DE102011003970A1 - A forming apparatus - Google Patents

Abstract

The invention relates to a sheet-forming device (1) for producing a two- or multi-layer fibrous web (2) from at least two fibrous suspensions (3), at least comprising a first wire (4) on which a first and preferably single-layer headbox (5) has a first layer (6) applies to pulp suspension (3) and which is guided with the overlying layer (6) of pulp suspension (3) over a stationary screen table (7) and several dewatering elements (8), a second headbox (9), which on the first , on the first sieve (4) lying layer (6) of pulp suspension (3) a second layer (10) of pulp suspension (3) applies, and a second sieve (11), which with the first sieve (4) at least partially a wedge-shaped inlet gap (13) having twin wire zone (12) forms. The sheet forming device (1) according to the invention comprises in the area (B) the application, preferably - viewed in the direction of wire travel (S) - before the application of the second layer (10) of fiber suspension (3) to the first layer (6) of fiber suspension (3) ) underneath the first screen (4) a first screen (4) leading dewatering element (17), which has a downwardly curved guide surface (17.A) with an angle of curvature (17.W) of ≥ 1 °, preferably ≥ 2 ° , in particular of ≥ 3 °. Furthermore, it comprises at least one inlet strip (21) which is arranged in the area of the wedge-shaped inlet gap (13) and / or - viewed in the direction of the wire (S) - after the area of the wedge-shaped inlet gap (13), which is arranged by means of at least one flexible element ( 22) and which can be pressed against the first sieve (4) and / or the sieve sandwich formed from the two sieves (4, 11) with the layers (6, 10) in between with a selectable force (22.F).

Description

The invention relates to a sheet forming apparatus for producing a two- or multi-ply fibrous web, in particular a cardboard or packaging paper web, from at least two pulp suspensions, at least comprising a first, preferably designed as a wire screen on which a first and preferably monolayer headbox to a first layer Fibrous suspension applies and which is guided with the overlying layer of pulp suspension on a stationary screen and several dewatering elements, a second and preferably single-layer headbox, which applies to the first, resting on the first screen layer of pulp suspension, a second layer of pulp suspension, and a second , Preferably designed as a top wire sieve, which at least in sections forms a wedge-shaped inlet gap having a double-wire zone with the first sieve, wherein in the twin-wire zone via an inlet roller led second sieve over a plurality of rigidly arranged and at least one radius of curvature, preferably at least two radii of curvature descriptive strips runs, which are arranged at a mutual distance to a drainage box.

Such a sheet forming device is for example from the document DE 91 15 632 U1 known. The disclosed sheet forming apparatus comprises a twin-wire former for producing a fibrous web from a pulp suspension having the following features: two screen belts forming a twin-wire zone with each other; in the twin-wire zone, the one wire belt runs over rigid strips, which are arranged at a mutual distance on a drainage box; and in the twin-wire zone, moreover, the other screen belt runs over a number of strips which lie opposite the rigid strips, are supported by means of resilient elements and can be pressed against the other screen belt with a selectable force. In one of the sieve loops, a closed sieve support surface is provided in the direction of the strips located there, which may be formed by a plate or the sliding surface of a forming shoe.

In the in the 2 illustrated embodiment of the sheet forming apparatus, a secondary headbox is arranged next to a primary headbox immediately before the start of the twin-wire zone. Below the secondary headbox a curved suction box is provided, over which the other sieve is guided.

Furthermore, from the two documents DE 40 31 038 A1 and DE 199 51 928 A1 a sheet forming device is known, each having a arranged above a horizontally extending wire longitudinal secondary headbox with a subsequent upper sieve unit comprising a top wire and a straight suction box with rigid strips. At the beginning of the horizontally extending wire, a primary headbox is arranged in each case.

A sheet forming apparatus is also known from the document DE 102 23 398 A1 known. The illustrated sheet forming apparatus comprises a secondary headbox disposed above a horizontally extending wire with a subsequent upper wire unit comprising a top wire and a straight suction box with rigid rails. In addition, a plurality of formation strips are provided, which are mutually arranged on the rigid strips of the suction box, which are supported by means of resilient elements and which can be pressed with a selectable force against the wire. At the beginning of the horizontally extending wire again a primary headbox is arranged.

