Patent Application
20050115494
This is a continuation of PCT application No. PCT/EP2003/006479, entitled “DEVICE FOR COATING AND DRYING THE FRONT AND BACK OF A WEB, PARTICULARLY ONE CONSISTING OF PAPER OR CARDBOARD”, filed Jun. 18, 2003.
1. Field of the Invention
The invention relates to a coating/drying device having a first application device for applying liquid or pasty application medium to a first side of a material web, in particular of paper or board, moving in the running direction, and having a second application device for applying liquid or pasty application medium to a second side of the material web, opposite the first side.
2. Description of the Related Art
Coating/drying devices are generally known in the prior art. In these devices, it is usual for a layer of application medium to be applied to one side of the material web and for this then to be dried in a drying device. Only then is an application medium layer applied to the other side of the material web and likewise dried. The disadvantage with these coating/drying devices is, firstly, that two drying devices have to be provided, which is not only expensive in terms of procurement and maintenance of these drying devices but, moreover, significantly more overall space is required. Secondly, the energy efficiency of single-sided drying, that is to say the drying effect per unit of energy applied, leaves much to be desired.
What is needed in the art is a coating/drying device, which permits both sides of the material web to be coated and dried in a space-saving and energy-saving manner.
According to the present invention, a coating/drying device of the generic type is utilized in which the second application device is an application device acting without contact and in which the drying device is arranged downstream of the two application devices in the running direction of the material web. According to the present invention, therefore, no intermediate drying is carried out, that is to say no drying device is provided between the position of the first application device and the position of the second application device. This saves overall space otherwise required for the second drying device and the cost required for the procurement and the maintenance of the second drying device. Furthermore, the heat provided by the drying device can be absorbed not just by one moist application medium layer but by two moist application medium layers. The heat absorption, which is higher as a result, improves the energy efficiency of the coating/drying device according to the present invention as compared with coating/drying devices from the prior art.
According to another aspect of the present invention, the two application devices are arranged substantially at the same position in the running direction of the material web, and the drying device is arranged downstream of the two application devices in the running direction of the material web. At least one, preferably both, of the application devices can advantageously be designed as an application device acting without contact. However, it is not ruled out that at least one of the application devices is an application device transferring the application medium indirectly by way of a transfer surface of a transfer element, preferably a transfer roll, carrying the application medium in the form of an application medium layer.
By way of a configuration according to another embodiment of the present invention of the coating/drying device, it is possible to dispense with the intermediate drying if both sides of the material web are coated. This dispensing with intermediate drying, in the case of the arrangement of the two application devices substantially at the same position in the running direction of the material web, is also entirely compatible with an application acting with contact. If appropriate the medium is applied in excess to the material web.
The application device, acting without contact, applies the application medium to the material web substantially without any excess, known as a “1:1 application”. It therefore needs no excess application medium to be doctored off and no physical contact with the material web is required. As a result of this, the application device, acting without contact, stresses the material web to only a low extent, specifically only by way of the softening of the material web from the liquid contained in the application medium. The application device, acting without contact, can be a spray application device or a curtain application device.
In principle, the first application device can also be an application device coating the material web with contact. For example, a blade application device may be used, that is to say an application device having a doctor blade for evening out and/or metering the applied layer of application medium. Alternatively, the application device may be a film application device, that is to say an application device in which the material web runs through a nip formed between two rolls and, in this nip, the web is brought into contact with a film of application medium applied to the surface of one of the rolls. According to the invention, it is preferred if the first application device is also an application device acting without contact, for example, a curtain application device. The low stressing of the material web is important in connection with the present invention, in particular since, the material web does not experience any intermediate consolidation by way of the withdrawal of moisture in an intermediate drying device between the two application devices.
Depending on the overall space available, and the other boundary conditions for the arrangement of the coating/drying device, at least one of the curtain application devices can apply the application medium to the material web from above under the force of gravity. Additionally or alternatively, at least one of the curtain application devices can be assigned a deflection device, which deflects the application medium curtain from the curtain application device out of its course under the force of gravity. The deflection of the application medium curtain can be based, for example, on an electrostatic and/or electromagnetic interaction between the application medium in the application medium curtain and the deflection device. Electrostatically and/or electromagnetically operating deflection devices of this type are known in the prior art and will therefore not be explained in more detail here.
