Patent ID: 12226718

FIG.1represents diagrammatically a filter element, which is used for example in a hydraulic filter. The use in a hydraulic filter is particularly preferable. It is possible to use the filter element in other filters. It comprises a perforated casing or a cylindrical support tube12through which a plurality of flow openings13pass in the radial direction. In the circumferential direction, support tube12is surrounded by a multi-layer filter bellows15, which for illustration is represented inFIG.1partially in the manner of an exploded drawing. Filter bellows15can also be referred to as corrugated or pleated flat material. Filter bellows15is pleated in a star-shaped manner by pleats17running parallel to the longitudinal axis of support tube12, in such a way that radially outer pleat peaks18and radially inner pleat bases19alternately follow one another along its circumference.

Filter bellows15specifically comprises a three-layer filter material22with a fine-filter layer in the form of a fleece24, which in flow direction26, i.e. in the represented embodiment in the radial direction from outside inwards, is covered on the inflow side by a pre-filter fleece27and on the outflow side by a protective fleece28. The fleeces can be produced for example from a plastic or glass fibre material. The invention is not limited to such a filter material, but rather is also suitable for other filter materials which are provided for filtration, for example with more or fewer than three layers.

In flow direction26, filter material22is supported on the outflow side on a backing fabric30, which lies over its area against protective fleece28of filter material22and is also pleated star-shaped. Backing fabric30is in turn supported in flow direction26in the region of pleat bases19on support tube12. On the inflow side, i.e. radially outside, a protective fabric31is arranged which lies over its area against pre-filter fleece27of filter material22and is also pleated star-shaped. Backing fabric30and protective fabric31are each produced from a fabric layer according to the example of embodiment according to the invention, which is explained in greater detail with the aid ofFIG.2. It is possible for only backing fabric30or only protective fabric31to be produced from the fabric layer described in greater detail below.

InFIG.2, it is shown that the fabric layer according to the example of embodiment according to the invention comprises a first fabric strip10. First fabric strip10can also be referred to as the main fabric. The main fabric is characterised in that it enables the main function of the filter element, i.e. the flow through filter material22required for the filtration. First fabric strip10thus comprises a particularly large effective area. First fabric strip10extends in the longitudinal direction of the fabric layer according toFIG.2. In the assembled state, i.e. in the filter element, first fabric strip10extends in the circumferential direction of the filter element.

First fabric strip10merges into a second fabric strip11, which extends essentially parallel to first fabric strip10. It is possible for second fabric strip11to have an offset of at least one warp thread, in particular of a plurality of warp threads. Alternatively, a zigzag-shaped course of second fabric strip11is possible. Specifically, the weft threads of first fabric strip10merge into the weft threads of second fabric strip11. The two fabric strips10,11thus use the same weft threads and thus form a uniform or coherent fabric layer, which extends at least in the production state in one and the same plane. When the fabric layer is integrated into the flat material or filter bellows15, the latter forms the same star-shaped contour as filter material22. The flat material and therefore the fabric layer is corrugated or pleated.

As indicated inFIG.2by the shading, first fabric strip10has a first type of weave and second fabric strip11a second type of weave, which differs from the first type of weave. The effect of this is that different properties of the fabric layer are created in the regions of first fabric strip10and second fabric strip11. For example, the threads of the fabric layer in the region of second fabric strip11can be fixed more firmly by the second type of weave than the threads of the fabric layer in the region of first fabric strip10.

As can be seen inFIG.2, a different number of first and second fabric strips10,11can be provided. In the example according toFIG.2, three first fabric strips10and four second fabric strips11are provided, wherein first fabric strips10each extend between two fabric strips11.

In the example according toFIG.2, the entire fabric layer is cut in such a way that partial fabric layers arise, which each comprise a first fabric strip10and two second fabric strips11, which extend along the edges of the fabric layer. When in use, the edges of the partial fabric layers form the front-side edges of filter bellows15, as can be seen inFIG.1. Three partial fabric layers are formed in the example according toFIG.2. The width of the partial fabric layers can differ. The width depends on the distance of the two fabric strips11from one another. This has the advantage that the fabric layer can be customised for different filter bellow sizes.

It is also possible to produce a single fabric layer with a plurality of first fabric strips10, which are separated by second fabric strips11, similar to the entire fabric layer before the cutting, i.e. uncut fabric3. The filter element can thus comprises different flow regions with different properties, which are created by the suitable selection of the respective type of weave for first and second fabric strips10,11.

In the example of embodiment according toFIG.2, the main fabric, i.e. first fabric strip10, is produced in the type of weave “twill weave”. Second fabric strips11are each produced in the type of weave “linen weave”.

Other combinations of types of weave are possible. Thus, the first type of weave of first fabric strip10can specifically have an alternating twill weave or a herringbone twill weave. It is also possible for the first type of weave to comprise an atlas weave. The second type of weave can comprise a linen weave or plain weave, as inFIG.2, or a twill weave. These two types of weave are characterised in that they fix the warp threads securely in the fabric layer (fixing weave).