Furthermore, from the document US 6,190,500 B1 a sheet forming apparatus having a horizontally extending wire with two overhead headboxes, a primary headbox and a secondary headbox. The wire is in this case no further Obersiebeinheit assigned. The known Obersiebeinheiten can, as can be seen in the cited references, have a straight or a curved Siebführung. Moreover, the Siebzusammenführung the two sieves, ie the first and the second sieve, carried out on rigid and curved elements. In general, moreover, no major deflection of the sieve guide in the area of the jet impact point or in front of the jet impact point of the secondary headbox is provided.

When applying the pulp suspension jet of the secondary headbox resulting from the above conditions restrictions on maximum sieve speed and basis weight or pulp suspension height. Consequently, there are limitations in the achievable quality of coverage.

Furthermore, there are also restrictions in the Siebzusammenführung. Due to the rigid and curved elements on the Siebzusammenführung relatively strong pressure pulses are generated in the pulp suspensions. However, the incoming and to be formed fibrous web has by the order of the secondary headbox a very significant difference in substance density in their z-direction, ie height direction. Below is an already finished fiber mat with fabric densities on the immobility point of the fiber, whereas the top of the still applied by the secondary headbox and still liquid pulp suspension is located. Consequently, the sieve sandwich must then be stably guided without negatively affecting the still very sensitive and to be formed fibrous web.

It is therefore an object of the invention to improve a sheet forming apparatus of the type mentioned in such a way that the production of a two- or multi-layer fibrous web using a secondary headbox at higher Siebgeschwindigkeiten and better quality properties, in particular the at least one applied to the secondary headbox layer is ensured continuously and reliably. This object is achieved in a sheet forming apparatus of the type mentioned in the present invention that in the field of application, preferably - seen in wire direction - before applying the second layer of pulp suspension to the first layer of pulp suspension on the underside of the first screen leading a first sieve Dewatering element is arranged, which has a downwardly curved guide surface with a curvature angle of ≥ 1 °, preferably of ≥ 2 °, in particular of ≥ 3 °, and that at least one inlet strip, which in the region of the wedge-shaped inlet gap and / or - in Sawing direction (S) seen - after the area of the wedge-shaped inlet gap ( 13 ) which is supported by at least one resilient element and which can be pressed with a selectable force against the first sieve and / or the sieve sandwich formed by the two sieves with the layers lying therebetween.

The angle of curvature here is by definition the angle between the initial screen direction of the first screen with the first layer of pulp suspension lying thereon and the changed screen direction of the first screen after application of the second layer of pulp suspension to the first layer of pulp suspension.

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

The embodiment of the sheet forming device according to the invention achieves an improvement both by means of gentle insertion geometry and by a gentler wire consolidation geometry.

The gentle injection of the second layer of pulp suspension is achieved by the described significant curvature of the sieve guide in the region of the beam impact point or before the Strahlauftreffpunkt the secondary headbox. The entry angle can be kept to a minimum, while taking into account minimum distances of the secondary headbox to the first sieve and the shortest possible free jet length of the second layer of pulp suspension.

The gentle sieve consolidation of the two sieves is made possible by the use of flexibly pressureable inlet strips in the area of the sieve junction. This makes it possible to set a sieve guide which is variable in the radius guide, which at the same time allows gentle pressure pulses to act on the two layers of pulp suspension due to the flexible contact pressure. By virtue of the gentler pressure pulses, however, the two layers of pulp suspensions in the sieve sandwich after sieve consolidation, that is to say in the region of the dewatering box, are even more sensitive. Thus, the combination with a curved sieve guide is necessary here, which supports the two layers of pulp suspensions in their further course stable until a higher consistency is reached.

Due to the sum of these measures, the use window of the secondary headbox can be significantly increased.

The drainage element having a downwardly curved guide surface preferably has a preferably constant radius of curvature between 2,000 and 20,000 mm, whereby the smoothness of the injection of the second layer of pulp suspension is pronounced even more positively. In this way, the realization of a minimum free jet length is made possible in a simple manner, whereby the beam quality and thus the sheet quality and the cover quality of the second layer is improved in the two- or multi-ply fibrous web to be formed.

