WO2013041769A1

WO2013041769A1 - An arrangement and a method for threading a tail in a fiber web machine

Info

Publication number: WO2013041769A1
Application number: PCT/FI2012/050905
Authority: WO
Inventors: Mikko Hakuli; James Werner
Original assignee: Metso Paper, Inc.
Priority date: 2011-09-23
Filing date: 2012-09-19
Publication date: 2013-03-28
Also published as: FI20115938A0; DE212012000178U1; FI20115938A; FI123613B; CN203904771U

Abstract

The invention relates to an arrangement for threading a tail in a fiber web machine, the arrangement including: Formation means (18) for forming a tail (10) from the fiber web; A cutting device (13) for cutting the tail (10); Tail threading equipment (16) located after a holding point (14) for releasing the tail (10) from the surface of a machine element (12) and transferring forward the tail (10) thus cut; wherein said cutting device (13) is located prior to the holding point (14') preceding said tail threading equipment (16). The cutting device is located in such a way that tail (10) cutting takes place in an unsupported section of the tail (10) between two holding points (14). The invention also relates to a method for threading a tail in a fiber web machine.

Description

AN ARRANGEMENT AND A METHOD FOR THREADING A TAIL IN A FIBER WEB MACHINE

The invention relates to an arrangement for threading a tail in a fiber web machine, the fiber web machine including rotating machine elements adapted to form holding points that create at least one contact with the tail, said arrangement including:

Formation means for forming a tail from the fiber web; A cutting device for cutting the tail;

- Tail threading equipment located after a holding point for releasing the tail from the surface of a machine element and transferring forward the tail previously cut;

wherein the cutting device is located prior to the holding point preceding said tail threading equipment.

The invention also relates to a corresponding method.

US patent No. 5413017 discloses a cutting device based on rotating knife blades, said cutting device being arranged in association with a vacuum belt conveyor. In the arrangement proposed, the tail to be run down is released from the surface of a dryer cylinder, functioning as the machine element, with a doctor, which thus forms the releasing means. After being released, the tail is oriented towards the rotating knife blades using a turning blow plate, whereupon the tail is cut. The turning blow plate thus forms the transfer means. The end of the tail previously cut is transferred forward on a vacuum belt conveyor. At the same time, it is avoided that the part of the tail already guided to broke treatment migrates back to the vacuum belt conveyor. This means that even a thick tail can be cut and transferred forward without folds.

The aforesaid turning blow plate operates slowly and requires a large mounting space. In addition, the transfer of the tail cut between the cutting device and the vacuum belt conveyor is unreliable. This unreliability is also increased by the fact that the tail enters the cutting device slack. Knife blades as such constitute a safety risk particularly during the maintenance operations of the fiber web machine. Thus it is necessary to use protective structures, which complicate the design of the cutting device and may create obstructions as pieces of the tail accumulate between the protective structures and the knife blades .

A common concept in prior art solutions is that cutting and releasing of the tail take place in the same position and often with the same means connected to each other. The holding point refers to, for example, the contact between a roll and the wrap of a fabric or a nip between two rolls, which advances the fiber web as the roll moves. Then, after cutting, slackness is generated in the tail, particularly with fiber webs with high basis weights, as the tail makes a sharp turn due to the cutting operation and the cutting operation slows down the tail travel. A slack tail, on the other hand, is more difficult to guide forward during tail threading and may create unnecessary bags or double ends in the tail. This easily leads to a tail break or dropping of the tail from the tail threading equipment .

The object of the invention is to provide an arrangement and a method for threading a tail in a fiber web machine, which enable the tail to be transferred forward stretched after tail cutting. More precisely, the arrangement according to the invention is characterized in that the cutting device is located in such a way that tail cutting takes place in an unsupported section of the tail between two holding points. More precisely, the method according to the invention is characterized in that the tail is cut prior to the holding point preceding the tail threading equipment in an unsupported section of the tail between two holding points. Thus the tail arriving from the holding point that precedes the tail threading equip- ment can be guided directly further with the tail threading equipment without cutting, thus completely, or at least to a great extent, avoiding generation of a slack tail. It is surprising that the tail can be cut in an open draw prior to the holding point since the tail then remains momentarily without a draw. However, with the method according to the invention, the tail can be transferred stretched to the holding point and further after the holding point.

