EP1398412B1 - Twin wire former for producing a fibrous web - Google Patents

Abstract

In a papermaking process a fibrous suspension is sandwiched between outer (5) and inner (4) moving de-watering sieve belts (4, 5), as they progress back-to back from a first drum (13) to a second forming drum (7). At a point approx. mid-way between the two drums, the belts are tangentially deflected towards the inner belt (4). The tangential deflection is effected by a wiper blade (16). Also claimed is a commensurate papermaking process

Description

The invention relates to a twin-wire former for producing a fibrous web, according to the preamble of claim 1.

Such a twin-wire former is for example from the German Offenlegungsschrift DE 198 03 591 A1 (PB10656 DE) of the applicant. The twin-wire former shown comprises two circumferential endless screens (inner screen, outer screen), of which the inner screen runs over a peripheral area of a forming roller and the outer screen over a peripheral area of a breast roller runs and then in the field of forming roll on the inner wire to form a wedge-shaped material inlet gap, which receives a pulp suspension directly from a headbox, runs up. Subsequently, the two screens (inner screen, outer screen) form a Doppelsiebstrecke, which runs at the end of the forming roller at an angle of -50 ° to + 50 ° to an imaginary vertical plane down and at the end of a deflection, in particular a guide roller is arranged , which deflects at least one of the two wires in a preferably substantially horizontal direction. In the region of the downwardly extending twin-wire section, a plurality of drainage elements in the form of a forming shoe are arranged on both sides, which act on the fibrous web lying between the two wires and forming. After deflection and at the end of the twin-wire section, the two screens pass over a separating device which separates the outer screen from the formed fibrous web and the inner screen.

This known twin-wire former has the disadvantage that the forming shoe in overload operation can cause most diverse defects within the fibrous web to be formed. Moreover, this embodiment of the twin-wire former causes increased screen wear in the area of the drainage elements.

Furthermore, so-called roll shapers are known, such as an embodiment in the German Offenlegungsschrift DE 44 43 874 A1 (PB10112 DE) of the applicant. In this case, two circumferential Endlossiebe are provided, which converge to form a Stoffeinlaufspalts along a Formierzylinders, over the circumference at least partially the two Endlossiebe are jointly performed, one of the screens is a transport screen and the other is a Gegensieb. Furthermore, a second arranged in the other sieve forming cylinder is provided in the direction of the wire behind the first arranged in one of the screens Formierzylinder, said second Formierzylinder in Sieblaufrichtung another fixed dewatering device with subsequent separator follows.

The disadvantage of this roll former is that the frictional connection between the two screens is low and thus allows slippage between the two screens, and even favored. As a consequence, once again very diverse defects can arise within the fibrous web to be formed. Furthermore, such a roll former is characterized by a relatively low dewatering performance.

It is therefore an object of the invention to improve a method and a twin-wire former of the type mentioned above so that both a lower Siebverschleiß compared Doppelsiebformern with Formierschuhen or a higher adhesion between the two screens as well as improved drainage performance over Doppelsiebformern without Formierschuhe (rollformer) allows becomes.

This object is achieved according to the invention in a twin-wire former of the type mentioned by the features of the characterizing part of claim 1.

The stripping device comprises a machine-wide squeegee, which, for reasons of strength, has a strip width in the range from 10 mm to 200 mm, preferably from 15 mm to 150 mm. Such a squeegee is also characterized by a flexible applicability and lower costs.

It is further provided that the wiper blade has a point angle in the range of 15 ° to 45 °, preferably from 25 ° to 35 °, an outlet angle in the range of 2 ° to 45 °, preferably from 5 ° to 25 °, and a Spitzenfase or a Tip radius in the range of 0.5 mm to 5 mm, preferably from 1 mm to 2 mm. When immersing the squeegee without tip radius occur when looping the outlet side additional shear forces that can lead to defects within the fibrous web to be formed. Or it comes due to an undefined Siebführung on the outlet side to so-called "Foil-effects" that can damage the fiber structure by sieve separations in the twin-wire area.

Furthermore, such an embodiment of the point angle ensures a clean flow guidance of the white water, wherein flow pulses in the cross machine direction (CD direction) are prevented in particular at machine speeds of> 1,000 m / min. This in turn leads to a homogenization of the white water removal, which also improves the moisture and Basisgewichtsquerprofile.

