Filter element

Abstract

The invention relates to a filter element, at least consisting of: - a pleated, hollow cylindrical filter mat (12); - a support tube (12) provided with fluid passages (34); - a non-woven casing (14) that surrounds the filter mat (12) on the outer circumference; and - two end caps between which the filter mat (12), the support tube (34) and the non-woven casing (14) are arranged; characterised in that the non-woven casing (14) is constructed from individual two-component fibres that have a core and a casing composed of plastic materials and are thermally connected to one another in the form of continuous filaments.

Description

[0001] Filter element

[0002] The invention relates to a filter element, at least consisting of a pleated, hollow cylindrical filter mat, a support tube provided with fluid passages,

[0003] - a fleece jacket that surrounds the filter mat on its outer circumference, and - two end caps between which the filter mat, the support tube and the

[0004] are arranged in a non-woven sheath.

[0005] EP 1 015 095 B1 discloses 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 connected to each other 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 insertion into the cylindrical filter jacket.

[0006] 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 jacket and the support tube and is thus insensitive to alternating pressure stresses during filter operation.

[0007] 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.

[0008] - 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

[0009] - 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. Unlike other solutions, the finished filter element with the already bonded outer shell is not printed, as in pad printing; rather, the outer shell is printed before being bonded to the filter element using a digital printing process. Furthermore, the aforementioned prior art relates to a filter element manufactured according to this process.

[0010] Based on this prior art, the invention aims to create a filter element that, while retaining the advantages of known solutions, offers further improvements. A filter element with the features of claim 1 as a whole achieves this objective.

[0011] According to the characterizing part of claim 1, the nonwoven sheath is constructed from individual bicomponent fibers, each having a core and a sheath made of plastic materials, and thermally bonded together in the form of continuous filaments. This allows the nonwoven sheath to be provided with high functionality and, similar to a filter mat, to remove particle contamination and / or varnish from a fluid stream, thus forming a pre-filter to the main filter with the filter mat while maintaining the same filter functionality. In particular, the bicomponent fibers are formed from continuous filaments that, when thermally bonded together, create a spunbond nonwoven with a fibrous structure, which can be used in a wide variety of applications.

[0012] Preferably, the core of a bicomponent fiber consists of polyester and the sheath of polyamide. It has also proven particularly advantageous if the polyester content of a bicomponent fiber is in the range of 50 to 75% and the polyamide content in the range of 25 to 50%. The fiber cross-sections used can be oval, star-shaped, trilobal, rhomboid, rectangular, especially square, and many others; however, a round fiber cross-sectional shape is preferred.

[0013] The nonwoven fabric of the cover is preferably open-pored and can be provided with organic particles, such as activated carbon, which typically results in a black color for the cover. The carbon content is expressed as a percentage based on the basis weight. Thus, the carbon content is preferably greater than 5% based on the basis weight of the nonwoven, particularly in the form of amorphous carbon. It is further preferred that the polyester core is made of PET and the polyamide cover of PA-6 plastic. Other material combinations are possible. Thanks to the carbon used, the filter element is electrically conductive. In particular, this also leads to a reduction in electrostatic fluid charging in conjunction with the filter mat component.

[0014] In a further preferred embodiment of the filter element according to the invention, the fiber diameter of a bicomponent fiber is between 15 and 300 mm / m, preferably 26 mm / m, the diameter of the polyester core is between 18 and 25 mm / m, preferably 22 mm / m, and the wall thickness of the polyamide sheath is between 1.5 and 3.25 mm / m, preferably 2 mm / m. This results in elastic behavior of up to approximately 30% due to the special material structure of the nonwoven sheath.

[0015] In a further preferred embodiment of the filter element according to the invention, the nonwoven jacket consists of a flat blank whose open-pored fiber structure forms a hollow cylinder. Preferably, the free, raised longitudinal edges of the blank are permanently welded together, either butted or with a predetermined overlap, to form the hollow cylindrical nonwoven jacket, particularly using an ultrasonic welding process, whereby the weld seam remains open-pored. Because the aforementioned special joining method using ultrasonic welding leaves the material of the nonwoven jacket largely unaffected, especially since the weld seam remains open-pored, the nonwoven jacket, acting as a pre-filter in combination with the filter mat as the main filter, has a significantly increased dirt-holding capacity.

