Method for producing a hollow-cylindrical filter element

Abstract

1. Method 2. A method for producing a hollow-cylindrical filter element (8) for treating fluids, in particular by way of particle filtration, at least consisting of the following production steps: - providing a hollow-cylindrical, preferably pleated filter mat; - printing a flat web at least on one side using a digital printing method; - making up a flat web piece of nonwoven material by separating it from or out of the web; - welding together the longitudinal edges of the web piece, preferably by ultrasound longitudinal seam welding, so as to obtain a closed, hollow-cylindrical nonwoven casing (22); - positioning, preferably erecting, the hollow cylindrical nonwoven casing (22); and - placing the filter mat in the positioned nonwoven casing (8) in such a way that the filter element (8) is produced without any thermal input and that the print (36) applied to the nonwoven casing (22) by the digital printing method faces an observer of the filter element (8).

Description

[0001] METHOD FOR MANUFACTURING A HOLLOW CYLINDRICAL FILTER ELEMENT

[0002] The invention relates to a method for manufacturing a hollow cylindrical filter element for the treatment of fluids, in particular in the form of particle filtration.

[0003] EP 1 015 095 B1 discloses a method for manufacturing a filter element with a fluid-permeable support tube surrounded by a filter mat, which in turn is enclosed by a filter jacket with passages defining a filter chamber and with two end caps arranged at the ends, wherein the filter jacket consists of a plastic material formed from a flat blank, the two ends of which are bent towards each other and are firmly joined together by a seam produced by a hot-melt adhesive, heating element or ultrasonic welding process, forming the filter chamber, wherein the filter mat, which is folded into a cylinder and pushed onto the support tube, has a larger outer diameter than the inner diameter of the filter jacket, and wherein the filter mat is gathered at one of its end faces in such a way as to form a cone that facilitates its insertion into the cylindrical filter jacket.This results in a precise fit of the filter mat within the filter element, so that the filter mat can be supported directly against the filter mantle and the support tube and is thus insensitive to alternating stresses during filter operation.

[0004] DE 10 2019 107 316 B4 discloses a method for manufacturing a filter element for filtering a fluid, in particular a hydraulic fluid, with a filter bellows comprising a flowable filter material, wherein the filter bellows is connected to an outer shell and the outer shell is printed before being connected to the filter bellows, wherein a carrier web made of the material of the outer shell is continuously fed to the filter element, the carrier web is guided planarly at least in one section, and the carrier web is printed in the area of ​​the planar section using a digital printing process.

[0005] - the printed carrier web is wrapped around the filter bellows and joined to it to form the outer shell, whereby a first bead of adhesive is applied to the filter bellows to join the outer shell to the filter bellows and a first layer of the outer shell is brought into contact with the first bead of adhesive to form a first seam, and

[0006] - a second bead of adhesive is applied to the outside of the first layer, extending along the first seam and at least partially covering it, in particular completely covering it.

[0007] Unlike other solutions, the finished filter element with its already attached outer shell is not printed, as in the pad printing process; rather, the outer shell is printed before being attached to the filter element using a digital printing process. Based on this prior art, the invention aims to provide an alternative manufacturing process that retains the advantages of known solutions while offering further improvements. A method comprising all the features of claim 1 achieves this objective.

[0008] The inventive method for manufacturing a filter element for the treatment of fluids is characterized by the following characteristic manufacturing steps:

[0009] Providing a hollow cylindrical, preferably pleated filter mat,

[0010] Printing on at least one side of a flat surface using a digital printing process,

[0011] Assembling a flat piece of nonwoven material by cutting or separating it from the web,

[0012] Welding the longitudinal edges of the web section together, preferably by means of longitudinal seam welding using ultrasound, in order to obtain a closed, hollow cylindrical nonwoven sheath,

[0013] Positioning, preferably erecting, the hollow cylindrical nonwoven sheath, and

[0014] The filter mat is nested within the positioned fleece jacket in such a way that the filter element is created free from any thermal input, and that the print applied to the fleece jacket by the digital printing process faces a viewer of the filter element.