As a result of this immersion of the machine-width stripping device, a pressure peak is created at its inlet, which prevents the formation of the so-called "water-skiing effect". The wiper keeps the pressure peak even with changing inlet conditions of the fibrous web, such as the suspension height, constant. This ensures optimum adhesion between the two screens with the best possible avoidance of differential speeds. In addition, the Siebverschleiß and the energy consumption of the twin-wire former are significantly reduced and it also creates a compact design of the same.

In a further embodiment of the invention, it is provided that the two screens in the range of 0 mm to 10 mm, preferably 1 mm to 7 mm, are deflected by the imaginary tangent and / or that the two screens at a distance from the running tangent point of the forming roller be deflected in the range of 25 mm to 300 mm, preferably from 50 mm to 200 mm.

These geometries according to the invention favor in a positive way a lower screen wear, a higher adhesion between the two wires and an improved dewatering performance of the twin-wire former.

In an advantageous development of the twin-wire former, provision is made for the suspension thickness of the pulp suspension to be measured after it has been introduced into the area between the two screens via the forming roller.

In Spaltformern (Gapformern), which have in the running direction of the pulp suspension first a forming roller and an adjoining shoe part (Formierschuh), namely, there is the problem that the amount of suspension between the wires, that is between the inner and outer wire, after the forming roller is still present, can not be detected without difficulty.

However, this detection is important in that the formation quality of the sheet portion formed on the forming roller is different (softer) than that of the sheet portion formed on the shoe portion (gritty formation) and the sum of these two sheet portions determines the sheet strength, which is an important paper property, in particular for packaging papers, is.

The practiced according to the prior art form of detection of all coming in the production of the fibrous web water streams, for example by means of inductive flow meters in the individual leads of the headbox and in the derivatives of the former, is costly and maintenance-intensive. In addition, it is not very accurate and error-prone. According to the invention, a direct detection of the suspension layer thickness is carried out.

A possible prior art arrangement of measuring devices between the forming roller and a subsequent forming box is problematic in many cases, since the measuring device requires a certain space and then the required minimum distance between the tangent point for the expiration of both screens on the forming roller and the tip of the Formierschuhs no longer exists. Both sieves are then no longer positively guided over a longer distance and can therefore oscillate freely, for example, thereby destroying the wet fibrous web between the sieves or at least impairing their formation and strength.

In order to avoid possible damage to the fibrous web to be formed as a result of spray water flows as far as possible, the stripping device is provided with a collecting device, in particular a collecting trough, for collecting and discharging the dehydrated by the stripping of the pulp suspension white water.

Furthermore, it is provided that the stripping device has at least one closed, preferably extending into the region of the forming roller beam channel. This jet channel is preferably acted upon by negative pressure and / or with overpressure, wherein it is sealed in the region of the forming roll by means of at least one scraper and laterally in each case by means of at least one gap seal. This "closed" jet channel with negative pressure and / or overpressure allows targeted control / regulation of the drainage pressure. By means of negative pressure, the reduction of the dewatering pressure can be conditionally compensated by large roll diameters. By lower pressure between the sieves, the filter cake can be kept open (avoiding "sheet sealing") and the drainage performance can be increased.

In order to be able to adjust, regulate or control the intensity of the wiping, it is provided that the stripping device, in particular the wiper strip, can be pressed elastically against the outer wire. The pressing is preferably carried out by means of at least one actuating unit, for example in the form of a cylinder, a spring element or a motor.

In a further embodiment, it is proposed that at least two stripping devices are provided, wherein at least one stripping device in each case dips into the outer screen and into the inner screen. This design significantly favors a lower screen wear, a higher adhesion between the two screens and an improved dewatering performance of the twin wire former.

Also, it is advantageous in terms of constructive and economic aspects, if the twin-wire section has a forming roller, which according to the invention advantageously a diameter in the range of 1.0 m to 3.0 m, preferably from 1.2 m to 2.4 m, and has a wrap angle in the range of 10 ° to 180 °. This forming roll is ideally designed as an open roll and digested by means of a grill or honeycomb structure and / or it is a suction roll.

The deflection of the Doppelsiebformers is preferably designed as a guide roller and has a diameter in the range of 0.4 m to 2.4 m, preferably from 1.0 m to 1.8 m, and a wrap angle in the range of 50 ° to 180 ° , The deflection device is formed in a favorable manner as a deflection roller in the form of a bending roll or forming roll.

