EP2199459A1 - Sheet composition system for a machine for producing a multiple layer sheet of fibrous material - Google Patents

Abstract

The sheet composition system (1) has a multilayered headbox (2) with a headbox nozzle (6). A separating wedge (7) has a separating wedge protrusion (U.7). The separating wedge has two separating wedge areas, particularly an upstream separating wedge starting area (7.1) and a downstream separating wedge ending area (7.2). Each has separating wedge angles (alpha,beta).

Description

The invention relates to a sheet forming system for a machine for producing a multilayer fibrous web, in particular a multilayer paper or board web, from at least two pulp suspensions, comprising a multilayer headbox with a headbox nozzle, the at least two extending across the width of the machine by at least one separating wedge from each other separate, during the operation of the multilayer headbox each have a pulp suspension as a pulp suspension flow leading and converging nozzle chambers having upstream each one feeder and downstream each having a width extending across the outlet gap with a gap width, the two outer nozzle chambers on the outside each have an outer wall and wherein the separating wedge contacts two during operation of the multi-layer headbox from the respectively adjacent pulp suspension stream e has Trennkeiloberflächen, and one of the multi-layer headbox immediately downstream Spaltformer with two rotating endless screens, of which the first sieve over a peripheral region of a forming roller and of which the second sieve over a peripheral region of a breast roll passes and then in the region of the forming roll on the first sieve with the formation of a wedge-shaped material inlet gap, which immediately accommodates the pulp suspension streams emerging with a free jet length from the headbox of the multi-layer headbox as a common pulp suspension jet, and the two wires with the at least two pulp suspensions between them then at least partially form a twin-wire zone.

The pulp suspensions will usually be suspensions of different pulps, but they may also be suspensions of the same pulps but with different physical properties. A physical property may be, for example, different pressures for setting different flow velocities in the respective pulp suspension stream.

Such a multilayer headbox for a machine for producing a multilayer fibrous web, in particular a multilayer paper or board web, from at least two fibrous stock suspensions is known, for example, from the German Offenlegungsschrift DE 195 38 149 A1 known. In the multilayer headbox designed as a three-layer headbox, the suspension layers are kept separate by rigid partitions. At the downstream end adjacent partitions are different deformable perpendicular to the jet plane, so that both a good beam guidance is possible and the optimal connection of the suspension layers after exiting the head box.

Furthermore, such a multi-layer casserole, for example, from the German patent DE 43 23 050 C1 known. The disclosed multi-layer casserole has, as in the FIG. 3 of this German patent specification, for the separation of two adjacent pulp suspension streams in the headbox nozzle, a continuously tapered separating wedge, which is arranged in the headbox nozzle by means of an articulation unit arranged upstream.

Furthermore, such a gap former is for a machine for producing a multilayer fibrous web, in particular a multilayer paper web. or board web, from at least two pulp suspensions, for example, from the German patent application DE 100 2005 003 531 A1 known. In particular, the show FIGS. 1A to 4B in each case a gap former whose first deflecting element for the first screen is a forming roller and whose second deflecting element for the second screen is a breast roller.

The majority of multi-layer drums are used today in the field of packaging machines for the production of testliner. The increasing production speeds as well as the rising raw material and energy costs increasingly require the production of multilayer products with lower basis weights. The multi-layer casseroles are for this purpose operated with ever smaller gap widths or pulp suspension jet thicknesses. As a result, however, the demands on the stability and the turbulence quality of the respective fibrous suspension jet coming from the headbox of the multi-layer headbox increase for the purpose of reducing the mixing zones within the pulp suspension jet in its height direction. The height direction is referred to in professional circles as "z-direction".

It is therefore an object of the invention to provide a sheet forming system of the type mentioned in such a way that both a high-quality layer purity in the height direction and a good optical coverage quality of the outer pulp suspension layers is achieved in a fibrous web produced with it. In particular, the production of a fibrous web having a basis weight in a range of 20 to 60 g / m ² per pulp suspension layer at a production speed of over 900 m / min should be possible.

This object is achieved in a sheet forming system of the type mentioned in the present invention that the at least one arranged in the headbox separating wedge a separating wedge supernatant in a range of 0.05 to 3.0, preferably from 0.1 to 2.0, in particular from 0.2 to 1.5, · the largest single gap width of the at least two nozzle chambers, that the separating wedge of two each having a separating wedge angle separating wedge areas, an upstream Trennkeilanfangsbereich and a downstream splitter end region, the two splitter wedge angles of the two splitter wedges assume different angles, with the splitter start angle of the upstream splice start region taking a greater angle than the spline end angle of the downstream splice end region, and between at least one splitter surface of the splitter a non-planar transition region between the two spline regions of the separating wedge is provided, that the pulp suspension free jet formed from the at least two pulp suspension streams has a free jet length in the range from 100 to 500 mm, preferably from 125 to 400 mm, in particular Other from 150 to 300 mm, and that the open forming roll has a diameter in the range of 1200 to 2500 mm, preferably from 1300 to 2400 mm, in particular from 1500 to 2200 mm.

The object of the invention is completely solved in this way.

The headbox of the multilayer headbox of the sheet forming system of the present invention thus constructed provides the advantage that the layer purity in the height direction can be markedly improved over known multi-layer headboxes. This is in principle due to the fact that the pressure loss and thus the fluid wall friction on the separating wedge can be reduced by shortening the separating wedge projection. Associated with this is a reduction of the turbulence forming in the pulp suspension streams with concomitant improvement of the layer purity in the height direction.

