EP1372867B1 - Method for applying a coating agent - Google Patents

Abstract

The coating machine (1) has a main upper chamber (5) above a smaller middle chamber (6) divided into inner (10) and outer (8,9) compartments. There is a bottom chamber (7), which is smaller than the middle chamber. Holes (12-15) in the floor of the upper chamber give access to the middle chamber, and further holes (19-20) and a ventilator (11) give access to the lower chamber. There is a container (18) for the material to be added to the incoming air (16) and there is a pipe (17) for removal of excess air. Both the air pipes are in a removable lid (4) at the top of the large chamber.

Description

The invention relates to a method for applying a coating agent to the surface of a workpiece.

For the purposes of the present invention, a coating agent is to be understood as meaning a wet-chemical coating material, in particular a lacquer.

Paints as such are known in many embodiments from the prior art. They are usually applied in a thin layer on the surface of a workpiece and form by a chemical reaction and / or physical change adhering to the surface of the workpiece solid film, which has a decorative and / or protective function depending on the application. The main components of a paint are usually binders, solvents, pigments, fillers and other additives, such as paint aids. Depending on the nature of the binder, lacquers may contain organic solvents and / or water or be solvent-free.

The application of a paint to the surface of a workpiece is referred to as painting and may depend on the surface of the workpiece, the paint to be applied and the desired properties the later lacquer layer using a variety of methods. For example, by painting with a brush, by spraying with the help of sprayers or by flood, dipping, pouring or rolling. The coating of metal strips or sheets can also be done by coil coating with stoving, in powder coating by electrostatic coating or sintering in the fluidized bed, and finally by the most commonly used in the automotive industry electrophoretic coating.

Smooth lacquer layers can be formed in particular by the dipping method. The thickness of the salmon depends primarily on the viscosity and rheology of the paint and on the extraction speed of the workpiece from the dipping bath. However, it is disadvantageous in the drip area of the workpiece to an unavoidable accumulation of paint, resulting in a generally unwanted thickening of the paint layer in this area.

Furthermore, it should be noted that the entire workpiece is wetted by the dipping process. This is always disadvantageous if not the entire workpiece, but only portions of the same are to be provided with a coating layer.

For the targeted painting of selected workpiece surface areas, in particular the spray process is suitable. In this case, a spray cone is generated, which is directed to the surface to be coated with a mostly predeterminable compressed air pressure. In this way can specifically coated only partial areas of a workpiece surface, ie painted.

Although the spraying method has prevailed in many fields for the abovementioned advantage, and this irrespective of whether a protective or decorative surface coating is to be formed with the coating, the lacquer layers which can be produced by the spraying process also have a strength that is usually considerable. Particularly in comparison with the wavelength of the light perceptible to the human eye, the lacquer layer thicknesses obtainable by conventional methods are very large. This circumstance is disadvantageously noticeable, in particular, in the case of transparent coating systems, because the viewer perceives that the structural change in the workpiece surface caused by a coating application is often perceived as having a high gloss and "greasy" quality. Also, the appearance of orange peel effects can not always be completely avoided. Such effects are also perceived by the viewer as unpleasant and often lead to complaints.

Such methods for applying a coating agent to the surface of a workpiece are known for example from DE 37 27 632, US 4,389,234 and JP 61-249567. DE 37 27 632 describes a method and an apparatus for coating thin-walled or small-sized glass containers. The still-hot glass containers are taken directly from the forming process and placed in a coating tunnel which is open on both sides and in which they are subjected to a turbulent flow of a mixture of vaporized metal compound and air get abandoned. In order to ensure the formation of a complete and uniform coating, it is provided that the glass containers are exposed during the course of the process two oppositely oriented flow paths. To form the mixture of air and vaporized metal compound, a metering system is provided, from which the liquid metal compound is metered continuously into the air guiding chambers of the coating tunnel. From there, the mixture enters the coating tunnel and flows around the glass containers to be coated, forming a coating of colorless, transparent metal on them.

