EP1643033B1 - Pressing device in a press section of a machine for manufacturing a fibrous web - Google Patents

Abstract

A papermaking assembly has a shoe press drum (10, 20) with a press shoe (11, 21) applied to a second drum (15). The shoe dress drum (10, 20) is enveloped by a mantle (14, 22) extending from the end cover over the press shoe. The press shoe leading edge and/or trailing edge extend over the drum (10, 20) towards the second drum (15) and terminating no more than 5 mm from the drum (10, 20) surface. The press shoe length in contact with the paper, tissue paper or carton is more than 400 mm. The ratio of the shoe press drum diameter to the length of shoe in the direction of rotation is 4.0 or more. The ratio of the second drum (15) to the press shoe length is 3.9 or more.

Description

The invention relates to a press section of a machine for producing a paper, cardboard, tissue or other fibrous web with a pressing device comprising a press shoe comprising a shoe press roll and, with this a press nip forming counter roll, wherein on the shoe press roll a roll shell of end caps on the press shoe is led around.

Such a press section is for example from the EP-A-0 389 675 known.

From the DE 100 22 087 A1 For example, a press section for a paper machine is known, which has two press points, each formed by a press roll cooperating with a shoe press roll. A first upper felt, the paper web coming from a forming wire, an underfelt and a press jacket of a first shoe press roll pass through the first press point. The underfelt continues with the paper web to the second press site. Together with a second top felt and a press jacket of a second press site, the paper web then passes through the second press site. The paper web follows the underfelt further up to a take-off roll, through which it is transferred to a first dryer wire which transfers the paper web to the dryer section.

In known shoe press rolls in the interaction with a counter roll, the problem is that the roll shell, which is guided around the circumference of the shoe press roll by rotating end-side lids around the press shoe inside the shoe press roll, during the rotational movement wears heavily. The main cause of this high wear is that the press shoe against the outer contour of the shoe press roll is set back pretty strong, so that the shell is deformed differently in its edge region in the passage of the press shoe area, since he rigidly on a circular path through the End plate is guided, on the other hand by the Counter roll is pressed into the shoe contour. In the transition region between the sides of the press shoe and the side walls, it is therefore alternately stretched and compressed.

In one embodiment of a pressing device according to the prior art, for example, a shoe press roll 1 (Fig. 1a) with a rotating shell 2 and a fixed press shoe 3 is provided. This forms together with a counter-roller 4 a press nip through which the fibrous web is passed in the direction of an arrow P to withdraw their water. In Fig. 1a, the shoe press roll 1 and the counter roll 4 are shown in the operating position in cross section.

The press shoe 3 is opposite the contour formed by the jacket 2 in the remaining area of the shoe press roll 1 at a position A at its front edge by an amount y _A and at positions designated B, C and D respectively by amounts y _B , y _C and y _{D set back} relative to the circular contour of the shoe press roll 1, ie, the press shoe 3 is set back over its entire length in the web running direction relative to the circular contour formed by the end disks. This leads to a distance s (FIG. 1b) extending in the axial direction of the shoe press roll 1 between the outer lateral edge of the press shoe 3 in the axial direction, ie a shoe landing plane 5, and the inner edge of a rotating side cover of the shoe press roll, ie the front cover plane 6, a bending of the shell 2 according to the bending lines I _A , I _B , I _C and I _D takes place. Corresponding to the fact that the contour of the press shoe 3 recedes toward the center more strongly than the circular shape predetermined by the end covers and denoted by 7 in FIG. 1a, the bending lines I _B and I _{C are} more inclined than the bending lines I _A and I _D , which correspond to the position on the front edge or in the vicinity of the rear end of the press shoe 3 (viewed in the running direction).

Thus, it can be seen that the edge region of the shell of the shoe press roll is deformed to different degrees when passing through the area of the press shoe, since it is rigidly guided on one circular path through the front disk, on the other hand is pushed through the counter roll in the facing this shoe contour. The deformation and the stresses resulting therefrom in the roll shell result in alternating stresses which limit the life of the shell and reduce it especially with increasing paper machine speeds.

It is the object of the invention to improve the known press section in such a way that the wear and the alternating stress of the roll mantle are reduced.

According to the invention this object is achieved in a press section of the aforementioned type in that the lateral distance of the end cover of the shoe press roll of the press shoe in the axial direction in each case at least 300 mm, in particular 330 mm or more.

By this measure, the load of the roll shell due to the deflection or the deformation when passing through the press shoe is reduced, since the strain or stress in the direction of the longitudinal axis of the shoe press roll distributed over a greater length of the roll shell.

