DE29712431U1 - Device for applying a liquid or pasty medium to a surface moving in one direction - Google Patents

Description

PATENT ATTORNEYS

DiPL-INO. FA WEICKMANN

DlPL-CHEM. B. HUBER

DIRECTOR H. LISKA

DIPL-PHYS. DR. J. PRECHTEL

DIPL-CHEM. DR. B. BÖHM

DIPLiHEM. DR. W. WEISS

DlPL-PHYS. DR. J. TEESMEYER

DIPL-PHYS DR M. HERZOG

Our sign:

16567G DE/HGTUct

Applicant:

Voith Sulzer Paper Machines GmbH
St. Pöltener Street 43

D 89522 HEIDENHEIM

PO BOX 860 820

81635 MUNICH

KOPERNIKUSSTRASSE 9

81679 MUNICH

TELEPHONE (089) 4 55 63-0 TELEX 5 22 621 FAX (089) 4 70 50 68 eMail weickmann@compuserve.com

U. JuH 1997

Device for applying a liquid or pasty medium to a surface moving in a direction

Device for applying a liquid or pasty medium to a surface moving in one direction

Description

The invention relates to a device for applying a liquid or pasty medium to a surface moving in a running direction, for example a material web, in particular made of paper or cardboard, or an application roller transferring the application medium to such a material web, the device comprising an application device assigned to the running surface for applying the liquid or pasty medium to a line area of the running surface while leaving a line-free area separated from the line area by a line edge on at least one of the two side edges of the running surface, a leveling device for leveling the liquid or pasty medium applied to the running surface in the line area, and a line edge limiting device assigned to the leveling device for preventing the at least one line-free area separated from the line area by a line edge from being covered with liquid or pasty medium as a result of the effect of the leveling device on the liquid or pasty medium applied in the line area.

Such application devices are known from the prior art. For example, EPO 617 161 B1 describes a device in which excess application medium accumulating immediately in front of the leveling device is prevented from undesirably passing over from the coating area into the coating-free area by means of lateral seals.

However, since there is a clear gap between the running surface and the side seals, application medium back pressure that forms in front of the leveling device causes application

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medium into the non-streaked area, which must subsequently be removed. This is done by subjecting this area to a rinsing process in which a liquid is continuously sprayed onto the non-streaked area of the running surface in order to remove the application medium located there. The rinsing liquid, together with the washed-off application medium, drips off the surface and is collected in a collecting channel provided for this purpose, in order to ultimately be discharged from the process as waste. With such an application device, it is not guaranteed that the entire amount of application medium that has transferred over will be removed from the non-streaked area. This means that residues of application medium may remain, which reduces the quality of the product. Another disadvantage is that of increased application medium consumption, since the amount of application medium that has undesirably transferred over to the non-streaked edge is largely lost through the rinsing process. In addition, in the device known from EP 0 617 161 B1, the need for rinsing liquid, for example water, is relatively high, which leads to undesirable environmental pollution.

From DE 34 04 706 A1, a generic application device is known which in principle has the same functionality as the aforementioned prior art. In this device, the sealing element and the device supplying the rinsing liquid are provided as a single piece in the form of a plastic part. This application device also has the disadvantage of increased application medium consumption and a high demand for rinsing liquid, the latter of which must also be disposed of.

In contrast, it is the object of the present invention to provide an application device of the generic type with which a high-quality, line-free edge can be achieved while at the same time reducing the consumption of application medium.

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This task is solved in a generic application device in that the line edge limiting device comprises at least one sealing element with a sealing surface facing the running surface in the area of the line edge, into which at least one fluid channel for supplying a sealing medium opens. As already explained in the assessment of the state of the art, excess application medium accumulates immediately in front of the leveling device, which also presses in the direction of the line-free area due to the resulting dynamic pressure. By supplying sealing medium into the area between the sealing surface and the running surface, a counterpressure can be built up that counteracts the dynamic pressure in the application medium. Such a line edge limiting device thus prevents application medium from passing from the line area into the line-free area with its sealing element or, ideally, even completely prevents such a pass.

The sealing element of the line edge limiting device according to the invention therefore effectively seals the line-free area from the line area by using the sealing medium. The need for sealing medium is significantly lower than the need for rinsing liquid or cleaning liquid in the prior art, because the sealing medium is practically not contaminated with application medium due to the effective sealing effect, which basically enables it to be used multiple times. In addition, the loss of application medium due to overflow into the line-free area is negligible.

