Pressing arrangement

The invention relates to a press arrangement for treating a fibrous web, in particular a paper and / or board web, having an intermediate a shoe press unit and an opposing roll formed, in the web running direction extended press nip between the counter roll and a and a further roller nip formed, wherein the shoe press unit a solid support by a rotational circumferential, in the region of the extended Press nip by at least one support member to the support abgestütztes flexible press belt and the counter roller comprises as a controlled deflection roll with a revolving around a rotationally fixed carrier Roll shell is formed in the region of the extended press nip again supported by at least one support member to the respective support and wherein the preferably pressure-fluid-operated supporting elements designed and acted upon is that with respect to the produced by the supporting elements on the flexible press belt of the Shoe press and the roll shell of the backing roll acting interior Contact pressures, a differential pressure setting.

In such a press arrangement, wherein the shoe press usually located above, should also not sag controlled nip a possible level line force can be generated, which by a corresponding Differential pressure or a corresponding line force difference between the shoe press unit and the backing roll is achieved. The differential pressure causing the extended in the press nip between the Shoe press and the counter roller acting line force not in full balanced scope through the inner support elements of the counter-roller becomes. The remaining force causes deformation of the mating roll both formed with the shoe press nip extended, the be easily compensated by the flexible support member of the shoe press may, as well as between the counter roll and the other roll nip formed. If the differential pressure chosen, for example, that adjusts the shoe press, a greater contact pressure than in the counter-roller, as occurs in between the backing roll and the further Roller nip formed a bulge to the counter roll. by virtue of this bulge can, for example, the counter roll and the further roll with a smaller crown for the controlled deflection be executed. With such a lower crown can the differential speeds between the roll center and the Roll ends are kept small. Between the shoe press and the counter roll can thus in particular such a line force difference are generated, with the deflection of the counter roll in the nip causes, thereby reducing the required crown is made possible in this nip.

In a press arrangement known from DE-A-195 20 443.3 of the the aforementioned type is the differential pressure and the line force difference fixed at a constant value. A fixed set differential pressure brings But just as a lack of differential pressure the Disadvantage that the line force at best a very limited can be adjusted range. This is particularly due to the fact that is dependent on the line force deformations by fixedly disposed cambers not be properly compensated and thus the self-adjusting to variations across the web width Pressure profile result.

A known central roll an additional support element rows, which provided towards the preceding roll towards the roll gap is and the anti-deflection controls in this nip. Ei ne such additional support element rows is now but with considerable connected additional effort and correspondingly expensive.

The aim of the invention is a simple in construction held inexpensive to provide press assembly of the aforementioned type, in which the Line force in the nip in a relatively wide range and adjustable which is in this nip transversely resultant to the web running direction is Preßdruckprofil varied without it to an additional support element rows the counter roll requires.

This object is achieved according to the invention characterized in that the differential pressure is changeable. In this case, the differential pressure is preferably Also, the line force between the shoe press unit difference and the backing roll changeable.

The variably adjustable differential pressure between the Shoe press unit and the backing roll in particular, the deformation variable in the nip between the counter roll and the other roll to be influenced. This means that in this not sag controlled otherwise Nip line forces over a wide range adjustable, always being guaranteed an optimal Preßdruckquerprofil is. Another advantage of the variable variable differential pressure between the shoe press unit and the backing roll is that with a targeted adjustment of the differential pressure cross profile corrections formed between the counter roller and the further roller nip can be made. In conclusion, therefore is also the moisture profile adjustable by the press in the desired manner. with a Change in the differential pressure and the line pressure difference between the shoe press unit and the backing roll also changes the deflection the counter-roller in the roller nip, and thus the resultant therein Pressure distribution. Here, the pressure distribution changes only in the nip. A deflection change of the backing roll in the extended nip is offset by the flexible press shoe. It is possible, acting on the fibrous web line forces in at least one nip unchanged in the respective set to keep the desired value. Even with a change in the line forces in the adjacent press gaps is always an optimal level line force in the formed between the counter roll and the other roll Nip distance. In this nip also are corrections the line force to improve the moisture profile in the form of Border refunds or charges possible. Moreover, the exchange is of the backing roll the nip forming roller further by another roll with a different stiffness simplified, with different Stiffness, for example, the material, the wall thickness or, in the case of a suction roll, may be due to the drilling pattern. Moreover, there is also an easier adaptation to a different Amount of deformation in the roll gap, for example, by a modified vacuum may be caused in the other roller. there , the date any necessary Bombierungsänderung the counter roll and the other roller by a corresponding change in the circumvented pressure difference between the shoe press unit and the backing roll will.

