EP1272709B1 - Application device - Google Patents

Abstract

The air boundary layer reduction unit is a suction device (26) with resilient sections (28, 30, 32) sliding on the paper ground. Preferred features: The resilient section is a dragging scraper (28), preferably at the outlet side of the suction unit. It is plastic film, sheet metal or a composite. It is curved in the direction of running (L). A brush (30) is included at the inlet side. It has bristles of differing hardness, increasing in the running direction. Spacing between non-flexible sections and the ground, is about 10 mm. Spacing between the trailing edge of the suction unit and the point of incidence of coating medium is 1-100 mm, preferably 10-50 mm. A variant based on the foregoing principles employs an air blower in place of the suction device. In further implementations, a sealing roller is employed and/or a conditioner (a strip) removes the uppermost layers of the air boundary layer.

Description

The invention relates to a device for applying liquid or pasty application medium by means of an application work on a running Underground according to the preamble of claim 1.

Although the air boundary layer carried by the subsurface also at other types of commissioned work, the order result disadvantageous can influence, the invention is illustrated below using the example of a Curtain applicator are discussed in more detail, i.e. one Application device in which the application works the application medium as a curtain or moving essentially due to gravity Emits veil to the underground.

When coating material webs using a curtain applicator (also known as "curtain coating") the application medium to the surface in the form of an application medium curtain issued, which is due to gravity from Commissioned work moved to the underground. That the curtain commission is at a predetermined distance from the surface Among other things, it has the advantage that it breaks down, for example is exposed to a lower risk of damage. Curtain coaters differ from other "contactless" commissions, for example free jet nozzle applicators, in which the movement of the order medium from the order work to the underground mainly comes from the ejection impulse from the delivery nozzle of the application unit, fundamental since the shape of the emerging from the dispensing nozzle Curtain only the interplay between the surface tension of the application medium and gravity. The surface tension tries to make the curtain based on its volume or its cross-sectional area has a very large surface or Has circumferential length to contract so as to its surface reduce. Only gravity opposes this effect Tries to stretch the curtain. It is therefore easy to see that it is all the more it is more difficult to have a uniform thickness across the entire working width Obtain the gas medium curtain the larger this working width.

The coating of material webs using a curtain applicator, that the material web the order medium as in the The application medium curtain moves due to gravity or veil is from the coating of photographic Films, tapes and the like have long been known. Indeed the material webs in these areas of application have a significant impact smaller width than that of modern plants for the production of Paper and cardboard webs is the case where material web widths of more than 10 m are required. One even over this width to be able to form a thick application medium curtain and keep it stable a task that is far from obvious to move away from the comparatively easy to control known narrow Application medium curtains suggestions for a functional Expected solution. In addition, the material webs move in modern plants for the production of paper and cardboard webs with Speeds of up to 3000 m / min, which is a multiple of that Is the speed at which the well-known narrow material webs move, and moreover another high burden on the stability of the Order medium curtain represents.

An application device of the generic type is known from DE 199 03 559 A1 known. DE 199 03 559 A1 presents a whole range of Principles of action, which should make it possible for the material web air boundary layer carried directly in front of a curtain application to weaken. This is done, among other things, by a sealing element, which extends in the material web transverse direction and on the material web surface is applied. The sealing element can, for example, as a roller be trained, which can be driven in such a way that their Lateral surface near the contact area with the material web in the same Direction as the web of material moves. The disadvantage of this device is that on the material web after passing the sealing element again form an air boundary layer carried by the material web can.

US 3 369 522 A1 discloses a curtain coating application device, in the direction of the flow before the point of impact of the order medium on the A blade-like sealing element is provided on the ground, which lies across the direction of travel of the subsurface extends. The blade-like sealing element itself can be used with a Suction nozzle opening pointing underground as a suction device be trained.

US 5 336 534 A1 discloses a curtain coating application device, where one near the point of impact of the order medium on the Ultrasound source arranged below to influence the Material layer carried air layer is provided.

