DE102005000088A1 - Double sieve molding device used in the manufacture of a paper or cardboard material from a fibrous suspension comprises a double sieve path having a horizontal initial dewatering path - Google Patents

Abstract

Double sieve molding device (1) comprises a double sieve path (11) having a horizontal initial dewatering path (13). The double sieve path follows a curved downward path via stationary dewatering elements (12). A pick-up roller (14) detaches the fibrous material from a sieve (3) after subsequent sieving. Preferred Features: The dewatering elements comprise a molding shoe (17), a molding suction unit (18), a wet suction unit (19) and a high vacuum suction unit (20) arranged in the sieve (3) in the sieve running direction.

Description

Such a twin-wire former is known, for example, from the German Offenlegungsschrift DE 39 27 597 A1 known. In the art, this type of twin wire former is referred to as a blade former.

The Dewatering elements arranged in the twin-wire section are in this case placed, designed and operated such that as the last drainage element in the first sieve (lower sieve) a sieve suction roll is provided.

disadvantageous at such use of a suction roll in the area of a twin-wire former the high acquisition and operating costs. The respective acquisition costs in height of about 500 need as well as the operating as well as the at least one reserve roller applied become. moreover designed the extraction of the respective suction roller consuming and thereby causes high operating costs due to increased energy and maintenance costs. additionally does not cause the gutter to double suction cup suction roll insignificant high costs.

Task of invention

Of the Invention is based on the object, in comparison to the known State of the art cheaper To create twin-wire former, however, no disadvantages in terms achievable product quality and runnability.

These Task is inventively characterized solved, that the twin-wire section is a horizontal or nearly horizontal running initial drainage route that has the over the stationary one dewatering elements away extending twin-screen at least predominantly one down curved Course takes that the drainage elements stationary, So are not designed to rotate and that a pickup roller the to be produced fibrous web after sieve separation of the first sieve decreases.

The inventive task is hereby complete solved.

By this twin-wire according to the invention is achieved that the drainage elements a large part the drainage performance take over the now no longer necessary Siebsaugwalze. In doing so, both the product quality as also the runnability compared to a sieve suction roll Twin-wire former not deteriorated. Between the jet injection and the Bahnabnahme is therefore no rotating drainage element.

Of the curved Course of Doppelsiebstrecke represents at noticeably reduced height of Doppelsiebformers also sure that continually the necessary Screen tension to produce a high quality and clear dry fibrous web is present.

In comprise first inventive embodiment the drainage elements at least one forming shoe in the first wire in the machine direction, a Formiersauger, a wet vacuum and after sieve separation arranged high vacuum suction. This combination of drainage elements favored in particular the drainage performance of the twin wire former.

Around the dry content of the fibrous web to be produced before its transfer into to be able to increase a subsequent press section noticeably again, points the high vacuum sucker prefers a vacuum of at least 5,000 Pa up.

Farther is in the second sieve a more extensive drainage elements dehydrator arranged, which has a jet channel, a skimmer and a deflector includes. This will be a maximum possible two-sided drainage the pulp suspension ensured. Preferably, the lies in the second sieve arranged drainage device approximately opposite arranged in the first sieve drainage elements Forming shoe and Formiersauger.

The dewatering elements preferably have Siebführungsflächen with Siebauflagepunkten, each Siebauflagepunkt a maximum normal force of 0.015 N learns.

Moreover, in further preferred embodiments, the two screens have a respective screen tension of greater than or equal to 6 kN / m ² and / or in each case more than 1,200, preferably more than 1,500 screen contact points per cm ² .

Of the Headbox is cheaper Way arranged so that a jet shot into the wedge-shaped Stoffeinlaufspalt with a jet injection angle in the range of +/- 30 ° to the horizontal arises.

Also, the twin-wire former preferably has an operating speed of greater than or equal to 800 m / min, preferably greater than or equal to 1,000 m / min. This will, inter alia, the advantage of a vivid annual production of invented Doppeltelsiebformers achieved according to the invention with a corresponding width of the fibrous web.

