Arrangement and method for operating a belt in a machine

Abstract

The invention relates to a method for operating a belt (2) in a machine for producing a fibrous web (3), wherein a fibrous web (3) is transferred to the belt (2) in a first region (6) and is removed from the belt (2) in a transfer region (8). The invention is characterized in that, during operation, a grinding device (9) for setting a desired surface roughness of the belt (2) is guided against the belt (2) between the transfer region (8) and the first region (6). The invention also relates to an arrangement for carrying out the method and allows advantageous and effective operation of the belt (2).

Description

[0001] ARRANGEMENT AND METHOD FOR OPERATION OF A BELT IN A MACHINE

[0002] The invention relates to a method for dewatering a fibrous web, in particular a paper, tissue or cardboard web, in a machine for producing the fibrous web; wherein the fibrous web is dewatered by pressing in a first nip formed between a shoe roller and a counter roller into a first covering, in particular a felt; wherein the shoe roller comprises a belt designed as a shoe press belt and the first nip forms a first region; wherein the fibrous web on the first covering is pressed into the first nip, i.e.The first area is guided and transferred from the first tensioning to the shoe press belt of the shoe roller; the fiber web is guided between the first area and a transfer area on an outer side of the belt, the fiber web being in direct contact with the outer side of the shoe roller belt between the first area and the transfer area; the fiber web is removed from the shoe roller belt in the transfer area, and after removal of the fiber web between the transfer area and the first area, substantially no fiber web remains on the shoe roller belt. The invention also relates to an arrangement for carrying out the method.

[0003] EP 2581493 B1 describes a belt for conveying a fibrous web, which is waterproof and has a certain roughness on the side in contact with the fibrous web. Figure 3 further shows an arrangement of the belt in a machine for producing a fibrous web.

[0004] EP 2264243 A1 describes a method for treating a fiber web in a paper or board machine, wherein a press roll of a long-nip press unit, i.e., a shoe roll, has a rotating press sleeve, and the fiber web is dewatered in an extended press gap between a counter roll and the press sleeve. In particular, after the extended press gap, the fiber web is guided directly onto the rotating press sleeve of the press roll to a transfer area for the fiber web transfer. This method allows for dewatering and onward transport of the fiber web without an intermediate web transfer, as well as a simpler and more compact design. Advantageously, re-wetting of the fiber web can be reduced, and improved quality properties of the fiber web can be achieved.

[0005] EP1997584B1 relates to an arrangement for grinding the outer surface of a shoe press roll of a machine for the production and / or finishing of a paper, cardboard or other fibrous web, wherein the shoe press roll has a flexible roll shell which is pressed against a counter roll by a pressure element with a concave pressure surface. The arrangement allows the roll shell to be ground in the machine.

[0006] The object of the invention is a method or arrangement for operating a belt in a machine for producing a fibrous web, whereby a constant efficiency in operation and a constant quality of the fibrous web are achieved.

[0007] According to the invention, this is achieved by guiding a grinding device against the outside of the belt between the transfer area and the first area while the fiber web is guided between the first area and the transfer area on the belt of the shoe roller. This device is used to adjust the desired surface roughness of the belt between the transfer area and the first area. The method according to the invention is thus used during operation, i.e., while the fiber web is being transferred with the belt, typically at a speed of more than 600 m / min, and advantageously more than 800 m / min. The belt is typically designed as an endless loop and is impermeable to water. Typically, the belt comprises at least one layer of resin, in particular polyurethane, and a reinforcing yarn structure arranged inside the belt.The inventors have recognized that the condition of the belt on the outer surface contacted by the fiber web, in particular the surface roughness of the belt, is crucial for efficient operation. Efficient operation is characterized by the ability to effectively transfer the fiber web—for example, in a press nip—to the belt, to effectively guide the fiber web on the belt, and, in particular, to effectively remove it from the belt in the transfer area. The inventors have further recognized that, in particular, the effective removal of the fiber web from the belt allows for the achievement of a consistently high quality of the removed fiber web, thus preventing, for example, tears or rips in the fiber web, or the formation of holes in the fiber web.Unexpectedly, the inventors discovered that a grinding device for adjusting the desired surface roughness of the belt can even be guided against the outer surface of the belt during operation, between the transfer area and the first area. This allows for the adjustment or restoration of an optimally conditioned belt during operation and, in particular, does not require stopping the belt-enclosing assembly or interrupting the production of the fiber web. The solution according to the invention also does not require the grinding device to be continuously guided against the belt during operation. Rather, it is possible to guide the grinding device against the belt as needed during operation. The solution according to the invention thus allows for greater efficiency of the belt-enclosing assembly, thereby avoiding interruptions caused by standstills or operation without a fiber web.so that production can be carried out at a consistently high level of quality.

