EP3554716B1 - Application device and method for applying a coating product - Google Patents

Description

The invention relates to an application device for the serial application of a coating agent on surfaces of workpieces, in particular motor vehicle bodies and / or their add-on parts, with a nozzle applicator, referred to below as a nozzle print head, which contains at least one nozzle or preferably a plurality of nozzles arranged next to one another that contains the coating agent Apply as continuous jets or individual drops to the surface to be coated. "Application device" means a device to which, in addition to the nozzle print head moved by a coating robot, other units such as the supply unit containing the coating agent and possibly a mixer, color changer and / or a rinsing device can belong. The invention also relates to a corresponding application and / or cleaning method.

For the general state of the art, z. B. be referred to the GB 2,367,771 A , the DE 10 2013 002 412 A1 , the DE 198 52 079 A1 , the WO 2011/044491 A1 , the DE 200 17 629 U1 , the DE 694 29 354 T2 and the DE 601 25 369 T2 .

EP 2 799 150 A1 and EP 2 433 716 A1 disclose application systems with nozzle arrangements for generating image patterns similar to known inkjet printers.

Furthermore, among other things WO 2010/046064 A1 (for continuous paint blasting) and DE 10 2010 019 612 A1 or. WO 2011/138048 A1 (for the generation of paint drops by applying vibrations of the coating agent) nozzle print heads are known, which enable the coating, namely painting of motor vehicle bodies with practically no overspray, because the jets or drops can be aimed precisely at the desired surface areas. The coating without overspray has that mentioned, for example WO 2010/046064 A1 The considerable advantages described, such as minimal losses of coating material and simplification of the coating booth, by dispensing with the measures previously required to remove the overspray from a painting booth and / or from an exhaust air stream.

Nevertheless, such print heads can operate with a surface coating capacity of at least 1 m ² / min, 2 m ² / min, 3 m ² / min, 4 m ² / min or even 5 m ² / min. The application efficiency of the printhead can be more than 80%, 90% or even 99%, and in the coating booth the air descent speed during operation can be less than 0.3 m / s, 0.2 m / s, 0.1 m / s , 0.07 m / s or even 0.05 m / s.

A nozzle plate with openings formed in a plate plane, which serve as nozzles, can be an essential component of the nozzle print head.

All of the above-mentioned features and advantages of the known nozzle print heads mentioned also apply to the invention described here.

It is also off, for example US 9,108,424 B2 Also known is a nozzle print head with a series of ink jet nozzles for printing a surface with predetermined patterns, which works according to the so-called drop-on-demand principle. This principle is based on the use of electric valves, with a magnetic valve needle as a piston in a coil and is lifted by supplying power to the coil. This releases a valve opening so that the fluid in question, in this case the ink, can emerge as drops of different sizes depending on the opening time. This principle can also be used in the invention described here, but in contrast to the prior art, not for ink.

US 2010/321448 A1 describes print heads with electro-pneumatically controlled ejectors in a modular plate unit with respective fluid outlets.

The above-mentioned application devices and other known nozzle print heads all have the disadvantage that they do not have multi-component coating agents such as. B. can apply the 2K or 3K paints, adhesives, sealants, adhesion promoters, primers, etc. that are customary in the painting of motor vehicle bodies.

the DE 10 2010 019 612 A1 however, already discloses a nozzle print head for the application of 2K paint, which is fed to the nozzle print head from a mixer via an input of a color changer, and also mentions a flushing system.

The invention is based on the object of enabling the coating, in particular, of structural or add-on parts of motor vehicle bodies and, in particular, their total surfaces in the manner already proposed, practically without overspray, but with any multicomponent coating agents.

This object is achieved by an application device according to the invention or a corresponding application method according to the independent claims.

The application device according to the invention initially has, in accordance with the prior art, a nozzle applicator or nozzle print head for applying the coating agent to the component to be coated. The term "nozzle pressure head" used in the context of the invention is to be understood in general terms and serves only to distinguish this nozzle applicator from all atomizers (e.g. rotary atomizers, air atomizers, airless atomizers, etc.) which emit a spray of the coating agent to be applied. In contrast, the nozzle print head produces radially narrow jets of coating agent or drops, the jet being continuous, i.e. H. is generated coherently in its longitudinal direction, while the drops fly in one and the same direction and should be separated from one another in the direction of flight. According to the invention, the nozzle print head contains a plurality of juxtaposed nozzles to which the already mixed coating agent is fed, or a plurality of nozzle units designed as double nozzles, of which one nozzle emits a first component and the other nozzle emits a second component. However, print heads with a multiplicity of, for example, one or more parallel rows of nozzles are preferred.