With the arrangement according to the invention, it is possible to achieve for the tail a route that is almost corresponding to the fiber web travel during normal operating conditions.

The invention is described below in detail by making reference to the enclosed drawings which illustrate some of the embodiments of the invention, in which

Figure 1 is a lateral basic view of an embodiment of the arrangement according to the invention,

Figure 2 is a lateral basic view of a second embodiment of the arrangement according to the invention, Figure 3 is a lateral basic view of a third embodiment of the arrangement according to the invention,

Figures 4a-4b illustrate the shape of the bevel cut of a tail that has been cut with the arrangement and the method according to the invention.

Figure 1 shows the arrangement according to an embodiment of the invention for threading a tail in a fiber web machine. Figure 1 depicts the end of a dryer section 50 and the subsequently located machine calender 52. In the figures, the travel direction of the fiber web is from right to left. The arrangement according to the invention can be used particularly in the dryer section of a fiber web machine but also in the press section or generally in applications in which the use of a tail is required and which include open draws for the fiber web. The purpose of tail threading of a fiber web is to transport a tail 10 of the fiber web and eventually the entire fiber web via the machine elements 12 supporting it as far as to the winder (not shown) . Depending on the application, besides supporting, the machine elements 12 may also dry the fiber web, such as in the dryer section 50, or press the fiber web, such as in the ma- chine calender 52. In this context, machine elements preferably refer to rotating rolls or cylinders. In this context, the fiber web preferably refers to paper or board.

Tail threading usually takes place in specific stages. In other words, the tail is not threaded through the entire machine in one go. Generally the tail and the entire fiber web are momentarily run down t,o the pulper 44 at the end of the various stages, such as at the end of the dryer section 50, as shown in Figure 1. This is to avoid the need of repeating the tail threading operation over the entire length of the fiber web machine if the tail should break before the winder.

As shown in Figure 1, in the dryer section 50, a fabric loop 28 supported by guiding machine elements 12 ' is arranged between the machine elements 12. In this case, the fabric loop refers to a wire fabric arranged as a loop and the guiding machine elements 12' refer to lead rolls. When the wire fabric of the fabric loop 28 and the cylinder functioning as the machine element 12 contact each other, a holding point 14 is created between them. The holding point refers to at least one contact point between the machine element and the fabric loop or alternatively between two machine elements, which carries along with it the fiber web and the tail while the machine element or elements rotate. That is, when the fiber web or the tail is in the contact point between the machine element and the fabric loop or between two machine elements, a holding point is created which carries along with it both the fiber web and the tail towards the rotating direction of the machine element. The arrangement according to the invention includes three basic components. The first component consists of formation means 18 for forming a tail 10 from the fiber web. The second component is a cutting device 13 for cutting the tail 10, and the third component is tail threading equipment 16 for releasing the tail 10 from the surface of a rotating machine element 12 and for 5 transferring the tail 10 thus cut onwards. The formation means 18 can consist of a blade cutter, for example, or a similar device, which is used to separate a tail from the full width fiber web in the travel direction of the fiber web. The width of the tail can be 200 mm, for example. In the embodiments of

10 Figures 1 - 3, the fiber web is a board web, in which case the formation means preferably consist of a blade cutter, because board requires a higher mechanical strength in cutting. The formation means 18 are located prior to the holding point 14¹ preceding the pulper 44; that is, prior to the machine element

15 12 preceding the pulper 44 in the travel direction of the fiber web. More precisely, the formation means are preferably located between the nearest holding point 14' and the second nearest holding point 14" preceding the tail threading equipment 16. In other words, the tail can also be formed in the area of a

20 descending web. Preferably, as in the embodiment shown in the figures, the tail is formed in the upwardly moving fiber web.

