CN110939007B

CN110939007B - Machine and method for producing a fibrous web

Info

Publication number: CN110939007B
Application number: CN201910782360.4A
Authority: CN
Inventors: A.L.A.费尔南德斯
Original assignee: Voith Patent GmbH
Current assignee: Voith Patent GmbH
Priority date: 2018-09-24
Filing date: 2019-08-23
Publication date: 2021-12-03
Anticipated expiration: 2039-08-23
Also published as: DE102018123389A1; CN110939007A

Abstract

The invention relates to a machine (1) for producing a fibrous web (2), comprising at least one press device (6) having a press element (7) and a counter-element (8) having a closing surface for forming a press nip (9) and having a water-absorbing belt (3) having a web side (4) and an opposite press element side (5), which can be guided together with the fibrous web (2) through the press nip (9) such that the fibrous web (2) is separated from the web side (4) of the water-absorbing belt (3) at the end of the press nip and is moved further with the counter-element (8), wherein the water-absorbing belt (3) is guided over a partial section by the press element (7) from the end of the press nip (9) and is provided on the press element side (5) of the water-absorbing belt (3) in the region of the water-absorbing belt (3) free of the fibrous web for detaching the water-absorbing belt (3) A suction device (12) for water.

Description

Machine and method for producing a fibrous web

Technical Field

The invention relates to a machine for producing a fibrous web, in particular a tissue web, having at least one press device comprising a press element and a counter element, which have a closing surface for forming a press nip and a water-absorbing belt having a web side and an opposite press element side, which can be guided together with the fibrous web through the press nip such that the fibrous web is separated from the web side of the water-absorbing belt at the end of the press nip and is moved further together with the counter element.

The invention further relates to a method for producing a fibrous web.

Background

Machines of this type are known. Document EP 0926296B 1 shows a machine for making tissue webs. In the forming zone, the felt belt together with the forming wire is guided partially around the forming roller, forming an insertion gap. A fibre suspension is fed into the lead-in gap through a headbox, from which the tissue web is formed. After the forming roll the forming wire is transferred away and the tissue web on the felt belt is guided to a press nip, which is formed by a shoe roll and a yankee dryer cylinder. After the press nip, the tissue web is run on for further drying using a yankee drying cylinder. In the endless belt formed by the felt belt, a suction device for loading the felt belt and the jointly guided tissue web is provided before the press nip.

It is also known to provide a suction element for the moisture treatment of the felt belt outside the endless belt formed by the felt belt between the press nip and the forming zone. Such suction elements are also known as "suction boxes or felt vacuum boxes". The water contained in the felt belt is removed by said moisture treatment, followed by the addition of the fibre suspension.

Disclosure of Invention

The object of the invention is to provide a machine and a method for producing a fibrous web, in particular a tissue web, in order to reduce the energy expenditure required for adjusting the running belt.

The object is achieved by a machine for producing a fibrous web, in particular a tissue web, having at least one press device comprising a press element and a counter-element, which press element and counter-element have a closing surface for forming a press nip and have a water-absorbing belt with a web side and an opposite press element side, which water-absorbing belt can be guided together with the fibrous web through the press nip such that the fibrous web is separated from the web side of the water-absorbing belt at the end of the press nip and continues to run together with the counter-element. According to the invention, the water-absorbing belt is guided over a partial section by the press element from the end of the press nip, and a suction device for dewatering the water-absorbing belt is provided in the region of the fiber-free web of the water-absorbing belt on the press element side of the water-absorbing belt.

By the guidance of the water-absorbing belt in a partial section on the press element, the water-absorbing belt immediately separates from the fibrous web at the end of the press nip and thus overcomes the moisture regain. The arrangement of the suction device inside the endless belt formed by the water-absorbing belt for the purpose of moisture treatment of the water-absorbing belt has the advantage that the water contained in the water-absorbing belt can be removed with less energy. This is supported by the negative pressure that is formed in the wedge angle between the suction belt and the press element. Water thrown back from the surface of the press element onto the suction belt by centrifugal force can thus be removed directly from the surface of the suction belt by the suction device.

In a practical embodiment, the mating element is formed by a drying cylinder, in particular a yankee drying cylinder.

In another possible embodiment, the press element is formed by a press roll, which has in particular an open, preferably grooved and/or drilled surface.

The invention works particularly advantageously if the press roll has an open surface, because water collected in the open surface and thrown off the end of the press nip is removed directly from the inner side of the suction belt by the suction device.