Alternatively, the drainage element having a downwardly curved guide surface may also have a preferably continuously decreasing radius of curvature, which in turn has a positive effect on the smoothness of the injection of the second layer of pulp suspension. The downwardly curved guide surface of the dewatering element may for example have a parabolic longitudinal contour. Thus, possible centrifugal forces do not act abruptly on the lower layer, but they are built up. This significantly reduces the risk of possible sheet disturbances in the two- or multi-layer fibrous web to be formed.

The second and preferably single-layer headbox, which applies the second layer of pulp suspension to the first layer of pulp suspension, preferably has a turbulence generator with a grating pitch in the cross-machine direction of ≦ 30 mm. The turbulence generator, in professional circles Also referred to as turbulence unit or turbulence generator, consists of a turbulence block, which is provided with preferably drilled turbulence channels, or a bundle of individual turbulence tubes, which are held at least at two points by means of anchor plates. The cited lattice distribution causes effective and cost effective avoidance of streaking in the second layer of pulp suspension. As a result, the beam quality and thus the sheet quality and the coverage quality of the second layer is improved in the forming two- or multi-ply fibrous web.

Furthermore, the second and preferably single-layer headbox, which applies the second layer of pulp suspension to the first layer of pulp suspension, preferably has a headbox nozzle in which at least one lamella is arranged. Such a lamella arranged in the headbox is ideally made of a plastic, preferably a high conductivity polymer such as in particular PPSU, PPS, PEI, PTFE, PA, POM or the like, and it has a positive effect on the generation and maintenance of micro-turbulence in the second layer Pulp suspension, which ultimately in turn is reflected in improved quality properties of the second layers of pulp suspensions.

In the region of the wedge-shaped inlet gap and / or - seen in the direction of wire direction - after the region of the wedge-shaped inlet gap preferably at least two inlet strips are arranged, which are each supported by at least one resilient element and each with a selectable force against the first sieve and / or that the Siebsandwich formed from the two sieves with the intermediate layers are pressed. The at least two inlet strips can be positioned in their respective position. As a result, the sieve sandwich with the two sieves with the intermediate layers of pulp suspensions is sufficiently out and stabilized, whereby ultimately a higher quality is achieved in the forming two- or multi-layer fibrous web. Furthermore, on the one hand as soft as possible performance of the second sieve on the second layer of pulp suspension can be achieved with a gentle pressure pulse, on the other hand, the well-defined area of the merger of the two screens to avoid air bubbles or other disorders can be used.

The at least two inlet strips preferably have a strip width in the range from 2 to 50 mm, preferably from 5 to 30 mm, in particular from 10 to 20 mm, a strip spacing in the range from 50 to 200 mm, preferably from 100 to 150 mm, in particular approximately 120 mm, and / or a foil angle in the range of +2 to -2 °, preferably from +1 to -1 °, in particular from +1 to 0 °, on. As a result, in a very efficient manner influence on the Siebführung on the pressure pulse expression in the performance of the second sieve on the two layers of pulp suspensions and the underlying first sieve are taken. Furthermore, sufficient guidance and stabilization of the two screens with the intervening layers of pulp suspension is ensured.

The first sieve runs in the twin-wire zone preferably over 2 to 8, preferably over 3 to 6, in particular 5 formation strips, which are mutually arranged on the rigid strips of the dewatering box, which are supported by resilient elements and which can be pressed against the first wire with a selectable force are. The formation strips preferably have a 1: 1, 2: 1 or 3: 1 splitting in relation to the splitting of the strips rigidly arranged on the drainage box. These formation strips are also preferably arranged only with respect to the first dewatering zone of the dewatering box.

The rigidly arranged on the drainage box strips preferably describe at least one radius of curvature, preferably at least two radii of curvature with a respective radius of curvature in the range of 1,500 to 10:00 mm, preferably from 2,000 to 7,500 mm, preferably from 2,000 to 5,000 mm. The increased curvature allows the realization of a higher dewatering pressure on the at least two layers of pulp suspension due to the acting wire tension to achieve the same dewatering performance as on a forming roll.

And the bars rigidly arranged on the drainage box moreover preferably have at least two radii of curvature with values increasing in the direction of the direction of the sieve. The advantage of this design is that the drainage of the at least two layers of pulp suspensions is thus gentler with increasing drainage.

