WO2000049225A1

WO2000049225A1 - Cuting device for a tail end

Info

Publication number: WO2000049225A1
Application number: PCT/FI2000/000042
Authority: WO
Inventors: Leo Lunden
Original assignee: Metso Paper, Inc.
Priority date: 1999-02-18
Filing date: 2000-01-20
Publication date: 2000-08-24
Also published as: DE10084218T1; FI104840B; FI990342A0; AU2297100A

Abstract

The invention relates to a method and an assembly for cutting a narrow tail end (WF) formed in a pulp web (W) in the wet end of a pulp-dryng machine, said tial end (WF) travelling along the surface of a felt (17), and said cut tail end (WF) being subsequently expandable to form a standard-width pulp web (W). The method comprises the use of a guide block (1), having a chamfered end portion (4). The guide block (1) is inserted from lateral direction with said chamfered end portion (4) first between the felt (17) and the tail end (WF) travelling on top of it, and the tail end (WF) is lifted off the felt (17) by means of the guide block (1). The tail end (WF) is cut while out of contact with the felt (17).

Description

Cutting device for a tail end

The present invention relates to a method in connection with tail threading for cutting a tail end, said tail end travelling along the surface of a supporting fabric, and said cut tail end being subsequently expandable to form a standard-width pulp web.

The invention relates further to an assembly for cutting a narrow tail end formed in a pulp web in the wet end of a pulp-drying machine, said tail end travelling along the surface of a felt, and said cut tail end being subsequently expandable to form a standard-width puip web.

In particular, the present invention relates to a method for cutting a narrow tail end formed in a pulp web in a pulp-drying machine, said tail end travelling along the surface of a felt, and said cut tail end being subsequently expandable to form a standard-width pulp web.

in a typical pulp machine, the headbox of said puip machine is used for feeding stock onto a wire section, wherein the stock is dewatered such that the resulting pulp web has a dry content of about 20%, and downstream of the wire section the puip web is carried through a press section for increasing the dry content to a value of about 50%. The puip web of the press section, is typically dried in an air drier, wherein the puip web travels through successive tiers from the drier's top portion to its bottom portion, alternately from the forward end of one tier to its rearward end and from the rearward end of a next tier to its forward end, etc. The drainage tiers are constructed by using banks of blow boxes, whereby the blow boxes in each tier are provided with air nozzles which are directed, e.g. towards each other, and the pulp web travels along a path between said face-to-face air nozzles. The pulp web travels typically as an unsupported transfer from the press section to the drier. The feeding of a pulp web from the press section to the drier is assisted by using a narrow tail end cut along the edge of the pulp web upstream of the press section, said tail end being carried by means of a closeable web-feeding ribbon extending alongside the drainage path into the interior of the drier, and typically through the entire drier, prior to expanding the tail end to its full web width. In view of enabling the tail end to be inserted inside the web- feeding ribbon, the tail end must be cut. For example, in the manual feeding of a tail end, this cutting has been implemented by a manually performed snatch-like or jerk-like action.

The application 981449 describes an apparatus for inserting a tail end mechanically inside a web-feeding ribbon and, when using this apparatus, the tail end is cut either by means of a snatch-like action of the apparatus or by using a high-pressure water-jet cutter The cutting of a tail end by snatching results in the formation of an irregular tip in the tail end, and in high-pressure cutting the jet is directed against a tail end travelling along a felt, the felt being also subjected to wear by the jet, which is undesirable. Hence, it is an object of the present invention to provide an improved method and assembly for cutting a tail end, which are capable of accomplishing a desired tip shape for the tail end and which minimize the wearing of a felt in connection with cutting, and said method and assembly being particularly suitable for pulp machines running at a high speed, e.g. more than 200 m/min.

The publication FI 96880 discloses a drawing device for edge trimmings, describing among other things cutting of a tail end However, this device is intended for such a section of a paper machine, wherein the tail end is run freely downwards.

The publication FI 83402 discloses a paper-web cutter for cutting and folding the end of a moving paper web This also requires a freely moving web in order to be functional

In order to achieve the above and other subsequently disclosed objects, a method of the invention is characterized in that, in said method, a tail end travelling along a supporting fabric is lifted off the supporting fabric, and the tail end is cut while out of contact with the supporting fabric According to one preferred embodiment of the invention, there is used a guide block provided with a chamfered end portion, which guide block is inserted with said chamfered end portion first from the lateral direction between a felt and a tail end travelling on top of it, said tail end being lifted off the felt by means of the guide block and said tail end being cut while out of contact with the felt

On the other hand, an assembly of the invention is characterized in that the assembly includes a guide block, which is msertable laterally between a felt and a tail end and which guide block is useful for lifting the tail end off the surface of a supporting fabric, and that the assembly further includes means for cutting the tail end while out of contact with the surface of the felt