[0016] Preferably, the nonwoven sheath, formed from the flat cut, is further provided for, having a basis weight between 10 and 500g / m². 2 exhibits that the material thickness of the nonwoven sheath is between 0.05 and 1.5 mm, preferably 0.5 mm, and that the air permeability of the nonwoven sheath is between 2000 and 10000 l / m 2 / s is located, preferably essentially 4200 l / m 2The flow rate is / s. This means that the nonwoven sheath has a thickness that is chosen to be translucent enough that, viewed from the surroundings, part of the filter mat's surface is visible. This allows, particularly from the outside, at least partial observation of the correct spacing of the individual filter pleats beneath the nonwoven sheath. Furthermore, the special fiber structure ensures homogeneous flow through the element, and the aforementioned elastic behavior facilitates reverse flow through the element when necessary.

[0017] The invention also relates to a nonwoven sheath, in particular provided for a filter element as specified above, wherein the nonwoven sheath consists of bicomponent fibers with a basis weight of the nonwoven sheath between 10 and 500 g / m². 2, wherein the material thickness of the nonwoven sheath is 0.05 to 1.5 mm, and wherein the air permeability of the nonwoven sheath is 2000 to 10000 l / m 2 The value is / s. In particular, the bicomponent fibers can be thermally bonded together in the range of approximately 200 to 300°C, so that the nonwoven sheath structure is created in a particularly gentle way without damaging the plastic fiber material.

[0018] The filter element according to the invention will now be explained in more detail with reference to an exemplary embodiment shown in the drawing. The drawing shows, in a general and not to scale, the following:

[0019] Figure 1 shows a perspective top view of individual components of the filter element, such as the fleece jacket, filter mat and perforated support tube in the assembled state;

[0020] Figure 2 shows the joining of two longitudinal edges of a blank using an ultrasonic welding process to produce the nonwoven sheath for a component assembly according to Figure 1; and

[0021] Figure 3 shows the finished filter element, starting from the pre-product according to Figure 1, with two end caps attached opposite each other and with the lettering applied.

[0022] The filter element shown in Figure 1, partially completed, features a filter mat 12 of conventional design encompassing a fluid chamber 10. This filter mat 12 is designed as a pleated, i.e., unfolded, multi-layer filter mat, shaped like a hollow cylinder. The aforementioned fluid chamber 10 also regularly forms the so-called filtrate chamber of the element shown in Figure 1. The main function of the filter mat 12 is the filtration of fluids, i.e., the reduction of fluid contamination, particularly in the form of particulate contamination. Accordingly, the filter mat 12, or the associated filter element, serves to protect hydraulic systems in both mobile and stationary applications. The filter mat 12, with its individual filter layers, is pleated in a star shape with a variable pleat height for the individual filter pleats, preferably in the range of 5 to 50 mm.The filter mat 12 mentioned above can accommodate a wide variety of plastic media, such as polyester, polyamide, polypropylene, and many others. Furthermore, the filter mat 12 can be reinforced on its inner and / or outer circumference with a wire mesh (not shown). In addition to the aforementioned plastic media, fiberglass media and cellulose material can also be used. If the filter mat 12 contains carbon-based media, static charging of the fluid is effectively prevented.The filter mat 12 is regularly formed from a multi-layered, flat blank and then, in pleated form, during assembly into a hollow cylinder, the two adjacent, free edges of the mat are joined together along a linear seam or connection point (not shown), for example, using an adhesive seam or a weldable connecting clip, as exemplified in DE 199 33 163 A1 of the patent holder. This seam or connection construction, like the mat construction itself, is common practice, so it will not be discussed in further detail here.

[0023] As further shown in Figure 1, the hollow cylindrical pleated filter mat 12 is precisely surrounded by a nonwoven jacket 14, the axial extent of which is selected such that it is flush with the free end faces of the filter mat 12 at the top and bottom. The nonwoven jacket 14 can also be designed to allow flow behind it if it is manufactured with variable offsets on one or both sides. This means that the nonwoven jacket 14 can have a predefinable distance to an adjacent end cap or termination on at least one side, leaving the filter mat 12 exposed. The nonwoven jacket 14 is obtained from a flat cut 16 of nonwoven material, which is folded up along its edges as shown in Figure 2 and closed along its two longitudinal edges or sides 18, 20 to form a cylindrical hollow body, creating the circumferential nonwoven jacket 14.The two longitudinal sides 18, 20 can abut each other end-to-end to form a longitudinal seam 22, or the longitudinal sides 18, 20 can be overlapped after welding to form the respective longitudinal seam 22. The longitudinal seam welding described above is performed using ultrasound as shown in Figure 2 to maintain the closed, hollow cylindrical fleece sheath 14. If the two longitudinal edges or longitudinal sides 18, 20 are partially overlapped, a projection 24 of a predefinable width is preferably created. This projection, viewed from below in the direction of Figure 2, rests flat on a strip-shaped anvil 26 of the ultrasonic tool and is welded from above by the vertically movable strip-shaped sonotrode 28, so that the weld joint in the form of the longitudinal seam 22 is produced as a whole.Instead of the aforementioned ultrasonic welding, the longitudinal sides 18 and 20 can also be firmly joined together using a conventional adhesive bonding method or the like. In the present case, the right longitudinal side 20 is placed onto the longitudinal side 18, forming the overhang 24.