The invention can also be implemented with all types of print heads or other nozzle applicators which differ from conventional atomizers in the manner explained above.

In addition, according to the invention, there are at least two separate feed lines for components of the coating agent that are to be mixed with one another provided, which are provided for the common supply of all nozzles of the print head with one and the same coating agent or its components. At least two separate supply lines lead to or into the nozzle print head, since the components are to be mixed there or only after leaving the nozzle print head. In typical exemplary embodiments, the components are at least one material component (e.g. base lacquer) and at least one hardener component which reacts in a manner known per se with the material component for its hardening. In the case of the invention, the components remain separate at least as far as the nozzle print head.

An essential advantage of the invention is that the series-wise fully automatic surface coating, namely painting of complete motor vehicle bodies with any multicomponent coating agents (including effect paints) is made possible with practically no overspray.

As has already been explained, the nozzles of the print head are intended to direct the jets or drops of the coating agent or its components specifically onto individual points of the surface to be coated in order to avoid overspray. The points of impact applied here can adjoin one another or overlap one another, as will be described in more detail below.

In accordance with the prior art, it is also expedient in the invention to arrange the nozzle print head on a multi-axis coating robot which moves the nozzle print head over the surface to be coated. For example, this can generally be referred to from the prior art per se known 6 or multi-axis painting robots with or without a linear travel axis are referred to.

As has also already been explained, the invention is suitable for any multicomponent coating agent such as 2K or 3K paint (including basecoat and clearcoat), primer or primer, adhesive or sealant or preservative, etc., each at least one Base component and a hardener component that reacts with it.

The components can be mixed in different ways and at different points in the application system.

Thus, the nozzle print head can direct the at least two components separately from one another onto the surface to be coated in such a way that they mix on this. The mixing of the components takes place here through the impact of the drops or jets. There is a possibility that the printhead will eject the components to be mixed at the same time. In other embodiments of the invention, however, the print head ejects the components to be mixed one after the other, that is to say first one and then the other component (for example first the base lacquer and then the hardener, or vice versa). In both cases, the jets or drops impinge at essentially the same point.

According to another possibility of the invention, the mixing can also take place in flight, ie the nozzles of the print head are positioned in relation to one another in such a way that the components meet on the way to the surface to be coated. In this case, for example, by means of the coating robot, a corresponding distance between the nozzle print head and the one to be coated must be maintained Area are respected. Furthermore, it is possible for the drops of the components of the coating agent to be ejected at different speeds and with a time offset from one another in such a way that the later ejected drop hits the first ejected drop in flight and mixes with it.

As already mentioned, z. B. electrically valve-controlled nozzles produce drops of different sizes. According to the invention, by means of different droplet sizes, inter alia. set the mixing ratio if the components are only mixed after leaving the nozzles.

According to a further possibility of the invention, however, the mixing can also take place in the nozzle print head, for example with a mixer, which can be designed in a manner known per se as a static or dynamic mixer. The mixer can be arranged on the nozzle print head, for example integrated within the print head in a respective inflow channel of the nozzles, where it is connected to the at least two separate feed lines of the application device.

According to another possibility of mixing the components in the print head, the individual nozzles of the nozzle print head can each be designed to mix the components. According to a corresponding embodiment of the invention, the respective nozzles can contain at least two channels leading to a nozzle outlet, which in this embodiment can run concentrically to one another, wherein the nozzle outlet can be formed by at least one annular gap and a central opening. In this exemplary embodiment, each nozzle of the nozzle print head is involved actually a unit with at least two nozzle elements, namely the outlet openings of this nozzle unit.

In particular with each of the mentioned possibilities of mixing without a mixer, it can be expedient to impart a twist to at least one of the components, but preferably to both or all of the components, as a result of which they mix better. Design options for this are readily available to the person skilled in the art.

If the components are not mixed using a mixer, it may be necessary when applying continuous jets to ensure the mixing ratio of the two components by regulating the volume flow of the individual components. When applying drops, the mixing ratio can be determined by the volume of the drops, e.g. B. can be controlled by means of different opening times of the nozzles.

If a mixer is to be provided, it has corresponding inputs at which it is connected to the at least two separate supply lines, while its output is connected to the nozzles via a common line.