Advantageous developments emerge from the subclaims, the description and the drawings.

The press shoe is preferably set back with its front end and / or with its rear end with a closed press nip at most 5 mm in relation to the circular contour of the roll mantle corresponding to the contour of the end cover.

By this measure, the deflection or deformation of the roll shell is greatly reduced. This applies regardless of the length of the press shoe in the machine direction. In a press shoe with a long length, for example, of more than 300 mm, as used for example for the production of wood-free paper, such as cardboard and packaging paper, to produce a broad press nip, so that there is no such strong surface pressure and the volume of Paper is not reduced too much, the invention can be used to advantage. The press section is formed in this case, for example by a tandem Nipcoflex press with two press nips and can also be used at higher operating speeds according to the invention.

It is particularly advantageous if the press shoe at its front and / or rear end is set back by up to 5 mm with respect to the circular contour of the roll shell or projects up to 50 mm beyond the circular contour.

In order to achieve a good dewatering of the fibrous web, the press shoe in the web running direction of the fibrous web has a length of 300 mm or more, in particular of more than 350 mm, in particular of more than 400 mm.

The effect of the length of the press shoe on the deflection or deformation of the roll shell is also reduced by the fact that the largest possible diameter of the shoe press roll and the counterpressure roll are used in relation to the length of the press shoe in the web running direction. The ratio of the diameter of the shoe press roll to the length of the press shoe in the direction of rotation is 4.0 or more, and the ratio of the diameter of the backing roll to the length of the press shoe is 3.9 or more. According to the invention, such a ratio can generally be used in press devices in a machine for producing a fibrous web.

gegeben ist, wobei y₁ (s. Fig. 1a) das Eindrückmaß an der Auflaufstelle (z. B. Abschnitt A in Fig. 2a; hier wird der Mantel der Presswalze zum ersten Mal zwischen dem Pressschuh und der Gegenwalze geklemmt; d. h. die Spannungen können sich nicht mehr durch Verschiebungen abbauen; y₁ ist die kleinste Abweichung.) den Wert des maximalen Überstands oder der Zurücksetzung des Pressschuhs an seinem Einlauf oder an seinem Auslauf gegenüber der Kreiskontur der Schuhpresswalze bezeichnet, wobei y₂ den Wert bezeichnet, um den der Pressschuh in seinem mittleren Bereich gegenüber der Kreiskontur der Schuhpresswalze zurückgesetzt ist (maximales Eindrückmaß) und wobei s den jeweiligen seitlichen Abstand der Stirndeckel von dem Pressschuh in axialer Richtung bezeichnet und dass der Wert (K₃) weniger als 1,07, insbesondere weniger als 1,02, ganz insbesondere weniger als 1,007, beträgt.Advantageously, a pressing device is used, in which the measure of the elongation of the roll shell of the shoe press roll due to the projecting from the lateral surface press shoe (K ₃ ) by the value $${\mathrm{K}}_{}$$$${\mathrm{}}_3=\left(1+{\left({\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="imgf0001.png"\; state="\{\{state\}\}">y</figure-callout>}}_2/\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}\right)}^2\right)/\left(1+{\left({\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="imgf0003.png"\; state="\{\{state\}\}">y</figure-callout>}}_1/\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}\right)}^2\right)$$

where y ₁ (see Fig. 1a) is the crushing dimension at the nib (e.g., section A in Fig. 2a, here the crimp of the press roll is clamped between the press shoe and the backing roll for the first time, ie, the stresses can no longer be reduced by displacements y ₁ is the smallest deviation.) denotes the value of the maximum protrusion or the resetting of the press shoe at its inlet or outlet opposite the circular contour of the shoe press roll, where y ₂ denotes the value by which the Press shoe is set back in its central region relative to the circular contour of the shoe press roll (maximum Eindrehmaß) and where s the respective lateral distance of the end cover of the press shoe in the axial direction and the value (K ₃ ) is less than 1.07, in particular less than 1 , 02, more preferably less than 1.007.

Advantageously, a support strip is used within the shoe press roll in the direction of rotation in front of the press shoe, which preferably extends over the entire width of the shoe press roll.

With a larger shift R in the direction of the interior of the shoe press roll or even when the press shoe protrudes from the cylindrical contour of the shoe press roll, there is a risk that the lubricating film between the shell and the shoe press roll - with unchanged shoe shape - reduced or even squeezed , It is therefore proposed in a further measure provided according to the invention, to support the lubricating effect that measures for forced lubrication in the shoe are performed at the inlet region, for. B. through small holes that are distributed over the width of the press shoe. By this measure, the friction between the press shoe and the roll shell can be significantly reduced.

