WO2002055179A1 - Method for producing a foldable filter and products of said method - Google Patents

Abstract

Disclosed is a method for producing a filter (1') made of a foldable filter medium (2) and products of said method. Spacers ensuring parallel distancing of the folds (3) of a filter (1) by means of glued spacer threads or embossments (4c) having a uniform depth of embossment (y) are known per se. According to the invention, embossments (6, 7) having a variable depth of embossment (y) are made in a filter medium (2). The depth of embossment (y) is varied as a function of the distance (x) from a fold line (8, 9) in order to obtain a non-parallel profile of the spacer profile (67) between adjacent folds (10) and therefore a predeterminable form. Embodiments relate inter alia to the depth of embossment (y) which increases as the height (x') of the fold increases, convex and concave embossments (6, 7) for spacers (67) on both sides, a depth of embossment (y) which is proportional to a diameter (w) of the embossments (6, 7) and flat (6, 7) or longitudinally extended embossments for local or expanded spacing (67). The method is particularly suitable for the production of filter forms having low flow losses, high throughput rates, a high degree of filtration efficiency and good cake detachment..

Description

Manufacturing process for pleated filters and

process products

TECHNICAL AREA

The invention relates to the field of filter technology. It relates to a method for producing a filter and products of the method according to the preamble of the independent claims.

STATE OF THE ART

Filter media for separating solid or gaseous contaminants in air, gases, water, liquids or the like are produced for a wide range of filter products. Proven materials for filters are u. a. Fleeces, felts and fabrics. The nonwovens can be dry or spunbonded such as. B. cotton, wet nonwovens such. B. papers, one- or both-sided laminated nonwovens such. B. glass / polyester fleece or otherwise constructed nonwovens. For example, needle felts made of any synthetic fibers are used in the felts. Monofilament or multifilament fabrics can be made from natural or synthetic man-made fibers or from inorganic materials. Cotton fabrics, nylon fabrics or metal fabrics may be mentioned as examples.

Known techniques for filter production are the pleating or pleating of the filter medium, ie the production of accordion folds, or the cutting of special geometries. The pleating creates a large filter area with a large filter effect. Touching and short-circuiting of adjacent filter folds is prevented by spacers. Previous spacers are realized with threads soaked in glue or with hot glue ("hot melt"). Per- The problem with this is that only essentially parallel spacing of pleats is achieved in this way. It is also known to realize largely parallel distances between pleats by creating spacers or spacing elements with a uniform thickness along the fold height by embossing the filter medium on one side with a constant embossing depth. A parallel arrangement of pleats has the disadvantage of high flow resistance, high pressure losses and corresponding additional energy costs. In addition, the embossing is carried out regardless of the later position of the pleats or bending edges, so that embossing that is in the area of the bending edge causes undesired thickening.

During embossing, the filter material is deformed hot or cold, and possibly reheated. For example, filter papers can be embossed directly in the manufacturing process or in a post-treatment process using embossing rollers with a wide range of geometric patterns. The embossing can be a flat deformation or knot or a scoring, in particular an interrupted scoring or oblique scoring. In known embossing processes for filter media, only embossings with an embossing depth that is constant over the fold height are carried out, which leads to the high flow losses mentioned.

PRESENTATION OF THE INVENTION

It is an object of the invention to provide a simplified production process for plissable filters and filter media and filters produced in this way, which are suitable for realizing filter geometries with a high filtering effect and high utilization of the filter area. This object is solved by the features of the independent claims. The solution according to the invention consists in a method for producing a filter from a filter medium, the filter medium being produced in a web, provided with embossments and pleated along fold lines to form a filter, the embossments serving to keep the spacing between adjacent pleats in the pleated state, and furthermore the embossing is carried out with a variable embossing depth and the embossing depth is varied as a function of a distance from a fold line in such a way that a non-parallel profile of the spacer between the adjacent folds required for a predefinable fold shape results. By using embossing with variable embossing depth, the use of separate spacers, such as e.g. B. threads or hot glue, and at the same time an advantageous filter geometry can be realized. By varying the embossing depth as a function of the distance from a fold line, it is achieved on the one hand that embossed folds in the pleated state can be supported on possibly also embossed neighboring folds, so that filter short-circuits are avoided. On the other hand, the non-parallel spacer profile realizes any fold shape with a non-parallel alignment of pleated folds of the filter medium. Pleats that are not aligned in parallel are in turn advantageous for a high filter effect and a good utilization of the entire available filter area. Loss of space due to glued spacers is eliminated. Using the embossing process according to the invention, spacer profiles for pleatable filter media can be tailored so that filters with a high degree of separation, large throughputs and good cake detachment are created. In particular, cleaning by shaking can be provided because the filter mats are not fixed by adhesive in the pleated state, but remain elastically movable. In one embodiment, the embossing depth is changed by varying the lateral extent of the embossments. By varying the lateral expansion, different embossing depths can be achieved without overstressing the filter medium to be embossed. The filter medium can also be provided with convex embossments and concave embossments in order to produce spacers on both sides for several or all pleats in the pleated state. Convex and concave embossing can effectively prevent filter short-circuits on both sides of the pleats.

