EP1884582B1 - Sieves, in particular for consolidating nonwoven fabric by gas- or hydro-entanglement - Google Patents

Abstract

A sieve (10) for the production of a non-woven fleece which is integrated by gas or fluid action on the sieve upper surface (11). The sieve has numerous apertures (14) linking the upper surface with the lower surface (12). The upper surface also has a number of detents (16) that together form the desired pattern. The cross section of the apertures remains uniform from top to bottom or diverges. The detents are of uniform depth and are no deeper than one third of the sieve depth. The diverging holes subtend an angle of about 20 degrees with the centerline and are circular.

Description

The invention relates to a sieve, in particular a sieve, as it is used for the production of nonwovens by means of a gas or liquid jet solidification process.

In the production of nonwovens, such as are used in particular in the home, in general for sanitary purposes or for hygiene articles, nonwoven materials, such. Fibers, filaments, platelets, tapes, or the like are applied to a screen to form there a non-woven, continuous nonwoven web by a consolidation process. For felting or solidifying the nonwoven materials, for example, they are pressed against the sieve by a jet of water under high pressure, fluidized and entangled with one another. Instead of beam or comb-like water jets, beam or comb-like gas jets can be used, which lead to turbulence and entanglement of the fiber materials. Furthermore, other liquids, including non-aqueous liquids can be used instead of water.

By means of a corresponding surface design of the screens, patterns can be embossed in the resulting nonwovens, which stand out in relief from the general background of the nonwoven fabric.

For this purpose, wire mesh, stencils or wires are already known in which wire mesh made of copper are used, which have depressions or elevations of the sieve surface at embossing points. Due to the depressions or elevations, more or less fibers or other nonwoven materials may be piled or thinned at a particular location. Since wire cloths usually do not have the necessary rigidity to withstand the gas, fluid or water pressure, it is usually necessary to use a perforated steel drum to stabilize and support the wire cloth screen.

The use of woven screens has the disadvantage that fibers and other components of the nonwoven material can get stuck at the intersections of warp and weft, so that the forming nonwoven web is not destructive detached from the sieve, but more or less attached to this.

From the EP 0 776 391 B1 For example, there is already known an apparatus for producing a nonwoven and non-woven cloth by means of pressurized water jets wherein a cylindrical rotatable drum having a plurality of micro-orifices on its surface is used. These micro-openings can be distributed randomly or regularly on the surface of the drum. The microapertures are produced by means of the known technique of serigraphy with electrolytic deposition.

In order to produce nonwoven material webs or the like with embossed surfaces, like the EP 0 705 932 B1 shows, topographic sieves or support members used, which have a plurality of through holes or drainage holes. These drainage holes taper from the top to the back of the support member. The angle of the taper must not be too large or too small in this known sieve or support member and must be adjusted in terms of the thickness of the support member to obtain on the one hand a sufficient drainage effect and on the other side on top of the support member for To obtain the background structure of the nonwoven fabric desired structured surface.

To make reliefs in the nonwoven fabric, the surface of the support member or screen has recesses corresponding to the desired patterns.

Due to the running from the top to the back of the support member tapering the through holes, there is a risk that they can clog with fiber material, which can significantly affect the function of the support member and makes frequent servicing the same erfoderlich.

WO01 / 64984 A1 shows a production line for producing imaged nonwovens. The production line has an embossing station, with a pattern on a screen using pressurized water nozzles on a Nonwoven fabric can be imprinted. The sieve has a sieve body with an upper side and a rear side opposite to the upper side. Between the top and back a plurality of through holes runs. The top of the screen body is structured. Thus, the screen body on the upper side higher and lower lying areas, the contours of these areas follow a desired pattern. The cross section of the through holes remains constant between top and back.

WO03 / 060215 A1 shows a production line for producing imaged nonwovens. The production line has an embossing station. The embossing station imposes a pattern on a screen via high pressure water nozzles on the nonwoven fabric.