Also in US 4,389,234 glass articles are coated in a coating tunnel. The glass containers to be coated are guided by means of a conveyor belt through a hood forming the coating tunnel. The side walls of the tunnel are provided with a plurality of mutually opposite coating agent-penetrating and suction, so that a guided through the hood glass container from different directions and each can be applied several times with a coating agent, wherein the unused coating agent from the tunnel for another Use is withdrawn. For penetrating the coating agent, a carrier gas, usually air, is provided, into which the coating agent is introduced as vapor or atomized.

JP 61-249567 describes the formation of a closed, very thin coating on the surface of a workpiece. For this purpose, the workpiece is guided in a coating chamber and a supersaturated aerosol atmosphere exposed. For the formation of the aerosol atmosphere, an atomizer is provided, which mixes the originating from a reservoir coating agent finely divided into a pressurized gas stream.

However, all these methods are not suitable to avoid the disadvantages described above.

It is therefore the object of the present invention to provide a method for applying a coating agent to the surface of a workpiece, with which an improved surface structure of the coated workpiece surface is achieved.

The previously derived and indicated object is achieved by a method for applying a coating agent to the surface of a workpiece, in which the coating agent is finely divided mixed into a gas stream, the coating agent-gas mixture is guided in a relative to the surrounding atmosphere sealed volume space and a workpiece arranged within the volume space is surrounded by the coating agent / gas mixture, wherein the coating agent is finely distributed so that particles with a diameter of 10 ^-8 m to 10 ^-6 m are formed.

Advantageous embodiments of the method according to the invention are the subject of the dependent claims.

An essential advantage of this method is that, depending on the particle diameter of the very finely distributed coating agent also provided Such layer thicknesses can be formed, whose thickness is below the wavelength of the light and thus any structural changes or unwanted surface effects are invisible to the human eye and therefore imperceptible. For this purpose, the coating agent to be applied is finely divided into particles having a particle diameter of 10-8 m to 10-6 m. The particles are then mixed into a gas stream, so that an aerosol consisting of carrier gas and coating particles is formed. This is guided in a sealed against the surrounding atmosphere volume space. Within the volume space, the workpiece having the surface to be coated is arranged, which is now exposed to the aerosol atmosphere. Around floating particles of the coating material hit the surface of the workpiece and wet it, so that depending on the density of the coating agent-gas mixture and the residence time of the workpiece within this atmosphere, a closed surface coating is achieved, the layer thickness of the particle diameter of the coating composition accordingly in the few 10 nm range, preferably a few 100 nm range lie. The formation of a closed surface coating can additionally be assisted by an electrical or electrostatic charging of the coating agent particles and / or of the workpiece to be coated.

In contrast to conventional methods, it is thus possible for the first time to apply transparent coating compositions in ambient atmosphere in such thin layer thicknesses that they can no longer be perceived by humans as such. For the people Invisible, the surface properties of workpieces can be changed in a targeted way. For example, surfaces of commodities may be coated with a colorless protective layer so that later cleaning of the article, such as wiping fingerprints, can be much easier and faster. In particular, the surface of black plastic parts, such as the surface of car taps, or the surface of shiny metallic or matte, such as chromed surfaces can be much easier maintained and cleaned due to a seal made by the method according to the invention.

The finest distribution and mixing of the coating agent in the gas stream to form a preferably saturated coating agent atmosphere within the volume space can be done in different ways and depends primarily on the state of matter of the coating agent. Thus, a coating agent-gas mixture according to the invention can be produced, for example, by a mechanical atomization of fine powders, by condensation of vapors when cooled below the dew point or freezing point, by combustion processes or spraying solutions or

Solution mixtures, brines, emulsions or suspensions, wherein the solvents or dispersants evaporate immediately. If the finely divided coating agent particles are solids, then the coating agent / gas mixture, depending on the type of formation, is present either as smoke or as dust. in the Trap of liquid coating agent particles produces mist.