It is particularly advantageous when the differential pressure and the line force difference is at least regionally continuously variable.

To vary the differential pressure, for example, by the Support elements of the shoe press unit generated, on the flexible press belt acting internal contact pressure or, for example by the supporting elements of the counter roll produced on the roll periphery acting internal contact pressure be changeable. In principle it is, however, also possible to vary the differential pressure, both by the support elements of the shoe press unit generated, on the flexible Press belt acting inner contact pressure and the by the supporting elements the counter roll produced on the roll periphery acting interior is contact pressure changeable.

In an expedient practical embodiment of the invention Press arrangement, the supporting elements of the shoe press and the supporting elements of the opposing roll to a common pressurized fluid line connected, wherein the pressure in the fluid communication between common pressure fluid line and the one or more support elements of Shoe press unit and / or the pressure in the fluid communication between common pressure fluid line and the one or more support elements of Counter roll adjustable pressure reducing means are provided and Differential pressure across this variable pressure reducing means is changeable.

The supporting elements of the shoe press unit and / or the supporting elements of the Counter roll can be used individually, in groups or as a whole to the common Pressure fluid line to be connected. To reduce the pressure of groups connected to the common pressurized fluid line Supporting elements can be between at least one, preferably each of these Groups of supporting elements and the common pressurized fluid line a be provided adjustable pressure reduction. To reduce the Pressure individually enclosed to the common pressurized fluid line Supporting elements can be between at least one, preferably each of these individual supporting elements and the common pressurized fluid line a be provided adjustable pressure reduction.

In an expedient practical embodiment, the Pressure reduction means at least one variably adjustable valve.

In most cases, it is advantageous when the differential pressure and the line force difference can be set externally.

The differential pressure and the line force difference can, for example, mechanically, hydraulic, pneumatic, manual, remote controlled, locally, starting from a waiting and / or process performed adjustable.

In an expedient embodiment of the differential pressure is by means predeterminable characteristics as a function of the line force in the nip adjustable. The differential pressure can also vary depending on line force adjustment presets be adjustable for the nip, wherein the Line force adjustment presets preferably via an electronic control entered and / or via corresponding signals from a process control system to be provided. The differential pressure may in particular also an at least one closed loop comprehensive control system be adjustable.

In an expedient practical embodiment is via the differential pressure the line force in a further variable nip is formed between the further roll and an additional roll. at the additional roll may, for example, a suction roll act.

Expediently, at least the opposing roll and / or associated with this the nip forming roller further cambered. Such crown due to the variable differential pressure or of the variable Line force differential less than previously be common. In particular Applications can even be completely dispensed in such a crown will.

In a preferred embodiment of the press assembly according to the invention the shoe press by a shoe press with a flexible press formed as a press belt.

The shoe press unit is expediently above the backing roll arranged.

In a preferred practical embodiment of the roll mantle of the backing roll at its ends is not radially displaceable on the relevant mounted carrier.

In certain cases it may be expedient if the action level the at least one supporting element of the opposing roll to the action plane the at least one support member of the shoe press is slightly inclined. In principle, however, it is also possible that the Effect level of the at least one supporting element of the backing roll with the effect level of the at least one support member of the shoe press coincide at least substantially.