EP 0 489 978 A1 also shows a curtain coating application device. This is a material web guided around a counter roller through a in the area of the separation point of the material web from the Coating medium impinging on the counter roller coated. In Running direction in front of the impact point is one of the contours of the Air-roller weakening device designed following the counter-cylinder cylinder segment intended. This air layer weakening device is in close proximity, but at a distance from Surface of the counter roller arranged so that a gap between the the counter-rotating material web and the air layer weakening device is provided. In one between the Entry point of the material web into and, the exit point of the Material web from the weakening device Intermediate section is a device for extracting air intended.

WO 97/03009 deals with the problem of drying Material webs after applying media, namely printing inks, especially in gravure web offset and flexo printing. She suggests that Gas molecules on the surface of the material web by means of a corona discharge to ionize and accelerate towards an electrode to due to the gas exchange at the Material surface to increase the drying efficiency.

Applicant's DE 198 17 202 A1 describes an application device known in which the weakening device is an elastic Sealing plate includes which is supported at one end and with its opposite free end to the underground, the Sealing plate at one between its bearing end and hers free end located forming an axis of rotation like this is supported that a deflection of the between the bearing End and the support point located sealing plate section as a result a prevailing differential pressure between the two plate sides a deflection of the between the support point and the free end located sealing plate section at least counteracts especially in the case of higher differential pressures Predeterminable maximum distance between the sealing plate and the To keep underground. The structure and function of this Disclosure content relating to the weakening or sealing device DE 198 17 202 A1 is therefore hereby fully referenced taken and made part of the disclosure of this application.

With the help of this embodiment, functional impairments can essentially also at higher ground speeds be excluded. Firstly, from the underground entrained interference bodies pass through the weakening device without so that there is a risk of damage to the sealing plate, and without that the sealing effect would be permanently lost. As a result of Support of the relatively elastic sealing plate is prevented at higher differential pressures, such as those in the area of one Vacuum-producing ventilation equipment can occur Distance between the sealing plate and the base increased. So each has a deflection between the bearing side End and the support point located sealing plate section in the Way in between the support point and the free end Sealing plate section from that an undesirable deflection or Deflection of the latter is practically compensated.

For the sake of completeness, we refer to the further state of the art DE 198 03 240 A1 and DE 198 29 449 A1 referenced.

It is an object of the present invention, a generic Specify the device in which the carried by the underground Air boundary layer can be weakened more than at the state of the Technology.

This object is achieved by a device for applying liquid or pasty application medium by means of an application unit a running surface, where the surface is the Surface of a material web, in particular made of paper or cardboard, and in the case of indirect application, the surface of a transfer element, preferably a transfer roller, which is the application medium transfers to the surface of the material web, wherein in the direction of the A device for weakening the substrate in front of the application air boundary layer carried along by the substrate is arranged, and wherein the weakening device comprises a sealing element which is sealingly pressed against the surface and in this Rolls off essentially without slip. This sealing element is due its pressure against the underground an effective barrier for the Air boundary layer and also represents due to the rolling on the Underground sure that the surface of the underground is not too much is charged.

According to the invention it is proposed that in the running direction of the One between the sealing element and the application Suction opening of a suction device is arranged. By means of this The part of the air boundary layer that is separated from the Sealing element could not be removed from the surface, further be weakened. The sealing element can except for his essentially engaging the subsurface be completely received in a suction box of the suction device. This applies in particular to sealing rollers with a larger diameter.

The sealing element can be, for example, a sealing roller and / or a endless sealing tape.

To rebuild an air boundary layer on the running route of the Between the weakening device and the impact position to be able to prevent the application medium on the surface, it is advantageous if this running distance can be as short as possible. Around To be able to achieve this is a further development of the invention suggested that the sealing roller have a diameter of between about 10 mm and about 38 mm. Such rod-like sealing elements can due to their relatively small diameter especially close to where the order medium hits the Be arranged underground. In principle, however, can also Sealing rollers of larger diameter are used, as further will be explained in more detail below.

To further reduce the stress on the surface of the substrate can, it is proposed that the sealing element is a rubber Surface. However, it is also possible for the sealing element has a metallic, for example a chrome-plated, surface. to This can increase the efficiency of weakening the air boundary layer Sealing element can also be tempered, i.e. heatable and / or coolable, or / and be electrostatically chargeable.