The cutting device 13 is a device for cutting the tail 10, said device, according to the invention, being located prior to the

25 holding point 14' preceding the pulper 44;- that is, prior to the machine element 12 preceding the pulper 44 in the travel direction of the fiber web. More precisely, the cutting device 13 is located in such a way that cutting of the tail 10 takes place in an unsupported section 19 of the tail 10 between two

30 holding points 14, in a so-called open draw. Preferably cutting takes place in a draw in which the tail proceeds from a lower machine element 12 to an upper machine element 12; that is, upwards. Preferably the cutting device 13 is located between the machine element 12 preceding the pulper 44 and the nearest

35 machine element 12 preceding the aforesaid machine element 12, in the vicinity of the machine element 12 preceding the pulper 44. According to Figures 1 - 3, the cutting device 13 is always located after the formation means 18 in the travel direction of the fiber web since the tail is formed with the formation means 18. Preferably, both the formation means 18 and the cutting device 13 are located in the same unsupported open draw 19 of the fiber web between two holding points 14. In this context, the expression "unsupported" means that, within this open draw between the holding points, the fiber web and its tail are not supported to a roll, a fabric, or a similar support element, for example. The travel of the tail and the fiber web is only guided by the draw created by the draw point subsequent in the travel direction. After tail cutting, the tail is momentarily guided only by its linear momentum. Tail cutting takes place in the tail transfer area where the tail runs directly towards the holding point located subsequently in the travel direction.

The tail threading equipment 16 can consist of equipment located in association with the machine element 12, which equipment is used to release the fiber web from the surface of the machine element 12 and to transfer it forward to the subsequent holding point 14. The tail threading equipment 16 can include separate releasing means 46, which can be, for example, pick-up blow pipes 36 as shown in Figure 2 or Figure 3, a doctor construction, or a similar prior art solution, which is used to release the fiber web from the surface of the rotating machine element 12 without slowing down the travel of the end of the tail 10, thus preventing generation of slackness. The tail threading equipment 16 can additionally include tail 10 transfer means 26, which can consist of a vacuum belt conveyor as shown in Figure 2, a blow plate, or a simple plate, for exam- pie. The purpose of the transfer means 26 is to transfer the tail 10 released from the machine element 12 further towards the subsequent holding point 14, which can be a nip between the calender rolls or a winder, for example. To carry out the method according to the invention, a tail 10 is formed from the fiber web with the formation means 18. When it is desired to continue tail threading further, the tail 10 is cut with the cutting device 13 prior to the holding point 14 preceding the tail threading equipment 16 in an unsupported section 19 of the tail 10, between two holding points 14. The tail 10 is released from the surface of the machine element 12 and transferred forward with the tail threading equipment 16. In other words, when it is desired to continue tail threading onwards from the pulper 44, the formation means 18 included in the arrangement create a tail in the fiber web which travels via the holding point 14 and the doctor 40 and further to the pulper 44. When the tail 10 extends to the pulper 44, the cutting device 13 cuts the tail 10 whereby the tail 11 preced- ing the holding point enters the pulper 44. The tail 10 subsequent to the cutting point travels unsupported by means of its linear momentum to the holding point 14 which draws the tail 10 further to the tail threading equipment 16. In this application, it is preferable that the doctor 40 is associated with pull-down means (not shown) to guide the web destined for broke treatment and the tail to the pulper. Preferably, the pull-down means consist of a pull-down blow. This pull-down function creates a gap in the position cut as the tail exits from the holding point 14'.

The cutting device used in the arrangement according to the invention is preferably a water cutter, which is used to cut the tail. The water cutter can be adjusted to cut the tail by moving a water jet laterally across the tail. Then, as the tail 10 moves forward, a wedge-shaped bevel cut 56, shown in Figure 4a, is created in the tail 10. The timing of the cutting operation can be such that the tip of the bevel cut just arrives at the holding point when the tail is finally cut off in order to maintain an almost continuous draw in the tail. Water cutting or blade cutting can be used in the method according to the invention .