The inventive method is suitable for coating a variety of flat or three-dimensional workpieces. These can be made of plastic, metal, glass, ceramics, fiber products, textiles, polymers, stone, sandstone or concrete. Particularly good results can be achieved with materials which have reactive groups (eg hydroxyl or amino groups) on their surface. These include, for example, glass or ceramic surfaces. Likewise, the process can be used with metals in particular for aluminum, brass and chrome, but is particularly suitable for electroplated surfaces. The adhesion of the coating agent to the surface of the workpiece is improved with increasing surface tension of the workpiece. Examples of coatable with the process according to the invention workpieces are fittings, solar panels, glass covers, facades, decorative screens, display windows, car sheets, printing press plates, metal foils and nozzles.

The workpiece preferably has room temperature, but may also be introduced cooled or heated into the volume space in order to achieve a temperature difference between the workpiece and located in the volume space coating agent.

The inventive method is suitable for use with coating compositions of any composition. Particularly suitable coating compositions are those based on silanes, in particular organosilanes.

Organosilanes are bifunctional silicon compounds which can serve in paints and coatings as adhesion promoters between substrate and coating or as crosslinkers. Organosilanes can also take over the function of a co-binder as oligomers in hybrid coatings. Suitable organosilanes are, in particular, organofunctional silanes and alkylsilanes. These are derived from silicic acid esters, wherein one or two alkoxy groups of the silicic acid ester are replaced by directly bonded alkyl or functionalized alkyl radicals. The organofunctional silanes and alkylsilanes thereby obtain a bifunctionality that allows them to react with organic as well as inorganic materials or to organophilically modify via their alkyl moiety of organic materials. Organosilanes preferably used according to the invention are preferably in the form of a liquid having a low viscosity.

In particular, their reaction behavior is advantageous with respect to the organosilanes, it being possible for the silicon-functional group to hydrolyze in the presence of water or by surface moisture of substrates (eg glass, metal, fillers or pigments). Here, the alkoxy groups are gradually split off to form alcohol and the silane converted into the reactive form, the silanol.

The silanol formed can then be fixed via a chemical bond on the surface of inorganic substrates. The coating compositions which are preferably used in the process according to the invention may contain, in addition to the silanes or organosilanes, further constituents, such as resins or inorganic compounds, such as aluminum oxides (eg A1203) or titanium oxide.

Furthermore, it is possible to modify the organofunctional silanes such that one or more silicon atoms are replaced by metal atoms. As a result, the properties of the layer system to be achieved can be specifically changed and adapted to the respective requirements.

• chemisch inert, abrieb-, kratz- und verschleißfest;
• schmutz-, staub- und wasserabweisend; säure- und laugenbeständig; chemikalienresistent;
• thermisches Aushärten unter 100 C möglich; optisch neutral;
• umweltfreundlich und recyclingfähig;
• gute Haftfähigkeit (chemische Bindung) auf Substraten wie Metall, Kunststoff, Keramik, Stein, Beton und Glas;
• hohe Korrosions- und Verschleißbeständigkeit bei extrem dünnen Schichten (µm-Bereich); für hohe klimatische Beanspruchung geeignet (Kondenswasser, Salzsprühnebel, Industrieatmosphäre, Freibewitterung mit UV-Belastung) ;
• Transparente und einfärbbare Oberflächen;
• Trennfähigkeit bis 70 bar.

By changing the composition of the coating agent, for example, the following properties of the coated workpiece can be achieved:

• chemically inert, abrasion, scratch and wear resistant;
• dirt, dust and water repellent; acid and alkali resistant; resistant to chemicals;
• thermal curing below 100 C possible; optically neutral;
• environmentally friendly and recyclable;
• good adhesion (chemical bonding) on substrates such as metal, plastic, ceramics, stone, concrete and glass;
• high corrosion and wear resistance with extremely thin layers (μm range); suitable for high climatic conditions (condensation, salt spray, industrial atmosphere, outdoor exposure to UV radiation);
• Transparent and dyeable surfaces;
• Separating ability up to 70 bar.

