Abstract:
Apparatus for paint or lacquer coating of a sheet capable of coiling that has precisely one drive, which is assigned in effect to a second coiling mount, wherein essentially no further means of influencing the running characteristics of the sheet are provided for.

Description:
BACKGROUND 
       [0001]    The invention concerns an apparatus for paint or lacquer coating of a quasi-endless surface element, capable of coiling, according to the preamble of claim  1  or  2  and an appropriate process according to the preamble of claim  11 . 
         [0002]    Quasi-endless coated metal sheets, in particular steel and aluminium sheets, are processed in huge numbers in the automobile industry and also for the manufacture of domestic appliances (so-called “white goods”) and furthermore for the production of aircraft and water vessels and of construction paneling. Steel sheets are primarily metallically bare, galvanized or nickel-plated sheets with thickness values in the range between a few tenths of a millimeter and more than one millimeter. As pre-treatment for later painting or plastic coating, a corrosion protection coating and/or a primer coat is already applied to such sheets on the coil. 
         [0003]    Such coatings are mostly applied in the liquid state, but occasionally also as powder coatings and, after application, must be rationally dried or cross-linked to arrive at a solid coating. To this end, and as is known, sheets are inductively heated to a temperature around or above 250° C., thus also heating up the coating to over 200° C., therefore drying or cross-linking it. 
         [0004]    This process involves very large amounts of energy because it is not primarily the actual processed item, namely the applied coating, that is heated, but the sheet itself, which does not require any heating. By contrast, in certain cases heating of the sheet is even disadvantageous because it is capable of modifying specific physical properties of the sheet that have been adjusted in prior steps through conscientiously coordinated thermal processes, up to here. Incidentally, in view of the very large numbers of tons of coated sheet dried in this way, the energy lost as a result of unnecessary warming of the sheet adds up to considerable amounts in terms of the national economy. 
         [0005]    A further considerable disadvantage of the known process consists of the high realization costs of inductive heating lines. In total, the aforementioned disadvantages lead to a price for sheets processed by the so-called “coil coating” method that is still relatively high today, which is manifesting itself increasingly disadvantageously in view of the increasing cost pressure on suppliers in the automobile and consumer goods industries. 
         [0006]    The known coil coating processes supply high-quality products with a high throughput per unit of time. It has been found, however, that certain surface defects such as fine cracks and slight flaws can occur when recoiling the coated sheet with the hardened coating which, in certain circumstances, can severely impair usefulness during later use. During further processing, segments of strip with such flaws can results in products of impaired quality which, in certain circumstances, even has to be scrapped. 
         [0007]    At an earlier time, the applicant had therefore proposed to realize the drying or cross-linking step in a so-called radiation drier by irradiating the coated surface of the surface element with electromagnetic radiation of a high power density in the range of near infrared, which has its essential active components in the wavelength range between 0.8 and 1.5 μm; cf. DE 101 06 890 A1. A similar process and suitable powder slurries have become known from DE 100 27 444 A1. 
         [0000]    In view of their considerable advantages, such coil coating processes using NIR® driers have in the meantime experienced widespread use in large industrial steel treatment. 
         [0008]    One basic disadvantage of the known large industrial coil coating processes—with inductive or radiation drying—consists of the fact that process control and plant structure are tailored to large throughput volumes. Correspondingly powerful installations are space-consuming and costly and operate efficiently only if considerable use is made of their capacities. With these processes and plants, small orders at a customer&#39;s special request cannot be realized rationally because large volumes of scrap sheets are produced during the start-up phase and until constant process control is achieved and, in turn, when shutting down a plant. Due to the small batch size, that increases product costs, which are high anyway. 
       SUMMARY 
       [0009]    The invention is therefore based on the object of providing an apparatus conforming to its genre and a process conforming to its genre with substantially improved suitability for small orders which, in particular, can also be used directly on the premises of the consumer of the coated sheets. 
         [0010]    In relation to its apparatus aspect, this problem is solved by an apparatus with the characteristics of Claims  1  and  2  and, in relation to its process aspect, by a process with the characteristics of Claim  7 . Expedient enhancements of the invention&#39;s concept are the subject of the pending claims. 
