Patent ID: 12234606

DETAILED DESCRIPTION OF VARIOUS EMBODIMENTS

With reference toFIG.1, an embodiment of a common concept for tissue paper making machines is shown. The machine1ofFIG.1comprises a forming section2that includes a head box5that receives stock from stock headers14through conduits/tubes15. InFIG.1, two stock headers14are shown but it should be understood that this is just an example and that there could be more than two stock headers or only one stock header. The head box5is arranged to inject stock into a gap8between a first forming fabric6and a second forming fabric7. The second forming fabric7is suitably a foraminous wire that runs in a loop supported by lead rolls20. The first forming fabric6is usually a felt that is capable of absorbing water but may conceivably also be a wire. The first forming fabric6runs in a loop supported by lead rolls20. The forming section also comprises a forming roll4and a fibrous web is formed from the stock that is injected into the gap8between the forming fabrics6,7. The first forming fabric6is arranged to carry the newly formed fibrous web to a nip formed between a press roll9and a Yankee drying cylinder3, i.e. the first forming fabric6not only forms a loop in which the forming roll4is located but also carries the newly formed fibrous web all the way to the Yankee drying cylinder3such that the fibrous web W is transferred to the outer surface of the Yankee drying cylinder3directly from the first forming fabric6. The forming section2ofFIG.1is designed as a crescent former. The press roll9may conceivably be a shoe roll arranged to cooperate with the Yankee drying cylinder3such that the nip between the press roll9and the Yankee drying cylinder3is a dewatering nip in which water is pressed out of the fibrous web. It should be noted that the press roll9does not have to be a shoe roll. The press roll9may also be, for example, a suction roll or a roll with a soft elastomer cover. In case of the press roll9being a shoe roll, the preceding roll37may be a suction dewatering roll. The nip between the press roll9and the Yankee drying cylinder3may also be a lightly loaded transfer nip in which no substantial dewatering takes place. In the nip between the press roll9and the Yankee drying cylinder3, the fibrous web is transferred to the outer surface of the Yankee drying cylinder3. The outer surface of the Yankee drying cylinder3is much smoother than the web-contacting surface of the first forming fabric6and the fibrous web will thus follow the outer surface of the Yankee drying cylinder3and the fibrous web is transferred from the first forming fabric6to the Yankee drying cylinder3in the nip formed between the Yankee drying cylinder3and the press roll9. The Yankee drying cylinder rotates in the direction indicated by arrow R. On the Yankee drying cylinder3, the fibrous web is dewatered by drying as the Yankee drying cylinder3is heated from inside by hot steam. The Yankee drying cylinder3may be, for example, a Yankee drying cylinder made of cast iron but it may also be a welded steel Yankee drying cylinder, for example as disclosed by EP 2126203 B1 or EP 2920360 B1. Optionally, a Yankee drying hood11may be arranged to cooperate with the Yankee drying cylinder3by blowing hot air against the fibrous web on the Yankee drying cylinder. If a Yankee drying hood11is used, the Yankee drying hood may be designed for example as disclosed by EP 2963176 B1 but other designs of the Yankee drying hood may also be considered. A creping doctor13is arranged to crepe the dried fibrous web W from the Yankee drying cylinder after which the dried and creped fibrous web W may e sent to a reel-up 12 as schematically indicated inFIG.1. The reel-up 12 may take many different forms, for example as disclosed in U.S. Pat. No. 5,901,918 or as disclosed in U.S. Pat. No. 6,805,317.

As can be seen inFIG.1, the tissue paper making machine1has a frame10which may be arranged to rest on a machine floor23. The frame10can support various parts of the tissue paper making machine1such as for example the Yankee drying cylinder3, the press roll9and the forming section2or parts thereof.

The general concept shown inFIG.1is a common and well tested concept which is often used to manufacture tissue paper. It can be seen as a conventional and reliable technology and produces tissue paper which is deemed to be of sufficient quality for many applications.