To further increase the barrier effect for the air boundary layer can be provided that the sealing element as a suction element is trained. The sealing element can also be used as a pump element be formed, the gas, preferably air, water vapor or the like, ejects to the air boundary layer from the ground "Blow away".

Both in the case of training as a suction element and in the case of Training as a pump element, the jacket of the sealing element with be provided with a plurality of openings or / and made of porous Material be formed.

To improve the suction efficiency, it can also be provided that the Suction opening on the outlet side and / or inlet side of a panel element is limited, for example an elastically deformable panel element, preferably as a scraper against the surface of the Underground is employed. This drag scraper hampers the Movement of the air boundary layer to the application work and leads thus to the air entrained in the air boundary layer. This destroys the laminar character of the air boundary layer flow and leads to their at least partial conversion into a turbulent one Flow, which makes suction easier.

The drag scraper can be a flexible film, preferably made of plastic, Metal sheet or a composite material may be formed. The flexible Foil nestles against the suction of the suction device the underground, which improves the sealing on the one hand and prevents others from building a new air boundary layer. Is the Drag scraper made of sheet metal, preferably stainless steel sheet with a thickness of at most 0.2 mm. As beneficial have also scrapers made of composite material with a Surface coating made of Teflon proven. The composite material ensures thereby for the required temperature resistance and flexibility, while the Teflon surface coating for low friction between the drag scraper and the running surface. Furthermore, the drag scraper can be curved in the running direction, which is the elastic dodging eases and friction with the ground further diminishes.

Additionally or alternatively, this can be at least one elastic Aperture element but also include a brush, which is preferably on inlet end of the suction device is arranged. to brush place less strain on the surface than an elastic film formed scraper. For this reason, the Use of brushes preferred because of the material web and especially theirs Surface needs special protection.

The effectiveness of the brush can depend on the hardness of its bristles and their Extension in the running direction can be influenced. For an order in one free movement of the material web, i.e. a section where the web of material not supported by a counter element, for example a counter roller pairs of brushes can be used to ensure functionality are used, with the brushes of each pair of brushes opposite sides of the material web are arranged. Can also the brushes comprise bristles of different hardness, the Bristle hardness preferably decreases in the direction of travel of the substrate. The hard bristles in the inlet area slow down the air boundary layer, while the subsequent softer bristles the laminar flow of the incoming air boundary layer gradually into a turbulent flow convert which is easier to remove from the surface. The softer bristles can preferably be made from natural hair, for example, horse hair.

In addition or as an alternative to the drag scraper and / or the brush the at least one elastic element is also made of foam, preferably Foam rubber, manufactured element include, for example is arranged on a side edge of the suction device. Such foam elements can easily adapt to their shape adjust surrounding harder parts. They are therefore special suitable in interaction with other elements such as drag scrapers or brushes to complete the suction device seal.

All of the above-mentioned types of elastically deformable elements can at a tear of the web and in the worst case subsequent winding of the web of material on the counter roller increasing effective diameter of the counter roll without Evade further, and after restoring the orderly Return to their original position or shape. They are therefore not subject to one or to one if the material web is torn off only tolerable low risk of damage.

On the one hand, the reconstruction of an air boundary layer on the railway section Prevent between the suction device and the applicator to be able to, but on the other hand if a curtain application is used a physical disturbance of the application medium curtain by the suction device or a part arranged thereon To be able to prevent, it is proposed that the distance between the downstream end of the suction device or one at arranged elastic end downstream of the suction device Elements, for example the drag scraper, and the impact position of the application medium on the substrate has a value of between approximately 1 mm and about 100 mm, preferably of between about 10 mm and about 50 mm.

According to a preferred embodiment of an application device of the In the present invention, the weakening device comprises a Electrode assembly. This electrode arrangement can Influence the air boundary layer in different ways and thus at least part of the laminar flow of the air boundary layer convert into a turbulent flow.