1

twin

2

Fibrous suspension

3

First Sieve (lower sieve)

4

second Sieve (upper sieve)

5

First breast roll

6

peripheral region

7

second breast roll

8th

peripheral region

9

Stock inlet gap

10

headbox

11

twin-wire

12

dewatering element

13

initial dewatering section

14

Pickup roll

 15

separation roller

16

suction

17

forming shoe

 18

suction box

19

wet vacuum cleaner

20

High vacuum suction

 21

dehydrator

 22

beam channel

 23

skimmer

24

deflector

25

jet impingement (Arrow)

 26

regulators roll

27

tension roller

28

tension roller

29

drive roller

30

regulators roll

31

deflecting

H

horizontal (Double arrow)

p _U

vacuum

S

wire running (Arrow)

 alpha

Jet impingement angle

Further Features and advantages of the invention will become apparent from the following Description of a preferred embodiment with reference on the drawing.

The single FIGURE shows a schematic side view of the twin-wire former according to the invention 1 for producing a fibrous web, in particular a paper or board web, from a pulp suspension 2 ,

The twin-wire former 1 includes two endless sieves 3 . 4 (Lower sieve, upper sieve), of which the first sieve 3 over a peripheral area 6 a first breast roll 5 runs and the second sieve 4 over a peripheral area 8th a second breast roll 7 running. The second breast roll 7 is substantially perpendicular or slightly offset above the first breast roll 5 arranged.

The two sieves 3 . 4 Run after the expiration of the respective breast roll 5 . 7 forming a wedge-shaped material inlet gap 9 , directly from a headbox 10 the pulp suspension 2 takes up, together. Subsequently, they form at least a twin-wire section 11 holding several drainage elements 12 having.

The twin-wire section 11 has a horizontal or approximately horizontal initial drainage path 13 on. In the area of this initial drainage route 13 no drainage elements are arranged yet. The subsequent via the stationary drainage elements 12 passing double screen 11 At least predominantly takes a downward curved course. In this course, the arranged drainage elements 12 stationary, not designed to be rotating. And finally picks up a pickup roller 14 the fibrous web to be produced after sieve separation from the first sieve 3 from. The sieve separation takes place in a known manner by discharging the second sieve 4 via a separation roller 15 from the one on the first sieve 3 lying fibrous web in the region of a suction device 16 ,

In the illustrated embodiment, the drainage elements comprise 12 in the first sieve 3 in wire direction S (arrow) a forming shoe 17 , a forming sucker 18 , a wet vacuum 19 and a high vacuum cleaner arranged after screen separation 20 which has a negative pressure p _U of at least 5,000 Pa. Of course, depending on the type of fibrous web to be produced even more drainage elements 12 to be available. Also, the order of the mentioned drainage elements 12 to be different.

In the second sieve 3 is a multiple drainage elements 12 comprehensive drainage facility 21 arranged the a beam channel 22 , a skimmer 23 and a deflector 24 includes. This is the drainage device 21 approximately opposite in the first sieve 3 arranged drainage elements 12 forming shoe 17 and Formiersauger 18 ,

The drainage elements 12 have Siebführungsflächen with Siebauflagepunkten, each Sieaufauflagepunkt undergoes a maximum normal force of 0.015 N. In addition, the two sieves 3 . 4 a respective wire tension of greater than or equal to 6 kN / m ² and more than 1,200, preferably more than 1,500 Siebauflagepunkte per cm ² on.

Furthermore, the headbox 10 so on arranges that a jet bullet 25 (Arrow) in the wedge-shaped Stoffeinlaufspalt 9 with a jet injection angle alpha in the range of +/- 30 ° to the horizontal H (double arrow) is formed. The headbox 9 may also have the following features: dilution water control, headbox with lamellae and multi-layer with preferably different qualities of pulp suspensions.

The twin-wire former 1 basically has an operating speed of greater than or equal to 800 m / min, preferably greater than or equal to 1,000 m / min.