[0008] In an advantageous embodiment of the method, at least one cleaning device, in particular a cleaning scraper, is guided against the outer surface of the belt between the transfer area and the first area where essentially no fiber web is guided on the belt. The cleaning device is positioned downstream of the transfer area and upstream of the grinding device. This ensures that any contaminants, fiber residues, etc., deposited on the belt are removed by the cleaning device, thus preventing contamination or a negative impact on the grinding device's performance. In a particularly advantageous embodiment, at least two cleaning devices are arranged upstream of the grinding device and guided against the belt.

[0009] In an equally advantageous embodiment of the method, the grinding device comprises an abrasive, wherein the abrasive is pressed against the belt with a line load of less than 1000 N / m and preferably with a line load of less than 400 N / m. This allows for precise adjustment of the desired surface roughness of the belt. In another advantageous embodiment of the method, the grinding device is guided or pressed against the outside of the belt at a substantially right angle, with a support element arranged opposite the grinding device on an inside side of the belt opposite the outside. It has been found that the desired surface roughness of the belt can be advantageously adjusted by positioning the belt between a support element located on the inside of the belt and the grinding device.

[0010] In a further advantageous embodiment of the method, the grinding device is moved away from the belt for cleaning, while the fiber web is guided on the belt between the first area and the transfer area. After cleaning, the grinding device is moved back against the belt. Cleaning the grinding device can also include replacing or renewing it. Furthermore, it was found that to achieve the desired effect according to the invention, it is not necessary to keep the grinding device permanently against the belt during operation. Rather, the belt can be reactivated by setting the desired surface roughness via the grinding device during operation and then moving the grinding device away from the belt. Reactivation of the belt then occurs as needed, e.g.,in the event of a deterioration in operational efficiency, for example due to problems in the removal of the fiber web from the belt.

[0011] In an equally advantageous embodiment of the process, the surface roughness is adjusted to a value of Ra = 0.5 to 8, measured in an unloaded and dry condition. Adjusting the surface roughness to a value of Ra = 2 to 5, preferably Ra = 2.5 to 4 pm, and most preferably Ra = 2.8 to 3.8 pm, is particularly advantageous. The roughness is determined, for example, according to ISO 4287. It is particularly evident that at these advantageous roughness values, the removal of the fiber web from the belt can be carried out very efficiently.

[0012] In the embodiment of the method according to the invention, the belt is operated as a shoe press belt of a shoe roller. The fiber web guided on a first covering is transferred in the first nip, formed between a counter roller and the shoe roller, from the first covering, in particular a felt, guided through the first nip, onto the shoe press belt of the shoe roller. A press shoe is arranged on the inside of the shoe press belt to form the first nip, and the press shoe is pressed against the counter roller. The shoe press belt is impermeable to water and typically comprises at least one layer of polyurethane. The transfer of the fiber web from the first covering to the shoe roller takes place in the first nip, which is designed as a long nip, i.e.,To form the first nip, a press shoe is arranged on the inside of the shoe press belt, with the press shoe pressed against the counter roller. The fiber web is removed from the shoe press belt in the transfer area. The transfer can, for example, take place onto a second fabric, with the transfer occurring, for instance, in a second nip formed between a take-off device and the shoe roller. However, the transfer or removal of the web could also occur without a nip – in the sense of a free pull of the fiber web. The inventors have recognized, in particular, that the efficient removal of the fiber web from the shoe press belt allows for the achievement of a consistently high quality of the removed fiber web, and, for example, prevents tears or holes in the fiber web.