In an expedient practical embodiment, the pressure-effective Surfaces of the supporting elements of the opposing roll, unlike the pressure-effective surfaces of the at least one supporting element of Shoe press. A similar effect as that of the plane of action the extended press nip inclined supporting elements of the counter roll can are therefore in particular also achieved in that the pressure-effective Surfaces of these support elements unequal to the surfaces of the support elements the shoe press are. Due to the different internal will print areas when connected to a common rail already reaches a differential line force between the two rollers. additionally can now in one or both leads variable pressure reduction be used to achieve the advantages mentioned above.

In the subclaims, further advantageous embodiments of the Press arrangement according to the invention indicated.

The invention will in the following by means of embodiments under Referring to the drawing approaches explained; in which:<dl tsize="8"><dt>figure 1</dt><dd>a schematic cross-sectional representation of an embodiment a press assembly having three press rolls,</dd><dt>figure 2</dt><dd>is a schematic longitudinal sectional view of the in figure 1 embodiment, in which also the to the shown support elements guided pressure fluid connections are and</dd><dt>figure 3</dt><dd>a schematic cross-sectional view of another Embodiment of a press arrangement with four Press rolls.</dd></dl>

In Figures 1 and 2 is a purely schematic illustration of a first Embodiment of the treatment of a fibrous web such as in particular 10 a paper and / or board web serving press assembly shown.

This press assembly includes a between a shoe press, here a shoe press roll 12 and a counter roll 14 formed in Web running direction L extended nip 16 and between the Backing roll 14 and a further roll, here a suction roll 18, formed Nip 20th

The directly above the backing roll 14 arranged shoe press 12 having a rotationally fixed by a support 22 rotating, in the region of extended press nip 16 by a support member 24 on the carrier 22 supported, serving as a pressing belt flexible press 26th

The counter roll 14 is in the present case as a controlled deflection roll educated. It has a revolving around a rotationally fixed carrier 28 Roll mantle 30, which in the region of the extended press nip 16 by a transversely to the web running direction L extending row of Supporting elements 32 is supported on the respective support 28th As can can be seen the figure 1, the suction roller 18 is obliquely below the counter roll 14 is arranged. The rollers 12, 14 and 18 are in a mounted framing not shown. By nips 16 and 20 extend next to the fibrous web 10 dewatering felts 34 for receiving of pressed out of the fibrous web 10 water.

The hydraulic, in the form of an axially extending strip on the backing 22 mounted supporting element 24 of the shoe press 12 is in the present Case provided with a concave support surface 36th Instead of on a hydraulic pressure cushion mounted bar is especially the Using multiple support elements 24 possible. The lubrication of the Gap between the supporting surface 36 and the inner surface of the flexible Press cover 26 can hydrostatically and / or hydrodynamically done.

Due to the concave support surface 36 is the approximately cylindrical counter roll 14 of the extended in the web running direction L nip 16 formed.

The roller shell 30 of the counter roll 14 is radially at its ends not slidably mounted on the support 28th

In the present case, the effect is level 38 of the support members 32 of the Against roller 14 with respect to the effective plane 40 of the support member 24 slightly the shoe press roll 12 is inclined. In this case, the angle of inclination α is preferably in a range from about 2 ° to about 15 ° and in particular in a range of about 4 ° to about 8 °. In principle it is, however, also possible that the effective plane 38 of the support members 32 of the Backing roll 14 with the plane of action 40 of the support member 24 of Shoe press roll 12 is at least substantially coincident.

Since the roll shell 30 of the backing roll 14 at the ends by bearings 42 is fixed to the support 28, the inclination of the support elements from the effect 32 (see. In particular Figure 1) resulting deformation of the roll mantle 30 of the backing roll 14 particularly strong in the central region out, so that the roll mantle 30 there more to suction 18 side deformed.

In the present embodiment, the support member 24 of the Shoe press roll 12 and the supporting elements 32 of the backing roll 14 to a common pressure fluid line connected 44th taken as the figure 2 may be, the supporting elements 32 of the backing roll 14 are in the present case, in groups with this common pressure fluid line 44..