[0024] While Figure 2 shows a simplified representation of the nonwoven sheath 14 in its nonwoven structure with the individual thermally bonded bicomponent fibers 30, this nonwoven structure is omitted in Figures 1 and 3 for the sake of clarity. Once the weld seam 22 is completed, the nonwoven sheath 22 is fitted flush onto the pleated back of the filter mat 12 with a predefinable pretension. This ensures that the individual filter pleats of the pleated assembly are kept at a defined distance from one another and cannot unintentionally adhere to each other during filter operation, thus preventing blockage of the filter material of the filter mat 12 and regularly impairing filtration performance.One way to fit the filter mat 12 into the nonwoven jacket 22, which is closed by welding or gluing, is to ensure that the filter mat 12, folded into a hollow cylinder, has a larger outer diameter than the inner diameter of the nonwoven jacket 22. This allows the flexible filter mat 12 to be gathered at one of its end faces, in this case the upper end, forming a cone (not shown) that facilitates insertion into the hollow cylindrical nonwoven jacket 22. The specific joining method for this purpose between a filter jacket and a hollow cylindrical filter mat is illustrated by way of example in EP 1 015 095 B1 and is thus sufficiently disclosed to a person skilled in the art in filtration technology. Other joining techniques are possible, for example, by precisely fitting the filter mat 12 into the nonwoven jacket 14.In any case, the composite of filter mat 12 and fleece jacket 14 is supported on the inner circumference in a known and proven manner by a support tube 32, which in the present case has circular openings as fluid passages 34.

[0025] Before the flat blank 16 with raised longitudinal sides 18, 20 is completed to form the nonwoven sheath 14 by welding, as shown in Figure 2, the blank 16 can be printed on one side using a digital printing process, such as an inkjet process, with a print, in particular in the form of lettering, which, as indicated in Figure 3, faces a viewer. The individual bicoment fibers 30 of the nonwoven sheath 14 consist of extruded continuous fibers, which are wound onto yarn spools during production. For further manufacturing towards a finished nonwoven fabric, the continuous fibers are then unwound from the yarn spools and, after passing through calender rollers, are bonded together or glued to form the finished nonwoven fabric in an oven at approximately 200 to 300°C.The production of yarn and nonwoven fabric in this way is common practice, so it will not be discussed in further detail here. The respective bicomponent fiber 30, with a polyester core and a polyamide sheath, can be further "finished," particularly along its surface, for example, by hydrophobic or hydrophilic modification.

[0026] Preferably, the polyester content of a bicomponent fiber designated 30 is between 50 and 75%, and the polyamide content is between 25 and 50%, wherein the polyester core is preferably equipped with carbon, i.e., preferably has a carbon content of greater than 5% based on the basis weight of the nonwoven, particularly in the form of amorphous carbon. Further technical specifications have already been mentioned in detail in the introductory section of the description, so to avoid repetition, they will not be discussed further here.