[0013] In an advantageous embodiment of the process, a pressure of greater than 5 kN / m is applied in the first nip between the counter roller and the shoe roller. This transfers the fiber web, guided through the first nip on the first tensioning layer, from the first tensioning layer to the shoe press belt. The pressure on the fiber web, positioned between the shoe press belt and the first tensioning layer, also results in dewatering of the fiber web into the first tensioning layer. Increased dewatering can be achieved by applying a higher line load in the first nip. For example, a line load greater than 70 kN / m is advantageous, and a line load greater than 100 kN / m is particularly advantageous.Equally advantageous, for example, is operation with a line load in the range between 70 kN / m and 600 kN / m, whereby, in addition to reliable transfer of the fiber web in the first nip, advantageous dewatering of the fiber web can also be achieved. In a further advantageous embodiment of the process, a second nip is formed in the transfer area, i.e., the second nip is formed between the shoe roller and a take-off device, wherein a pressure with a line load, in particular greater than 1 N / m, takes place in the second nip. It has been recognized that the formation of a second nip for taking the fiber web from the shoe roller is advantageous with regard to the stability and efficiency of the take-off, particularly advantageous compared to taking the fiber web via a free pull.The take-off device can be designed, for example, as a roller, and in particular – to assist the take-off – as a suction roller, or, for example, as a take-off suction device, suction box, transfer suction device, or similar. It is advantageous to transfer the fiber web in the second nip from the shoe press belt to a second covering guided through the second nip, the second covering being designed, in particular, as a structured covering. The transfer of the fiber web to the second covering, which is designed, in particular, as structured, has a beneficial effect on the quality, e.g., the thickness, volume, or absorption capacity, of the fiber web.

[0014] The invention also relates to an arrangement for carrying out the method according to the invention, comprising a belt, wherein the arrangement for guiding the fiber web on the belt is formed between the first region and the transfer region. According to the invention, the arrangement includes a grinding device, wherein the grinding device for setting a desired surface roughness of the belt between the transfer region and the first region can be guided against the outside of the belt, while between the first region and the transfer region the fiber web is guided directly on the outside of the belt. The arrangement according to the invention allows the desired surface roughness of the belt to be set during operation, thereby enabling significantly more efficient operation. Downtime for belt replacement can be avoided, since the belt can be optimally adjusted during operation.

[0015] In a particularly advantageous embodiment of the arrangement, the grinding device is encompassed by a scraper assembly and detachably mounted on a scraper holder of the scraper assembly. In particular, the grinding device can be connected directly to a blade of the scraper holder or indirectly to a support element of the scraper holder. Scraper assemblies are known and available in high quality. By incorporating the grinding device into a scraper assembly, a grinding device can be very easily implemented in an existing arrangement or retrofitted. To adjust the desired surface roughness of the belt, the grinding device can advantageously be pressed against the belt by means of an actuator. This allows for easy adjustment of the line load with which the abrasive is pressed against the belt. It is particularly advantageous to allow the grinding device to oscillate in an axial direction, i.e.,The belt should be positioned perpendicular to one direction of rotation. This oscillation prevents local inconsistencies in the belt's surface roughness. For the grinding device, an abrasive material designed as a belt or film is particularly advantageous. These are readily available in a wide range of qualities and can be easily replaced or renewed during cleaning of the grinding device.

[0016] In the embodiment according to the invention, the arrangement is configured as a shoe press assembly. The belt is designed as the shoe press belt of a shoe roller, the first section is configured as the first nip between a counter roller and the shoe roller, and the shoe press assembly is designed to guide the fiber web on the shoe press belt between the first nip and the transfer section. Adjusting the desired surface roughness of the shoe press belt allows for efficient operation of the shoe press assembly.

