EP1382740A1 - Forming section for producing a multi-layer fibrous web - Google Patents

Abstract

A paper-making machine forms a multi-layered web and has an overhead sieve section (1). The section (1) has two endless sieve belts (7, 8) which come together in a double-sieve zone (6.1) where a fibrous suspension is introduced to the gap between the two converging sieve belts. The contact zone esp. includes a bend defined by a rotating drum (23). On passing the drum the two sieves (7, 8) and moving web change direction by pref. 30 to 150 degrees. In the process a first fibrous layer (5) is released onto a belt (4) to form a first web layer. The belt (4) is located below the double-sieve unit (1) with a forming drum (16) producing a second web (9) from a fibrous suspension. The two webs are brought together at a merging station (10, 11) by a couch roll (28).

Description

The invention relates to a wire section for producing a multilayer fibrous web, in particular a paper or cardboard web, from at least one Fibrous suspension according to the preamble of claim 1.

Such a wire section is from German published application DE 196 51 493 A1 (PB10449 DE) of the applicant known. The screen section shown includes a belt on which at least a first fiber layer runs in, a twin-wire section with a forming roller and with a first and a second Sieve (upper sieve, lower sieve), which together form a double sieve zone form, in which a second fibrous layer is produced, and a merging section with a lower vertex where the first and the second fiber layer combined to produce a multi-layer fiber web become.

This known wire section has the disadvantage that differential speeds occur between the two screens of the twin wire section in the area of the twin wire zone. Such an occurrence of differential speeds can be attributed to the low frictional connection between the two sieves in said zone and increases with increasing basis weight of the fibrous suspension or increasing height of the fibrous suspension between the two sieves.
The resulting differential speeds significantly worsen the sheet production conditions and promote screen wear on both screens, making the manufacture of a high-quality fibrous web noticeably more difficult.

It is therefore an object of the invention to provide a wire section of the type mentioned to improve such that the emergence of said differential speeds largely prevented, especially with reduced screen wear and the production of a high-quality fibrous web with good runability is made possible.

This object is achieved according to the invention in a wire section of the type mentioned at the outset in that the two screens are guided in the area of the twin wire zone over a peripheral area of at least one folding device.
This has the advantage that due to the fact that the fibrous web has already been largely or preferably completely completed, there is an intimate frictional connection between the two sieves both in the web area and in the two edge regions, and that this intimate frictional connection largely prevents the occurrence of said differential speeds. This enables the production of a high-quality fibrous web with good runability.
The arrangement of such a folding device also creates space for further devices. Such a device can be, for example, a water collection and water drainage basin, in which the white water falling down can easily be collected and discharged. This again ensures trouble-free operation of the wire section without defects in the fiber layer.

In a preferred embodiment of the invention, the buckling device is a buckling roller formed because of possible rotation due to the rotation of the roller body on the touched screen is largely avoided.

To ensure sufficient adhesion between the two sieves, According to the invention, they have a wrap angle on the buckling device on which has a value in the range from 20 ° to 180 °, preferably from 30 ° up to 150 °.

The buckling device is advantageously arranged such that the two Sieves on the common rollers and one in the twin-wire zone have the same direction of buckling.

According to the invention, the buckling device can be in the loop of the first Sieve (top sieve) as well as in that of the second sieve (bottom sieve), with an arrangement in the loop of the second sieve (top sieve) the drain point of the two screens from the forming roller in the direction of the belt or after the point of contact or in the area of the point of contact of the two screens lies on the buckling device. These types of arrangement stand out in particular by enabling a compact structure of the Twin-wire section from.

As part of achieving trouble-free operation of the wire section, it is as already mentioned, advantageous, at least one water collection and Drainage basins within the lower two quadrants of the To arrange kinking device.

With regard to the separation of the two screens, there exist in principle according to the invention three options: the separation is carried out by at least one separating suction device, the separation is carried out by a suction, preferably in some areas Merging section or the separation takes place when it expires from the Articulation. All three options are characterized by one high process reliability, which means that the fibrous web remains in place on the top sieve, with gentle treatment of the first layer of fiber produced out.

