Device and method for transferring a strip of a web

Abstract

The invention relates to a device and a method for transferring the tail of a web from a first clothing to a second clothing. It is characterised in that the tail is transferred in a first, short open draw from the first clothing to the second clothing. This enables automatic web transfer requiring significantly less space and with equipment of low complexity.

Claims

1. A method for transferring a tail (1) of a pulp web (2) from a first clothing (14) to a second clothing (13) in a first open draw (9) in a machine (10) for production of the pulp web, comprising steps of guiding the tail cut from the pulp web through at least one press nip, after the at least one press nip, transferring the tail of the pulp web in the first open draw to the second clothing, moving the tail (1) onwards with the second clothing (13) with the tail (1) being guided on the second clothing (13) to a second area (19), carrying the tail (1) in the second area (19) between the second clothing (13) and a third clothing (15), wherein the tail (1) and a remaining section of the pulp web (2) are carried together on the first clothing (14) through the at least one press nip (5) between a suction press roll (4) and at least one other roll (6) to mechanically dewater the tail and the remaining pulp web in the at least one press nip (5), carrying the tail (1) onwards on the first clothing (14) while the remaining pulp web (2) follows a clothing of the other roll (6) to a broke area, wherein the second clothing (13) is a felt, and the third clothing (15) is a felt or impermeable belt.

2. The method according to claim 1, wherein a jet from a pneumatic nozzle (8) acts upon the first clothing (14) after the open draw (9), the jet acting in a cross-machine area of the first clothing (14), where the tail is carried on the first clothing (14) before the open draw (9).

3. The method according to claim 1, wherein the tail (1) is subjected to suction through the first clothing (14) between the press nip (5) and the open draw (9).

4. The method according to claim 1, wherein at least the tail (1) is subjected to suction through the second clothing (13) after the open draw (9).

5. The method according to claim 4, wherein suction is applied to the second clothing (13) indirectly by a suction box (12) after the open draw (9).

6. The method according to claim 5, wherein the second clothing (13) is guided over a roll (11) after the open draw (9), the roll (11) is selected from a grooved roll (11) with grooves or a perforated roll (11), and the suction box (12) applies suction directly to the grooves in the grooved roll (11) or directly to the perforated roll (11), thereby indirectly applying suction to the second clothing (13) by the suction box (12).

7. The method according to claim 1, wherein at least a portion of the tail (1) is subjected to suction through the second clothing (13) after the open draw (9) and before the second area (19).

8. The method according to claim 7, wherein the second clothing (13) is guided over a suction box (12) between the open draw (9) and the second area (19) and suction is applied to the second clothing (13) by the suction box (12).

9. The method according to claim 1, wherein the tail (1) cut out of the pulp web (2) is widened when it has passed through the second area (19) and the full pulp web is guided through the second area (19) after widening.

10. The method according to claim 1, wherein the pulp web (2) comprises primarily pulp and has a basis weight of more than 450 g/m.sup.2.

11. The method according to claim 1, wherein the tail (1) is cut over its entire width across a machine running direction before the open draw (9).

12. A machine (1) for production of a pulp web with a device for transferring a tail (1) of the pulp web (2), comprising: a first clothing (14) and a second clothing (13), the first clothing carrying the tail cut from the pulp web through at least one press nip formed between a suction press roll and at least one other roll, an open draw (9) for transferring the tail (1) from the first clothing (14) to the second clothing (13), a roll (11) for guiding the second clothing (13) after the open draw (9), and a jet from a pneumatic nozzle (8) that can be directed onto the first clothing (14) after the open draw, the jet being disposed in a cross-machine area of the first clothing (14), wherein the tail (1) is carried on the first clothing (14) before the open draw (9), the tail (1) and the remaining pulp web (2) can be carried together on the first clothing (14) through the at least one press nip (5), the tail (1) can be carried onwards on the first clothing (14) and the remaining pulp web (2) can be carried onwards on a clothing of the other roll (6) to a broke area.

13. The machine according to claim 12, wherein the roll (11) is a grooved roll with grooves or a perforated roll (11), the second clothing is a felt, and suction can be applied indirectly to the second clothing (13) after the open draw (9) at least at a portion of the tail (1) by a suction box (12) applying suction directly to the grooves in the grooved roll (11) or by the suction box (12) applying suction directly to the perforated roll (11).

14. The machine according to claim 12, wherein the first clothing (14) is wrapped around the suction press roll (4) and the suction press roll (4) has at least one suction zone for applying suction to the first clothing (14) in an area after the press nip (5), and the second clothing (13) is guided over a suction box (12) after the open draw (9) and the suction box (12) can apply suction to the second clothing (13) in an area of the tail (1).

15. A machine for production of a pulp web having a basis weight of more than 450 g/m.sup.2 in a manner that allows automatic transfer of a tail of the pulp web, the machine comprising: at least one press nip formed between a suction press roll and at least one other roll and being arranged to dewater the tail cut from the pulp web, a first clothing carrying the tail cut from the pulp web having a basis weight of more than 450 g/m.sup.2 through the at least one press nip, an open draw arranged after the at least one press nip and for transferring the cut tail from the first clothing to a second clothing, said open draw being defined by a gap between the first clothing and the second clothing whereby the first clothing and the second clothing do not touch one another and the pulp web is not supported and is guided freely, a roll for guiding the second clothing after the open draw, and a pneumatic nozzle directing a jet onto the first clothing after the open draw, the jet being disposed in a cross-machine area of the first clothing.