[0017] The invention will now be described using the drawing as an example of an application in a shoe press arrangement.

[0018] Fig. 1 shows a shoe press arrangement according to the invention.

[0019] Fig. 1 shows a shoe press arrangement according to the invention for carrying out the method, comprising a shoe roller 1 with a shoe press belt 2. A first nip 6 is formed between a counter roller 7 and the shoe roller 1, wherein a press shoe 14 is arranged on the inside of the shoe press belt 2 and the press shoe 14 is pressed against the counter roller 7. The fiber web 3, guided on a first covering 4, is transferred from the first covering 4, in particular a felt, to the shoe press belt 2 in the first nip 6. Subsequently, the fiber web 3 is guided on the shoe press belt 2 to the transfer area 8, wherein the fiber web 3 is in direct contact with the shoe press belt 2 between the first nip 6 and the transfer area 8. In the transfer area 8, the fiber web 3 is removed from the shoe press belt 2, with a second nip 10 being formed between the shoe roller 1 and a removal device 11. In Fig.In Figure 1, the take-off device 11 is designed, for example, as a transfer suction device, wherein the fiber web 3 is transferred from the shoe press belt 2 to a covering 5 guided by the second nip 10 in the transfer area 8. The grinding device 9 according to the invention is also shown, which is designed to adjust a desired surface roughness of the shoe press belt and which can be guided against the shoe press belt 2 between the transfer area 8 and the first nip 6, while the fiber web 3 can be guided directly on the shoe press belt 2 between the first nip 6 and the transfer area 8. Furthermore, a cleaning device 12 for cleaning the surface of the shoe press belt 2, a cleaning scraper, is shown between the transfer area 8 and the first nip 6, wherein the cleaning device 12 is arranged after the transfer area 8 and before the grinding device 9.

[0020] The present invention offers numerous advantages. The inventors have recognized that the operation of the belt in the arrangement according to the invention can be made significantly more efficient if a desired surface roughness of the belt can be set during operation. This allows for consistently good removal of the fiber web from the belt, thereby preventing fiber web breaks or partial removal. Corresponding to the improved fiber web removal, the fiber web also exhibits improved quality properties. Downtime can be avoided due to the extended service life of the belt in the arrangement, which is also economically advantageous.

[0021] Reference sign

[0022] 1 shoe roller

[0023] 2 shoe press belts

[0024] 3 Fiber web 4 First covering

[0025] 5 Second covering

[0026] 6 First nip / first area

[0027] 7 Counter roller 8 Transfer area

[0028] 9 Grinding device

[0029] 10 Second Nip

[0030] 11 Acceptance device

[0031] 12 Cleaning device 13 Abrasive

[0032] 14 Press shoe

[0033] 15 scraper arrangement

Claims

Patent claims 1. Method for dewatering a fibrous web (3), in particular a paper, tissue or board web, in a machine for producing the fibrous web (3); wherein the fibrous web (3) is dewatered by pressing it into a first nip (6) formed between a shoe roll (1) and a counter roll (7) into a first covering (4), in particular a felt; wherein the shoe roll (1) comprises a belt (2) designed as a shoe press belt (2) and the first nip (6) forms a first area (6); wherein the fibrous web (3) is guided on the first covering (4) into the first nip (6), i.e. the first area (6), and is transferred from the first covering (4) onto the shoe press belt (2) of the shoe roll (1);wherein the fiber web (3) is guided between the first area (6) and a transfer area (8) on an outside of the belt (2), wherein the fiber web (3) is guided between the first area (6) and the transfer area (8) in direct contact with the outside of the belt (2) of the shoe roller (1); the fiber web (3) is removed from the belt (2) of the shoe roller (1) in the transfer area (8), wherein after removal of the fiber web (3) between the transfer area (8) and the first area (6) essentially no fiber web (3) is guided on the belt (2) of the shoe roller (1), characterized in that, while the fiber web (3) is guided on the belt (2) of the shoe roller (1) between the first area (6) and the transfer area (8), a grinding device (9) for adjusting a desired surface roughness of the belt (2) between the transfer area (8) and the first area (6) is guided against the outside of the belt (2).