In another exemplary embodiment, the embossing depth is varied so that in the pleated state an increasing embossing depth is achieved with an increasing pleat height, and / or, if there are parallel fold lines, the embossing depths for such embossings or parts of embossings are kept the same Have clearances to one of the parallel fold lines. By choosing an increasing embossing depth with an increasing fold height, a spacing profile between the folds and thus a fold shape can be specified in such a way that free inflow and outflow surfaces of at least approximately the same size are created. As a result, the acceleration of the air flow within the filter media package is kept as small as possible, the flow and pressure losses are reduced and the overall energy costs are reduced.

In further exemplary embodiments, flat embossings are carried out for essentially punctiform or local spacing and / or elongated embossings for an extensive spacing. In the case of extensive embossing, the embossing depth can be varied by enlarging or reducing a size of the extensive embossing depending on the distance from one of the fold lines. Surface embossing can be done e.g. B. oval, elliptical or round with an in Dependence of the distance from one of the fold lines of variable diameter. In the case of elongated, in particular grooved, embossments, the embossing depth can be varied by increasing or reducing the width of the elongated embossments depending on the distance from a fold line. Furthermore, elongated embossings can be carried out in a straight line for a linear spacer or bent, angled or meandering for a flat spacer. In addition, longitudinal embossing can be carried out parallel to one of the fold lines with a constant embossing depth and / or not parallel to a fold line with a variable embossing depth depending on the distance from the fold line. Embossing should be avoided in the area of fold lines because they would limit the ability of the filter medium to be pleated. It is thus avoided that, as was customary in the past, the embossing pattern is arranged randomly relative to the fold lines or bending edges of the pleating.

In important embodiments, increasing and decreasing embossing depths are alternately carried out along a longitudinal direction of the path of the filter medium between the fold lines, and / or convex and concave embossments are alternately carried out along a width of the path of the filter medium, and / or there is an increase and a decrease of the embossing depths for convex and concave embossings executed in opposite directions. By means of alternately increasing and decreasing embossing depths in the longitudinal direction between the fold lines, immediately adjacent folds are provided with embossments for spacing at least on one side, thereby ensuring stable and reliable pleating. By alternately convex and concave embossings in the width direction, the same number of closely spaced and regularly arranged spacers are created on both sides of filter folds for particularly stable pleating. With convex and concave embossing with opposing increases and decreases Embossing depths are created on the inside and outside surfaces of folds, two opposing spacer profiles, which complement each other to create a definable fold shape and enable largely full-surface, bilateral support of adjacent folds.

In a second aspect, the invention also relates to a filter medium which is in the form of a web and has embossments and fold lines for pleating, the embossments serving to maintain a distance between adjacent pleats in the pleated state, the embossments furthermore having a variable embossing depth and the embossing depth varies as a function of a distance from a fold line so that in the pleated state a non-parallel profile of the spacer between the adjacent folds required for a predeterminable fold shape results. In particular, the embossments are designed as described in the exemplary embodiments. The filter medium can be a fleece, in particular a paper, a felt or a fabric.

In a third aspect, the invention relates to a filter which is produced according to the method and which in particular a particulate filter, a liquid filter, a dust filter or a filter for air pollution z. B. in vehicles, rooms or production facilities.

Further designs, advantages and applications of the invention result from the dependent claims and from the following description with reference to the figures.

BRIEF DESCRIPTION OF THE DRAWINGS

1 shows a pleated filter with an unembossed or embossed filter medium with constant depth (prior art); 2 shows a web of a filter medium with convex and concave embossings according to an exemplary embodiment of the invention; and

FIG. 3 shows the filter medium according to FIG. 2 in the pleated state.

In the figures, the same parts are provided with the same reference symbols.