The pressure fluid operated supporting elements 24 and 32 are acted upon, that with respect to the generated by these supporting elements 24, 32, to the flexible press 26 of the shoe press roll 12 and the roll shell 30 of the backing roll 14 acting internal pressing pressures, a differential pressure adjusts the partially different by size the pressing faces of the support members 24, 32 may be determined. According to this differential pressure variable. This differential pressure In particular, the line force difference between the Shoe press roll 12 and the backing roll 14 changeable. Preferably also extending transversely to the web running direction L resultant cross section of the differential pressure between the shoe press roll 12 and the backing roll 14 variable, so that in particular different differential pressures across the width are adjustable. About the variable differential pressure between the shoe press unit 12 and the counter roll 14 is thus correspondingly Also, the line force in the nip 20 be changed, in which nip 20 at least substantially flat line forces set are. Here, the differential pressure and the line force difference can at least be regionally varied continuously. The differential pressure or the line force difference can be set in the present case from the outside. The setting can, for example, mechanical, hydraulic, pneumatic, manually, remotely, locally, from a waiting and / or carried out process. The differential pressure can, for example, by means of predefinable characteristic curves as a function of the line force in the Nip 20 be adjustable. It may in particular, depending adjustable line force correction specifications for the nip 20 be. In this case, the setting is done via an electronic Control 62. It is in particular also possible that for example the each line force adjustment presets and / or the like via appropriate Signals a process control system are provided. moreover the differential pressure over an at least one closed loop comprehensive control system be adjusted.

In the present embodiment, for varying the differential pressure the produced by the supporting elements 32 of the backing roll 14, on whose roll mantle 30 acting internal contact pressure changed (see. Figure 2). In the present case are in a pressure fluid connection between the common pressurized fluid line 44, and the supporting elements 32 the counter roll 14 adjustable or variable adjustable pressure reducing 46 is provided, wherein the differential pressure across these variable Pressure reduction means 46 is changed. As seen from the figure 2 is, is to reduce the pressure of the groups to the common Pressure fluid line 44 connected support members 32 between each group of support members 32 and the common pressurized fluid line 44 respectively an adjustable or variable adjustable pressure reducing 46 provided. In contrast, the support element 24 of the shoe press roll 12 directly connected to the common pressurized fluid line 44th The pressure reduction means 46 may, for example, a respective variably adjustable valve include.

The variably adjustable differential pressure between the shoe press 12 and the backing roll 14 may also be in the deformation between the counter roller 14 and the suction roll 18 nip formed 20 variable to be influenced. This means that in this not sag controlled otherwise Nip 20 line forces over a wide range adjustable, always guaranteed an optimal Preßdruckquerprofil is. With a targeted adjustment of the variable differential pressure between the shoe press roll 12 and the backing roll 14 can also Transverse profile corrections in between the counter roller 14 and the suction roll 18 formed nip 20 be made.

Because of the present invention variable differential pressure, this Crowning of the rolls are however relatively small. In particular Cases even completely dispensed with such a crown will.

With the arrangement shown in Figure 2 is used in the shoe type press roll 12 a higher contact force generated as in the counter-roller 8. In order to influence the cross section in front of it but can nip 20 also be the reverse case expedient, in which to the roll shell 30 of the backing roll 14 a higher contact pressure is exerted on the the press jacket 26 of the shoe press roll 12. In this case, the Pressure reduction means 46 between the common pressurized fluid line 44 and a desired number of support elements or support member groups the shoe press 12 to use. The reduced pressure must but always still have a value such that between in the Shoe press roll 12 and the backing roll 14 extended press nip formed 16 the desired line force. The nip 20 is now affected in opposite ways. It occurs in this case, namely, an increase in the overall deformation. This can be particularly be in relatively narrow paper machines useful where the purpose of the Bombierungsverringerung in between the counter roller 14 and the further roll 18 nip formed 20 a subordinate role plays.

An even higher degree of variability is achieved when both the Pressure fluid connections to the shoe press roll 12 and into the pressure fluid connections to the backing roll 14 variably adjustable pressure reducing 46 used. The line forces in the nip 20 can then be adjusted to an even greater range of linear forces, wherein always produces a planar Preßkraftquerprofil in the nip 20 can be. Then, for example the adjustment presets border corrections the line force in the nip 20 in the positive direction (Edge over-press) and in the negative direction (border relief) take place.