The electrode arrangement comprises a plurality of electrodes in the transverse direction of the Individual electrodes arranged adjacent to one another, preferably Needle electrodes, or at least comprises the electrode arrangement a flat electrode, which on its side facing the underground has a plurality of projections or needle tips, so it can Discharges occur between the electrode and the substrate. The Air molecules charged in these discharges are in the by the Electrode arrangement generated accelerated and can this leads to an at least partial destruction of the laminar character the flow of the air boundary layer.

The electrode arrangement can be used to increase the efficiency of this effect a distance of between about 2 mm and about 30 mm from the ground exhibit. Furthermore, the electrode arrangement can be on a predetermined electrical potential, which has a value of, for example between about 5 kV and about 60 kV, preferably about 30 kV.

However, it is an alternative to the discharge effect explained above also possible that the electrode arrangement a high-frequency electrical Alternating field emits. The frequency of the alternating field can be chosen such that at least some of the air molecules are closed Vibrations is excited. As a result of these vibrations again at least part of the laminar flow of the air boundary layer converted into a turbulent flow.

The further electrode arrangement can, for example, on the suction device, preferably its downstream end, and from it be arranged electrically insulated. It is particularly advantageous if the Electrode arrangement in the suction-active area of the suction device, i.e. for example in that of the at least one elastic element bounded area of the suction device is arranged. In this case namely, the suction device and the electrode arrangement do not work independently of each other, but complement each other in influencing the Air boundary layer. For example, that of the electrode arrangement generated turbulent portion of the flow of the air boundary layer immediately be sucked off by the suction device.

As an alternative to vibration excitation via an alternating electrical field can a comparable vibration excitation by means of a weakening device can be achieved, which comprises an ultrasound source. The The frequency of this ultrasound source can in turn be selected such that that at least some of the air molecules are excited to vibrate.

In a further development of the weakening device according to the invention it is advantageous if the weakening device is a conditioning device precedes which are the top layers of the Air boundary layer essentially completely removed. Usually hangs the efficiency of the weakening device depends on various influences, for example the running speed of the surface. The conditioning device ensures by removing the top areas of the Air boundary layer that dependence on these influences diminished, if not completely prevented. Also needs the weakening device no longer against the whole Air boundary layer, but only against that of the Conditioner passed part. This will make the The weakening device is relieved and can therefore be less powerful be trained.

In a simple embodiment, the conditioning device comprise a bar which extends in the transverse direction of the subsurface, which can be formed, for example, by a simple sheet metal strip. It However, it is also possible that the conditioning device is aerodynamic Exploits effects, for example by looking in the transverse direction has a cross section that is in the shape of an upside down Has wing profile.

Good results can be achieved, for example, if the Conditioning device from the surface at a distance of between about 3 mm and about 10 mm is arranged.

The conditioning device can be designed to be self-supporting or else be attached to the weakening device.

As already mentioned above, the weakening devices according to the invention can used in particular in an application device which has a curtain commission, i.e. on Commissioned work, which is the order medium as essentially gravity moving curtain or veil on the surface emits.

Fig. 1 bis 8

grobschematische Seitenansichten verschiedener Ausführungsformen von vorteilhaften Auftragsvorrichtungen.

The invention will be explained in more detail below with the aid of some exemplary embodiments with reference to the attached drawing. It shows:

1 to 8

rough schematic side views of various embodiments of advantageous application devices.

1, an application device according to the invention is generally at 10 designated. It comprises a curtain application 12, from the Dispensing nozzle 14 application medium 16 as application medium curtain 18 a substrate U moving in the running direction L is delivered. in the The illustrated embodiment is the underground U from the surface 20a of a material web 20 is formed, on which the application medium 16 as Application layer 22 is applied.

To weaken an air boundary layer G is in the direction of L before Application unit 12 a suction device 24 with a suction box 26 provided that at a predetermined distance from the underground U is arranged. In order to achieve effective suction despite this distance to ensure, the suction area 26a of the suction box 26 in the illustrated embodiment to the environment by means of a A plurality of differently designed sealing elements 28, 30 and 32 sealed, all of which are designed as elastically deformable elements are.