The separating wedge of the multilayer headbox of the sheet forming system according to the invention thus constructed also has the advantage that the layer purity in the vertical direction can again be markedly improved in comparison to known multilayer headboxes. This is primarily due to the fact that the angle of incidence of the two pulp suspension streams is significantly reduced when they are merged at the separating wedge end. Associated with this is once again a reduction of the turbulences forming in the pulp suspension streams with a concomitant improvement in the layer purity in the height direction.

The turbulence forming in the outer pulp suspension streams also substantially affects the coverage qualities of the outer pulp suspension layers. Now, if the turbulence is reduced, so also reduce the mixing zones within the pulp suspension jet in its height direction. And the reduced mixing zones, in turn, contribute significantly to improved coverage qualities of the outer pulp suspension layers.

Thus, in a fibrous web produced by means of the multilayer headbox according to the invention, both a high-grade layer purity in the height direction and a good optical cover quality of the outer fibrous stock suspension layers are achieved.

If the multi-layer casserole be designed as a three- or even four-layer casserole, so the separating wedge projections can have the same, approximately the same or even different values depending on the application.

In general, the individual separating wedge may consist of a high-grade steel or the like and have a minimum rigidity both in the machine direction and in the cross machine direction, which assumes at least a value of ≥ 40 N / mm in some areas. Moreover, the separating wedge is preferably by means of an upstream attached separating wedge recording rigid, so not articulated and thus not freely movable arranged in the headbox. By the upstream separating wedge recording of the separating wedge by definition extends in its longitudinal direction, preferably centrally aligned straight line.

Furthermore, the said free jet length of the pulp suspension jet formed from the at least two pulp suspension streams still ensures a free-jet quality which is sufficient in terms of process technology. The pulp suspension free jet undergoes no appreciable widening in the stated length range due to the air boundary layers forming on the two free-jet surfaces. Thus, by avoiding turbulence due to non-expansion of the pulp suspension jet, the layer purity of the pulp suspension streams in the height direction can be continued.

And finally, the open forming roll of the sheet forming system according to the invention with said diameter range provides the advantage of gentle dewatering of the at least two fibrous suspensions located between the two screens during their common guidance over a peripheral area of the open forming roll. The gentle dewatering of the at least two pulp suspensions is primarily the result of the relatively large diameter of the forming roll in conjunction with a sufficient dewatering length on the open forming roll. Depending on the application, the open forming roller may be vacuumed or unabsucked, with the suction of the forming roller being well known in the art.

The four features of the sheet formation system according to the invention which are essential to the invention ensure the continuous and process-reliable achievement of both a high-quality layer purity in the height direction and a good optical cover quality of the outer pulp suspension layers in a fibrous web produced therewith. It is also the production of a multi-layer fibrous web with a basis weight in a range of 20 to 60 g / m ² per pulp suspension layer at a production speed of about 900 m / min possible.

In a first embodiment according to the invention, it is provided that the at least one separating wedge arranged in the iris-free headbox nozzle has a separating wedge projection in a range from 0.05 to 1.0, preferably from 0.1 to 0.95, in particular from 0.2 to 0, 90, • has the largest single gap width of the at least two nozzle chambers. In this dazzle-free multi-layer casserole thus the requirement is met that no dazzling board due to the absence of a panel only a small separation wedge supernatant required.

In a further embodiment according to the invention, it is provided that a preferably adjustable diaphragm with an aperture immersion depth is arranged on at least one outer wall of the headbox nozzle and that the at least one separating wedge arranged in the headbox nozzle has a separating wedge projection in a range from 0.5 to ≦ 3.0, preferably from 0.6 to ≦ 2.0, in particular from 0.7 to 1.5, · has the largest single gap width of the at least two nozzle chambers. Thus, in this multi-layer casserole, the requirement that a large baffle board requires a larger wedge overhang is satisfied.

In the multilayer headbox of the sheet forming system according to the invention, it is of course also possible for a preferably adjustable iris with an iris depth to be arranged on both outer walls of the headbox nozzle. The setting of the aperture can be done, for example, by means of a plurality of arranged over the width of the headbox adjusting units, in particular servomotors. This minimizes the pressure loss in the respective pulp suspension layer.

Furthermore, the aperture of the multilayer headbox of the sheet forming system of the present invention may have an iris depth into the adjacent pulp suspension stream in a range of 1 to 30 mm, preferably in a range of 5 to 15 mm. This embodiment allows the generation of a minimum turbulence in the corresponding pulp suspension, but without equal to achieve the above-described disadvantageous turbulence level.

In order for the pulp suspensions conducted in pulp suspension streams to undergo an optimum combination in terms of process technology, the at least one separating wedge of the multilayer headbox of the sheet forming system according to the invention can have a separating wedge angle ≦ 10 °, preferably in a range between 3 and 7 °. In addition, these angular ranges avoid disadvantageous mixing of two adjacent pulp suspensions.

Furthermore, depending on the system requirement, at least one separating wedge for separating two adjacent pulp suspension streams of the multilayer headbox of the sheet forming system according to the invention can be arranged rigidly or in the headbox nozzle by means of an articulation unit arranged upstream. These embodiments allow an optimal design of the multilayer headbox of the sheet forming system according to the invention to different operational system requirements.

Moreover, the pulp suspension streams emerging from the headbox nozzle of the multilayer headbox of the sheet forming system according to the invention as a common pulp suspension jet can have different jet velocities. Thus, for example, the at least one difference in the jet speeds may assume a value in the range of 10 to 60 m / min, preferably 15 to 25 m / min. This significantly reduces the spread of the mixing cone in the pulp suspension jet to the relevant pulp suspension layer. These requirements may also be dependent on the former concept in a known manner.