In the figure 3 is a schematic cross-sectional view of a further Embodiment of a press arrangement with four press rolls shown.

This embodiment differs from that according to Figures 1 and 2 essentially in that viewed in the web running direction L before the nip 20, a further roller nip 48 is provided between the the suction roller 18 and an underlying additional Roller 50 is formed. This additional nip 48 is double-felted, during the next two in the web running direction L nips 20 and 16 are single-felted. The through the further nip 48 guided top felt 52 also runs through the nip 20. The additional Roller 50 is in the loop of the run through the nip 48 under felt 54.. The fibrous web 10 is from the top felt 52 in over the region of a suction roll 56 of a screen belt 58 before it is passed through the nip 48th Incidentally, this embodiment substantially the same structure as that according to the Figures 1 and 2, wherein corresponding parts have the same reference numerals are provided.

Thus, between the shoe press roll 12 and the backing roll 14 again a differential pressure or a line pressure difference created 60 wherein the differential pressure and the line pressure difference 60 again changed and preferably are variable and adjustable. In the present Case is about the variable differential pressure or the variable line pressure difference 60 between the shoe press roll 12 and the backing roll 14 in particular the line force changed in the further nip 48th In this case, the differential pressure or pressure difference this line 60 between the shoe press roll 12 and the backing roll 14 in particular be variable and adjustable. This also changes again the deflection of the central or backing roll 14 in the nip 20 and thus the pressure distribution in the nip 20th It is possible, acting on the fibrous web 10 line forces in the nip 20 and the extended press nip 16 on the keep each desired value. The setting of the line pressure difference 60 and the differential pressure is carried out also in the present embodiment In principle, again via an electronic control 62. the adjustment, for example mechanical, hydraulic, pneumatic, Manually operated, remotely, locally, from a waiting and / or carried out process. Here is a second support element row dispensed in the direction of the nip 20th The variable line force difference may, in particular for influencing the pressure distribution be used in order in the nip 20 without in each case the changed desired line forces in the nips 20, 16 and 48 will. About the variable differential pressure or the variable line pressure difference can also in particular, the line force in the nip 20 adjusted in a relatively wide range in the desired manner will. In addition, a targeted influence on the conditions in the further nip 48 possible.

<b>LIST OF REFERENCE NUMBERS</b>

<dl tsize="3" compact="compact"><dt>10</dt><dd>Fibrous web</dd><dt>12</dt><dd>shoe press</dd><dt>14</dt><dd>backing roll</dd><dt>16</dt><dd>extended nip</dd><dt>18</dt><dd>further roll, suction roll</dd><dt>20</dt><dd>nip</dd><dt>22</dt><dd>rotationally fixed carrier</dd><dt>24</dt><dd>supporting member</dd><dt>26</dt><dd>flexible press jacket</dd><dt>28</dt><dd>rotationally fixed carrier</dd><dt>30</dt><dd>roll shell</dd><dt>32</dt><dd>supporting elements</dd><dt>34</dt><dd>Dewatering</dd><dt>36</dt><dd>supporting surface</dd><dt>38</dt><dd>effect level</dd><dt>40</dt><dd>effect level</dd><dt>42</dt><dd>warehouse</dd><dt>44</dt><dd>common pressure fluid line</dd><dt>46</dt><dd>pressure reduction</dd><dt>48</dt><dd>further roller nip</dd><dt>50</dt><dd>additional roll</dd><dt>52</dt><dd>overfelt</dd><dt>54</dt><dd>bottom felt</dd><dt>56</dt><dd>suction roll</dd><dt>58</dt><dd>screen belt </dd><dt>60</dt><dd>Pressure differential</dd><dt>62</dt><dd>electronic control</dd><dt>L</dt><dd>The web running direction</dd><dt>α</dt><dd>angle of inclination</dd></dl>