WO97 / 22434 A1 shows another production line for producing imaged nonwovens. The production line has a solidification station in which the nonwoven fabric is solidified on a screen via high-pressure water nozzles. The screen includes an upper surface, a reverse side opposite the upper side, and through holes that extend from the upper side to the rear side. Neither the top nor the back have a pattern for embossing on the nonwoven fabric. Further, the cross section of the through holes initially decreases in a funnel shape from the upper side to the rear side, in order then to remain constant.

Based on this, the object of the invention is to provide a further screen, in particular for the production of nonwovens, by means of a beam hardening method, which is improved in particular in its function and provides an increased embossing effect.

This object is achieved by the screen according to claim 1 and by the method according to claim 15, 22 and 23. Advantageous developments and refinements of the invention are described in the subclaims.

According to the invention, in the case of a sieve with a sieve body having an upper side for applying a nonwoven material to be consolidated, a reverse side thereto, a multiplicity of through openings extending from the upper side to the rear side, and with lower regions in the upper side, their contours correspond to a desired pattern run, provided that the cross section of the passage openings increases from the top to the back.

This makes it possible, on the one hand, for fibers, fiber fragments, filaments, filament fragments or other fibrous materials, which undesirably enter the passage openings, to not practically wed in them, as a result of which blockage of the passage openings of the sieve can be effectively prevented. On the other hand, the embossing effect can also be improved, since the flow resistance of the screen in the region of the depressions, in particular if the through openings taper conically towards the rear side, is reduced, so that the medium acting on the nonwoven material for solidification and entanglement also comes out of the The recesses adjacent areas can flow into the wells and thereby entrains fiber material, resulting in an improved relief formation.

Furthermore, the function of the sieve according to the invention is also improved by the fact that, especially when using liquids for solidifying the felt material, these liquids can be removed more easily in the region of the depressions, which facilitates subsequent drying of the nonwoven fabric produced on the sieve according to the invention.

In an advantageous embodiment of the invention it is provided that the deeper lying areas have a uniform depth which is not greater than about three quarters of the thickness of the screen body, preferably about equal to two thirds of the thickness of the screen body.

In order to make the relief formation, that is to say the contours of the desired relief more clearly or less clearly recognizable, it is expedient for the lower lying areas along their edges to be delimited by side walls which either extend substantially perpendicular to the sieve plane or at an angle of less than 45 ° inclined to the vertical plane of the sieve böschungsartig or form an undercut at an angle of less than 20 ° to the perpendicular to the plane of the sieve.

Particularly good results in the production of the nonwoven material are achieved if the opening ratio, ie the ratio of the area of all openings to the total area of the screen is in the range of 1% to 30%, in particular in the range of 5% to 20%, preferably 7% , Expediently, the opening ratio in the region of the lower regions is equal to or greater than outside of it.

In another embodiment of the invention, it is provided that the deeper areas of pattern forming, raised areas are interrupted, which protrude beyond the plane of the top of the screen body, wherein the opening ratio in the region of the raised areas at least smaller than the opening ratio in the lower lying Ranges, preferably equal to zero. With this, a pattern can be formed in the nonwoven fabric, which is pressed in relief in the background.

Depending on the type of medium used to solidify the nonwoven material on the screen, the cross section of the through openings may be circular or non-circular. In the latter case, oval, elliptical or quadrangular shapes are preferred, which may also be slit-shaped.

In the case of slot-shaped and non-circular passage openings whose cross-section defines a longitudinal direction, it is provided that the passage openings are arranged with their longitudinal directions parallel to one another, alternately parallel and perpendicular to one another, or in random orientation relative to one another, depending on the desired aperture ratio and / or required stability of the screen.

In order to ensure a good stability of the screen at a high opening ratio, it is expedient if the passage openings arranged so in that immediately adjacent to each of the through holes are six through holes equidistant from each other.

In another embodiment of the invention, it is provided that adjacent to each of the passage openings are three to ten through holes, which have different distances from each other. This makes it possible to achieve that the nonwoven fabric produced on the screen has a vividly structured background surface.

Such structuring can also be achieved if the passage openings are arranged randomly or pseudo-randomly with respect to each other.

