EP1342838A1 - Machine for manufacturing a tissue web - Google Patents

Abstract

The machine for the production of a tissue paper web has a press gap between a drying cylinder and especially a Yankee cylinder, and a press shoe assembly (10) with a number of independent hydraulic press units (16) against the drying cylinder in at least one row across the direction (L) of web travel. A monitor (18) measures the pressure applied by the press units, at least at the two side edges of the press gap, and a display unit (26) displays the registered pressures (26') at each measurement point (24). A control unit gives local pressure corrections from the edge pressure measurements.

Description

The invention relates to a machine for producing a tissue web, with a press nip which is formed between a drying cylinder, in particular a Yankee cylinder, and a press shoe arrangement which can be pressed against the drying cylinder via a plurality of pressing elements which extend in at least one row transverse to the web running direction are arranged.

So far, press shoes have been pressed evenly across the width or with less pressure at the edges.

However, the contour of a Yankee drying cylinder of a tissue machine now changes as a result of the vapor pressure inside as well as a temperature expansion of the front cover. If a press shoe is pressed against the Yankee cylinder to form a press nip, the pressure pressure profile in the transverse direction is no longer constant, but deviates upwards or downwards at the edges. The deviations are not always constant, but depend on the operating parameters, e.g. the basis weight, the speed, the vapor pressure, the temperature, the line force of the press nip and / or the like. As is known, the line force can be calculated from the pressure profile and the nip geometry. There is a clear connection for the same press shoe.

The aim of the invention is to create a possibility for the transverse pressure profile and / or linear force transverse profile resulting in the width of the press nip in the press nip, which is preferably formed by a shoe press Check the press nip, especially at the edges, and set it to the desired values. A corresponding setting should be possible, especially during operation.

This object is achieved according to the invention by a machine for producing a tissue web, with a press nip which is formed between a drying cylinder, in particular a Yankee cylinder, and a press shoe arrangement which can be pressed against the drying cylinder via a plurality of pressing elements which can be pressed into at least one are arranged transversely to the web running direction, with a measuring device for measuring at least the pressing pressures resulting in the two lateral edge areas of the press nip in the effective area associated with pressing elements and with a control and / or regulating device, via which the pressing pressures in the edge areas by a corresponding action of the pressing elements assigned to these edge regions can be set locally.

The pressing elements serving as actuators therefore no longer have to press the pressure shoe arrangement across the width with the same constant, predetermined force, the edge regions can now in particular also be subjected to different pressing forces.

Advantageously, at least the pressing elements assigned to the edge regions can be acted upon or controlled independently of the other pressing elements.

Several contact elements can in particular be assigned to a respective edge area. The pressing elements of a respective edge region can preferably be acted upon or controlled at least partially independently of one another.

In particular, hydraulic pressure elements can be provided. These can each comprise at least one cylinder / piston unit.

According to an expedient practical embodiment, at least the pressure elements provided in the edge areas are assigned separate hydraulic units. However, such an embodiment is also conceivable, for example, in which at least the pressure elements assigned to the edge regions can be acted upon by a central hydraulic system via the throttles specifically assigned to the respective pressure elements.

Advantageously, the pressing pressure cross profile can be adjusted in particular in the edge areas via the pressing elements. This cross-pressure profile is preferably adjustable during operation.

According to a preferred practical embodiment of the invention, a pressure cross profile control is provided.

Advantageously, a respective edge area has a width, measured transversely to the machine direction, of at most about 1000 mm and preferably of at most about 700 mm.

According to a preferred practical embodiment of the machine according to the invention, the pressing pressure measuring points, viewed in the machine running direction, are each provided in the region of the maximum of the pressing pressure curve resulting in the machine running direction.

When viewed in the transverse direction, the contact pressure measuring points are advantageously provided in the area of the contact elements.

In particular, a display device for displaying the measured pressing pressure values can also be provided. Such a display device preferably comprises a plurality of display elements, such as, for example, pressure gauges or the like, assigned to the various pressing pressure measuring points.

The display device can comprise display elements provided in the area of the press and / or display elements provided in the area of a control room or control center.