In a further preferred embodiment, in each case a non-planar transition region between the two separating wedge areas of the separating wedge is provided on both separating wedge surfaces of the separating wedge. Thus, a markedly reduced angle of incidence of the two pulp suspension streams can be achieved when they are combined at the separating wedge end, this markedly reduced angle of impact then being carried by both separating wedge surfaces of the separating wedge.

In this case, at least the upstream separating wedge initial region of the separating wedge can be aligned symmetrically with respect to a straight line running through the upstream separating wedge receptacle of the separating wedge. In this case, if the downstream spline end region of the splitter key is oriented asymmetrically to a straight line passing through the upstream spline retainer of the splitter spline, then the splitter tip of the splitter will not lie on the straight line passing through the upstream spline retainer of the splitter spline.

However, both the upstream breaker wedge start region of the breaker wedge and the downstream breaker wedge end region of the breaker wedge may be symmetrically aligned with a straight line through the upstream wedge retainer of the breaker wedge such that the breaker wedge tip of the breaker wedge lies on the straight line passing through the upstream wedge retainer of the breaker wedge. The separating wedge in this case is then designed symmetrically to the straight line passing through the upstream separating wedge receptacle of the separating wedge.

And in a further preferred embodiment, a non-planar transition region between the two separating wedge areas of the separating wedge is provided on a separating wedge surface of the separating wedge, and on the other separating wedge surface of the separating wedge a planar transition region is provided between the two separating wedge areas of the separating wedge. The separating wedge thus forms one side a flat surface, so that the noticeably reduced angle of incidence of the two pulp suspension streams must be borne on their merger at the splitter end of the other side of the separating wedge.

In this case, at least the upstream separating wedge initial region of the separating wedge can be aligned symmetrically with respect to a straight line running through the upstream separating wedge receptacle of the separating wedge. In this case, if the downstream spline end region of the splitter key is oriented asymmetrically to a straight line passing through the upstream spline retainer of the splitter spline, then the splitter tip of the splitter will not lie on the straight line passing through the upstream spline retainer of the splitter spline.

However, both the upstream breaker wedge start region of the breaker wedge and the downstream breaker wedge end region of the breaker wedge may be oriented asymmetrically with respect to a straight line passing through the upstream breaker wedge retainer of the breaker wedge. In this case, the separating wedge tip of the separating wedge could then lie on the straight line passing through the upstream separating wedge holder of the separating wedge.

In order for the two pulp suspensions conducted in pulp suspension streams to undergo an optimum combination in terms of process technology, the separating wedge end angle of the downstream separating wedge end region preferably has an angle value in the range from 1.5 to 8 °, preferably from 2.5 to 4.5 °. In addition, these angular ranges avoid adverse mixing of the two adjacent pulp suspensions. The Trennkeilanfangswinkel the upstream Trennkeilanfangsbereichs in this case preferably has an angular value in the range of 8 to 20 °, preferably from 10 to 15 °, so that a sufficient minimum stiffness of the separating wedge is given both in the longitudinal direction and in the transverse direction.

Furthermore, in view of a sufficient guide length, it is advantageous for the two pulp suspension flows if the downstream separating wedge end region of the separating wedge has a downstream separating wedge end length in the range of 10 to 100 mm, preferably 15 to 75 mm, in particular 25 to 50 mm, and / or the downstream Trennkeilendbereich the separating wedge protrudes beyond the outlet gap of the headbox nozzle, preferably in a range of 10 to 25 mm.

Furthermore, the respective non-planar transition area on the separating wedge surface between the two separating wedge areas of the separating wedge of the multilayer headbox of the sheet forming system according to the invention may be geometrically angular or round with a radius of curvature in the range from 20 to 1000 mm, preferably from 100 to 500 mm, in particular from 150 to 250 mm, be designed.

In another embodiment, the open forming roll has an open area in the range of 60 to 99%, preferably 70 to 98%, especially 80 to 96%, of the total area of the forming roll, so that a mark free or nearly mark free, efficient and a gentle drainage of the at least two fibrous suspensions located between the two sieves during their joint guidance over a peripheral region of the open forming roller is possible. The open forming roller, as already mentioned, depending on the application, be vacuumed or unabsucked, the aspiration of the forming roller is well known in the art.

Moreover, the open forming roll preferably has one of the two wires together with the at least two located between them pulp suspensions entangled area with a wrap angle in the range of 15 to 260 °, preferably from 30 to 230 °, in particular from 50 to 180 °. These areas contribute significantly to the efficient and gentle dewatering of the at least two fibrous suspensions located between the two sieves during their joint guidance over a peripheral area of the open forming roll.

Also, the jet impingement of the pulp suspension free jet formed from the at least two pulp suspension streams may be directed to the open forming roll in the range of 0 to 100%, preferably 20 to 60% and the at least two pulp suspensions may have a respective stock consistency in the multilayer headbox of the sheet forming system of the present invention. 2 to 1.8%, preferably 0.5 to 1.6%, in particular from 0.7 to 1, 4%.

And the mode of operation of the multilayer headbox of the sheet forming system according to the invention can take place both in over- and underflow with the speed ranges 20 to 80 m / min or 20 to - 80 m / min.

Furthermore, it can be advantageous with regard to a regulation of both the fiber orientation transverse profile and the basis weight transverse profile of the multilayer fibrous web if the multilayer headbox is provided in a further embodiment with a dilution water control known from a large number of publications. For this purpose, a regulated feed stream, in particular a dilution water stream, can be fed to at least one pulp suspension when a mixed stream is produced with a mixed concentration.