         [0011]    The invention is based on the fundamental idea of using a coil coating apparatus whose structure and operating principle are coordinated to the processing of small orders, in particular on site at the consumer&#39;s premises. Therefore, a compact, also portable in compliance with an essential aspect of the invention, plant is made available that manages without prolonged start-up or shutdown phases (in which no useful product is delivered). 
         [0012]    With such a solution, even small volumes of surface elements in different colours and with different coating materials can be produced at low cost in a comparatively fast sequence of orders, with a low scrap rate and (also due to the relatively low creation costs of the proposed plants) also at low cost. Processing of orders in the order of magnitude of 20 m coil length is as realistic as the attainment of waste coil lengths (throughput up to stabilisation of the process parameters) of 5 m or less. 
         [0013]    In accordance with a first independent aspect of the invention, the compact structure is promoted by the provision of precisely one drive on a coiling mount and the practically complete relinquishment of other means for influencing running properties (web tension regulator, etc.). Provided the system has a coiling mount at the output end, the drive is preferably assigned to it. 
         [0014]    According to a further essential, relatively independent, aspect of the invention, the system is structured as a coherently crane-capable block on one common load-bearing construction. This guarantees fast and easy provision to the consumer of the coated sheets or other surface elements (lattices, networks, etc.). 
         [0015]    The block preferably has outside dimensions that are maximally equal to those of a 30-foot to 50-foot standard container. This ensures a possibility of transport in appropriate standard containers “in one piece”, by road or rail, and space-saving setting up at the place of use. 
         [0016]    The compact structure is essentially enabled by virtue of the fact that the radiation drier has a large number of radiators whose essential active component lies in the range of near infrared or in the UV range and its dimension in the transport direction of the surface elements lies in any case under 5 m, preferably in the range between 500 and 2000 mm, in particular between 700 and 1500 mm. A further advantage (in combination with a suitable mode of operation) is a particularly compact design of a subsequently arranged cooling line, in particular realized as a powerful water cooling line. 
         [0017]    The particularly compact structure of the radiation drier, in turn, is essentially achieved by virtue of the fact that the radiation drier has halogen filament lamps and/or UV medium or high-pressure lamps operated at a radiator temperature of 2900 K or more in an actively water or air-cooled integrated reflector housing. Here, it may be appropriate to suitably connect the water cooling of a solid metal reflector featuring internal cooling fluid channels with the water cooling in the subsequently arranged cooling line. In combination with this—or under certain operating conditions also as an alternative to this—cooling of the reflector and of the radiation sources (or particularly the ends of the lamps) with air is possible. Such an air supply can, in turn, also be designed so that is simultaneously serves to dissipate solvent components of the coating. 
         [0018]    It is of particular advantage if (according to a further relatively independent aspect of the invention) the plant has precisely one media connection for operating energy and media, in particular precisely one main voltage connection and precisely one fresh water connection. Especially in the case of a crane-capable container design, the energy and media connections can be arranged on one container wall, in compliance with the spatial conditions at the intended operating location, but other configurations are naturally also possible. In this connection it is essential that a supply to the various consumption points within the apparatus takes place via one central distributor so that, if possible, only one connection needs to be produced at the operating location. 
         [0019]    The proposed configuration is flexibly adaptable to differing conditions of use and additional or replacement components can be integrated easily in a modular fashion. Thus, for applications in which a fast change of the coating type or colour is required, a second coater can be provided or primer coating units or other pre-treatment units can be provided. Post-treatment units for the coated and dried sheet and/or different types of collecting units can be integrated at the output end. 
         [0020]    The process according to the invention is distinguished by control of the coating and drying step that differs clearly from that of large engineering coil coating processes in terms of the time regime of starting up and stopping of passage of the surface elements: while the coating and drying step in conventional processes does not take effect until the sheet has essentially reached a predetermined nominal speed, in the process according to the invention this already takes place beforehand, in particular automatically when a predetermined fraction of the nominal speed has been reached. 
         [0021]    A preferred process control is distinguished by virtue of the fact that a nominal speed in the range between 3 and 30 m/min, in particular between 5 and 20 m/min, is set. These transport speeds are substantially lower than in the case of industrial installations, but sufficient for the relatively low order volumes to which the solution according to the invention is tailored. The low speeds contribute towards enabling the different (and simplified) process and very low rates of scrapping uncoated or improperly coated sheet. 