16. The machine according to claim 15, wherein the roll is a grooved roll with grooves or a perforated roll, the second clothing is a felt, and suction can be applied indirectly to the second clothing after the open draw at least at a portion of the tail by a suction box applying suction directly to the grooves in the grooved roll or by the suction box applying suction directly to the perforated roll.

17. The machine according to claim 15, wherein the second clothing moves at a different speed than the first clothing.

18. The machine according to claim 15, wherein the second clothing moves at a greater speed than the first clothing.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

(1) The invention will now be described using the examples in the drawings.

(2) FIG. 1 shows a machine for production of a pulp web according to the state of the art.

(3) FIG. 2 shows an embodiment of the disclosed device with a short open draw for transferring a tail.

(4) FIG. 3 shows an embodiment of the disclosed suction box for applying suction directly to a roll and indirectly to the second clothing.

DETAILED DESCRIPTION

(5) FIG. 1 shows an overview of the sheet forming unit and the press section of a machine 10 for production of a pulp web according to the state of the art. The sheet forming unit for forming the sheet 2 is designed as a twin-wire dewatering unit and the press section is designed with a first press unit 6 and a subsequent press unit 7. Other units coming after the machine are not shown. In accordance with the open draw between the first press unit 6 and the subsequent press unit 7, a tail 1 of the web 2 is transferred first of all and then widened to the machine width. An endless woven clothing 14 of the first press unit 6 and the endless woven clothings 13 and 15 of the subsequent press unit 7 are also shown. According to FIG. 1, the web 2 runs from left to right.

(6) FIG. 2 shows the disclosed device and illustrates the method for transferring the tail 1. Here, the tail 1 is cut from the web 2 in the first press unit 6 before the press nip 5, and the tail 1 and the remaining web 2 are guided through the press nip 5 on the first clothing 14. The remaining web 2 is removed from the first clothing 14 after the press nip 5 and runs into a broke area or broke container (not shown). The tail 1 is carried onwards on the first clothing 14 round the suction press roll 4, enabling suction to be applied to the first clothing 14, at least in the area of the tail 1, by the suction press roll 4, at least after the press nip 5. The tail 1 is transferred from the first clothing 14 to the second clothing 13 in an open draw 9, the second clothing 13 being guided over a roll 11, which is designed as a grooved roll 11 or as a perforated roll 11. Here, the roll 11 enables suction to be applied to the second clothing 13, at least in the area of the tail 1. During transfer, the jet from the nozzle 8 acts on the first clothing 14, at least for a short time, the jet from the nozzle 8 acting at least in the cross-machine area of the first clothing shortly after the open draw 9 (as shown in FIG. 2), where the tail 1 is carried on the first clothing 14 before the open draw. After the open draw 9 and before the second area 19, the clothing is guided over a suction box 12, where suction is applied to the second clothing 13 by the suction box 12, at least in the area of the tail. The suction box 12 furthermore enables suction to be applied indirectly to the second clothing 13 after the open draw 9, the suction box 12 applying suction to the roll 11, which is designed as a grooved roll 11 or perforated roll 11, directly round the circumference. The second area 19 is characterised by the third clothing 15 being placed on the second clothing 13 carrying the tail 1. The jet of the water nozzle 16 can act on the second clothing 13, acting in a cross-machine area of the second clothing 13, where the tail 1 is carried on the second clothing 13 after the open draw 9. Due to the jet of the water nozzle 16, the second clothing 13 can be saturated with water in the effective range of the jet during transfer, increasing the smoothness of the second clothing 13 on the web side and reducing the permeability of the second clothing 13. When the tail 1 has been guided successfully through the second area 19, transfer of the tail 1 is complete, the tail subsequently being widened. After widening, the tail 1 has the full width of the web 2, the web 2 being guided through the press nip 5 and the entire web 2 onwards over the suction roll 4 on the first clothing 14. After the press nip 5, suction can be applied to the web 2 through the first clothing 14 by the suction roll 4. In accordance with the open draw, there is a gap between the first clothing 14 and the second clothing 13, i.e. they do not touch one another, and the web 2 is transferred freely from the first clothing 14 to the second clothing 13. The advantage of an open draw is, in particular, the option of different speeds between the first clothing 14 and the second clothing 13, whereby, the speed of the clothings in machine direction remains the same or increases. After widening, the second clothing 13 has either the same speed as or a higher speed than the first clothing 14. As the speed increases in machine direction, elongation of the web can be compensated, thus preventing bubbles or streaks from forming.

(7) FIG. 3 shows the roll 11, which can be designed as a grooved roll 11 or a perforated roll 11, suction being applied to the roll 11 directly around the circumference by the suction box 12. The grooves 17 in the roll 11 or, alternatively, the perforated suction width 17 of the roll 11 is shown in FIG. 3. During transfer of the tail 1, it is an advantage if suction is applied to the second clothing 13, at least in the area of the tail. The suction box 12 can be designed with a separate edge zone 18 in order to concentrate the application of suction on the area of the tail 1 during transfer of the tail 1. After widening, it can be an advantage to apply suction over the entire width of the web 2 in order to secure the web 2 more effectively on the second clothing 13 and prevent bubbles and streaks from forming.

(8) The present invention thus offers advantages over conventional transfer devices. In addition to automatic web transfer without touching the web by hand and the resulting improvement in industrial safety, the invention enables automatic transfer in a very small space with an overall reduction in mechanical engineering complexity.