Moreover, the drainage box - as seen in the direction of wire drainage - preferably has a skimmer zone and at least one dewatering zone, preferably at least two dewatering zones. The first dewatering zone of the dehydration box has a radius of curvature in the range of 1,000 to 5,000 mm, preferably of about 2,000 mm, an open area in the range of 100 to 40% and a pitch in the range of 60 mm, and those in FIGS - Seen in the direction of wire drainage - second dewatering zone of the drainage box has a radius of curvature in the range of 3,000 to 10,000 mm, preferably of about 5,000 mm, an open area in the range of 100 to 40% and a pitch in the range of 50 mm. The advantage here is that the drainage of the at least two layers of pulp suspensions with gentle dewatering occurs thereby. The same situation also applies to the two divisions in the first and second dewatering zone of the dewatering box. The sieve guide of the two sieves with the intermediate layers of pulp suspensions can be carried out in a known manner in a known manner after the drainage box arranged in the sieve loop of the second sieve:

Thus, the two screens with the intervening layers of pulp suspensions in the twin-wire zone can still be guided over a roller, in particular a suction roller or a solid roller, so that a change in the wire direction is downward, in particular vertically or approximately vertically downwards. In this case, then the two sieves can be separated with the intermediate layers of pulp suspensions and the sieve with the layers of fibrous suspensions lying on it can be passed over a Gautschelement, in particular a Gautschwalze or a Gautschschuh, the two layers of pulp suspensions to another and led to a further sieve guided layer of pulp suspension. Depending on the sieve separation, the layer of pulp suspension guided by the further sieve can be moved counter to the direction of the sieve of the first sieve or in the direction of the sieve of the first sieve. As a result, it is generally possible to produce an at least three layers of fibrous web.

However, the two screens with the intervening layers of pulp suspensions can also be separated and the two layers of pulp suspensions are guided on the first sieve. This makes it possible to produce a two-ply fibrous web, in particular.

The sheet forming apparatus according to the invention can also be used in an excellent manner in a machine for producing a multilayer fibrous web, in particular a cardboard or packaging paper web, from at least two fibrous stock suspensions. This then results in the already mentioned above advantages of the invention.

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

Show it

1 a schematic detail view of a preferred embodiment of a sheet forming apparatus according to the invention for producing a two- or multi-layer fibrous web;

1a a schematic detail of the in the 1 shown preferred embodiment of a sheet forming apparatus according to the invention for producing a two- or multi-layer fibrous web; and

2 to 4 schematic side views of three further preferred embodiments of a respective sheet forming apparatus according to the invention for producing a two- or multi-layer fibrous web.

The 1 shows a schematic detail view of a preferred embodiment of a sheet forming apparatus according to the invention 1 for producing a two- or multi-ply fibrous web 2 , in particular a cardboard or packaging paper web, from at least two pulp suspensions 3 ,

The illustrated sheet forming apparatus 1 comprises a first, preferably designed as a wire screen 4 on which a first and preferably one-layer headbox 5 (see. 2 to 4 ) a first location 6 on pulp suspension 3 applies and which with the lying situation 6 on pulp suspension 3 over a stationary sieve table 7 and several drainage elements 8th is led (see also 2 to 4 ).

Furthermore, the illustrated sheet forming apparatus comprises 1 a second and preferably single-layer headbox 9 , the first on the first sieve 4 overlying situation 6 on pulp suspension 3 a second location 10 on pulp suspension 3 applies. The two pulp suspensions 3 for the two layers 6 . 10 generally possess different qualities.

Furthermore, a second, preferably designed as a top wire sieve 11 provided, which with the first sieve 4 at least in parts a wedge-shaped inlet gap 13 having twin-wire zone 12 forms, wherein in the twin-wire zone 12 that via an inlet roller 14 guided second sieve 11 over several rigidly arranged and two radii of curvature 15.K1 . 15.K2 descriptive strips 15 running, with mutual distance 15.a. So with a division of forces 15.T on a drainage box 16 are arranged.

