DE10233922A1 - shoe press - Google Patents

Abstract

A shoe press of a machine for the production or treatment of a fibrous web, in particular paper or cardboard web, comprises a shoe press unit which has at least one press shoe and a flexible press belt guided over it and, with a moving counter surface, forms a press nip extended in the direction of web travel, the area between the Press shoe and the press belt is supplied with lubricating fluid. At least part of the press shoe of the shoe press unit is separated from the lubricating fluid by a thermal insulating layer. The thermal insulating layer can at the same time also have increased compressibility and / or increased damping properties.

Description

The invention relates to a shoe press of a machine for the production or treatment of a fibrous web, in particular paper or cardboard web, with a shoe press unit, which comprises at least one press shoe and a flexible press belt guided over it and forms a press nip extended in the web running direction with a moving counter surface, the Area between the press shoe and the press belt is supplied with lubricating fluid. It also relates to a shoe press of the type specified in the preamble of claim 13 DE 198 60 687 A1 described.

Shoe presses are already known where the pressure or pressure shoe has a series of pressure pistons is pressed against a counter roller, so that a uniform pressure over the Width appears secure, especially since thermal influences the line force distribution through thermal insulation built into the pressure shoe should be switched off. Nevertheless, there are relatively narrow limits Moisture and / or dry peaks in the moisture cross profile on what is extremely unsatisfactory and ultimately inexplicable is.

The conditions on a press shoe used in combination with a Yankee cylinder result, for example, from the 1 , in which a conventional shoe press is shown in a schematic representation.

According to this 1 includes the shoe press 10 one by a shoe press roll 12 formed shoe press unit with a Yankee cylinder 14 an extended press nip in the web running direction L. 16 forms through which the fibrous web 18 for example together with a press felt 20 is led.

The shoe press roller 12 includes an all-round flexible press jacket 22 as well as a press shoe 24 with assigned support elements 26 that over rows of pressure pistons 28 are applied to the inside of the press jacket 22 provided press shoe 24 against the Yankee cylinder 14 to press. In between the press jacket 22 and the Yankee cylinder 14 formed press nip 16 lies the fiber web 18 here on the of the Yankee cylinder 14 assigned side of the press felt 20 ,

Between the press shoe 24 and the flexible press jacket 22 An oil film 30 results due to, for example, hydrodynamic and / or hydrostatic lubrication.

Between the two facing support surfaces 32 of the support elements 22 as well as the press shoe 24 is a thermal insulation layer 34 intended.

The fibrous web 18 can, for example, also be sandwiched between two felts or, for example, a felt and, for example, a water-impermeable transfer belt.

The thermal insulation layer 34 in this known shoe press is therefore below the press shoe 24 , Differences in temperature can therefore affect the entire width of the shoe.

The ratios of the area between the Press shoe and the press belt produced lubricating oil film are among others from depending on the shape of the press shoe, especially at the beginning of the gap. Despite considerable effort with regard to a sufficient dimensional accuracy results in the local oil film thickness a significant spread. At a point with a smaller film thickness, for example occurs a larger viscous Shear friction and heat development on who the above it In addition, the smaller mass of the thinner oil film heats up disproportionately. As a result, the one that is usually made of bronze Press shoe locally heated considerably becomes. This is due to the insulation between the upper part and the base body temperature increase from the main body kept away, which makes it spacious extensive errors in the moisture cross profile avoided to some extent can be. As a result of the inherent stiffness of the bronze upper part, the local overtemperature may result However, the press shoe can be thermally deformed so that it arched towards the counter roller and a line spray gun is produced locally. Conversely the situation with an above average thick oil film.

In addition, the effect of a deviation of the press nip thickness on the line force distribution is undesirably high due to the very high bedding number of the shoe press nip. The bedding number [N / mm ² ] is a measure of the compressibility of a material or an arrangement. For example, a bedding figure of 1 N / mm ^{2 means} a yield of 1 mm with a line force of 1 N / mm. Every lowering of this bed number would make the press nip more forgiving with regard to the line force distribution.

The invention lies among others based on the task of an improved shoe press of the beginning to create the type mentioned, in which the above-mentioned problems are eliminated. In particular, it should also even out the Width of the shoe press resulting pressure profile and a reduction or avoiding transverse temperature differences and their impact in the transverse direction on the pressure cross profile can be achieved.