According to an embodiment, the cutting device has a cutting sequence which controls the water jet in such a way that it moves faster during initial cutting when starting from the first edge of the tail and more slowly when closer to the second edge, in the lateral direction. Thus a blunt 58 wedge, shown in Figure 4b, is created from the bevel cut 56 of the tail 10. After the blunt tip 58, the water jet moves more slowly, whereupon a long edge part 60 is generated. A blunt shape is more resistant in the holding point as regards forces directed to the tail. An advantage of the arrangement and the method according to the invention is that they prevent the tail from remaining slack when transferring it forward. In prior art solutions, tail cutting takes place after the holding point and more precisely, only after the tail has already been released from the surface of the machine element with the tail threading equipment. For the sake of space requirement, the tail threading equipment is thus often located below the shaft of the machine element, the tail to be transferred forward thereby making a sharp turn or even a loop before it can travel further, after cutting, to- wards the subsequent holding point. Slackness is then easily created, which disturbs the tail threading process. In the arrangement according to the invention, cutting takes place already before the holding point, in which case the tail leaving the holding point can be released from the surface of the machine element as soon as possible after the holding point and guided directly and tense to the tail threading equipment and towards the subsequent holding point. The tail threading equipment can be located essentially on the same level with the machine element preceding the tail threading equipment. The expression "essentially on the same level" means that the tail threading equipment is located in the vertical interval between the highest and the lowest surface of the machine element. Thus the tail can be provided with an almost normal travel route according to that of the fiber web during the operation..

5 Figure 2 shows another embodiment of the arrangement according to the invention. This figure clearly illustrates how the tail 10 can be released from the surface of the machine element 12 immediately after the holding point 14, thus making it possible to guide the tail 10 onwards almost directly and with the

10 transfer means 26 included in the tail threading equipment 16, in this case a vacuum belt conveyor, towards the subsequent holding point, which is not shown in this connection. In this embodiment, the releasing means 46 of the tail threading equipment 16 consist of pivoting pick-up blow pipes and a blow plate

15 24; the pick-up blow pipes 36 release the tail 10 from the surface of the rotating machine element 12 by means of an air blow and the blow plate 24 transfers the tail 10 forward. Instead of a blow plate, a conveyor can also be used.

20 Figure 3 shows a third embodiment of the arrangement in which the tail 10 is released from the machine element using pick-up blow pipes 36 included in the tail threading equipment 16. In this embodiment, the pick-up blow pipes 36 are located lower than in the embodiment of Figure 2. However, releasing the tail

25 10 takes place higher than in the prior art solutions, which allows the tail 10 to advance more directly to the subsequent holding point 14, compared to the prior art solutions. In this embodiment, the subsequent holding point 14 is composed of carrier rope sheaves 38 which transfer the tail 10 forward from

30 this point. A carrier rope system can include tail threading ropes 37 and a rope sheave 39, which can be moved to the vicinity of the machine element 12 for the duration of the tail threading process and aside during the normal operation.

35 Figures 1 - 3 illustrate the use of the arrangement in association with a dryer section implemented with a double-fabric run system. In this case, the machine elements 12 are rolls and the holding points 14 are formed between the rolls and the fabric loop. The fiber web travels unsupported in the open draw between the holding points 14. There are two fabric loops: an upper one and a lower one. If the dryer section is implemented as a single-fabric run system, a space can be arranged at the cutting device between the machine elements by means of a loop made for the wire fabric, for example, in which loop the fabric travels via two rolls (not shown), for example. The design can be similar to the solutions that are generally used in prior art fabric loops. Thus a space is provided for the cutting device between the fabric and the fiber web. The arrangement according to the invention is suitable for use in dryer sections that are implemented using either a single-fabric or a double-fabric run system.

