EP2802421A1

EP2802421A1 - Paint-conveying, metering and mixing apparatus for spray guns

Info

Publication number: EP2802421A1
Application number: EP13700179.8A
Authority: EP
Inventors: Joachim VOSSKUHL; Boris PETERS; Sibylle SCHÖPS; Monika TIGGEMANN; Werner-Alfons Jung; Andreas Bauder; Robert Engel; Wolfgang HAIP
Original assignee: BASF Coatings GmbH
Current assignee: BASF Coatings GmbH
Priority date: 2012-01-13
Filing date: 2013-01-11
Publication date: 2014-11-19
Anticipated expiration: 2033-01-11
Also published as: EP2802421B1; WO2013104771A1; US20150036454A1; ES2631187T3

Abstract

The invention relates to an apparatus for conveying, metering and mixing liquid paint components, comprising (a) a paint-feeding apparatus (A), which comprises two or more paint-supply containers (1) each with at least one outlet opening (14, 15) for different paint components which are to be mixed with one another; or comprises one paint-supply container (1) comprising two or more chambers (11, 12) for different paint components which are to be mixed with one another, wherein each chamber has at least one outlet opening (14, 15), (b) a metering apparatus (B), which is arranged downstream of the paint-feeding apparatus (A) and has a number of inlet openings (21, 22) for the paint components which corresponds to the number of outlet openings (14, 15) of the paint-supply containers or of the paint-supply container, wherein the metering apparatus is configured such that the volume flows of mixable paint components which enter via the inlet openings (21, 22) are forcibly conveyed separately from one another via rotating conveying devices (251/252, 261/262) serving as metering subassemblies, wherein the conveying devices are connected to one another such that their rotational speeds are fixed in relation to one another, and wherein the metering apparatus (B) have separate exit openings (23, 24) for the now metered volume flows of paint components, and (c) a static mixing apparatus (C), which is arranged downstream of the metering apparatus (B) and has a number of entry openings (31, 32) for the metered volume flows which corresponds to the number of exit openings (23, 24) of the metering apparatus, and the discharge of said mixing apparatus being designed such that it can be connected to a paint-spray gun. The invention also relates to a method for conveying, metering and mixing paint components using the apparatus according to the invention, to a metering apparatus and to a method for coating a substrate using the apparatus according to the invention in combination with a paint-spray gun.

Description

Paint delivery, metering and mixing device for paint spray guns

The present invention relates to a combined paint delivery, paint dosing and paint mixing device for spray guns and a spray painting process using such a paint delivery device.

Spray painting without electrostatic paint charging are widely used in industrial and artisanal paint shops. Above all, the processes are distinguished from other painting methods in that they can be used manually, have high flexibility with regard to the shape, size and materials of the objects to be painted, as well as the choice of paint and the paint change, are mobile in use and entail relatively low investment costs ( H. Kittel, "Textbook of Paints and Coatings", Second Edition, Volume 9, pp. 26-40, S. Hirzel Verlag Stuttgart Leipzig, 2004).

The spray painting processes can be distinguished essentially in compressed air spraying in the high pressure or low pressure method on the one hand, and airless spraying with or without air assistance.

As the first spray painting process, pneumatic atomization or compressed air spraying was developed around 1900. Even today, compressed air atomization is the most frequently used in industry and trade. When high-pressure spraying, also referred to as conventional spraying or pneumatic spraying, is usually worked with an air pressure of about 2 to 7 bar, while the low-pressure spraying, as HVLP spraying ("High Volume, Low Pressure" syringes or

Syringes with high injection volume flow and low pressure), is usually worked with an air pressure of 0.2 to 0.7 bar (H.Kittel, ibid).

At the atomizing head, the compressed air flows from an annular opening which is formed by a central bore in the air cap and the paint nozzle arranged therein. Further air jets from different air cap holes serve to regulate the jet shape and aid atomization. Due to the compressed air flowing out at high velocity, a negative pressure area is created directly at the paint nozzle mouth, especially in the case of the pressureless air Paint supply from a so-called suction cup the Lackausfluss supported by its suction (H. Kittel, ibid).

