EP1348804B1 - Tissue papermaking machine with a shoe press - Google Patents

Abstract

A tissue paper making machine has a de-watering press shoe (24) which is applied to a drying cylinder (22) forming a nip interface (28). The press shoe has a centre-zone (M) between two outer margins (R) which are esp. more flexible than the centre zone. Also claimed is a tissue paper making machine with a series of pressure jacks (26) applied to the shoe (24) lower surface. The shoe is progressively thinner (d) towards the outer margins (R) than in the centre section (M). The width of the outer margin is pref. 500 mm and is supported by pref. four pressure jacks (26).

Description

The invention relates to a machine for producing a tissue web with a shoe press unit having a press shoe, wherein the press shoe can be pressed against the jacket of a drying cylinder via a plurality of pressing elements to form a press nip, through which the tissue web to be formed or treated can be passed and wherein the plurality of pressing elements are arranged transversely to the web running direction.

The usual press shoes have a width across the width transverse to the web direction constant thickness.

However, in particular in the case of tissue machines with so-called Yankee drying cylinders, the problem now arises that the press nip does not run straight across the width, but has to adapt to the contour of the jacket of the Yankee cylinder in order, for example, to maintain constant dry content values over the width Tissuebahn to reach. The contour of a Yankee cylinder changes due to the vapor pressure inside as well as due to a thermal expansion of the end caps. If a press shoe is then pressed against the Yankee cylinder to form a press nip or press nip, the pressure pressure profile in the gap is no longer constant in the transverse direction, but deviates upwards or downwards at the edges. The press shoe must therefore be bent over the width seen. Although the press shoe is relatively thin and thus compared to a Sauganpresswalze has a relatively small bending moment of inertia, it opposes a respective bending moment too much resistance. As a result, the pressing pressure acting on the tissue web edges is greater than in the middle of the web. To counter this problem, an attempt has already been made to reduce the thickness of the press shoe uniformly across the width in order to achieve a smaller bending moment of inertia or moment of resistance. However, this measure does not result in production-related reasons to the desired result. Also by a different contact pressure At the edge area, the problem could not be completely solved because the contact forces of adjacent contact elements and correspondingly the residual errors were too large.

Shoe presses are known from DE 32 39 954, DE 196 42 943 and US Pat. No. 4,428,797, in which the press shoe is made thinner at its lateral edge regions than in the middle region of the press shoe. But the thinner edge areas are all outside the press nip.

From DE 196 42 049 a shoe press is further known, the press shoe is formed within the press nip in its two lateral edge regions thinner than in the central region. According to this document, a camber is to be achieved by the training, by which it is possible to press the press shoe by means of only one extending over the entire width of the press shoe pressing element generating a transverse to the web running direction pressing force against the counter roll in the shoe press.

From DE 100 32 251 a machine for the production of tissue paper with a Schupresseinheit is known. The shoe press unit has a press shoe which can be pressed against a drying cylinder by a plurality of pressing elements.

The aim of Erfingung is to provide a tissue machine of the type mentioned, with which the aforementioned problems are eliminated.

This object is achieved in a tissue machine of the type mentioned in that the press shoe within the press nip in its two lateral edge regions adjacent edge portions at least partially has a lower flexural rigidity than in its intermediate middle region and that at least the two edge regions associated pressing elements at least partially separately controllable.

A basic idea of the invention is thus to reduce the flexural rigidity in the edge region of the shoe, and to be able to set a desired pressing pressure profile by means of the pressing elements which can be controlled separately at least in the edge region.

In this case, the lower bending stiffness in question can be achieved, for example, in that the press shoe has a smaller thickness in the edge regions than in its intermediate region and / or the material of the press shoe is selected accordingly.

In the case of a reduction in thickness, for example, the press shoe thickness is reduced only in the peripheral areas.