Furthermore, the longitudinal axes of the forming roller and the deflecting device preferably have a horizontal spacing which is in the range of +1.25 * diameter the forming roller (in the direction) to -1.25 * diameter of the forming roller (opposite to the direction) is. This length is particularly advantageous for conversions, as this is usually only a limited space available.

In an advantageous development of the twin-wire former after the forming roller in the running direction of the pulp suspension is equipped with a measuring device for measuring the suspension thickness of the pulp suspension. This measuring device ensures accurate measurement of the suspension thickness.

Advantageously, the measuring device is mounted so that the measuring device is arranged in front of a downstream in the direction of the pulp suspension strip part on the inner screen or the outer screen. The measuring device is mounted either on the inner sieve or on the outer sieve. However, it can also be provided that a measuring device is mounted both on the inner screen and on the outer screen.

It is also advantageous if the measuring device is arranged in a housing in which at least one strip is arranged with at least one sensor. Through the housing, the measuring device is protected against damage. It is understood that a plurality of transducers can be arranged in a housing, which are arranged for example across the width of the screen next to each other. Advantageously, the transducers are mounted oscillating or traversing. The transducers are arranged either within a bar or within the housing.

It can also be provided that different types of transducers are used, for example, those that use electromagnetic waves and others that work with ultrasound.

In addition, can be connected to the housing of the measuring device, a device for adjusting a negative pressure, through which a negative pressure can be applied. It is sufficient already a slight negative pressure to ensure that the measuring device initially running sieve always rests against the measuring head and the bar or strips peel off or peel off excess white water from the screen, without thereby measurement values can be falsified. In certain situations, an overpressure which can also be determined via a pressure control or regulating system can be applied to the housing in which the measuring device is arranged.

With respect to the screen on which the housing rests, this has either a straight contour or it is slightly curved in the direction of the screen to the center.

In one embodiment of the invention it is provided that the at least one strip can be pressed against the inner sieve or the outer sieve in a stationary or elastic manner or can be pressed against the inner sieve or the outer sieve exclusively during a measuring process.

Of particular advantage is a twin-wire former in which the suspension thickness measured by the measuring device can be supplied to a regulating device for regulating a constant suspension thickness. By means of the control device, the suspension thickness can be regulated by changing a parameter of the twin-wire former, in particular the negative pressure in the forming roller and / or in a first shoe part.

In an advantageous embodiment of the invention, over the width of the Doppelsiebformers a plurality of individually and independently adjustable ranges, in particular in the forming, is present, in which the suspension thickness is individually adjustable. Accordingly, several transducers can be mounted in the measuring device, each of which measures the suspension thickness in one of the regions. In conjunction with a respective associated control unit so that the suspension thickness is in sections as Control parameters used to produce an optimized in their parameters fibrous web. With the control unit, the suspension thickness can be regulated at one position or in the transverse profile.

In an advantageous embodiment, the stripping device is housed in a housing in which the measuring device is additionally arranged. This ensures that the measuring device is mounted in a protected environment. In addition, no additional space is required for the measuring device, resulting in an additional free Sieblänge.

So that a clearly measurable suspension thickness is available, after the strip part with the measuring device there is a further roller, in particular a deflection roller and / or a suction roller, or a buckling roller looped around by both screens, both for a strong dehydration of the pulp suspension in the region after Ensure shoe part.

In addition, in an embodiment of the invention, it can be provided that the measuring device comprises a flushing device and / or a cleaning device.

Maintenance and cleaning work on the measuring device are supported when a lighting device is provided.

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

Figur 1:

eine schematisierte Seitenansicht eines erfindungsgemäßen Doppelsiebformers;

Figur 1A:

eine schematisierte Seitenansicht einer Abstreifeinrichtung des erfindungsgemäßen Doppelsiebformers;

Figuren 1B und 1C:

zwei schematisierte und detaillierte Seitenansichten von Abstreifeinrichtungen des erfindungsgemäßen Doppelsiebformers;

Figur 2:

eine weitere schematisierte und detaillierte Seitenansicht einer Abstreifeinrichtung des erfindungsgemäßen Doppelsiebformers;

Figuren 2A und 2B:

zwei Detailansichten der Abstreifleiste der Figur 2;

Figur 3:

eine weitere schematisierte Seitenansicht des erfindungsgemäßen Doppelsiebformers; und

Figuren 4 bis 7:

weitere schematische Darstellungen eines Doppelsiebformers, in dem zusätzlich eine Messvorrichtung eingebracht ist.