In principle, it is possible that the sieve body of non-metallic materials, such. Plastic, ceramic, natural resin or lacquer materials suitable for forming stable sheets, composites or a combination thereof. However, it is advantageous if the strainer body consists of metal, preferably of a metal which can be deposited on an electrode in a galvanic bath, in particular of nickel, copper or aluminum or a mixture thereof.

• Bereitstellen eines Siebkörpers mit einer Oberseite zum Aufbringen eines zu verfestigenden Vliesmaterials und einer zur Oberseite entgegengesetzten Rückseite, wobei der Siebkörper eine Vielzahl von von der Oberseite zur Rückseite verlaufenden Durchgangsöffnungen aufweist, deren Querschnitt im wesentlichen von der Oberseite zur Rückseite hin gleich bleibt oder zunimmt, und
• Ausbilden von tiefer liegenden Bereichen in der Oberseite des Siebkörpers entsprechend einem gewünschten Muster, wobei vorzugsweise zum Ausbilden der tiefer liegenden Bereiche
• auf den Siebkörper eine Ätzmaske entsprechend einem gewünschten Muster aufgebracht wird, und
• anschließend der Siebkörper von der Oberseite her bis zu einer gewünschten Tiefe geätzt wird.

According to the invention, a sieve, which is used in particular for the production of nonwovens, can be produced by the following steps:

• Providing a screen body having an upper surface for applying a nonwoven material to be consolidated and a reverse side to the upper side, the screen body having a plurality of through openings extending from the upper side to the rear side, the cross section of which substantially remains or increases substantially from the upper side to the rear side, and
• Forming deeper areas in the top of the screen body according to a desired pattern, wherein preferably for forming the deeper areas
• on the screen body, an etching mask is applied according to a desired pattern, and
• then the screen body is etched from the top to a desired depth.

Instead of forming the recessed or deeper areas by means of etching, it is also possible that the top of the screen body is patterned eroded to a desired depth to form the deeper areas. However, the formation of the deeper areas can also be achieved by pattern-like ablation or by pattern-based ablation of the Siebkörpermaterials from the top of the screen body forth by means of laser radiation. It is expedient if laser radiation is used for removing the Siebkörpermaterials whose wavelength is selected according to the absorption properties of the Siebkörpermaterials.

Appropriately, the screen body is galvanically provided.

But it is also possible that is provided for providing the screen body, a flat plate or a hollow cylinder made of metal or non-metal by means of laser radiation with the plurality of extending from the top to the back through holes.

• Bereitstellen einer galvanischen Siebkörperfolie mit einer Oberseite und einer dazu entgegengesetzten Rückseite sowie einer Vielzahl von Durchgangsöffnungen,
• Aufbringen einer Galvanisierungsmaske entsprechend einem gewünschten Muster auf der Siebkörperfolie,
• galvanisches Abscheiden von Siebkörpermaterial außerhalb der tiefer liegenden Bereiche auf die Oberseite der Siebkörperfolie bis einer Dicke, die im Wesentlichen der späteren Tiefe der tiefer liegenden Bereiche entspricht,
• Entfernen der Galvanisierungsmaske und
• galvanisches Abscheiden von Siebkörpermaterial auf der resultierenden Siebkörperstruktur bis zu einer für den Siebkörper gewünschten Dicke unter Beibehaltung der Durchgangsöffnungen, die von der Oberseite des Siebkörpers zu dessen Rückseite mit zunehmendem Durchmesser verlaufen.

A method for producing a screen without material-removing techniques is characterized by the following steps:

• Providing a galvanic sieve body foil having an upper side and a rear side opposite thereto and a multiplicity of through-openings,
• Applying a galvanizing mask according to a desired pattern on the sieve body foil,
• electrodepositing screen body material outside the deeper areas onto the top side of the sieve body foil to a thickness substantially equal to the later depth of the lower lying areas,
• Remove the plating mask and
• electrodepositing screen body material on the resulting screen body structure to a desired thickness for the screen body while maintaining the passage openings which extend from the top of the screen body to its rear side with increasing diameter.

