EP1120490B1 - Former and method for manufacturing a tissue web - Google Patents

Abstract

At the fourdrinier section of a papermaking machine to produce a web of tissue paper, where water is extracted from the pulp to form a wet web, the outer fourdrinier (14) which is not in contact with the web-forming roller (18) has zones with different mesh permeability. At least one suction unit (36) is within the loop of the inner fourdrinier (12), at the separation point (34) where the outer (14) and inner (12) fourdriniers are separated again and/or the web-forming roller (18) has a suction zone (38). The suction unit (36) operates with an adjustable vacuum. It is located in front of the separation point (34), in the direction (L) of web travel, or the fourdriniers separate on the suction unit (36). The structure of the suction unit (36) takes the inner fourdrinier (12) over it so that suction is applied over its whole width. At least one blower unit (40) is within the loop of the outer fourdrinier (14), at the separation point (34), to give a blowing action over the whole width of the outer fourdrinier (14). The web-forming roller (18) has a suction zone (38) working with an adjustable vacuum. At least one fourdrinier (12,14) has zones of different permeability, and a cleaner (50) acts on this fourdrinier across its whole width. The web-formation zone is a crescent system (10), using a blanket as the inner belt (12).

Description

The invention relates to a Crescentformer for a machine for producing a Tissuebahn according to the preamble of claim 1. It further relates to a method according to the preamble of claim 11.

Tissue manufacturing twin-wire formers and crescent formers the fiber suspension is placed between two dewatering belts, which passed over at least part of the circumference of a forming roll are. In twin-wire formers both drainage tapes are considered Drainage screens executed. In contrast, in Crescentformern as Innensieb provided a felt tape. Looking in the direction of flow after the forming roller, the outer belt is led away from the inner band. The Tissuebahn formed between the two Entwässerungsbändem runs with the lower drainage band with. This is problematic Separation process when the outer band is very rough and / or very open. This is different when using a sieve with zonal Sieve permeability, i. when using a so-called DSP screen the case. The fibers are partly due to the drainage flow drawn into the drainage tape where they get caught. This initially brings with it the disadvantage that the tissue web to tends to run with the outer screen. Another disadvantage is that the In the outer sieve, fibers do not fully entangle with the tissue web during the separation process be removed from the rough, open Aussensieb, but partly in the outer sieve remain. In operation, this leads to an increasing contamination of the outer sieve and thus to quality losses of the formed course as well as to runability problems in the Tissue machine.

From WO 96/35018 is a crescent former with a forming fabric with zonal different Siebdurchlässigkeit known. In such a shaper consist already described above disadvantages of the poor lifting of the tissue web from Forming screen during the separation process.

US 5,397,437 describes a twin-wire former, i. a former with two Forming screens between which a tissue web is formed, in which the lifting of the Tissuebahn from the outer forming fabric by suction of the inner forming fabric is supported.

DE 43 27 601 C describes a forming fabric associated Conditioning device.

The aim of the invention is to provide a former and a method of the type mentioned create a reliable and safe operation of a tissue machine with a Ensure DSP sieve in the initial drainage area.

This object is solved by the features of the characterizing part of claim 1.

With the aid of the suction element, the tissue web can be safely removed from the outer sieve become. As a suction, for example, a suction box with strips and Suction slots, a suction roll and / or a pipe suction can be used.

Sieves zonal different permeability are for example from the SE 427 053 known. Thereafter, the screens in question may e.g. consist of a fabric in which provided in one or more levels Longitudinal and transverse threads according to a predeterminable pattern interwoven, that systematically distributed areas more suitable Showing size in which the number of intersections equal Zero or significantly smaller than in the weave structure of the remaining fabric.

In a preferred embodiment of the former according to the invention is the existing vacuum in the vacuum element adjustable. This is one easy adaptation to the respective operating conditions (Basis weight, porosity of the web, speed) possible.

The suction element is in the direction of tape expediently before Separation point arranged.

The separation of the two bands, for example, on the suction element respectively.

Advantageously, the suction element is designed so that it is the inner band acted upon at least substantially over its entire width.