         [0022]    According to a preferred variant, paint or lacquer coating and drying are activated within 10 s, preferably within 5 s, after the process has been started. Again, it is advantageous that, in the proposed solution, paint or lacquer coating and drying are activated or deactivated simultaneously and/or no further essential control intervention in the paint or lacquer coating process and drying takes place between activation and deactivation. Whereas, in industrial installations, corresponding control commands are generally issued by qualified and experienced operating personnel, simplified control of the proposed process can also be realised by less-qualified operators, who may also be able to perform other tasks in parallel. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0023]    Advantages and practicalities of the invention otherwise result from the dependent claims and the following description of two preferred variants with reference to the figures. In  FIGS. 1 and 2 , these each show the equivalent sketch of an embodiment of the apparatus conforming to the invention in the form of a longitudinal section. 
       
    
    
     DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS 
       [0024]      FIG. 1  shows a coil coating apparatus  100  that, on a joint carrier plate  101 , has a first, input-end coiling mount  103  for an input-end coil  105  of a plate  106  to be coated, a roller coater  107 , an NIR drier  109 , a water cooling unit  111  and a second, output-end coiling mount  113  for output-end holding of a coil  115  of the coated sheet and a drive (not shown) assigned to the second coil mount  113  for transport of the sheet. In total, the apparatus is portable due to the fact that all components are mounted jointly on the carrier plate  101 . With a dimension l of approximately 10 m between the axes of the first and second coiling mounts  103 ,  113 —which is in particular enabled by a short drier length l T  of the NIR drier  109 —in total the apparatus can be transported completely assembled in a 40-foot standard container by road or rail to its place of use. 
         [0025]      FIG. 1A  schematically shows such a container variant of the apparatus  100 , wherein the components of the apparatus mentioned further above are not designated here and are not explained yet again. The apparatus  100  is housed in a container  117 , of which the floor  117   a , the rear wall  117   b , the top terminating wall (ceiling)  117   c  and a front and rear door  117   d ,  117   e  are shown in the figure. Over a part of the length, the floor or the mounting plate  117   a  is realized as a false floor  117   f  to accommodate media infrastructure. 
         [0026]    On the side pointing towards the operator (in the figure of the front side), observation windows  119   a  or  119   b  are provided in the area of the coater  107  and of the NIR drier  109 . Above the corresponding areas of the apparatus, ingoing and outgoing air treatment units  121   a ,  121   b  are provided which are linked to the atmosphere via ingoing and outgoing air openings (not separately marked). All infrastructure connections can be routed via a central connection unit that is attached outside the container, on its rear wall for example, and which is not recognisable in the figure. Incidentally, an electrical power supply and/or the gas supply for an assigned exhaust air treatment unit, as well as this unit itself, can be provided as additional dock-on units. 
         [0027]      FIG. 2  shows a further compact coil coating system  200  that has a structure similar to the system  100  shown in  FIG. 1 . Coinciding parts are designated with reference numbers based on  FIG. 1  and are not explained yet again here. The essential difference consists of the fact that, here, at the output end there is no (second) coiling mount, but a deflection unit  214  (merely shown symbolically) with subsequent sheet shears  216  and a stacking unit  218  to accommodate sheets cut to size  206 ′. These components are not arranged on the joint carrier plate  201 , but are additionally assigned to the plant on the site. This makes it possible to accommodate the components arranged on the carrier plate  201  even in a 30-foot container, on the basis of the dimensions stated above. 
         [0028]    Vertical expansion of the proposed apparatus is not only possible, as in the variant shown in  FIG. 2 , by including additional units recessed in the floor, but also by means of a two-tier version, which can be realised in practice by placing one container on top of another, each of which contains a part of the overall apparatus, for example in a first contain the input-end coiling mount, a first coater (for example for a primer) and a first drying line and in a second container a second coater (for example for a top coat), an assigned second drying line and an output-end coiling mount or cutting unit with panel deposit, etc. 
         [0029]    Furthermore, it is possible, in a basic configuration of the apparatus, to deliberately provide for additional components to be possibly inserted later, for example an additional UV drier or a mechanical machining unit for the (uncoated or coated) coil. 
         [0030]    It goes without saying that, within the scope of the invention, numerous variations of details of the realisation examples and processes aspects explained above are possible without moving out of the sphere of protection of the invention.