads 4 may also be dots of plastic material.

[0101] As can be seen in the figure, these further beads 4 are arranged in parallel to the longitudinal direction of the strip 2. When the strip 2 is folded around the pleated medium, the further beads 4 additionally get into contact with the filter medium 3 and form the connecting means or the connector between the frame 2 and the filter medium.

[0102] Figure 7 is a block diagram of an embodiment of a method 100 for producing a recyclable frame filter 1 .

[0103] Preferably, the produced frame filter 1 is similar to the frame filters described with respect to the embodiments of figures 2 and 3.

[0104] In a first step 101 of the method, a nonwoven filter medium made from a plastic material is provided. In a second step 102, the filter medium 3 is embossed. In a third step 103, the filter medium 3 is cut. In a fourth step 104, preferably second beads 6 of the plastic material are applied in molten physical condition to the upstream side and / or to the downstream side of the filter medium 3. While the second beads 6 are cooling down, in a fifth step 105, the filter medium 3 is zigzag folded. After the second beads 6 have hardened, these form the stabilizer or stabilizing means for the pleated filter medium 3. Depending on the dimension of the second beads 6, these also serve the spacers for adjacent pleats 5A, 5B of the filter medium 3. In order to achieve a larger spacing between the pleats 5A, 5B, the fourth step 104 may be executed twice such that a twofold bead of plastic material is formed on the filter medium 3, as represented in figure 4. Preferably, such spacers are arranged on the upstream side and on the downstream side of the filter medium 3. Alternatively, the spacers are only formed on one side of the filter medium 3 while on the other side, there is no second bead 6 ora relatively small second bead 6 which only serves for reinforcing but not for connecting adjacent pleats 5A, 5B.

[0105] In a sixth step 106, a layer made from the plastic material used for the filter material and the second beads 6 is provided. The plastic material shall be flexible enough to be folded, such as certain plastics in a foamed finishing or nonwoven finishing. In a seventh step 107, the layer is embossed. In particular, the first folding embossings 11 and the second folding embossings 15 are inserted in the layer. In an eight step 108, the layer is cut into at least one strip 2. In a ninth step 109, first beads 4 of the plastic material used for the filter medium 3 and the layer are applied to the strip 2 in a molten physical condition. These first beads 4 form the connector or the connecting means after hardening. While the first beads 4 are cooling down, the strip 2 is folded around the zig-zag folded filter medium such that the first beads 4 form the connecting means or the connector connecting the strip 2 to the filter medium 3. After hardening of the connecting means or the connector 4, the strip 2 forms the frame for the frame filter 1 . In a tenth step 110, the strip 2 is folded around the zig-zag folded filter medium such that the first beads 4 form the connector or connecting means connecting the strip 2 to the filter medium 3 after hardening and that the strip 2 forms the frame for the filter medium 3.

[0106] In general, the order of the steps of the method 100 is not bound to the order given by the numbering of the steps. For example, the embossing step 100 can be executed after the cutting step 103, or the embossing step 107 can be executed after the cutting step 108.

[0107] Figure 8 is a block diagram of a method 200 for recycling a frame filter 1 , in particular for recycling a frame filter according to the embodiment according to figures 2 and 3.

[0108] Recycling frame filters is getting to be more and more important. The frame filters presented above have outstanding capabilities of being recycled, since they can be produced as mono-material filters. A mono-material recyclate of raw materials is the basis for the reuse of used frame filters, in particular to produce new frame filters. In contrast, frame filters of several materials have to be mostly burned after use.

[0109] With the frame filters described above, it is possible to recycle the whole frame filter without a physical or chemical separation process of different plastic materials.

[0110] A method 200 for recycling the mono-material frame filter comprises as a first step 201 the hackling of the whole frame filter 1 into pieces. In a second step 202, particles are separated from the plastic material by submerging the pieces in a bath of liquid, such as water. In this liquid, the pieces float to a surface of the bath while the particles mostly sink to a ground of the bath.

[0111] Preferably, in the third step 203, the liquid is set into motion in order to encourage the separation. In a further preferred fourth step 204, the pieces are dried. In a further preferred fifth step 205, plastic granulate is generated from the pieces. In particular, the pieces are melted and the granulate is extruded from the molten raw material. Further cleaning and / or filtering steps of the molten raw material may be applied. Furthermore, the molten recyclate raw material may be mixed with new raw material, in particular recyclate granulate may be mixed with new granulate, before being used for producing new plastic products, in particular new filter medium.

[0112] In general, the order of the steps of the method 200 is not bound to the order given by the numbering of the steps. For example, the liquid may be set into motion before submerging the hackled pieces in the water bath.

[0113] In the following, embodiments are described. The features of these embodiments can be combined to form other embodiments:

[0114] In one embodiment, a recyclable frame filter comprises a frame 2 and a nonwoven zig-zag folded filter medium 3, wherein the filter medium 3 is connected to the frame 2 by connecting means or a connector 4, and wherein the filter medium 3, the frame 1 and the connecting means or the connector 4 are at least substantially made of the same plastic material, in particular polypropylene.

