DE10014322A1 - Double fourdrinier pulp former section has a continuous former belt/blanket with the lower fourdrinier supported by a sliding shoe to give an extended water extraction stretch - Google Patents

Abstract

The double fourdrinier water-extraction section (10), to convert a pulp into a wet paper or cardboard web (12), has a pulp former as a continuous former belt or blanket (20) within the loop of the lower fourdrinier (16), which passes at least partially around it. The former belt (20) passes over at least one sliding shoe (22), where the belt and the lower fourdrinier are moving together. The sliding shoe (22) has a length of 0.2-3.0 m, along the direction (L) of web travel. The former belt (20) has an open outer peripheral surface with blind drillings and/or grooves, and is especially grooved with external suction.. A generally straight and/or at least a curved water extraction stretch is between the zone where the former belt (20) is caught and the fourdrinier separation point (T). The former belt (20) is moved by the lower fourdrinier (16), or an external drive. Where the former belt (20) is on the deflected path, the path has a number of different curve radii in a range from zero to infinity. The sliding shoe (22) has different curve radii. The sliding shoe (22) has a hydrodynamic and/or hydrostatic action. The former belt (20) has guides of a number of supports (22), and is led at least partially by rollers. The double fourdrinier assembly is a gap former, where the pulp flow is taken initially by a curved water extraction stage where it meets preferably a fourdrinier or an open former belt/blanket.

Description

The invention relates to a twin wire former of a machine for manufacturing position of a fibrous web, in particular paper or cardboard web, with a revolving endless top sieve and a revolving endless Bottom wire that converge in the area of a forming element.

Forming rolls in gap formers are relatively expensive. With increasing foliage weight gain or increasing speed increases the required Liche forming roller diameter up to about 1.8 m.

With larger radii or diameters, the production is more difficult, what especially for versions with on drilled smoothing cylinder seen grill applies.

Distributing the weight over two formers is expensive.

The pressure difference over the suspension height in the curved forming gap also increases with (g. H. V ² ) / R, where g = density, h = suspension height, R = radius, v = speed.

This leads to different speeds over the Suspensi height and thus to different fiber orientations above the z Direction of the sheet of paper.  

The aim of the invention is to provide a twin wire former of the type mentioned To create a way that realizes a longer drainage route is in which the fibrous web is dewatered on two sides. there should in particular also have a gap height of up to about 70 mm, for example be possible, which would be particularly good for burst pressure. Moreover such gap heights should be observed especially at low speeds speeds of, for example, about 200 m / min, which is a so-called called "heavy linerboard" would be good.

This object is achieved according to the invention in that the shape relement by a arranged in the loop of the bottom wire, from this partially wrapped endless forming belt or -cloth is formed.

The forming belt is preferably over in the wrap area performed at least one shoe. This can conveniently egg ne have a length of approximately 0.2 m to 3 m as measured in the direction of travel of the strip.

The forming belt can be partially wrapped around the bottom wire and appropriately have an open outer peripheral surface.

The outer peripheral surface of the forming belt can, for example, be blind drilled and / or grooved.

In a convenient practical embodiment of the fiction According to the twin wire former, the forming belt is especially grooved and sucked from the outside.  

Between the area surrounding the forming cloth and the screen separator position is expediently at least one at least essentially straight and / or at least a curved drainage section in front seen.

The forming belt can for example over the bottom wire or over an external drive can be driven.

It is also advantageous if the forming belt is in the wrap area is guided along a path with a different radius of curvature. The different radii of curvature can each have a value in Have a range from 0 to ∞.

For example, the shoe can have different radii of curvature s.

In particular, it can be a hydrodynamic and / or hydrostatic Be provided.

In certain cases it is also advantageous if the forming belt is closed is at least partially guided by several support elements. The support element elements can at least partially be replaced by a Be formed.

Alternatively or additionally, it is also possible for the forming belt to be closed is at least partially guided by rollers.  

The twin wire former can also be designed as a gap former, for example be, in which the fiber suspension jet on an initial ge curved drainage section, preferably a sieve or open a forming tape or cloth.

The invention is un based on exemplary embodiments ter described in more detail with reference to the drawing; in this show:

Fig. 1 is a schematic representation of a first exporting approximate shape of a twin having a partially looped by the bottom wire encircling Formier band, which is guided in the wrap shoe over a slide,

Fig. 2 is a schematic representation of another Ausfüh approximate shape of a twin wire former, in which the For mierband is at least partially guided by several support elements, and

Fig. 3 is a schematic representation of a further embodiment of a twin wire former with an at least partially guided by a sliding shoe and at least one further support element forming belt.

Figs. 1 to 3 show in a purely schematic illustration of a twin respectively 10 for the manufacture of a fibrous web 12, which may be in particular a paper or board web.

The twin wire formers 10 each comprise a twin wire zone 14 , which is formed by a rotating endless bottom wire 16 and a rotating endless top wire 18 .

The two screens 16 , 18 run together in the area of a forming element, which is formed by a continuous forming belt or cloth 20 arranged in the loop of the lower wire 16 and partially wrapped around it.

