DE10332658A1 - Sieve screen section of papermaking machine, includes roller opposite forming cylinder supporting inner surface of second sieve belt - Google Patents

Abstract

A roller (9) forms a support opposite the forming cylinder (1), which supports the inner surface of the second sieve belt (2) : The roller (9) surface is structured with studs 2-30 mm high, especially 5-8 mm high. The roller surface has a rectangular or square grid. In an alternative, it carries uniformly-spaced ridges (13) in adjacent rows. The ridges are orientated along the run of the web, or transversely to it. They may form a herringbone pattern. Studs, ridges or grid lines have a spacing of 3-10 mm, especially 4-7 mm.

Description

The The invention relates to a wire section in a machine for manufacturing a paper, board, tissue or other fibrous web from a pulp suspension, which has a headbox on the Wire section with a first and a second each endless screen belt is applied with each other on a part of its circumference forming a twin-wire zone, and at least one in the area the twin-wire zone arranged forming cylinder whose outer surface acts as an outer support surface, wherein at least a part of the support surface is the first Sieve belt on the inner surface and the second screen belt is supported on the outer surface thereof.

From the DE 43 01 103 C1 Such a wire section is known. Pressure elements exert pressure on the inner surface of the second wire in the region in which it is supported by the support surface, the pressure elements apply the pressure only at certain points, the pressure points, so that also pressure-free areas remain. The pressure points are distributed over the entire screen surface. The pressure points act on a forming cylinder and running around this as a support body. Can be used as printing elements bars, roller blades or concave contact pressure shoes.

With these measures should be opportunities for Intensification of drainage and to improve fibrous web quality by preventing flocculation be further developed in the pulp suspension such that the entire length the wire section of a paper machine is reduced. As support elements primarily the peripheral surfaces of Formierzylindern and bands come into consideration, the effects of centrifugal force and initiated pressure pulses and force the drainage the pulp suspension. By avoiding friction on the screen belt will be, the wear and tear reduces the power required to drive.

With the contact pressure of printing elements is achieved that line or punctate Loads and in the case of the concave pressure shoe surface loads be caused on the screen belt leading to turbulence in the Fiber suspension between the screen belts lead, leading to a prevention of flocculation contributes. The printing elements extend, for example, together or each for alone over the entire wire width.

Next The wire section described above, there are others in the art Sieve sections, which operate on the principle of the roll-blade principle, wherein the forming cylinder instead of the printing element or the printing elements a drainage element opposite is arranged. The working on the roll-blade principle Arrangements have the disadvantage that formation disorders by Siebtrennungseffekte occur at the end of the Formierzylinders.

such Disadvantages are avoided in roll-gap formers, in which the sheet formation from the pulp suspension exclusively on the forming cylinder he follows. However, this only creates a bad formation.

to Uniting the benefits of both principles has already been tried Formation strips directly to the forming cylinder of a roll former to act. In this method, however, are also in Transverse direction produces strong local formation disturbances, as the suspension in contrast to static strip parts forced between two rigid flow walls and thus no local self-regulation by dodging a freely movable screen possible is.

It The object of the invention is the formation of a fibrous web to improve and avoid the disadvantages of the prior art.

According to the invention this Task with a wire section of the type mentioned solved in that the forming cylinder opposite and the second screen belt of the inner surface supporting a roller as a support element is arranged.

With This arrangement is a the formation of the pulp suspension shear rate to be generated in the pulp suspension generated. An advantage of the invention is that the sheet formation on a forming element, namely the forming cylinder, is completed. It will be a formation improving shear, d. H. a velocity gradient in cross section the pulp suspension transverse to the direction of the fibrous web, produced without the fibers a preferred orientation in the direction of travel receive.

essential Characteristic of the invention is a roller or roller which is in the range the formation of sheets on the forming cylinder against the outer wire suppressed. The surface the roller and the outer sieve move essentially equally fast in the direction of the screen; but it is also possible a difference in the rotational speed of the roller and the forming cylinder or a difference in the speed of rotation of the screen belt and to provide the roller.

advantageous Further developments of the invention will become apparent from the dependent claims, the Description and the drawings.

With Advantage, the roller has a structured outer surface. By the elevations in the surface the roller comes with the outer, over the Formierzylinder running sieve briefly in contact and presses the pulp suspension one. The impressions generates a momentary squish flow. The caused thereby Shearing in the free suspension improves formation. Especially Advantageously, the squish flow acts in all directions, so no preferred fiber orientation direction arises in the paper web.

With Advantage, the roller is provided on its lateral surface with knobs. These for example, have a height between 2 and 30 mm, in particular between 5 and 8 mm.

In a likewise advantageous alternative embodiment has the roller on her Lateral surface Grid, in particular a rectangular or square grid, on. It is understood that the grid also has a different structure may have.

In Another alternative is the roller with on their advantage lateral surface configured at the same distance to each other arranged webs, which are each arranged in mutually adjacent rows. However, it is also possible the bars at different intervals in different arrangements, in particular random to arrange.