Controlled color change valve arrangements, usually referred to as color changers, for selecting a particular desired color lacquer from a large number of supplied different colors are generally known per se. Also in the invention, at least one color changer can be provided which is connected to at least one of the supply lines of the application device or the nozzle print head z. B. is connected for a base paint component. The color changer can expediently be arranged movably, in particular on the coating robot that moves the nozzle pressure head, for example on a its arms or on a robot axis. The closer the color changer is to the nozzle print head, the lower the unavoidable loss of color and detergent during a color change. Instead, however, the color changer can also be arranged in a stationary manner, for example on an inner or outer wall of the coating booth of the coating system under consideration here.

The nozzle print head can expediently be formed by a nozzle plate which, as nozzles, contains openings arranged next to one another in a plane of the plate. The nozzles can preferably be arranged in one or more parallel rows, for example also as columns and rows of a matrix. In corresponding embodiments of the invention, the longitudinal axes of the nozzles can run perpendicular to the plane of the plate. In other embodiments, on the other hand, the longitudinal axes of adjacent nozzles are inclined at different or identical, for example opposite, identical angles with respect to the plane of the plate.

For automatic control of their opening times, the nozzles can be connected, for example within the framework of the usual program control for coating systems, to electrical or pneumatically controlled valves arranged in or on the nozzle print head, possibly for example on the nozzle plate.

The control valves can, for example, have a piston which can be displaced electrically by a coil or pneumatically and which, depending on its position, closes or opens the nozzle.

According to an aspect of the application device according to the invention that is particularly important for multicomponent coating agents, its cleaning before and after coating processes. For example, the nozzle print head can be rinsed after a specified time or operating time, for example hourly or after several hours or at certain times of the day (end of shift or production, weekend) etc. or after reaching a certain number of coated workpieces or after reaching a certain ejected amount of paint . It can also be useful to rinse the nozzle print head after certain events in the coating operation, for example after each standstill of a belt or other conveyor device conveying the vehicle bodies or other workpieces to be coated through a coating booth as usual, or after a predetermined number of conveyor stoppages. Furthermore, the flushing can be signal-controlled after a predetermined period of time has elapsed, for example on the basis of an alarm or fault signal signal after a period of time after which the reaction of two components has progressed so far that the application system has to be flushed to avoid damage. With car body coating, rinsing can also take place in the so-called body gaps, i.e. when the robot waits for the next body to be conveyed through the coating booth during the breaks after coating a body. The flushing processes can be controlled automatically as a function of time monitoring devices.

Different detergents can be used for cleaning, depending on the application. For example, when changing the coating operation between solvent-based (2K) paint and water-based paint, other rinsing agents may be appropriate, with a separating agent such as. B. an alcohol can be used. In addition, detergents with different cleaning effects can be used (cascading), for example for Reduction of VOC emissions (i.e. volatile organic compounds) when the organic solvent content of an aqueous detergent increases. But there are also known universal detergents for water-based paints and solvent-based paints. VOC-free detergent is preferably used. For this purpose, different wash programs, which differ in their program sequence and / or their duration, can be used for different paints.

Furthermore, it can be useful to fill or wet the inner or outer surfaces of the nozzle print head that are touched by one or more components of the coating agent, especially before a planned work interruption, with a fluid that at least causes deposits of the coating agent and / or the reaction of two components of the coating agent essentially prevented (in the context of the invention, a reaction generally means a chemical and / or curing reaction).

For rinsing, detergent and pulsed air can be supplied alternately in a manner known per se. In addition or instead, it is also possible to rinse with an aerosol. If it proves necessary after flushing, the flushed paths can then be emptied or dried with compressed air.

After rinsing, it is expedient to fill the path in question with the coating agent or its components again before the start of coating, which is usually referred to as pressing in coating systems. Optionally, it can be useful here to apply at least one drop or a defined amount of the new coating agent or its components through the nozzle.

The flushing device provided for the flushing processes described can be formed by at least one flushing agent line running parallel to the component feed lines into the application device, which can optionally be connected or connectable to all nozzles via a mixer or directly. If a color changer is available, a detergent line can be connected to an input of the color changer, for example, so that the detergent can be fed to the nozzle print head through the supply line, for example. B. can be supplied for the base paint component. A rinsing agent line leading separately into the nozzle print head is also conceivable.