Show it:

FIG. 1:

a schematic side view of a Doppelsiebformers invention;

FIG. 1A

a schematic side view of a stripping of the Doppelsiebformers invention;

FIGS. 1B and 1C:

two schematic and detailed side views of stripping means of the twin-wire former according to the invention;

FIG. 2:

a further schematic and detailed side view of a stripping of the Doppelsiebformers invention;

FIGS. 2A and 2B:

two detailed views of the squeegee of the FIG. 2 ;

FIG. 3:

a further schematic side view of the Doppelsiebformers invention; and

FIGS. 4 to 7:

further schematic representations of a Doppelsiebformers, in which a measuring device is additionally introduced.

The figure 1 shows a schematic side view of a twin-wire former 1 of a machine for producing a fibrous web 2, in particular a paper or board web, from at least one pulp suspension 3, with two continuous endless sieves (inner sieve 4, outer sieve 5), of which the inner sieve 4 over a peripheral region. 6 a preferably evacuated forming roller 7 runs and the outer wire 5 runs over a peripheral region 8 of a breast roll 9 and then in the field of Formierwalze 7 on the inner wire 4 to form a wedge-shaped Stoffeinlaufspalts 10, which receives directly from a preferably dilution water-regulated headbox 11 a pulp suspension 3 , accumulates and the two sieves (inner sieve 4, outer sieve 5) then form a twin-wire section 12, which after passing from the forming roller 7 at an angle δ of -50 ° to + 50 ° (schematic area indication - / + δ) to an imaginary vertical plane V runs down and at the end e Ine deflecting device 13, in particular a guide roller 13.1 is arranged, which deflects the two wires 4, 5 in a preferably substantially horizontal direction L (arrow). After the deflection and at the end of the twin-wire section 12, the two wires 4, 5 run over a separator 14, which the outer screen 5 separates from the formed fibrous web 2 and the inner wire 4. The outer wire 5 passes over guide rollers 15 back to the breast roll 9, whereas the inner wire 4 is guided with the fibrous web 2 thereon to a pickup roller, not shown, before it then also runs over guide rollers 15 back to the forming roller 7.

The twin-wire former 1 shown here according to the embodiment of the already mentioned German Offenlegungsschrift DE 198 03 591 A1 (PB10656 DE) of the applicant, in a further embodiment, also according to the embodiment of German patent application DE 196 51 493 A1 (PB10449 DE) of the applicant. In other words, the possible execution of the twin-wire former is not intended to be based on the embodiment according to the FIG. 1 be limited, the execution according to the FIG. 1 is intended to be merely exemplary in nature of a variety of possible embodiments for the twin-wire former.

It is now provided that at least one machine-width stripping device 16, in particular a machine-wide squeegee 16.1, between the forming roller 7 and the deflecting device 13 is arranged such that it dips into the outer wire 5 and that they are the two wires 4, 5 of one between the forming roller 7 and the deflecting 13 imaginary tangent T (dashed line) in the direction of the inner screen 4 deflects.

The stripping device 16 has an immersion depth t in the outer screen 5 in the range of 0 mm to 10 mm, preferably 1 mm to 7 mm, and a distance a from the running tangent point TP of the forming roller 7 in the range of 25 mm to 300 mm, preferably 50 mm to 200 mm, on.

Furthermore, the stripping device 16 comprises a machine-wide squeegee 16.1, which ideally has a strip width B in the range of 10 mm to 200 mm, preferably from 15 mm to 150 mm.

Moreover, the stripping device 16 is provided with a collecting device 17, in particular a collecting trough 17.1, for collecting and discharging the white water 18 dewatered by the stripping device 16 from the fibrous suspension 3. The collecting device 17 may be executed closed in a further embodiment and provided with at least one preferably evacuated outlet.

