EP1120490A2 - 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 former of a machine for producing a Tissue web, with two continuous endless drainage belts run together to form a material inlet gap and then guided over a forming element, in particular a forming roller are. It relates to a method according to the preamble of claim 11.

Twin-wire and crescent formers used in tissue production the fiber suspension is placed between two dewatering belts, which are guided over at least part of the circumference of a forming roller are. With twin wire formers, both drainage belts are as Drainage screens executed. In contrast, crescent formers are used as inner sieves a felt band is provided. Considered in the direction of flow the forming roller, the outer belt is guided away from the inner belt. The tissue web formed between the two drainage belts runs with the lower drainage belt with. This becomes problematic Separation process when the outer band is very rough and / or very open. This is when using a screen with zonal different Screen permeability, i.e. when using a so-called DSP sieve the case. The fibers are partly caused by the drainage flow pulled into the drainage belt where they get caught. First of all, this has the disadvantage that the tissue web is too tends to run along with the outer wire. Another disadvantage is that the fibers in the outer sieve do not hook completely during the separation process the tissue web can be removed from the rough, open outer screen, but partly remain in the outer sieve. In operation, this leads to a increasing contamination of the outer sieve and thus a loss of quality the web formed as well as runability problems in the tissue machine.

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

With regard to the former, this object is achieved in that as not a drainage sieve coming into contact with the forming element with zonal different sieve permeability is provided and that in the area of the separation point at which this outer band and the Inner band can be separated again, a suction element inside the loop of the inner band arranged and / or the forming element is provided with a suction zone.

With the help of the suction element, the tissue web can be safely removed from the outer sieve be removed. A suction box, for example, can be used as the suction element with strips and suction slots, a suction roller and / or a pipe suction device be used.

Sieves of zonal different permeability are, for example, from the SE 427 053 known. Then the relevant sieves can e.g. from a Tissues exist in the one or more levels provided Longitudinal and transverse threads according to a predefinable pattern are interwoven with each other, that systematically distributed areas are more suitable Result in size in which the number of crossing points is equal Is zero or significantly smaller than in the weave structure of the remaining fabric.

In a preferred embodiment of the former according to the invention the vacuum in the suction element can be adjusted. So that's one easy adaptation to the respective operating conditions (Basis weight, porosity of the web, speed) possible.

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

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

The suction element is advantageously designed such that it is the inner band acted on at least substantially over its entire width.

As a result, the suction element can be provided with suction openings, for example be arranged so that each point of the tissue web in the Suction area arrives before the drainage belts are separated. The suction openings can for example consist of at least one machine width Suction slot or viewed from several in the machine direction successive rows of holes offset from one another (round holes, elongated holes, etc.) exist.

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

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

According to a further aspect of the invention, in the event that at least one of the two drainage belts through a drainage sieve with different zonal permeability, i.e. a DSP sieve, is formed, such a drainage screen a conditioning device such as in particular a screen cleaning device. In order to counteracts the tendency of the DSP sieve to become dirty is due to the fact that due to the different permeability Fibers penetrate the volume of the sieve and settle. Corresponding contamination affects the performance of the sieve and thus the quality of the tissue web. These disadvantages are compounded by the Conditioning or screen cleaning device according to the invention avoided. In this case, for example, spray pipes with over the machine width arranged nozzles are used. For example, it is too a traversing "Duocleaner" (cf. EP-A-0 731 212) from 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 so that it Drainage screen at least essentially over its entire width charged away. A corresponding one across the entire width Cleaning device (e.g. spray pipes with over the machine width arranged nozzle, jet cleaner, cleaning roller, etc.) can for example in combination with a traversing, locally intensive effect Cleaning device (e.g. Duocleaner, high pressure jet) can be used. A combination of such cleaning elements can reduce strain on the sieve with a sufficiently good cleaning effect.

It is advantageous if the former in question is designed as a crescent former in which a felt band is provided as the inner band.

