DE10341448A1 - Papermaking assembly directs fibre suspension into closing gap between two sieve belts under a water jet baffle plate - Google Patents

Abstract

A papermaking assembly has a forming drum (1) in contact with a first sieve belt (2) that advances around the drum mantle to a gusset gap (8) where it is joined by a second sieve belt (3). A headbox jet injects a fibre suspension into the closing gap between the two belts (2, 3). Surplus water passing through the outer sieve (3) is returned by a curved baffle plate (10) hanging from a pivot (11). The baffle plate slides or hangs on the pivot in response to water pressure and has a foil water guide.

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 form a twin - wire zone, with at least one in the region of Double-screen zone arranged forming cylinder, whose lateral surface acts as an outer support surface, wherein at least a part of the support surface the first screen belt on the inner surface and the second screen belt is supported on its outer surface, and with a forming agent, which ejects a fluid against the inside of the second screen belt, the the pulp suspension is opposite.

A Wire section in a machine for producing a fibrous web comprises a headbox, by means of which a pulp suspension between two powered sieves is ejected. The pulp suspension is passed through the sieves to form a fibrous web dehydrated at least until the immobilization of the fibers. The pulp suspension is through the headbox into a formed by the two sieves Gap introduced. Therefore, such twin wire formers are also referred to as gap formers.

at the drainage it depends on the formation of the finished fibrous web too influence. In the case of a paper web, this is called formation the appearance of a sheet of paper held against light. It is judged how evenly the fibers in the finished Paper web are distributed. A "bad formation," that is, a piece of paper with "cloudier Review " caused by the fact that in the formation of a web in the former in the still liquid Fiber suspension "flakes", i.e. unwanted fiber aggregates, form. To avoid this or to the resulting flakes again dissolve, So in order to achieve a good formation, screening sections generally have formulating agents which attack the sieve or both sieves. As a formulating agent For example, moldings are known. Such moldings are at intervals arranged in the tape running direction one behind the other transversely to the direction of tape travel. Between the moldings therefore remain unaffected areas. As rigid moldings to profile disturbances in the fibrous web to lead, In a twin-wire former, the forming strips elastically one of the two sieves pressed. As a result, learns between the sieves on the Series of moldings running pulp suspension pressure pulses, Loosen or dissolve the possibly formed fiber flakes and in the finished fibrous web for to provide a good formation. Alternatively to the strips can be also roller blades or convex curved Insert forming shoes.

From the DE 198 03 451 A1 Such a wire section is known in which the forming means comprise at least one fluid ejector which ejects a fluid against the side of a screen opposite the pulp suspension. As a result, a pressure is exerted against the sieve, which is similar to the effect conventional, compliant Formierleisten. As a result, the fibrous suspension moving stationary between two sieve belts undergoes pressure pulses, whereby flakes are dissolved and the formation of the finished fibrous web is improved. In addition, the formation achieved hereby softer than with the yielding molded moldings. Since the mechanical contact between Sieboberfläche and the Formierleiste deleted, the Siebverschleiß is significantly reduced. The fluid is irradiated onto the screen at an angle between 10 ° and 90 ° to produce the desired pressure pulses in the pulp suspension.

It The object of the invention is another simple way to improve the formation in a fibrous web.

According to the invention this Task with a wire section of the type mentioned solved in that the forming means comprises a deflecting element, that of the headbox radiated and passed from the second screen belt white water jet towards the lateral surface of the Deflects forming cylinder back.

The invention reduces the energy required to produce the jet of fluid directed against the forming roll. In addition, disturbances in the paper web are prevented by air impact as well as by the decrease in the gap strength and an increase in porosity. It is particularly advantageous that the white water, which carries the pulp suspension, can be reused directly by being deflected in its direction against the sieve. Thus, it is not necessary to use another fluid, as according to the DE 198 03 451 A1 is provided. In contrast to the known solution is saved by the elimination of the nozzle for the fluid space. This results in significantly lower investment and operating costs. In addition, the susceptibility to interference is eliminated by the clogging of the nozzle. Changes in the angle of incidence of the white water jet can also be achieved more easily than with the nozzle.

Preferably, the pulp suspension is ejected machine width; it is, however conceivable to provide or use them only pointwise or in sections, for example, to compensate for the inadequacy of other Formiermittel at these points, which occur due to aging or manufacturing tolerances. An example of this are discontinuities in the sieve thickness. Preferably, the device also has control means to influence the formation of the pulp suspension across the width. For this purpose, for example, adjusting devices are provided, which adjusts the deflecting element as a whole or in sections.

Further Benefits emerge from the subclaims, the description and the drawings.

From It is particularly advantageous if the deflecting element as a whole or is arranged slidably or pivotally in parts. By the deflection, the water is deflected against its direction and shot at the forming cylinder.

In An advantageous development is the function of the deflecting element supported by that a film holder and / or a baffle for guiding the white water jet is available.

A special effectiveness of the deflecting element is achieved when the Film holder a single film or a plurality next to each other picks up arranged foils. The slides can also be sectioned individually adjust. By using the floating on the screen Foils are avoided by the not completely closed Siebwasserstrahl Air enters the suspension between the sieves.

From Advantage is a further embodiment of the invention, according to the Film or the films clamped in the film holder or by a screw is or will be held.

Advantageous It is also when the film or the films on her, the Formierzylinder facing end is bent in the direction of the filter belts or are. This will give a well controllable influence on the formation through the white water jet allows.