The forming roller 7 of the twin-wire former 1 has a diameter D _F in the range of 1.0 m to 3.0 m, preferably 1.2 m to 2.4 m, and a wrap angle ε _F in the range of 10 ° to 180 ° ,

The deflection device 13 of the twin-wire former 1, on the other hand, is designed as a deflecting roller 13.1 and has a diameter D _U in the range from 0.4 m to 2.4 m, preferably from 1.0 m to 1.8 m, and a wrap angle ε _U in the range from 50 ° to 180 °. The deflection device 13 is formed as a deflection roller 13.1 in a preferred form of a bending roll or forming roll.

The figure 1A shows a schematic side view of a stripping device 16 of the twin-wire former 1 according to the invention.

It is provided that the stripping device 16 has at least one closed, preferably up to the area of the forming roller 7 extending beam channel 19. The jet channel 19 can be acted upon by means of a vacuum device (arrow) which is not shown, but known and preferably controllable / controllable, with negative pressure (-p) and / or with overpressure (+ p), whereby it is provided in the region of the forming roller 7 by means of at least one known doctor 20 and laterally sealed in each case by means of at least one known gap seal 21. Of course, the stripping device 16 is again provided with a collecting device 17 for collecting and discharging the white water 18 dewatered by the stripping device 16 from the fibrous suspension 3.

The two FIGS. 1B and 1C show two schematic and detailed side views of stripping 16.1 formed stripping 16 of the invention Doppelsiebformers. 1

In this case, the two squeegee 16.1 each have an outlet angle α in the range of 2 ° to 45 °, preferably from 5 ° to 25 ° on. In addition, the squeegee 16.1 can be provided with different, the outer wire 5 touching contours, such as with zigzag or sawtooth or wavy shape.

Within the scope of the optional adjustment, regulation or control of the intensity of the wiping it is provided that the stripping device 16, in particular the wiper strip 16.1, can be elastically pressed against the outer screen (5). In this case, the pressing (directional arrow E) preferably takes place by means of at least one actuating unit which is not explicitly shown, but which is known to the person skilled in the art, for example in the form of a cylinder, a spring element or a motor. Of course, in a further embodiment, a plurality of actuating units distributed over the outer sieve 5 with possibly different settings may of course also be provided.

The figure 2 shows a further schematic and detailed side view of a stripping device 16 of the twin-wire former 1 according to the invention.

The stripping device 16 is designed as a stripping bar 16.1, which has an inlet radius R ₁ in the range of 0 mm to 100 mm, an arc length L _B in the range of 3 mm to 15 mm and an outlet radius R ₂ in the range of 2 m to 5 m , And again, the outlet angle α formed on the wiper strip 16.1 can be seen in the range from 2 ° to 45 °, preferably from 5 ° to 25 °.

The two FIGS. 2A and 2B show two detailed views of the squeegee 16.1 of FIG. 2 ,

It can be seen that the wiper strip 16.1 has a point angle β in the range of 15 ° to 45 °, preferably 25 ° to 35 °, and a tip radius R ₃ in the range of 0.5 mm to 5 mm, preferably 1 mm to 2 mm, has. In a further embodiment, the squeegee 16.1 and a Spitzenfase, not shown, preferably with a flat surface, have.

The figure 3 shows a further schematic side view of the twin-wire former 1 according to the invention, which in principle the embodiment of the FIG. 1 equivalent. Thus, in this regard, the description of the FIG. 1 directed.

It is now provided that at least two stripping devices 16, 16A are provided, with at least one stripping device 16, 16A each dipping into the outer screen 5 and into the inner screen 4. In the illustrated embodiment of FIG. 3 a total of two stripping devices 16, 16A are provided.

Furthermore, the longitudinal axes I, II of the forming roller 7 and the deflecting device 13 have a horizontal distance C in the range of +1.25 * diameter D _{F of} the forming roller 7 (in the direction L (arrow) - solid representation) to - 1, 25 * diameter D _{F of} the forming roller 7 (opposite to the direction L (arrow) - dashed line) is located.

The two wires 4, 5 are deflected between the forming roller 7 and the deflecting device 13 by means of at least one machine-width stripping device 16 from an imaginary between the forming roller 7 and the deflector 13 tangent T in the direction of the inner wire 4. In this case, the two wires 4, 5 preferably in the range of 0 mm to 10 mm, in particular from 1 mm to 7 mm, of the imaginary tangent T and at a distance from the running tangent point TP of the forming roller 7 in the range of 25 mm to 300 mm , preferably from 50 mm to 200 mm, deflected.