According to a preferred practical embodiment, the press shoe arrangement is provided in the area of the press pressure measuring points with measuring bores through which the respective press pressures resulting in the press nip are measured.

Advantageously, three pressing elements are provided in the edge areas. In principle, however, more or fewer pressing elements can also be provided in the respective edge regions.

Advantageously, the pressure elements provided in the edge areas can be acted upon or controlled independently of one another and independently of the pressure elements provided in the central area.

It is also advantageous if the setting of the pressures, at least in the marginal areas, takes place at least in part on the basis of absolute target values.

In principle, however, such an embodiment is also conceivable in which the setting of the pressing pressures takes place at least partially in the marginal areas on the basis of relative target values.

According to an expedient practical embodiment of the invention, the control and / or regulating device receives a reference pressure value from at least one contact pressure measuring point or at least one contact element in the middle region lying between the two edge regions. The contact pressures or contact pressures in the edge regions can preferably be set as a function of the reference pressure value.

The division of the pressing elements in the edge regions in the transverse direction can be at least substantially the same as the division of the pressing elements in the middle region lying between the two edge regions or differ from the division of the pressing elements of this middle region. In the latter case, the division of the pressing elements in the edge regions is preferably smaller than the division of the pressing elements in the middle region.

The pressing pressures are preferably adjustable via the control and / or regulating device in such a way that an at least substantially uniform pressing pressure cross profile results.

It is also particularly advantageous if the press shoe arrangement has a lower bending stiffness in the edge regions than in the central region lying between the two edge regions.

The press shoe arrangement can comprise only a single press press or a plurality of press shoes.

The pressing elements serving as actuators for pressing the shoe no longer have to act with the same constant force. Rather, the edge areas can now also be subjected to different contact forces. The e.g. Hydraulic pressure elements or units can be subjected to different pressures in the edge areas regardless of the pressure elements provided in the middle. For this purpose, separate hydraulic units can be assigned to the edge areas, or they can be operated via a central hydraulic system together with the remaining pressure elements with suitable throttles. The edge regions are, for example, at most about 1000 mm wide and in particular at most about 700 mm wide.

In the edge areas, the pressures, preferably the maximum pressures, can be measured, for example, through bores provided in the press shoes. In the machine direction these measuring bores are preferably positioned in the area in which the pressing pressure curve resulting in the machine direction has its maximum. The measured pressures can be displayed, for example, on manometers on the press or in the control room. In the transverse direction, the measuring bores can be arranged in particular in the area of the preferably hydraulic pressing elements. The machine personnel can now set the desired contact pressure at the relevant point by appropriately setting the contact pressure of a respective contact element in the edge area. Problems such as felt compaction, web overheating, web transfer to the next machine section and web adhesion conditions on the Yankee cylinder are avoided. Correspondingly, the quality characteristics of the tissue web, such as, in particular, the dry content, Bulk, crepe quality etc. can also be optimally set in the critical marginal areas.

In particular, a press shoe arrangement with pressure measuring devices for measuring the press pressure at representative points in the area of the preferably hydraulic pressing elements in the edge area of a tissue machine can be provided. The measured pressures can be compared to predetermined target values and adjusted to these target values by appropriately adjusting the local shoe contact forces.

The invention has a particularly advantageous effect on Yankee cylinders which have inner ribs to stiffen the cylinder jacket, as is the case, for example, is described in DE-A-196 54 345.

Figur 1

eine schematische, perspektivische Teildarstellung einer Pressschuhanordnung insbesondere zur Bildung eines Pressspaltes mit einem Trockenzylinder wie insbesondere einem Yankee-Zylinder,

Figur 2

eine schematische Längsschnittdarstellung einer einen Yankee-Zylinder mit zugeordneter Pressschuhanordnung umfassenden Schuhpresse im nicht belasteten Zustand,

Figur 3

eine schematische Längsschnittdarstellung der einen Yankee-Zylinder mit zugeordneter Pressschuhanordnung umfassenden Schuhpresse im Betriebszustand (Dampfdruck, Temperatur, Pressdruck),

Figur 4

eine schematische Längsschnittdarstellung der einen Yankee-Zylinder mit zugeordneter Pressschuhanordnung umfassenden Schuhpresse mit zugeordneter Steuer- und/oder Regeleinrichtung und

Figur 5

ein Diagramm, in dem ein beispielhafter Verlauf der sich in den Anpresselementen ergebenden Drücke wiedergegeben ist.