In addition to the promotion of the paint material from a suction cup is also the possibility of the paint material depending on quantity requirements and viscosity

Conveying systems such as flow cups, pressure vessels or recirculation systems

Supply spray gun nozzle (Figures 1A-D). In Figure 1A, the paint supply is represented by Saugbechersystem, it takes place as shown above by the

Suction effect of the spray air. Typical cup contents are volumes up to about one liter. In Figure 1 B, a flow cup system is shown, wherein the paint supply takes place both by the suction effect of the spray air, as well as supported by the Lack- Gefälledruck. Also in this paint delivery system cup volumes of about one liter are usually not exceeded. Less suitable for mobile use are paint systems as the printing system (Figure 1 C) and the circulation system (Figure 1 D). In the printing system, the paint supply from a pressure tank by support with a pressure of 0.5 to 4 bar (more commonly

Tank capacity 1 to 250 liters). In the circulation system, the paint supply is carried out by piston or turbine pumps, the circulation system is typically useful only with a daily consumption of more than 100 liters of paint (H. Kittel, ibid).

Particularly in low-pressure spraying, the suction effect due to the negative pressure at the paint nozzle orifice of a so-called HVLP spray gun is lower than in high-pressure spraying, which is why support of the suction effect by the paint gradient pressure is desired, especially in the low pressure range. It is therefore recommended when processing small amounts of paint in low-pressure spraying with a

Flow cup system to work as a paint delivery system.

Two-component coating (2K coating) are mainly due to their limited pot life (pot life) with

Spraying process processed. In this case, the dosage of stock and hardener is the central problem. For small series and individual parts, in particular the refinish area, such as the automotive refinish area, the 2K material is usually mixed manually in the specified ratio and as one One component material sprayed. In practice, this means that both the dosage and the mixture of components before filling a

Flow cup or suction cup or in the flow cup or suction cup itself and thus also the quality and homogeneity of the mixture depends strongly on the manual skills of the painter. Unused material must be discarded after the pot life has expired. On the other hand, a fast drying and curing behavior of the paint film is desired, which is why curing catalysts are often incorporated into the base paint and / or hardener of the 2K or multi-component mixture.

Therefore, especially when using 2K or multicomponent coating compositions, there is the desire for a long processing or pot life, but at the same time improved drying and faster

Hardness development of the sprayed paint film.

In order to obtain the best possible appearance (appearance) of the cured lacquer film as well as reproducible qualities, it is absolutely necessary to produce as homogeneous as possible consistently high-quality compositions of base lacquer and hardener, which have consistent properties over the entire period of application, which is precisely the case with premixed 2K Systems are not always the case, for example, if a short pot life causes the first sprayed material due to a not yet advanced reaction of the

Ingredients has a low viscosity, while the later sprayed material residues already partially contain viscosity-increasing crosslinking products.

In the production of large quantities, with short pot lives and high

High quality dosing and mixing systems are used in industry to meet tolerance limits of dosing accuracy of +/- 5% hardener volume in relation to the base varnish quantity. Further developments aim at pulsation-free dosing and low system wear, for example through the use of diaphragm dosing devices. For mixing static or dynamic systems are used with driven mixing units. For very short pot lives also special pistols are used, in which base varnish and hardener are discharged from separate nozzles and mix the resulting droplets in the spray (H.Kittel, ibid).

Especially in small paint shops, however, there is a need for much less expensive conveyor, metering and mixing devices. In particular, it should not be necessary to use the abovementioned special pistols or

highly specialized dosing and mixing units. The simplicity of use of suction cups or fluid cups, especially of the latter should be preserved. Pumping, dosing and mixing should only be achieved by the varnish pressure, the suction effect of the spray produced by the varnish

Negative pressure and optionally applied to the flow cup pressure. Another external drive of delivery, metering or mixing should not be required. In particular, no drive by pumps and the like should be necessary. Nevertheless, an almost independent of the pot life processability should be ensured, while homogenous mixing of the components, before this nozzle of the spray gun

preferably reach the spray gun itself. The resulting paint films should have good drying and rapid hardness development and lead to cured films with good appearance.

WO 93/13872 A1 describes a method for applying a

A multi-component refinish coating composition wherein at least two paint components are held in separate containers and at least one component is supplied under pressure to a kinetic dosing system comprising two piston-mounted double-acting cylinders with cylinder rods. The metered components are fed to a mixer, which opens into a paint spray gun. The structure of the metering device is rather complex and necessarily requires the admission of at least one paint reservoir with compressed air.