The application medium curtain from both curtain application devices may be deflected out of its respective course under the force of gravity by way of a deflection device. According to an exemplary web course, the material web can run substantially vertically from bottom to top, the two curtain application devices being arranged on either side of the material web. The two application medium curtains are deflected from their course under the force of gravity, which does not lead to any wetting of the material web, into an operating course wetting the material web, by utilizing the deflection device. In the case of the deflection of both application medium curtains, it is advantageous if the two application devices are arranged substantially at the same position in the running direction of the material web.
Furthermore, the two application devices may be arranged on a section of the material web running substantially in the vertical direction, preferably moving from bottom to top. If mention is made here of “running substantially in the vertical direction”, this is intended to include entirely more severe angular deviations from an exactly vertical course, if appropriate up to ±45°. However, a lower angular deviation from the exactly vertical course, for example ±20°, is more expedient.
The second application device can be arranged downstream of the first application device by a predetermined distance in the running direction of the material web. For example, the two application devices can be arranged in the sections of the run of the material web that run substantially horizontally, in order to permit application of the application medium from above. This is advantageous in particular when curtain application devices are used. Since this application “from above” is still readily possible even given deviations of up to 45° from an exactly horizontal course of the material web, the formulation “running substantially horizontally” is to be interpreted in a correspondingly manner.
An arrangement of the application devices, one above another, which utilizes the overall height available and thus saves overall length, results, for example, if the material web between the sections that run substantially horizontally is deflected through substantially 180° by way of at least one web deflection unit. It goes without saying that the formulation “deflected through substantially 180° ” is also to be interpreted widely in accordance with the above and can cover deflections from about 140° to about 210°.
In order to be able to prevent any influence on the surface properties of the application medium layer just applied, and thus still moist, by the web deflection units, responsible for the curved web courses, provision is made for the web deflection units between the first application device and the second application device to be arranged on the uncoated, second side of the material web. However, if use is made of what are known as “air turns”, that is to say deflection units in which the material web is guided without contact on a compressed air cushion expelled from these “air turns”, the web deflection units between the first application device and the second application device can also be arranged on the coated, first side of the material web.
Finally, it is also possible for a web turning device to be arranged between the first application device and the second application device. The axles or shafts of the deflection units of this web turning device run parallel to a section of the material web running into the respective deflection unit and at a predetermined angle with respect to the transverse direction of this web section. In this connection, “air turns” can also be used as web deflection units. These can be constructed, for example, as perforated pipes, the perforations being used to expel compressed gas for forming a compressed gas cushion.
Irrespective of the arrangement of the two application devices, it is advantageous if the two application devices are accommodated in a common housing, in order to prevent contamination of the entire coating installation by application medium droplets or the like.
In a development of the present invention, the curved sections of the web run between the first application device and the drying device have a radius of curvature of at least 300 mm. Only if this minimum radius of curvature is observed is it ensured that, in the region of the curved sections of the web run, the centrifugal forces acting on the still moist application layers are so low that application medium droplets are prevented from being thrown off under centrifugal force. This applies in particular at web speeds of more than 1000 m/min.
The coating/drying device, according to the present invention, can advantageously have at least one non-contacting device for stabilizing the moving material web and/or for avoiding or reducing corrugations, in particular transverse corrugations, of the moving material web. For example, at least one coanda effect nozzle arrangement can advantageously be provided. The present invention includes the use of at least one nozzle arrangement for producing an opposing corrugation, in particular a longitudinal corrugation, thereby counteracting a corrugation in particular a transverse corrugation.
Furthermore, the coating/drying device according to one embodiment of the presnent invention can advantageously have at least one device for disrupting and preferably for eliminating or reducing an air boundary layer dragged along by the moving material web. The device should ideally be arranged shortly or immediately upstream of a respective application device, in order that the application of the application medium is not disrupted by the air boundary layer, so that a coating meeting high quality requirements is achieved.
The above-mentioned and other features and advantages of this invention, and the manner of attaining them, will become more apparent and the invention will be better understood by reference to the following description of embodiments of the invention taken in conjunction with the accompanying drawings, wherein:
FIGS. 1 to 4 show schematic illustrations of arrangements and web runs in embodiments of coating/drying devices according to the present invention;
FIGS. 7 to 9 illustrate further schematic illustrations of arrangements and web runs in embodiments of coating/drying devices according to the present invention; and
Corresponding reference characters indicate corresponding parts throughout the several views. The exemplifications set out herein illustrate one preferred embodiment of the invention, in one form, and such exemplifications are not to be construed as limiting the scope of the invention in any manner.