According to a preferred practical embodiment of the press shoe according to the invention, a respective edge region of lower flexural rigidity has a width measured transversely to the machine direction of at most about 1000 mm, in particular of at most about 700 mm and preferably of at most about 500 mm. The width of a respective edge region may, for example, extend over two pressing elements, preferably over three pressing elements and in particular over four pressing elements.

In certain cases, it is advantageous if the thickness becomes increasingly smaller in a respective edge region towards the relevant shoe edge. In this case, the thickness in a respective edge region towards the relevant shoe edge, for example, gradually become smaller. The transition between the individual stages can in particular be continuous. In principle, however, such an embodiment is conceivable in which the thickness in a respective edge region to the relevant shoe edge is continuously or steadily smaller.

In an expedient practical embodiment, the press shoe has a plurality of local material recesses in a respective edge region. These may in particular be formed by cuts or the like, which may extend at least partially, in particular in the transverse direction or in the web running direction.

The material recesses may for example have an equal size. For example, the material recesses can be formed by cuts of constant depth.

In principle, however, the material recesses can also be formed by cuts of variable depth. Such is, for example Embodiment conceivable in which the incisions extend at least partially in the transverse direction and the incisions each have a depth to the respective shoe edge increasing.

The material recesses may also have at least partially a different size. In this case, they may be formed, for example, by cuts of different depths. Thus, e.g. the depth of transverse cuts extending to the relevant shoe edge become greater.

The material recesses formed for example by cuts can be arranged at the same distance or at different distances from each other. In the latter case, the material recesses may for example be arranged closer to the relevant shoe edge.

According to a preferred practical embodiment of the press shoe according to the invention, a corresponding reduction in thickness is provided only on the side of the press shoe facing away from the press nip.

In certain cases, however, it may also be advantageous if in each case a thickness reduction is provided both on the side facing away from the press nip side and on the side of the press shoe facing the press nip.

In principle, however, such a design is conceivable in which a corresponding reduction in thickness is provided only on the press nip facing side of the press shoe.

As already mentioned, in particular, a thickness reduction which is continuous with the relevant shoe edge can also be provided in a respective edge region. However, it is also conceivable, for example, a stepped reduction in thickness.

Preferably, the thickness reduction provided in a respective edge region is selected such that the bending stiffness of the press shoe decreases toward the relevant shoe edge.

The press shoe can be made in one or more parts.

Alternatively or additionally, the press shoe may in particular also consist of different materials. According to an expedient practical embodiment of the press shoe in the edge regions, for example, at least partially made of a flexurally softer material than in the central region.

Figur 1

eine schematische Längsschnittdarstellung einer einen Yankee-Zylinder mit zugeordnetem herkömmlichen Pressschuh umfassenden Schuhpresse im nicht belasteten Zustand,

Figur 2

eine schematische Längsschnittdarstellung der einen Yankee-Zylinder mit zugeordnetem herkömmlichen Pressschuh umfassenden Schuhpresse im Betriebszustand (Dampfdruck, Temperatur, Pressdruck),

Figur 3

eine schematische Längsschnittdarstellung einer erfindungsgemäßen Schuhpresse im Betriebszustand mit einem Yankee-Zylinder und einem diesem zugeordneten erfindungsgemäßen Pressschuh,

Figur 4

eine schematische Teildarstellung einer weiteren Ausführungsform des erfindungsgemäßen Pressschuhes, wobei nur auf der vom Pressspalt abgewandten Seite des Pressschuhes eine entsprechende Dickenreduzierung vorgesehen ist und die Dicke in einem jeweiligen Randbereich zum betreffenden Schuhrand hin stufenweise kleiner wird,

Figur 5

eine schematische Stirnansicht des Pressschuhes gemäß Figur 4,

Figur 6

eine schematische Teildarstellung einer weiteren Ausführungsform des erfindungsgemäßen Pressschuhes, wobei in einem jeweiligen Randbereich des Pressschuhes auf der vom Pressspalt abgewandten Seite eine Mehrzahl von sich in Bahnlaufrichtung erstreckenden Einschnitten vorgesehen ist,