The above objects have been surprisingly achieved by the inventors of the present invention by providing a special apparatus for

Dissolved promotion, dosage and mixing of liquid paint components, which does not have the disadvantages of the prior art. The device according to the invention has the following device units:

(A) a paint supply device, the

i. two or more paint reservoir having at least one outlet opening for different paint components to be mixed together; or

ii. a paint reservoir comprising two or more chambers for different paint components to be mixed together, each chamber having at least one outlet port,

(b) a metering device, which is connected downstream of the paint supply device and has a number of outlet openings of the paint reservoir or the paint reservoir corresponding number of inlet openings for the paint components, wherein the metering device is designed so that the entering via the inlet openings flow rates of the paint components to be mixed together separated from each other via serving as dosing, rotating conveyors are positively conveyed, the conveyors are connected together so that their speeds are in fixed proportions to each other, and wherein the metering device has separate outlet openings for the now metered volume flows of the paint components, and

(c) a static mixing device, which is connected downstream of the metering device and which has a number of outlet openings of the metering device corresponding number of inlet openings for the metered volume flows, and whose output is designed so that this with a

Paint spray gun can be connected.

The term paint reservoir includes, among other embodiments such as cups preferably gravity cup, disposable cartridges or bags and the like.

If the paint reservoir has two or more chambers, then these chambers can have any shape and be arranged as desired with respect to each other. For example, the chambers can be cup-shaped

Paint reservoir simply by a plate-shaped partition from each other be separated (see, for example, Figure 2). However, it is also possible a concentric arrangement of the chambers. In the latter case, the paint component of the inner chamber then has to be conveyed through the wall of the outer chamber by means of a type of injector outlet, so that separate outlet openings for the paint components are retained and thus a separate metering is made possible. Such a concentric arrangement allows a simpler

Screw the Lackzuführvorrichtung with the Lackdosiervorrichtung.

Preferably, the device unit comprises (a) i. two paint reservoirs for two different paint components or ii. a paint reservoir with two separate chambers for two different paint components, in particular in the case i. a paint reservoir for a stem paint and a second

Paint reservoir for a hardener or in case ii. one

Paint reservoir with a first chamber for a parent lacquer and a second chamber for a hardener. In the latter embodiment has the

Paint reservoir two outlet openings, one for the master paint and one for the hardener. The metering device has in this embodiment

corresponding to two inlet openings, one for the base lacquer and one for the hardener, as well as two outlet openings for the metered volume flows.

For all embodiments, the volume flows of the components, such as, for example, the master varnish and hardener, are supplied separately from one another to a rotating conveyor. In a special

Embodiment, each individual rotating conveyor is designed so that it consists of two intermeshing wheels. For each volume flow there thus exists in each case a single rotating conveyor, comprising a pair of wheels. The intermeshing wheels of the wheel pair are preferably gearwheels, which may be either circular or oval, or paddle wheels. Particularly preferred are Ovalradpaare. The

Wheels of the individual conveyors are interconnected so that their speeds are in fixed proportions. This is done, for example, by fastening at least one of the two intermeshing wheels of a conveyor, each with one of the two wheels of the other conveyors on one and the same shaft or axis. The interconnected wheels of the conveyors thus act synchronously dependent on each other, while the respective second wheel of the respective

Pair of wheels can be stored freely, as this taken over the first synchronized wheel, that is driven. This type of drive is called

Forced conveying is and is essential in order to compensate for the usually present viscosity differences of the various components. The wheel pairs are designed in terms of their size so that they are each promoted to be metered flow rates. The spatial separation of the wheel pairs can be realized for example by partitions in the metering device. The separation of the flow rates prevents premature mixing of the various components in the conveyors.

Another possibility of forced delivery can be realized, for example, when using paddle wheels. In such a case it is not absolutely necessary to use two pairs of wheels. Each volumetric flow can in this case be conveyed, for example, by means of just one impeller, with the impellers of the conveyors being connected to one another in such a way that their rotational speeds are in fixed relationships with one another. This can also be done via a common synchronizing axis or shaft. The volumes delivered can be here, for example, by the capacity of the blades of the

Dosing paddle wheels.

The varnish pressure in the paint reservoirs or in the

Paint reservoir and the suction effect of the spray gun alone is not enough to set the gear pairs in motion or to keep going, so the

Paint reservoir are pressurized with compressed air. In such a case, the paint reservoir is closed, for example, with a pressure-tight lid, which has a compressed air inlet opening, which can be acted upon by compressed air. An external drive of the wheel pairs is neither intended nor desired.

In this respect, the metering device is a completely closed unit and only via the inlet openings with the paint reservoirs or the paint reservoir or via the outlet opening (s) with the static mixer connected. This construction of the metering device is low maintenance and energy efficient.