The fiber suspension can be introduced into the twin wire section in the running direction or against the direction of the belt. Both types provide the advantage of not extending the wire section, the introduction is more advantageous in the running direction from a spatial point of view.

The buckling device according to the invention is in the first embodiment as a full roll formed with a preferably smooth surface, in a second and third embodiment the buckling device can also have a grooved and / or drilled surface have or be formed as a forming or suction roll. Any execution the buckling device has characteristic features and is suitable thereby each for a special application.

The merging section is preferably formed by a rubber roller, since the merging of the first and second layers of fibrous material can be achieved by means of a rubber roller can be easily and structurally solved.

It is also advantageous with regard to design and economic aspects if the twin-wire section has a forming roller which, according to the invention, advantageously has a diameter of more than 1,200 mm, preferably more than 1,635 mm, in particular more than 1,760 mm. This forming roller is ideally designed as an open roller and opened up by means of a grill or honeycomb structure and / or it is a suction roller.
The above-mentioned elements are largely known and tested and therefore have increased functional reliability and low acquisition costs, and possibly also low operating costs.

With regard to a low height of the wire section on the one hand and on the other hand a minimum number of components in the wire section, it is advantageous if the Forming roller has a drainage capacity that has a value of at least 50%, preferably at least 65%, of the total drainage capacity has the twin-wire section. The components can then be used for the remaining drainage together with the associated construction height in terms of quantity and constructively smaller than usual.

In the context of optimal operation of the wire section, it is also advantageous if at least one of the rollers is driven by at least one drive device is. This enables an optimal drive concept for the wire section realize.

According to a further preferred embodiment of the invention, the twin-wire section is placed on the belt as a unit. By this measure can the twin wire section of the wire section according to the invention for retrofitting from existing screen sections.

The wire section according to the invention is suitable on the basis of those described above Excellent properties also for use with a Sieve section rebuild, as there are usually existing structural conditions, for example hall dimensions, must be taken into account and thereby the screen section conversion should not require any additional space, for example due to an increased height of the screen section to be installed.

It is understood that the present invention is not only in the manufacture of two-layer fibrous webs, but also in the case of three or more layers Fiber webs can be used.

It is further understood that the above and below still apply explanatory features of the invention not only in the specified combination, but can also be used in other combinations or alone are without departing from the scope of the invention.

Further features and advantages of the invention emerge from the subclaims and the description below Exemplary embodiments with reference to the drawing.

Figuren 1 bis 6:

verschiedene schematische Seitenansichten von erfindungsgemäßen Siebpartien.

Show it

Figures 1 to 6:

different schematic side views of screen sections according to the invention.

The screen section 1 shown for producing a multi-layer fibrous web 2, in particular a paper or cardboard web, from at least one fiber suspension 3.1, 3.2, comprises a belt 4 on which at least a first layer of fibrous material 5 arrives, a twin wire section 6 with a first and a second Sieve (upper sieve, lower sieve) 7, 8, in which a second fiber layer 9 is produced and a merging section 10 having a lower vertex 11, in which the first and the second fiber layer 5, 9 producing a multilayer fibrous web 2 are merged. Under the term In the context of this description, "tape" is generally the covering of a Understood paper or board machine, for example a sieve.

It is a headbox 12, not shown, for applying at least one fiber suspension 3.1, which is used to produce the first fiber layer 5 is provided on the tape 4. The tape 4 is after application of the Fibrous suspension 3.1 over several schematically indicated forming and Drainage elements 13 guided, with at least one other Headbox at least one additional layer of fiber suspension for formation at least one further fiber layer is applied to the first fiber layer 5 can be.

The twin wire section 6 has a first wire (top wire) 7 and a second wire (bottom wire) 8, which are guided in parallel in a twin wire zone 6.1 for forming the second fiber layer 9. In the area in which they are brought together for parallel guidance, the two screens 7, 8 form an inlet gap 14. At the inlet gap 14, a headbox 15, which is only indicated schematically, is provided, by means of which at least one fibrous suspension 3.2 for the second fibrous layer 9 enters the inlet gap 14 is shot in the running direction L (arrow) of the band 4. Because of this type of headbox 15, the twin-wire section 6 is a so-called "gap former".
The two headboxes 12, 15 can also be equipped as multi-layer headboxes and / or as headboxes with sectionally controllable dilution water technology (system "ModuleJet" - DE 40 19 593 A1 (PA04598 DE) of the applicant).