The on the drainage box 16 rigidly arranged strips 15 describe two radii of curvature 15.K1 . 15.K2 with a respective radius of curvature in the range of 1500 to 10.00 mm, preferably from 2,000 to 7,500 mm, preferably from 2,000 to 5,000 mm. It is advantageous if the staring ledges 15 at least two radii of curvature 15.K1 . 15.K2 with increasing values in the direction of the sweep S (arrow).

In the area B of the application, preferably - seen in the direction of wire direction (S) - before the application of the second layer 10 on pulp suspension 3 on the first location 6 on pulp suspension 3 is now below the bottom of the first sieve 4 a first sieve 4 leading drainage element 17 arranged, which has a downwardly curved guide surface 17.A with a bending angle 17.W of ≥ 1 °, preferably of ≥ 2 °, in particular of ≥ 3 °.

The angle of curvature 17.W Here, by definition, is the angle between the initial screen direction SH (arrow) of the first screen 4 with lying on first layer 6 on pulp suspension 3 and the changed Sieblaufrichtung SN (arrow) of the first sieve 4 after application of the second layer 10 on pulp suspension 3 on the first location 6 on pulp suspension 3 , In the present embodiment, the initial screen direction SH (arrow) is oriented horizontally or approximately horizontally, whereas the changed screen direction SN (arrow) is oriented slightly downwards and between the dewatering element 17 and the drainage box 16 is oriented.

The one downwardly curved guide surface 17.A having drainage element 17 has a preferably constant radius of curvature 17.K between 2,000 and 20,000 mm. Alternatively and not shown, the drainage element having a downwardly curved guide surface may also have a preferably continuously decreasing radius of curvature, for example in the form of a parabolic longitudinal contour.

The second layer 10 on pulp suspension 3 on the first location 6 on pulp suspension 3 applying second and preferably single-layer headbox 9 has a turbulence generator 18 with a grid pitch 18.T in cross machine direction CD (arrow) of ≤ 30 mm. Also, the second and preferably single-layer headbox 9 a headbox nozzle 19 on, in which two lamellae 20 between the three rows 18.R1 to 18.R3 of the turbulence generator 18 are arranged.

Moreover, as in the 1a shown in a schematic detail, at least one inlet strip 21 provided in the area of the wedge-shaped inlet gap 13 and / or - in the direction S as seen in the direction S (arrow) - after the area of the wedge-shaped inlet gap 13 is arranged, by means of at least one resilient element 22 is supported and with a selectable force 22.F (Arrow) against the first sieve 4 and / or the two seven 4 . 11 with the intermediate layers 6 . 10 made sieve sandwich is pressable. In the present embodiment, a total of three such inlet strips 21 intended.

The respective inlet rail 21 a last width 21.b in the range from 2 to 50 mm, preferably from 5 to 30 mm, in particular from 10 to 20 mm, a division of the bars 21.T in the range of 50 to 200 mm, preferably 100 to 150 mm, in particular about 120 mm, and / or a foil angle 21.W in the range of +2 to -2 °, preferably from +1 to -1 °, in particular from +1 to 0 °, on.

Continue to run the first sieve 4 in the twin-wire zone 12 over 2 to 8, preferably over 3 to 6, in particular 5 formation strips 23 , The formation bars 23 are mutually the rigid bars 15 of the drainage box 16 arranged, by means of compliant elements 24 supported and with a selectable force 24.F (Arrow) against the first sieve 4 pressed. As a rule, the formation strips 23 a division of parts 23.T from 1: 1, 2: 1 or 3: 1 in terms of splitting 15.T the at the drainage box 16 rigidly arranged strips 15 exhibit.

And the drainage box 16 itself points - as seen in the wire direction S (arrow) - a Skimmerzone 25 and two more drainage zones 26.1 . 26.2 on. In this case, the first drainage zone, as seen in the direction of the wire run S (arrow), points first 26.1 of the drainage box 16 a radius of curvature in the range of 1,000 to 5,000 mm, preferably about 2,000 mm, an open area in the range of 100 to 40% and a pitch in the range of 60 mm. On the other hand, the second dewatering zone, seen in the direction of the wire run S (arrow), has the second 26.1 of the drainage box 16 a radius of curvature in the range of 3,000 to 10,000 mm, preferably of about 5,000 mm, an open area in the range of 100 to 40% and a pitch in the range of 50 mm.