In order to be able to coat material webs with different formats or to be able to vary the width of the line-free area or the line area, it is intended that the line edge limiting device can be moved and adjusted transversely to the running direction of the surface. This increases the flexibility of the application device for the production of various

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a wide range of material web widths, which is desirable for example for different product designs in the paper industry.

In order to be able to vary the application properties, for example the application thickness, in the coating area as required while maintaining the same quality of the coating-free area, the coating device according to the invention is designed so that the coating edge limiting device can be positioned against the running surface. If the feed rate of the application medium in the coating area is increased while maintaining the properties of the running surface, a larger accumulation of application medium occurs in front of the leveling device, which is reflected in a larger accumulation pressure. In order to prevent accumulated application medium from overflowing into the coating-free area, the coating edge limiting device can be positioned more strongly against the running surface, thereby increasing the sealing effect. Furthermore, variable positioning of the coating edge limiting device with a component orthogonal to the running surface allows the coating edge limiting device to be positioned more or less strongly against the running surface depending on the properties of the running surface, in order to prevent damage to it. In addition to or as an alternative to the delivery of the line edge limiting device, it is also possible to increase the supply of sealing medium in order to generate a greater counterpressure, which counteracts the higher dynamic pressure in the area of the sealing surface.

In a particularly effective design of the sealing element with regard to the sealing effect, it is provided that the sealing surface forms a gap with the running surface that tapers in the running direction. This gap thus tapers in the direction of the increasing dynamic pressure of the application medium, i.e. in the direction of the equalizing device, which means that the gap is narrowest at the point where the highest dynamic pressure occurs. This measure allows the supply of

Sealing medium must be kept within narrow limits even at high back pressure in order to compensate for the back pressure.

In a further development of the invention, it is provided that the sealing surface in the area close to the leveling device rests against the running surface, whereby a transfer of application medium through mechanical contact between the sealing element and the surface can be prevented and the sealing medium only has direct contact with the application medium in areas of lower dynamic pressure.

The design of the sealing surface can be varied. For example, in a simple, easily manufactured design, the sealing surface has a straight contour across the running surface in the running direction. This allows the sealing element to rest on the running surface across the entire width, which reduces the contact pressure and thus also reduces the mechanical load on the running surface.

Alternatively, a recess oriented in the running direction is provided in the middle of the sealing surface. This design of the sealing element creates lips to the left and right of the recess, which may rest in sections on the running surface. If the sealing element is subjected to sufficient pressure over these lips, they deform, i.e. beads form on their side surfaces in the contact area. This increases the sealing effect.

In this design variant of the sealing surface, it is preferably provided that the fluid channel opens into the recess. This means that the sealing medium initially collects in the recess, which creates a uniform pressure profile over the entire length of the recess and, ideally, also the sealing surface (in the running direction). This also

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in the edge areas of the sealing surface, the overflow of sealing medium is prevented. In addition, this can counteract deformation of the lip adjacent to the line area due to dynamic pressure.

A further advantage of the design of the sealing surface with the above-mentioned recess is that excess sealing medium essentially exits from the front or rear recess openings and can thus be collected in a targeted manner. It is also conceivable that the recess on the front or rear is possibly even closed on both sides. In this case, the sealing medium exits through the tapered gap in the direction of the line-free area. In this case, too, a targeted collection of excess sealing medium is possible.

The sealing element can be made of various materials, for example plastic materials. In order to ensure low mechanical stress on the running surface, it is advantageous if the sealing element is made of rubber or rubber-like material, for example NBR (nitrile butadiene rubber), CR (chloroprene rubber), foam rubber or the like, as the sealing element can then adapt to the contour of the running surface, which not only protects the running surface but also increases the sealing effect.

Due to the direct contact between the sealing element and the running surface, the sealing element is subject to wear, for example friction-related abrasion. Although the wear is reduced by the lubricating effect of the sealing medium, it still occurs to a limited extent and can possibly (after a longer period of operation) reduce the function of the sealing element. In order to ensure high-quality results even after the application device has been in operation for a longer period of time,

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In order to be able to manufacture products, it is proposed to use replaceable sealing elements, i.e. sealing elements that can be replaced with a new sealing element if they become too worn.