In order to achieve a particularly uniform coating of the workpiece, the choice of the way in which the coating agent-gas mixture is brought into contact with the workpiece, to pay attention to the composition of the coating agent-gas mixture. It has been shown that essentially three coating effects can be observed. On the one hand a condensation effect, in which the aerosol flows around the workpiece and condenses like a mist on the surface of the object. Of the Condensation effect occurs substantially at smaller particle sizes of the coating agent mixed in the carrier gas. Furthermore, there is a gravitational effect, in which especially larger particles are accelerated downwards by the gravitational attraction and coat workpieces, especially from above. Finally, a kinetics effect is observed, in which the particles move through their kinetic energy and hit the surface of the object and adhere to it. Depending on the composition of the coating agent and the spectrum of particle diameters in the coating agent / gas mixture, one of the coating effects comes to the fore.

Thus, it has been shown that, especially in the case of the generation of fog, it is produced with a spectrum of particle sizes that corresponds to a Gaussian curve. In a typical composition of a coating material, the frequency maximum at certain viscosity and temperature is at a droplet diameter of 500 nm. The lower limit is 200 nm, the upper limit is about 2 pm. However, since the droplet mass grows at the third power of the diameter, the frequency peak of the mass spectrum is over 2 μm. The essential mass fraction of the transported coating agent is thus in the relatively few large drops. The gravitational effect is particularly pronounced in such a composition of a coating agent gas mixture.

Therefore, the way in which the coating agent / gas mixture is brought into contact with the workpiece should be matched to the predominant coating effect. This is preferably done by Measures to ensure that each surface section of the workpiece comes into contact with all particles of different diameters. This is done above all by means of measures which bring about a uniform distribution of all particle sizes in the part of the volume space in which the workpiece is located.

With a given embodiment of the volume space, however, measures can alternatively be taken which influence the spectrum of the particle diameter and thus a different coating effect comes to the fore.

In addition to the choice of the viscosity of the coating composition, the spectrum of particle sizes can be influenced in particular by the choice of the temperature and the pressure. Higher temperatures and lower viscosities result in a smaller particle spectrum. This can support the condensation effect. A mean particle diameter based on the number of particles of 250 to 800 nm, in particular 400 to 600 nm, is preferably used or set. The average particle diameter based on the mass of the particles should be 800 nm to 6 μm, especially 1 to 3 μm.

The dominance of a coating effect can be brought about when a temperature gradient between the workpiece and the volume space is set.

This can be generated in a simple manner by heating or cooling the workpiece into the volume space.

Preferably, the coating process is carried out under substantially atmospheric pressure. This leads to a good adhesion of the coating agent to the workpiece.

According to a further feature of the invention, the coating agent-gas mixture is blown into the volume space. This allows the introduction of a pre-mixed and in the composition of the specific individual case coordinated coating agent-gas mixture. In addition, an increased movement of the individual suspended particles can be achieved by blowing, so that sets an overall uniform distribution of the coating agent particles within the volume space. This causes advantageously the formation of a more uniform, d. H. in particular a more uniform thin coating agent layer.

According to a further feature of the invention, the coating agent-gas mixture is circulated within the volume space. Also by this measure, the coating agent-gas mixture is distributed evenly in an advantageous manner in the volume space, so that an equally uniform coating is ensured. In this context, it should be noted that the larger the diameter of the coating agent particles, the stronger their tendency to settle towards the bottom of the volume space. A circulation of the coating agent-gas mixture thus takes place not only as a function of the density of the mixture, but also as a function of the diameter of the particles, wherein the necessity of a circulation increases with increasing particle diameter.

According to a further feature of the invention it is provided that the coating agent-gas mixture is guided in a closed circuit.

Especially for health or environmental reasons, leading in a closed cycle is an advantage. For example, it can be ensured in this way that the coating agent or particles thereof are not unintentionally released into the environment. In addition, cleaning systems can be installed in a simpler manner, which allow both a reprocessing of the coating agent itself, as well as the carrier gas.