A known alternative to the kind of concept that is shown inFIG.1is the through-air drying concept, commonly referred to as TAD. An embodiment of a machine using a TAD concept is shown inFIG.6. With reference toFIG.6, the forming section2may be designed as a C-former/C-wrap former. As in the machine ofFIG.1, the forming section has a head box5and a forming roll4and stock is injected from the head box5into the gap8between the forming fabrics7,27. The first and second forming fabrics27,7are suitably both foraminous wires and the first forming fabric is arranged to carry the newly formed fibrous web to a transfer point TP where the fibrous web is transferred to a structured fabric26such as a TAD wire that runs in a loop, the transfer is suitably assisted by a suction device within the loop of the structured fabric26. A certain speed difference may be used at the transfer point TP such that the structured fabric26runs at a lower speed than the first forming fabric27, for example at a speed that is 2%-8% lower than the speed of the first forming fabric27. The speed difference results in a so-called Rush Transfer or Wet Creping in order to increase the bulk of the fibrous web. InFIG.6, the direction of travel of the structured fabric26is indicated by arrow A. The still wet fibrous web is carried by the structured fabric26along a path over two through-air drying cylinders25, i.e. two TAD cylinders25. The TAD cylinders25are arranged to be rotatable and, during operation, they will rotate in the direction of arrows R just as the Yankee drying cylinder3is rotating in the direction of arrow R. The TAD cylinders25are provided with hoods34and air can be blown either from the inside of the TAD cylinders25and radially outward or from the hoods34radially inward into the TAD cylinders. As hot air is blown through the fibrous web and the structured fabric26as they pass the TAD cylinders, the fibrous web is dried to a considerable extent and the pattern of the structured fabric26is pressed into the fibrous web such that it obtains a three-dimensional structure. The structured fabric26then carries the fibrous web to a Yankee drying cylinder3where final drying is carried out in the same way as explained with reference toFIG.1and the ready-dried fibrous web W can then be creped off with a creping doctor13and sent to a reel-up (not shown). Although not shown inFIG.6, the Yankee drying cylinder3may be provided with a Yankee drying hood as in the machine ofFIG.1.

Machines according to such concepts as the one shown inFIG.6produce tissue paper that is generally much bulkier than tissue paper manufactured on machines built in a way similar to that ofFIG.1. Tissue paper manufactured on a TAD machine will have much higher absorbency that tissue paper manufactured on machines similar to that ofFIG.1and will often also be softer/smoother. However, the operation of such a machine consumes more energy and thus becomes more expensive. Moreover, the TAD units require extra space.

In order to manufacture tissue paper with bulk, absorbency and other desirable qualities that are comparable to tissue paper manufactured on TAD machines, several different concepts have been proposed, usually concepts involving the use of a structured or textured fabric that is used to imprint a three-dimensional pattern into the fibrous web but without using TAD cylinders. Such technologies are sometimes referred to as “hybrid technology”.

One example of a “hybrid” concept is disclosed inFIG.2. With reference toFIG.2, the forming section2is designed as a crescent former, just like the concept ofFIG.1, and it comprises a head box5, a forming roll4, a first forming fabric6which is a felt and a second forming fabric7which is a foraminous wire. Unlike the concept ofFIG.1, the first forming fabric is not arranged to carry the newly formed fibrous web to the Yankee drying cylinder3. Instead, the first forming fabric6which runs in a loop guided by lead rolls20is arranged to carry the newly formed fibrous web to a dewatering press nip PN formed between the press rolls16and19. The press roll16is located within the loop of the first forming fabric6and it may suitably, but not necessarily, be a shoe roll and the preceding roll37may possibly be a suction dewatering roll. The roll19may then serve as a counter roll for the shoe roll16. In the dewatering press nip PN, the fibrous web is dewatered by pressing and transferred to a transfer belt17which has a smooth web-contacting surface formed by polyurethane or a material that comprises polyurethane or a material with properties similar to polyurethane. As the web-contacting surface of the transfer belt17is much smoother than the web-contacting surface of the first forming fabric6which is typically a water-absorbing felt, the fibrous web will be easily transferred to the transfer belt17which runs in a loop supported/guided by lead rolls20. The transfer belt17carries the fibrous web to a nip N formed between the rolls21and22where the web is transferred to a structured fabric18. In the nip N, the structured fabric18imprints a three-dimensional pattern into the fibrous web as the fibrous web and the structured fabric18are pressed together in the nip N. Suitably, a speed difference is used, i.e. a Rush Transfer, such that the structured fabric18moves slightly slower than the transfer belt17. Thereby, additional bulk can be achieved. The structured fabric18is preferably air permeable. The structured fabric18, which moves in the direction of arrow A, will then carry the fibrous web to the Yankee drying cylinder3where it is transferred to the outer surface of the Yankeed drying cylinder3in the nip formed between the press roll9and the Yankee drying cylinder3. The fibrous web is then dried and creped from the Yankee drying cylinder as explained with reference toFIG.1.