The insertion of a guide block laterally between a felt and a tail end travelling on top of it, and the cutting of the tail end, are preferably implemented by an actuator drive, e.g. by means of hydraulic actuators

Hence, the invention enables the cutting of a tail end while carried on a supporting fabric, whereby the cutting does not require an unsupported section for the tail end, nor, on the other hand, is the supporting fabric subjected to wear as a result of the cutting process, and at the same time the tail end is always in a supported condition

A method according to a particular object of the invention is characterized in that there is used a guide block, having at least its end portion chamfered, that the guide block is inserted with said chamfered end portion first in the lateral direction between a felt and a tail end travelling on top of it, that said tail end is lifted off the felt by means of the guide block, and that the tail end is cut while out of contact with the felt

The invention will now be described in more detail with reference made to the accompanying drawings, wherein fig. 1 shows schematically an application of a method and assembly of the invention in connection with tail threading carried out from a press section to a drier in the wet end of a pulp-drying machine,

fig. 2 shows a view similar to fig. 1 with a tail end cut and as the tail end is being inserted inside a web-feeding ribbon,

fig. 3 shows an assembly of the invention in a schematic, enlarged view, prior to the cutting of a tail end,

fig. 4 shows the assembly of fig. 3 after the cutting of a tail end, and

fig. 5 shows a cross-sectional view of a guide block included in the assembly of figs. 3 and 4.

Figs. 1 and 2 illustrate how the method and assembly of the invention are applied for carrying a tail end from a press section 10 to a drier section 11. The press section 10 comprises a frame element 14, 15 and press rolls 12, 13 mounted on the frame element, between which is formed a press nip N, a pulp web being carried through said nip between an upper felt and a lower felt. The lower felt 17 travels through the press nip N and around a guide roll 16, and this felt 17 carries on top of it a pulp web W, which, as the pulp-drying machine is started up, is initially driven down after the press, e.g. to a pulper. This puip web going to the pulper is designated with reference character W_R in fig. 1 . After gaining a sufficient strength, the pulp web W is carried to the drier 11 by providing the pulp web with a narrow tail end W_F by means of a high-pressure water jet or some other type of cutter, located typically upstream of the press nip N, said tail end being guided inside a tail threading ribbon 32 of a tail threading mechanism 30, e.g. by means of a device 18. The tail threading ribbon 32 carries the tail end W_F to the drier 11 under the guidance of rolls 19, 20 and further through the drier, and after this, at the latest, the pulp web is spread or expanded to a standard web width, followed by shutting down the drive of the tail threading ribbon 32, and the pulp web W, driven by the rolls present in the drier, progresses as an unsupported transfer from the press nip N to the top portion of the drier 11. Fig. 2 shows with dashed lines the passage of the pulp web W with a pulp-drying machine in a standard running setup. The tail threading mechanism 30, wherein the tail threading ribbon 32 is opened by means of rolls and remains open downstream of a reverse roll 31 for enabling the passage of a tail end to within the tail threading ribbon, said tail threading ribbon being closed, e.g. by means of guide pins 33, has been described in terms of its operation e.g. in FI Patent 55882, and it is not explained in more detail in this context. The device 18, comprising a preferably perforated follow-up belt 40 and vacuum chambers 41 , 42, has been described in terms of its operation in more detail in FI application 981449 and, thus, neither is that explained in more detail in this context.

The method of the invention involves the use of a guide block 1 , having one end 4, as well as preferably one side thereof, chamfered to facilitate the insertion of the guide block from lateral direction between the felt 17 and the tail end W_F travelling on top of it. This insertion is preferably effected in an actuator-driven fashion, e.g. by means of a hydraulically operated, electrically driven or mechanical actuator (not shown). The guide block 1 is made wedge-shaped 5 in lateral view for achieving to enable a disengagement of the tail end W_F from the felt and, in the embodiment of figs. 3 and 4, it has an articulated joint 6 to provide it with a cutter 2 which is initially in its top position for allowing the tail end W_F to pass through a gap between the top surface of the guide block 1 and the cutter 2. By turning the cutter 2 down in a quick movement, e.g. by using a suitable actuator, the tail end W_F can be cut, and the tail end W_F provided with a new cut end is guided, e.g. onto the top surface of a conveyor 3 or, in case of using a suction belt, onto its bottom surface, as for example in conjunction with the device 18 shown in fig. 1.

Fig. 4 depicts the cutter 2 in its lower position and the cut tail end W_F is guided onto the top surface of the conveyor 3.

Fig. 5 shows in cross-section a guide block 1 , on top of which travels a narrow tail end W_F cut from the pulp web W. The guide block is provided with a chamfered end portion 4 for facilitating the insertion of the guide block between the felt and the tail end to be cut.