In expedient embodiments of the invention, an external rinsing device can also be provided in the coating system, for example a separate rinsing device arranged in the vicinity of the coating robot that can be reached by the latter. If there is a depositing device in the coating system for depositing the nozzle print head during coating breaks, the flushing device can also be integrated into the depositing device.

In any case, the flushing device should preferably be designed in such a way that the nozzle channels and also the outer surface of the nozzle print head, that is to say the nozzle plate, if applicable, can be flushed. Furthermore, backwashing of the nozzle plate or nozzle channels can be expedient, the flushing agent being pressed from the outside inwards through the nozzle channel, for example in order to clean a clogged nozzle. This eliminates the need to change the nozzle print head or the nozzle plate, thus saving material and working time. The rinsing device can be equipped with an appropriate to collect all fluids emerging during rinsing (from the nozzles), that is to say coating and rinsing agents and / or aerosols Be provided collecting device from which they can then be separated and disposed of.

In general, the lowest possible losses of coating agent and rinsing agent should occur and VOC emissions should be avoided. In the application methods described here, paint or coating losses caused by a rinsing process should be limited to less than 10 1, but preferably to less than 5 1, 200 ml, 20 ml, 10 ml, 5 ml or even 2 ml, and the The amount of detergent required should be limited to less than 10 1, but preferably less than 5 1, 2 1, 200 ml, 100 ml, 50 ml, 20 ml or even 10 ml.

In order to reduce the loss of color and the consumption of detergent when changing color, it can also be sufficient when processing multi-component paints that only the B. a 2K basecoat or 2K clearcoat and the areas touched by the mixture of both components are rinsed.

In this context it should be mentioned that especially when the components are mixed only when or after leaving the nozzles and therefore no already mixed coating material flows in the nozzle print head, the otherwise necessary detergent and time losses can be avoided, in particular because then there are no special losses Mixing elements need to be flushed.

If the mixing takes place only when or after leaving the nozzle, this also has the advantage that the mixing ratios required in each case can be set particularly easily and without problems.

Finally, it should also be mentioned that the nozzle print heads known from the prior art, which are only suitable for one-component paint, have to be adapted to the requirements for two-component coating agents. In particular, the size, that is, the hydraulic cross-sections of the nozzles and their channels, must be dimensioned in accordance with the respective mixing ratio. In addition, materials that are as solvent-resistant as possible should be used, such as seals made of FFKM (i.e. perfluorinated rubber).

Fig. 1

eine Querschnittsansicht durch eine erfindungsgemäße Lackieranlage zur Lackierung von Kraftfahrzeugkarosseriebauteilen mit Druckköpfen als Applikationsgeräte,

Fig. 2

die schematische Darstellung von aus zwei Düsen ausgestoßenen Komponenten gemäß einer Ausführungsform der Erfindung,

Fig. 3

die schematische Darstellung der Erzeugung einander überlappender Beschichtungspunkte, und

Fig. 4

eine bei einer Ausführungsform der Erfindung zu verwendenden Düseneinheit.

The invention is explained in more detail with the aid of the drawings. Show it

Fig. 1

a cross-sectional view through a painting system according to the invention for painting motor vehicle body components with print heads as application devices,

Fig. 2

the schematic representation of components ejected from two nozzles according to an embodiment of the invention,

Fig. 3

the schematic representation of the generation of overlapping coating points, and

Fig. 4

a nozzle unit to be used in one embodiment of the invention.

In the in Fig. 1 illustrated painting system according to the invention for the serial complete painting of motor vehicle bodies, the components to be painted are transported on a conveyor 1 at right angles to the plane of the drawing through a painting booth 2, in which the components are then painted by painting robots in a manner known per se. In the example shown, the painting robots 3, 4 have two swiveling robot arms and each guide an application device via a multi-axis robot hand axis. For example, it can be a robot with six or more rotary axes and possibly a linear travel axis along the conveying path. Painting robots with at least seven rotary axes have the advantage of painting bodywork that in many cases there is no need for an additional axis.

In contrast to conventional painting systems with the usual rotary atomizers or other atomizers, the painting robots 3, 4, as application devices, carry nozzle print heads 8, 9 for two-component or multi-component paint. These nozzle print heads have a much higher application efficiency than atomizers of more than 95% to 99% and thus produce practically no overspray. On the one hand, this offers the advantage that the washout below the booth, which is required in conventional painting systems with atomizers, can be dispensed with. Instead, in the painting system according to the invention, an air suction device 10 can be located under the painting booth 2, which sucks the booth air downwards out of the booth through a filter ceiling 11 if necessary, without any other effort required to collect and separate overspray. In many cases, the air extraction works without a filter. This can also take place via channels arranged near the floor.