If the promotion of the paint components alone on the paint slope pressure and the suction effect of the spray gun, the paint reservoir or the paint reservoir can be closed with a vented lid. In a preferred embodiment, the paint delivery is carried out, however, by additional loading of the paint components with compressed air, which from the

Lackvorratsbehältern or the paint reservoir are pressed by the compressed air in the metering device. In such a case, too

Lackvorratsbehälter or the paint reservoir is a completely closed unit, which has only at least one inlet opening for compressed air and the outlet openings to the metering device.

The same applies to the mixing device, which also represents a completely closed unit, which is connected only via the inlet openings with the metering device and the outlet opening with the spray gun. Connected to each other can also mean that the mixing device is partially / completely integrated into the spray gun body.

The three device units (paint supply device, metering device, static mixing device) can be connected to one another, for example, via pressure-tight threads or welded or glued together. To be at a

For example, to ensure bolting tight seals, for example

Sealing rings and the like are used, as known to the average person skilled in the art.

Figure 2 describes the basic structure of a particular embodiment of the invention for the use of a 2K system using two

different paint components. The particular shown in Figure 2

Embodiment of a device according to the invention for conveying, dosing and mixing of liquid paint components comprises a paint supply device (A), which comprises a paint reservoir (1), in turn, two separated by a partition wall (13) chambers (1 1 and 12) for different together comprising mixing liquid paint components, wherein the first chamber (1 1) has an outlet opening (14) and the second chamber (12) has an outlet opening (15). The paint reservoir (1) has in this embodiment, a closable lid (6) via which through an opening (5) compressed air can be applied. Furthermore, the particular embodiment of the

2 according to the invention a metering device (B or 2) with two inlet openings (21 and 22) for the components to be metered and mixed. The metering device is - as already described in detail above - designed so that the over the two inlet openings (21 and 22) entering the flow rates of the paint components to be mixed with each other are conveyed separately via serving as dosing, rotating conveyors. The conveyors are connected to each other so that their speeds are in fixed proportions to each other. The metered volume flows of the paint components are then on the

Outlet openings (23 and 24) of the subsequent static mixing device (C or 3) supplied. The static mixer has two

Inlet openings (31 and 32) and an outlet opening (4) for fixing the device to the paint spray gun. The static mixing device preferably comprises one or more so-called mixer rods (33). The

Mixer rods / elements can be installed vertically, horizontally or in any other way, but they must ensure sufficient mixing of the components.

In Figure 3, an embodiment of a metering device (B or 2) is described in detail, in which each rotating conveyor has a pair of wheels (251/252 or 261/262) and at least one wheel (251) of the pair of wheels (251/252) with the corresponding wheel (261) of the adjacent one

Conveyer located pair of wheels (261/262) via a common axis (27) is connected so that their speeds are in fixed proportions to each other. The axis (27) thus forces a synchronized rotation of the wheels 251 and 261, whereby a positive promotion of the volume flows takes place. The respective second wheel of the two pairs of wheels, this is wheel 252 with respect to wheel 251 or wheel 262 with respect to wheel 261, can be mounted on its own axis (281 or 282) are stored. These second wheels (252, 262) are driven by the rotation of the first wheels (251, 261).

In any case, the materials of the three device units are chosen so that they are inert to the paint components to be mixed and meet the mechanical stresses. For weight reasons are particularly inert, abrasion-resistant plastics, which are resistant to the coating components such as solvents, hardeners, etc., such as Teflon, polyoxymethylene, polyphenylsulfide, polypropylene, polyamide, polyetheretherketone or

Polyaryletherketone. When using flammable or explosion-prone products, dissipative materials must be selected to prevent electrostatic charging. In the case of plastics, dissipative plastics with a resistance of less than 10 ⁶ ohms are to be used. But also the production of

Device units made of metallic materials is conceivable, albeit more costly and less advantageous in particular because of the higher weight during manual operation of the spray gun.

In a particular embodiment of the paint reservoir, the two or more chambers are separated by partitions (see Figure 2). However, it is also possible to realize the two or more chambers so that they are inserted in the form of bags or the like in the paint reservoir and the openings of the bag with the outlet openings of the paint reservoir

are connected. In such a case, a separation over, for example, rigid partitions is not necessary. The volumes of the chambers are advantageously chosen to meet the needs of the components in the final mixture.