Figur 7

eine schematische Teildarstellung einer weiteren Ausführungsform des erfindungsgemäßen Pressschuhes, wobei in einem jeweiligen Randbereich des Pressschuhes auf der dem Pressspalt zugewandten Seite eine zum jeweiligen Schuhrand hin stetige Dickenreduzierung vorgesehen ist,

Figur 8

eine schematische Teildarstellung einer weiteren Ausführungsform des erfindungsgemäßen Pressschuhes, wobei in einem jeweiligen Randbereich des Pressschuhes auf der vom Pressspalt abgewandten Seite sich in Querrichtung erstreckende Einschnitte vorgesehene sind, deren Tiefe zum jeweiligen Schuhrand hin zunimmt,

Figur 9

eine schematische Stirnansicht des Pressschuhes gemäß Figur 8 in Richtung des Pfeils "A" der Figur 8 und

Figur 10

eine schematische Teildarstellung einer weiteren Ausführungsform des erfindungsgemäßen Pressschuhes, wobei der Pressschuh aus unterschiedlichen Materialien besteht.

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

FIG. 1

a schematic longitudinal sectional view of a Yankee cylinder with associated conventional press shoe comprehensive shoe press in the unloaded state,

FIG. 2

a schematic longitudinal sectional view of a Yankee cylinder associated with conventional press shoe shoe press in the operating state (vapor pressure, temperature, pressure),

FIG. 3

a schematic longitudinal sectional view of a shoe press according to the invention in the operating state with a Yankee cylinder and a press shoe associated therewith according to the invention,

FIG. 4

a schematic partial view of another embodiment of the press shoe according to the invention, wherein only on the side facing away from the press nip side of the press shoe, a corresponding reduction in thickness is provided and the thickness in a respective edge region to the relevant shoe edge gradually becomes smaller,

FIG. 5

a schematic end view of the press shoe according to Figure 4,

FIG. 6

a schematic partial view of another embodiment of the press shoe according to the invention, wherein in a respective edge region of the press shoe on the from Pressing gap facing away from a plurality of extending in the web running direction cuts is provided

FIG. 7

a schematic partial view of another embodiment of the press shoe according to the invention, wherein in a respective edge region of the press shoe on the side facing the press nip a continuous thickness reduction is provided for the respective shoe edge,

FIG. 8

a schematic partial view of a further embodiment of the press shoe according to the invention, wherein in a respective edge region of the press shoe on the side facing away from the press nip transversely extending incisions are provided whose depth increases towards the respective shoe edge,

FIG. 9

a schematic end view of the press shoe according to Figure 8 in the direction of the arrow "A" of Figure 8 and

FIG. 10

a schematic partial view of another embodiment of the press shoe according to the invention, wherein the press shoe consists of different materials.

Figure 1 shows a schematic longitudinal sectional view of a drying cylinder 10, in particular Yankee cylinder, with associated conventional press shoe 12 comprehensive shoe press 14 in the unloaded state. The jacket 16 of the drying cylinder 10 is thus not bent in the present case.

The press shoe 12 is pressed against the drying cylinder 10 by at least one row of pressing elements 18. The press shoe 12 forms with the drying cylinder 10 the press nip 20, through which the tissue web is guided together with at least one carrier tape (not shown). The tissue web preferably runs together with a water-impermeable press jacket and a felt (water-absorbent) through this press nip or nip 20.

Figure 2 shows a comparable to that of Figure 1 representation of the shoe press 14 in the loaded state, i. in the operating state. In operation, the contour of the drying cylinder 10 deformed by the in-cylinder pressure (steam) and a greater expansion of the front cover of the drying cylinder due to the steam temperature and by other design-related factors. Furthermore, the contour of the drying or Yankee cylinder 10, in particular in the region of the press nip 20, is influenced by different pressing pressures or line forces. The jacket 16 of the drying cylinder 22 is here so bent. As can be seen with reference to FIG. 2, a corresponding deflection also results in the press shoe 12.