Fig. 2 explains an embodiment of the invention in which two components of the coating agent are mixed with one another only when they strike the surface to be coated by the impact of the drops or jets. These drops or jets are generated by two schematically illustrated nozzles D1 and D2, which are in a common plane of the nozzle print head are arranged next to each other, with one nozzle ejecting a first component (e.g. base paint) and the other nozzle ejecting a second component (hardener). The ejection can take place one after the other or simultaneously at a point in time 1, and according to the painting distance L of the nozzles D1 and D2 from the surface F to be coated and the flight speeds of the components, the two components hit the surface F a little later at a point in time 2 , at least approximately at one and the same point P, where they mix with one another.

In the example shown, the ejection directions of the two nozzles D1 and D2 (shown in dashed lines) are inclined at, for example, opposite flight angles α and β to the other nozzle in relation to the painting distance L perpendicular to the surface F. The size of the chosen flight angle depends not only on the painting distance L, but also on the distance between the nozzles D1 and D2, measured parallel to the surface F, and can be, for example, between approximately 0 and 90 °. The flight speeds and / or the flight angles of the two components can also be different from one another. If the nozzles D1 and D2 are opened at different times, a displacement movement of the nozzles relative to the surface F during the application of the two components can also be taken into account.

Fig. 3 explains schematically the overlapping application of coating dots on the surface F to be coated, whereby it is usually a matter of drops of already mixed components, which in turn mix with one another on the surface F by flowing together. However, these could also be components that only mix on the surface F to be coated. While the Nozzles, for example, are moved by the coating robot at the given travel speed along the surface F, they generate a coating point, for example one drop each, with a defined size a at predetermined successive evenly spaced times t1 to t5 etc. The respective nozzle is time-controlled in such a way that defined drop spacings b along the surface F and consequently the respectively desired overlap of the applied drops result. The degree of overlap can be between more than 0% and about 75% (triple overlap), for example about 10%, 20%, 30% or 50% (double overlap with b = 1/2 a) or also b = 1/3 a or 2/3 a. Instead, the coating points can also be applied adjacent to one another, that is to say without overlapping (b = a).

In principle, such an application with or without an overlap is possible if the components are mixed before or in the nozzle print head or after leaving the nozzle, but before reaching the surface to be coated. Even if no individual drops are applied, but rather continuous jets, an overlapping application is advisable.

In Fig. 4 a nozzle unit 40 designed as a double nozzle for mixing two components of a coating agent (e.g. 2K paint) in or on the nozzle pressure head is shown schematically. The nozzle unit 40 consists essentially of an outer tubular body 41, in the interior of which, for example, is cylindrical, and an inner tube 42, which is also cylindrical, for example, is arranged concentrically. While Figure 4B ) shows a longitudinal section through this tubular nozzle unit 40 is shown in FIG Figure 4A ) a top view of the in Figure 4B ) lower nozzle face shown. The outer pipe body 41 can, as shown, protrude axially outward on the nozzle end face 43 beyond the inner tube 42. Through the inner pipe 41, one component of the coating agent (e.g. base paint) is pressed to the outlet 45, which is circular in the example under consideration, while the second component (e.g. hardener) is pressed towards the as an annular gap between the inner pipe 42 and the outer one Tubular body 41 formed outlet 46 is pressed. Conversely, the first-mentioned component could also be passed through the annular gap and consequently the second component could be passed through the inner tube.

In the example considered here, the components are mixed at the end face 43 of the double nozzle or nozzle unit 40 shown, that is to say at its outlet, where the droplets formed there mix with one another as shown. It can be useful here if the respective droplet formation does not begin at the same time, but rather the two nozzle elements, i.e. the inner tube 42 and the outlet 46 designed as an annular gap nozzle with valves (not shown), are timed so that first the drop at the inner tube nozzle and only then the drop is formed at the annular gap nozzle. The reverse order can also be useful. Instead, however, a simultaneous opening of the two nozzle elements is also conceivable.

As explained at the outset, the nozzle print head according to the invention preferably holds a multiplicity of such nozzle units, which can in particular be arranged in one or more rows.