There are several ways to apply an oil film; one possibility is that the means for application in front of the press shoe, in particular on a arranged in the direction of the press shoe support bar, is arranged.

Preferably, the press shoe on the inlet side is provided with a bead, in which the means, in particular in the form of arranged over the entire width of the press shoe holes, is integrated. The oil lines may preferably end in lubrication pockets or communicate with protrusions in the interior of the press shoe in which the oil collects.

To reduce the friction and to promote the formation of an oil film between the inside of the roll shell and the press shoe, it also serves when the inlet-side contour forms a convergent wedge between the lateral surface of the roll shell and the inlet side, the shell-facing surface of the press shoe. This can be achieved in that the inlet-side wedge is formed by a radius of curvature of the inlet-side bead that reduces in the direction of the lateral surface of the roller shell, so that the For example, shoe inlet surface has two different radii of curvature.

The diameter of the counter roll is preferably at least 0.975 times the diameter of the shoe press roll. This has for example a diameter of 1200 mm. The counter roll in this case has at least a diameter of 1170 mm.

Fig. 2a

einen ersten Querschnitt durch eine erste Schuhpresswalze und eine mit dieser zusammenwirkende erste Gegenwalze,

Fig. 2b

eine zu Fig. 2a zugehörige Darstellung der Dehnung des Walzenmantels in axialer Richtung im Bereich zwischen der Seite des Pressschuhs und der Innenkante des Stirndeckels,

Fig. 3a

einen zweiten Querschnitt durch eine zweite Schuhpresswalze und eine mit dieser zusammenwirkende zweite Gegenwalze,

Fig. 3b

eine zu Fig. 3a zugehörige Darstellung der Dehnung des Walzenmantels entsprechend der Darstellungsweise in Fig. 2b,

Fig. 4 - 6

ausschnittweise perspektivische Schnittdarstellungen durch eine Schuhpresswalze und eine Gegenwalze in der Umgebung der Einlaufseite eines Pressschuhs.

The invention will be explained in more detail in exemplary embodiments with reference to the drawings. Show it:

Fig. 2a

a first cross section through a first shoe press roll and a cooperating with this first counter roll,

Fig. 2b

2 a representation of the expansion of the roll shell in the axial direction in the region between the side of the press shoe and the inner edge of the end cover,

Fig. 3a

a second cross section through a second shoe press roll and a cooperating with this second counter roll,

Fig. 3b

3 a representation of the elongation of the roll mantle according to the representation in FIG. 2b,

Fig. 4-6

Sectional perspective sectional views through a shoe press roll and a counter roll in the vicinity of the inlet side of a press shoe.

In a shoe press roll 10 (FIG. 2 a), a press shoe 11 with an inlet-side bead 12 is arranged in such a way that the bead 12 has a circular contour 13 fictitious in the region of the press shoe 11, the end disks leading to the contour of a roll shell 14 (not shown here) corresponds to the shoe press roll 10 (position A) (this is defined in Fig. 2b as a negative direction y), while the press shoe 11 in its central region (positions B and C) and at its outlet end (position D) with respect to the contour of the roll mantle 14 is reset (positive y values for the positions B, C, D). Here, A is the beginning of the press nip.

Overall, this means that a counter-roller 15 which interacts with the shoe press roll 10 to form the press nip reduces the roll mantle 14 less strongly than the prior art press apparatus 2 (FIG. 1 a) less than in the prior art the counter roll 4 is pressed.

Compared to the prior art, the distance between the centers of the shoe press roll 10 and the backing roll 15 has been increased by an amount R ₁ (ie, the displacement shown in FIG. 2a) in the radial direction R to reduce the shell indentation. By the points designated A, B, C and D, the run of the roll mantle 14 at the press shoe edge of the press shoe 11 is characterized. The illustration shows the deformation of the roll mantle 14 over the region between the side edge 16 of the press shoe 11 and the inner edge 17 of the end disk in the direction of the longitudinal axis of the shoe press roll 10 by amounts y _A , y _B , y _C and y _D, respectively. Overall, in comparison to the deformations shown in the prior art shown in FIG. 1 b, much lower deformations according to the invention exist. At position A, the roll shell has a negative offset (outward), while at positions B, C, and D, it has a positive offset negative deformation (inward) relative to the circular contour of the faceplate.

The shoe press roll 10 is mounted substantially above the counter roll 15. Compared to the vertical their center is usually offset by an amount e relative to the center of the counter-roller 15.