• Bereitstellen eines galvanischen Siebkörpers mit einer Oberseite und einer dazu entgegengesetzten Rückseite sowie einer Vielzahl von Durchgangsöffnungen, deren Durchmesser von der Oberseite zur Rückseite hin zunimmt,
• Aufbringen einer Galvanisierungsmaske entsprechend einem gewünschten Muster auf den Siebkörper,
• galvanisches Abscheiden von Siebkörpermaterial außerhalb der tiefer liegenden Bereiche auf die Oberseite des Siebkörpers bis einer Dicke, die im Wesentlichen der späteren Tiefe der tiefer liegenden Bereiche entspricht, und
• Entfernen der Galvanisierungsmaske.

Another method for producing a screen in which the pattern structures without Siebmaterial abtragende techniques are produced, comprises the following steps:

• Providing a galvanic screen body with a top and a opposite rear side and a plurality of through holes whose diameter increases from the top to the back,
• Applying a galvanization mask according to a desired pattern on the screen body,
• galvanically depositing screen body material outside the deeper areas on top of the screen body to a thickness substantially equal to the later depth of the lower areas, and
• Remove the plating mask.

In order to be able to produce a nonwoven fabric which has not only a relief-like embossed surface but also a background structure, it is advantageous if the upper side of the sieve body is raised before or after forming the lower-lying regions or before applying a plating mask for a galvanic production Etched areas using an etching mask according to the respective desired background structure of the nonwoven fabric to be produced.

• Figur 1 eine schematische Schnittdarstellung eines erfindungsgemäßen Siebes;
• Figur 2 eine schematische Draufsicht auf ein anderes erfindungsgemäßes Sieb;
• Figur 3 schematische Schnittdarstellungen weiterer Ausgestaltungen der Erfindung;
• Figur 4 schematische Draufsichten auf erfindungsgemäße Siebe zur Erläuterung der Verteilung von Durchgangsöffnungen;
• Figur 5(a) eine schematische Schnittdarstellung einer galvanischen Siebkörperfolie;
• Figur 5(b) eine schematische Schnittdarstellung eines Siebkörpers oder -rohlings;
• Figur 6(a) eine Darstellung entsprechend Figur 5(a);
• Figur 6 einen galvanischen Vorläufer eines erfindungsgemäßen Siebes;
• Figur 7(a) eine schematische Draufsicht auf ein Sieb gemäß einer weiteren Ausgestaltung der vorliegenden Erfindung; und
• Figur 7(b) einen Schnitt im Wesentlichen nach Linie VII in Figur 7(a).

The invention will be explained in more detail below, for example, with reference to the drawing. Show it:

• FIG. 1 a schematic sectional view of a sieve according to the invention;
• FIG. 2 a schematic plan view of another inventive sieve;
• FIG. 3 schematic sectional views of further embodiments of the invention;
• FIG. 4 schematic plan views of inventive sieves to explain the distribution of through holes;
• FIG. 5 (a) a schematic sectional view of a galvanic Siebkörperfolie;
• FIG. 5 (b) a schematic sectional view of a screen body or blank;
• FIG. 6 (a) a representation accordingly FIG. 5 (a) ;
• FIG. 6 a galvanic precursor of a sieve according to the invention;
• FIG. 7 (a) a schematic plan view of a sieve according to another embodiment of the present invention; and
• FIG. 7 (b) a section substantially to line VII in FIG. 7 (a) ,

In the various figures of the drawing corresponding elements are provided with the same reference numerals.

As in FIG. 1 As can be seen, a screen, in particular a screen, which is used for the production of nonwovens by means of a gas or liquid jet solidification process, a screen body 10, which has a top 11 and a reverse side 12 opposite thereto. The upper side 11 of the sieve body 10, ie the upper side of the sieve, is the side onto which the nonwoven material to be consolidated, ie fiber materials, filaments and other platelets or ribbon materials suitable for nonwoven fabric webs, are applied in the production of nonwovens. The opposite to the top 11 of the screen back 12 of the screen body 10 is substantially formed by a parallel to the top 11, preferably smooth surface. The sieve can be a flat sieve or else a cylindrical sieve.

With appropriate choice of material, it is also conceivable that form the wire band-shaped. For a belt-shaped screen, it is necessary to use a material of such a strength that on the one hand it is flexible enough to pass over deflecting rollers, but on the other hand is stable enough to withstand the pressure of a medium directed against the screen for the strengthening process , Level and cylindrical sieves can be preferably - as will be explained in more detail - produce galvanically.