WAYS OF CARRYING OUT THE INVENTION

Fig. 1 shows a conventional filter 1, which was made from a filter medium 2 by pleating in the form of accordion folds 3. If the harmonica folds 3 are placed close to one another, then two filter surfaces 4a, 4b can touch and short-circuit, i. H. become inactive for filtration. Previous distance maintenance has been achieved by spacing threads (not shown) impregnated with glue on one or better on both sides of the filter medium 2 before pleating, and the spacing threads of adjacent pleats 3 are fused together during pleating. Such spacer threads or hot glue provide a stable fold shape with folds 3 aligned in parallel. However, it is disadvantageous that only largely parallel pleat shapes can be formed by the spacer threads and the active, flowable filter area is reduced. Also known are single-sided embossments 4c (shown in dashed lines) of the filter medium 2 for mutually supporting the folds 3. Again, only a parallel spacer profile can be produced, in which the filter surface is flowed through unevenly and the air flow has to be deflected several times.

Fig. 2 shows a section of a web 5 of a filter medium 2, z. B. paper 2, with embossings 6, 7, which according to the invention have different embossing depths y. 5a denotes a longitudinal direction and 5b a width of the Web 5. Along the width 5b, fold lines 8, 9, namely lower fold lines 8 and upper fold lines 9, are provided for later pleating. Starting from a fold line 8, 9, z. B. the lower fold line 8, a fold height x can be defined in the longitudinal direction 5a, the maximum amount 89 is equal to a distance between the lower fold line 8 and an adjacent upper fold line 9. A fold as a whole is designated by 10 and its two fold halves by 10a, 10b. Symmetrical to a lower fold line 8 are arranged positive or convex or upstanding embossments 6, the size w and thus the embossing depth y increases with increasing distance x from the lower fold line 8 to the two adjacent upper fold lines 9. The embossments 6 are also symmetrical with respect to the upper fold lines 9, namely with increasing distance x from the upper fold lines 9 with decreasing size w and thus decreasing embossing depth y. As an alternative or in addition, negative or concave or downward embossing are also possible

7 produced, the size w and thus the embossing depth y with increasing distance x from the lower fold line

8 decreases up to the two adjacent upper fold lines 9 and increases symmetrically again from there. The convex and concave embossments 6, 7 are thus varied in opposite directions in their size w, lateral extent w or their diameter w and thus in their embossing depth y. As shown, they are advantageously arranged alternately in the direction of the width 5b.

3 shows the mode of action of the embossings 6, 7 with a variable embossing depth y- according to the invention. In the area of a lower fold line 8, two fold halves 10a, 10b are folded against one another or pleated, so that an upper side of the web 5 becomes the inside 11 of the fold 10 and a lower side of the web 5 becomes the outside 12 of the fold 10. Due to the pleating, the convex embossments 6 come into contact with one another on the inside of the fold 10 and can contact one another and thus the Support the fold halves 10a, 10b against each other. Due to the increasing or generally variable embossing depth y, a predeterminable spacer profile 67 and thus a predefinable fold shape can be realized. The concave embossments 7 located in the area of the lower fold line 8 fulfill the same function as the convex embossments 6, but with respect to the adjacent folds 10, ie they form a mutual support for the halves 10b, 10a of the adjacent folds 10. Note that for adjacent folds 10, the assignment of inside 11 and outside 12 to the original web 5 is reversed.

In the example shown, a V-shaped spacing profile 67 and a V-shaped fold shape are realized in that the embossing depth y of the convex embossments 6 increases in proportion to the distance x from the lower fold line 8 and the embossing depth y of the concave embossings 7 in proportion to the distance x from the lower fold line 8 decreases. A pleating angle α desired for a filter 1 'can be specified by choosing an appropriate proportionality factor. Due to the continuous arrangement of embossments 6, 7 in the longitudinal direction 5a, the alternating arrangement of convex embossments 6 and concave embossments 7 in the width direction 5b, and the mirror-symmetrical distribution of the embossing depths y for convex and concave embossments 6, 7 with respect to fold lines 8, 9 an extremely stable, versatile design and adaptable for optimal flow conditions spacer 67 for pleated filter media 2 is created.