In another shoe press roll 20 (FIG. 3 a), a press shoe 21 projects out of the circular contour 13 at its front end (position A) like the press shoe 11, while the press shoe 21 at its rear end (position D) projects with the position of the circular contour 13 which means that a roll jacket 22 guided over the shoe press roll 20 is no longer stretched at this location.

In Fig. 3b is shown how between the edge 23 of the press shoe 21 and the inner edge 24, an elongation of the roll shell 22 over the existing between the edge 23 and the inner edge 24 distance s, where z _A , z _B , z _C and _d each denote the offset of the press shoe 21 with respect to the circular contour 13. If the distance between the edges 23 and 24 is doubled to the amount of 2 s (at a distance between the edge 23 and an edge 24 '), the stretch of the roll mantle 22 will be distributed twice as long, and therefore will experience only one about half as much stretching or bending. For the purposes of the invention, therefore, the aim is to choose the distance between the edge of the press shoe and the inner edge of the end disk as large as possible.

In order to reduce the surface pressure between the press shoe 11 and the roll shell 14 according to FIG. 2 a (or the roll shell 22 according to FIG. 3 a), the input side bead 12 of the press shoe 11 is provided with a convergent wedge in one embodiment of the invention (FIG. 4) forms between the roll shell 14 and the shoe inlet surface. This prevents the squeezing of the oil film.

For this purpose, the bead radii of curvature R ₂ and R ₁ , which shrink in the direction of the roll shell 14. It is understood that the value of the radius of curvature R _{2 can} also be continuous or via a plurality of intermediate values in the radius of curvature R ₁ . In this way, a convergent inlet gap 25 is formed between the roll shell 14 and the press shoe 11. The friction between the press shoe 11 and the roll shell 14 is reduced by the use of an oil film 26 applied to the roll shell 14.

In a further embodiment (FIG. 5), bores 27 are present inside the input-side bead 12 of the press shoe 11, via which oil or another lubricant is supplied into the region between the press shoe 11 and the roll shell 14 in order to reduce the friction. The holes 27 are arranged distributed over the entire width of the press shoe 11 and communicate with oil pressure lines, which ensure forced lubrication. The bores 27 may optionally terminate in pockets in which reservoirs for the lubricant are formed. The dashed line 14 'shows the circular contour or the course, the roll shell 14 would take without the introduced into the interior of the shoe press roll 10 press shoe 11.

In another embodiment (FIG. 6), alternatively or in addition to the embodiment according to FIG. 5, inside the shoe press roll 10 a support strip 28 is provided which serves to stabilize the roll mantle 14. Such support strips 28 may be distributed within the shoe press roll 10 at several points over the circumference. On the support strips 28 also nozzles for spraying an oil film can be arranged on the inside of the roll shell 14. The support strip can also extend continuously over the entire width of the shoe press roll 10 in the axial direction. The support strip causes a smooth inlet of the oil film between the roll shell 14 and the press shoe 11 is achieved.

In the event that the shoe press roll is arranged below the counter-roller in a pressing device, and oil by means of a spray pipe in the direction of the inlet of the press shoe and / or the support bar are sprayed.

zu erhalten, wobei K₃ das Maß für die maximale Deformationsänderung des Walzenmantels darstellt. Es versteht sich, dass diese Werte auch anhand der Figuren 2a und 3a ermittelt werden können, lediglich aus Gründen der Übersichtlichkeit wurden die Werte y₁ und y₂ dort nicht eingezeichnet.In addition to the above-described extension of the shoe press roll 10 in the axial direction with a uniform press shoe 11 can be used as a further measure to reduce the elongation of the roll shell 14 at a constant shoe length and the diameter of the backing roll 15 increase. For this purpose, as shown in FIG. _{1 a,} recourse is had to the indentation dimensions y ₁ and y _{2 of} the press shoe with respect to the circular contour of the shoe press roll, in order to obtain the equation already introduced at the outset $${\mathrm{K}}_{}$$$${\mathrm{}}_{\mathrm{3}}\mathrm{=}\left(\mathrm{1}\mathrm{+}{\left({\mathrm{<figure-callout\; id="2"\; label="y"\; filenames="imgf0001.png"\; state="\{\{state\}\}">y</figure-callout>}}_{\mathrm{2}}\mathrm{/}\mathrm{<figure-callout\; id="2"\; label="s"\; filenames="imgf0001.png"\; state="\{\{state\}\}">s</figure-callout>}\right)}^{\mathrm{2}}\right)/\mathrm{(}\mathrm{1}\mathrm{+}{\left({\mathrm{<figure-callout\; id="1"\; label="y"\; filenames="imgf0003.png"\; state="\{\{state\}\}">y</figure-callout>}}_1\mathrm{/}\mathrm{s}\right)}^{\mathrm{2}}\mathrm{)}$$

to obtain K _3, the measure of the maximum deformation change of the roll shell. It is understood that these values can also be determined with reference to FIGS. ₂ a and _{3 a} , merely for reasons of clarity, the values y ₁ and y ₂ have not been plotted there.