Gear pairs such as oval wheel pairs are available, inter alia, from Bopp & Reuther under the trade name "Miniflow 015." The desired ratio of the volume flows of the paint components is preferably adjusted via a width adjustment of the gears or oval wheels., However, the ratio of the volume flows of the paint components can also over other parameters such as wheel diameter or, in the case of coupling via a gearbox, speed ratios can be defined a regulation of the volume flows, for example, take place over the depth of the blades.

In a particular embodiment, the static mixing device consists of a mixing tube with fixed internals. Preferably, so-called mixer rods can be used. Very particularly preferred mixer bars are available, for example, from the company Fluitec Georg AG (Neftenbach, Switzerland) under the name CSE-X® mixer.

As spray guns in principle all spray guns are suitable, which are used in compressed air spraying. The connection of the static mixing device with the spray gun is straightforward and can be done with all common compounds, preferably by a screw thread or quick couplings or dovetail joints. Paint spray guns are available, for example, from Sata GmbH & Co. KG (Kornwestheim, Germany) under the name SATAjet®, as HVLP or RP spray guns.

All components and materials are chosen by the average person skilled in the art so that they are designed for the occurring pressures.

In principle, the individual device units can also be heated externally. However, this is usually not intended.

An essential part of the device according to the invention is a

Metering device that has two or more inlet ports for mixing

Has components, wherein the metering device is designed so that the incoming via the inlet openings flow rates of the paint components to be mixed with each other are conveyed separately via serving as dosing, rotating conveyors, wherein the

Conveyors are interconnected so that their speeds are in fixed proportions to each other, and wherein the metering device has separate outlet openings for the now metered volume flows of the paint components. This metering device is also referred to as metering device according to the invention. The present invention also relates to a method for conveying, metering and mixing of two or more paint components, which is derived from the

Inventive device and / or of the invention

Dosage device makes use.

Furthermore, the present invention relates to a method for coating substrates with 2K or multi-component coating compositions using the device according to the invention in combination with a paint spray gun. The coating process according to the invention is particularly advantageously carried out purely manually. In particular, the inventive method for coating using small amounts of paint is suitable. Preferably, the process is carried out as a HVLP spraying process. Most preferably, it is used in automotive refinish. However, the aforementioned method can also in the context of an OEM OEM, especially in the

so-called assembly repair can be used.

If the process is carried out as HVLP spraying method, then the

Atomizing pressure usually 1, 5 to 2 bar. In the case of RP guns, work is usually carried out at an atomization pressure of 1.5 to 3 bar. In order to support the paint promotion of, or can the paint reservoir with

Compressed air can be applied, the overpressure can vary depending on the

Lackviskosität and the discharge amount can be adjusted.

If two components are used, one component is usually the so-called base coat, the second component is the hardener. In the masterbatches are preferably hydroxy-functional polymers such as polyhydroxy-functional poly (meth) acrylates, polyester polyols, polyether polyols, polyurethane polyols or mixed polyester / polyether polyols used. Polythiols, for example, can be used. In the

Hardener components are usually polyisocyanates such as

Hexamethylene diisocyanate, tolylene diisocyanate, isophorone diisocyanate or

Diphenylmethane diisocyanate or the dimers, trimers and polymers of

aforementioned isocyanates, and / or aminoplast resins such as Melamine resins, used. Also usable are epoxy systems, both conventional and aqueous. Of course, it is also possible to use systems which only become reactive at atmospheric humidity (eg aldimines, silanes). In general, however, parent lacquer and hardener have compounds with complementary functional groups. That is, groups that react with each other after mixing the two components. For example, the following complementary groups may be mentioned: amine / isocyanate, hydroxy / isocyanate, thiocyanate, amine / epoxy / isocyanate, amine / epoxy resin, epoxy / anhydride, amine / anhydride , Anhydride / hydroxy or hydroxy / isocyanate / amine groups. Usually, base lacquer and hardener react after application at temperatures of 0 to 100 ° C, preferably 10 to 80 ° C, that is below

Refinishing conditions usual conditions.

In the process according to the invention, it is also possible to select those masterbatch-hardener combinations which, in the conventional procedure of the

Premix the components before filling the paint reservoir, too short pot life. Even with such systems excellent coatings are obtained, which are characterized by short drying and curing times and an excellent appearance.

In the following, the invention will be explained by way of example by way of example.