The invention is described below with reference to exemplary embodiments with reference to the drawings; in this show:

Figure 1

2 shows a schematic, perspective partial representation of a press shoe arrangement, in particular for forming a press nip with a drying cylinder, such as in particular a Yankee cylinder,

Figure 2

1 shows a schematic longitudinal sectional illustration of a shoe press comprising a Yankee cylinder with an associated press shoe arrangement in the unloaded state,

Figure 3

is a schematic longitudinal sectional view of a Yankee cylinder with associated press shoe assembly Shoe press in operating condition (steam pressure, temperature, pressing pressure),

Figure 4

is a schematic longitudinal sectional view of the Yankee cylinder with an associated press shoe arrangement comprising shoe press with an associated control and / or regulating device and

Figure 5

a diagram in which an exemplary course of the pressures resulting in the pressing elements is shown.

FIG. 1 shows a schematic, perspective partial illustration of a press shoe arrangement 10, which can be provided in particular for a press nip 14 in a tissue machine with a drying cylinder 12, in particular a so-called Yankee cylinder (see also FIGS. 2 to 4) to build. The press shoe arrangement 10 can comprise one or more press shoes.

The press shoe arrangement 10 can be pressed against the drying cylinder via a plurality of pressing elements 16. These pressing elements 16 can be hydraulic pressing elements, for example, which can each comprise at least one cylinder / piston unit.

As can be seen from FIG. 1, the pressing elements 16 are arranged in a row extending transversely to the web running direction L. In principle, several such rows of pressing elements can also be provided.

A measuring device 18 is provided for measuring at least the pressing pressures resulting in the two lateral edge areas of the press nip in the effective area associated with pressing elements 16.

In the upper part of FIG. 1, the pressing pressure curve 20 resulting in the machine running direction L is shown. The area under this curve corresponds to the line force, for example in kN / m. As can be seen from FIG. 1, the pressing elements 16, viewed in the machine running direction L, can each be provided in the area of the maximum of the pressing pressure curve 20. The pressing pressure can be specified, for example, in kN / m ² or Pa.

The press shoe arrangement 10 is provided in the area of the press pressure measuring points with measuring bores 24, via which the respective press pressures resulting in the press nip are measured. The pressing pressure measuring points 24 defined by the measuring bores 24 are again provided in the machine running direction L in the region of the maximum of the pressing pressure curve 20. Viewed in the transverse direction, these contact pressure measuring points 22 are provided in the region of the contact elements 16.

As can be seen from FIG. 1, a display device 26 is provided for displaying the measured pressing pressure values. This display device 26 can comprise a plurality of display elements 26 ′ assigned to the various pressing pressure measuring points 22, such as in particular pressure gauges or the like.

The display device 26 can comprise display elements 26 'provided in the area of the press and / or display elements 26' provided in the area of a control room or control center.

In the present case, one contact pressure measuring point 22 is provided for each contact element 16.

The pressure elements 16 provided in the edge areas can expediently be acted upon or controlled independently of one another and independently of the middle pressure elements 16.

A plurality of pressing elements 16 can be assigned to a respective edge area. In the exemplary embodiments shown in FIGS. 3 and 4, the two lateral edge regions are each assigned, for example, three pressing elements 16 ₁ - 16 ₃ or 16 ₄ - 16 ₆ .

The pressing pressures in the edge regions can be set locally, for example, via a control and / or regulating device 28 (cf. also FIG. 4) by appropriately acting on the pressure elements 16 ₁ - 16 ₃ or 16 ₄ - 16 ₆ assigned to these edge regions.

The pressing pressure transverse profile can preferably be set in the desired manner, in particular in the edge regions, via the pressing elements 16. The setting can in particular also be carried out during operation. In particular, a pressure cross profile control can be provided.