1. a) Herstellung der wässrigen Faserstoffsuspension, insbesondere aus gemischtem Altpapier;
2. b) Reinigung dieser Faserstoffsuspension, sofern sie störende Verunreinigungen enthält;
3. c) Fraktionierung dieser Faserstoffsuspension in eine Kurzfaserfraktion mit vermehrt kurzen Fasern und eine Langfaserfraktion mit vermehrt langen Fasern; und
4. d) Verwendung dieser Fraktionen bei der Herstellung von einer mindestens eine Deckenlage und eine Rückseitenlage aufweisenden mehrschichtigen Faserstoffbahn, insbesondere Verpackungspapier oder Karton.

In a further preferred embodiment, at least one pulp suspension for the production of the multilayer fibrous web can also be produced with the following steps:

1. a) preparation of the aqueous pulp suspension, in particular of mixed waste paper;
2. b) cleaning of this pulp suspension, if it contains interfering impurities;
3. c) fractionation of this pulp suspension into a short fiber fraction with increasingly short fibers and a long fiber fraction with increasingly long fibers; and
4. d) Use of these fractions in the production of a multilayer fibrous web, in particular packaging paper or cardboard, having at least one cover layer and one backsheet.

It can be provided that the ceiling layer of the multi-layer fibrous web is formed from the short fiber fraction. Furthermore, it can be provided that the rear side layer of the multilayer fibrous web is formed from the long fiber fraction.

And for fractionation, at least one pressure sorter can be used in which, with the aid of a wet sieve, the pulp suspension is fractionated so that the long fiber fraction passes into the overflow and the short fiber fraction into the flow. In this case, sieves with slots whose slot width is 0.3 to 1 mm can be used for the fractionation.

Furthermore, it may be provided in an alternative embodiment that at least a three-ply packaging paper or at least three-ply cardboard is produced, wherein from the long fiber fraction, the middle layer of the multi-layer fibrous web is formed and wherein from the short fiber fraction, the top layer and the backsheet of the multi-layer fibrous web are formed. Or it can even be provided that an at least three-ply packaging paper or at least three-ply cardboard is produced, wherein the middle layer and the backsheet of the multi-layer fibrous web are formed from the long fiber fraction.

The sheet forming system according to the invention is particularly suitable for use in a machine for producing a multilayer fibrous web, in particular a multilayer paper or board web at least two pulp suspensions. In such a use, the advantages already mentioned arise.

Further features and advantages of the invention will become apparent from the following description of several preferred embodiments with reference to the drawings.

Figur 1

eine schematische Längsschnittdarstellung einer Ausführungsform eines erfindungsgemäßen Blattbildungssystems;

Figuren 2 bis 4

schematische Längsschnittdarstellungen von Endbereichen verschiedener Ausführungsformen einer jeweiligen Stoffauflaufdüse eines Mehrschichtenstoffauflaufs eines erfindungsgemäßen Blattbildungssystems; und

Figuren 5 und 6

schematische Seitendarstellungen zweier weiterer Ausführungsformen von Trennkeilen eines Mehrschichtenstoffauflaufs eines erfindungsgemäßen Blattbildungssystems.

It show the

FIG. 1

a schematic longitudinal sectional view of an embodiment of a sheet forming system according to the invention;

FIGS. 2 to 4

schematic longitudinal sectional views of end portions of various embodiments of a respective headbox of a multilayer headbox of a sheet forming system according to the invention; and

FIGS. 5 and 6

schematic side views of two further embodiments of separating wedges of a multilayer headbox of a sheet forming system according to the invention.

The FIG. 1 1 shows a schematic longitudinal sectional illustration of an embodiment of a sheet forming system 1 comprising a multilayer headbox 2 in the form of a two-layer headbox and a gap former 3. The illustrated sheet forming system 1 is a component of a machine not shown in more detail for producing a multi-layer fibrous web 4, in particular a multilayer paper or board web. from two pulp suspensions 5.1, 5.2.

The pulp suspensions 5.1, 5.2 will usually be suspensions of different pulps, but they may also be suspensions of the same pulps, but with different physical properties.

The multi-layer headbox 2 designed as a two-layer headbox comprises a headbox nozzle 6, which has two pulp suspension 5.1, 5.2, which extend across the width B (arrow) and are separated on the inside by a separating wedge 7 during operation of the multi-layer headbox 2, 5.10 (arrow). 5.20 (arrow) leading and converging nozzle chambers 8.1, 8.2. The two nozzle chambers 8.1, 8.2 have the same or approximately the same cross-sectional profiles. Furthermore, the respective nozzle chamber 8.1, 8.2 each upstream of a feed device 9.1, 9.2, not shown in detail, each downstream over the width B (arrow) extending exit slit 10.1, 10.2 with a gap s.10.1, s.10.2 and on the outside each have an outer wall 11.1, 11.2. The separating wedge 7 has two separating wedge surfaces 7.0, 7U touched during the operation of the multi-layer headbox 2 by the respectively adjacent fibrous stock suspension stream 5.10 (arrow), 5.20 (arrow).

The gap widths s.10.1, s.10.2 of the exit slits 10.1, 10.2 are the same size in the illustrated embodiment; however, they can be different in size. The respective feed device 9.1, 9.2, which is not illustrated in detail, is in the illustrated embodiment one of the headbox nozzle 6 directly upstream of the turbulence generator; However, it may also be arranged upstream of the headbox nozzle 6 indirectly and / or it may comprise a preferably machine-wide intermediate chamber or a pipe grid. These units are known to the person skilled in the art.