The machine concept shown inFIG.2is capable of producing a tissue paper with a high bulk and good absorbency thanks to the three-dimensional pattern imprinted into it by the structured fabric18and without using TAD cylinders that consume a large amount of energy. However, the extra equipment requires more space than the concept shown inFIG.1.

A second hybrid concept tis shown inFIG.4. With reference toFIG.4, the forming section2(with a crescent former) has a head box5, a forming roll4, a first forming fabric6and a second forming fabric7. The reference numeral20is used to indicate lead rolls. As in the concept according toFIG.1, the first forming fabric6is suitably a water-absorbing felt while the second forming fabric7is a foraminous wire. Unlike the concept according toFIG.1, the first forming fabric does not carry the newly formed fibrous web to the Yankee drying cylinder3but to a press nip between a press roll32and a counter roll31. The press roll32is suitably a shoe roll with a flexible belt looping a shoe which may have a concave surface facing the counter roll31. The preceding roll37may advantageously (but not necessarily) be a suction dewatering roll. The counter roll31may be a heated cylinder, i.e. a drying cylinder. To allow heating, one or several induction heating elements may be arranged outside or inside the counter roll31. Alternatively, the counter roll can be heated in other ways, for example by steam that is supplied to the interior of the counter roll31. In the nip between the press roll32and the counter roll, the fibrous web is transferred to the counter roll31which has a smooth outer surface. The fibrous web is then transferred from the outer surface of the counter roll31to an air and water permeable structured fabric33. InFIG.4, the reference numeral30indicates a creping roll that forms a wet-creping nip with the counter roll31. The structured fabric33moves with a speed that is lower than the peripheral speed of the outer surface of the counter roll31such that a Rush Transfer is achieved in order to increase the bulk of the fibrous web. The structured fabric33has a three-dimensional pattern facing the fibrous web and the three-dimensional pattern is pressed into the fibrous web such that a three-dimensional pattern is imparted to the fibrous web. The fibrous web is then transferred to the smooth surface of the Yankee drying cylinder3in a transfer nip formed between the Yankee drying cylinder3and a transfer press roll9. After drying on the Yankee drying cylinder3, the fibrous web can be creped off from the Yankee drying cylinder by a creping doctor13. The Yankee drying cylinder may optionally be provided with a Yankee drying hood. InFIG.4, the arrows R and A indicate direction of rotation/movement.

The machine concept shown inFIG.4is capable of producing a tissue paper with a high bulk and good absorbency thanks to the three-dimensional pattern imprinted into it by the structured fabric33and without using TAD cylinders that consume a large amount of energy. However, the extra equipment still requires more space than the concept shown inFIG.1since the extra fabric33and the press formed by the rolls31,32must be fitted in the area between the forming roll4and the Yankee drying cylinder3.

With reference toFIG.5, a third hybrid concept will now be explained. Like the TAD concept shown inFIG.6, this machine has a C-former forming section2and the forming section comprises a head box5, a forming roll4, a first forming fabric6and a second forming fabric7. The first forming fabric6is a water-absorbing felt while the second forming fabric is a foraminous wire. The forming fabrics6,7are supported/guided by lead rolls20. InFIG.5, the direction of rotation/movement is indicated by arrows R and A. The newly formed fibrous web is carried by the first forming fabric6to a dewatering nip formed between the press rolls35and a counter roll36where the fibrous web is dewatered by pressing. The press roll35is located within the loop of the first forming fabric6and it may suitably, but not necessarily, be a shoe roll. It may be preceded by a roll37which may possibly (but not necessarily) be a suction dewatering roll. A belt28which has a web-contacting surface formed by a material such as polyurethane picks up the web in the dewatering press nip formed between the rolls35, and36and carries the fibrous web to the Yankee drying cylinder3where the web is dried by heat coming from hot steam supplied to the interior of the Yankee drying cylinder and the fibrous web can then be creped off from the Yankee drying cylinder3by a creping doctor13. The web-contacting surface of the belt28is preferably textured such that a three-dimensional patent can be imprinted into the fibrous web to give the fibrous web increased bulk and absorbency. However, the web-contacting surface of the belt28may also be smooth. Optionally, a Yankee drying hood can be arranged over the Yankee drying cylinder3to increase the drying effect by hot air that is blown against the fibrous web. After creping, the fibrous web can be sent to a reel-up (not shown).