Referring now to the drawings, and more particularly to
As indicated in
Furthermore, application devices 14 and 16 are arranged in sections 12′ and 12″ of the course of material web 12, which run substantially horizontally and they apply application medium to material web 12 substantially from above. In order to permit this arrangement, according to
Finally, a deflection device 22, operating without contact, is also arranged between application device 16 and drying device 10. Deflection device 22 can be formed, for example, by what is known as an “air turn”, which guides material web 12 without contact on a compressed air cushion.
A further embodiment of a coating/drying device according to the present invention, which corresponds substantially to the embodiment according to
Coating/drying device 110 according to
A further embodiment of a coating/drying device according to the present invention, which corresponds substantially to the embodiment according to
In coating/drying device 210 according to
A further embodiment of a coating/drying device according to the present invention, which corresponds substantially to the embodiment according to
Coating/drying device 310 according to
As indicated by double arrows, application devices 414 and 416 can be adjusted vertically. Material web 412 runs between application device 414 or 416 and a respective trough 448 or 450, which collects excess application medium.
After passing under second application device 416, material web 412 is led over an air turn 422 to a drying device operating without contact (not illustrated). For instance, a hot air dryer can be provided. As an alternative or addition to air turn 422, guidance can also be provided by air nozzles 452. An exemplary course of material web 412 through air nozzles 452 is illustrated by dashed line 412′. Air nozzles 452 can be arranged in such a way that a slight corrugation in the moving material web 412 with wave troughs and wave peaks following one another in the running direction or longitudinal direction of the material web is produced. Such corrugation counteracts undesired transverse corrugation of material web 412 with wave peaks and wave troughs following one another in the transverse direction.
With regard to deflection rolls 420, consideration is primarily given to these having a comparatively large diameter, for example larger than 600 mm, in order to avoid throwing off the application medium, also known as the coating color.
As can clearly be seen from
In the arrangement according to
Two air turns 520 act with their guide air on the side of the material web coated by first application device 514. It is possible for the other, not yet coated, side of the material web to be assigned one or more supporting rolls, in order to ensure defined and stable material web guidance. After material web 512 has passed under second application device 516, which is preferably designed as a curtain application device, just like first application device 514, material web 512 runs through air nozzles 552 used for stabilization. Web 512 is then deflected by way of a further air turn 522 into a contactless dryer 518, downstream of which, a further drying device 560 operating with contact in the manner of a normal drying section can be connected.
Of material web 512 fed to the respective coating/drying device, according to
Coating/drying device 610 according to
A further expedient arrangement is shown in
An arrangement very similar to the arrangement of
An indirect application to both sides of web 812, is accomplished with application rolls 860 and 862, which are, in each case, loaded with a coating film by way of curtain applicators 814 and 816, is shown in
Referring once more to components or elements 452, 552 and region X and also to elements 444, 446, 544, 546, 644, 646, 744, 746, 844, 846 and 944, it should be pointed out that, for high-value coating results, the avoidance of corrugations and the achievement of a high stability of the web guidance, and also the avoidance, or at least reduction, of the air boundary layers disrupting the application are of great importance in practice. For the purpose of web stabilization and avoiding disruptive corrugations, the coanda effect air nozzle arrangements already mentioned are advantageously suitable which, by way of generating a vacuum, force controlled web guidance and even out any material web corrugations. The application nozzle arrangements have a plurality of nozzles, which are arranged one after another on different web sides in the running direction and which impart to the material web a corrugation in the running direction in a defined manner, which counteracts damaging corrugations in the transverse direction.
While this invention has been described as having a preferred design, the present invention can be further modified within the spirit and scope of this disclosure. This application is therefore intended to cover any variations, uses, or adaptations of the invention using its general principles. Further, this application is intended to cover such departures from the present disclosure as come within known or customary practice in the art to which this invention pertains and which fall within the limits of the appended claims.
| Number | Date | Country | Kind |
|---|---|---|---|
| 102 28 114.9 | Jun 2002 | DE | national |
| Number | Date | Country | |
|---|---|---|---|
| Parent | PCT/EP03/06479 | Jun 2003 | US |
| Child | 11023940 | Dec 2004 | US |
