DE19821820A1 - Wet stack calender for processing cardboard web - Google Patents

Abstract

The assembly to apply a finish to the surface of a moving web, and especially of cardboard, is a polishing station with at least two polishing rollers forming a press gap between them for the web passing through. A hard roller and a soft roller form a pair of rollers (2-4). An applicator (5), to form a film on the web surface, is directly at least at one of the two rollers in a pair (2-4). A number of roller press gaps (P1-P3) are formed by the paired rollers (2-4), arranged vertically or horizontally on the direction of web (B) travel. The paired rollers (2-4) are arranged with a hard roller and a soft roller, which are in parallel opposite each other, with the hard rollers on one side of the web (B) and the soft rollers on the other side. The paired rollers (2,3) can be offset from each other, without a gap between the pairs, so that they form an additional press gap in the direction of web (B) travel. The applicator can be a jet applicator with a doctor roller with a smooth or ridged surface, or a doctor blade, a sump applicator (5) or a free-stream jet system. It can also be a roller applicator with a transfer roller. The applicator (5) is at the hard roller of the paired rollers. The press gaps (P1-P3), between the paired rollers (2-4) exert an adjustable linear force independent of the roller loading.

Description

The invention relates to a device according to the preamble of Claim 1.

The web is mostly used in the production of paper or cardboard webs smoothed for surface finishing (also known as calendering). It is the goal is to compensate for differences in thickness within the web and a specific one Smoothness to achieve, for example, the later printability of the web improve.

In many machines for the production of cardboard webs, the required smoothness, usually before the coating process, in a so-called "wet stack calender". This is a smoothing unit installed after the dryer section, usually 6 to 8 hard rollers, some of which (often 3) have so-called water scrapers are attached. These water scrapers are designed as gutters with a seal against the Roll surface formed and z. B. with a mixture of water and starch, Filled with polyvinyl alcohol or other liquids. The liquid level of this Water scraper is so high that it lies over the seal and the liquid with it comes into contact with the roller surface. This will make her with the latter taken and transported to the next press nip above. There it moistens the web surface to improve the smoothing effect and at the same time bind the fibers into the surface of the cardboard web.

Such a wet stack has considerable inadequacies.  

This is expressed in the following:

• - The applied film thickness can only be very imprecise, e.g. B. by changing the Height of the liquid level or by the viscosity of the application medium to be influenced.
• - If torn off, the material web can adhere to the roller surface of the betting stack remain and lead to the "wrapping" of one or more rollers.
• - The device is susceptible to faults and requires a lot of maintenance.
• - Due to the risk of corrosion, roller alloys must be used Disadvantages, e.g. B. in terms of tool life.
• - As a result of the arrangement of all the rollers one above the other, they are in the individual columns acting line forces partly dependent on the roll weight and cannot always be chosen as it is for the smoothing process with regard to smoothness development and minimizing the loss of bending stiffness of the web would be desirable.
• - Because the material web during the run through the wet-stack smoothing unit is always mutually curved, bending rigidity is lost.

A proposal to replace such a wet stack is in DE-297 10 804 U1 disclosed. It is provided that a pair of calenders rollers for calendering a cardboard web in the machine direction immediately before the calender gap Film press is connected upstream. A liquid is applied to the surface in the film press nip transferred to the cardboard web and thereby moistens the cardboard web, causing the Smoothing effect is improved.  

Hard rolls (hard press nip) are provided as calender rolls.

Due to the hard calender gap, the cardboard web is still too strong claimed, and you need an increased space for arranging the Film press.

The present invention has for its object with a suitable Device a minimal stress on the material web, in particular Cardboard web to ensure when smoothing or calendering and also the To improve smoothing effect.

This object is achieved according to the invention in a device of the type mentioned Art solved by the features of the characterizing part of claim 1.

The web combination becomes hard / soft (at least on one side) less stressed than before. Due to the soft press nip (nips) too the smoothing effect better, since there is friction and the press nip is extended.