Various materials can be used as sealing media. For example, it is conceivable to use a gas, such as air, as a sealing medium. However, it is more advantageous to use a liquid, such as water, as a sealing medium. Due to their viscosity and incompressibility, liquids are well suited as a counterpressure medium against the dynamic pressure of the liquid or pasty application medium.

When using a liquid as a sealing medium, it is advantageous to provide the device with a collecting container arranged in the area of the line edge limiting device. This collecting container serves to collect excess sealing liquid and, if necessary, to feed it into a circuit in order to reuse it. The line edge limiting device according to the invention offers the advantage that the sealing medium can be collected almost uncontaminated, i.e. largely without contamination by application medium, and can be used in the circuit without reprocessing steps. Such a collecting container also offers the advantage that the device becomes less contaminated and that any corrosive sealing and/or application media can be collected directly at the exit point, thus preventing corrosion damage to sensitive components.

As already mentioned at the beginning, the application device according to the invention can be used both for the direct and for the indirect application of the liquid or pasty medium onto a material web. In the first case, the running surface is formed directly by a surface of the running material web, while in the second case it is formed by the surface of a rotating application roller or a moving

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moving application belt. Of course, the liquid or pasty medium can be applied to the material web on one or both sides using the application device according to the invention.

In the following, the invention will be explained in more detail using two embodiments based on the accompanying drawings, whereby the liquid or pasty medium is applied directly to one side of a moving material web in both embodiments. It shows:
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Fig. 1 is a schematic side view of an application device according to the invention;

Fig. 2 is a schematic sectional view of the application device according to the invention along the line H-II from Fig. 1 or 3;

Fig. 3 is a sectional view of the application device according to the invention along the line III-III in Fig. 2;

Fig. 4 is a schematic sectional view of the application device according to the invention along the line IV-IV of Fig. 3;

Fig. 5 to 7 are views analogous to Fig. 2 to 4 of a further embodiment of the application device according to the invention.

In Fig. 1, an application device according to the invention is generally designated 10. This serves to apply a uniform layer of a liquid or pasty medium to a surface 12 of a material web M moving in the running direction A, for example made of paper or cardboard. The material web is guided on the input and output sides by a guide roller 14 and between the guide rollers 14 over the angular range σ by a counter-pressure roller 16, which moves accordingly.

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the running direction A of the material web M and its running speed in the direction of arrow B. In the contact area 18 defined by the angle range α, the material web M first runs past an application device 20, with which liquid or pasty application medium 21 is applied to a line area T (see Fig. 2) of the surface 12 of the material web M. In its further course, the material web M then reaches the area of a leveling device with a line edge limiting device 22 arranged immediately in front of it in the running direction A. In the illustrated embodiment, the leveling device comprises a squeegee blade 28, which is accommodated in a squeegee bed 30.

In the following, a first embodiment of a line edge limiting device 22 according to the invention will be described with reference to Figs. 2 to 4.

In Fig. 2, a sectional view along line ll-ll from Fig. 1 or Fig. 3 is shown. This shows a section of the counter-pressure roller 16 around which the material web M is guided, the course of which on the counter-pressure roller 16 is shown in dash-dot lines. Below the material web M, the line edge limiting device 22 is arranged, which serves to achieve a defined line edge 32 between the line area T and a line-free area S on the material web M. The line edge limiting device 22 comprises a sealing element 24 and a holding part 26, which serves to accommodate the sealing element 24 (not shown in more detail). A fluid channel 34 is provided in the sealing element 24, which connects to a corresponding feed channel 36 in the holding part 26. Sealing medium is fed to this feed channel 36 from a reservoir (not shown), which can be part of a circuit, for example. The fluid channel 34 opens into a sealing surface 40 via an outlet opening 38. Behind the line edge limiting device

The doctor blade 28 is arranged in the device 22 and serves to scrape off excess application medium 21.

According to Fig. 3, the sealing surface 40 lies directly in front of the doctor blade 28 on the surface 12 of the material web M and, due to its shape, forms together with the surface 12 a gap 42 that tapers in the running direction A. The sealing element 24 can be made, for example, from rubber-elastic material or from rubber, whereby it can adapt to the contour of the material web M guided by the counter-pressure roller 16 when fed in the direction of arrow Y via a feed device (not shown). Laterally next to the line edge limiting device 22, according to Fig. 2, in the direction of the counter-pressure roller end 46, a collecting container 44 is arranged, which can also be part of a sealing medium circuit already mentioned above.