The press element may also be constituted by a shoe press unit. The invention functions particularly advantageously in the case of the use of a shoe press, since a greater amount of water has to be conducted.

The opening surface may comprise a bore hole embodied as a blind hole.

In one practical case, the shoe press unit may comprise a water-absorbent mantle and a press shoe arranged inside the mantle and being pressable against a mating element.

Furthermore, the side of the outer cover facing the press element side of the water-absorbing belt can have an open, preferably grooved and/or drilled surface. In the case of open surfaces, the invention can also function particularly advantageously here, since the water collected in the open surfaces and thrown out at the end of the press nip towards the suction belt is removed directly from the inside of the suction belt by the suction device.

The partial section is preferably selected such that the direction of the diverted water-absorbing belt forms an angle in the range of more than 10 °, in particular more than 15 °, preferably in the range of 20 °, with a tangent line at the end of the press nip on the counter element. The moisture regain of the fibrous web is thereby overcome by the water-absorbing belt.

Furthermore, the suction device can also have a coating with openings, which are preferably embodied as bores and/or slits.

Preferably, the machine may be embodied as a crescent-shaped former. The fibrous web is guided on a water-absorbing belt from a forming zone to a press nip.

In an advantageous development, the water-absorbing belt comprises at least one first and one second layer and a layer structure, which, viewed in the thickness direction, is arranged on the half facing the press element and has a higher specific flow resistance than the first and/or second layer. The layer structure prevents or reduces the backflow of water contained in the press element-side half of the suction belt in the web-side direction by means of a higher flow resistance. The water can thus be removed more easily by means of a suction device arranged on the side of the press element. The flow resistance of the layer or layer structure can be determined, for example, by passing, for example, water through the layer or layer structure in the thickness direction over the flow surface at a predetermined pressure difference, and measuring the volume flow rate and correlating it to the thickness of the layer or layer structure. If the flow resistances of different layers or layer structures should be compared, the edge conditions should remain constant.

Advantageously, the first layer constitutes the web side and comprises a fibrous backing layer, preferably made of plastic fibres. The first layer may be applied in a felt-like manner. The plastic fibres may be connected, e.g. stitched, to the second layer.

The second layer may be a woven layer and the first layer may preferably be connected, in particular stitched, to the second layer.

The layer structure is advantageously connected to the second layer.

In addition, the layer structure may be joined to a second layer and constitute the press element side of the water-absorbing belt.

However, it is also conceivable for the layer structure to form the press element side. Which in this case constitutes the running side of the suction belt and is in contact with the press element. The layer structure can be optimized with regard to low wear and at the same time with regard to flow resistance by means of a mechanical transmission.

Furthermore, a further layer can be provided on the half of the water-absorbing belt facing the press element, said further side preferably comprising a fibrous backing layer made of plastic fibers. The further layer may be seamed with the layer structure and/or with the second layer.

In a practical embodiment, the layer structure may be arranged between the second layer and the further layer.

It is also possible to arrange the layer structure inside the further layer.

In another possible embodiment, the layer structure can be arranged adjacent to the further layer and form the press element side.

The water-absorbing belt can be implemented as a press felt.

In a possible development, the layer structure can be embodied as a film with openings. This may be, for example, a plastic film with holes sewn or punched or drilled with a laser.

The layer structure can however also be embodied as a fibrous backing layer made of fine fibers. The fiber fineness may preferably be less than or equal to 3dtex (dtex).

The layer structure may preferably at least partially comprise a component consisting of a thermoplastic polyurethane elastomer (TPU).

The object of the invention is also achieved by a method for producing a fibrous web, in particular a tissue web, using at least one press device comprising a press element and a counter-element, which press element and counter-element have a closing surface for forming a press nip and a water-absorbing belt having a web side and an opposite press element side, which water-absorbing belt can be guided together with the fibrous web through the press nip such that the fibrous web is separated from the web side of the water-absorbing belt at the end of the press nip and is moved further together with the counter-element. It is essential according to the invention that the water-absorbing belt is guided over a partial section by the press element from the end of the press nip, and that a suction device for dewatering the water-absorbing belt is provided in the region of the fiber-free web of the water-absorbing belt on the press element side of the water-absorbing belt.

Drawings

Other technical features and advantages of the present invention are given by the following description of the preferred embodiments in conjunction with the accompanying drawings.