[0015] In this way, individual components for the final filter element can be manufactured and prepared at various production stations, even if these stations are geographically far apart. Provisioning, assembly, printing, welding, and assembly can thus be carried out at different production sites, allowing a larger batch of components to be prepared and made available at each production station. Subsequently, at another production station, a further process step can be performed to complete the filter element as a whole. This can be more advantageous than combining several production steps into a single process flow, which would result in production of the filter element as a whole being interrupted or delayed in the event of any disruptions in the process flow.

[0016] In a preferred embodiment of the method according to the invention, it is provided that a fluid-permeable support tube with a predefinable tolerance is inserted precisely into the free space inside the hollow cylindrical filter mat.

[0017] Preferably, it can also be provided that the filter mat, designed as a hollow cylinder and in particular erected, which can be slid onto the fluid-permeable support tube, has a larger outer diameter than the free inner diameter of the nonwoven jacket at least before being nested together, and that the filter mat is gathered at one of its end faces in such a way that a cone is formed which, in the manner of a sliding ramp, facilitates the insertion of the filter mat into the nonwoven jacket.

[0018] Furthermore, it can preferably be provided that the filter mat, which is designed as a hollow cylinder and can be slid onto the fluid-permeable support tube, has a smaller outer diameter than the free inner diameter of the nonwoven jacket, at least before being slid onto it, and that the outer diameter of the fluid-permeable support tube is chosen to be larger than the free inner diameter of the filter mat, such that when the support tube is inserted, the filter mat expands simultaneously and automatically and comes into contact with the inside of the nonwoven jacket with a predefinable pressing force.

[0019] There are various assembly options for producing the filter mat with the nonwoven jacket as a precursor to the filter element as the final product. Depending on various parameters, such as the size of the filter mat, the stiffness of the filter mat material, the number of filter pleats, the wall thickness of the chosen nonwoven jacket, the material of the nonwoven jacket, etc., a suitable combination product, "filter mat with nonwoven jacket," can be provided to the manufacturer promptly for further use. This ensures a reliable process and largely avoids potential production errors.

[0020] In accordance with the foregoing, it is further preferable that the filter mat and / or the support tube has a removable insertion aid on at least one free end face, in particular in the form of a conical insertion ramp, which facilitates sliding the nonwoven jacket onto the filter mat or the filter mat onto the support tube. Due to the removable insertion aid, it can be used as an assembly aid for a multitude of support tubes, each of which is to be inserted into the manufactured combination of filter mat and surrounding nonwoven jacket. Furthermore, a multitude of support tubes of different sizes can be securely positioned within the aforementioned filter mat / nonwoven jacket assembly using only one type of insertion aid.

[0021] In a further preferred embodiment of the method according to the invention, an inkjet printing process is used as the digital printing method, in particular for applying a label to the outer circumferential side of the nonwoven sheath. Compared to the otherwise conventional pad printing methods, this allows for the reliable application of a label with high contrast against the underlying nonwoven sheath.

[0022] In a further preferred embodiment of the method according to the invention, it is provided that, in the nested state, the components—the nonwoven jacket, the filter mat, and the support tube—are assembled, with their respective installation lengths selected such that two end caps, fixed opposite each other at their ends by means of an adhesive bed, accommodate all components flush between them. In this way, various types of end caps can be combined with the assembly of nonwoven jacket, filter mat, and support tube as a standardized intermediate product to form the final filter element. It is also possible, however, to space the nonwoven jacket at least on one side, preferably on both sides, from the adjacent end cap, thus enabling unimpeded flow of the pleated filter medium through the nonwoven jacket, with the possibility of flow behind the nonwoven jacket from the inside.

[0023] In a further preferred embodiment of the method according to the invention, the nonwoven sheath has a predefinable fluid permeability and is formed from individual fibers with at least a partial bicomponent structure. Preferably, at least some of the individual fibers consist of carbon or are coated with carbon black. Due to the bicomponent fiber structure, consisting of a core fiber and an outer sheath for the core fiber, the fiber material can be adapted to predefinable filtration tasks and their requirements over a wide range. Furthermore, thanks to the carbon or carbon black structure, unwanted electrostatic charging of the filter mat can be reduced, or a corresponding dissipation via the end caps, optionally including the associated filter housing, can be achieved. In this respect, the nonwoven can be formed with or without carbon or carbon black, respectively.Likewise, the bicomponent structure can be formed with or without carbon or soot.