With regard to the running direction L on the outlet side, there is one on the suction box 26 elastic film 28 attached, for example made of a composite material can be made of Teflon on its surface is coated. The film 28 takes you from top to bottom and right left curved path and hugs the surface 20a of the material web 20, which due to its inherent elasticity against the Material web 20 is biased. Furthermore, the film 28 by the Suction effect of the suction box 26 pressed against the underground U, which improves their sealing effect. In front of the film 28 the jams in the Suction area 26a of the suction box 26 penetrated air boundary layer G, what the laminar character of the flow of this air boundary layer G at least partially destroyed and the suction in the air boundary layer G air carried by the suction box 26 facilitated. The downstream End 28a of the film 28 has from the impact position P of the Curtain 18 on the underground U a distance d. This distance is d dimensioned such that on the one hand the reconstruction of an air boundary layer on the track section between the suction box 26 and the impact position P and physical contact between film 28 and curtain 18 can be prevented.

On the input side, the suction area 26a of the suction box 26 is from the brush 30 limited. This brush 30 brakes the one entering the suction area 26a Air boundary layer G and weakens their laminar character In favor of turbulent flow components. To increase the efficiency of the Effect of the brush 30 can the hardness of the bristles 30a of this brush 30 in Decrease running direction L, which is shown in Fig. 1 by a right to left decreasing line thickness of the individual bristles 30a of the brush 30 Dashes is indicated. Hard bristles are particularly suitable to slow down the air boundary layer G, since it is not so easy for it can be deflected, while soft bristles due to their higher mobility are more likely to convert the laminar flow into a convert turbulent flow.

Finally, through relatively long lines to the transverse direction Q in Lateral boundary elements 32 running essentially orthogonally indicated, which can be made of foam rubber, for example and to completely seal the suction area 26a relative to the Serve environment.

Finally, there is another one in FIG. 1 upstream of the suction device 24 Conditioning device arranged in the form of a triangularity bar. This Conditioning bar 36 has the task of covering the top layers of the air boundary layer G lift off before the subsurface areas of the air boundary layer the suction box 26 are supplied. As a result of this relatively weakening of the air boundary layer G, which is easy to provide, can Suction device 24 provided less power and thus less expensive become. In addition, the thickness of the air boundary layer G varies following the conditioning bar 36 is no longer as dependent of the operating parameters of the application device 10 than this without the conditioning bar 36 is the case.

In Fig. 2 is an embodiment of a not to the present invention computing device shown. This is general in Fig. 2 designated 110. In the running direction L in front of the curtain applicator 112 a deflection strip 140 is provided, one end 140a of which Takes part of the air boundary layer G from the underground U. Beyond that the deflection bar 140 is curved so that it has a part G ' of the tapped air flow is deflected by essentially 180 ° and can act on the air boundary layer G against the running direction L. As a result, the laminar character of at least the upper areas of the Air boundary layer G are weakened. A partition 142 ensures that the air flow G 'is essentially undisturbed against the Air boundary layer G can be conducted. The deflection bar 140 and the The partition 142 is preferably at a distance from the underground U less than 1 mm.

Another portion G "of the air tapped from the deflection bar 140 is directly through an opening 140b of the deflection bar 140 in a directed upstream of the application medium curtain 118. The hereby overpressure generated on the inlet side of the curtain 118 helps this to further stabilize against the influence of the air boundary layer G.

In the application device 210 according to FIG 3 is upstream of the curtain applicator 212 in the running direction L. a device 250 is provided which generates an electric field, through which the material web 220 moves. It can electrical field both lead to electrical discharges which the Electrically charge air molecules of the air boundary layer G and orthogonal to the Accelerate underground U. However, it is also possible that the Device 250 with a high-frequency electrical alternating field acts on the air boundary layer G, the frequency of which is selected such that at least some of the air molecules are excited to vibrate. Both Effects cause at least part of the laminar flow of the Air boundary layer G is converted into a turbulent flow, which in 3 by vortex arrows increasingly curved from right to left is indicated and leads to a weakening of the air boundary layer G.

An electrode arrangement corresponding to the field generating device 250 50 can also be provided in the embodiment according to FIG. 1 be, preferably at the downstream end of the suction box 26 between the suction box 26 and the film 28. The of this Electrode arrangement 50 outgoing discharge processes e disturb the laminar character of the air boundary layer G, so that of this entrained air can be extracted more easily from the suction box.