2 and 3 can be varied in a variety of ways. Here are some examples: The embossments 6, 7 can instead of all for only a part of the folds 10 and / or only for parts, for. B. individual halves 10a, 10b, the folds 10 are performed. Convex embossments 6 can be on a first half 10a and / or a second half 10b Fold 10 and / or concave embossments 7 can be arranged on a second half 10b and / or a first half 10a of a fold 10. In particular, the convex embossments 6 can be carried out alone, ie without the concave embossments 1, or vice versa, so that only every second fold 10 has a support or spacer 67. For the remaining folds 10, a support can be dispensed with or another spacer can be used; convex embossments 6, or alternatively concave embossments 7, can also be arranged only on every second half 10a or 10b of a fold 10 and z. B. be embossed with a double embossing depth y to produce the desired spacer profile 67; Furthermore, convex embossments 6 on a first half 10a and concave embossments 7 on a second half 10b of the folds 10 can be produced in particular with a double embossing depth y in order to support the folds 10 on both sides with a smaller number of embossments 6, 7 by means of a predeterminable spacer profile To reach 67; Likewise, non-parallel fold lines 8, 9 and / or non-symmetrical distributions of embossing depths y can be produced to realize special filter geometries l ¹ .

The embossing depth y can be changed directly, ie without varying a lateral extension w of the embossings 6, 7. Another alternating pattern between convex and concave embossments 6, 7 can be carried out in the width direction 5b. The embossing molds 6, 7 can be designed as flat embossings 6, 7 for an essentially punctiform or local spacer 67 (as shown) and / or as elongated embossings for an extended spacer 67. The flat embossings 6, 7 can, for example, be oval, elliptical or round and in particular with a predeterminable embossing distance z between the embossings 6, 7 into the Filter medium 2 are impressed. A favorable choice of the embossing distance z is a value between 15 mm and 100 mm.

Longitudinal embossings can in turn be produced in a wide variety of shapes, for example curved and / or angled and / or in a change of shape. The embossing depth y is advantageously increased or decreased by increasing or decreasing a width of the elongated embossments 6, 7. Linear spacers 67 can be created with straight-line embossings. Longitudinal embossing should be carried out parallel to one of the fold lines 8, 9 with a constant embossing depth y and / or not parallel to a fold line 8, 9 with a variable embossing depth y depending on the distance x from the fold line 8, 9.

The fold shapes can be freely specified by choosing the profile of the spacers 67. Wrinkle shapes with non-parallel folds 10 are preferably produced. V-shaped pleat shapes are particularly favorable because they have the same inflow and outflow areas, cause low pressure losses, have a large usable filter area and are exposed to a uniform load and in particular contamination.

A pleat height x ¹ in the pleated state is advantageously chosen between 10 mm and 100 mm. For a V-shaped fold shape, a pleating angle α can be specified which is equal to a ratio of the distance x of an embossing 6, 7 from a folding line 8, 9 to the embossing depth y at this distance x.

Embossing methods known per se can be used to implement the invention. Typically, the filter material 2 is hot deformed or cold deformed and optionally reheated during embossing. The embossing can be done by nubbed rollers. In the case of a paper filter medium 2, the burling process can be integrated directly into the paper manufacturing process. With previous However, only knobs are used which have knobs, ie surfaces or grooves, for the embossments 6, 7 with a uniform depth. In order to carry out the invention, rollers with nubs are now used, in which the nub depth is varied in a manner according to the invention and in particular a required depth profile for the nubs on a nub roller is specified for a longitudinal direction 5a. In addition, the distance 89 between adjacent fold lines 8, 9 can be determined from the desired fold height x 'in the pleated state and the desired pleating angle. The fold lines 8, 9 and the knobs can then be arranged on the knob roller so that the knobs come to lie between the fold lines 8, 9.

In addition to the method described above for producing a filter 1 'from a filter medium 2, the invention also relates to a filter medium 2 which has been provided with embossings 6, 7 according to the method and a filter 1' which has been produced according to the method. The filter 1 'produced according to the invention can be a suspended matter filter 1', e.g. B. for the hospital area or for clean rooms, around a liquid filter 1 ', for. B. for the production of beverages, cosmetics or pharmaceuticals to a comfort filter 1 ', z. B. for room ventilation, air conditioning or vehicles, or a dedusting filter 1 '.