According to a further feature of the invention, it is provided that the coating agent / gas mixture is introduced under pressure into the volume space via at least one supply line and the resulting coating agent / gas mixture jet circulates the coating agent / gas mixture within the volume space. The advantage of this type of circulation leads to a very effective, fast and safe application of the coating composition. There is no need for additional costly plant components for recirculation and the volume space in which the coating is carried out is easy to design and clean. It is also possible to influence the circulation and thus the coating via the applied pressure, whereby the coating agent gas mixture is forced out of the feed.

According to a further feature of the invention it is provided that the coating agent-gas mixture jet is directed onto an inner surface of the volume space. As a result, the jet can bring about an advantageous long-range circulation and distribution of the coating agent / gas mixture. If, for example, a sphere is used as the volume space, then the jet can be deflected along the inner surface so that a vortex filling the vortex is formed.

This ensures an optimal coating.

According to a further feature of the invention, it is provided that two coating agent-gas mixture jets flow in the opposite direction. On the one hand, it is possible for the jets to collide with one another and cause strong turbulences, which results in the above-mentioned advantages of circulation during the coating and, secondly, it is possible to produce mixture jets which run parallel to one another and run in opposite directions cause far-reaching turbulence over the entire volume space. By arranging the opposing jets on different sides to the central axis of the volume space, a spacious vortex can be generated which fills the entire volume space. The advantages of the turbulence-related upheaval have already been mentioned in detail.

According to a further feature of the invention, it is provided that the at least one coating agent-gas mixture jet enters the volume space in a direction inclined to the horizontal. This holds advantageous options depending on the shape of the volume space and the workpiece to be coated to determine the circulation of the coating agent-gas mixture. So even areas close to the floor and the ceiling can be supplied with the necessary particle density.

According to a further feature of the invention it is provided that a coating agent-gas mixture jet in a direction inclined to the horizontal upward and a second coating agent-gas mixture jet is introduced in a direction inclined downwards to the horizontal direction. By this alignment of two beams, the entire volume space can be advantageously circulated.

According to a further feature of the invention it is provided that the workpieces are positioned within the volume space by means of a frame. As a result, the workpieces can already be suitably fixed outside the volume space and be positioned with the frame in the volume space. Thus, for the first, a secure positioning and removal of the workpieces from the volume space is ensured and, secondly, a suitable frame design can be selected in order to achieve optimum circulation of the coating agent / gas mixture.

According to a further feature of the invention, it is provided that the workpieces are moved in the volume space, preferably rotated on a frame about one or more axes. In coating processes in which the gravitational effect is in the foreground, this leads to all surfaces of a flat or three-dimensional Workpiece at least once during the coating in an "upward" facing position. Since the gravitational effect of the coating is essentially achieved by the fact that heavy drops gravitational impact from the top of "upward" facing surfaces, the aforementioned movement of the workpieces leads to a uniform coating of all surfaces. In coating processes where the condensation effect is paramount, no movement is required. Nevertheless, a movement of the workpiece can also be provided in these methods.

According to a further feature of the invention, it is provided to set the temperature of the coating agent to a temperature of 15 to 23 C. This leads to an intensification of the gravitational effect, which is particularly advantageous when the workpiece is moved in the volume space according to the manner described immediately above.

Alternatively, it is provided that the temperature of the coating agent is adjusted to 22 to 40 C, preferably 35 to 40 C. This reduces the particle size of the coating composition and supports the condensation effect. Thus, even in volume spaces in which the workpieces are not moved, they are well coated.

According to a further feature of the invention, it is provided that the coating agent / gas mixture is conveyed as a function of a predefinable function via a supply line into the volume space and after flowing through the volume space via an exhaust gas line is sucked off. In this way, a precise control or regulation of the mixture atmosphere is made possible within the volume space and so can be done if necessary, a Nachförderung or upstream suction. A decisive decision criterion here is the density of the coating agent-gas mixture.