[0024] In a further preferred method according to the invention, the nonwoven jacket rests linearly on the inner circumference of the filter pleats of the filter mat, while maintaining the predetermined pleat spacing of the filter mat. In this way, the pleat spacing can be fixed without becoming blocked during operation, as is previously the case, thus improving filtration performance.

[0025] The inventive method is explained in more detail below with reference to exemplary embodiments shown in the drawing. The drawings are presented in a general and not to scale representation.

[0026] Figures 1 to 13 show the different manufacturing steps, and

[0027] Figure 14 shows the manufactured filter element as a whole in a perspective external view with a labeled nonwoven jacket.

[0028] The filter element 8, partially manufactured in a preliminary stage according to Figure 1, has a filter mat 12 of conventional design encompassing a fluid chamber 10. As shown in Figure 1, the filter mat 12 can be designed as a hollow cylinder, but preferably it is designed as a pleated, i.e., unfolded, multi-layer filter mat, as shown in the following figures. The aforementioned fluid chamber 10 regularly also forms the so-called filtrate chamber of an element. The preferably pleated filter mat 12 is arranged as a hollow cylinder according to the illustration in Figure 1 and its two adjacent, free edges are connected to each other along a linear seam 14, for example, using an adhesive seam or a weldable connecting clip, as exemplified in DE 199 33 163 A1 of the patent holder.The corresponding seam or connection point 14 is shown in simplified form in Figure 1, and the mat construction is standard practice, so it will not be discussed in further detail here. In any case, the filter mat 12 is thus prepared for further manufacturing.

[0029] Figure 2 shows a section of a web segment 16 of a longer web 18 made of nonwoven material. The nonwoven material preferably consists of a fiber material with bicomponent fibers, which are bonded together, in particular thermally bonded, to form the nonwoven material. During the thermal bonding process, the individual bicomponent fibers are made of a suitable, readily meltable plastic material. Depending on the selected porosity or fluid permeability of the nonwoven material, it can be used as a pre-filter for the filter mat 12 as a main filter, either for particle filtration or for varnish removal from a fluid stream.

[0030] In the manufacturing process described above, the horizontal web 18 or a longer web section 16 obtained from it is printed on one side, which will later face the viewer, using a digital printing process. For this purpose, the web 18, preferably wound onto a roll, is unwound, or the web section 16 is used, in each case running horizontally, and passed under a suitable printing device during the printing process.

[0031] During pre-processing, a blank or web section 20 is cut from web 18 or web section 16, consisting of the nonwoven material, as shown in Figure 3. This is done, for example, by cutting or punching the web section 16, or by laser or waterjet cutting. Alternatively, and preferably, the web section 20 is obtained by laterally separating or cutting it from web 18 or web section 16.The final size of the web section 20, as shown in Figure 3, is chosen such that it can be placed around the hollow cylindrical filter mat 12 according to Figure 1 as an outer or nonwoven sheath 22, allowing for a flush finish at both free end faces and completely encompassing the outer circumference of the filter mat cylinder 12 with a definable edge overhang 24, as can be seen particularly in Figure 6. As indicated in Figure 4, alternatively, one side of the cut web section 20, which will later face the viewer, can be printed directly with a design, including a colored print, using a digital printing process, for example, an inkjet printer 25.In an alternative embodiment not shown, it may further be provided that the outer or nonwoven sheath 22 is shortened at least on one side in such a way that a predetermined distance to the respective adjacent end cap is created in the assembled state.