FIG. 2 shows a schematic longitudinal sectional illustration of a shoe press 30 comprising a drying cylinder 12, in particular a Yankee cylinder, with an associated press shoe arrangement 10 in the unloaded state. The jacket 32 of the drying cylinder is therefore not bent in the present case.

The press shoe arrangement 10 is pressed against the drying cylinder 12 by at least one row of pressing elements 16. The press shoe arrangement 10 forms with the drying cylinder 12 the press nip 14 through which the tissue web is guided together with at least one carrier tape (not shown). The tissue web preferably runs through this press nip or nip 14 together with a water-impermeable press jacket and a felt (water-absorbing).

Figure 3 shows a representation of the shoe press 30 comparable to that of Figure 2 in the loaded condition, i.e. in the operating state. In the operating state, the contour of the Yankee cylinder deforms due to the internal cylinder pressure (steam) and a greater expansion of the end caps of the Yankee cylinder due to the steam temperature and other design-related factors. Furthermore, the contour of the Yankee cylinder is influenced in particular in the area of the press nip by different press pressures or line forces. The jacket 32 of the drying cylinder 12 is therefore bent here. As can be seen from FIG. 3, a corresponding deflection also results in the press shoe arrangement 10.

In the present case, three pressing elements 16 are assigned to each of the two lateral edge regions of the press shoe arrangement 10, namely the press elements 16 ₁ - 16 ₃ and 16 ₄ - 16 ₆ . The pressing elements assigned to the central area are designated here by 16 _z .

The hydraulic pressure elements 16 _i , in particular, can be subjected to different pressures, which correspondingly generate different pressure forces. The pressure elements can in particular be acted upon and / or controlled in such a way that there is an at least substantially uniform pressing pressure cross profile or line force profile in the press nip 14.

FIG. 4 shows a schematic longitudinal sectional view of the shoe press 30 comprising a drying cylinder 12, in particular a Yankee cylinder, with an associated press shoe arrangement 10 with an associated control and / or regulating device 28, by means of which the pressures in the edge areas are appropriately acted upon by the pressure elements 16 ₁ - assigned to these edge areas. 16 ₃ or 16 ₄ - 16 _{6 can} be set locally.

At least the pressure elements 16 ₁ -16 ₃ or 16 ₄ - 16 ₆ assigned to the edge regions can be assigned, for example, separate hydraulic units. The pressing elements 16 can, however, also be acted upon by a central hydraulic system above the respective throttles assigned to throttles.

As can be seen from FIG. 4, the pressure cross profile can now be set or controlled and / or regulated in the desired manner via the control and / or regulating device 28 and the pressing elements 16, in particular in the edge regions. In the present case too, three pressing elements 16 ₁ - 16 ₃ or 16 ₄ - 16 _{6 are again} provided in each of the two lateral edge regions. In principle, however, more or fewer pressing elements 16 can also be provided in a respective edge area. Four or more pressure measuring points are particularly advantageous with larger pressure gradients, ie with strong local deformation of the Yankee cylinder. This may also require a narrower division for the pressing elements and measuring points, for example less than or equal to 170 mm.

A respective edge area can have, for example, a width measured transversely to the machine running direction, in particular of at most about 1000 mm and preferably of at most about 700 mm.

The control and / or regulating device 28 can be assigned an input device 34 for entering setpoint values of the controlled pressing elements. The pressures can be set at least partially in the marginal areas on the basis of absolute setpoints and / or on the basis of relative setpoints.

In the present case, the control and / or regulating device 28 receives a reference pressure value 36 from at least one contact pressure measuring point 22 (cf. for example also FIG. 1) or at least one contact element 16 in the middle region lying between the two edge regions. The contact pressures or contact pressures in the border areas can therefore be set depending on the reference pressure value. The reference pressure value can in particular be a pressure value in the press nip 14 measured at a respective pressing pressure measuring point 22 or a pressure measured in the associated pressing element 16. Via the control and / or regulating device 28, the pressing elements 16 ₁ - 16 ₃ or 16 ₄ - 16 ₆ assigned to the two edge regions are then acted upon accordingly.