The application device 310, likewise not to be counted towards the invention 4 differs from the embodiment according to FIG. 3 only in that the upstream of the curtain applicator in the direction L 312 provided device 360 for weakening the of the air boundary layer G carried along with the material web 320 Ultrasound source, the frequency of which is selected such that at least a portion of the air molecules in the air boundary layer G. Vibrations are excited. With regard to the resulting Attenuation of the air boundary layer G is based on the explanations for FIG. 3 pointed.

Finally, the air boundary layer G, as shown in Fig. 5 for the Application device 410 is shown, also by means of a running direction L sealing roller arranged upstream of the curtain applicator 412 470 are weakened, which against the surface 420a of the Material web 420 is pressed and rolls on it. The coat 470a the sealing roller 470 is made of an elastic material, for example Rubber or a rubber-like material, made to withstand the stress the material web 420 as a result of the pressure on the roller 470 to be able to keep low. Furthermore, the roller jacket 470a has one Plurality of openings 470b, and the roller 470 is one Suction pump 472 connected, which from the air boundary layer G entrained air through the openings 470b at least partially from sucks the surface 420a of the material web 420.

Alternatively, the sealing roller 570, as shown in the example of FIG Application device 510 is shown in Fig. 6, but also one Have perforation-free roll jacket 570a. This sealing roller 570 forms together with a counter roll 574 a nip N through which the Material web 520 is passed. Since the web 520 the Counter roll 574 wraps around the nip N, and also the Sealing roller 570 in the area of the nip N against the material web 520 is turned on, the air boundary layer G in the nip N through the sealing roller 570 blocked.

Should the material web 520 be smoothed in order to influence its Thickness and / or smoothing or / and porosity profile before Medium application may be desired, so are the rollers 570 and 574 can also be used as heatable or coolable calender rolls. This is the Setting a specific line pressure or a specific one Surface pressure in the nip N is required, which is indicated in FIG. 6 by the arrows D is indicated.

To also those portions g of the air boundary layer G that the Nip N despite the sealing roller 570 could pass, is further weakening immediately after the sealing roller 570, the suction opening 576a of a suction box 576, which is connected to a suction pump 572 connected. On the outlet side, the suction opening 576a is by means of a Diaphragm element 528, for example one against material web 520 employed scraper, sealed. The suction opening 576a can connect directly to the sealing roller 570, as shown in FIG. 6 is shown, according to which the suction opening 576a by means of another Aperture element 528 'is divided in two.

To the running distance between the suction opening 576a and the Impact position P of the application 512 as a curtain 518 To be able to keep emerging medium 516 as short as possible Sealing roller 570 substantially entirely in suction box 576 added. That only that engaged with web 520 Circumferential section of the sealing roller 570 and adjacent to it, a safety distance between the web 520 and the Suction box 576 providing peripheral portions protrude from the Suction box 576 out.

Although the sealing rollers 470 and 570 shown in FIGS. 5 and 6 are each in Combined with a suction device, it is outside of the scope of the present invention in principle also possible To provide sealing roller alone. For example, see the Referring to the embodiment of FIG. 7, according to which a doctor rod-like Sealing roller 670, i.e. a sealing roller with a diameter of between about 10 mm and about 38 mm in a "doctor bed" 678 is supported against which led around a counter roller 674 Material web 620 is employed. This embodiment of the Application device 610 allows the length d of the running route between the sealing roller 670 and the impact position P of the from Application work 612 emerging order medium curtain 618 particularly to keep short.

In contrast to the doctor rod-like roller 670, the rollers 470 and 570 a diameter of up to depending on the machine width to 1000 mm, for example with a machine width of 4 m Diameter of about 500 mm. The arrangement of the aperture element 528 enables a small distance even with a larger roller diameter d to application medium curtain 518.

Finally, in Fig. 8 is an essentially contactless one Sealing device 780 shown in an application device 710 can be used, both alone and for example in combination with other sealing devices, such as the Embodiment according to FIG. 1 instead of the conditioning bar 36 Sealing device 780 includes a relatively resilient sealing plate 782 which at one end by means of one provided on a suction box 784 Bearing 786 is mounted and with its free end of the material web 720 opposite, from which it is at a distance X.