In the area of the inlet gap 15 is on the second formed as a lower wire Screen 8 is a preferably driven forming roller 16 and on the top screen trained first screen 7, a screen guide roller 17 is provided.

The forming roller 16 has a suction area 18 which extends over the circumference the forming roller 16 approximately from the area of the entry nip 14 to approximately the point extends, on which the two forming rollers 16 wrapping sieves 7, 8 of the forming roller 16 are removed. The sieves 7, 8 run in an upper one Section of the forming roller 16 between this and the opposite Wire guide roller 17 together and loop around the forming roller at an angle, which is less than 120 °, preferably less than 90 °.

A dewatering section 19 immediately adjoins the forming roller 16 in the form of a so-called D-part. The D part 19 points in the area of the first Siebs (top sieve) 7 a schematically indicated suction box 20 with a Row of fixed strips. The suction box 20 is a combined one Vacuum cleaner designed. The forming strips of the suction box 20 preferably form a slightly convex tread in the running direction of the sieves 7, 8.

The first sieve (top sieve) 7 with the shaped second fiber layer 9 is from Discharge area of the D part 19 into a merging section 10 with a lower vertex 11, in which the first and second fiber layers 5, 9 are brought together to produce a multilayer fibrous web 2, guided.

It is now provided that the two screens 7, 8 in the area of Twin wire zone 6.1 over a peripheral area 22 at least one Articulation device 21 are guided. The buckling device 21 is preferred formed as a preferably driven kink roller 23, but it can in not shown, also as an articulated shoe, articulated beam or the like be executed. Furthermore, the direction of kinking of the two screens 7, 8 is at the Rolls 16, 23 and in the twin wire zone 6.1 in the same direction.

The two screens 7, 8 have a wrap angle α on the buckling device 21, which has a value in the range from 20 ° to 180 °, preferably from 30 ° up to 150 °.

There is also a water collection and drainage basin 31 within the lower one two quadrants of the buckling device 21 arranged so that the down falling white water can be easily collected and discharged. Such a thing Basin 31 can in all of the embodiments shown in the figures sieve section 1 according to the invention may be present.

In Figure 1, the kinking device 21 is arranged in the loop of the top wire 7 and the outlet point 24 of the two screens 7, 8 from the forming roller 16 lies in Direction of travel L (arrow) of the belt 4 in front of the run-up point 25 of the two screens 7, 8 on the buckling device 21.

Furthermore, the buckling device 21 of FIG. 1 is preferably a solid roller with a smooth surface. However, it can also be a grooved and / or have drilled surface or it can even as a forming or suction roll be trained.

After passing the buckling device 21 through the two screens 7, 8 and fibrous web 9 introduced between them is separated by a Vacuum cleaner 26 of a known type, the second fibrous web 9 on the first Sieve (top sieve) 7 remains. The second sieve (lower sieve) 8 is over one or several guide rollers 27 led back to the forming roller 16.

The first sieve (top sieve) 7 and the second fibrous web 9 are then guided into the merging section 10, in which the first and second fibrous layers 5, 9 are brought together to produce a multilayer fibrous web 2. The first screen (top screen) 7 is then guided back to the screen guide roller 17 via a plurality of guide rollers 27. The merging section 10 is formed by a preferably known and possibly driven rubber roller 28, which can be closed or open or open and vacuumed.
In a further, but not shown embodiment, the merging section 10 can also be designed as a rubber press according to the applicant's unpublished German patent application DE 101 01 549.6 (PB11190 DE). The content of this patent application is hereby made the subject of the present description.

In addition, there is a separating suction device in FIG. 1 after the merging cut 10 26 for the safe separation of the now multi-layer fibrous web 2 from the first Sieve (top sieve) 7 arranged in the loop of the belt 4.