In order to allow a derivation of the medium used, in particular of the water used during the solidification process, a plurality of passage openings 14 are provided in the screen body 10, whose cross-section remains the same from the upper side 11 to the rear side 12 or, as in FIG FIG. 1 shown widening conically.

In order to structure the forming nonwoven surface in relief in the production of nonwoven fabrics during the solidification of the nonwoven material by means of suitable liquid or gas jets, 10 recesses 15 are provided in the top 11 of the screen body whose bottoms 16 form deeper areas bounded by side walls 17 become.

How very good in FIG. 2 can be seen, the side walls 17 of the recesses 15 represent the contours of a desired pattern.

FIG. 2 shows a honeycomb-shaped arrangement of the through holes, and also shows that in the region of the wells, the through holes 14 on the input side have a larger diameter than the out-of-wells through holes 14, which is a consequence of the conical extension of the through holes to the back 12 out.

Depending on the desired relief sharpness, it is possible to form the side walls perpendicular to the plane of the screen or, in the case of cylindrical screens, perpendicular to the respective tangential plane, as shown in FIG FIG. 1 is shown. However, it is also conceivable that, as in FIG. 3 is shown, the side walls 17 form undercuts or slopes, as the left and right sides of Figure 3 shows. The angle α of the side wall with the vertical to the screen surface is in case of undercuts in the range of 0 ° to 20 °, while it can be up to 45 ° for embankments.

Depending on the medium used for the solidification process, and depending on the pressures used, the through holes may have different cross-sectional shapes and be distributed in different ways. FIG. 4 shows, for example, a random statistical arrangement in which adjacent to each of the round through-holes 14 are three to ten through holes 14, which have different distances from each other, while in the regular honeycomb-shaped arrangement according to FIG. 2 adjacent to each through hole 14 six Through holes 14 are located, each having the same distances from each other.

However, it is also possible to choose non-circular, oval, rectangular cross sections for the passage openings 14, which can then also be slot-shaped, as in FIG FIGS. 4 (b) and (c) is shown. Depending on the desired aperture ratio, ie the ratio of the total area of the openings to the total area of the screen, different arrangements can be provided. FIG. 4 (b) shows, for example, an array of passage openings 14 with slit-shaped cross-section, wherein the slots are all offset from each other in parallel. FIG. 4 (c) shows another arrangement in which to each through hole 14 eight adjacent through holes include, of which half are arranged parallel and the other half perpendicular thereto.

As a further design element for the desired relief-like pattern on the surface of the nonwoven fabrics, the depth t of the recesses 15 can be varied. Conveniently, the depth t of the recesses 15 should not be greater than about 3/4 of the thickness d of the screen body. In particular, the depth, as in the FIGS. 1 and 3 approximately equal to half the thickness of the screen body 10 is shown. However, depths t which are approximately 2/3 of the thickness d of the screen body 10 are preferred.

Since the passage openings 14 have a cross section which is constant or preferably widening from the top to the rear, the aperture ratio, ie the ratio of the area of all openings to the total area of the screen in the region of the recesses, is equal to or greater than the aperture ratio outside thereof. The opening ratio seen over the total screen is in the range of 1% to 30%, in particular in the range of 5% to 20% and preferably 7% and is corresponding to the fiber and nonwoven materials to be processed and taking into account the pressures with which the solidification medium flows against the fiber and nonwoven material on the surface of the screen, chosen.

In the production of nonwovens by means of the screen according to the invention, therefore, a nonwoven material is applied in a known manner to the surface 11 of the screen, in order then to be charged with a medium, which is the individual components of the nonwoven material pressed against each other, swirled and thus leads to a felting and to a solidification of the nonwoven material, which ultimately results in a web formation.

In the swirling of the nonwoven material by the solidification medium used, that is, for example, by gas, water, aqueous and non-aqueous liquids, fiber material is also transported into the recesses 15, thereby forming the relief pattern of the surface forming protruding. When using vertical or undercut side walls 17, the relief-like patterns receive sharp contours, while the use of more or less gently sloping slopes results in a softer relief formation.