Instead of the cutter 2 it is possible to cut the tail end W_F, e.g. by using a high- pressure water jet, which is directed against the tail end W_F as it lies on the top surface of the guide block 1 , whereby the cutting does not damage the felt 17. In view of facilitating the cutting performed by means of a water jet, the top surface of the guide block 1 can be formed with a groove (not shown) extending transversely to the tail end W_F, the water jet being adapted to follow said groove for an easier cutting of the tail end W_F. The groove, and a high-pressure water jet progressing therealong, may extend diagonally across the tail end to form a sharp point after the tail end has been cut for facilitating the insertion of the tail end W_F into the tail threading ribbon 32. Instead of a water jet, it is also possible to use other types of cutting methods and devices.

In the context of this application, the method and assembly are described as applied to carrying a web from a press section to a drier and transferred within the press section on top of a felt, but the solution of the invention is conceivable also elsewhere as regards to tail threading, and the felt can also be replaced with some other type of supporting fabric, such as, e.g. a wire or a so-called transfer belt or the like.

Claims

1. A method in connection with tail threading for cutting a narrow tail end (W_F), said tail end (W_F) travelling along the surface of a supporting fabric (17), and said cut tail end (W_F) being subsequently expandable to form a standard-width pulp web, characterized in that, in the method, the tail end travelling along the supporting fabric is lifted off the supporting fabric, the tail end being cut while out of contact with the supporting fabric

2. A method as set forth in claim 1 , characterized in that there is used a guide block (1 ) provided with a chamfered end portion (4), that the guide block (1 ) is inserted with said chamfered end portion (4) first from the lateral direction between the supporting fabric (17) and the tail end (W_F) travelling on top of it, that the tail end (W_F) is lifted off the supporting fabric (17) by means of the guide block (1 ), and that the tail end (W_F) is cut while out of contact with the supporting fabric

3. A method as set forth in claim 1 , characterized in that the cutting is performed by means of a cutter (2) mounted on the guide block (1 )

4 A method as set forth in claim 3, characterized in that the cutter (2) is linked pivotally (6) to the guide block (1 ), said cutter being initially in its upper position in such a way that the tail end (W_F) travels through between the cutter and the guide block (1 ), and that the cutter is pivoted to its lower position toward the felt (17), thus cutting the tail end (W_F), said tail end (W_F) being then guided onto a conveyor mechanism (3, 16) for carrying the tail end (W_F) to further processing

5. A method as set forth in claim 1. characterized in that the cutting is performed by means of a water jet, which is directed against the tail end (W_F) lying on the top surface of the guide block ( 1 )

6. A method as set forth in claim 5, characterized in that the guide block (1 ) has its top surface formed with a cutting groove and the water jet is directed to follow the cutting groove, said cutting groove contributing to the cutting of the tail end (W_F).

7. An assembly for cutting a narrow tail end (W_F) formed in a pulp web (W) in the wet end of a pulp-drying machine, said tail end (W_F) travelling along the surface of a supporting fabric (17), and said cut tail end (W_F) being subsequently expandable to form a standard-width pulp web (W), characterized in that the assembly includes a guide block (1 ) insertable laterally between the felt (17) and the tail end (W_F), and said guide block being useful for lifting the tail end (W_F) off the felt surface, and that the assembly further includes means (2) for cutting the tail end (W_F) while it is out of contact with the felt surface.

8. An assembly as set forth in claim 7, characterized in that the guide block comprises an elongated, cross-sectional ly (5) wedge-shaped member (1), having an end portion (4) which is chamfered for an easier insertion of the guide block between the felt (17) and the tail end (W_F).

9. An assembly as set forth in claim 7 or 8, characterized in that the cutting means comprise a cutter (2), which is mounted pivotally (6) on the guide block (1 ) and which is up in its initial position, such that the tail end (W_F) is passable through between the cutter and the guide block (1 ), and said cutter being pivotable to its lower position toward the felt (17) for cutting the tail end (W_F).

10. An assembly as set forth in claim 7 or 8, characterized in that the cutting means comprise a water jet, which is transferable across the tail end (W_F) for cutting the tail end (W_F) while the tail end (W_F) lies on the top surface of the guide block.

11. An assembly as set forth in claim 10, characterized in that the cutting means further comprise a cutting groove, formed in the top surface of the guide block and extending transversely to the tail end (W_F), the water jet being guidable to progress along said cutting groove.

12. A method for cutting tail end a narrow tail end (W_F) formed in a puip web (W) in a pulp-drying machine, said tail end (W_F) travelling along the surface of a felt (17), and said cut tail end (W_F) being subsequently expandable to form a standard-width puip web, characterized in that there is used a guide block (1 ), having at least its end portion (4) chamfered, that the guide block (1 ) is inserted laterally with said chamfered end portion (4) first between the felt (17) and the tail end (W_F) travelling on top of it, that the tail end (W_F) is lifted off the felt (17) by means of the guide block (1 ), and that the tail end (W_F) is cut while out of contact with the felt (17).