Compared to the prior art and the general practice, it is surprising that the tail can be cut prior to the holding point, in an interval between the holding points where the tail is unsupported, in which case the tail remains without draw over a part of the distance. Since the tail also moves at a remarkable speed during tail threading, it has a certain linear momentum which is still maintained after cutting even without momentarily drawing the tail forward. Thus the unsupported tail continues to travel towards the same direction as before the cutting equipment.

The basic components, i.e., the formation means, the cutting device and the tail threading equipment, used in the arrange- ment according to the invention can be similar to prior art equipment, the arrangement thus being simple and affordable to provide .

Preferably, the arrangement and the method are suitable for use in the board production since board folds poorly due to its. stiffness and thus easily remains slack during tail cutting and tail releasing when using prior art methods. In this context, board refers to fiber webs with basis weights exceeding 125 g/m². The arrangement also suits the paper production. The arrangement according to the invention is preferably used in the method according to the invention.

Claims

1. An arrangement for threading a tail in a fiber web machine, the fiber web machine including rotating machine ele- ments (12) adapted to form holding points (14) that create at least one contact with the tail (10), said arrangement including :

Formation means (18) for forming a tail (10) from the fiber web;

- A cutting device (13) for cutting the tail (10);

Tail threading equipment (16) located after a holding point (14) for releasing the tail (10) from the surface of a machine element (12) and transferring forward the tail (10) thus cut;

wherein said cutting device (13) is located prior to the holding point (14') preceding said tail threading equipment (16), characterized in that the cutting device (13) is located in such a way that tail (10) cutting takes place in an unsupported section of the tail (10) between two holding points (14) .

2. An arrangement according to Claim 1, characterized in that said cutting device (13) is located between the nearest holding point (14') and the second nearest holding point (14") preceding said tail threading equipment (16) .

3. An arrangement according to Claim 1 or 2, characterized in that the arrangement is adapted to be used in a dryer section (50) of a fiber web machine.

4. An arrangement according to any of Claims 1 - 3, characterized in that said cutting device (13) and formation means (18) are arranged in the same interval between two holding points (14) .

5. An arrangement according to Claim 4, characterized in that said water cutter (34) is arranged to move laterally for cutting the tail (10) to a wedge shape.

6. An arrangement according to claim 5, characterized in that said water cutter (34) includes a cutting sequence for cutting the tail (10) to a blunt wedge shape.

7. An arrangement according to any of Claims 1 - 6, charac- terized in that the arrangement includes a doctor (40) located after the nearest holding point (14') preceding the tail threading equipment (16) and pull-down means located in association with the doctor (40) for guiding a fiber web manufactured in a fiber web machine and the tail (10) cut from the fiber web from the doctor (40) to a pulper (44) included in the fiber web machine .

8. An arrangement according to any of claims 1 - 7, characterized in that the tail threading equipment (16) included in the arrangement is adapted for transferring the tail (10) to a calender .

9. An arrangement according to any of Claims 1 - 8, character! zed in that the cutting device (13) is located in the section of the tail (10) run advancing directly towards the holding point (14') located subsequently in the travel direction .

10. An arrangement according to any of claims 1 - 9, charac- terized in that the tail threading equipment (16) is located essentially on the same level with the machine element (12) preceding the tail threading equipment (16) .

11. A method for threading a tail in a fiber web machine, the fiber web machine including rotating machine elements (12) adapted to form holding points (14) that create at least one contact with the tail (10) , in which method:

A tail (10) is formed from the fiber web;

The tail (10) is cut;

- The tail (10) is released from the surface of said machine element (12) and transferred further;

characterized in that the tail (10) is cut prior to the holding point (14) preceding said tail threading equipment (16) in an unsupported section of the tail (10) between two holding points (14) .

12. A method according to Claim 11, characterized in that the arrangement according to any of Claims 1 - 10 is used in the method.

13. A method according to Claim 11 or 12, characterized in that the method is used in a dryer section (50) of a fiber web machine .