Twin wire former

• US 20040069430A1
• Filed: 01/02/2002
• Published: 04/15/2004
• Est. Priority Date: 05/02/2000
• Status: Active Grant

• Current Assignee: Voith Patent Gmbh (Voith GmbH & Co. KGaA)
• Original Assignee: Voith Paper Patent GmbH (Voith GmbH & Co. KGaA)
• Inventors: Bubik, Alfred, Henssler, Joachim, Stelzhammer, Franz, Prossl, Jurgen
• Granted Patent: US 6,875,309 B2
• Time in Patent Office: Days
• US Class Current: 162/301
• CPC Class Codes: D21F 9/003 of the twin-wire type

Abstract

The invention relates to a twin wire former (1) for producing a fibrous web (4), in particular a paper, cardboard or tissue web, from a fibrous suspension according to the generic terms claim 1. The twin wire former (1) is characterized in that, the two wire belts (2, 3) run upwards after a passing a first deviation device (10), forming an angle (β) relative to an imaginary second horizontal plane (H2), in such a way that the upper vertex (15.SO) of the second deviation device (15) lies above the lower vertex (10.SU) of the first deviation device (10), and that the angle (δ) relative to the imaginary first horizontal plane (H1) runs downwards.

Claims

1. A twin-wire former (1) for producing a fibrous web (4), in particular a paper, board or tissue web, from a fibrous stock suspension, having the following features:

a) two endless wire belts (lower wire (2) and upper wire (3)) together form a twin-wire zone (5);

b) in a first section of the twin-wire zone (5), in which the two wire belts (2, 3) run over a dewatering element in the form of a rotating forming roll (7), the two wire belts (2, 3) together form a wedge-like inlet gap (8) which picks up the fibrous stock suspension directly from a flowbox (9) fitted at an angle (δ

) relative to an imaginary first horizontal plane (H1) (“

gap former”

);

c) in a second section of the twin-wire zone (5), the two wire belts (2, 3) with the fibrous web (4) forming between them run downward over further dewatering elements (6) at an angle (α

) of 10°

to 60°

relative to an imaginary first vertical plane (V1);

d) at the end of the second section of the twin-wire zone (5), the two wire belts (2, 3) run over a first deflection device (10) with a lower vertex (10.SU) and then over at least one separating device (11) which acts over the machine width and in the area of which one of the wire belts (2, 3) is led away from the forming fibrous web (4) and the other wire belt (2, 3);

e) a second deflection device (15) with an upper vertex (15.SO) is arranged after the separating device (11) and deflects the wire belt (2) that carries the forming fibrous web (4);

characterized

f) in that after the first deflection device (10), the two wire belts (2, 3) run upward at an angle (β

) relative to an imaginary second horizontal plane (H2) in such a way that the upper vertex (15.SO) of the second deflection device (15) is located above the lower vertex (10.SU) of the first deflection device (10), and

g) in that the angle (δ

) runs downward relative to the imaginary first horizontal plan (H1).

2. The twin-wire former (1) as claimed in claim 1,

characterized in that

the upper vertex (15.SO) of the second deflection device (15) is located at least 50 mm, preferably at least 100 mm, in particular at least 200 mm, above the lower vertex (10.SU) of the first deflection device (10).

3. The twin-wire former (1) as claimed in claim 1 or 2,

characterized in that

the angle (δ

) assumes a value between 0° and

45°

, preferably between 0° and

30°

.

4. The twin-wire former (1) according to the preamble of claim 1,

characterized

f) in that after the first deflection device (10), the two wire belts (2, 3) run upward at an angle (β

) relative to an imaginary second horizontal plane (H2),

g) in that a felt (23) removes the forming fibrous web (4) from the wire belt (2) at a pickup point (S_p), which is located above the lower vertex (10.SU) of the first deflection device (10), and

h) in that the pickup point (S_p) is followed by a press unit (24), in which the forming fibrous web (4) is guided first through a first, preferably double-felted press nip (25) with a first press roll (26) and a second press roll (27), after the first press nip (25) is guided, with one of the felts (23), around the first press roll (26), is then transferred to a non-felted press roll (29) in a second press nip (28) and then runs through at least one further single-side-felted press nip (30).