[0115] In a further embodiment of a recyclable frame filter 1 , adjacent pleats 5a, 5b of the zig-zag folded filter medium 3 comprise stabilizing means or a stabilizer 6 which are formed at least substantially by the plastic material.

[0116] In a further embodiment of a recyclable frame filter 1 , the connecting means or the connector 4 and / or the stabilizer or stabilizing means 6 are beads of the plastic material.

[0117] In a further embodiment of a recyclable frame filter 1 , the stabilizer or stabilizing means 6 are arranged on both sides or only on one side of the filter medium 3.

[0118] In a further embodiment of a recyclable frame filter 1 , the stabilizer or stabilizing means 6 are stabilizing embossings, in particular forming a macrostructure, in the filter medium 3. In a further embodiment of a recyclable frame filter 1 , the stabilizer or stabilizing means 6 extend at least substantially perpendicular to pleat ridges 17 of the zig-zag folded filter medium 3.

[0119] In a further embodiment of a recyclable frame filter 1 , the stabilizer or stabilizing means 6 connect adjacent pleats 5a, 5b at least on one side of the filter medium 3 by non-adhesive joining, wherein a plurality of fibers of the nonwoven filter medium 3 are joined at respective intermediate areas 14 of contacting adjacent pleats 5a, 5b.

[0120] In a further embodiment of a recyclable frame filter 1 , the connecting means or the connector 4 and / or the stabilizer or stabilizing means 6 are formed from the plastic material in a molten physical condition.

[0121] In a further embodiment of a recyclable frame filter 1 , the frame 2 is formed in one piece.

[0122] In a further embodiment of a recyclable frame filter 1 , the plastic material of the frame 2 has a foldable finishing.

[0123] In a further embodiment of a recyclable frame filter 1 , the plastic material of the frame 2 has a foamed finishing or nonwoven finishing, or an injection molded or extruded finishing.

[0124] In a further embodiment of a recyclable frame filter 1 , the frame 2 has the form of a strip and is wrapped around the filter medium 2 along a first terminal pleat 7, a first face side 8, a second terminal pleat 9 and a second face side 10 of the filter medium 3 and is connected by the connecting means or the connector 4 to the first terminal pleat 7, the first face side 8, the second terminal pleat 9 and the second face side 10 of the filter medium 3.

[0125] In a further embodiment of a recyclable frame filter 1 , the distances of the folding embossings 11 on the strip 2 are adapted to the respective lengths of the first terminal pleat 7, the first face side 8, the second terminal pleat 9 and the second face side 10 of the filter medium.

[0126] In a further embodiment of a recyclable frame filter 1 , the frame 2 has seams 13 that enclose the zig-zag folded filter medium 3 in a form fitting manner.

[0127] In a further embodiment of a recyclable frame filter 1 , the seams 13 of the frame 2 are at least partly mitered in the region of the short edges 12 of the frame 2, whereby overlapping parts 16, if any, are connected to each other, in particular by thermobonding.

[0128] In one embodiment, a method 100 for producing a recyclable frame filter 1 comprises the steps of: providing 101 a nonwoven filter medium 3 made from a plastic material; embossing 102 the filter medium 3; cutting 103 the filter medium 3; zig-zag folding 105 the filter medium 3; providing 106, 107, 108 a frame for the filter medium 3 made from the plastic material; and adhering 109, 110 the frame 2 to the zig-zag folded filter medium 3 by connecting means made from the plastic material.

[0129] In a further embodiment of a method 100, providing a frame 2 comprises the further substeps: providing 106 a layer made from the plastic material; embossing 107 the layer; and cutting 108 the layer in at least one strip 2; and wherein adhering the frame comprises the further steps of: applying 109 first beads 4 of the plastic material in molten physical condition to the strip 2; and folding 110 the strip 2 around the zig-zag folded filter medium such that the first beads 4 form connecting means connecting the strip 2 to the filter medium 3 after hardening and that the strip 2 forms the frame for the filter medium 3.

[0130] In a further embodiment a method 100 comprises the steps of: hackling 201 the whole filter frame 1 in pieces; and separating 202 dirt particles from the plastic material by submerging the pieces in a water bath, wherein the pieces float to a surface of the water bath while the dirt particles mostly sink to a ground of the water bath. It should also be noted that the exemplary embodiments are merely examples which are not intended to limit the scope of protection, the applications and the structure in any way. Rather, the preceding description provides the skilled person with a guideline for the implementation of at least one working example, whereby various modifications, in particular with respect to the function and arrangement of the described components, can be made without leaving the scope of protection as it results from the claims and feature combinations being equivalent to these claims. For example, even if the frame filter 1 according to the described embodiments has quadratic upstream and downstream sides, the skilled person understands that the invention can be realized with any form of a frame filter.