Of course, the drainage box may also have only one drainage zone in a manner not shown.

The 2 to 4 show schematic side views of three further preferred embodiments of a respective sheet forming apparatus according to the invention 1 for producing a two- or multi-ply fibrous web 2 , The three embodiments shown here include those in the 1 illustrated in detail embodiment, which is now indicated only schematically. On the description of the figure 1 becomes reference taken. In the two embodiments of the 2 and 3 are the two sieves 4 . 11 with the intermediate layers 6 . 10 on pulp suspensions 3 in the twin-wire zone 12 over a roller 27 , In particular, a suction roll or a solid roll out, so that a change in the screen direction S (arrow) downwards, in particular vertically or approximately vertically downwards takes place. Subsequently, the two sieves 4 . 11 with the intermediate layers 6 . 10 on pulp suspensions 3 separated and the sieve (" 4 " in 2 , " 11 " in 3 ) with the layers lying on top 6 . 10 on pulp suspensions 3 is over a Gautschelement 28 , in particular a Gautschwalze 28.1 or a rubber shoe, wherein the two layers 6 . 10 on pulp suspensions 3 on another and another sieve 30 guided location 29 on pulp suspension 3 be aufgautscht. Depending on the sieve separation can that of the other sieve 30 guided location 29 on pulp suspension 3 opposite to the screen direction S (arrow) of the first screen 4 (see. 2 ) or in the direction S (arrow) of the first sieve 4 (see. 3 ) are moved. In this way, therefore, the production of an at least three layers of fibrous web 2 allows.

In the embodiments of the 4 be the two sieves 4 . 11 with the intermediate layers 4 . 10 on pulp suspensions 3 separated in a known manner, so that the two layers 4 . 11 on pulp suspensions 3 on the first sieve 4 be guided. In this way, therefore, the production of at least two layers of fibrous web 2 allows.

The in the 1 to 4 At least partially illustrated sheet forming devices according to the invention 1 Of course, further screening units can be used 31 include. Such a further screening unit 31 is for example in the 2 shown in dashed lines.

The in the 1 to 4 At least partially illustrated sheet forming devices according to the invention 1 are particularly suitable for use in a machine 100 for producing a two- or multi-ply fibrous web 2 , in particular cardboard or packaging paper web, of at least two pulp suspensions 3 ,

The machine 100 may also include, in a manner not shown, a DuoCentri NipcoFlex press, which in a known manner has a press nip draining only on one side and which, for example, in the documents EP 1 749 926 B1 and DE 10 2004 003 674 A1 is disclosed. The relevant content of these publications is hereby made the subject of the present description.

In summary, it should be noted that the invention provides a sheet forming apparatus of the aforementioned types, which is the production of a two- or multi-layer fibrous web using a secondary headbox at higher Siebgeschwindigkeiten and better quality properties, in particular the at least one applied to the secondary headbox layer ensured continuously and reliably.

LIST OF REFERENCE NUMBERS

1

Sheet forming device for producing a two- or multi-layer fibrous web

2

Fibrous web

3

Fibrous suspension

4

First sieve; wire

5

First headbox

6

First location

7

forming board

8th

dewatering element

9

Second headbox

10

Second location

11

Second sieve; top wire

12

twin

13

inlet gap

14

inlet roller

15

Rigid bar

15.a.

distance

15.K1

radius of curvature

15.K2

radius of curvature

15.T

afford division

16

dewatering box

17

dewatering element

17.A

Downwardly curved guide surface

17.K

radius of curvature

17.W

angle of curvature

18

turbulence generator

18.R1

line

18.R2

line

18.R3

line

18.T

grid division

19

headbox

20

lamella

21

inlet strip

21.b

last width

21.T

afford division

21.W

foil angle

22

Resilient element

22.F

Selectable force (arrow)

23

formation bar

23.T

afford division

24

Resilient element

24.F

Selectable force (arrow)

25

Skimmerzone

26.1

First drainage zone

26.2

Second drainage zone

27

roller

28

Gautschelement

28.1

couch roll

29

More location

30

Another sieve

31

screening unit

100

Machine for producing a two- or multi-layer fibrous web

B

Area

CD

Cross machine direction (arrow)

S

Sieblaufrichtung (arrow)

S.H

Initial screen direction (arrow)

S.n

Changed sieve direction (arrow)

QUOTES INCLUDE IN THE DESCRIPTION

This list of the documents listed by the applicant has been generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA assumes no liability for any errors or omissions.