[0027] In addition to the previously mentioned black color, the element surface with the nonwoven sheath 14 can also be designed in white, green, and other colors, depending on the specific color particles applied or incorporated. Besides color, the yarn material can also be further enhanced by being flame-resistant, heat-resistant, and stable against ambient UV radiation. For good environmental compatibility, the filter element as a whole is designed to be recyclable or incinerated. Preferably, all components of the filter element according to Figure 3 are made of recyclable plastic materials, including the two end caps 36 and 38 with the O-ring 40 and the support tube 32. To ensure this environmental compatibility, the antimony content of the continuous fiber must be extremely low.The individual bicomponent fibers 30 are inherently stable and have a yarn fineness of preferably 7 to 15 dtex. Preferably, the respective lettering has an inclination (not shown) to the longitudinal axis of the element. As can be further seen from Figures 1 and 3, in the nested state, i.e., in the composite state of the components in the form of the nonwoven sheath 14, the filter mat 12, and the support tube 32, their respective axial installation lengths are selected such that the two end caps 36, 38, which are fixed opposite each other at the ends of this composite by means of an adhesive bed (not shown), accommodate all components flush between them. Alternatively, in an embodiment not shown, it can be provided that the nonwoven sheath, preferably on both sides, is set off or shortened in relation to the respective adjacent end cap 36, 38, so that a free-flowing area is created with the possibility of backflow.The filter element, as shown in Figure 3, is completed in this respect and is marked on the outside of the nonwoven jacket 14 by means of a laser printing process. The upper end cap 36, viewed in the direction of Figure 3, has a flange-like, upwardly extending circular cylindrical opening 42 with the inserted inner sealing ring in the form of the elastomeric O-ring 40. The other lower end cap 38, in contrast, is closed at the bottom.

[0028] The construction of filter elements according to Figure 3 is generally standard, so it will not be discussed in further detail here. The nonwoven sheath 14 is smooth towards the surrounding area, i.e., without protruding fiber material, and is made with the bicomponent fibers 30, so that the assembly in the form of the filter element is easy to handle; in particular, replacing a used element with a new one is easily done manually. The end caps 36, 38, which are preferably used, are made of polyamide plastic in this case, as is the perforated support tube 32.

Claims

Patent claims 1. Filter element, consisting at least of - a pleated, hollow cylindrical filter mat (12), - a support tube (32) provided with fluid passages (34), - a fleece jacket (14) that surrounds the filter mat (12) on its outer circumference, and - two end caps (36, 38) between which the filter mat (12), the support tube (32) and the nonwoven jacket (14) are arranged, characterized in that the nonwoven jacket (14) is made up of individual bicomponent fibers (30) which have a core and a jacket made of plastic materials and which are thermally bonded together in the form of continuous filaments.

2. Filter element according to claim 1, characterized in that the core of a bicomponent fiber (30) consists of polyester and the sheath of polyamide.

3. Filter element according to claim 1 or 2, characterized in that the polyester content of a bicomponent fiber (30) is 50 to 75% and the polyamide content is 25 to 50%.

4. Filter element according to one of the preceding claims, characterized in that the polyester core has a carbon content, in particular in the form of amorphous carbon, of greater than 5% based on the basis weight of the nonwoven sheath (14).

5. Filter element according to one of the preceding claims, characterized in that the fiber diameter of a bicomponent fiber (30) is between 15 and 300 / jm, preferably 26 m, and that the diameter of the polyester core is between 18 and 25 / jm, preferably 22 / jm, and that the wall thickness of the polyamide sheath is between 1.5 and 3.25 / jm, preferably 2 / jm.

6. Filter element according to one of the preceding claims, characterized in that the nonwoven sheath (14) consists of a flat blank (16) which, when raised, forms a hollow cylinder with its open-pored fiber structure.

7. Filter element according to one of the preceding claims, characterized in that the free, raised longitudinal edges (18, 20) of the blank (16) are permanently welded together by butting or overlapping with a predetermined overhang (24) to form the hollow cylindrical nonwoven sheath (14), in particular by using an ultrasonic welding process, and that the weld seam (22) formed in each case remains open-pored.

8. Filter element according to one of the preceding claims, characterized in that the nonwoven sheath (14), formed from the flat blank (16), has a basis weight between 10 and 500 g / m2.

9. Filter element according to one of the preceding claims, characterized in that the material thickness of the nonwoven jacket (14) is between 0.05 and 1.5 mm, preferably 0.5 mm.

10. Filter element according to one of the preceding claims, characterized in that the air permeability of the nonwoven jacket (14) is between 2000 and 10000 l / m2 / s, preferably substantially 4200 l / m2 / s. 1 1. Filter element according to one of the preceding claims, characterized in that the thickness of the nonwoven sheath (14) is such that The filter mat (12) is chosen to be translucent, such that part of its surface is visible when viewed from the surroundings.

12. Nonwoven sheath, in particular provided for a filter element according to one of the preceding claims, characterized in that the nonwoven sheath (14) consists of bicomponent fibers (30) with a basis weight of the nonwoven sheath (14) between 10 and 500 g / m² 2, that the material thickness of the nonwoven sheath (14) is 0.05 to 1.5 mm, and that the air permeability of the nonwoven sheath (14) is 2000 to 10000 l / m 2 / s is.

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