The second sieve 4 is after his leadership on the separation roller 15 via a regulator roller 26 and a tension roller 27 to the second breast roll 7 recycled. The first sieve 3 however, after the decrease of the fibrous web to be produced by the pickup roller 14 over a tension roller 28 , a drive roller 29 , a regulator roller 30 and a guide roller 31 to the first breast roll 5 recycled. The rollers 26 to 31 correspond to the arrangement in the illustrated embodiment. Of course, more rollers may be present.

The sieve separation takes place in a known manner by discharging the second sieve 4 via a separation roller 15 from the one on the first sieve 3 lying fibrous web in the region of a suction device 16 ,

In summary It should be noted that by the invention a twin-wire former of the aforementioned type is created, in comparison to known prior art is less expensive, but no Disadvantages in terms of achievable product quality and runnability having.

Claims (10)

Twin wire former ( 1 ) for producing a fibrous web, in particular a paper or board web, from at least one fibrous stock suspension ( 2 ), with two endless sieves ( 3 . 4 ), of which the first sieve ( 3 ) over a peripheral area ( 6 ) a first breast roll ( 5 ) and the second sieve ( 4 ) over a peripheral area ( 8th ) a second breast roll ( 7 ) and the two sieves ( 3 . 4 ) after the expiration of the respective breast roll ( 5 . 7 ) to form a wedge-shaped material inlet gap ( 9 ) directly from a headbox ( 10 ) the at least one pulp suspension ( 2 ), converge and then at least one twin-wire section ( 11 ) forming several drainage elements ( 12 ), characterized in that the twin-wire section ( 11 ) a horizontal or approximately horizontally extending initial drainage route ( 13 ) that via the stationary drainage elements ( 12 ) extending past double-wire section ( 11 ) at least predominantly takes a downwardly curved course that the drainage elements ( 12 ) stationary, so are not rotating and that a pickup roller ( 14 ) the fibrous web to be produced after screen separation from the first sieve ( 3 ) decreases. Twin wire former ( 1 ) according to claim 1, characterized in that the drainage elements ( 12 ) in the first sieve ( 3 ) in the direction of the wire (S) at least one forming shoe ( 17 ), a Formiersauger ( 18 ), a wet vacuum ( 19 ) and arranged after the sieve separation high vacuum suction ( 20 ). Twin wire former ( 1 ) according to claim 2, characterized in that the high vacuum suction device ( 20 ) has a negative pressure (p _U ) of at least 5,000 Pa. Twin wire former ( 1 ) according to one of the preceding claims, characterized in that in the second sieve ( 4 ) a plurality of drainage elements ( 12 ) comprehensive drainage device ( 21 ) is arranged, which a beam channel ( 22 ), a skimmer ( 23 ) and a deflector ( 24 ). Twin wire former ( 1 ) according to claim 4, characterized in that in the second sieve ( 4 ) arranged drainage device ( 21 ) approximately opposite that in the first sieve ( 3 ) arranged drainage elements ( 12 ) Forming shoe ( 17 ) and Formiersauger ( 18 ) lies. Twin wire former ( 1 ) according to one of the preceding claims, characterized in that the drainage elements ( 12 ) Have Siebführungsflächen with Siebauflagepunkten, each Sieaufauflagepunkt undergoes a maximum normal force of 0.015 N. Twin wire former ( 1 ) according to one of the preceding claims, characterized in that the two sieves ( 3 . 4 ) have a respective wire tension of greater than or equal to 6 kN / m ² . Twin wire former ( 1 ) according to one of the preceding claims, characterized in that the two sieves ( 3 . 4 ) each have more than 1,200, preferably more than 1,500 Siebauflagepunkte per cm ² . Twin wire former ( 1 ) according to one of the preceding claims, characterized in that the headbox ( 10 ) is arranged such that a jet shot ( 25 ) in the wedge-shaped substance running gap ( 9 ) with a beam entry angle (alpha) in the range of +/- 30 ° to the horizontal (H) is formed. Twin wire former ( 1 ) according to one of the preceding claims, characterized in that it has an operating speed of greater than or equal to 800 m / min, preferably greater than or equal to 1,000 m / min.