This task comes after a first Aspect of the invention essentially solved in that at least one part of the press shoe of the shoe press unit through a thermal insulation layer is separated from the lubricating fluid.

According to the invention, at least one Part of the press shoe of a shoe press between the press surface and the support surface is separated from the lubricating fluid in the area between the press belt or press jacket and the shoe by a thermal insulating layer.

The thermal insulating layer preferably extends generally in the direction of web travel.

According to a preferred practical embodiment the shoe press according to the invention the press shoe on its side facing the press nip with a provided with a thermally insulating coating. In the present case the thermal insulating layer is therefore a thermal one insulating coating on the press surface of the press nip Press shoe, causing the effects of different lubricating fluid or oil heating largely kept away from the load-bearing substructure of the press shoe become. The formation of a respective local overpressure or underpressure leveled. The wet cross profile obtained after the shoe press becomes level and stable.

The thermally insulating coating can be provided with a wear-resistant coating. The press shoe can thus be designed in particular three layers. The wear-resistant Characteristic coating can consist of metal powder or the like, for example.

According to an expedient practical embodiment the shoe press according to the invention is the press shoe due to the thermal insulation layer at least essentially divided into two shoe parts. Here, the thermal insulation layer at least essentially completely cut through the press shoe.

So it is especially one such embodiment conceivable, in which the press shoe through the thermal insulation layer into a shoe part facing the press nip and one from the press nip facing shoe part is divided.

The thermal insulation layer can especially equidistant to the contour of the press surface facing the press nip Press shoes run.

In addition, in certain cases of advantage if the shoe part facing the press nip is less Thickness is the part of the shoe facing away from the press nip.

In an expedient embodiment, the Shoe part facing the press nip and the shoe part facing away from the press nip Shoe part made of different materials.

The thermal insulation layer or thermally insulating coating can for example be made of plastic, Ceramic, CFRP, a composite and / or any other low thermally conductive Material.

According to a second aspect of Invention is a shoe press in the preamble of the claim 13 proposed type, which is characterized in that the press shoe on its side facing the press nip with an elevated one compressibility and / or increased damping properties provided coating and / or by an appropriate layer is divided into two shoe parts to prevent vibrations in the press nip to counteract or prevent generated pressure.

This will make the bed number of the shoe press nip reduced and due to deviations in the press gap thickness conditional errors in line force distribution reduced.

This second aspect of the invention is for both viewed as well as in combination with the first aspect of Invention of considerable practical advantage.

What a possible combination of these two As far as aspects are concerned, such an implementation of the Shoe press according to the invention conceivable in which the coating or layer of increased compressibility and / or increased damping properties simultaneously through the thermal insulating layer or thermally insulating coating is formed. The coating or Layer can therefore in particular consist of a poorly heat-conducting compressible material.

To achieve the desired increased compressibility or, increased damping properties the coating or layer is preferably porous. there can the coating or layer, for example, gas-filled bubbles have or with tubular channels be provided, which preferably extend transversely to the web running direction. The tubular ones channels can at least in a central region viewed in the pressing direction Coating or layer or, for example, at least in one area of the coating adjacent to the press shoe his. In the latter case, those are provided in the coating tubular channels on the press shoe side preferably limited by the press shoe.

The press shoe can thus, for example, be provided with a compressible coating or layer, with the result that the bed number of the shoe press nip is reduced and the errors in the line force distribution that occur when there are deviations in the press nip thickness are reduced. Since the material compressibility of the usual coating or layering materials is not sufficient for this purpose, the hollow or displacement material must be given the possibility to evade there and thus at least become more compressible in its effect by means of constructed hollow or displacement volumes. If the compressibility constructed in this way were to be placed in the press jacket, it would be compressed and relaxed again with each nip pass and subjected to a correspondingly high dynamic load. If the required compressibility is now laid in the relevant coating or layer of the press shoe, the dynamic load is reduced to Fluctuation range of the local pressing pressure, where it is ideally zero. The respective hollow or displacement volumes are achieved, for example, by compressible gas bubbles (porosity) enclosed in the coating or layer and / or tubular, transverse channels arranged in the coating or layer, which can be filled with gas or liquid.

With the corresponding to the second aspect of the invention solution can including the previously inexplicable short-wave interference and instabilities can be reduced in the moisture cross profile after the press.

As already mentioned is of particular advantage especially any combination of the two aspects the invention possible in which the coating or the cover, in particular, from a bad thermally conductive Compressible material can be made.