The separating wedge 7 is made of a stainless steel or the like and has a minimum stiffness S both in the longitudinal direction and in the transverse direction, which assumes at least a value of ≥ 40 N / mm in some areas. Moreover, the separating wedge 7 in the present embodiment by means of an upstream mounted wedge holder 12 is rigid, so not articulated and thus not freely movable in the headbox 6 is arranged. By the upstream Separating wedge holder 12 of the separating wedge 7 runs by definition a preferably in the longitudinal direction aligned centrally straight line G.

The multilayer headbox 2 is immediately followed by the gap former 3 with two continuous endless screens 13, 14. The first wire 13 passes over a peripheral portion 16 of an open-ended forming roll 15, not shown to scale, and the second wire 14 passes over a peripheral portion 18 of a breast roll 17, which is merely indicated and not drawn to scale, before being placed in the area of the open forming roll 15 first sieve 13 to form a wedge-shaped material inlet gap 19, which immediately with a free jet length L.20 from the headbox 6 of the multilayer headbox 2 as a common pulp suspension free jet 20 exiting pulp suspension flows 5.10 (arrow), 5.20 (arrow) accumulates runs. Subsequently, the two screens 13, 14 with the two fibrous suspensions 5.1, 5.2 between them form at least in parts a double-wire zone 21.

The pulp suspension streams 5.10 (arrow), 5.20 (arrow) emerging from the headbox nozzle 6 as a common pulp suspension jet 20 can have different jet velocities v.5.10 (arrow), v.5.20 (arrow). In this case, the difference in the jet velocities v.5.10 (arrow), v.5.20 (arrow) in particular assumes a value in the range from 10 to 60 m / min, preferably from 15 to 25 m / min.

The at least one separating wedge 7 arranged in the headbox nozzle 6 now has a separating wedge projection Ü.7 in a range from 0.05 to 3.0, preferably from 0.1 to 2.0, in particular from 0.2 to 1.5, the largest single gap width s.10.1 of the at least two nozzle chambers 8.1, 8.2.

At the in the FIG. 1 shown multilayer headbox 2 is on both outer walls 11.1, 11.2 of the headbox 6 each one preferably adjustable aperture 22.1, 22.2 arranged with an aperture immersion depth t.22.1, t.22.2. The respective orifice immersion depth t.22.1, t.22.2 in the adjacent pulp suspension flow 5.10 (arrow), 5.20 (arrow) assumes a value in a range of 1 to 30 mm, preferably in a range of 5 to 15 mm. The respective orifice immersion depth t.22.1, t.22.2 is by definition the vertical immersion depth of the respective orifice 22.1, 22.2 in the associated pulp suspension flow 5.10 (arrow), 5.20 (arrow). The adjustability of the corresponding aperture 22.1, 22.2 is indicated by a respective double arrow.

In this embodiment, the separating wedge 7 now has a separating wedge projection Ü.7 in a range from 0.5 to ≦ 3.0, preferably from 0.6 to ≦ 2.0, in particular from 0.7 to 1.5, • the largest Single gap width s.10.1 of the two nozzle chambers 8.1, 8.2. The separating wedge supernatant Ü.7 of the separating wedge 7 preferably assumes a value in a range of 10 to 25 mm.

Furthermore, the separating wedge 7 consists of two separating wedge regions each having a separating wedge angle .alpha., .Beta., An upstream separating wedge starting region 7.1 and a downstream separating wedge end region 7.2. The two separating wedge angles α, β of the two separating wedge areas 7.1, 7.2 assume different angle values, the separating wedge starting angle α of the upstream separating wedge starting area 7.1 assuming a larger angle value than the separating wedge final angle β of the downstream separating wedge end area 7.2. In addition, a non-planar transition region 23.0 between the two separating wedge areas 7.1, 7.2, of the separating wedge 7 is provided between at least one separating wedge surface 7.0 of the separating wedge 7. Also, both the upstream separating wedge initial region 7.1 of the separating wedge 7 and the downstream separating wedge end region 7.2 of the separating wedge 7 are aligned symmetrically with respect to a straight line G passing through the upstream separating wedge holder 12 of the separating wedge 7, so that the separating wedge tip 24 of the separating wedge 7 is supported by the separating wedges 12 upstream the separating wedge 7 extending straight line G is located.

Furthermore, the Trennkeilanfangswinkel α of the upstream Trennkeilanfangs 7.1 an angle value in the range of 8 to 20 °, preferably from 10 to 15 °, on. The Trennkeilendwinkel β of the downstream Trennkeilendbereichs 7.2, however, has an angle in the range of 1.5 to 8 °, preferably from 2.5 to 4.5 °, so that it is smaller than the Trennkeilanfangswinkel α of the upstream Trennkeilanfangs 7.1.

Also, the downstream Trennkeilendbereich 7.2 of the separating wedge 7 has a downstream Trennkeilendlänge L.7.2 in the range of 10 to 100 mm, preferably from 15 to 75 mm, in particular from 25 to 50 mm. The respective non-planar transition region 23.0, 23.U on the corresponding separating wedge surface 7.0, 7.U between the two separating wedge regions 7.1, 7.2 of the separating wedge 7 is round with a radius of curvature R.7.0, R.7.U in the range of 20 to 1000 mm , preferably from 100 to 500 mm, in particular from 150 to 250 mm. The individual non-planar transition region on the separating wedge surface between the two separating wedge regions of the separating wedge could also be geometrically angular (cf. FIGS. 5 and 6 ).

Moreover, the pulp suspension free jet 20 formed from the two pulp suspension streams 5.10 (arrow), 5.20 (arrow) has a free jet length L.20 in the range from 100 to 500 mm, preferably from 125 to 400 mm, in particular from 150 to 300 mm. And the merely indicated and not to scale illustrated open forming roller 15 has a diameter D.15 in the range of 1200 to 2500 mm, preferably from 1300 to 2400 mm, in particular from 1500 to 2200 mm.