According to a further feature of the invention, the coating agent-gas mixture is filtered after aspiration from the volume space. This ensures that particles do not enter the environment unintentionally. Depending on the particular application, an activated carbon filter is preferred.

According to a further feature of the invention, the density of the coating agent-gas mixture is detected in the volume space and readjusted to set a predeterminable value in case of need. Maintaining a predetermined density is of crucial importance for the coating quality achievable with the method according to the invention, in that the mixture density, which is in a function ratio relative to the residence time of the workpiece in the volume space, has a decisive influence on the layer thickness formed per unit time. Although this dependence can be varied by additional circulation motions of the coating agent / gas mixture in the volume space, in particular the density of the mixture is a preferred measure for determining how many coating agent particles per volume of part are contained in the gas. Preferably, the density of the coating agent-gas mixture is detected optically. This type of capture is easy to perform and reliable over.

According to a further feature of the invention, the coating agent is mixed in liquid and / or solid form in the gas stream. As stated above, depending on the nature of the formation of the coating agent gas mixture, either smoke or dust is present; in the case of liquid coating agent particles, mist is present.

To form the coating agent / gas mixture, according to a further advantageous proposal of the invention, an inert gas, preferably nitrogen, is used. In particular, the sensitivity of some coating agents to, for example, moisture contained in the ambient air can thus be taken into account and unwanted reactions can thus be prevented. Nor can this form explosive mixtures. But even dry air is used as a coating agent-gas mixture, if the coating chamber is carried out expolsionssicher.

In addition to the aforementioned transparent coating systems, other coating compositions can be processed and discharged onto the surface of a workpiece with the inventive method, but it is crucial that the respective coating agent can be distributed so finely that particles with a particle diameter of 10-8 m to 10-s m be present, so that, as described above, an aerosol can be formed with nanocomposites.

Fig. 1:

eine schematische Seitenansicht einer erfindungsgemäßen Vorrichtung zur Durchführung des Verfahrens mit einer Umwälzeinrichtung,

Fig.2:

eine perspektivische Darstellung einer erfindungsgemäßen Vorrichtung zur Durchführung des Verfahrens mit zwei Zuführungsleitungen, die ohne gesonderter Umwälzeinrichtung arbeitet,

Fig. 3:

eine perspektivische Darstellung einer erfindungsgemäßen Vorrichtung zur Durchführung des Verfahrens mit einer Drehvorrichtung für ein Gestell zur Aufnahme der Werkstücke.

Further features and advantages of the invention will become apparent from the description with reference to FIGS. These show:

Fig. 1:

a schematic side view of an apparatus according to the invention for carrying out the method with a circulating device,

Figure 2:

a perspective view of an apparatus according to the invention for carrying out the method with two supply lines, which operates without separate circulation device,

3:

a perspective view of a device according to the invention for carrying out the method with a rotating device for a frame for receiving the workpieces.

Fig. 1 shows a limited by side walls 2, a bottom 3 and a lid 4 volume space 1. The volume space 1 is sealed against the surrounding atmosphere.

The volume space is subdivided into a coating space 5, a first chamber 6 and a second chamber 7. The coating space 5 and the first chamber 6 and the first chamber 6 and the second chamber 7 are in each case fluidically connected to one another. The first chamber 6 is in turn subdivided into two outer regions 8 and 9 and a middle region 10.

The central region 10 of the first chamber 6 is connected via a fan 11 with the second chamber 7 in fluid communication. In addition, slit-like openings 12 and 13 between the processing space 5 and the first chamber 6 and 19 and 20 between the first and the second chamber 6 and 7 intended. In addition, apertures 14 and 15 are present between the coating chamber 5 and the central region 10 of the first chamber 6. The fan 11 blows from the second chamber 7 in the first chamber 6 and that in the central region 10 of the first chamber 6. This creates a negative pressure in the second chamber 7. As a result thereof is through the openings 12,13,19 and 20 sucked between the processing chamber 5 and the second chamber 7 located in the processing chamber 5 coating agent atmosphere. Via the fan 11, the sucked atmosphere then passes into the central region 10 of the second chamber 6. The openings 12 and 13 are arranged offset in comparison to the apertures 14 and 15, so that there is not a simple blowing through the sucked atmosphere, but rather comes to a cross-mixing.