5. The twin-wire former (1) as claimed in claim 4,

characterized in that

the pickup point (S_p) is located at least 50 mm, preferably at least 100 mm, in particular at least 200 mm, above the lower vertex (10.SU) of the first deflection device (10).

6. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the angle (β

), at which the two wire belts (2, 3) run upward in relation to an imaginary second horizontal plane (H2) after the first deflection device (10), assumes a value between 10° and

90°

, preferably between 25° and

40°

.

7. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

isobaric dewatering elements (18, 19), as they are known, are arranged between the first deflection device (10) and the separating device (11), between which the forming fibrous web (4) runs, enclosed between the two wire belts (2, 3).

8. The twin-wire former (1) as claimed in claim 7,

characterized in that

at least one stationary isobaric dewatering element (18) is arranged on the one wire belt (2, 3), and at least one isobaric dewatering element (19) is arranged on the other wire belt (2, 3) and can be set resiliently against the wire belt (2, 3) by means of a selectable force.

9. The twin-wire former (1) as claimed in claim 7 or 8,

characterized in that

the isobaric dewatering elements (18, 19) are designed as plates or as plate segments.

10. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

after the separating device (11), there is arranged at least one flat suction element (20), which acts on the wire belt (2) which carries the forming fibrous web (4).

11. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

at the second deflection device (15), deflection of the wire belt (2) is carried out in such a way that the wire belt (2) subsequently runs downward at an angle (γ

) less than 60°

, preferably less than 40°

, in particular less than 25°

, relative to an imaginary second vertical plane (V2).

12. The twin-wire former (1) as claimed in one of claims 1 to 10,

characterized in that

at the second deflection device (15), deflection of the wire belt (2) is carried out in such a way that the wire belt (2) subsequently runs substantially horizontally.

13. The twin-wire former (1) as claimed in claim 12,

characterized in that

the wire belt (2) runs over the lower vertex (10.SU) of the first deflection device (10).

14. The twin-wire former (1) as claimed in claim 13,

characterized in that

the wire belt (2) runs at least 50 mm, preferably at least 100 mm, above the lower vertex (10.SU) of the first deflection device (10).

15. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

a further sheet forming device (22), preferably a hybrid former, is arranged after the second deflection device (15).

16. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the second deflection device (15) is a suction roll (13), a shoe (21) with foils or a shoe with foils and with applied vacuum.

17. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the distance (A) between the lower vertex (10.SU) of the first deflection device (10) and the upper vertex (15.SO) of the second deflection device (15) assumes a value between 1 and 8 m, preferably between 3 and 6 m.

18. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the first deflection device (10) is a closed roll (16), an open roll or an open roll with applied vacuum.

19. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the separating device (11) is designed as a suction separator (17) and/or as a vacuum shoe.

20. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the forming roll (7) has a diameter (D7) of greater than 1200 mm, preferably greater than 1635 mm, in particular greater than 1760 mm.

21. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the forming roll (7) has a dewatering capacity which has a value of at least 50%, preferably of at least 65%, of the total dewatering capacity of the twin-wire former (1).

22. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the forming roll (7) is designed as an open roll.

23. The twin-wire former (1) as claimed in claim 22,

characterized in that

the open forming roll (7) is closed by means of a grille or honeycomb structure.

24. The twin-wire former (1) as claimed in claim 22,

characterized in that

the open forming roll (7) is a suction roll.

25. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

the roll diameter (D16) of the deflection roll (16) is greater than the roll diameter (D7) of the forming roll (7) and/or the roll diameter (D13) of the suction roll (13).

26. The twin-wire former (1) as claimed in one of the preceding claims,

characterized in that

it has an overall height (H) in a range from 2 to 8 m, preferably from 3 to 6 m.

27. Use of the twin-wire former (1) as claimed in one of the preceding claims, in particular in a former rebuild.