[0131] List of numerals

[0132] 1 frame filter

[0133] 2 frame

[0134] 3 filter medium

[0135] 4 connecting means or connector / further bead

[0136] 5, 5A, 5B pleat

[0137] 6 stabilizing means or a stabilizer / bead

[0138] 7 first terminal pleat

[0139] 8 first face side

[0140] 9 second terminal pleat

[0141] 10 second face side

[0142] 11 folding embossing

[0143] 12 edge

[0144] 13 seam

[0145] 14 intermediate area

[0146] 15 embossing

[0147] 16 overlapping part

[0148] 17 pleat ridge

Claims

Claims1 . A recyclable frame filter (1), comprising a frame (2) and a nonwoven zig-zag folded filter medium (3), wherein the filter medium (3) is connected to the frame (2) by, in particular a, connecting means or a connector (4), and wherein the filter medium (3), the frame (1) and the connecting means or the connector (4) are at least substantially made of the same plastic material, in particular polypropylene.

2. The recyclable frame filter (1) according to claim 1 , wherein adjacent pleats (5a, 5b) of the zig-zag folded filter medium (3) comprise, in particular a, stabilizing means or a stabilizer (6) which are formed at least substantially by the plastic material.

3. The recyclable frame filter (1) according to claim 1 or 2, wherein the connecting means or the connector (4) and / or the stabilizer or stabilizing means (6) are beads of the plastic material.

4. The recyclable frame filter (1) according to claim 2 or 3, wherein the stabilizer or stabilizing means (6) are arranged on both sides or only on one side of the filter medium (3).

5. The recyclable frame filter (1) according to claim 2, wherein the stabilizer or stabilizing means (6) are stabilizing embossings, in particular forming a macrostructure, in the filter medium (3).

6. The recyclable frame filter (1) according to any one of claims 2 to 5, wherein the stabilizer or stabilizing means (6) extend at least substantially perpendicular to pleat ridges (17) of the zig-zag folded filter medium (3).

7. The recyclable frame filter (1) according to any one of claims 2 to 6, wherein the stabilizer or stabilizing means (6) connect adjacent pleats (5a, 5b) at least on one side of the filter medium (3) by non-adhesive joining, wherein a plurality of fibers ofthe nonwoven filter medium (3) are joined at respective intermediate areas (14) of contacting adjacent pleats (5a, 5b).

8. The recyclable frame filter (1 ) according to any one of the preceding claims, wherein the connecting means or the connector (4) and / or the stabilizer or stabilizing means (6) are formed from the plastic material in a molten physical condition.

9. The recyclable frame filter (1 ) according to any one of the preceding claims, wherein the frame (2) is formed in one piece.

10. The recyclable frame filter (1) according to any one of the preceding claims, wherein the plastic material of the frame (2) has a foldable finishing.

11. The recyclable frame filter (1) according to any one of the preceding claims, wherein the plastic material of the frame (2) has a foamed finishing or nonwoven finishing, or an injection molded or extruded finishing.

12. The recyclable frame filter (1) according to any one of the preceding claims, wherein the frame (2) has the form of a strip and is wrapped around the filter medium (2) along a first terminal pleat (7), a first face side (8), a second terminal pleat (9) and a second face side (10) of the filter medium (3) and is connected by the connecting means or the connector (4) to the first terminal pleat (7), the first face side (8), the second terminal pleat (9) and the second face side (10) of the filter medium (3).

13. The recyclable frame filter (1 ) according to claim 12, wherein the strip (2) has folding embossings (11), wherein the distances of the folding embossings (11) on the strip (2) are adapted to the respective lengths of the first terminal pleat (7), the first face side (8), the second terminal pleat (9) and the second face side (10) of the filter medium.

14. The recyclable frame filter (1) according to any one of the preceding claims, wherein the frame (2) has seams (13) that enclose the zig-zag folded filter medium (3) in a form fitting manner.

15. The recyclable frame filter (1) according to claim 14, wherein the seams (13) of the frame (2) are at least partly mitered in the region of the short edges (12) of the frame (2), whereby overlapping parts (16), if any, are connected to each other, in particular by thermobonding.

16. Method (100) for producing a recyclable frame filter (1), in particular according to any one of the preceding claims, comprising the steps of: providing (101) a nonwoven filter medium (3) made from a plastic material; embossing (102) the filter medium (3); cutting (103) the filter medium (3); zig-zag folding (105) the filter medium (3); providing (106, 107, 108) a frame for the filter medium (3) made from the plastic material; and adhering (109, 110) the frame (2) to the zig-zag folded filter medium (3) by connecting means made from the plastic material.

17. Method (100) according to claim 16, wherein providing a frame (2) comprises the further sub-steps: providing (106) a layer made from the plastic material; embossing (107) the layer; and cutting (108) the layer in at least one strip (2); and wherein adhering the frame comprises the further steps of: applying (109) first beads (4) of the plastic material in molten physical condition to the strip (2); and folding (110) the strip (2) around the zig-zag folded filter medium such that the first beads (4) form connecting means connecting the strip (2) to the filter medium (3) after hardening and that the strip (2) forms the frame for the filter medium (3).

18. Method (200) for recycling a frame filter (1) according to claim 16 or 17, comprising the steps of: hackling (201) the whole filter frame (1) in pieces; and separating (202) dirt particles from the plastic material by submerging the pieces in a water bath, wherein the pieces float to a surface of the water bath while the dirt particles mostly sink to a ground of the water bath.

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