During operation, application medium 21 accumulates in front of the doctor blade 28 and attempts to get into the gap 42 due to the dynamic pressure caused by the movement of the material web. The sealing medium emerging from the outlet opening 38 in the area of the sealing surface 40 forms a counterpressure in the area of the line edge 32 between the sealing surface 40 and the opposite section of the material web M, which counteracts the penetration of the application medium 21 into the gap 42. In order to maintain the counterpressure, sealing medium flowing in thus flows out of the gap 42 on the side of the sealing element 22 that is remote from the application medium (see arrows C) and reaches the collecting container 44. From this collecting container 44 it can then be conveyed, for example, into the above-mentioned reservoir or emptied into a drain.

In the area of high dynamic pressure, i.e. directly in front of the doctor blade 28, the sealing surface 40 of the sealing element 24 is in contact with the material web M guided by the counter-pressure roller 16. By means of a feeding movement in the direction Y, the contact pressure in the area of

Sealing surface 40 can be increased. This prevents application medium 21 from entering the line area T beyond the line edge 32 into the line-free area S in the area of high dynamic pressure. By using rubber-elastic material for the sealing element 22, a sufficiently high contact pressure in the area of the sealing surface 40 results in a bead-like deformation of the sealing element 24 at its edges, as shown in Fig. 4 (section along line IV-IV from Fig. 3). This bead-like deformation results in an improved sealing effect and largely prevents application medium 21 from penetrating the line-free area S of the material web M.

Fig. 2 also shows that the line edge limiting device 22 can be moved in the direction of the double arrow X, i.e. transversely to the running direction A of the material web M, via a mechanism not shown. This makes it possible to position the line edge 32 differently relative to the material web M, whereby the line-free area S or the line area T can be made wider or narrower. This means that, for example, the application device 10 can be adapted to material webs M of different widths, which makes its use more flexible.

In the case shown, the sealing element 24 comprises only one fluid channel 34. However, it is also entirely conceivable that the sealing element 24 comprises several fluid channels, which, for example, open out one after the other in the direction of travel A or evenly or unevenly distributed over the sealing surface 40. The sealing element 24 can be fastened in the holder part 26 by various connection mechanisms, for example a clamp connection, screw connection or similar. It is important, however, that on the one hand the holder of the sealing element 24 does not allow any unwanted leakage of sealing medium in the area of the holder part-sealing element cut parts, i.e. a tight holder is provided, but on the other hand that the holder can still be relatively easily removed in order to

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To be able to remove sealing element 24 and replace it with a new one if necessary.

A second embodiment of the line edge limiting device 22', in particular of the sealing element 24', is described below with reference to Figures 5, 6 and 7, the individual figures corresponding in their arrangement to the views of the described Figures 2, 3 and 4. The embodiment according to Figures 5 to 7 corresponds essentially to the embodiment according to Figures 2 to 4. Similar components therefore have the same reference numerals as in the first embodiment, whereby the reference numerals of modified components have been provided with a " ' ". Furthermore, the embodiment according to Figures 5 to 7 will only be described below insofar as it differs from the embodiment according to Figures 2 to 4, to whose description we otherwise expressly refer.

This second embodiment differs essentially only in the design of the sealing surface 40' of the sealing element 24' from the first embodiment. A recess 50 oriented in the running direction A with a width b and a depth t is provided in the sealing surface 40'. Sealing webs 52 and 54 extend to the left and right of the recess 50, which run parallel in the running direction A, separated by the recess 50, and whose surfaces lie in a common plane, namely the plane of the original sealing surface 40.

If the surfaces of the two sealing webs 52 and 54 are now brought into contact with the surface 12 of the material web M facing them by moving the line edge limiting device 22' in the direction Y, they deform in the contact areas as shown in Fig. 7, so that bead-like sealing lips 55 are formed on the sides, which increase the sealing effect against the line-free surface due to the dynamic pressure.