With Advantage is the distance between the film holder with the machine stopped and the sieve without suspension between the sieves 6 to 40 mm, in particular 10 to 15 mm.

In a further advantageous form of the invention consists or exist the film or the films of a flexible material.

Also is the angle of incidence with respect to the tangent to the support surface preferably adjustable. It is between 0 ° and 90 °, preferably between 15 ° and 45 °. He can be over the Machine width preferably by means of the deflecting plate and / or the Adjust the film holder assigned zoning screws also in zones.

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 a variant of the arrangement 1 and

3a , b Detailed views of foils in a foil holder.

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.

Both screen belts 2 . 3 walk in the immediate vicinity of a headbox 5 with a headbox optionally equipped with lamellae 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. From the headbox nozzle 6 Pulp suspension flows at a rate of, for example, 900 m / min or more into the inlet gap 8th , As stored at the greater part of the pulp suspension between the sieve belts 2 . 3 down while a white water jet 9 through the sieve belt 3 passes.

On the inside of the screen belt 3 is a baffle 10 attached, that through the screen belt 3 passing through white water jet 9 towards the forming cylinder 1 deflects. For example, by a joint 11 attached swivel mechanism is the deflection sheet 10 movable, so that the angle under which the white water jet 9 on the wrap area 4 is deflected, is changeable. In addition, the white water jet 9 through a foil holder 12 steered, the below the concave inside of the baffle 1O is arranged.

In a variant ( 2 ) of the arrangement 1 is a Siebwasserleitblech 13 available. On its concavely curved inner surface of the plurality of jet surfaces condenses 9.1 having white water jet 9 to a narrow beam, which at a sharp angle of incidence α on the two screen belts 2 . 3 in the wrap area 4 impinges and influences the fibrous suspension passed between them in such a way that flocculation is avoided and a uniform paper structure is produced.

Below the Siebwasserleitblechs 13 and on the bottom of the compressed white water jet 9 is the foil holder 12 who is a shell 14 and a lower part 15 between which either a single, preferably over the entire width of the machine extending film 16 or a plurality of side-by-side foils 16 is held.

The foil 16 is between the shell 14 and the lower part 15 either clamped or bolted. Preferably by pivoting away and / or additional lifting of the baffle 9 or the Siebleitblechs 13 becomes the foil holder 12 accessible to the slides 16 exchange. Alternatively, these can also be laterally through the slot between the upper part 14 and the lower part 15 Push.

The slides 16 are either flat and become when their projecting towards the wrap area length is greater than the distance between this and the film holder 12 bent. Alternatively, the slides 16 angled forward ( 3a ). The distance between the film holder is 12 with the machine stopped and the sieve 3 without suspension between the sieves 2 . 3 6 to 40 mm, in particular 10 to 15 mm. Or the slides 16 already have as such a forward curved shape, as in 3b is shown.

The slides 16 consist of either a plastic or a thin sheet metal. Preferably, they are bendable.

In addition to an adjustability of the baffle 10 over the joint 11 or the Siebwasserleitblechs 13 about a joint 17 is preferably also the film holder 12 about a joint 18 adjustable, so that the angle of incidence of the white water jet 9 on the wrap area 4 can be adjusted in a larger angle range.

Instead of the foil holder 12 can be arranged at this point, a preferably also pivotable baffle.

1

forming cylinder

2

screen belt

3

screen belt

4

wrap region

5

headbox

6

headbox

7

deflecting

8th

inlet gap

9

Siebwasserstrahl

9.1

beam area

10

baffle

11

joint

12

foil holder

13

Siebwasserleitblech

14

top

15

lower part

16

foil

17

joint

18

joint

α

angle of impact

Claims (8)

Sieve section in a machine for producing a paper, board, tissue or other fibrous web from a pulp suspension, which has a headbox ( 6 ) on the wire section with a first ( 2 ) and a second endless sieve belt ( 3 ) is applied, which form with each other on a part of its circumference a twin-wire zone, with at least one forming cylinder arranged in the region of the double-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, and with a forming agent, the fluid against the inside of the second screen belt ( 3 ) which opposes the fibrous suspension, characterized in that the forming agent comprises a deflecting element ( 10 . 13 ), which separates the from the headbox ( 6 ) and from the second screen belt ( 3 ) passed through white water jet ( 9 ) in the direction of the lateral surface of the forming cylinder ( 1 ). Wire section according to claim 1, characterized in that the deflecting element ( 10 . 13 ) is arranged as a whole or in parts displaceable or pivotable. Wire section according to claim 1 or 2, characterized in that the deflecting a baffle ( 10 . 13 ) and / or a film holder ( 12 ) for guiding the white water jet ( 9 ). Wire section according to claim 3, characterized in that the film holder ( 12 ) a single film ( 16 ) or a plurality of juxtaposed foils receives. Wire section according to claim 4, characterized in that the film ( 16 ) or the films in the film holder ( 12 ) or held by a screw or is. Wire section according to claim 4 or 5, characterized in that the film ( 16 ) or the films at their the Formierzylinder ( 1 ) facing end in the running direction of the screen belts ( 2 . 3 ) is bent or are. Wire section according to claim 6, characterized in that the distance between the film holder ( 12 ) with the machine stopped and the sieve ( 3 ) without suspension between the sieves ( 2 . 3 ) Is 6 to 40 mm, in particular 10 to 15 mm. Wire section according to one of claims 4 to 7, characterized in that the film ( 16 ) or the films consists of a flexible material or exist.