The open forming roll 15 has an open area A.15 in the range of 60 to 99%, preferably 70 to 98%, in particular 80 to 96%, of the total area AG of the forming roll 15. Moreover, the open forming roller 15 has one of the two screens 13, 14 with the ones located between them Pulp suspensions 5.1, 5.2 together wrapped region B.15 with a wrap angle χ in the range of 15 to 260 °, preferably from 30 to 230 °, in particular from 50 to 180 °, on. The definition and appearance of both the looped region B.15 of the forming roll 15 and the wrap angle χ of the forming roll 15 are well known to those skilled in the art.

The FIGS. 2 to 4 show schematic longitudinal sectional views of end portions of three different embodiments of a respective headbox 6 of a multi-layer casserole 2 of a sheet forming system 1 according to the invention. The respective basic structure of this headbox nozzle 6 substantially corresponds to the basic structure in the FIG. 1 schematically illustrated headbox nozzle 6, so that reference is also made to this description of figures.

In the FIG. 2 Now, a multi-layer casserole 2 with a non-dazzling headbox 6 is shown. The separating wedge 7 arranged in this iris-free headbox 6 in this case has a separating wedge supernatant Ü.7 in a range from 0.05 to 1.0, preferably from 0.1 to 0.95, in particular from 0.2 to 0.90 largest single gap width s.1 0.1 of the two nozzle chambers 8.1, 8.2.

At the in the Figures 3 and 4 on the other hand, a preferably adjustable diaphragm 22.1 with a diaphragm immersion depth t.22.1 is arranged on each outer wall 11.1 of the headbox nozzle 6. The respective aperture immersion depth t.22.1 is by definition the vertical immersion depth of the respective aperture 22.1 in the associated pulp suspension stream 5.10 (arrow). The adjustability of the corresponding aperture 22.1 is indicated by means of a respective double arrow. The respective aperture immersion depth t.22.1 into the adjacent fibrous stock suspension 5.10 (arrow) assumes a value in a range of 1 to 30 mm, preferably in a range of 5 to 15 mm.

The two embodiments of the Figures 3 and 4 differ in that in the embodiment of the FIG. 3 the lower lip board L.11.2 of the lower outer wall 11.2 is greater than the Trennkeilstand Ü.7 of the separating wedge 7. On the other hand, in the embodiment of the FIG. 4 the lower lip wall L.11.2 of the lower outer wall 11.2 is smaller than the Trennkeilstand Ü.7 of the separating wedge 7. In both embodiments, the respective separating wedge 7, as already stated, again a Trennkeilstand Ü.7 in a range of 0.5 to ≦ 3, 0, preferably from 0.6 to ≤ 2.0, in particular from 0.7 to 1.5, • the largest single gap width s.10.1 of at least two nozzle chambers 8.1, 8.2 on.

Furthermore, in all four illustrated embodiments of the multilayer headbox 2, the pulp suspension streams 5.10 (arrow), 5.20 (arrow) emerging from the headbox nozzle 6 as a common pulp suspension free jet 20 can have different jet speeds v.5.10 (arrow), v.5.20 (arrow). In this case, the difference in the jet velocities v.5.10 (arrow), v.5.20 (arrow) in particular assumes a value in the range from 10 to 60 m / min, preferably from 15 to 25 m / min.

The two FIGS. 5 and 6 2 show schematic side views of two further embodiments of separating wedges 7 of a multilayer headbox 2 of a sheet forming system 1 according to the invention.

On both separating wedges 7, a non-planar transition region 23.0 between the two separating wedge areas 7.1, 7.2 of the separating wedge 7 is provided only on a separating wedge surface 7.0 of the separating wedge 7. At the other separating wedge surface 7.U of the separating wedge 7, a planar transition region 23.U, that is to say no change in geometry between the two separating wedge regions 7.1, 7.2 of the separating wedge 7, is provided.

In the in the FIG. 5 illustrated embodiment, the upstream Trennkeilanfangsbereich 7.1 of the separating wedge 7 is symmetrical to one through the upstream separating wedge recording 12 of the separating wedge 7 extending straight line G, wherein the straight line G was as already defined above. However, since the downstream Trennkeilendbereich 7.2 of the separating wedge 7 is oriented asymmetrically to the running through the upstream separating wedge holder 12 of the separating wedge 7 straight line G, the separating wedge tip 24 of the separating wedge 7 is not on the running through the upstream separating wedge holder 12 of the separating wedge 7 straight G.

And in the in the FIG. 6 In the embodiment shown, both the upstream separating wedge starting region 7.1 of the separating wedge 7 and the downstream separating wedge end region 7.2 of the separating wedge 7 are aligned asymmetrically with respect to a straight line G passing through the upstream separating wedge holder 12 of the separating wedge 7, wherein the straight line G has been defined above. However, in this embodiment it is provided that the separating wedge tip 24 of the separating wedge 7 lies on the straight line G passing through the upstream separating wedge holder 12 of the separating wedge 7. But it could also be wrong.

In both embodiments of the FIGS. 5 and 6 the respective Trennkeilanfangswinkel α of the upstream Trennkeilanfangsbereich 7.1 turn an angle value in the range of 8 to 20 °, preferably from 10 to 15 °, on. The respective Trennkeilendwinkel β of the downstream Trennkeilendbereichs 7.2 again has an angular value in the range of 1.5 to 8 °, preferably from 2.5 to 4.5 °, so that it is smaller than the Trennkeilanfangswinkel α of the upstream Trennkeilanfangs 7.1. And the downstream Trennkeilendbereich 7.2 of the respective separating wedge 7 has a downstream Trennkeilendlänge L.7.2 in the range of 10 to 100 mm, preferably from 15 to 75 mm, in particular from 25 to 50 mm.