If, as shown in the figures, through openings 14 are used, which widen conically towards the rear, this has a larger opening ratio in the region of the bottoms 16 of the recesses 15, which leads to a reduced flow resistance. As a result, the relief formation is further assisted, since the medium used for solidification can flow off faster in the region of the depressions, whereby the transport of nonwoven material into the recesses is assisted.

In particular, when using liquids, the increased in the lower areas, ie in the areas of the soil opening ratio improves the removal of the liquid, which simplifies a subsequent drying process.

A significant advantage of the constant or widening cross sections of the passage openings 14 is that in this way virtually clogging of the through openings is virtually eliminated, so that screens according to the invention can be used for a longer period maintenance-free for the production of nonwoven nonwoven fabrics.

In addition to electroplated sieves, whose production is described in more detail below, sieves can also be made of metal, plastic and composite materials, such as glass fiber reinforced plastics or resins or carbon fiber materials. It is also conceivable plastics and natural materials that are suitable for layering, with metal matrices or the like skeletal reinforce.

If sieves are to be produced from such materials, the plates or cylinders provided for this purpose can be provided with the passage openings 14 by means of laser radiation. By suitable adjustment of the laser beam focal point, through openings 14 with cross sections extending toward the rear side 12 can be achieved when the focus waist lies in the region of the upper side 11 so that the laser beam widens from the upper side 11 to the rear side 12. Depending on the depth of field of the laser, the conical widening of the passage opening 14 can be adjusted.

The following is based on the Figures 5 and 1 described the galvanic production of a sieve according to the invention by a first method according to the invention.

First, a screen body film 10 'having a desired thickness is prepared on a die patterned into conductive and nonconductive areas according to the desired screen in a galvanic bath. After the Siebkörperfilm 10 'has reached the desired thickness, it is withdrawn from the die to receive from the Siebkörperfilm 10' a screen body 10 by deposition of screen material in the galvanic bath. Here, as in FIG. 5 (b) is shown, at the top of the screen funnel-shaped inlet portions 24 of the through holes 14 form, which can each leave the size of the through holes 14 and / or after the desired aperture ratio of the screen or ground.

After the screen body 10 or screen blank is completed, the recesses 15 can then be performed by etching, spark erosion, laser ablation or by laser ablation. If a laser is used, it is expedient if its wavelength is matched to the absorption properties of the screen material used in each case.

If the depressions are to be produced by etching, an etching mask must first be applied to the sieve body. For this purpose, the sieve is first coated with an etching protective layer, which is then removed either by exposure and development or again by means of laser radiation in the area to be etched. After the appropriate removal of material then results from the in FIG. 5 shown Siebkörper 10 or Siebrohling, the in FIG. 1 illustrated sieve.

According to another method of the invention, after producing a sieve body film 10 ', as shown in FIG FIG. 6 (a) is shown, the Siebkörperfilm 10 'provided on the back and in the region of the recesses 15 to be formed with a Galvanisierungsschutzschicht to then deposit in the other areas further screen material in the galvanic bath, so that a Siebkörpervorläufer 10 "forms, already with the desired Depressions 15. Finally, after removal of the galvanization protective layers, the sieve body precursor 10 "in the galvanic bath is brought to the final sieve thickness d.

In the screens described thus far, the ratio of the total area of the recesses 15, ie the ratio of the total area of the lower areas to the total area of the non-recessed areas, is substantially less than 1, so that the resulting relief in the nonwoven fabric produced on the screen shows raised relief-like patterns ,

In another embodiment of a screen according to the invention, which is intended for relief-like depressed areas in the nonwoven fabric to be produced, are, as in the FIGS. 7 (a) and 7 (b) shown provided on the wire raised portions or areas 18, the side walls 17 correspond to the contours of the desired pattern, as shown in FIG. 7 a can be seen. The opening ratio of the screen in the region of the raised areas 18 is here preferably 0, ie that the raised areas are not provided with openings. Here, therefore, the ratio of the deeper areas to the raised areas is reversed as above.