As a result, the suction element may for example be provided with suction openings which are arranged so that each point of the tissue web in the Suction area passes before the drainage tapes are separated. The suction openings may for example consist of at least one machine width Suction slot or viewed from several in the machine direction one behind the other, staggered rows of holes (round holes, long holes, etc.) exist.

To improve or support the separation effect of the suction element may be in the area of the separation point within the loop of the outer band a blowing element can be arranged. This blowing element is expediently designed so that it at least in the outer band essentially applied over its entire width. As blowing medium For example, water or preferably air may be provided.

If a forming element provided with a suction zone is provided, then preferably the vacuum in question adjustable again. By the adjustable Vacuum can be the contact intensity between the tissue web and change the inner band and adjust. By a higher vacuum For example, the adhesion of the web to the outer band is reduced and increased on the inner band, whereby the separation improved accordingly becomes.

According to another aspect of the invention is the dewatering with zonal different screen permeability, i. the DSP sieve, a conditioning device as assigned in particular a sieve cleaning device. In order to the pollution tendency of the DSP screen is counteracted due to the fact that due to the different permeability Fibers penetrate into the volume of the sieve and solidify. A corresponding contamination affects the performance of the screen and thus the quality of the tissue web. These disadvantages are caused by the Inventive conditioning or sieve cleaning device avoided. In this case, for example, spray tubes with over the machine width arranged nozzles are used. It is, for example a traversing "Duocleaner" (see EP-A-0 731 212) of Voith Sulzer with rotating high pressure nozzles and integrated suction or a "Jet Cleaner" from Voith Sulzer can be used.

The conditioning device is preferably designed to handle the Entwässerungssieb at least substantially over its entire width acted upon. A corresponding over the entire width acting Cleaning device (e.g., spray tubes with across the machine width arranged nozzle, jet cleaner, cleaning roller, etc.), for example in combination with a traversing, locally intensive effect Cleaning device (e.g., Duocleaner, high-pressure jet) are used. By a combination of such cleaning elements, the Siebbeschspruchung be minimized with sufficiently good cleaning effect.

The inventive method is characterized by the features of the characterizing part of claim 11.

Advantageous embodiments of the method according to the invention are specified in the dependent claims.

As sieves zonal different permeability come for example Sieves of the type in question, as described in PCT / GB99 / 02684 (WO-A-0 012 817) are described. Thereafter, the sieves in question, in particular from a tissue exist in the one or more levels envisaged in one first direction extending threads extending in a second direction Threads are interwoven to form a grid, a multitude of systematically distributed areas of predefinable configurations separates and determines accordingly, taking the systematic distributed areas each at least three in one and at least includes three extending in the other direction threads. At the threads these may in particular be weft threads and warp threads.

Figur 1

eine schematische Darstellung eines Crescentformers mit am Yankee-Zylinder vorgesehener Schuhpresse,

Figur 2

eine vergrößerte Darstellung des Formierbereichs des in der Figur 1 gezeigten Formers mit innerhalb der Schlaufe des Innenbandes angeordnetem Saugelement und dem Außensieb zugeordneter Konditioniereinrichtung,

Figur 3

eine schematische Darstellung einer dem Außensieb des Formers zugeordneten Konditioniereinrichtung, die eine in das Entwässerungssieb eingedrückte Walze mit zugeordnetem Schaber umfaßt,

Figur 4

eine schematische Darstellung einer im Bereich einer Leitwalze des Außensiebes angeordneten Konditioniereinrichtung, die einen "Jet Cleaner" der Firma Voith Sulzer umfaßt,

Figur 5

eine schematische Darstellung einer weiteren Ausführungsform mit einer im Bereich einer Leitwalze des Außensiebes angeordneten Konditioniereinrichtung, die einen "Jet Cleaner" der Firma Voith Sulzer umfaßt,

Figur 6

eine schematische Darstellung einer im Bereich einer Leitwalze des Außensiebes angeordneten Konditioniereinrichtung, die einen "Duocleaner" der Firma Voith Sulzer umfaßt, und

Figur 7

ein Webmusterdiagramm eines sich wiederholenden Abschnitts einer möglichen Ausführungsform eines durch ein Gewebe gebildeten Entwässerungssiebes mit zonal unterschiedlicher Siebdurchlässigkeit.