The conventional press shoe 12 shown in FIGS. 1 and 2 has a thickness which is constant over the width.

FIG. 3 shows a schematic longitudinal section of a shoe press 21 according to the invention with a drying cylinder 22, in particular a Yankee cylinder, and a press shoe 24 according to the invention with associated pressing elements 26 arranged in at least one row extending transversely to the web running direction and over which the press shoe 24 is pressed against the drying cylinder 22. The press shoe 24 can be made in one or more parts be. In this figure 3, the shoe press 22 is shown in the operating state.

The press shoe 24 forms with the drying cylinder 22 the press nip 28, through which the tissue web is guided together with at least one carrier tape (not shown). Preferably, the tissue web again runs along with a water-impervious press cover and a felt (water-absorbent) through this press nip or nip 28.

The jacket 30 of the drying cylinder 22 is bent in the illustrated operating state. As can be seen from FIG. 3, a corresponding deflection also results again for the press shoe 24.

In the present case, the two lateral edge regions R of the press shoe 24 each have a plurality of, for example, three pressing elements 26 ₁ - 26 ₃ assigned. The middle region can be assigned pressing elements 26 _z (cf., FIGS. 4 and 6).

As can be seen with reference to FIG. 3, press shoe 24 has, in its two lateral edge regions R adjacent to the web edges, at least in sections a smaller thickness d than in its intermediate region M located therebetween.

It can, as can be seen from the left part of Figure 3, to form a corresponding reduction in thickness 34, for example, on the side facing away from the press nip 28 side of the press shoe 24 material recesses 32 or the like may be provided in the present case, for example in Stretch web direction.

As can be seen from the right-hand part of FIG. 3, an at least substantially continuous thickness reduction 34 can also be provided in a respective edge region R. This thickness reduction 34 is also in the present case e.g. again provided on the side facing away from the press nip 28 side of the press shoe 24. As shown in FIG. 3, the transition from the middle region M into the thickness-reduced edge region R can, for example, run continuously.

At least the two edge regions R of the press shoe 24 associated pressing members 26 are at least partially controlled separately. The particular hydraulic pressure elements 26 _i - 26 ₃ can thus be applied in particular with different pressures, whereby correspondingly different contact forces are generated. In this case, the pressing elements can be controlled so that in the press nip 28 results in an at least substantially uniform compression cross-pressure profile or line force profile. In principle, it is also possible to associate pressing elements 26 _z corresponding to the central region M (see FIGS. 4 and 5). These middle contact pressure elements 26 _z can in principle be at least partially separately controlled again.

A respective edge region R of lesser thickness d may, for example, have a width measured transversely to the machine direction of at most about 1000 mm, in particular of at most about 700 mm and preferably of at most about 500 mm.

Figure 4 shows a schematic partial view of a further embodiment of the press shoe 24 according to the invention, in which again only on the side facing away from the press nip side a corresponding reduction in thickness 34 is provided. In the present case, the thickness in a respective edge region R becomes gradually smaller towards the relevant shoe edge R '. It can take place between the individual stages 34 ', as shown, for example, a continuous transition.

A respective correspondingly reduced thickness edge region R are again assigned separately controllable pressing elements 26 ₁ , 26 ₂ . In the present case, two such pressing elements 26 ₁ , 26 _{2 are} assigned to a respective edge region R, for example. The middle region M of the press shoe is acted upon by pressing elements 26 _z , which can also be at least partially separately controlled again.

FIG. 5 shows a schematic end view of the press shoe 24 according to FIG. 4.

FIG. 6 shows, in a schematic partial representation, a further embodiment of the press shoe 24 according to the invention, in which again a respective reduction in thickness 34 is again provided only on the side facing away from the press nip. In the present case, a plurality of incisions 32 extending here, for example in the web running direction, are provided in a respective edge region R. The edge regions R are each again assigned at least partially separately controllable pressing elements 26 ₁ - 26 ₃ . Also, the central region is again acted upon by corresponding pressing elements 26 _z .