Furthermore, the forming roller 16 has a diameter D greater than 1,200 mm, preferably greater than 1,635 mm, in particular greater than 1,760 mm, and is as a suction roll formed; however, it can also be designed as an open roller be, the open roller in turn by means of a grill or Honeycomb structure can be unlocked.

Moreover, the forming roller 16 has a drainage capacity that one Value of at least 50%, preferably at least 65%, of the total drainage capacity of the twin wire former 6.

In principle, FIGS. 2 to 6 show one that is shown in FIG. 1 and is sufficient described sieve section 1 in slightly different configurations. Consequently with regard to their general descriptions, reference is made to that of FIG.

In the embodiment of FIG. 2, it is provided that the drain point 24 of the two Sieves 7, 8 from the forming roller 16 before the point of impact 25 thereof or in Area of the run-up point 25 of the same on the buckling device 21 in the form of a Buckling roller 23 lies. However, it is preferably in the loop of the second Siebs (bottom sieve) 8 a further deflection element 30 between the dewatering section (D-part) 19 and the buckling device 21. Farther the two screens 7, 8 are separated from the kinking device as they run 21 due to different outlet angles for the screens 7, 8.

FIG. 3 shows the twin-wire section 6 of the wire section 1 according to the invention, the buckling device 21 being arranged in the form of a buckling roller 23 in the loop of the second wire (bottom wire) 8. After passing through the buckling device 21 through the two screens 7, 8 and the second fibrous layer 9 inserted between them, their separation takes place in a manner similar to the embodiment in FIG.
Such an arrangement of the buckling roller 23 ensures that the top wire 7 always travels a longer distance in the twin wire area compared to the bottom wire 8 due to the bottom wire thickness, suspension or fiber layer. As a result, acceleration and braking effects of the two screens 7, 8 are largely avoided.

Also in the twin wire section 6 of the wire section 1 according to the invention from FIG. 4 is the buckling device 21 in the form of a buckling roller 23 in the loop of the second Siebs (lower sieve) 8 arranged. In addition, the two are separated Sieves 7, 8 through a preferably partially suctioned merging section 10. This is preferably a rubber roller 28 with controllable vacuumed areas 29 formed.

FIG. 5 shows a further embodiment of the wire section 1 according to the invention. Here, the buckling device 21 in the form of a buckling roller 23 is again in the Loop of the second sieve (lower sieve) 8 arranged and the separation of the two sieves 7, 8 and the second fibrous layer 9 inserted between them is carried out by a vacuum cleaner 26 of known type, the second Fiber layer 9 remains on the first sieve (top sieve) 7. The wire section 1 of the figure 5 is also characterized by the shape of its sieves 7, 8 comparatively low overall height.

The design of the wire section 1 according to the invention from FIG. 6 is due to the introduction the fiber suspension 3.2 in the twin-wire section 6 against the Direction of travel L (arrow) of band 4 marked. Other features of this Configuration have already been made in the context of the description of the figures 1 to 5 described.

The twin wire section 6 of the wire section 1 according to the invention can be advantageous Be placed on the belt 4 as a unit. This makes it suitable their use in particular in a screen section conversion.

In summary, it should be noted that a screen section of the invention initially mentioned type is created, the emergence of said differential speeds largely with reduced screen wear prevented and the production of a high quality fibrous web good runability.

LIST OF REFERENCE NUMBERS

1

Wire section

2

Multi-layer fibrous web

3.1, 3.2

Fibrous suspension

4

tape

5

First layer of fibers

6

Double-screen

6.1

twin

7

First sieve (top sieve)

8th

Second sieve (bottom sieve)

9

Second layer of fiber

10

Merging section

11

Lower vertex

12.15

headbox

13

Forming and drainage elements

14

entrance slit

16

forming roll

17

wire guide roll

18

suction area

19

Drainage section (D part)

20

suction box

21

Articulation

22

peripheral region

23

buckling roller

24

the end point

25

accumulating point

26

suction separator

27

guide roll

28

couch roll

29

Area

30

deflecting

31

Water collection and drainage basins

D

diameter

L

Running direction (arrow)

α

Wrap angle

Claims (23)