The transverse division T _{R of} the pressing elements 16 in the edge zones can be at least substantially the same as the division T _{M of} the pressing elements 16 in the central region lying between the two edge regions or differ from this division T _{M of} the central pressing elements 16. In the latter case, the pitch T _{R of} the pressing elements 16 in the edge regions is preferably smaller than the pitch T _{M of} the middle pressing elements 16.

In the present case too, the pressing elements 16 can thus be subjected to different pressures again.

The pressing pressures can in particular be adjustable or controllable and / or regulatable via the control and / or regulating device 28 in such a way that an at least substantially uniform pressing pressure cross profile or line pressure cross profile results.

The press shoe arrangement 10 can have a lower bending stiffness in the edge regions than in the middle region lying between the two edge regions.

FIG. 5 shows a diagram in which an exemplary course of the pressures resulting in the pressing elements 16 _i is shown. The reference pressure is given with p _z .

$${\text{P}}_{\text{5}}{\text{= P}}_{\text{2}}{\text{= 40 · 10}}^{\text{5}}\text{Pa}$$

$${\text{P}}_{\text{4}}{\text{= P}}_{\text{3}}{\text{= P}}_{\text{z}}{\text{= 27 · 10}}^{\text{5}}\text{Pa}$$

For example, the following pressures may be present, p _i denoting the pressure in the pressing element 16 _i : $${\text{P}}_{\text{6}}{\text{= P}}_{\text{1}}{\text{= 8.10}}^{\text{5}}\text{Pa}$$

$${\text{P}}_{\text{5}}{\text{= P}}_{\text{2}}{\text{= 40.10}}^{\text{5}}\text{Pa}$$

$${\text{P}}_{\text{4}}{\text{= P}}_{\text{3}}{\text{= P}}_{\text{z}}{\text{= 27.10}}^{\text{5}}\text{Pa}$$

Such a characteristic pressure curve according to the invention at the edges achieves a uniform, optimal pressing pressure cross profile, so that the paper or tissue web produced has a desired, uniform moisture cross profile. One advantage is the longer felt runtimes, since the felt in the press nip is no longer compacted or compressed differently.

LIST OF REFERENCE NUMBERS

10

Press shoe arrangement

12

Drying cylinders, Yankee cylinders

14

press nip

16

presser

18

measuring device

20

Press pressure curve

22

Press pressure measuring point

24

measuring bore

26

display

26 '

display element

28

Control and / or regulating device

30

shoe press

32

coat

34

input device

36

reference pressure

L

Web direction

T _M

Division of the middle pressing elements

T _R

Division of the pressure elements in the edge area

Claims (31)