In a further embodiment of the twin-wire former 1 (FIG. FIG. 4 ) it is provided that at the distance d to the tangent point TP on the forming roller 7, a stripping device 30 is arranged, whose function coincides with that of the stripping device 16, which, however, is also equipped with a measuring device 31.

The stripping device 30 comprises a housing 32, in which, spaced from one another, three individual strips 33, 34, 35 are arranged in the direction of the outer screen 5. The upper and the forming roller 7 first located bar 33 receives the measuring device 31. The strip 33 has a width of, for example, between 10 and 180 mm.

Above the housing 32, a trough-shaped discharge device 36 for discharging white water via an outlet 37 is arranged. The housing 32 serves as a collecting trough for the white water stripped by the strips 33, 34, 35 from the wire 5, which is discharged via an outlet 38, in particular by means of a suction pump. Below the housing 32, a separating sucker 39 is arranged, which serves to separate the fibrous web from the wire 4, so that it remains on the wire 5. Another separating sucker 40 is arranged below a wire 41, on which the fibrous web is transferred from the wire 5. The housing 32 has opposite the wire 5 either a straight or a curved shape, a corresponding shape have the strips 33, 34, 35th

In a further embodiment ( FIG. 5 ), a measuring device 31 is arranged in a housing 42 on the outer sieve 5. By means of a pump 43, white water is sucked out of the housing 42. On both sides of the sieves 4, 5 discharge means 44, 45, 46 are arranged for discharging white water, which are respectively equipped with pumps 44.1, 45.1, 46.1 or with drains for discharging the collected in the trough-shaped discharge means 44, 45, 46 white water. As in the embodiment according to FIG. 4 is here below the Aussensiebes 5 to the wire 41 a separating sucker 40 available.

In a further embodiment ( FIG. 6 ) is the forming roller 7 on the opposite side of the outer wire 5 in the running direction of the pulp suspension 3 downstream of a stripping 47. The contact pressure of a wiper strip 47.1 of the stripping device 47 is fed to a control device 48 as an actual variable; this generates therefrom a target size for a pressure valve 49 for adjusting the pressure within a housing 50 surrounding the stripping device 47 by means of compressed air or, alternatively, for the immediate adjustment of the contact pressure of the stripping strip 47.1.

On the side of the inner screen 4, a stripping device 51 with scraper strips 52, 53, 54 is arranged within a housing 55. The wiper strip 54 is equipped with a measuring device 56 for measuring the suspension thickness; Within the housing 55, the internal pressure is connected via a control device 59 to a pressure valve 57 for adjusting the pressure in the housing 55. The actual pressure is supplied to the control device 59, which generates a desired pressure for the pressure valve 57 therefrom. The stripper 51 opposite to the side of the outer screen 5 elastically resilient strips 58 are arranged, which support the wires 4, 5 and the guided between them fibrous web in position relative to the stripping 51.

According to another embodiment ( FIG. 7 ), which in their construction correspond to the one in Fig. 3 shown twin-wire former with a guide roller 13 are in the stripping 16, 16A are scraper blades 60, 61 provided with transducers 62, 63 above troughs 65, 66 for the removal of white water. According to the invention, the direct detection of the suspension thickness is made possible. The measuring device is located in a protected environment in a bar or in a housing. For the measuring device no additional space is needed. Additional free Sieblängen be avoided. The measuring device can be introduced into a control device for controlling the suspension thickness, the suspension thickness being determined either at the Position of the measuring device over the entire width or over individual sections of the fibrous web width is regulated.

In summary, it should be noted that the invention provides a method and a twin-wire former of the type mentioned above with both less screen wear compared to twin wire formers with forming shoes or a higher adhesion between the two wires as well as an improved drainage performance compared to twin wire without formers (roll former).