In the drawings:

fig. 1 shows a known embodiment of a machine for producing a fibrous web;

figure 2 shows a schematic view of an embodiment of the pressing device of the machine according to the invention;

fig. 3 shows a schematic view of an embodiment of a machine for manufacturing a fibrous web according to the present invention;

fig. 4 shows a schematic view of an embodiment of a water-absorbent belt of a machine for manufacturing a fibrous web according to the present invention;

fig. 5 shows a schematic view of another embodiment of a water-absorbent belt of a machine for manufacturing a fibrous web according to the invention;

Detailed Description

Fig. 1 shows a known embodiment of a machine for manufacturing tissue webs. In the forming zone, the felt belt together with the forming wire 25 is guided partially around the forming roller 24, forming an introduction gap. The fibre suspension is fed into the lead-in gap through a headbox 23, from which the tissue web 2 is formed. After the forming roll 24, the forming wire 25 is transferred away and the tissue web on the felt belt is guided to a press nip, which is formed by a shoe roll and a yankee dryer cylinder. After the press nip, the tissue web 2 continues to run for further drying using a yankee dryer cylinder 8. In the endless belt formed by the felt belt, a suction device for loading the felt belt and the jointly guided tissue web can be arranged before the press nip. Outside the endless belt formed by the felt belt and between the press nip and the forming zone, a suction element 20 is provided for the moisture treatment of the felt belt. Such a suction element 20 is also known as a "suction box or felt vacuum box". The water contained in the felt belt is removed outwards by said moisture treatment, after which the fibre suspension is added.

Fig. 3 shows a schematic view of an embodiment of a machine 1 according to the invention for producing a fibrous web 2. In the forming zone, the suction belt 3 together with the outer wire 25 is guided partially around the forming roll 24, forming an introduction gap. The fiber suspension is fed into the introduction gap via a headbox 23, from which the fiber web 2 is formed. After the forming roll 24, the outer wire 25 is transferred away and the fibrous web 2 is guided on the web side 4 of the water-absorbing belt 3 to a press device 6 with a press nip formed between the press element 7 and the yankee drying cylinder 8. In this embodiment, the press element 7 is constituted by a shoe roll. The cylindrical surface of the yankee dryer cylinder 8 is designed to be smooth. After the press nip 9, the fibrous web 2 continues to run together with the yankee drying cylinder 8 for further drying by means of impingement flow through the housing 21 and for crimping and peeling by means of a creping doctor and for guidance to another machine section. Inside the endless belt formed by the water-absorbing belt 3, a suction-type deflecting roller or suction element 22 (not shown here) can be provided upstream of the press nip 9 for sucking the water-absorbing belt 3 and the jointly guided fibrous web 2. Opposite the suction element 22, a steam or hot air hood is also provided for increasing the dewatering capacity. Between the press nip 9 and the forming zone, a suction device 12 is provided inside the endless belt formed by the water-absorbing belt 3 for moisture treatment of the water-absorbing belt 3. The suction device 12 has a coating with a plurality of openings through which water is sucked into the suction element and which are preferably embodied as bores and/or slits. The suction device 12 is arranged in the area of the water-absorbing belt 3 without the fibrous web 2. Thereby simplifying and improving the humidity treatment. The water of the suction belt 3 is conducted away towards the inside, i.e. towards the press element side 5, by means of the suction device 12. The shoe roll comprises a press shoe 10 which can be pressed against the yankee dryer cylinder 8 in order to create a press pressure in the press nip. A casing 11 surrounding the press shoe 10 runs between the press shoe 10 and the fibrous web 2 through the press gap 9. In order to increase the dewatering of the fibrous web 2 in the press nip 9, the side of the cover 11 which comes into contact with the press element side 5 of the water-absorbing belt 3 has a groove. The water pressed out of the fibrous web 2 in the region of the press nip 9 partially passes through the water-absorbing belt 3 into the grooves of the outer cover 11 and, after the press nip 9, is thrown from there partially in view of centrifugal forces to the press element side 5 of the water-absorbing belt 3. Thereby making the water-absorbent belt 3 moist. The thrown-off water can be removed efficiently and with little energy expenditure by the arrangement according to the invention of the suction device 12 without having to suck the water through the entire thickness of the suction belt 3. Furthermore, the suction device 12 can be provided with a suction element 20 downstream as required, viewed in the direction of travel 26 of the suction belt 3.