A particular advantage of the invention is that the medium to be applied can be applied directly to the smoothing roller, which makes the liquid even closer than that of the DE 297 10 804 is applied before the smoothing gap. This will make it even shorter Contact time reached, which means that the application medium does not penetrate deeper than necessary into the web can penetrate. As a result, the dry material web is not moistened and inside can also occur during the passage through the subsequent press nip (s) not undesirably reduce in their thickness and their bending stiffness.

This positive effect is further enhanced when the line forces of the smoothing roller pairs according to the required effect regardless of the roll load in the individual smoothing slits are adjustable, especially since the line forces due to Dead weight of the rollers are often higher than desired. An unnecessary compression the web and the reduction in bending stiffness mentioned above so avoided.  

Above all, however, a very precise metering of the application medium is possible in order to achieve the To be able to reliably control the smoothing effect and to avoid being too large Apply amounts that have to be dried later.

The best smoothing effect is achieved when the application medium is applied to one or more the hard rollers is applied.

Further expedient refinements of the device according to the invention are shown in further subclaims are described.

By providing several pairs of smoothing rollers, the smoothing effect becomes significant improved, but it should be mentioned that a smoothing effect with only one only pair of smoothing rollers is already accessible. Through the arrangement according to the invention The pairs of rollers to each other ensure that the web is as little as possible and is used as evenly as possible.

Above all, the straight guidance of the web through the individual pairs of smoothing rollers protects the Track before loss of bending stiffness.

As application devices for moistening, sizing or pigmenting the web are all conventional known devices such as nozzle applicators with dosing elements in the form of doctor blades, such as roller doctor blades with a smooth or profiled surface or Doctor blades, free jet applicators or roller applicators with downstream metering devices as mentioned above, can be used.

By arranging them directly on the smoothing roller, the required space is required further decreased. The space requirement and the cost of an additional film press are saved here.

The invention will be explained in more detail below with reference to drawings.  

Show it:

Fig. 1 shows a schematic representation of the device according to the invention with pairs of smoothing rollers arranged one above the other at a distance.

Fig. 2 Same as Fig. 1 - with horizontally arranged pairs of smoothing rollers.

Fig. 3 Staggered pairs of smoothing rollers spaced from each other.

Fig. 4 to 6 Further variants of Fig. 3 with offset pairs of smoothing rollers.

Fig. 4 A conventional wet-stack smoothing unit with metering application.

In the figures, the same components are provided with the same reference symbols.

From FIG. 1, an arrangement can be removed, where a web of material B made of cardboard from a not shown in the figure, the dryer section is coming passed in the arrow direction via deflecting rollers 1 through the press nip P1 to P3 of three superposed spaced Glättwalzenpaare 2, 3, 4.

Each pair of rollers consists of a hard and a soft roller, in which Figure was chosen an example in which all hard rollers on one side of the web and all soft rollers are arranged on the other side of the web.

The soft rollers are provided with an inner circle in the figure.

The hard rollers can be heated.

A conventional application device 5 for the purpose of a precisely adjustable and reproducible amount of application medium is arranged on the first lower hard roller of the pair of smoothing rollers 2 .

With this dosed order quantity, controlled leveling or incorporation of the Cardboard web fibers possible.

In the example, a device with a sump and a roller squeegee 6 delimiting the sump is selected as the metering element.

An arrangement of the smoothing roller pairs 2 , 3 , 4 in the horizontal direction is shown in FIG. 2.

Here, the arrangement of the individual smoothing rollers is made so that a hard one Roller is opposed to a soft roller.

An application device 7 is again assigned to the hard roller of the first pair of smoothing rollers 2 . In this case, the application device 7 represents, for example, a free-jet nozzle applicator with a downstream doctor blade 8 with adjustable contact pressure. An application device 5 is assigned to the hard roller of the subsequent pair of smoothing rollers 3 . Here again a sump applicator with roller doctor 6 is used.

But there could also be another available order facility with Dosing options can be used.

A further embodiment variant can be seen from FIG. 3, in which only two pairs of smoothing rollers 2 and 3 are provided.

These pairs 2 and 3 are offset and spaced from one another so that the web passes through the press nips P ₁ , P ₂ and an additional press nip Pz in a meandering manner - but only with a slight curvature. The additional press nip Pz is created in the present case by the two hard rolls lying one above the other.