FIG. 7 shows, in a schematic partial representation, a further embodiment of the press shoe 24 according to the invention, but in this case the corresponding reduction in thickness 34 on the press nip facing side of the press shoe 24 is provided. In this case, the thickness d of the press shoe 24 becomes increasingly smaller in a respective edge region R for the relevant shoe edge R '.

Also in the present case, in particular the edge regions R are again assigned separately controllable pressing elements (not shown).

FIG. 8 shows, in a schematic partial representation, a further embodiment of the press shoe 24 according to the invention, in which, however, the respective thickness reduction 34 in the edge regions R is again provided on the side of the press shoe 24 facing away from the press nip. In this case, transversely extending incisions 34 are provided, the depth of which increases towards the respective shoe edge R '.

FIG. 9 shows a schematic end view of a part of the press shoe 24 according to FIG. 8 in the direction of the arrow "A" of FIG. 8.

FIG. 10 shows, in a schematic partial representation, a further embodiment of the press shoe 24 according to the invention, in which case the press shoe 24 consists of different materials. It is possible, for example, that the press shoe 24 in the edge region R consists partly or entirely of a material that is more flexible than in the middle region M.

As can be seen with reference to FIG. 10, press shoe 24 may consist, for example, of a first material 36, eg brass or the like, and a carrier material 38, eg fiber-reinforced plastic or the like. In the present embodiment, the carrier material in the edge region R is reduced in thickness.

LIST OF REFERENCE NUMBERS

10

Drying cylinder, Yankee cylinder

12

press shoe

14

shoe press

16

coat

18

presser

20

Press nip, nip

21

shoe press

24

press shoe

26

presser

28

Press nip, nip

30

coat

32

Material recess, incision

34

thickness reduction

34 '

step

36

material

38

support material

M

middle area

R

border area

R '

Shoe edge

d

thickness

Claims (32)