EXAMPLES

It turned out that conventionally dosed and mixed

Paint compositions after the compressed air spraying a worse

Have dry behavior than those that were produced with the device according to the invention and immediately afterwards splattered. The drying was carried out by means of a so-called Drying Recorder (type B.K. from The Mickle

Laboratory Engineering Co, Ltd. GB). For the assessment were

Glass strip painted with a Sata RP 1, 3 NR gun in two spray passes

(resulting dry film thickness 30-40 μιτι) It was between the Spray passages flashed off for 1 min. Subsequently, the Stage IV Dry Through Time was determined over a test period of 12 h at 22 ° C and a relative humidity of 45% analogously to ASTM D 5895. The results are shown in Table 1.

Table 1

The paint used consists of the Glasuritklarlack 923-335 (BASF Coatings GmbH), which mixed in a volumetric mixing ratio of 2: 1 with the hardener i o 929-33 (BASF Coatings GmbH) and 10 vol% dilution 352-91

was processed. The catalyst solution used was a mixture of 45 g of butyl acetate, 45 g of xylene and 10 g of DBTL (dibutyltin dilaurate).

Claims

claims

1 . Device for conveying, dosing and mixing of liquid

Paint components comprising

(A) a paint supply device, the

i. two or more paint reservoir, each with at least one outlet for different mixed together

Paint components comprises; or

(b) a metering device, which is connected downstream of the paint supply device and has a number of outlet openings of the paint reservoir or the paint reservoir corresponding number of inlet openings for the paint components, wherein the metering device is designed so that the entering via the inlet openings flow rates of the paint components to be mixed together separated from each other via serving as metering units, rotating conveyors

be conveyed positively, the conveyors are connected together so that their speeds are in fixed proportions to each other, and wherein the metering device has separate outlet openings for the now metered volume flows of the paint components, and

(C) a static mixing device, which is connected downstream of the metering device and the one of the number of outlet openings of the metering corresponding number of inlet openings for the metered

Has volume flows, and whose output is designed so that it can be connected to a paint spray gun.

2. Device according to claim 1, wherein it comprises a paint reservoir, the (a) two chambers for different mixed with each other

Contains paint components, each chamber at least one

Has outlet opening, (b) a metering device, the

Paint reservoir is connected downstream and two inlet openings for the Paint components has, wherein the metering device is designed so that the entering via the inlet openings volume flows of the paint components to be mixed are conveyed separately via serving as dosing, rotating conveyors are separated, the conveyors are connected together so that their speeds are in fixed proportions to each other , And wherein the metering device has separate outlet openings for the now metered volume flows of the paint components.

3. Device according to claim 1 or 2, wherein each rotating conveyor (a) comprises a pair of wheels and at least one wheel of the pair of wheels is connected to the corresponding wheel of the adjacent pair of wheels in the adjacent conveyor pair via a common axis, so that their

(B) in the case of the use of paddle wheels, each rotating conveyor has a paddle wheel and the paddle wheels of the conveyors are connected to each other via a common axis, so that their rotational speeds are in fixed proportions to each other.

4. The apparatus of claim 3 wherein the wheels of a pair of wheels are selected from the group consisting of circular gears, oval wheels and paddle wheels.

5. Device according to one of claims 1 to 4, wherein at least one of the paint reservoir has a closable lid, via which compressed air can be applied.

6. Method for conveying, metering and mixing two or more

Paint components, characterized in that for carrying out the method, a device according to one or more of claims 1 to 5 is used.

7. Process for coating substrates with two- or

Multi-component coating compositions, characterized in that for applying a coating, the device according to one or more Claims 1 to 6 is connected to a paint spray gun, base varnish and hardener are conveyed through the paint reservoir and the metering device in the static mixing device, the resulting homogeneous mixture of base varnish and hardener of the spray gun is supplied and applied via this to the substrate.

8. Metering device which has two or more inlet openings for components to be mixed, wherein the metering device is designed so that the incoming via the inlet openings flow rates of the paint components to be mixed with each other than above

Serving dosing, rotating conveyors are positively conveyed, the conveyors are interconnected so that their speeds are in fixed proportions to each other, and wherein the metering device has separate outlet openings for the now metered volume flows of the paint components.

9. A dosing device according to claim 8, wherein each rotating conveyor (a) has a pair of wheels and at least one wheel of the pair of wheels is connected to the corresponding wheel of the pair of wheels located in the adjacent conveyor on a common axis, so that their

10. A method for synchronized metering of at least two separate volume flows, wherein the volume flows of the metering device according to claim 8 or 9 are supplied and taken after the metering of these.