The invention is explained in more detail below with reference to embodiments with reference to the drawing; in this show:

FIG. 1

a schematic representation of a Crescentformers provided with Yankee cylinder shoe press,

FIG. 2

1 is an enlarged view of the forming region of the former shown in FIG. 1 with a suction element arranged inside the loop of the inner band and a conditioning device associated with the outer screen;

FIG. 3

a schematic representation of the outer screen of the former associated conditioning, which includes a depressed in the dewatering screen roller with associated scraper,

FIG. 4

a schematic representation of a arranged in the region of a guide roller of the outer screen conditioning, which includes a "Jet Cleaner" Voith Sulzer,

FIG. 5

3 a schematic representation of a further embodiment with a conditioning device arranged in the region of a guide roller of the outer screen, which comprises a "Jet Cleaner" from Voith Sulzer,

FIG. 6

a schematic representation of a arranged in the region of a guide roller of the outer screen conditioning, which includes a "Duocleaner" Voith Sulzer, and

FIG. 7

a weave pattern diagram of a repeating portion of a possible embodiment of a fabric formed by a dewatering screen with zonal different Siebdurchlässigkeit.

Figure 1 shows a schematic representation of a Crescentformer 10 a Machine for producing a tissue web 22. There are two circumferential endless drainage tapes 12, 14 provided under formation a Stoffeinlaufspaltes 16 converge and then on a here formed by a forming roller 18 forming element are performed.

In the stock intake gap 16 by means of a headbox 20, the pulp suspension brought in.

As is not in contact with the forming roller 18 in contact outer band 14 a dewatering screen with zonal different screen permeability, i.e. provided a so-called DSP sieve. The inner band is present Embodiment provided as a felt belt.

The resulting tissue web 22 is connected to the forming roller 18 together with the inner band 12 an extended press nip 24 fed between a tissue drying cylinder or Yankee cylinder 26 and a shoe press unit, here a shoe press roll 28, is formed. In the tape running direction L before the extended press nip 24 the tissue web 22 leading inner band 12 via an evacuated device, here a suction roll 30, guided.

The Yankee cylinder 26 may be associated with a drying hood 32.

FIG. 2 shows an enlarged view of the forming region of FIG Figure 1 shaper shown in the further essential details of the invention Arrangement can be seen.

Thereafter, in the region of the separation point 34, at which the outer screen 14 and the inner band 12 are separated from each other again, at least one Suction element 36 is disposed within the loop of the inner band 12. Alternatively or additionally, the forming roller 18 with a suction zone 38 be provided. With such a suctioned forming roller 18 is the Nonwoven fabric pulled on the inner band 12 forming felt.

The suction element 36 is present in the present case in the tape running direction L. the separation point 34 is arranged. The vacuum present in the suction element 36 can be adjustable. The same applies to the vacuum of the suction zone 38. Moreover, the suction member 36 may be configured to hold the Inner band 12 at least substantially over its entire width applied.

In the region of the separation point 34 can within the loop of the outer screen 14 at least one blowing element 40 may be arranged. The outer sieve 14 Thus, for example, can be acted upon with blowing air from the inside. This blowing element 40 is suitably designed so that it Aussensieb 14 at least substantially over its entire width applied.

The outer screen 14 guided over guide rollers 42 - 48 can be a conditioning device 50 be associated with the, which is in particular at a sieve cleaning device can act. This conditioning device 50 is suitably designed so that it the outer sieve 14th acted upon at least substantially over its entire width.

The conditioning device 50 may, for example, a spray tube, a "Duocleaner" from Voith Sulzer, one in the relevant drainage sieve indented roller with scraper and / or the like.