The forming belt 20 suitably has an open outer peripheral surface. This outer peripheral surface can, for example, be drilled blind and / or grooved. Especially with a grooved outer circumferential surface, this forming tape 20 can be vacuumed from the outside.

Between the area comprising the forming cloth 20 and the separation point T, at which the lower wire 16 and the upper wire 18 are separated from one another, at least one at least substantially straight and / or at least one curved drainage path can be provided.

The forming belt 20 can be driven via the lower wire 16 or also via a separate drive.

For example, in the area wrapped by the lower wire 16 , the forming belt 20 can be guided along a path with a different radius of curvature. The different radii of curvature can each have a value in the range from 0 to ∞.

The forming belt 20 can be guided through at least one sliding shoe and / or through at least one support element. As an alternative or in addition, a belt guide by rolling is also conceivable.

In the embodiment shown in FIG. 1, the forming belt 20 leads in the wrapping area via at least one sliding shoe 22 ge. This slide shoe 22 can, for example, have a length of approximately 0.2 m to approximately 3 m measured in the tape running direction L.

Larger drainage lengths of, for example, about 2 to about 3 m can be particularly useful for cardboard.

The slide shoe 22 can have different radii of curvature. It can be lubricated hydrodynamically and / or hydrostatically.

In the embodiment shown in FIG. 2, the forming belt 20 is guided, in particular in the looping area, by a plurality of support elements 24 , in which, for example, support shoes can be used again. To improve formation, a pulse generation by vibration of the support elements or support shoes 24 can be provided.

In the present case, the stock inlet gap 26 formed by the two converging screens 16 , 18 lies in an upper region. The fiber suspension supplied by a headbox 28 is introduced into this stock inlet gap 26 .

The two screens 16 , 18 are separated from one another again in the area of a screen suction roll 30 .

In the embodiment according to FIG. 3, the forming belt 20 is guided out of the inlet gap 26 located here laterally firstly via a slide shoe 32 of larger radius of curvature and then via several support elements 34 of smaller radius of curvature. Alternatively or additionally, the forming belt 20 can also be guided over at least one roller.

A combination of internal elements such as larger or larger shoes smaller diameter and at least one roller appears in particular especially for larger, e.g. B. for cardboard certain drainage lengths of about 2 to 3 m, for example.

In the present case, a suction device 36 is provided for an external suction of the particularly grooved forming tape or cloth 20.

The present embodiment differs from that according to FIG. 2 in that the lower wire 16 is continued to the left in the lower left area and the fibrous web 12 is carried along by this lower wire 16 .

Reference list

10th

Twin wire former

12th

Fibrous web

14

Twin-wire zone

16

Bottom sieve

18th

Top sieve

20th

Forming tape or cloth

22

Sliding shoe

24th

Support elements

26

Infeed gap

28

Headbox

30th

Sieve suction roller

32

Sliding shoe

34

Support elements

36

Suction device
L tape running direction
T separation point

Claims (15)

1. twin-wire former ( 10 ) of a machine for producing a fibrous web ( 12 ), in particular paper or cardboard web, with a continuous endless top wire ( 18 ) and a continuous endless bottom wire ( 16 ) in the area of a forming element ( 20 ) run together, characterized in that the forming element is formed by an endless forming belt or cloth ( 20 ) which is arranged in the loop of the lower wire ( 16 ) and is partially wrapped around it. 2. Twin wire former according to claim 1, characterized in that the forming belt ( 20 ) is guided in the looping area over a least least one sliding shoe ( 22 , 32 ). 3. twin-wire former according to claim 2, characterized in that the sliding block ( 22 , 32 ) has a length in the tape running direction (L) measured from about 0.2 m to about 3 m. 4. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) has an open outer peripheral surface. 5. Twin wire former according to one of the preceding claims, characterized in that the outer peripheral surface of the forming belt ( 20 ) is blind-drilled and / or grooved. 6. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) is in particular grooved and sucked from the outside. 7. Twin wire former according to one of the preceding claims, characterized in that at least one at least substantially straight and / or at least one curved drainage section is provided between the region comprising the forming cloth ( 20 ) and the screen separation point (T). 8. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) can be driven via the lower wire. 9. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) can be driven via an external drive. 10. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) is guided in the wrapping area along a path with a different radius of curvature, the different radii of curvature each having a value in the range from 0 to ∞. 11. Twin wire former according to one of the preceding claims, characterized in that the sliding block ( 22 , 32 ) has different radii of curvature. 12. Twin wire former according to one of the preceding claims, characterized in that a hydrodynamic and / or hydrostatic sliding block ( 22 , 32 ) is provided. 13. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) is guided at least partially by a plurality of support elements ( 22 , 32 , 24 , 34 ). 14. Twin wire former according to one of the preceding claims, characterized in that the forming belt ( 20 ) is at least partially guided by rolling. 15. twin wire former according to one of the preceding claims, characterized, that it is designed as a gap former in which the fibrous pulp ion beam on an initially curved drainage section, preferably a sieve or open forming tape or cloth meets.