For the supply or removal of a coating agent-gas mixture, a corresponding supply line 16 and a discharge line 17 is provided. A fluidically connected to the supply line reservoir for the coating agent-gas mixture is designated 18.

From this reservoir 18, the desired amount of coating agent-gas mixture can be dispensed as needed.

The process according to the invention provides finely divided coating compositions which are conveyed into the volume space 1 by means of a gas stream and, in the coating space 5, preferably a workpiece immersed in the atmosphere prevailing there umspülen. In this case, a layer thickness is formed on the workpiece, which lies in its thickness below the wavelength of the visible light. Thus, any structural changes or unwanted surface effects are invisible to the human eye and thus imperceptible. The supply line 16 and the apertures 14 and 15 are aligned so that the coating agent-gas mixture jets prefer a wide circulation in the coating chamber 5.

The coating agent to be applied is finely divided into particles having a particle diameter of from 103 m to 10-6 M. The particles are then mixed into a gas stream, so that an aerosol consisting of carrier gas and coating particles is formed. This is conducted in the volume space 1 sealed relative to the surrounding atmosphere. Floating particles of the coating agent strike the surface of the workpiece arranged within the coating space 5 and not shown in this figure, and wet it, so that a closed surface coating is achieved depending on the density of the coating agent / gas mixture and the residence time of the workpiece within this atmosphere is whose layer thickness of the particle diameter of the coating agent are correspondingly in the nm range.

2 shows a volume space 21 bounded by a side wall 23, a bottom 22 and a cover 24. The volume space 21 is tightly sealed against the atmosphere surrounding it. In this embodiment, the entire volume space 21 is simultaneously the coating space.

In the side walls 23, two supply lines 25 and 26 are mounted, is flowed through by the coating agent-gas mixture. The supply lines 25 and 26 are arranged so that they are on the opposite side. The feed line 26 is inclined downwardly to the horizontal and faces the front part of the side wall 23. The feed line 25 is inclined upwardly to the horizontal and faces the rear part of the side wall 23. The feed line 26 is located slightly higher in the side wall 23 than the supply line 25. As a result, the supply lines 25 and 26 are aligned so that the emerging from them coating agent-gas mixture jets are oriented in opposite directions and in the volume space a wide circulation is achieved. Because of the orientation of the supply lines 25 and 26 on the side wall 23 ensures that the exiting rays are deflected and create a spacious vortex along the side wall 23 about the vertical center axis of the volume space 21 around.

A fluidically connected to the supply lines 25 and 26 reservoir for the coating agent-gas mixture can deliver the desired amount of coating agent-gas mixture as needed. The coating agent-gas mixture is pressed under pressure into the volume space 21, in order to have the appropriate speed, which ensures sufficient circulation of the coating agent-gas mixture.

The lid 24 of the volume space 21 is configured as a bell, in which a discharge line 27 is connected, in which there is a valve 28 for controlling the exiting coating agent-gas mixture. Within the volume space 21 are racks and support 29 for the positioning of the workpieces to be coated. The racks and carrier 29 are mounted in the lid 24.

Fig. 3 shows a volume space 1 with a feed line 30 and a discharge line 31 and a cover, not shown, for opening the volume space 1. In the volume space 1, a frame 32 is arranged, the receptacles 33 for workpieces 34 has. The receptacles 33 are arranged on mounting rods 35 which are mounted on turntables 36. At least one turntable 36 and possibly the mounting rods 35 are connected to a rotating device, not shown.

By the rotating device, the turntable 36 and the mounting rods 35 are rotated in the direction indicated by arrows in the drawing directions. Thereby, the workpieces 34 are rotated in the volume space 1, so that a good coating of the workpiece with coating agent, which is supplied to the volume space 1 via the feed line 30 as a coating agent-gas mixture takes place.