FIG. 3 shows a schematic representation of a respective one Drainage sieve with zonal different sieve permeability, here for example, the outer sieve 14, associated conditioning 50, an indented in the sieve 14 roller 52 with associated Scraper 54 includes. In the tape running direction S in front of the roller 52 is on the same screen side as the roller a spray tube 56 arranged. The end the sieve 14 leaking wastewater and the like is replaced by a received on the other side screen device 58 added.

In the embodiment shown in Figure 2, the conditioning is 50 disposed between the two guide rollers 42 and 48. However, it can also in the range of a guide roller, for example in the area the guide roller 42, be provided (see Figures 4 to 6).

FIG. 4 shows a schematic representation of one in the region of a guide roller, For example, the guide roller 42, the Aussensiebes 14 arranged Conditioning device 50, which by a "Jet Cleaner" the company Voith Sulzer is formed. This conditioning device 50 includes an inside arranged the loop of Aussensiebes 14, the sieve 14 acting Nozzle assembly 60, one of these opposite, on the another screen side provided suction device 62 and in the strip running direction L arranged upstream, the outside of the screen 14 beaufschlagendes Spray tube 64. In the direction of belt L before the guide roller 42nd provided nozzle assembly 60 is in the present case at a distance arranged by the guide roller 42.

FIG. 5 shows an arrangement comparable to the embodiment according to FIG. 4, however, the nozzle assembly 60 is in the between the outer screen 13 and the guide roller 42 formed Einlaufzwickel 66 is arranged. Moreover, in the present case, the wrap angle over which the Guide roller 42 is wrapped by the outer sieve 16, larger than in the Figure 4 shown arrangement. Otherwise, the conditioning device comprises 50 again the same parts as those according to Figure 4, wherein each other corresponding elements are assigned the same reference numerals.

FIG. 6 shows, in a schematic representation, one in the region of a guide roller, For example, the guide roller 42, the Aussensiebes 14 arranged conditioning 50, by a "Duocleaner" of the company Voith Sulzer is formed.

Thereafter, this includes in the region of a guide roller, for example, the guide roller 42, provided conditioning or cleaning device 52 a a cleaning nozzle 68 formed by a rotor nozzle with a rotatable Nozzle head 70, which has a nozzle arrangement, not shown. A cylindrical suction cup 72 surrounds the cleaning nozzle 68 and the Nozzle head 70. The interior of the suction bell 72 is fluidly with a Suction line 74 is connected and forms one of the cleaning nozzle 68th associated suction chamber 76. The cleaning nozzle 68 is connected via a High pressure hose 78 supplied with fluid. Accordingly, that can Sieve 14 with a rotating high-pressure water jet 80, for example be charged. The dirt and water extraction takes place over the suction line 74.

The aforementioned parts of the conditioning device 50 are at a Traversierwagen 82 arranged transversely to the direction of tape L displaced. The sitting on cross members 84 Traversierwagen 82 is not by means of a driven traversing motor drivable.

Incidentally, this conditioning device 50 can be executed, for example be as described in EP-A-0 731 212.

As sieves zonal different permeability come for example Sieves of the type in question, as described in PCT / GB99 / 02684 (WO-A-0 012 817) are described. Thereafter, the sieves in question, in particular from a tissue exist in the one or more levels envisaged in one first direction extending threads extending in a second direction Threads are interwoven to form a grid, a multitude of systematically distributed areas of specifiable configuration separates and determines accordingly, taking the systematic distributed areas each have at least three in one and at least three in the other direction extending threads comprises. At the threads can these are in particular wefts and warp threads.

FIG. 7 purely by way of example shows a weave pattern diagram of a repetitive one Section of a possible embodiment of a through such fabric formed drainage sieve with zonal different Wire permeability. The repeating weave pattern diagram in the present embodiment comprises ten warp threads and ten Wefts. In the area of the hatched squares is the respective Weft below the respective warp thread. In contrast, lies in the area the bright squares of each weft above the respective Warp. Depending on the circumstances, one or the other the other side of the weave pattern diagram are outside.

The hatched areas form a grid 86, through which finally a Variety of systematically distributed areas 88 specifiable configuration separated and determined accordingly.