Machine for producing a tissue web, with a press nip (14) which is formed between a drying cylinder (12), in particular a Yankee cylinder, and a press shoe arrangement (10) which can be pressed against the drying cylinder by means of a plurality of pressing elements (16) at least one row extending transversely to the web running direction (L) is arranged, with a measuring device (18) for measuring at least the pressing pressures resulting in the two lateral edge areas of the press nip (14) associated with pressing elements (16) and with a control and / or Control device (28) by means of which the pressing pressures in the edge regions can be set locally by appropriately acting on the pressing elements (16) assigned to these edge regions. Machine according to claim 1,
characterized,
that at least the pressure elements (16) assigned to the edge regions can be acted upon or controlled independently of the other pressure elements (16). Machine according to claim 1 or 2,
characterized,
that a respective edge area has several pressing elements (16) assigned and these pressing elements (16) can be acted upon or controlled at least partially independently of one another. Machine according to one of the preceding claims,
characterized,
that hydraulic pressure elements (16) are provided. Machine according to claim 4,
characterized,
that the hydraulic pressure elements (16) each comprise at least one cylinder / piston unit. Machine according to one of the preceding claims,
characterized,
that hydraulic pressure elements (16) are provided and at least the hydraulic elements assigned to the edge areas (16) are assigned separate hydraulic units. Machine according to one of the preceding claims,
characterized,
that hydraulic pressure elements (16) are provided and at least the pressure elements (16) assigned to the edge areas can be acted upon by a central hydraulic system via the respective pressure elements (16) that are assigned to specific throttles. Machine according to one of the preceding claims,
characterized,
that the pressure cross profile can be adjusted in particular in the edge areas via the pressure elements (16). Machine according to claim 8,
characterized,
that the baling cross profile is adjustable during operation. Machine according to claim 8 or 9,
characterized,
that a pressure cross profile control is provided. Machine according to one of the preceding claims,
characterized,
that a respective edge area has a width, measured transversely to the machine direction (L), of at most about 1000 mm and preferably of at most about 700 mm. Machine according to one of the preceding claims,
characterized,
that the pressing pressure measuring points (22) viewed in the machine direction (L) are each provided in the area of the maximum of the pressing pressure curve (20) resulting in the machine direction (L). Machine according to one of the preceding claims,
characterized,
that the pressing pressure measuring points (22), viewed in the transverse direction, are provided in the area of the pressing elements (16). Machine according to one of the preceding claims,
characterized,
that a display device (26) is provided for displaying the measured pressing pressure values. Machine according to claim 14,
characterized,
that the display device (26) comprises a plurality of display elements (26 ') associated with the various pressing pressure measuring points (24), such as in particular pressure gauges or the like. Machine according to one of the preceding claims,
characterized,
that the display device (26) comprises display elements (26 ') provided in the area of the press. Machine according to one of the preceding claims,
characterized,
that the display device (26) comprises display elements (26 ') provided in the area of a control room or control center. Machine according to one of the preceding claims,
characterized,
that the press shoe arrangement (10) is provided in the area of the press pressure measuring points (22) with measuring bores (24) through which the respective press pressures resulting in the press nip are measured. Machine according to one of the preceding claims,
characterized,
that three contact elements (16 ₁ - 16 ₃ or 16 ₄ - 16 ₆ ) are provided in the edge areas. Machine according to one of the preceding claims,
characterized,
that the pressure elements (16) provided in the edge areas can be acted upon or controlled independently of one another and independently of the pressure elements (16) provided in the central area. Machine according to one of the preceding claims,
characterized,
that the setting of the pressures, at least in the marginal areas, takes place at least in part on the basis of absolute target values. Machine according to one of the preceding claims,
characterized,
that the setting of the pressures, at least in the marginal areas, takes place at least in part on the basis of relative target values. Machine according to one of the preceding claims,
characterized,
that the control and / or regulating device (28) receives a reference pressure value (36) from at least one pressing pressure measuring point (22) or at least one pressing element (16) in the middle area lying between the two edge areas. Machine according to claim 23,
characterized,
that the contact pressures or contact pressures in the edge areas can be set as a function of the reference pressure value. Machine according to one of the preceding claims,
characterized,
that viewed in the transverse direction, the pitch (T _R ) of the pressing elements (16) in the edge areas is at least substantially the same as the pitch (T _M ) of the pressing elements (16) in the middle area lying between the two edge areas. Machine according to one of claims 1 to 24,
characterized,
that viewed in the transverse direction, the division (T _R ) of the pressing elements (16) in the edge regions differs from the division (T _M ) of the pressing elements (16) in the middle region lying between the two edge regions. Machine according to claim 26,
characterized,
that viewed in the transverse direction, the pitch (T _R ) of the pressing elements (16) in the edge areas is smaller than the pitch (T _M ) of the pressing elements (16) in the middle area lying between the two edge areas. Machine according to one of the preceding claims,
characterized,
that the pressing pressures can be adjusted via the control and / or regulating device (28) in such a way that an at least substantially uniform pressing pressure cross profile results. Machine according to one of the preceding claims,
characterized,
that the press shoe arrangement has a lower bending stiffness in the edge regions than in the middle region lying between the two edge regions. Machine according to one of the preceding claims,
characterized,
that the press shoe arrangement comprises only a single press shoe. Machine according to one of claims 1 to 29,
characterized,
that the press shoe arrangement comprises at least two press shoes.

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