While the invention is in Fig. 4 If a double nozzle unit is explained using the example of droplet formation, such or similar double nozzles are also conceivable for the generation of component jets which can be mixed at the nozzle outlets. In both In some cases, the two nozzle elements can be controlled jointly and / or individually with regard to their opening times by assigned controllable valves.

As already mentioned, it can be useful to provide the components to be mixed with a twist. This can be achieved, for example, by means of a spiral groove on the inside of a nozzle channel (in principle similar to a rifle barrel).

Claims (22)

1. Application device for the application in series of a coating agent to surfaces of workpieces, in particular of motor vehicle bodies and/or add-on parts thereof,
   having a nozzle printhead (8, 9) which contains a plurality of nozzles (D1, D2; 40) arranged side by side which apply the coating agent to the surface (F) to be coated as continuous jets or individual drops,
   wherein the nozzle printhead is arranged on a multi-axis coating robot (3, 4) having six or more rotary axes which moves the nozzle printhead (8, 9) over the surface to be coated,
   and having a supply unit containing the coating agent,
   wherein the coating agent consists of at least two components which are to be mixed together, which components comprise at least one material component and at least one curing agent component which reacts with the material component for the curing thereof,
   and wherein there is provided a flushing apparatus for the nozzle printhead, which

   (a) is formed by at least one flushing medium line which leads into the application device and/or into the nozzle printhead and to which the nozzles are connected or can be connected, and/or

   (b) is formed by an apparatus arranged externally in the vicinity of the multi-axis coating robot (3, 4) which moves the nozzle printhead,

   characterised in that the nozzle printhead (8, 9) has at least two separate supply lines for the components to be mixed, which supply lines are provided to jointly supply the nozzles (D1, D2; 40) with the coating agent or the components thereof, and
   the components remain separate at least until they enter the nozzle printhead (8, 9).
2. Application device according to claim 1, characterised in that the nozzles of the nozzle printhead purposively direct the jets or drops of the coating agent or the components thereof at individual points of the surface to be coated in order to avoid overspray, wherein the applied impact points in particular adjoin one another or overlap with one another.
3. Application device according to any one of the preceding claims, characterised in that the coating agent is

   (a) a liquid multicomponent lacquer,

   (b) a primer,

   (c) an adhesive or sealant or

   (d) a preserving agent,

   and in each case has at least one parent component and at least one curing agent component that reacts therewith.
4. Application device according to any one of the preceding claims, characterised in that

   (a) the nozzle printhead directs the at least two components separately from one another onto the surface to be coated in such a manner that they mix together on the surface, and/or

   (b) the nozzles of the nozzle printhead are so adjusted relative to one another that the components meet on the path to the surface to be coated, or

   (c) the components are mixed in the nozzle printhead, and/or

   (d) the nozzles of the nozzle printhead are each configured for mixing the at least two components.
5. Application device according to any one of the preceding claims, characterised in that the nozzle printhead ejects the components to be mixed simultaneously or in succession in time.
6. Application device according to any one of the preceding claims, characterised in that a mixer for mixing the components of the coating material

   (a) is arranged in the nozzle printhead, and/or

   (b) is integrated into an inflow channel of the nozzles inside the nozzle printhead and is there connected on the inlet side to the at least two separate supply lines.
7. Application device according to claim 6, characterised in that the mixer is in the form of a static mixer or in the form of a dynamic mixer.
8. Application device according to any one of the preceding claims, characterised in that there is provided at least one colour changer which

   (a) is connected to at least one of the supply lines of the application device or of the nozzle printhead and supplies selectable lacquer components of different colours to the at least one supply line in a controlled manner, and

   (b) is movably arranged relative to the surface to be coated, in particular on a lacquering robot which moves the nozzle printhead, or

   (c) is fixedly arranged in a lacquering booth.
9. Application device according to any one of the preceding claims, characterised in that the nozzles (40) each contain at least two passages which lead to a nozzle outlet (45, 46) and which preferably extend concentrically to one another, wherein the nozzle outlet (45, 46) is preferably formed by at least one annular gap and a central opening.
10. Application device according to any one of the preceding claims, characterised in that the nozzle printhead imparts a swirling motion to the ejected components by constructive shaping of the nozzles or the supply channels thereof, for the purpose of better mixing.
11. Application device according to any one of the preceding claims, characterised in that the nozzles of the nozzle printhead are controllable in respect of their respective opening and closing times, in particular by program control signals for actuating valves of the nozzles.
12. Application device according to any one of the preceding claims, characterised in that the longitudinal axes of the nozzles of the nozzle printhead, with respect to a plane of the nozzle printhead, in particular of a nozzle plate,