The machine concept shown inFIG.5is capable of producing a tissue paper with a high bulk and good absorbency. However, the extra equipment still requires more space than the concept shown inFIG.1since the extra components must be fitted in the area between the forming roll4and the Yankee drying cylinder3.

In the machine concepts described above with reference toFIG.2andFIGS.4-6, there must be enough space between the forming section2and the Yankee drying cylinder3that the various extra rolls and fabrics can be fitted into the machine. In practice, this means that the distance between the forming roll4and the Yankee drying cylinder must have a certain minimum value. For a prior art concept such as the one shown inFIG.1, the distance along the horizontal axis from the axis of rotation A1of the Yankee drying cylinder to the axis of rotation A2of the forming roll4, i.e. the distance corresponding to that indicated as X inFIG.3, may be on the order of no more than 8 m-12 m which, in practice, is insufficient to fit the extra equipment needed for the concepts ofFIG.2andFIGS.4-6. For a machine concept such as the one shown inFIG.2, the horizontal distance between the axis of rotation of the Yankee drying cylinder and the axis of rotation of the forming roll may typically be in the range of 22 m-25 m, for example 24 m or 24.2 m. For a concept such as the one shown inFIG.6, that distance may be in the range of 23 m-37 m, for example 24 m or 36 m while the corresponding distance for the concept ofFIG.4may be in the range of 22 m-28 m in many realistic embodiments. For the concept ofFIG.5, the distance may be in the range of 18 m-21 m, for example 20 m.

The inventors have realized that by providing a machine according to the standard concept of whichFIG.1shows an example and extending the distance between the Yankee drying cylinder and the forming roll, it becomes possible to rebuild the machine much easier at a later stage if this should be required. Such a machine will thus be capable of operating according to the standard concept but can easily be modified into a different concept.

With reference toFIG.3, a tissue paper making machine1comprises a forming section2and a Yankee drying cylinder3mounted to be rotatable about a first axis of rotation A1. The forming section2has a forming roll4mounted to be rotatable about a second axis of rotation A2which second axis of rotation is parallel to the first axis of rotation A1. The forming section2further comprises a head box5, a first forming fabric6and a second forming fabric7. The second forming fabric7is normally a foraminous wire that allows water to pass through it but does not absorb water. The head box5is arranged to inject stock in a gap8between the first forming fabric6and the second forming fabric7. The first forming fabric6is a water-absorbing felt that forms a loop and it is arranged to be capable of carrying a newly formed fibrous web W from the forming section2to the Yankee drying cylinder3. With regard to the terminology, it may be noted that the term “forming fabric” is sometimes understood as referring only to foraminous wires. In the context of this patent application and any patent that may be granted on the basis thereof, both fabrics6,7are referred to as “forming fabrics” since they are both used in the forming section of the paper making machine. The tissue paper making machine1further comprises a press roll9arranged inside the loop of the first forming fabric6which forms a nip N against the Yankee drying cylinder3. The nip N can be a dewatering press nip or just a lightly loaded transfer nip. The press roll9may be, for example, a shoe roll with a rotatable flexible belt that forms a loop around a shoe. The press roll9may advantageously (but not necessarily) be preceded by a suction dewatering roll37. According to the invention, the distance X in the horizontal direction between the first axis of rotation A1and the second axis of rotation A2is preferably in the range of equal to or greater than 18.0 m and less than or equal to 40.0 m, more preferably in the range of equal to or greater than 22.0 m and less than or equal to 37.0 m, even more preferably in the range of equal to or greater than 23.0 m and less than or equal to 30.0 m and most preferably in the range of equal to or greater than 24.0 m and less than or equal to 30.0 m.