Cited patent literature

• DE 9115632 U1 [0002]
• DE 4031038 A1 [0004]
• DE 19951928 A1 [0004]
• DE 10223398 A1 [0005]
• US 6190500 B1 [0006]
• EP 1749926 B1 [0052]
• DE 102004003674 A1 [0052]

Claims (15)

Sheet forming device ( 1 ) for producing a two- or multi-ply fibrous web ( 2 ), in particular a cardboard or packaging paper web, from at least two pulp suspensions ( 3 ), at least comprising a first, preferably designed as a wire screen ( 4 ), to which a first and preferably a single-layer headbox ( 5 ) a first layer ( 6 ) to pulp suspension ( 3 ) and which with the overlying layer ( 6 ) to pulp suspension ( 3 ) via a stationary screen table ( 7 ) and several drainage elements ( 8th ), a second and preferably one-layer headbox ( 9 ), on the first, on the first sieve ( 4 ) resting position ( 6 ) to pulp suspension ( 3 ) a second layer ( 10 ) to pulp suspension ( 3 ), and a second sieve, preferably designed as an upper sieve ( 11 ), which with the first sieve ( 4 ) at least partially a wedge-shaped inlet gap ( 13 ) having twin-wire zone ( 12 ), wherein in the twin-wire zone ( 12 ) via an inlet roller ( 14 ) guided second sieve ( 11 ) over a plurality of rigidly arranged and at least one radius of curvature, preferably at least two radii of curvature ( 15.K1 . 15.K2 ) descriptive strips ( 15 ) running at a mutual distance ( 15.a. ) on a drainage box ( 16 ) are arranged, characterized in that in the region (B) of the application, preferably - seen in the wire direction (S) - before the application of the second layer ( 10 ) to pulp suspension ( 3 ) on the first layer ( 6 ) to pulp suspension ( 3 ) below the first sieve ( 4 ) a first sieve ( 4 ) leading drainage element ( 17 ) is arranged, which has a downwardly curved guide surface ( 17.A ) with a bending angle ( 17.W ) of ≥ 1 °, preferably of ≥ 2 °, in particular of ≥ 3 °, and in that at least one inlet strip ( 21 ) located in the region of the wedge-shaped inlet gap ( 13 ) and / or - in the direction of wire direction (S) - after the area of the wedge-shaped inlet gap ( 13 ) arranged by means of at least one resilient element ( 22 ) and which is supported by a selectable force ( 22.F ) against the first sieve ( 4 ) and / or from the two sieves ( 4 . 11 ) with the intermediate layers ( 6 . 10 ) made sieve sandwich is pressable. Sheet forming device ( 1 ) according to claim 1, characterized in that the one downwardly curved guide surface ( 17.A ) having drainage element ( 17 ) has a preferably constant radius of curvature ( 17.K ) between 2,000 and 20,000 mm. Sheet forming device ( 1 ) according to claim 1, characterized in that the drainage element having a downwardly curved guide surface has a preferably continuously decreasing radius of curvature. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the second layer ( 10 ) to pulp suspension ( 3 ) on the first layer ( 6 ) to pulp suspension ( 3 ) applying second and preferably single-layer headbox ( 9 ) a turbulence generator ( 18 ) with a grid pitch ( 18.T ) in the cross machine direction (CD) of ≤ 30 mm. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the second layer ( 10 ) to pulp suspension ( 3 ) on the first layer ( 6 ) to pulp suspension ( 3 ) applying second and preferably single-layer headbox ( 9 ) a headbox nozzle ( 19 ), in which at least one lamella ( 20 ) is arranged. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that in the region of the wedge-shaped inlet gap ( 13 ) and / or - in the direction of wire direction (S) - after the area of the wedge-shaped inlet gap ( 13 ) at least two inlet strips ( 21 ) are arranged, each by means of at least one compliant element ( 22 ) and each with a selectable force ( 22.F ) against the first sieve ( 4 ) and / or from the two sieves ( 4 . 11 ) with the intermediate layers ( 6 . 