Unlike in the FIG. 1 illustrated embodiment of the separating wedge 7 is the respectively in the two FIGS. 5 and 6 illustrated non-planar transition region 23.0 on the wedge surface 7.0 between the two Trennkeilbereichen 7.1, 7.2 of the individual separating wedge 7 designed geometrically angular. The transition extends in the transverse direction of the separating wedge 7 along a line L. The respective non-planar transition region could also be designed around with a corresponding radius of curvature.

The respectively in the FIGS. 1 to 4 shown multilayer headbox 2 is particularly suitable for use in a machine for producing a multi-layer fibrous web 4, in particular a multilayer paper or board web, from at least two pulp suspensions 5.1, 5.2.

And finally, at least one pulp suspension, a controlled feed stream, in particular a dilution water stream when generating a mixed stream with a mixed concentration be fed. This makes it possible to control both the fiber orientation transverse profile and the basis weight transverse profile of the multilayer fibrous web.

In summary, it should be noted that the invention provides a sheet forming system of the type mentioned in the introduction, which makes it possible to achieve both high-quality layer purity in the height direction and good optical cover quality of the outer pulp suspension layers in a fibrous web produced therewith. This is also made possible, in particular, in the production of a fibrous web having a weight per unit area in the range from 20 to 60 g / m ² per pulp suspension layer at a production speed of over 900 m / min.

LIST OF REFERENCE NUMBERS

1

Sheet forming system

2

Multi-layer headbox

3

gap former

4

Multilayer fibrous web

5.1

Fibrous suspension

5.10

Pulp suspension stream (arrow)

5.2

Fibrous suspension

5.20

Pulp suspension stream (arrow)

6

headbox

7

separating wedge

7.1

Upstream separating wedge starting area

7.2

Downstream separating wedge end area

7.0

Separating wedge surface

7.U

Separating wedge surface

8.1

nozzle chamber

8.2

nozzle chamber

9.1

feeding

9.2

feeding

10.1

exit slit

10.2

exit slit

11.1

outer wall

11.2

outer wall

12

Separating wedge retainer

13

First sieve

14

Second sieve

15

forming roll

16

peripheral region

17

breast roll

18

peripheral region

19

Stock inlet gap

20

Fibrous suspension free jet

21

twin

22.1

cover

22.2

cover

23.0

Transition area

23.U

Transition area

24

Separating wedge tip

A.15

Open area

AG

total area

B

Width (arrow)

B.15

Enveloped area

D.15

diameter

G

Just

L

line

L.11.2

Lower lip Board

L.20

Free jet length

L.7.2

Downstream separating wedge end length

R.7.O

rounding radius

R.7.U

rounding radius

S

minimum stiffness

s.10.1

gap width

s.10.2

gap width

t.22.1

Baffle immersion depth

t.22.2

Baffle immersion depth

Ü.7

Separating wedge supernatant

v.5.10

Jet velocity (arrow)

v.5.20

Jet velocity (arrow)

α

Separating wedge angle

β

Separating wedge angle

χ

Wrap angle

Claims (15)