Fig. 2 shows a schematic view of an embodiment of the pressing device 6 of the machine 1 according to the invention. The fibrous web 2 is guided on the web side 4 of the water-absorbing belt 3 to a press device 6 with a press nip 9, which is formed between a press element 7 and a yankee drying cylinder 8. In this embodiment, the press element 7 is constituted by a shoe roll. The cylindrical surface of the yankee dryer cylinder 8 is designed to be smooth. The shoe roll comprises a press shoe 1O which can be pressed against the yankee dryer cylinder 8 in order to be able to create a pressing pressure in the press nip 9. A casing 11 surrounding the press shoe 10 runs between the press shoe 10 and the fibrous web 2 through the press gap 9. In order to increase the dewatering of the fibrous web 2 in the press nip 9, the side of the cover 11 which comes into contact with the press element side 5 of the water-absorbing belt 3 has an open surface, in this embodiment a groove. The water pressed out of the fibrous web 2 in the region of the press nip 9 partially passes through the water-absorbing belt 3 into the grooves of the outer cover 11.

The suction belt 3 is guided over a partial section by the press element 7 from the end of the press nip 9. The partial sections are preferably selected such that the direction of the transferred water-absorbing belt 3 forms an angle 14 in the range of more than 10 °, in particular more than 15 °, preferably 20 °, with a tangent 13 at the end of the press nip on the counter element 8. The dampening of the fibrous web 2 is thereby overcome by the water-absorbing belt 3. The moisture treatment of the water-absorbing belt 3 is assisted by the negative pressure created in the wedge angle between the water-absorbing belt 3 and the press element 7.

Fig. 4 shows a schematic view of an embodiment of a water-absorbing belt 3 of a machine 1 for producing a fibrous web 2 according to the invention. The water-absorbent belt 3 comprises a first layer 15, a second layer 16, a further layer 17 and a layer structure 18 having a higher specific flow resistance than the first layer 15 and/or the second layer 16 and/or the further layer 17. The web side 4 is constituted by a first layer 15 and the press element side 5 is constituted by a further layer 17. The layer structure 18 is arranged on the half facing the press element 7, seen in the thickness direction of the water-absorbing belt 3. The higher flow resistance of the layer structure 18 prevents or minimizes the back flow of water contained in the press element-side half of the suction belt 3 in the direction of the web side 4. The water can thus be removed more easily by means of the suction device 12 arranged on the press element side 5. The first layer 15 constituting the web side 4 comprises a fibrous backing layer in the form of a felt and is stitched to the second layer 16. The second layer 16 is a woven layer. In this embodiment, the layer structure 18 is woven into the further layer 17 between the second layer 16 and the press element side 5 and is thus located inside said further layer 17. The layer structure 18 can also directly adjoin the second layer 16 and be connected to it, for example by means of a seam. The other layer 17, which constitutes the press element side, likewise comprises a fibrous batt and is stitched to the second layer 16. The layer structure 18 is embodied as a film having a plurality of openings. This may be, for example, a plastic film with holes sewn or punched or drilled with a laser. Within the scope of the invention, the layer structure 18 can also be embodied as a fibrous backing layer made of fine fibers. The fiber fineness may preferably be less than or equal to 3dtex (dtex). The layer structure 18 at least partially contains a component made of a thermoplastic polyurethane elastomer (TPU). This improves the elasticity of the water-absorbent belt 3.

Fig. 5 shows a schematic view of a further embodiment of a water-absorbing belt 3 of a machine 1 for producing a fibrous web 2 according to the invention. The embodiment of fig. 5 differs from the embodiment of fig. 4 only in the arrangement of the layer structure 18 in the thickness direction of the water-absorbent belt 3. The layer structure 18 is connected to the further layer 17 and constitutes the press element side 5 of the water-absorbing belt 3. In the machine 1 the layer structure 18 is brought into contact with the press element 7. The layer structure 18 is optimized with regard to low wear and at the same time with regard to flow resistance by means of mechanical transmission.

Corresponding elements of the embodiments in the figures are denoted by the same reference numerals. The functions of such elements in the various figures correspond to each other, provided that they are not otherwise described and are not mutually inconsistent. And thus repetitive description will be omitted. It should be noted, however, that the different features of the illustrated embodiments can be interchanged and combined with one another. The invention is therefore not limited to the shown combination of features of the shown embodiments.