With an equally possible reversed arrangement of the rollers acc. Fig. 4 form two soft rolls a gap S, which is not a press nip here. In this variant, the upper surface is once again smoothed B _o and the underside B _u in the press nip P in the press nip P _{2. 1}

A further variant in which the underside of the web B _{u is} smoothed 3 times is shown in FIG. 5 and in which the top of the web B _{o is} smoothed 3 times in the press nip (P ₁ , P ₂ , Pz), FIG. 6 .

For reasons of simplification, no application device is shown in FIGS. 4-6. These figures are only intended to illustrate the differently selectable configurations.

In order to demonstrate the possibility of variation for the application devices to be used, sump application devices 5 and an application device 9 with a so-called transfer roller 10 are again shown in FIG. 3. The transfer roller 10 can have a special cover with a surface structured for the purpose of metering.

In Fig. 7 it is shown that in a wet stack already present in a paper or cardboard manufacturing machine for smoothing the web, the same application devices as described above with metering options can be arranged.

In the present example, nozzle applicators have been selected.

The wet stack shown in FIG. 7 consists of 6 smoothing rollers, the lower one being provided with a drive. These smoothing rollers are arranged one above the other and form press nips P ₁ to P ₅ .

The disadvantage of wet-stack rollers mentioned in the introduction to the description is therefore not yet canceled, but accurate and controlled humidification of the web and avoiding the other disadvantages mentioned in the introduction to the description are now possible.

The statements shown in the figures are in no way a dogma. Of course, they can be varied further. So are the individual smoothing rollers For example, it can also be reversed, or the web guide can be integrated in one direction other than the specified direction. Likewise, they are Order facilities freely selectable. Their use depends above all on the required Surface quality. In addition, more smoothing roller pairs can be used than in the examples are shown or even fewer (e.g. only a single pair).  

Following the smoothing according to the invention, further Connect coating processes, drying processes and smoothing.

Claims (8)

1. Device for surface treatment of a running material web, in particular made of cardboard, comprising:

• - A smoothing unit consisting of at least two smoothing rollers, which together form a press nip through which the material web runs.
• - An application device for moistening, sizing or pigmenting the material web to be smoothed, characterized in that a hard smoothing roller and a soft smoothing roller form a pair of smoothing rollers ( 2 , 3 , 4 ) and the application device ( 5 , 6 , 7 , 8 , 9 , 10 , 11 ) at least one of the two smoothing rollers of the pair of smoothing rollers ( 2 , 3 , 4 ) is directly assigned.

2. Apparatus according to claim 1, characterized in that a plurality of a press nip (P1, P2, Pz) with each other smoothing roller pairs ( 2 , 3 , 4 ) are provided, which are arranged vertically one above the other or horizontally one behind the other in the running direction of the material web (B) . 3. Apparatus according to claim 2, characterized in that the smoothing roller pairs ( 2 , 3 , 4 ) are arranged such that a hard smoothing roller is parallel to a soft smoothing roller. 4. The device according to claim 2, characterized in that the smoothing roller pairs ( 2 , 3 , 4 ) are arranged such that the hard smoothing rollers and the soft smoothing rollers are located on one side of the web. 5. Apparatus according to claim 2, characterized in that the smoothing roller pairs ( 2 , 3 ) are offset from one another and are arranged without a distance from one another, so that seen in the direction of travel of the material web, the smoothing rollers which are now one above the other have a further press nip (Pz) or nip ( S) form. 6. The device according to one or more of claims 1-5, characterized in that the application device is a known nozzle applicator ( 11 ) with metering device in the form of a doctor blade ( 6 ) with a smooth or grooved surface or a doctor blade ( 8 ), a sump applicator ( 5 ), or a free jet nozzle applicator ( 7 ) or a roller applicator ( 9 ) with a transfer roller ( 10 ) is provided. 7. The device according to one or more of claims 1-5, characterized in that the press nip (P ₁ , P ₂ , Pz) between the smoothing roller pairs ( 2 , 3 , 4 ) with a freely adjustable, independent of the roller load line force is applied . 8. The device according to claim 6, characterized in that the application device ( 5 , 6 , 7 , 8 , 9 , 10 , 11 ) is assigned to the hard smoothing roller.