Claims (13)

1. Press section of a machine for manufacturing a paper, board, tissue or another fibrous web, having a pressing device with a shoe press roll (10, 20) comprising a press shoe (11, 21) and an opposing roll (15) forming a press nip with the former, a roll shell (14, 22) being led around over the press shoe (11, 21) from end covers on the shoe press roll (10, 20), characterized in that the lateral spacing (s) of the end covers of the shoe press roll (10, 20) from the press shoe (11, 21) in the axial direction is in each case at least 300 mm, in particular 330 mm or more.
2. Press section according to Claim 1, characterized in that, when the press nip is closed, the press shoe (11, 21) is set back with its front end and/or with its rear end by at most 5 mm with respect to the circular contour (13) of the roll shell, corresponding to the contour of the end covers.
3. Press section according to Claim 2, characterized in that the press shoe (11, 21) is set back at its front and/or rear end by up to 5 mm with respect to the circular contour (13) of the roll shell or projects beyond the circular contour (13) by up to 50 mm.
4. Press section according to one of Claims 2 and 3, characterized in that the press shoe (11, 21) has a length of 300 mm or more, in particular of more than 350 mm, quite particularly of more than 400 mm, in the web running direction of the fibrous web.
5. Press section, in particular according to one of Claims 2 to 4, characterized in that the ratio of the diameter of the shoe press roll (10, 20) to the length of the press shoe (11, 21) in the direction of rotation is 4.0 or more, and the ratio of the diameter of the opposing roll (15) to the length of the press shoe (11, 21) is 3.9 or more.
6. Press section according to one of Claims 3 to 5, characterized in that the dimension for the lengthening of the roll shell of the shoe press roll (10, 20) as a result of the press shoe (11, 21) projecting out of the circular contour (13) or circumferential surface is given by the value $${\mathrm{K}}_{\mathrm{3}}\mathrm{=}\left(\mathrm{1}\mathrm{+}{\left({\mathrm{y}}_{\mathrm{2}}\mathrm{/}\mathrm{s}\right)}^{\mathrm{2}}\right)/\mathrm{(}\mathrm{1}\mathrm{+}{\left({\mathrm{y}}_1\mathrm{/}\mathrm{s}\right)}^{\mathrm{2}}\mathrm{)}$$

   

   
   where y₁ designates the smallest indentation dimension of the press shoe, in particular the indentation dimension at the run-on point of the press shoe (11, 21) at its entry, with respect to the circular contour of the shoe press roll (10, 20), where y₂ designates the maximum indentation dimension, in particular the indentation dimension by which the press shoe (11, 21) is set back in its central region with respect to the circular contour (13) of the shoe press roll (10, 20), and where s designates the respective lateral spacing of the end covers from the press shoe (11, 21) in the axial direction, and in that the value (K₃) is less than 1.07, in particular less than 1.02, quite particularly less than 1.007.
7. Press section according to one of Claims 2 to 6, characterized in that, before the press shoe (11, 21) in the direction of rotation, the shoe press roll (10, 20) has a supporting bar (28) which preferably extends over the entire width of the shoe press roll (10, 20).
8. Press section according to one of Claims 2 to 7, characterized in that a means for applying oil to the front region of the press shoe (11, 21) is arranged within the shoe press roll (10, 20).
9. Press section according to Claim 8, characterized in that the means is arranged before the press shoe (11, 21), in particular on the supporting bar (28).
10. Press section according to Claim 8, characterized in that the means is integrated into a bead (12) on the entry side of the press shoe (11, 21), in particular in the form of drilled holes (27) arranged over the entire width of the press shoe (11, 21) .
11. Press section according to Claim 10, characterized in that the contour on the inlet side forms a convergent wedge between the circumferential surface of the roll shell (14, 22) and the surface of the press shoe (11, 21) on the inlet side, facing the shell.
12. Press section according to Claim 11, characterized in that the wedge on the inlet side is formed by a radius of curvature (R₁, R₂) of the bead (12) on the inlet side which decreases in the direction of the circumferential surface of the roll shell (14, 22) .
13. Press section according to one of Claims 1 to 12, characterized in that the diameter of the opposing roll (15) is at least 0.975 times the diameter of the shoe press roll (10, 20).

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