LIST OF REFERENCE NUMBERS

1

twin

2

Fibrous web

3

Fibrous suspension

4

inside screen

5

outer wire

6

Peripheral area (forming roller)

7

forming roll

8th

Peripheral area (breast roll)

9

breast roll

9.1

Brustformierwalze

9.2

Open surface

10

Stock inlet gap

11

headbox

12

twin-wire

13

deflecting

13.1

deflecting

14

separator

15

guide roll

16, 16A

stripping

16.1

squeegee

17

catcher

17.1

drip tray

18

white water

19

beam channel

20

scraper

21

gap seals

30

stripping

31

measuring device

32

casing

33, 34, 35

strip

36

removal device

37

outlet

38

outlet

39.40

suction separator

41

wire

42

casing

43

pump

44, 45, 46

removal device

44.1, 45.1, 46.1

pump

47

stripping

47.1

squeegee

48

control device

49

pressure valve

50

casing

51

stripping

52, 53, 54

squeegee

55

casing

56

measuring device

57

pressure valve

58

strip

59

control device

60.61

squeegee

62, 63

transducer

65, 66

tub

a

distance

B

last width

c

distance

d

distance

D _F

Diameter (forming roller)

D _U

Diameter (deflection device)

e

Pressing (directional arrow)

I

Longitudinal axis (forming roller

II

Longitudinal axis (deflection device)

L

Running direction (arrow)

L _B

arc length

- p

vacuum

R ₁

entry radius

R ₂

outlet radius

R ₃

tip radius

t

Immersion depth

T

tangent

TP

tangent point

V

vertical plane

α

exit angle

β

Point angle

δ

angle

ε _F

Wrap angle (forming roll)

ε _U

Wrap angle (deflection device)

+ p

overprint

Claims (25)