[0032] Subsequently, the two opposing longitudinal edges 26, 28 of the web section 20 are welded together, preferably by longitudinal seam welding using ultrasound, as shown in Figure 5, to obtain a closed hollow cylindrical nonwoven sheath 22. For this purpose, as shown in the partial view in Figure 6, the two longitudinal edges 26, 28 are placed one on top of the other, in particular the longitudinal edge 28 onto the longitudinal edge 26, so that a linear or seam-shaped overhang 24 is formed, wherein the overhang 24 then rests flat on a strip-shaped anvil 30 of the ultrasonic tool when viewed from below in the direction of Figure 5, and the weld seam connection as a whole is produced from above with the vertically movable, strip-shaped sonotrode 32.While Figure 5 shows the nonwoven sheath 22 in its nonwoven structure with the individual thermally bonded bicomponent fibers, this nonwoven structure is omitted in the other figures for the sake of simplicity. Once the weld seam 34 is completed, the nonwoven sheath 22 is fitted flush onto the pleated back of the filter mat 12 by being pulled onto it, with a predefinable pretension. This ensures that the individual filter pleats 62 of the pleated assembly are kept at a defined distance from one another and do not unintentionally press against each other during filter operation, thus preventing the filter material of the filter mat 12 from becoming clogged and regularly impairing the filtration performance.

[0033] The section of the composite of filter mat 12 and nonwoven jacket 22 shown in Figure 6 can be achieved by nesting the filter mat 12 inside the nonwoven jacket 22 in such a way that the print applied by printing, as exemplified in Figure 14, faces an observer in the vicinity. Instead of the welding process shown, the seam of the nonwoven jacket 22 can also be produced by gluing.

[0034] One way to position the filter mat 12 in the nonwoven jacket 22, which is closed by welding or gluing, is shown in Figure 7, in that the filter mat 12, which is folded into a hollow cylinder, has a larger outer diameter than the inner diameter of the nonwoven jacket 22, so that the filter mat 12 is gathered at one of its end faces, here the upper end 38, in such a way that a cone 40 is formed, which facilitates its insertion into the hollow cylindrical nonwoven jacket 22.The corresponding connection method between the nonwoven jacket 22 and the hollow cylindrical filter mat 12 is shown in Figure 10 from the upper free end face of the components in question, whereby, within the framework of this connection technique, a support tube 42 can also be inserted from the inside of the closed filter mat sheet 12, which, provided with individual fluid passages 44 (Figure 12), can support the mat sheet on its inner circumference and ensures the unimpeded flow of fluid from the outside into the interior of the element 8 with the fluid or filtrate space 10.

[0035] As the further assembly solution according to Figure 8 shows, a fluid-permeable support tube 42 with a predefinable tolerance is also inserted precisely into the free space inside the hollow cylindrical filter mat 12 in the form of the fluid space 10, which is again shown from the free end face.

[0036] In contrast, the solution according to Figure 9 relates to a method in which the filter mat 12, positioned as a hollow cylinder and which can be slid onto the fluid-permeable support tube 42, has a smaller outer diameter than the free inner diameter of the associated nonwoven jacket 22, wherein the outer diameter of the fluid-permeable support tube 42 is chosen to be larger than the free inner diameter of the filter mat 12 such that, when the support tube 42 is inserted, the filter mat 12 expands and comes into contact with the inside of the nonwoven jacket 22 with a predefinable contact force, which is shown on the far right when viewed in the direction of Figure 9, again from a free end face.The figures show the nonwoven jacket 22, the filter mat 12 and the support tube 42 assembled in an erected position, i.e. in a vertically oriented position, which allows for simplified assembly, whereby, particularly with regard to automated assembly, preferably using handling aids and devices, a different position of the components relative to each other can also be assumed, for example horizontally.

[0037] As can be seen from the sequence of Figures 11, 12, and 13, the support tube 42, with its individual circular fluid passages 44, has a shell-like insertion aid 48 on its free upper end face 46. This insertion aid has a knob 50 on its upper surface, which allows it to be handled, i.e., placed on or removed from the support tube 42. The insertion aid 48 also has a convex insertion ramp 52, which forms an annular wall area and facilitates the sliding of the filter mat 12 with its fleece cover 22, as shown in Figure 11, onto the support tube 42, as shown in Figure 12. This facilitates the assembly shown in Figure 13, consisting of the printed fleece cover 22, the filter mat 12, and the hollow cylindrical support tube 42 arranged internally.