The sealing plate 782 is except for the end clamped in the bearing 786 curved, being different from that in the area of the suction box 784 provided negative pressure side 784a upwards to the positive pressure side is arched. It is at least in the area of its free end Introduced essentially tangentially to the material web 720.

The relatively elastic sealing plate 782 is at one between its bearing-side end and its free end located under 782a Formation of an axis of rotation extending transversely to the web running direction L. supported so that a deflection of the between the bearing End and the support point 782a located sealing plate portion 782b in Follow one that prevails between the two sides of the plate Differential pressure of an undesirable deflection or deflection of the between the support point 782a and the free end Sealing plate section 782c at least counteracts, in particular even at higher differential pressures a maximum distance X between the sealing plate 782 and the web 720. So that will achieved that, especially at higher differential pressures desired distance X is at least substantially maintained, i.e. especially does not get bigger.

In the present case, the relatively elastic sealing plate 782 is open the stiffer support plate 788 arranged on the vacuum side 784a. This is provided with through openings 788a and on its left End together with the adjacent end of the sealing plate 782 in the bearing 786 clamped.

The support point 782a and thus the axis of rotation formed in its area are closer to the free end of the sealing plate 782 than its bearing side End, in the present case in the area of the free end of the Sealing plate 782 is arranged. This results in the left one Sealing plate section 782b a relatively large, the differential pressure exposed attack surface, with the deflection of an undesirable Deflection of the sealing plate section adjacent to the material web 720 782c is counteracted in such a way that even with higher ones Differential pressures result in practically no change in the distance X. With the openings 788a provided in the support plate 788 are ensured that the between the bearing end and the support point 782a located sealing plate portion 782b in the required manner from Vacuum is applied.

As can be seen from FIG. 8, the sealing plate 782 is under Formation of an axis of rotation extending transversely to the web running direction L. through the free right end of the underlying stiffer support plate 788 supported.

The distance to be maintained between the sealing plate portion 782c and the material web 720 can be adjustable. In addition, this distance X even with the machine at a standstill or at low web speeds be given. Basically, however, is also one dynamic sealing possible, in which the sealing plate section 782c only when starting the machine, i.e. with increasing web speed is lifted off by a part of the air boundary layer G, whereby the desired distance X, however, at the latest when the operating speed is reached established. Because of the latest in operation non-contact sealing can also be set in this If there is no abrasion.

In any case, the sealing device 780 prevents that a larger proportion of those carried along by the material web 720 Air G in the area of the impact position P, not shown in FIG Order medium curtain arrives.

The air boundary layer G entrained by the material web 720 thus becomes largely scraped or stripped. Another advantage is too call that the sealing plate portion 782c on the surface of the Material web 720 carried impurities without further notice can dodge. And also in the event of a web break and "packing up" the Back-up roller 774 is at risk of damaging the sealing device 780 reliably prevented.

Claims (29)