To accommodate for rebuild into a concept such as the one shown inFIG.2, the preferred distance X can suitably be in the range of equal to or greater than 22.0 m and less than or equal to 25.0 m. To accommodate for rebuild into the concept shown inFIG.6, the preferred distance X may be in the range of equal to or greater than 23.0 m and less than or equal to 37.0 m, for example 25.0 m or 30.0 m.

To have a machine prepared for rebuild to a concept such as the one according toFIG.4, the distance X may suitably be in the range of equal to or greater than 22.0 m and less than or equal to 28.0 m for example 24.0 m, while a machine prepared for rebuild into a concept such as the one shown inFIG.5may be designed such that the distance X is in the range of equal to or greater than 18.0 m and less than or equal to 21.0 m.

To have the machine1prepared for rebuild into a concept such as the one shown inFIG.2, the distance in the vertical direction between the first axis of rotation A1and the second axis of rotation A2should preferably be less than or equal to half the diameter of the Yankee drying cylinder3.

A brief reference toFIG.7will now be made. InFIG.7, the reference sign Y refers to the vertical distance between the first axis of rotation A1(the axis of rotation of the Yankee drying cylinder3) and the second axis of rotation A2(the axis of rotation of the forming roll4). In other figures, the distance Y is not marked as such, but it will be understood that there is usually a certain vertical distance Y also in all machines/embodiments shown inFIGS.1-6although embodiments of the invention are conceivable in which there is no vertical distance, i.e. in which Y=0.0 m.

In all embodiments, the tissue paper making machine can suitably be supported by a machine frame10resting on a machine floor23. Reference will now be made toFIG.3. In order to make the inventive machine ready to be rebuilt into a concept such as the one according toFIG.2, the distance Y in the vertical direction between the first axis of rotation A1and the second axis of rotation A2can be kept small by shaping the machine floor23such that the machine floor below the forming roll4is at a higher vertical level than the machine floor below the Yankee drying cylinder3. With reference toFIG.3, the machine floor has a raised/elevated part24in the area below the forming roll4. In this way, there is room for a downward run of the first forming fabric6in the concept ofFIG.2which is desirable in order to make ensure a correct amount of wrap around the roll16inFIG.2.

It should be understood that in embodiments of the invention the vertical distance Y may conceivably be greater than half the diameter of the Yankee drying cylinder3.

In one possible embodiment in which the inventive machine is prepared to be rebuilt into a machine as shown inFIG.6, the diameter of the Yankee drying cylinder3may be 5.5 m, the horizontal distance X between the first axis of rotation A1and the second axis of rotation A2may be about 26.2 m and the vertical distance Y between the first axis of rotation A1and the second axis of rotation A2may be 1.6 m.

In another possible embodiment of the inventive machine in which the machine is prepared for rebuild into a machine as shown inFIG.2, the diameter of the Yankee drying cylinder3may be 5.5 m, the horizontal distance X between the first axis of rotation A1and the second axis of rotation A2may be 23.4 m and the vertical distance Y between the first axis of rotation A1and the second axis of rotation A2may be 1.3 m.

The invention may also be understood in terms of a method of rebuilding a tissue paper making machine from a machine as defined by any of claims1-8into a machine as shown in any ofFIGS.2or4-6. Such a method would comprise the steps of replacing the felt and roll arrangement between the forming roll4and the Yankee drying cylinder3as shown inFIG.3with the arrangement of rolls and fabrics shown in any ofFIGS.2or4-6.

The Yankee drying cylinder3may be of many different dimensions but, in typical embodiments, the diameter of the Yankee drying cylinder would normally be in the range of 3.5 m-7.0 m, for example in the range of 3.5 to 6.7 m or from 3.5 to 6.5 m, and the width of the Yankee drying cylinder may be in the range of 2.5 m-8.0 m, for example 4.0 m, 4.7 m, 5.0 m or 6.0 m.

Thanks to the invention, a tissue paper making machine can be built for a standard concept and yet be easily rebuilt to a concept for making bulkier tissue paper with high absorbency. The long distance between the axes of rotation A1, A2makes it possible to fit in the extra equipment needed for the concepts shown inFIG.2,FIG.4,FIG.5orFIG.6or other for making bulkier tissue paper with high absorbency without having to move these axis of rotation.