Sheet forming system (1) for a machine for producing a multilayer fibrous web (4), in particular a multilayer paper or board web, from at least two pulp suspensions (5.1, 5.2), comprising a multilayer headbox (2) with a headbox nozzle (6) containing at least two extending over the width (B) of the machine, separated by at least one separating wedge (7), during operation of the multilayer headbox (2) each have a pulp suspension (5.1, 5.2) as pulp suspension flow (5.10, 5.20) leading and converging nozzle chambers ( 8.1, 8.2), which each upstream of a feed device (9.1, 9.2) and downstream each have an across the width (B) extending exit gap (10.1, 10.2) having a gap width (s.10.1, s.10.2), wherein the both outer nozzle chambers (8.1, 8.2) on the outside each have an outer wall (11.1, 11.2) and wherein the separating wedge (7) zw Separating wedge surfaces (7.0, 7.U) contacted by the respectively adjacent pulp suspension stream (5.10, 5.20) during operation of the multilayer headbox (2), and a gap former (3) with two circulating endless sieves (13) immediately following the multi-layer headbox (2) , 14), of which the first wire (13) runs over a peripheral region (16) of a forming roll (15) and of which the second wire (14) runs over a peripheral region (18) of a breast roll (17) and thereafter in the region of Forming roller (15) on the first sieve (13) to form a wedge-shaped Stoffeinlaufspalts (19), which immediately [[with a free jet length (L.20)] from the headbox (6) of the multi-layer headbox (2) as a common pulp suspension free jet (20) emerges pulp suspension flows (5.10, 5.20) accumulates, and the two sieves ( 13, 14) with the at least two fibrous suspensions (5.1, 5.2) between them then at least in sections form a double-wire zone (21),
characterized,
in that the at least one separating wedge (7) arranged in the headbox nozzle (6) has a separating wedge projection (Ü.7) in a range from 0.05 to 3.0, preferably from 0.1 to 2.0, in particular from 0.2 to 1.5, • the largest single gap width (s.10.1) of the at least two nozzle chambers (8.1, 8.2), that the separating wedge (7) consists of two each one wedge angle (α, β) having Trennkeilbereichen (7.1, 7.2), an upstream Separating wedge start region (7.1) and a downstream Trennkeilendbereich (7.2), that the two Trennkeilwinkel (α, β) of the two Trennkeilbereiche (7.1, 7.2) assume different angle values, wherein the Trennkeilanfangswinkel (α) of the upstream Trennkeilanfangsbereich (7.1) a larger angle value assumes as the Trennkeilendwinkel (β) of the downstream Trennkeilendbereichs (7.2), and that between at least one separating wedge surface (7.O; 7.0, 7.U) of the separating wedge (7) a non-planar transition region (23.O; .0, 23.U) between the two separating wedge regions (7.1, 7.2) of the separating wedge (7), that the fibrous suspension free jet (20) formed from the at least two fibrous suspension streams (5.10, 5.20) has a free jet length (L.20) in the region from 100 to 500 mm, preferably from 125 to 400 mm, in particular from 150 to 300 mm, and that the open forming roll (15) has a diameter (D.15) in the range from 1200 to 2500 mm, preferably from 1300 to 2400 mm , in particular from 1,500 to 2,200 mm. Sheet forming system (1) according to claim 1,
characterized,
in that the at least one separating wedge (7) arranged in the iris-free headbox nozzle (6) has a separating wedge projection (Ü.7) in a range from 0.05 to 1.0, preferably from 0.1 to 0.95, in particular from 0.2 to 0.90, • the largest single gap width (s.10.1) of the at least two nozzle chambers (8.1, 8.2). Sheet forming system (1) according to claim 1,
characterized,
in that at least one outer wall (11.1, 11.2, 11.1) of the headbox nozzle (6) a preferably adjustable aperture (22.1, 22.2; 22.1) with an aperture immersion depth (t.22.1, t.22.2; t.22.1) is arranged and that the at least a separating wedge (7) arranged in the headbox nozzle (6) has a separating wedge projection (Ü.7) in a range from 0.5 to ≦ 3.0, preferably from 0.6 to ≦ 2.0, in particular from 0.7 to 1 , 5, · the largest single gap width (s.10.1) of the at least two nozzle chambers (8.1, 8.2). Sheet forming system (1) according to one of the preceding claims,
characterized,
that at both separating wedge surfaces (7.0, 7.U) of the separating wedge (7) each have a non-planar transition region (23.0, 23.U) between the two separating wedge areas (7.1, 7.2) of the separating wedge (7) is provided. Sheet forming system (1) according to one of the preceding claims,
characterized,
in that at least the upstream separating wedge initial region (7.1) of the separating wedge (7) is aligned symmetrically with respect to a straight line (G) running through the upstream separating wedge holder (12). Sheet forming system (1) according to claim 4 or 5,
characterized,
in that both the upstream separating wedge starting region (7.1) of the separating wedge (7) and the downstream separating wedge end region (7.2) of the separating wedge (7) are aligned symmetrically with respect to a straight line (G) passing through the upstream separating wedge holder (12) of the separating wedge (7) in that the separating wedge tip (24) of the separating wedge (7) lies on the straight line (G) passing through the upstream separating wedge receptacle (12) of the separating wedge (7). Sheet forming system (1) according to one of claims 1 to 3,
characterized,
that at a parting wedge surface (7.0) of the separating wedge (7) has a non-planar transition region (23.0) between the two separating wedge areas (7.1, 7.2) of the separating wedge (7) is provided and that on the other separating wedge surface (7.U) of the separating wedge (7 ) a planar transition region (23.U) between the two separating wedge areas (7.1, 7.2) of the separating wedge (7) is provided. Sheet forming system (1) according to claim 7,
characterized,
in that at least the upstream separating wedge initial region (7.1) of the separating wedge (7) is aligned symmetrically with respect to a straight line (G) running through the upstream separating wedge receptacle (12) of the separating wedge (7). Sheet forming system (1) according to claim 7,
characterized,
in that both the upstream separating wedge initial region (7.1) of the separating wedge (7) and the downstream separating wedge end region (7.2) of the separating wedge (7) are aligned asymmetrically with respect to a straight line (G) passing through the upstream separating wedge holder (12) of the separating wedge (7). Sheet forming system (1) according to one of the preceding claims,
characterized,
in that the separating wedge initial angle (α) of the upstream separating wedge starting region (7.1) of the separating wedge (7) has an angular value in the range of 8 to 20 °, preferably 10 to 15 °, and in that the separating wedge end angle (αβ) of the downstream separating wedge end region (7.2) of the separating wedge (7) has an angular value in the range of 1.5 to 8 °, preferably from 2.5 to 4.5 °. Sheet forming system (1) according to one of the preceding claims,
characterized,
that the downstream separating (7.2) of the separating wedge (7) has a downstream Trennkeilendlänge (L.7.2) in the range of 10 to 100 mm, preferably from 15 to 75 mm, in particular from 25 to 50 mm. Sheet forming system (1) according to one of the preceding claims,
characterized,
that the downstream separating (7.2) of the separating wedge (7) via the exit gap (10.1, 10.2) of the headbox nozzle (6) extends, preferably in a range of 10 to 25 mm. Sheet forming system (1) according to one of the preceding claims,
characterized,
that the open forming roll (15) having an open face (A.15) in the range of 60 to 99%, preferably from 70 to 98%, in particular from 80 to 96% of the total area (AG) of the forming roll (15). Sheet forming system (1) according to one of the preceding claims,
characterized,
in that the open forming roll (15) has a region (B.15) co-wrapped by the two wires (13, 14) with the at least two pulp suspensions (5.1, 5.2) between them, with a wrap angle (χ) in the range of 15 to 260 °, preferably from 30 to 230 °, in particular from 50 to 180 °. Machine for producing a multilayer fibrous web (4), in particular a multilayer paper or board web, from at least two pulp suspensions (5.1, 5.2),
characterized,
in that it comprises at least one sheet forming system (1) according to one of the preceding claims.

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