1. Twin-wire former (1) of a machine for producing a fibrous web (2), in particular a paper or paperboard web, from at least one fibrous stock suspension (3), having a circulating endless inner wire (4) and a circulating endless outer wire (5), of which the inner wire (4) runs over a circumferential region (6) of a forming roll (7) and the outer wire (5) runs over a circumferential region (8) of a breast roll (9) and subsequently, in the region of the forming roll (7), rolls onto the inner wire (4) with the formation of a wedge-shaped stock inlet gap (10) which receives a fibrous stock suspension (3) directly from a headbox (11), and the two wires (inner wire (4), outer wire (5)) subsequently form a twin-wire section (12) which, after running off from the forming roll (7) runs downwards at an angle (δ) of from -50° to +50° with respect to an imaginary vertical plane (V) and at the end of which a deflection device (13) is arranged, in particular a deflection roll (13.1), which deflects at least one of the two wires (4, 5) into a preferably substantially horizontal running direction (L), at least one machine-width wide wiping device (16) being arranged between the forming roll (7) and the deflection device (13) in such a way that it dips into the outer wire (5) and that it in the process diverts the two wires (4, 5) from an imaginary tangent (T) between the forming roll (7) and the deflection device (13) in the direction of the inner wire (4), characterized in that the wiping device (16) has a machine-width wide wiping strip (16.1) which has a strip width (B) in the range from 10 mm to 200 mm, preferably from 15 mm to 150 mm, and in that the wiping strip (16.1) has a tip angle (β) in the range from 15° to 45°, preferably from 25° to 35°, and a tip chamfer or a tip radius (R₃) in the range from 0.5 mm to 5 mm, preferably from 1 mm to 2 mm.
2. Twin-wire former (1) according to Claim 1, characterized in that the wiping strip (16.1) has a dipping depth (t) into the outer wire (5) in the range from 0 mm to 10 mm, preferably from 1 mm to 7 mm.
3. Twin-wire former (1) according to Claim 1 or 2, characterized in that the wiping strip (16.1) has a spacing (a) from the running-off tangent point of the forming roll (7) in the range from 25 mm to 300 mm, preferably from 50 mm to 200 mm.
4. Twin-wire former (1) according to one of Claims 1 to 3, characterized in that the wiping strip (16.1) is provided with a collecting device (17), in particular a collecting trough (17.1), for collecting and discharging the white water (18) which is removed from the fibrous stock suspension (3) by the wiping strip (16.1).
5. Twin-wire former (1) according to one of Claims 1 to 4, characterized in that the wiping strip (16.1) has at least one closed jet channel (19) which preferably extends as far as into the region of the forming roll (7).
6. Twin-wire former (1) according to Claim 5, characterized in that the jet channel (19) can be loaded with vacuum (-p) and/or with excess pressure (+p), the said jet channel (19) being sealed in the region of the forming roll (7) by means of at least one doctor (20) and laterally in each case by means of at least one gap seal (21).
7. Twin-wire former (1) according to one of Claims 1 to 6, characterized in that the wiping strip (16.1) has a running-off angle (α) in the range from 2° to 45°, preferably from 5° to 25°.
8. Twin-wire former (1) according to one of Claims 1 to 7, characterized in that the wiping strip (16.1) can be pressed onto the outer wire (5) elastically.
9. Twin-wire former (1) according to one of Claims 1 to 8, characterized in that at least two wiping devices (16, 16A) are provided, at least in each case one wiping device (16, 16A) dipping into the outer wire (5) and into the inner wire (4).
10. Twin-wire former according to one of Claims 1 to 9, characterized in that the forming roll (7) of the twin-wire former (1) has a diameter (D_F) in the range from 1.0 m to 3.0 m, preferably from 1.2 m to 2.4 m.
11. Twin-wire former (1) according to one of Claims 1 to 10, characterized in that the forming roll (7) of the twin-wire former (1) has a wrap angle (ε_F) in the range from 10° to 180°.
12. Twin-wire former (1) according to one of Claims 1 to 11, characterized in that the deflection device (13) of the twin-wire former (1) is configured as a deflection roll (13.1) and has a diameter (D_U) in the range from 0.4 m to 2.4 m, preferably from 1.0 m to 1.8 m.
13. Twin-wire former (1) according to one of Claims 1 to 12, characterized in that the deflection device (13) of the twin-wire former (1) has a wrap angle (ε_U) from 50° to 180°.
14. Twin-wire former (1) according to one of Claims 1 to 13, characterized in that the deflection device (13) is configured as a deflection roll (13.1) in the form of an articulated roll or forming roll.
15. Twin-wire former (1) according to one of Claims 1 to 14, characterized in that the longitudinal axes of the forming roll (7) and the deflection device (13) have a horizontal spacing (c) which lies in the range from +1.25 * the diameter (D_F) of the forming roll (7) (in the running direction (L)) to -1.25 * the diameter (D_F) of the forming roll (7) (counter to the running direction (L)).
16. Twin-wire former (1) according to one of Claims 1 to 15, characterized in that a measuring apparatus (31, 56) for measuring the suspension thickness of the fibrous stock suspension (3) is arranged behind the forming roll (7) in the running direction L (arrow) of the fibrous stock suspension (3).
17. Twin-wire former (1) according to Claim 16, characterized in that the measuring apparatus (31, 56) is arranged on the inner wire (4) or the outer wire (5) in front of a strip part which trails in the running direction L (arrow) of the fibrous stock suspension (3) .
18. Twin-wire former according to Claim 16 or 17, characterized in that the measuring apparatus (31, 56) is arranged in a housing (32), in which at least one strip (33, 34, 35, 58) having at least one measured-value sensor (62, 63) is arranged.
19. Twin-wire former (1) according to one of Claims 16 to 18, characterized in that the wiping device (47, 51) which comprises the housing (32, 50) and the measuring apparatus (31, 56) is connected to a device (59) for setting a vacuum, by way of which device (59) a vacuum can be applied.
20. Twin-wire former (1) according to one of Claims 16 to 19, characterized in that the at least one strip (33, 34, 35, 58) can be pressed against the inner wire (4) and the outer wire (5) in a stationary or elastic manner, or can be pressed against the inner wire (4) and the outer wire (5) exclusively during a measuring operation.
21. Twin-wire former (1) according to one of Claims 16 to 20, characterized in that the suspension thickness which is measured by the measuring apparatus (31, 56) can be fed to a regulating apparatus (59) for regulating a constant suspension thickness, and in that the suspension thickness can be regulated by the regulating apparatus by changing a parameter of the twin-wire former (1), in particular the vacuum in the forming roll (7) and/or in a first shoe part.
22. Twin-wire former (1) according to Claim 21, characterized in that there are a plurality of regions which can be adjusted individually and independently of one another over the width of the twin-wire former (1), in particular in the forming roll (7), in which regions the suspension thickness can be set.
23. Twin-wire former (1) according to one of Claims 16 to 22, characterized in that a further roll, in particular a deflection roll (13.1) and/or a suction roll, or an articulated roll which is wrapped around by the two wires (4, 5), is arranged behind the measuring apparatus (31, 56).
24. Twin-wire former (1) according to one of Claims 16 to 23, characterized in that the measuring apparatus (31, 56) comprises a rinsing apparatus and/or a cleaning apparatus.
25. Twin-wire former (1) according to one of Claims 16 to 24, characterized in that an illumination device is arranged on the measuring apparatus (31).

Images