The method according to the invention is accordingly characterized in that that as an outer band not in contact with the forming element a drainage sieve with different zonal permeability is used that in the area of the separation point at which this outer band and the inner band are separated again, the inner band by means of a suction element arranged within its loop is sucked and / or that a forming element provided with a suction zone is used.

With the solution specified in claim 16 is in particular again counteracts the tendency of a DSP sieve to become dirty.

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

The method according to the invention is advantageously in a crescent former applicable.

For example, come as sieves of zonal different permeability Sieves of the type in question as described in PCT / GB99 / 02684. After that, the screens in question can be made in particular from one fabric exist in one or in several levels provided in one threads running in the first direction with threads running in a second direction Threads are woven together so that there is a grid, that is a multitude of systematically distributed areas of definable configurations separates from each other and determines accordingly, the systematically distributed areas each have at least three in one and at least comprises three threads running in the other direction. With the threads it can 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 below using exemplary embodiments with reference to the drawing; in this show:

Figure 1

1 shows a schematic illustration of a crescent former with a shoe press provided on the Yankee cylinder,

Figure 2

2 shows an enlarged representation of the forming area of the former shown in FIG. 1 with the suction element arranged inside the loop of the inner band and the conditioning device assigned to the outer sieve,

Figure 3

1 shows a schematic representation of a conditioning device assigned to the outer wire of the former, which comprises a roller pressed into the drainage wire with an associated scraper,

Figure 4

1 shows a schematic representation of a conditioning device which is arranged in the region of a guide roller of the outer wire and which comprises a "jet cleaner" from Voith Sulzer,

Figure 5

2 shows a schematic representation of a further embodiment with a conditioning device which is arranged in the region of a guide roller of the outer wire and which comprises a "jet cleaner" from Voith Sulzer,

Figure 6

a schematic representation of a conditioning device arranged in the region of a guide roller of the outer wire and comprising a "Duocleaner" from Voith Sulzer, and

Figure 7

a weave pattern diagram of a repeating section of a possible embodiment of a drainage sieve formed by a fabric with zonally different sieve permeability.

Figure 1 shows a schematic representation of a crescent former 10 Machine for producing a tissue web 22. There are two rotating ones Endless drainage belts 12, 14 are provided under formation a stock inlet gap 16 converge and then over a here are formed by a forming roller 18 forming element.

The fiber suspension is fed into the stock inlet gap 16 by means of a headbox 20 brought in.

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

The tissue web 22 which is formed in the process 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. Is in the tape running direction L before the extended nip 24 the inner band 12 guiding the tissue web 22 via a suction device, here a suction roller 30 out.

A drying hood 32 can be assigned to the Yankee cylinder 26.

Figure 2 shows an enlarged view of the forming area of the in the Figure 1 shown formers in which further essential details of the invention Arrangement can be seen.

Then is in the region of the separation point 34, at which the outer sieve 14 and the inner band 12 are separated again, at least one Suction element 36 arranged within the loop of the inner band 12. Alternatively or additionally, the forming roller 18 can have a suction zone 38 be provided. With such a suction-formed forming roller 18, the Nonwoven fabric is pulled onto the felt forming the inner band 12.

In the present case, the suction element 36 is in the tape running direction L. the separation point 34 arranged. The vacuum in the suction element 36 can be adjustable. The same applies to the vacuum in the suction zone 38. In addition, the suction element 36 can be designed so that it Inner band 12 at least substantially over its entire width acted upon.

In the area of the separation point 34, inside the loop of the outer wire 14 at least one blowing element 40 may be arranged. The outer screen 14 can thus be supplied with blown air from the inside, for example. This blowing element 40 is advantageously carried out so that it Outer sieve 14 at least essentially over its entire width acted upon.

A conditioning device can guide the outer screen 14, which is guided over guide rollers 42-48 50 assigned to be, which is in particular a screen cleaning device can act. This conditioning device 50 is expediently designed so that the outer sieve 14th acted on at least substantially over its entire width.