10 ) made sieve sandwiches are pressed. Sheet forming device ( 1 ) according to claim 6, characterized in that the at least two inlet strips ( 21 ) a last width ( 21.b ) in the range from 2 to 50 mm, preferably from 5 to 30 mm, in particular from 10 to 20 mm, a splitting ( 21.T ) in the range from 50 to 200 mm, preferably from 100 to 150 mm, in particular from approximately 120 mm, and / or a foil angle ( 21.W ) in the range of +2 to -2 °, preferably from +1 to -1 °, in particular from +1 to 0 °. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the first sieve ( 4 ) in the twin-wire zone ( 12 ) over 2 to 8, preferably over 3 to 6, in particular 5 formation strips ( 23 ) running each other's rigid ledges ( 15 ) of the dewatering box ( 16 ) arranged by means of resilient elements ( 24 ) are supported and with a selectable force ( 24.F ) against the first sieve ( 4 ) and that the formation strips ( 23 ) a division of forces ( 23.T ) of 1: 1, 2: 1 or 3: 1 in relation to the division of forces ( 15.T ) on the drainage box ( 16 ) rigidly arranged strips ( 15 ) exhibit. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the on the drainage box ( 16 ) rigidly arranged strips ( 15 ) at least one radius of curvature, preferably at least two radii of curvature ( 15.K1 . 15.K2 ) having a respective radius of curvature in the range of 1,500 to 10,00 mm, preferably of 2,000 to 7,500 mm, preferably of 2,000 to 5,000 mm. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the on the drainage box ( 16 ) rigidly arranged strips ( 15 ) at least two radii of curvature ( 15.K1 . 15.K2 ) with increasing values in the screen direction (S). Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the drainage box ( 16 ) - in skimming direction (S) - a Skimmerzone ( 25 ) and at least one dewatering zone, preferably at least two dewatering zones ( 26.1 . 26.2 ), wherein the - seen in the wire direction (S) - first dewatering zone ( 26.1 ) of the dewatering box ( 16 ) has a radius of curvature in the range of 1,000 to 5,000 mm, preferably of about 2,000 mm, an open area in the range of 100 to 40% and a pitch in the range of 60 mm, and wherein the second drainage zone (seen in the wire direction (S)) ( 26.2 ) of the dewatering box ( 16 ) has a radius of curvature in the range of 3,000 to 10,000 mm, preferably about 5,000 mm, an open area in the range of 100 to 40% and a pitch in the range of 50 mm. Sheet forming device ( 1 ) according to one of the preceding claims, characterized in that the two sieves ( 4 . 11 ) with the intermediate layers ( 6 . 10 ) on pulp suspensions ( 3 ) in the twin-wire zone ( 12 ) via a roller ( 27 ), in particular a suction roll or a solid roll are guided so that a change in the wire direction (S) down, in particular vertically or approximately vertically downwards takes place. Sheet forming device ( 1 ) according to claim 12, characterized in that the two sieves ( 4 . 11 ) with the intermediate layers ( 6 . 10 ) on pulp suspensions ( 3 ) and that the sieve ( 4 ; 11 ) with the layers lying thereon ( 6 . 10 ) on pulp suspensions ( 3 ) via a rubber element ( 28 ), in particular a Gautschwalze ( 28.1 ) or a rubber shoe is guided, wherein the two layers ( 6 . 10 ) on pulp suspensions ( 3 ) on another and another sieve ( 30 ) guided location ( 29 ) to pulp suspension ( 3 ) be aufgautscht. Sheet forming device ( 1 ) according to one of claims 1 to 11, characterized in that the two sieves ( 4 . 11 ) with the intermediate layers ( 6 . 10 ) on pulp suspensions ( 3 ) and that the two layers ( 6 . 10 ) on pulp suspensions ( 3 ) on the first sieve ( 4 ). Machine ( 100 ) for producing a two- or multi-ply fibrous web ( 2 ), in particular a cardboard or packaging paper web, from at least two pulp suspensions ( 3 ), characterized in that it comprises at least one sheet forming device ( 1 ) according to one of the preceding claims.

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