In the volume space 1, an atmospheric pressure is maintained by the volume space 1 via the discharge line 31 coating agent-gas mixture is withdrawn in an appropriate amount.

List of numbers Volume space 2 Sidewall 3 Floor 4 Cover 5 Coating space 6 First chamber 7 Second chamber 8 outer region 9 outer region 10 middle region 11 ventilator 12 breakthrough 13 breakthrough 14 breakthrough 15 breakthrough 16 feed line 17 removal line 18 reservoir 19 breakthrough 20 breakthrough 21 volume space 22 bottom 23 side wall 24 cover 25 feed line 26 feed line 27 discharge line 28 valve 29 frame 30 feed line 31 discharge line 32 frame 33 receptacle 34 workpiece 35 mounting rod 36 turntable

Claims (20)

1. A method for applying a coating medium to the surface of a workpiece wherein the coating medium is mixed, finely distributed, into a flow of gas, the coating medium/gas mixture is conveyed into a volumetric space sealed off from the surrounding atmosphere, and a workpiece disposed within the volumetric space is flushed by the coating medium/gas mixture, the coating medium being finely distributed such that particles with a diameter of 10^-8 m to 10^-6 m are formed.
2. The method according to Claim 1, characterised in that the coating medium/gas mixture is blown into the volumetric space.
3. The method according to either of Claims 1 or 2, characterised in that the coating medium/gas mixture is distributed evenly in the volumetric space.
4. The method according to any of Claims 1 to 3, characterised in that the coating medium/gas mixture is circulated within the volumetric space.
5. The method according to any of Claims 1 to 4, characterised in that the coating medium/gas mixture is conveyed in a closed circuit.
6. The method according to any of Claims 1 to 5, characterised in that the coating medium/gas mixture is introduced via at least one supply line under pressure into the volumetric space, and the resulting jet of coating medium/gas mixture circulates the coating medium/gas mixture within the volumetric space.
7. The method according to any of Claims 1 to 6, characterised in that the jet of coating medium/gas mixture is directed towards an inner surface of the volumetric space.
8. The method according to any of Claims 1 to 7, characterised in that two jets of coating medium/gas mixture flow in opposite directions.
9. The method according to any of Claims 1 to 8, characterised in that the at least one jet of coating medium/gas mixture passes into the volumetric space in a direction inclined with respect to the horizontal.
10. The method according to any of Claims 1 to 9, characterised in that a jet of coating medium/gas mixture is introduced in a direction upwardly inclined with respect to the horizontal, and a second jet of coating medium/gas mixture is introduced in a direction downwardly inclined with respect to the horizontal.
11. The method according to any of Claims 1 to 10, characterised in that the workpieces within the volumetric space are positioned by means of a stand.
12. The method according to any of Claims 1 to 11, characterised in that the workpiece disposed in the volumetric space is moved within the volumetric space.
13. The method according to Claim 12, characterised in that the workpiece is rotated by means of the stand.
14. The method according to any of Claims 1 to 13, characterised in that the coating medium/gas mixture is conveyed into the volumetric space dependent upon a predeterminable function via a supply line, and after it has flowed through the volumetric space, is extracted via an exhaust gas line.
15. The method according to any of Claims 1 to 14, characterised in that the coating medium/gas mixture is filtered after extraction from the volumetric space.
16. The method according to any of Claims 1 to 15, characterised in that the density of the coating medium/gas mixture is recorded in the volumetric space and readjusted to set a predeterminable value if so required.
17. The method according to any of Claims 1 to 16, characterised in that the density of the coating medium/gas mixture is optically detected.
18. The method according to any of Claims 1 to 17, characterised in that the coating medium is mixed into the gas flow in liquid and/or solid form.
19. The method according to any of Claims 1 to 18, characterised in that an inert gas is used to form the coating medium/gas mixture.
20. The method according to any of Claims 1 to 19, characterised in that nitrogen is used to form the coating medium/gas mixture.

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