The conditioning device 50 can, for example, be a spray tube "Duocleaner" from Voith Sulzer, one in the drainage screen concerned include indented roller with scraper and / or the like.

FIG. 3 shows a schematic illustration of one concerned Drainage sieve with different zonal permeability, here For example, conditioning device assigned to the outer screen 14 50, which has a roller 52, which is pressed into the screen 14, with an associated roller Scraper 54 includes. In the tape running direction S in front of the roller 52 is on the a spray tube 56 is arranged on the same screen side as the roller. The end the sieve 14 escaping dirty water and the like. by a provided on the other side of the screen 58 included.

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

FIG. 4 shows a schematic illustration of a roller in the area of a guide roller, For example, the guide roller 42, the outer wire 14 arranged Conditioning device 50 by a "Jet Cleaner" from Voith Sulzer is formed. This conditioning device 50 comprises an inside the loop of the outer screen 14 arranged, the screen 14 acting Nozzle arrangement 60, one opposite this, on the suction device 62 provided on the other side of the screen and one in the tape running direction L arranged in front of it, which acts on the outside of the screen 14 Spray tube 64. The in the tape running direction L in front of the guide roller 42nd provided nozzle arrangement 60 is at a distance in the present case arranged by the guide roller 42.

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

FIG. 6 shows a schematic representation of one in the area of a guide roller, for example, the guide roller 42, the outer screen 14 arranged conditioning device 50 by a "Duocleaner" from Voith Sulzer is formed.

Thereafter includes in the area of a guide roller, for example the guide roller 42, provided conditioning or cleaning device 52 a formed by a rotor nozzle cleaning nozzle 68 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 in flow with one Suction line 74 connected and forms one of the cleaning nozzle 68 assigned suction space 76. The cleaning nozzle 68 is a High pressure hose 78 supplied with liquid. Accordingly, it can Sieve 14 with, for example, a rotating high-pressure water jet 80 be charged. The dirt and water suction takes place via the suction line 74.

The aforementioned parts of the conditioning device 50 are on one Traversing carriage 82 arranged transversely to the tape running direction L. The traversing carriage 82 seated on cross members 84 is not by means of a traversing motor shown driven.

Otherwise, this conditioning device 50 can be designed in this way, for example be as described in EP-A-0 731 212.

For example, come as sieves of zonal different permeability Sieves of the type in question as described in PCT / GB99 / 02684. After that, the screens in question can be made in particular from one fabric exist in one or in several levels provided in one threads running in the first direction with threads running in a second direction Threads are woven together so that there is a grid, that a multitude of systematically distributed areas of definable configuration separates from each other and determines accordingly, the systematically distributed areas each have at least three in one and at least three includes threads running in the other direction. The threads can it is in particular weft threads and warp threads.

FIG. 7 shows a weaving pattern diagram of a repetitive example Section of a possible embodiment of one by one such fabric formed drainage screen with zonal different Screen permeability. The repeating weave pattern diagram includes ten warp threads and ten in the present embodiment Weft threads. The respective lies in the area of the hatched squares Weft thread below the respective warp thread. In contrast, lies in the area the light squares the respective weft above the respective Warp thread. Depending on the circumstances, one or the other the other side of the weave pattern diagram is on the outside.

The hatched areas form a grid 86 through which one ultimately ends Plenty of systematically distributed areas 88 configurable configuration be separated from one another and defined accordingly.

Reference list

10th

Crescentformer

12th

Inner band

14

Outer band

16

Infeed gap

18th

Forming roller

20th

Headbox

22

Tissue web

24th

extended press nip

26

Yankee cylinder

28

Shoe press roll

30th

Suction roll

32

Dryer hood

34

Separation point

36

Suction element

38

Suction zone

40

Blow element

42

Guide roller

44

Guide roller

46

Guide roller

48

Guide roller

50

Conditioning device

52

roller

54

scraper

56

Spray tube

58

Facility

60

Nozzle arrangement

62

Suction device

64

Spray tube

66

Inlet gusset

68

Cleaning nozzle

70

Nozzle head

72

Suction cup

74

Suction line

76

Suction chamber

78

High pressure hose

80

High pressure water jet

82

Traversing trolley

84

Cross member

86

Grid

88

Areas

L

Belt running direction

Claims (18)