1. Device (410; 510; 610) for the application of liquid or pasty application medium (516) by means of an applicator unit (412; 512; 612) to a moving substrate (U),
   the substrate (U), in the case of direct application, being the surface of a material web (420; 520; 620), in particular of paper or board, and, in the case of indirect application, being the surface of a transfer element, preferably a transfer roll, which then transfers the application medium to the surface of the material web, and
   a device (470; 570; 670) for attenuating the air boundary layer (G) carried along by the substrate (U) being arranged upstream of the applicator unit (412; 512; 612) in the running direction (L) of the substrate (U), said attenuation device comprising a sealing element (470; 570; 670) which is pressed in a sealing manner against the substrate (U) and rolls on the latter without slippage,
   characterized in that a suction opening (576a) of a suction device (576) is arranged between the sealing element (570) and the applicator unit (512) in the running direction (L) of the substrate (U).
2. Application device according to Claim 1,
   characterized in that the sealing element is a sealing roll (470; 570; 670).
3. Application device according to Claim 2,
   characterized in that the sealing roll (470; 570) has a diameter of up to 1000 mm.
4. Application device according to Claim 2,
   characterized in that the sealing roll (670) has a diameter of between about 10 mm and about 38 mm.
5. Application device according to Claim 1,
   characterized in that the sealing element is an endlessly circulating sealing belt.
6. Application device according to one of Claims 1 to 5,
   characterized in that the sealing element (470; 570; 670) has a rubber-covered surface (470a; 570a).
7. Application device according to one of Claims 1 to 5,
   characterized in that the sealing element (470; 570; 670) has a metallic surface (470a; 570a), for example a chromium-plated surface.
8. Application device according to one of Claims 1 to 7,
   characterized in that the sealing element (470; 570; 670) can be temperature-controlled and/or electrostatically charged.
9. Application device according to one of Claims 1 to 8,
   characterized in that the sealing element (470) is constructed as a suction element.
10. Application device according to one of Claims 1 to 8,
    characterized in that the sealing element is constructed as a pump element.
11. Application device according to one of Claims 1 to 10,
    characterized in that the cover (470a) of the sealing element (470) is provided with a plurality of apertures (470b).
12. Application device according to one of Claims 1 to 11,
    characterized in that the cover (470a) of the sealing element (470) is formed of porous material.
13. Application device according to any of the preceding claims,
    characterized in that the suction opening (576a) is bounded on the outlet side and/or on the feed side by a diaphragm element (528), for example a resiliently deformable diaphragm element, which is preferably set against the surface of the substrate (U) as a trailing scraper.
14. Application device according to one of the preceding claims,
    characterized in that the attenuation device comprises an electrode arrangement (250) arranged on the application medium application side of the substrate.
15. Application device according to Claim 14,
    characterized in that the electrode arrangement (250) comprises a plurality of individual electrodes, preferably needle electrodes, arranged adjacent to one another in the transverse direction of the substrate (U).
16. Application device according to Claim 14,
    characterized in that the electrode arrangement (250) comprises at least one flat electrode which, on its side facing the substrate (U), has a plurality of projections or needle points.
17. Application device according to one of Claims 14 to 16, characterized in that the electrode arrangement (250) has a distance of between about 2 mm and about 30 mm from the substrate (U).
18. Application device according to one of Claims 14 to 17,
    characterized in that the electrode arrangement (250) is kept at a predetermined electric potential which preferably has a value of between about 5 kV and about 60 kV.
19. Application device according to one of Claims 14 to 18,
    characterized in that the electrode arrangement (250) emits a high-frequency alternating electric field.
20. Application device according to Claim 19,
    characterized in that the frequency of the alternating field is selected such that at least some of the air molecules are excited into oscillation.
21. Application device according to one of Claims 14 to 20,
    characterized in that the electrode arrangement (50) is arranged on the suction device (26), preferably the downstream end thereof, electrically insulated from the latter.
22. Application device according to one of the preceding claims,
    characterized in that the attenuation device comprises an ultrasound source (360) whose frequency is preferably selected in such a way that at least some of the air molecules are excited into oscillation.
23. Application device according to one of the preceding claims,
    characterized in that a conditioning device (36), which substantially completely removes the uppermost layers of the air boundary layer (G), is arranged upstream of the attenuation device (24).
24. Application device according to Claim 23,
    characterized in that the conditioning device (36) comprises a bar extending in the transverse direction (Q) of the substrate (U).
25. Application device according to Claim 23 or 24,
    characterized in that the conditioning device (36), as viewed in the transverse direction (Q), has a cross section which has the shape of an aerofoil profile standing on its head.
26. Application device according to one of Claims 23 to 25,
    characterized in that the conditioning device (36) is arranged at a distance of between about 3 mm and about 10 mm from the substrate (U).
27. Application device according to one of Claims 23 to 26,
    characterized in that the conditioning device (36) is designed to be self-supporting.
28. Application device according to one of Claims 23 to 26,
    characterized in that the conditioning device is fitted to the attenuation device.
29. Application device according to one of the preceding claims,
    characterized in that the applicator unit (12) is a curtain applicator unit, which discharges the application medium (16) onto the substrate (U) as a curtain or veil (18) that moves substantially under the force of gravity.

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