An example of a linen weave (second type of weave) is represented inFIG.3andFIG.4. In the case of the linen weave, weft threads32run alternately over and under a warp thread33. The cross-overs of weft threads32and warp threads33takes place according to a 1:1 pattern. Second fabric strips11are characterised by a high slip resistance. The threads, in particular the warp threads of second fabric strips11, are fixed by the linen weave securely in the fabric composite.

An example of a twill weave (first type of weave) is shown inFIG.5. In contrast with the linen weave according toFIG.4, weft threads32of the first fabric strip10run under two warp threads33, after which they run over two warp threads33, then again reach under two warp threads33and so on. The immediately adjacent weft thread displaces this rhythm by one to the side. Weft rises38thus extend over two adjacent warp threads, the same applying to weft falls39.

If two sections of the employed fabric layer with a twill weave in the region of first fabric strip10or in the regions of first fabric strips10come to lie directly against one another due to pleating or corrugation, thread or filament sections projecting in the downstream direction, in particular mutually facing and intersecting warp and weft rises, lie against one another. The total thickness of the sections of the fabric with a twill weave lying against one another due to pleating or corrugation is greater than the total thickness of the sections of the fabric with linen weave lying against one another due to pleating or corrugation. Micro-channels are formed between the sections of the fabric with a twill weave lying against one another due to pleating or corrugation, which micro-channels are not impaired by a slight relative movement of the two sections, but rather retain their formation in a stable manner.

As a result of the combination of the different types of weave, different properties of the fabric layer are thus created locally, which significantly reduce the re-work costs in the production of the filter elements, for example in the case of the linen weave at the edges of the fabric layer, because the edge threads are fixed in the fabric composite.

In addition, there is the fact that the arrangement of the two fabric strips11at the front-side edges of the fabric layer, as shown inFIG.2, leads to the regions with the two types of weave, i.e. second fabric strips11, dipping into end discs38,40and not therefore participating in the effective flow area of the filter element.

To sum up, the fabric layer is not woven consistently in one and the same type of weave, for example in a twill weave, as in the prior art. On the contrary, at the points at which the fabric layer is subsequently cut, i.e. to defined ribbon widths, a strip with a specific number of warp threads is woven in each case in another type of weave, in particular into a linen weave or plain weave. The main advantage consists in the fact that, as result of the linen weave at the edge, the edge thread is fixed in the fabric much better due to the more frequent switching, i.e. the more frequent offsetting of the thread, than in the case of a pure twill weave. The edge thread thus has a very much reduced tendency to jump out or be pulled out from the fabric.

Within the scope of the invention, the filter element with a filter bellows is claimed in addition to the fabric layer, into which filter bellows at least one fabric layer according to the example of embodiment according to the invention is integrated. Specifically, the filter bellows contains a plurality of material layers, which are pleated with one another in order to form a star-shaped pattern. One or two of these layers (upstream or downstream side) is made of a twill fabric, which has a favourable effect on the performance data and in particular the pressure loss of the filter element. Specifically, first fabric strip10is constituted in this manner. The intrinsically existing drawback of the fabric optimised with regard to the pressure loss consists in the fact that the edge threads in the twill weave are only slightly bound in the fabric, so that during the pleating process and subsequent processing steps, such as for example the separating of the pleated bellows, the edge threads are not held sufficiently well in the fabric composite, as a result of which additional re-work arises.

The twill fabric used for the main fabric or generally the first fabric strip with the first type of weave is supplemented by the fact that, at the edges, or where cuts are made to smaller ribbon widths after the weaving, a second type of weave is used, specifically the plain linen weave. The number of warp threads that are woven into the plain weave is ideally selected at maximum such that this part of the fabric disappears in the adhesive bed of the end discs of the filter element and does not therefore influence the performance data of the filter element.

In addition, further zones or strips with plain weave can also be introduced between the actual cutting lanes, in order for example to create flexible possibilities after weaving of being able to cut to different ribbon widths. Instead of plain weave at the edge, i.e. in the second fabric strip, other types of weave differing from the actual first type of weave of the fabric can also be considered at the edge, which hold the edge thread much better in the fabric than the twill weave. Here, the leno weave for example comes into question. The manual rework due to jumping-out of edge threads is not required, as a result of which a significant improvement in production for the manufacture of the filter element is to be noted.

LIST OF REFERENCE NUMBERS

1parent roll2roll for cutting3uncut fabric4cutting knife5first fabric strip11second fabric strip12support tube13flow openings14free15filter bellows16free17pleats18pleat peaks19pleat bases20free21free22filter material23free24fleece25free26flow direction27pre-filter fleece28protective fleece29free30backing fabric31protective fabric32weft threads33warp threads