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Increase the area of application medium pressing against the surface. The sealing medium supplied via the supply channel 36 and fluid channel 34 collects in the recess 50 and forms a uniform counterpressure profile along both opposite recess flanks 56 and 58, each associated with the sealing webs 52 and 54. Thus, a deformation of the contact web 52 triggered by the dynamic pressure of the application medium 21, which would result in application medium 21 overflowing over the line edge 32, is largely excluded, since such a deformation is counteracted by the counterpressure of the sealing medium on the recess flank 56.

With such a design of the sealing element 24' with the recess 50, sealing medium can exit from the openings both in and against the running direction A of the material web M, and, as in the previous first embodiment, laterally through the gap 42 in the direction of the counter-pressure roller end 46 (see arrows C). In order to achieve the most complete possible collection of the excess sealing medium, the collecting container 44' is U-shaped and is arranged next to the two end faces 60 and 62 of the sealing element 24', which have the recess openings, and next to the side 64 remote from the coating area. Collected sealing medium can, as already mentioned in the first embodiment, be fed into the circuit via the storage tank for reuse. By providing the recess 50 in the sealing surface 40', the sealing effect of the sealing element 24' can be increased by the formation of the lips 55 and the pressure conditions on their flanks 56 and 58 can be made even more favorable.

Of course, the line edge limiting device 22' of the second embodiment can be subjected to various modifications in accordance with that 22 of the first embodiment, for example, several fluid channels can be arranged in the sealing element.

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the sealing element 24' can be removably mounted in the support part 26. Furthermore, the same material as for the sealing element 24 of the first embodiment can be used for the sealing element 24' of the second embodiment.

In the embodiments described above, only one line edge limiting device 22, 22' is arranged on the right-hand side of the material web M as seen in the running direction A. Of course, a correspondingly mirror-symmetrical line edge limiting device can also be arranged on the left-hand side of the material web M to achieve a line-free area, which can have all of the features described above.

Claims (1)

- 15 - Expectations 1. Device (10) for applying a liquid or pasty medium (21) to a surface (12) moving in a running direction (A), for example a material web (M), in particular made of paper or cardboard, or an application roller transferring the medium to such a material web, comprising: an application device (20) associated with the running surface (12) for applying the liquid or pasty Medium (21) to a line area (T) of the current Surface (12) leaving a portion of the stroke area (T) line-free area separated by a line edge (32) (S) on at least one of the two side edges of the running surface (12), a leveling device (28, 30) for leveling the liquid or pasty medium (21) applied to the running surface (12) in the line area (T) of the running surface (12), and - a line edge associated with the equalizing device (28, 30) Limiting device (22, 22') for preventing the at least one line-free area (S) from being covered with liquid or pasty medium (21) as a result of the effect of the leveling device (28, 30) on the liquid or pasty medium (21) applied in the line area (T), characterized, that the line edge limiting device (22, 22') comprises at least one sealing element (24, 24') with a sealing surface (40, 40') facing the running surface (12) in the region of the line edge (32), into which at least one fluid channel (34) opens for supplying a sealing medium. 2. Device (10) according to claim 1, characterized in that the line edge limiting device (22, 22') is displaceable and adjustable transversely to the running direction (A) of the running surface (12). 3. Device (10) according to one of the preceding claims, characterized in that the line edge limiting device (22, 22') can be adjusted against the running surface (12). 4. Device (10) according to one of the preceding claims, characterized in that the sealing surface (40, 40') forms with the running surface (12) a gap (42) tapering in the running direction (A). 5. Device (10) according to one of the preceding claims, characterized in that the sealing surface (40) is transverse to the running direction (A) has a straight contour. 6. Device (10) according to one of claims 1 to 4, characterized in that a recess (50) oriented in the running direction (A) is provided centrally in the sealing surface (40'). 7. Device (10) according to claim 6, characterized in that the fluid channel (34) opens into the recess (50). 8. Device (10) according to one of the preceding claims, characterized in that the sealing element (24, 24') is made of rubber or rubber-like material, for example NBR, CR, foam rubber or the like. 9. Device (10) according to one of the preceding claims, characterized in that the sealing element (24, 24') is replaceable. - 17- 10. Device (10) according to one of the preceding claims, characterized in that the sealing medium is a liquid, for example water. 11. Device (10) according to one of claims 1 to 10 , characterized by a collecting container (44, 44') arranged in the region of the line edge limiting device (22, 22'). 14.07.97 11:19