1. Machine for producing a tissue web, comprising a shoe press unit having a press shoe (24), it being possible for the press shoe (24) to be pressed against the circumference (30) of a drying cylinder (10) by a plurality of pressing elements (26), forming a press nip (28), through which the tissue web to be formed or to be treated can be led, and the plurality of pressing elements being arranged transversely with respect to the web running direction, characterized in that, within the press nip (28), in its two lateral edge regions (R) adjacent to the web edges, the press shoe (24) has a lower flexural rigidity, at least in some sections, than in its central region (M) lying between them, and in that at least the pressing elements (26) assigned to the two edge regions (R) can be activated at least partly separately.
2. Machine for producing a tissue web according to Claim 1, characterized in that the press shoe has a lower thickness (d) in the edge regions (R) than in its central region (M) lying between them.
3. Machine for producing a tissue web according to Claim 1, characterized in that the material of the press shoe (24) in the edge regions (R) is selected in such a way that the press shoe (24) has a lower flexural rigidity in these edge regions (R) than in its central region (M) lying between them.
4. Machine for producing a tissue web according to one of the preceding claims, characterized in that a respective edge region (R) of lower flexural rigidity has a width measured transversely with respect to the machine running direction of at most about 1000 mm, in particular of at most about 700 mm and preferably of at most about 500 mm.
5. Machine for producing a tissue web according to one of the preceding claims, characterized in that the width of a respective edge region (R) extends over two pressing elements, preferably over three pressing elements and in particular over four pressing elements.
6. Machine for producing a tissue web according to one of the preceding claims, characterized in that the thickness (d) in a respective edge region (R) becomes continuously smaller towards the relevant shoe edge (R').
7. Machine for producing a tissue web according to Claim 6, characterized in that the thickness (d) in a respective edge region (R) becomes smaller in steps towards the relevant shoe edge (R').
8. Machine for producing a tissue web according to Claim 7, characterized in that a continuous transition is made between the individual steps (34').
9. Machine for producing a tissue web according to Claim 6, characterized in that the thickness (d) in a respective edge region (R) becomes smaller, continuously or steadily, at least in some sections, towards the relevant shoe edge (R').
10. Machine for producing a tissue web according to one of the preceding claims, characterized in that the press shoe in a respective edge region (R) has a plurality of local material cut-outs (32).
11. Machine for producing a tissue web according to Claim 10, characterized in that the material cut-outs are formed by incisions (32).
12. Machine for producing a tissue web according to Claim 11, characterized in that the incisions (32) extend at least partly in the transverse direction.
13. Machine for producing a tissue web according to either of Claims 11 and 12, characterized in that the incisions (32) extend at least partly in the web running direction.
14. Machine for producing a tissue web according to one of Claims 10 to 13, characterized in that the material cut-outs (32) are of the same size.
15. Machine for producing a tissue web according to one of Claims 10 to 14, characterized in that the material cut-outs (32) are formed by incisions of constant depth.
16. Machine for producing a tissue web according to one of Claims 10 to 14, characterized in that the material cut-outs (32) are formed by incisions of variable depth.
17. Machine for producing a tissue web according to Claim 16, characterized in that the incisions (32) extend at least partly in the transverse direction and the incisions each have a depth increasing towards the relevant shoe edge (R').
18. Machine for producing a tissue web according to one of Claims 10 to 13 and 15 to 17, characterized in that the material cut-outs (32) have a different size, at least to some extent.
19. Machine for producing a tissue web according to one of Claims 10 to 14 and 16 to 18, characterized in that the material cut-outs (32) are formed by incisions of different depth.
20. Machine for producing a tissue web according to Claim 19, characterized in that the depth of the incisions (32) becomes greater towards the relevant shoe edge (R').
21. Machine for producing a tissue web according to one of Claims 10 to 20, characterized in that the material cut-outs (32) are arranged at the same distance from one another.
22. Machine for producing a tissue web according to one of Claims 10 to 20, characterized in that the material cut-outs (32) are arranged more densely towards the relevant shoe edge (R').
23. Machine for producing a tissue web according to one of Claims 2 and 4 to 22, characterized in that an appropriate thickness reduction (34) is provided only on that side of the press shoe which faces away from the press nip (28).
24. Machine for producing a tissue web according to one of Claims 2 and 4 to 22, characterized in that a thickness reduction (34) is in each case provided both on the side of the press shoe facing away from the press nip (28) and on the side facing the press nip.
25. Machine for producing a tissue web according to one of Claims 2 and 4 to 22, characterized in that an appropriate thickness reduction (34) is provided only on that side of the press shoe (24) which faces the press nip (28).
26. Machine for producing a tissue web according to one of Claims 2 and 4 to 25, characterized in that a thickness reduction (34) that is continuous towards the relevant shoe edge (R') is provided in a respective edge region (R).
27. Machine for producing a tissue web according to one of Claims 2 and 4 to 26, characterized in that the thickness reduction (34) provided in a respective edge region (R) is chosen such that the flexural rigidity of the press shoe (24) decreases towards the relevant shoe edge (R').
28. Machine for producing a tissue web according to one of the preceding claims, characterized in that the press shoe is designed in one piece.
29. Machine for producing a tissue web according to one of Claims 1 to 27, characterized in that the press shoe is designed in many parts.
30. Machine for producing a tissue web according to one of the preceding claims, characterized in that the press shoe consists of different materials.
31. Machine for producing a tissue web according to one of the preceding claims, characterized in that, in the edge regions (R), the press shoe consists at least partly of a more flexible material than in the central region (M).
32. Machine for producing a tissue web according to one of the preceding claims, characterized in that the central region (M) is assigned pressing elements (26) which can be activated at least partly separately.

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