LIST OF REFERENCE NUMBERS

10

crescent

12

sweatband

14

outer band

16

Stock inlet gap

18

forming roll

20

headbox

22

tissue web

24

extended press nip

26

Yankee cylinder

28

shoe press

30

suction roll

32

Trockenhaube

34

separation point

36

suction

38

suction zone

40

blowing element

42

guide roll

44

guide roll

46

guide roll

48

guide roll

50

conditioning device

52

roller

54

scraper

56

spray wand

58

Facility

60

nozzle assembly

62

suction

64

spray wand

66

inlet pocket

68

cleaning nozzle

70

nozzle head

72

suction cup

74

suction

76

suction

78

High pressure hose

80

High pressure water jet

82

traverse trolley

84

crossbeam

86

grid

88

areas

L

Tape direction

Claims (16)

1. Crescent former (10) for a machine for manufacturing a tissue web (22), having an endless felt as an inner belt (12) and having an endless dewatering fabric (14) with a zonally different fabric permeability, which run together, forming a stock inlet (16) and are then led over a forming element (18) such as, in particular, a forming roll, the dewatering fabric (14) forming the outer belt (14), which does not come into contact with the forming element (18), characterized in that, in the region of the separation point (34) at which the outer belt (14) and the inner belt (12) are separated from each other again, at least one suction element (36) is arranged within the loop of the inner belt (12) and/or the forming element (18) is provided with a suction zone (38).
2. Former according to Claim 1, characterized in that the vacuum in the suction element (36) can be adjusted.
3. Former according to Claim 1 or 2, characterized in that the suction element (36) is arranged upstream of the separation point (34) in the belt running direction (L).
4. Former according to one of the preceding claims, characterized in that the belts (14, 12) are separated on the suction element (36).
5. Former according to one of the preceding claims, characterized in that the suction element (36) is designed in such a way that it acts on the inner belt (12) at least substantially over the entire width of the latter.
6. Former according to one of the preceding claims, characterized in that at least one blower element (40) is arranged within the loop of the outer belt (14) in the region of the separation point (34).
7. Former according to Claim 6, characterized in that the blower element (40) is designed in such a way that it acts on the outer belt (14) at least substantially over the entire width of the latter.
8. Former according to one of the preceding claims, characterized in that the forming element (18) is provided with a suction zone (38) of adjustable vacuum.
9. Former according to one of the preceding claims, characterized in that at least the felt or the dewatering fabric (14) is assigned a conditioning device (50), such as in particular a fabric cleaning device.
10. Former according to Claim 9, characterized in that the conditioning device (50) is designed in such a way that it acts on the dewatering fabric (14) at least substantially over the entire width of the latter.
11. Method for manufacturing a tissue web (22) by means of a crescent former having an endless felt as an inner belt (12) and an endless dewatering fabric (14) with a zonally different fabric permeability, which run together, forming a stock inlet (16) and are then led over a forming element (18) such as, in particular, a forming roll, the dewatering fabric forming the outer belt, which does not come into contact with the forming element (18), characterized in that, in the region of the separation point (34) at which the outer belt (14) and the inner belt (12) are separated from each other again, the inner belt (12) has a vacuum applied to it by means of at least one suction element (36) arranged within its loop and/or in that use is made of a forming element (18) provided with a suction zone (38).
12. Method according to Claim 11, characterized in that the inner belt (12) has a vacuum applied to it upstream of the separation point (34) in the belt running direction (L).
13. Method according to Claim 11 or 12, characterized in that the inner belt (12) has a vacuum applied to it at least substantially over its entire width.
14. Method according to one of the preceding Claims 11 to 13, characterized in that, in the region of the separation point (34), the outer belt (14) is acted on by means of a blower element (40) arranged within its loop.
15. Method according to Claim 14, characterized in that the outer belt (14) is acted on by means of the blower element (40) at least substantially over its entire width.
16. Method according to one of the preceding Claims 11 to 15, characterized in that the dewatering fabric (14) is conditioned or cleaned by means of a conditioning device (50) such as, in particular, a fabric cleaning device.

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