2. The method according to claim 1, wherein at least one cleaning device (12) for cleaning the outside of the belt (2), in particular a cleaning scraper, is guided against the outside of the belt (2) between the transfer area (8) and the first area (6), wherein the cleaning device (12) is guided against the belt (2) after the transfer area (8) and before the grinding device (9).

3. Method according to one of claims 1 to 2, wherein the grinding device (9) comprises an abrasive (13) and the abrasive (13) is pressed against the belt (2) with a line load of less than 1000 N / m and preferably with a line load of less than 400 N / m.

4. Method according to one of claims 1 to 3, wherein the grinding device (9) is guided or pressed substantially at a right angle against the outside of the belt (2), wherein a support element is arranged opposite the grinding device (9) on an inside of the belt (2) opposite the outside for supporting the belt (2).

5. Method according to any one of claims 1 to 4, wherein, while the fibrous web (3) is guided on the belt (2) between the first area (6) and the transfer area (8), the grinding device (9) is moved away from the belt (2) for cleaning, wherein after cleaning the grinding device (9) the grinding device (9) is moved back towards the belt (2).

6. Method according to any one of claims 1 to 5, wherein the surface roughness is measured to a value in an unloaded and dry condition. Ra is set to 0.5 to 8.

7. Method according to claim 6, wherein the surface roughness is adjusted to a value of Ra = 2 to 5, preferably Ra = 2.5 to 4 pm and particularly preferably Ra = 2.8 to 3.8 pm.

8. Method according to one of claims 1 to 7, wherein in the first nip (6) between the counter roller (7) and the shoe roller (1) a pressure is applied with a line load greater than 5 kN / m.

9. Method according to one of claims 1 to 8, wherein in the transfer area (8) a second nip (10) is formed between the shoe roller (1 ) and a removal device (11 ) and in the second nip (10) a pressure is applied with a line load in particular greater than 1 N / m.

10. Method according to claim 9, wherein the fiber web (3) is transferred in the second nip (10) from the shoe press belt (2) to a second covering (5) guided through the second nip (10), wherein the second covering (5) is in particular designed as a structured covering.

11. Method according to any one of claims 1 to 10, wherein to form the first nip (6) a press shoe (14) is arranged on the inside of the shoe press belt (2) and the press shoe (14) is pressed against the counter roller (7).

12. Arrangement for carrying out the method according to any one of claims 1 to 11, wherein the arrangement is a shoe press arrangement comprising a belt (2), wherein the belt (2) is arranged as a shoe press belt (2) of a shoe roller (1), the first region (6) is designed as a first nip (6) between a counter roller (7) and the shoe roller (1), wherein the arrangement for guiding the fiber web (3) on the belt (2) is designed between the first region (6) and the transfer region (8), characterized in that the arrangement comprises a grinding device (9), the grinding device for adjusting a desired surface roughness of the outside of the belt (2) between the transfer region (8) and the first region (6) can be guided against the belt (2), while between the first region (6) and the transfer region (8) the fiber web (3) is guided directly on the outside of the belt (2).

13. Arrangement according to claim 12, wherein the grinding device (9) is comprised of a scraper arrangement (15), the grinding device (9) is detachably arranged on a scraper holder of the scraper arrangement (15), wherein the grinding device (9) is in particular directly connectable to a blade of the scraper holder or indirectly to a support element of the scraper holder.

14. Arrangement according to claim 12 or 13, wherein the grinding device (9) can be pressed against the belt (2) by means of an actuator to adjust the desired surface roughness of the belt (2), and in particular the grinding device (9) can be oscillated in an axial direction.

15. Arrangement according to one of claims 12 to 14, wherein the grinding device (9) comprises an abrasive (13) designed as a grinding belt or grinding film.

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