With the shoe press unit it can are in particular a shoe press roller.

The counter surface is preferably by a Counter roll or a drying cylinder, in particular a Yankee cylinder, educated.

The shoe press according to the invention is special Advantage applicable for graphic papers, cardboard and packaging papers, tissue and / or like.

The invention is explained below of embodiments explained in more detail with reference to the drawing; in this show:

1 a schematic partial representation of a conventional shoe press,

2 2 shows a schematic partial illustration of an embodiment of the shoe press according to the invention with a press shoe which is provided on its side facing the press nip with a thermally insulating coating,

3 is a schematic partial representation of a with the embodiment according to 2 comparable further embodiment of the shoe press according to the invention, in which the thermally insulating coating is provided with a wear-resistant cover,

4 1 shows a schematic partial representation of a further embodiment of the shoe press according to the invention with a press shoe which is divided into two shoe parts by a thermal insulation layer,

5 2 shows a schematic partial representation of a further embodiment of the shoe press according to the invention with a press shoe which is provided with a porous, gas-filled bubble coating,

6 2 shows a schematic partial illustration of a further embodiment of the shoe press according to the invention with a press shoe which has a porous coating which is provided with tubular channels which extend transversely to the web running direction and are provided in a central region of the coating when viewed in the pressing direction,

7 a partial schematic representation of a further embodiment of the shoe press according to the invention with a press shoe which has a porous coating which is provided with tubular channels extending transversely to the web running direction, but which is provided here in an area adjacent to the press shoe and delimited on the press shoe side by the press shoe are and

8th a purely schematic representation of the advantages achieved with a press shoe according to the invention with a thermally insulating coating compared to a press shoe without a thermally insulating coating.

2 shows a schematic representation of an embodiment of the shoe press according to the invention 36 , Such a shoe press 36 can be provided in particular in a machine for producing or treating a fibrous web, for example paper or cardboard web and in particular tissue or hygiene web. Such a shoe press is particularly advantageous 36 applicable for graphic papers, cardboard and packaging papers, tissue and / or the like.

According to 2 includes the shoe press 36 one here, for example, by a shoe press roll 38 formed shoe press unit with a moving counter surface 40 an extended press nip in the web running direction L. 42 forms. In the present case it is the counter surface 40 by a counter roll and in particular by a drying cylinder 44 formed, which can be, for example, a Yankee cylinder. The fibrous web 46 , here for example a paper web, is treated accordingly by the extended press nip 42 guided.

The shoe press roller 38 comprises a press jacket formed by a flexible circumferential press belt 48 and a press shoe 50 , which can be acted upon by pressing elements and via which the flexible press jacket 48 against the counter roller 44 can be pressed. The press shoe is on its underside 50 with thermal insulation 52 Mistake.

As with the 2 can be seen, the fibrous or paper web 46 for example together with a felt 54 through the press nip 42 be led.

The area between the press shoe 50 and the press belt 48 is with lubricating fluid such as especially lubricating oil 56 provided.

At least part of the press shoe 50 the shoe press unit 38 is through a thermal insulating layer or thermally insulating coating 58 of that in the area between press shoe 50 and press belt 48 provided lubricating fluid 56 Cut. This thermal insulating layer or thermally insulating coating extends 58 generally in web running direction L.

In the present case, the press shoe 50 on its the press nip 42 facing side with a thermally insulating coating 58 Mistake.

The thermally insulating coating 58 can simultaneously have increased compressibility and / or increased damping properties.

As with the 2 can be seen, the thermally insulating coating 58 in addition to thermal insulation 52 be provided on the bottom of the shoe.

3 shows a schematic partial representation of one with the embodiment according to 2 comparable further embodiment of the shoe press according to the invention, in which case the thermally insulating coating 58 with a wear-resistant coating 60 is provided.

The thermal insulation 52 (see. 2 ) on the bottom of the shoe is missing in the present embodiment.

4 shows a schematic partial representation of a further embodiment of the shoe press according to the invention. In this case, the press shoe 50 through a thermal insulation layer 58 who the press shoe 50 in the present exemplary embodiment cuts at least substantially completely into a press nip 42 (cf. also 2 ) facing upper part of the shoe 62 and one from the press nip 42 facing away lower shoe part 64 divided.