Claims

1. A method for producing a filter (1 ') from a filter medium (2), the filter medium (2) being produced in a web (5), provided with embossments (6, 7) and along fold lines (8, 9) is pleated into a filter (l ¹ ), the embossments (6, 7) serving as a spacer (67) between adjacent pleats (10) in the pleated state, characterized in that a) the embossments (6, 7) with a variable embossing depth (y) and b) the embossing depth (y) as a function of a distance (x) is varied by a fold line (8, 9) such that a non-parallel profile of the spacer (67) between the adjacent folds (10) required for a predefinable fold shape results. 2. The method according to claim 1, characterized in that a) the embossing depth (y) is varied in that a lateral extent (w) of the embossments (6, 7) is varied and / or b) the filter medium (2) with convex Embossings (6) and concave embossings (7) are provided in order to produce spacers (67) on both sides for several or all folds (10) in the pleated state. 3. The method according to any one of the preceding claims, characterized in that a) the embossing depth (y) is varied so that in the pleated state with an increasing fold height (x ¹ ) an increasing embossing depth (y) is achieved and / or b) parallel There are fold lines (8, 9) and the embossing depths (y) for such embossings (6, 7) or parts of embossings are kept constant, which have the same distances (x) to one of the parallel fold lines (8, 9). 4. The method according to any one of the preceding claims, characterized in that a) the embossing depth (y) starting from a fold line (8, 9), in the area of which embossments (6, 7) are inside in the pleated state, with an increasing distance ( x) the fold line (8, 9) is increasingly selected and / or b) the embossing depth (y) is based on a fold line (8, 9), in the area of which embossments (7, 6) are pleated on the outside, with a increasing distance (x) to the fold line (8, 9) is chosen decreasing and c) in particular that a V-shaped fold shape is specified and the embossing depth (y) is varied in proportion to the distance (x). 5. The method according to any one of the preceding claims, characterized in that a) planar embossments (6, 7) for an essentially punctiform spacer (67) and / or elongated embossments for an extended spacer (67) are carried out and b) in particular that no embossments (6, 7) are carried out in the area of fold lines (8, 9). 6. The method according to any one of the preceding claims, characterized in that a) with embossing (6, 7), the embossing depth (y) is varied by a size (w) the areal embossments (6, 7) are enlarged or reduced depending on the distance from one of the fold lines (8, 9) and / or b) areal embossments (6, 7) are oval, elliptical or round with a depending on the spacing (x) of one of the fold lines (8, 9) of variable diameter (w) and / or c) a stamping distance (z) between flat embossings (6, 7) between 15 mm and 100 mm is selected. 7. The method according to any one of the preceding claims, characterized in that a) in the case of elongated embossings, the embossing depth (y) is varied by increasing or decreasing a width of the elongated embossments depending on the distance (x) from a fold line (8, 9) and / or b) elongating embossments in a straight line for a linear spacer (67) or bent, angled or meandering for a flat spacer (67) and / or c) elongated embossings parallel to one of the fold lines (8, 9) with a constant embossing depth (y) and / or not parallel to a fold line (8, 9) with one depending on the distance (x) from the fold line (8, 9) variable embossing depth (y) are carried out. 8. The method according to any one of the preceding claims, characterized in that a) a pleat height (x ¹ ) in the pleated state is selected between 10 mm and 100 mm and / or b) a pleating angle (α) is specified for a V-shaped pleat shape , which is equal to a ratio of the distance (x) of an embossing (6, 7) from a fold line (8, 9) to the embossing depth (y) at this distance (x). 9. The method according to any one of the preceding claims, characterized in that a) along a longitudinal direction (5a) of the web (5) of the filter medium (2) between the fold lines (8, 9) alternately increasing and decreasing embossing depths (y) are carried out and / or b) alternately convex and concave embossings (6, 7) are carried out along a width (5b) of the web (5) of the filter medium (2) and / or c) an increase and a decrease in the embossing depths (y) for convex embossings (6) and concave embossings (7) are carried out in opposite directions. 10. filter medium (2), which has the shape of a web (5) and embossments (6, 7) and fold lines (8, 9) for pleating, the embossments (6, 7) to a spacer (67) between adjacent wrinkles (10) serve in the pleated state, characterized in that a) the embossments (6, 7) have a variable embossing depth (y) and b) the embossing depth (y) as a function of a distance (x) from a fold line (8, 9 ) varies in such a way that in the pleated state a non-parallel profile of the spacer (67) between the adjacent folds (10) required for a predefinable fold shape results. 11. Filter medium (2) according to claim 10, characterized in that a) the embossments (6, 7) are carried out according to the characterizing method steps according to one of claims 2-9 and / or b) the filter medium (2) is a nonwoven, in particular a paper (2), a felt or a fabric. 12. Filter (l ¹ ), produced by the method according to any one of claims 1-9. 13. Filter (1 ') according to claim 12, characterized in that the filter (1') a particulate filter (1 "), a liquid filter (1 '), a dust filter (l ¹ ) or a filter (!') For air pollution control is.