Sieve section (1) for producing a multilayer fibrous web (2), in particular a paper or cardboard web, from at least one fibrous suspension (3.1, 3.2), with a belt (4) on which at least a first fiber layer (5) runs in, with a twin wire section (6) with a forming roller () and with a first and a second wire (top wire, bottom wire) (7, 8), which together form sections of a twin wire zone (6.1) in which a second layer of fibrous material (9) is produced , and with a merging section (10) with a lower apex (11), in which the first and the second fiber layer (5, 9) are brought together to produce a multi-layer fiber web (2), characterized in that the two screens (7, 8) are guided in the area of the twin-wire zone (6.1) over a circumferential area (22) of at least one kinking device (21). Sieve section (1) according to claim 1,
characterized in that the buckling device (21) is designed as a buckling roller (23). Sieve section (1) according to claim 1 or 2,
characterized in that the two screens (7, 8) have a wrap angle (α) on the kinking device (21) which assumes a value in the range from 20 ° to 180 °, preferably from 30 ° to 150 °. Sieve section (1) according to one of the preceding claims,
characterized in that the kinking device (21) is arranged in such a way that the two screens (7, 8) on the rollers (16, 23) and in the twin-wire zone (6.1) have the same direction of kinking. Sieve section (1) according to one of the preceding claims,
characterized in that the kinking device (21) is arranged in the loop of the first sieve (top sieve) (7). Sieve section (1) according to claim 5,
characterized in that the discharge point (24) of the two screens (7, 8) from the forming roller (16) in the running direction (L) of the belt (4) before or after the point of impact (25) or in the region of the point of impact (25) two sieves (7, 8) on the folding device (21). Sieve section (1) according to one of claims 1 to 4,
characterized in that the kinking device (21) is arranged in the loop of the second sieve (lower sieve) (8). Sieve section (1) according to one of the preceding claims,
characterized in that at least one water collection and drainage basin (31) is arranged within the lower two quadrants of the buckling device (21). Sieve section (1) according to one of the preceding claims,
characterized in that the separation of the two screens (7, 8) is carried out by at least one separating suction device (26) preferably arranged after the kinking device (21). Sieve section (1) according to one of claims 1 to 8,
characterized in that the separation of the two screens (7, 8) takes place by means of a merge section (10) which is preferably vacuumed in some areas. Sieve section (1) according to one of claims 1 to 8,
characterized in that the separation of the two screens (7, 8) takes place at the end of the buckling device (21). Sieve section (1) according to one of the preceding claims,
characterized in that the fiber suspension (3.2) is introduced into the twin-wire section (6) in the running direction (L) of the belt (4). Sieve section (1) according to one of claims 1 to 11,
characterized in that the fiber suspension (3.2) is introduced into the twin-wire section (6) against the running direction (L) of the belt (4). Sieve section (1) according to one of the preceding claims,
characterized in that the buckling device (21) is designed as a solid roller with a preferably smooth surface. Sieve section (1) according to one of claims 1 to 13,
characterized in that the buckling device (21) has a grooved and / or drilled surface. Sieve section (1) according to one of claims 1 to 13,
characterized in that the buckling device (21) is designed as a forming or suction roll. Sieve section (1) according to one of the preceding claims,
characterized in that the merging section (10) is formed by a rubber roller (28). Sieve section (1) according to one of the preceding claims,
characterized in that the forming roller (16) has a diameter (D) of greater than 1,200 mm, preferably greater than 1,635 mm, in particular greater than 1,760 m. Sieve section (1) according to one of the preceding claims,
characterized in that the forming roller (16) is vacuumed. Sieve section (1) according to one of the preceding claims,
characterized in that the forming roller (16) has a dewatering capacity which has a value of at least 50%, preferably at least 65%, of the total dewatering capacity of the twin-wire section (6). Sieve section (1) according to one of the preceding claims,
characterized in that at least one of the rollers (16, 23, 28) is driven by at least one drive device. Sieve section (1) according to one of the preceding claims,
characterized in that the twin-wire section (6) is placed on the belt (4) as a unit. Use of the wire section (1) according to one of the preceding claims, especially when converting a wire section.

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