From It is advantageous if in this case the webs in the direction of the fibrous web or are arranged transversely to the direction of the fibrous web.

In another embodiment the invention are on the mantle of the roll webs after a herringbone pattern arranged.

Prefers have the pimples, the webs or the grid lines of the lattice spacings of 3 to 10 mm, in particular from 4 to 7 mm, to each other.

below the invention is in an embodiment explained in more detail with reference to the drawings.

It demonstrate:

1 a section of a wire section of a twin-wire paper machine with a forming cylinder and a roller opposite him,

2 an enlarged section of the pulp suspension between the forming cylinder and the opposite roller and

3a - 3c Representations of various structures on the lateral surface of the roller.

A twin-wire section in a machine for producing a fibrous web, in particular a paper web, comprises a forming cylinder 1 ( 1 ), which either has a closed surface or is provided with a plurality of holes to aid drainage. The forming cylinder 1 is made of two endless sieve bands 2 and 3 on a part of its outer circumference in the wrap area 4 entwined. Along this elbow on the circumference of the forming cylinder 1 become the screen belts 2 . 3 run together and form with each other a twin-wire zone up to a suction roller 5 , Both screen belts 2 . 3 walk in the immediate vicinity of a headbox 6 over the forming cylinder 1 or via a deflection roller 7 together, so that the two screen belts 2 . 3 a wedge-shaped inlet gap 8th form for the pulp suspension.

To the forming cylinder 1 is in the wrap area within the screen belt 3 a roller 9 ( 1 . 2 ) with a textured surface to create a shear rate in the pulp suspension. The roller 9 has elevations on its lateral surface 10 on that the gap between the forming cylinder 1 and the roller 9 shrink when moving through the wrap area 4 move through and thereby a punctual flow away the pulp suspension 11 in the area of the forming cylinder 1 nearest survey 10 to create the shear rate across the direction of travel. The roller 9 can with different contact pressures to the forming cylinder 1 and different distances to the forming cylinder 1 exhibit.

In particular, there are a variety of ways to design the surveys 10 , These are for example pimples 12 ( 3a ).

Alternatively, bridges become 13 ( 3b ) on the lateral surface of the roller 9 used, either in the circumferential direction or in the direction of the longitudinal axis of the roller 9 run. Likewise, the webs 13 also obliquely to the direction of rotation of the roller 9 be arranged, for example in a herringbone arrangement.

In another embodiment ( 3c ) come grid 14 used, with the grid 14 are either rectangular or square or have other shapes. These grids have a height H in the range of 2 to 30 mm, preferably 5 to 8 mm, and a distance A in the range of 3 to 10 mm, preferably from 4 to 7 mm.

1

forming cylinder

2

screen belt

3

screen belt

4

wrap region

5

suction roll

6

headbox

7

bottom wire

8th

inlet gap

9

deflecting

10

surveys

11

Fibrous suspension

12

burl

13

Stege

14

grid

A

distance

H

height

Claims (9)

Wire section in a machine for producing a paper, board, tissue or other fibrous web from a pulp suspension ( 11 ), which have a headbox ( 6 ) on the wire section with a first ( 2 ) and a second endless sieve belt ( 3 ) is applied, which form a double-wire zone with each other over part of its circumference, and with at least one forming cylinder arranged in the region of the twin-wire zone (US Pat. 1 ), whose lateral surface acts as an outer support surface, wherein at least a part of the support surface of the first screen belt ( 2 ) on its inner surface and the second screen belt ( 3 ) is supported on its outer surface, characterized in that the Formierzylinder ( 1 ) and the second screen belt ( 2 ) supporting a roller from its inner surface ( 9 ) is arranged as a support element. Wire section according to claim 1, characterized in that the roller ( 9 ) has a structured lateral surface. Wire section according to claim 2, characterized in that the roller ( 9 ) on its lateral surface nubs ( 12 ) having. Wire section according to claim 3, characterized in that the nubs ( 12 ) have a height between 2 and 30 mm, in particular between 5 and 8 mm. Wire section according to claim 2, characterized in that the roller ( 9 ) on its outer surface a grid ( 14 ), in particular a rectangular or square grid ( 14 ), having. Wire section according to claim 2, characterized in that the roller ( 9 ) on its lateral surface at the same distance to each other arranged webs ( 13 ), which are each arranged in mutually adjacent rows. Wire section according to claim 6, characterized in that the webs ( 13 ) are arranged in the direction of the fibrous web or transversely to the direction of the fibrous web. having. Wire section according to claim 3, characterized in that the roller on its coat webs ( 13 ) arranged according to a herringbone pattern. Wire section according to one of claims 3 to 8, characterized in that the nubs ( 12 ), the webs ( 13 ) or the grid lines of the grids ( 14 ) Have distances of 3 to 10 mm, in particular from 4 to 7 mm, to each other.