Different from this one 4 shown, the thermal insulation layer 58 in particular also equidistant to the contour of the press nip 42 facing press surface of the press shoe 50 run.

As with the 4 can be seen, it has the press nip 42 (see also 2 ) facing shoe part 62 in the present case a smaller thickness than that of the press nip 42 facing shoe part 64 ,

The thermal insulation layer 58 can in particular also have increased compressibility and / or increased damping properties.

The two through the shift 58 separate shoe parts 62 . 64 can consist of different materials.

5 shows a schematic partial representation of a further embodiment of the invention. Shoe press. In this case, the press shoe 50 or the press shoe upper with a porous, gas-filled bubbles 66 having coating 58 Mistake. Between the coating 58 of the press shoe 50 and the press jacket 48 is the lubricating or oil film 56 educated.

The coating 58 thus again has increased compressibility and / or increased damping properties. In particular, it can also be thermally insulating.

6 shows a schematic partial representation of one with the execution according to 5 comparable embodiment, in which the porosity of the coating 58 however, through tubular channels extending transversely to the web running direction L. 68 is achieved. In the present case, these are channels 68 in a central region of the coating when viewed in the pressing direction 58 intended.

The coating also has in the present case 58 again increased compressibility and / or increased damping properties. In particular, it can also be thermally insulating.

7 shows a schematic partial representation of one with the execution according to 6 comparable further embodiment, in the present case the channels extending transversely to the web running direction L. 68 but in one to the press shoe 50 adjacent area of the coating 58 provided and on the press shoe side by the press shoe 50 or the upper part of the press shoe is limited.

In the present case, too, the coating 58 thus again increased compressibility and / or increased damping properties. In particular, it can also be thermally insulating.

8th shows a schematic representation of the behavior of a press shoe according to the invention 50 with thermally insulating coating 58 compared to a press shoe without such a thermally insulating coating. Part a) shows the 8th is a schematic cross-sectional view of a section of the press shoe, cut in a plane transverse to the web running direction L, and part b) of the 8th a side view of the press shoe in question.

A stable lubricating film is all in one wide range of thickness possible, the feed conditions at the beginning of the gap are essential. Yet there may be scattering of the local lubricating fluid or oil film thickness come.

For example, find "A" (see part a) of the 8th ) a stronger warming takes place, so there is the following effect, which in part a) the 8th is referred to as "Effect 1": The temperature becomes higher than in the neighboring areas. As a result, the press shoe expands 50 locally and becomes correspondingly thicker. Accordingly, the press nip or gap becomes narrower. The pressure increases in this area, which results in a so-called "peak" in the moisture cross profile.

In addition, there is another effect that in part a) 8th is marked as "Effect 2".

With regard to this second effect, it should be noted that the temperature in the area of the contour surface of the press shoe is considered over the shoe thickness 50 becomes higher than in the area of the Stützele ments 70 , Due to a bimetallic effect, the press shoe is curved 50 up. The press nip or gap becomes narrower accordingly. The baling pressure rises again, which again brings a "peak" in the moisture cross profile.

Based on 8th can now be seen that the "peaks" mentioned in a press shoe 50 with a thermally insulating coating according to the invention 58 be significantly reduced or leveled.

10

shoe press

12

Shoe press roll

14

Backing roll Yankee cylinder

16

extended press nip

18

Fibrous web

20

press felt

22

flexible press cover

24

press shoe

26

support element

28

Anpresskolbenreihen

30

oil film

32

support surface

34

thermal insulating

36

shoe press

38

Shoe press unit Shoe press roll

40

counter surface

42

press nip

44

Backing roll Drying cylinder, Yankee cylinder

46

Fibrous web

48

Press belt, press cover

50

press shoe

52

thermal insulation

54

felt

56

Lubricating fluid, Oil, Grease film, oil film

58

thermal Insulating layer, thermally insulating coating

tung

60

wear-resistant coating

62

the Shoe part facing the press gap, upper shoe part

64

from Shoe part facing away from press nip, lower shoe part

66

gas-filled bubbles

68

tubular channels

 70

support element

Claims (23)