Shaper of a machine for producing a tissue web (22), with two circulating endless dewatering belts (12, 14), which converge to form a stock inlet gap (16) and are then guided over a forming element (18), in particular a forming roll,
characterized by
that a drainage sieve with zonally different sieve permeability is provided as the outer belt (14) not coming into contact with the forming element (18) and that in the region of the separation point (34) at which this outer belt (14) and the inner belt (12) are separated again , at least one suction element (36) is arranged within the loop of the inner band (12) and / or the forming element (18) is provided with a suction zone (38). Shaper according to claim 1,
characterized by
that the vacuum in the suction element (36) is adjustable. Shaper according to claim 1 or 2,
characterized by
that the suction element (36) is arranged in the tape running direction (L) in front of the separation point (34). Shaper according to one of the preceding claims,
characterized by
that the separation of the tapes (14, 12) takes place on the suction element (36). Shaper according to one of the preceding claims,
characterized by
that the suction element (36) is designed such that it acts on the inner band (12) at least substantially over its entire width. Shaper according to one of the preceding claims,
characterized by
that at least one blowing element (40) is arranged in the region of the separation point (34) within the loop of the outer band (14). Shaper according to claim 6,
characterized by
that the blowing element (40) is designed such that it acts on the outer band (14) at least substantially over its entire width. Shaper according to one of the preceding claims,
characterized by
that the forming element (18) is provided with a suction zone (38) adjustable vacuum. Shaper of a machine for producing a tissue web (22), with two continuous endless drainage belts (12, 14), which converge to form a stock inlet gap (16) and are then guided over a forming element (18), in particular a forming roller, in particular according to one of the previous claims,
characterized by
that at least one of the two drainage belts (12, 14) is formed by a drainage screen with zonal different screen permeability and a conditioning device (50), in particular a screen cleaning device, is assigned to this drainage screen. Shaper according to claim 9,
characterized by
that the conditioning device (50) is designed so that it acts on the drainage screen (14) at least substantially over its entire width. Shaper according to claim 9,
characterized by
that it is designed as a crescent former (10) in which a felt band is provided as the inner band (12). Method for producing a tissue web (22) by means of a former with two circulating endless dewatering belts (12, 14), which converge to form a stock inlet gap (16) and are then passed over a forming element (18), in particular a forming roller,
characterized by
that a drainage sieve with zonally different sieve permeability is used as the outer belt (14) not coming into contact with the forming element (18), that in the region of the separation point (34) at which this outer belt (14) and the inner belt (12) are separated again the inner band (12) is sucked by means of at least one suction element (36) arranged inside its loop and / or that a forming element (18) provided with a suction zone (38) is used. Method according to claim 12,
characterized by
that the inner belt (12) is sucked in the belt running direction (L) before the separation point (34). A method according to claim 12 or 13,
characterized by
that the inner band (12) is sucked at least substantially over its entire width. Method according to one of the preceding claims,
characterized by
that the outer band (14) is acted upon in the region of the separation point (34) by means of a blowing element (40) arranged inside the loop. A method according to claim 15,
characterized by
that the outer band (14) is acted upon by the blowing element (40) at least essentially over its entire width. Method for producing a tissue web (22) by means of a former (10) with two circulating endless dewatering belts (12, 14), which converge to form a stock inlet gap (16) and are then passed over a forming element (18), in particular a forming roller, in particular according to one of the preceding claims,
characterized by
that for at least one of the two dewatering belts (12, 14) a dewatering sieve with different zonal permeability is used and this dewatering sieve is conditioned or cleaned by means of a conditioning device (50), in particular a sieve cleaning device. Application of the method according to one of the preceding claims in a crescent former (10) in which the inner band (12) a felt band is provided.

Images