List of reference numerals

1 machine

2 fibrous web

3 Water absorption belt

4 breadth side

5 pressing element side

6 squeezing equipment

7 pressing element

8 cooperating elements, drying cylinders

9 Press nip

10 pressure shoe

11 outer cover

12 suction device

13 tangent line

14 degree angle

15 first layer

16 second layer

17 other layers

18-layer structure

19 Press felt

20 suction piece

21 cover

22 suction element

23 headbox

24 forming roller

25 external net and forming net

26 direction of travel

Claims

1. A machine (1) for producing a fibrous web (2) having at least one press device (6) comprising a press element (7) and a counter-element (8) having a closing surface for forming a press nip (9) and having a water-absorbing belt (3) with a web side (4) and an opposite press element side (5), which can be guided together with the fibrous web (2) through the press nip (9) in such a way that the fibrous web (2) separates from the web side (4) of the water-absorbing belt (3) at the end of the press nip and continues to run together with the counter-element (8),

it is characterized in that the preparation method is characterized in that,

the water-absorbing belt (3) is guided over a partial section by a press element (7) from the end of the press nip (9), and a suction device (12) for dewatering the water-absorbing belt (3) is provided on the press element side (5) of the water-absorbing belt (3) in the region of the fiber-free web of the water-absorbing belt (3).

2. Machine according to claim 1, characterized in that the press element (7) is constituted by a press roll with openings.

3. Machine according to claim 1, characterized in that the press element (7) is constituted by a shoe press unit.

4. Machine according to claim 3, characterized in that the shoe press unit comprises a water-permeable outer mantle (11) and a press shoe (10) arranged inside the outer mantle (11) and capable of being pressed against the mating element (8).

5. Machine according to claim 4, characterized in that the side of the outer mantle (11) facing the press element side (5) of the water-absorbing belt (3) has an open surface.

6. Machine according to claim 1 or 2, characterized in that the partial sections are selected such that the direction of the diverted water-absorbing belt (3) forms an angle (14) of more than 10 ° with a tangent (13) at the end of the press gap (9) on the counter element (8).

7. Machine according to claim 1 or 2, characterized in that the suction device (12) has a coating with a plurality of openings, which are embodied as bores and/or slits.

8. The machine according to claim 1 or 2, characterized in that the water-absorbing belt (3) comprises at least one first layer (15), a second layer (16) and a layer structure (18) arranged on the half facing the press element (7) as seen in the thickness direction, which layer structure has a higher specific flow resistance than the first layer (15) and/or the second layer (16).

9. Machine according to claim 8, characterized in that the first layer (15) constitutes a web side (4) and comprises a fibre lining made of plastic fibres.

10. Machine as in claim 9, characterized in that said second layer (16) is a woven layer and said first layer (15) is connected to the second layer (16).

11. Machine according to claim 8, characterized in that said layer structure (18) is associated with said second layer (16).

12. Machine according to claim 8, characterized in that the layer structure (18) constitutes the press element side (5).

13. Machine according to claim 8, characterized in that the water-absorbing belt (3) further comprises a further layer (17) for constituting the press element side (5), which further layer (17) is arranged on the half of the water-absorbing belt (3) facing the press element (7), which further layer comprises a fibre lining made of plastic fibres.

14. Machine according to claim 8, characterized in that said layer structure (18) is implemented as a film having a plurality of openings.

15. Machine according to claim 10, characterized in that the layer structure (18) is embodied as a fibre lining made of fibres having a fibre fineness of less than 3 dtex.

16. Machine according to claim 1, wherein the fibrous web (2) is a tissue web.

17. Machine according to claim 1, characterized in that the press element (7) is constituted by a press roll with a grooved and/or bored surface.

18. Machine according to claim 4, characterized in that the side of the mantle (11) facing the press element side (5) of the water-absorbing belt (3) has a grooved and/or drilled surface.

19. Machine according to claim 6, characterized in that said angle (14) is greater than 15 °.

20. Machine according to claim 6, characterized in that said angle (14) is in the range of 20 °.

21. Machine according to claim 9, characterized in that said first layer (15) is stitched to said second layer (16).

22. A method for producing a fibrous web (2) using at least one press device (6) comprising a press element (7) and a counter-element (8) having a closing surface for forming a press gap (9) and having a water-absorbing belt (3) with a web side (4) and an opposite press element side (5), which is guided together with the fibrous web (2) through the press gap (9) in such a way that the fibrous web (2) is separated from the web side (4) of the water-absorbing belt (3) at the end of the press gap and is moved further together with the counter-element (8),

it is characterized in that the preparation method is characterized in that,