Shoe press ( 36 ) a machine for producing or treating a fibrous web ( 46 ), in particular paper or cardboard web, with a shoe press unit ( 38 ) who have at least one press shoe ( 50 ) and a flexible press belt guided over it ( 48 ) and with a moving counter surface ( 40 ) a press nip extended in the direction of web travel (L) ( 42 ), the area between the press shoe ( 50 ) and the press belt ( 48 ) with lubricating fluid ( 56 ), characterized in that at least part of the press shoe ( 50 ) of the shoe press unit ( 38 ) by a thermal insulation layer ( 58 ) of the lubricating fluid ( 56 ) is separated. Shoe press according to claim 1, characterized in that the thermal insulating layer ( 58 ) extends generally in the direction of web travel (L). Shoe press according to claim 1 or 2, characterized in that the press shoe ( 50 ) on its press nip ( 42 ) facing side with a thermally insulating coating ( 58 ) is provided. Shoe press according to claim 3, characterized in that the thermally insulating coating ( 58 ) with a wear-resistant coating ( 60 ) is provided. Shoe press according to claim 4, characterized in that the wear-resistant coating ( 60 ) consists of metal powder or the like. Shoe press according to claim 1 or 2, characterized in that the press shoe ( 50 ) due to the thermal insulation layer ( 58 ) is at least essentially divided into two shoe parts. Shoe press according to claim 6, characterized in that the thermal insulating layer ( 58 ) the press shoe ( 50 ) at least essentially completely cuts through. Shoe press according to claim 6 or 7, characterized in that the press shoe ( 50 ) due to the thermal insulation layer ( 58 ) in the press nip ( 42 ) facing shoe part ( 62 ) and one from the press nip ( 42 ) facing shoe part ( 64 ) is divided. Shoe press according to one of the preceding claims, characterized in that the thermal insulating layer ( 58 ) equidistant to the contour of the press nip ( 42 ) facing press surface of the press shoe ( 50 ) runs. Shoe press according to claim 8 or 9, characterized in that the press nip ( 42 ) facing shoe part ( 62 ) has a smaller thickness than that of the press nip ( 42 ) facing away shoe part ( 64 ). Shoe press according to one of the preceding claims, characterized in that the the press nip ( 42 ) facing shoe part ( 62 ) and that of the press nip ( 42 ) facing away shoe part ( 64 ) consist of different materials. Shoe press according to one of the preceding claims, characterized in that the thermal insulating layer or thermally insulating coating ( 58 ) consists of plastic, ceramic, CFRP, a composite and / or the like. Shoe press ( 36 ) a machine for producing or treating a fibrous web ( 66 ), in particular paper or cardboard web, with a shoe press unit ( 38 ) that have at least one press shoe ( 50 ) and a flexible press belt guided over it ( 48 ) and with a moving counter surface ( 40 ) a press nip extended in the direction of web travel (L) ( 42 ), in particular according to one of the preceding claims, characterized in that the press shoe ( 50 ) on its press nip ( 42 ) facing side with a coating having increased compressibility and / or increased damping properties ( 58 ) and / or by an appropriate layer ( 58 ) in two shoe parts ( 62 . 64 ) is divided to prevent vibrations in the press nip ( 42 ) to counteract or prevent generated pressing pressure. Shoe press according to claim 13, characterized in that the coating or layer ( 58 ) increased compressibility and / or increased damping properties at the same time through the thermal insulating layer or thermally insulating coating ( 58 ) is formed. Shoe press according to claim 14, characterized in that the coating or layer ( 58 ) consists of a poorly heat-conductive compressible material. Shoe press according to one of the preceding claims, characterized in that the coating or layer ( 58 ) is porous. Shoe press according to claim 16, characterized in that the coating or layer ( 58 ) gas-filled bubbles ( 66 ) having. Shoe press according to one of the preceding claims, characterized in that the coating or layer ( 58 ) with tube-like channels ( 68 ) is provided. Shoe press according to claim 18, characterized in that the tubular channels ( 68 ) extend across the web running direction (L). Shoe press according to claim 18 or 19, characterized in that the tubular channels ( 68 ) at least in a central region of the coating or layer when viewed in the pressing direction ( 58 ) are provided. Shoe press according to claim 18 or 19, characterized in that the coating ( 58 ) with tube-like channels ( 68 ) is provided, which is at least in one on the press shoe ( 50 ) adjacent area are provided. Shoe press according to claim 21, characterized in that the tubular channels ( 68 ) on the press shoe side through the press shoe ( 50 ) are limited. Shoe press according to one of the preceding claims, characterized in that the shoe press unit is formed by a shoe press roll ( 38 ) is formed.