[0038] As further shown in Figure 13, when nested together, the components—the nonwoven jacket 22, the filter mat 12, and the support tube 42—have their respective axial installation lengths selected such that two end caps 54 and 56, fixed opposite each other to this assembly by means of an adhesive bed (not shown), fit flush between them. The filter element 8, thus completed in Figure 14, is marked on the outside of the nonwoven jacket 22 using a laser printing process. The upper end cap 54, viewed in Figure 14, has a flange-like, upwardly extending circular cylindrical opening 58 with an inserted inner sealing ring in the form of an elastomeric O-ring 60, while the lower end cap 56 is closed at the bottom.

[0039] The construction of filter elements 8 in this manner is common, so it will not be discussed in further detail here. The nonwoven sheath 22 is smooth towards the surrounding area, i.e., without any protruding fiber material, so that the assembly in the form of the filter element 8 is easy to handle; in particular, replacing a used element with a new one is thus easily accomplished. The end caps 54, 56, which are preferably used, are made of sheet metal in this case. Alternatively, they can be made of plastic (polyamide) or die-cast zinc.

Claims

Patent claims 1. Method for manufacturing a hollow cylindrical filter element (8) for the treatment of fluids, in particular in the form of particle filtration, comprising at least the following manufacturing steps: Providing a hollow cylindrical, preferably pleated filter mat (12), Printing on a flat web (18) at least on one side using a digital printing process, Assembling a flat web section (20) of nonwoven material by cutting or separating it from or out of the web (18), Welding the longitudinal edges (26, 28) of the web section (20) together, preferably by means of longitudinal seam welding by ultrasound, in order to obtain a closed, hollow cylindrical nonwoven sheath (22), Positioning, preferably erecting, the hollow cylindrical nonwoven sheath (22), and The filter mat (12) is nested inside the positioned fleece jacket (22) in such a way that the filter element (8) is created free from any thermal input, and that the print (36) applied to the fleece jacket (22) by the digital printing process is facing a viewer of the filter element (8).

2. Method according to claim 1, characterized in that a fluid-permeable support tube (42) with a predefinable tolerance is inserted precisely into the free space inside the hollow cylindrical filter mat (12).

3. Method according to claim 1 or 2, characterized in that the filter mat (12), designed as a hollow cylinder and in particular erected, which can be slid onto the fluid-permeable support tube (42), has a larger outer diameter than the free inner diameter of the nonwoven jacket (22) at least before being nested together, and that the filter mat (12) is gathered at one of its end faces (38) in such a way that a cone (40) is formed which, in the manner of a sliding ramp, facilitates the insertion of the filter mat (12) into the nonwoven jacket (22).

4. Method according to one of the preceding claims, characterized in that the filter mat (12) formed as a hollow cylinder, which can be slid onto the fluid-permeable support tube (42), has a smaller outer diameter than the free inner diameter of the nonwoven jacket (22) at least before being slid on, and that the outer diameter of the fluid-permeable support tube (42) is chosen to be larger than the free inner diameter of the filter mat (12) such that, when the support tube (42) is inserted, the filter mat (12) expands simultaneously and comes into contact with the inside of the nonwoven jacket (22) with a predefinable contact force.

5. Method according to one of the preceding claims, characterized in that the filter mat and / or the support tube (42) has a removable insertion aid on at least one free end face (46), in particular in the form of a convex or conical insertion ramp (52), which facilitates the sliding of the fleece jacket (22) onto the filter mat (12) or the sliding of the filter mat (12) with the fleece jacket (22) onto the support tube (42).

6. Method according to one of the preceding claims, characterized in that an inkjet printing method is used as the digital printing method.

7. Method according to one of the preceding claims, characterized in that, in the nested state, the components in the form of the fleece jacket (22), the filter mat (12) and the support tube (42), whose respective installation length is selected such that two end caps (54, 56) fixed opposite each other on this assembly by means of an adhesive bed, receive all components flush between them.

8. Method according to one of the preceding claims, characterized in that the nonwoven sheath (22) has a predefinable fluid permeability and is formed from individual fibers with at least partial bicomponent structure.

9. A method according to any one of the preceding claims, characterized in that at least a portion of the individual fibers consist of carbon or are coated with carbon black.

10. A method according to any one of the preceding claims, characterized in that the nonwoven sheath (22) rests linearly on the inner circumference of the filter pleats (62) of the filter mat (12) and that the predetermined pleat spacing of the filter mat (12) is maintained.

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