In this sieve, again, the passage openings 14 are provided with a constant or a cross-section widening towards the back 12 of the sieve.

According to the invention, such a sieve is produced in such a way that firstly the sieve body 10 is formed to the desired thickness of the sieve in order subsequently to be provided with a galvanizing mask which leaves free only the regions on which sieve material for the formation of the raised regions 18 according to the pattern is left to be deposited in the galvanic bath.

When producing a nonwoven fabric on such a screen, fiber and nonwoven material is transported from the area of the raised areas into the lower areas, so that there forms a tapered, recessed relief in the finished nonwoven fabric.

The shape of the through holes also provides the same advantages as the other embodiments of the invention.

If it is desired that the nonwoven fabric produced on a wire of the present invention not only has the relief-like pattern embossed with the recesses or raised portions, but also provided with a background pattern extending over the entire background of the fabric, that is, the non-patterned portions In order to simulate, for example, a fabric, a knit or the like, it is possible to superficially etch the screen, that is to say the upper side of the screen body, using a corresponding etching mask. Depending on the manufacturing process used, the surface of the sieve body can be etched before or after the formation of the depressions. In the manufacture of a screen with raised areas, it is also possible to etch the top of the screen body before or after formation of the raised areas using a suitably patterned etch mask. If the structuring of the upper side of the screen body takes place after the formation of the recesses or raised areas, then the background pattern on the finished nonwoven also extends to the relief areas. Conversely, by forming the structure provided for the background pattern prior to the formation of the embossing elements, it can be achieved that the relief-like embossed areas do not have the same background structure, so that the relief emerges even more beautifully.

Claims (26)

1. Screen, in particular for manufacturing nonwoven fabrics by means of a gas jet or liquid jet bonding process, comprising a screen body (10) with an upper side (11) for applying a nonwoven material to be bonded and a rear side opposite from the upper side (11), the screen body (10) having a multiplicity of through-openings (14) running from the upper side to the rear side and also lower-lying regions (16) in the upper side (11) having contours that run in a way corresponding to a desired pattern, characterized in that the cross section of the through-openings (14) increases from the upper side (11) to the rear side (12).
2. Screen according to Claim 1, characterized in that the lower-lying regions (16) have a uniform depth (t), which is not greater than approximately three quarters of the thickness (d) of the screen body (10), preferably approximately equal to two thirds of the thickness (d) of the screen body (10).
3. Screen according to Claim 1 or 2, characterized in that the lower-lying regions (16) are bounded along their edges by side walls which either run substantially perpendicularly to the plane of the screen or are inclined in the manner of a slope at an angle of less than 45° to the perpendicular of the plane of the screen or form an undercut with an angle of less than 20° with respect to the perpendicular to the plane of the screen.
4. Screen according to Claim 1, 2 or 3, characterized in that the opening ratio, that is to say the ratio of the surface area of all the openings to the total surface area of the screen, lies in the range from 1% to 30%, in particular in the range from 5% to 20%, preferably at 7%.
5. Screen according to Claim 4, characterized in that the opening ratio in the region of the lower-lying regions is the same as or greater than outside them.
6. Screen according to Claim 4, characterized in that the lower-lying regions (16) are interrupted by pattern-forming, raised regions (18), which protrude beyond the plane of the upper side of the screen body, the opening ratio in the region of the raised regions being at least less than the opening ratio in the region of the lower-lying regions (16), preferably equal to zero.
7. Screen according to one of the preceding claims, characterized in that the cross section of the through-openings (14) is circular.
8. Screen according to one of Claims 1 to 6, characterized in that the cross section of the through-openings (14) is noncircular, in particular oval, elliptical or quadrangular.
9. Screen according to Claim 8, characterized in that the cross section of the through-openings (14) is slit-shaped.
10. Screen according to Claim 8 or 9, characterized in that the through-openings (14) are arranged with their longitudinal directions parallel to one another, alternately parallel and perpendicular to one another, or in randomized alignment to one another.
11. Screen according to one of the preceding claims, characterized in that directly adjacent each through-opening (14) there lie six through-openings (14) that are spaced at equal intervals from one another.
12. Screen according to one of Claims 1 to 10, characterized in that adjacent each of the round through-openings (14) there lie three to ten through-openings (14) that are spaced at different intervals from one another.
13. Screen according to one of Claims 1 to 10, characterized in that the through-openings (14) are arranged in a randomized or pseudo-randomized manner in relation to one another.
14. Screen according to one of the preceding claims, characterized in that the screen body (10) consists of metal, preferably of a metal that can be deposited on an electrode in an electrolytic bath, in particular of nickel, copper or aluminum or a mixture thereof.
15. Method for producing a screen, in particular according to one of the preceding claims, with the following steps:

    - providing a screen body (10) with an upper side (11) for applying a nonwoven material to be bonded and a rear side (12) opposite from the upper side (11), the screen body (10) having a multiplicity of through-openings (14) running from the upper side (11) to the rear side (12), the cross section of which substantially increases from the upper side (11) to the rear side (12), and

    - forming lower-lying regions (15) in the upper side (11) of the screen body (10) in a way corresponding to the desired pattern.
16. Method according to Claim 15, characterized in that the forming of the lower-lying regions (15) is performed by

    - applying an etching mask to the screen body (10) in a way corresponding to a desired pattern, and

    - subsequently etching the screen body (10) from the upper side (11) to a desired depth.
17. Method according to Claim 15, characterized in that the upper side of the screen body (10) is eroded to a desired depth according to a pattern to form the lower-lying regions (15).
18. Method according to Claim 15, characterized in that the formation of the lower-lying regions (15) is performed by removal according to a pattern or ablation according to a pattern of the screen body material from the upper side of the screen body by means of laser radiation.
19. Method according to Claim 18, characterized in that laser radiation of a wavelength corresponding to the absorption properties of the screen body material is chosen for the removal of the screen body material.
20. Method according to one of Claims 15 to 19, characterized in that the screen body is provided galvanically.
21. Method according to one of Claims 15 to 19, characterized in that a planar plate or a hollow cylinder of metal or non-metal is provided with a multiplicity of through-openings running from the upper side to the rear side by means of laser radiation to provide the screen body.
22. Method for producing a screen, in particular according to one of Claims 1 to 14, with the following steps:

    - providing a galvanic screen body film (10') with an upper side (11') and a rear side (12) opposite from it and also a multiplicity of through-openings (14),

    - applying an electroplating mask in a way corresponding to a desired pattern on the screen body film,

    - galvanically depositing screen body material outside the lower-lying regions (16) onto the upper side of the screen body film up to a thickness that corresponds substantially to the later thickness of the lower-lying regions (16),

    - removal of the electroplating mask and

    - galvanically depositing screen body material on the resulting screen body structure (10") to a thickness desired for the screen body (10) while retaining the through-openings (14) that run from the upper side (11) of the screen body (10) to its rear side (12) with increasing diameter.
23. Method for producing a screen, in particular according to Claim 6, with the following steps:

    - providing a galvanic screen body film (10) with an upper side and a rear side (12) opposite from it and also a multiplicity of through-openings (14), the diameter of which increases from the upper side to the rear side,

    - applying an electroplating mask in a way corresponding to a desired pattern on the screen body film (10),

    - galvanically depositing screen body material outside the lower-lying regions (16) onto the upper side of the screen body (10) up to a thickness that corresponds substantially to the later thickness of the lower-lying regions, and

    - removal of the electroplating mask.
24. Method according to one of Claims 15 to 23, characterized in that, after the forming of the lower-lying regions, the upper side (11) of the screen body (10) is etched using an etching mask in a way corresponding to a desired background structure of the nonwoven fabric to be manufactured.
25. Method according to one of Claims 15 to 21, characterized in that, before the forming of the lower-lying regions, the upper side (11) of the screen body (10) is etched using an etching mask in a way corresponding to a desired background structure of the nonwoven fabric to be manufactured.
26. Method according to Claim 23, characterized in that, before the application of an electroplating mask for galvanically depositing screen body material outside the lower-lying regions (16), the upper side (11) of the screen body (10) is etched using an etching mask in a way corresponding to a desired background structure of the nonwoven fabric to be manufactured.

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