    (a) extend perpendicularly to the plane, or

    (b) extend at an angle to the plane, in particular at different, equal or opposite equal angles of adjacent nozzles.
13. Nozzle printhead of the application device according to any one of the preceding claims, in particular having a nozzle plate which contains, in a plate plane, openings serving as nozzles and preferably arranged in one or more parallel rows.
14. Application device according to claim 1, characterised in that the flushing apparatus is configured

    (a) for flushing the nozzle passages and/or

    (b) for flushing an outside surface of the nozzle printhead and/or a nozzle plate containing the nozzles.
15. Application device according to claim 1 or 14, characterised in that the flushing apparatus has a collecting device for collecting coating agent and/or flushing medium ejected from the nozzles during flushing.
16. Coating system having an application device according to any one of the preceding claims having one or more application robots inside a coating booth.
17. Method for the application in series of a coating agent to surfaces of workpieces, in particular of motor vehicle bodies and/or add-on parts thereof,
    wherein the coating agent is applied to the surface (F) to be coated as continuous jets or individual drops by an application device having a nozzle printhead (8, 9) which is arranged on a multi-axis coating robot (3, 4) having six or more rotary axes and which contains a plurality of nozzles (D1, D2, 40) arranged side by side,
    wherein the coating agent consists of at least two components which are to be mixed together, which components comprise at least one material component and at least one curing agent component which reacts with the material component for the curing thereof,
    and wherein there is used a flushing apparatus which is formed by at least one flushing medium line which leads into the application device and/or into the nozzle printhead and to which the nozzle or nozzles are connected or can be connected, and/or by an apparatus arranged externally in the vicinity of the multi-axis coating robot (3, 4) which moves the nozzle printhead,
    characterised in that the components are fed to the nozzle printhead (8, 9) via at least two separate supply lines by which the nozzles are jointly supplied with the coating agent or the components thereof, and the components remain separate at least until they enter the nozzle printhead (8, 9),
    wherein mixing of the at least two components takes place

    (a) on the surface to be coated,

    (b) in mid-air on the path to the surface to be coated,

    (c) in or at the nozzle printhead, or

    (d) in each case in or at the outlet of a nozzle.
18. Method according to claim 17, characterised in that the at least two components are ejected

    (a) simultaneously or

    (b) in succession in time in a controlled manner

    from separate nozzles or from at least two outlet openings of one nozzle.
19. Method according to claim 17 or 18, characterised in that the components to be mixed are ejected with a swirling motion.
20. Method according to any one of claims 17 to 19, in particular when mixing the components on the surface to be coated, characterised in that the jets or drops of the coating agent or the components thereof strike the surface to be coated as points with a defined diameter in succession in time in such a manner that they

    (a) adjoin one another or

    (b) overlap with one another, wherein the overlap is between more than 0 % and preferably approximately 75 % of the point diameter.
21. Method according to any one of claims 17 to 20, characterised by at least one of the following steps:

    (a) flushing the nozzle printhead after a specified operating period or other period of time or at fixed specified times or after at least one specified event of the coating operation;

    (b) flushing the passages of the nozzles;

    (c) flushing an outside surface of the nozzle printhead and/or of a nozzle plate containing the nozzles;

    (d) back flushing the nozzle printhead and/or a nozzle plate containing the nozzles by pressing the flushing medium into the nozzle passages from the outside inwards;

    (e) alternately supplying flushing medium and pulsed air;

    (f) flushing with an aerosol;

    (g) collecting the fluids ejected during flushing and/or an aerosol and separating it off for disposal;

    (h) pressing on the coating agent or the components thereof by re-filling the nozzle printhead after flushing;

    (i) ejecting at least one drop or a defined amount of the coating agent or of a component through the nozzle after flushing;

    (k) using different flushing media in the case of a change between solvent-based lacquer and water-borne lacquer as the parent lacquer component of the coating agent and optionally using a separating agent between the two types of lacquer;

    (1) using different flushing media with different cleaning actions;

    (m) using a universal flushing medium, in particular in the case of a change between solvent-based lacquer and water-borne lacquer as the parent lacquer component of the coating agent;

    (n) using a VOC-free flushing medium;

    (o) flushing only the paths of the application device with which only one of the components and/or the mixture of two components comes into contact, in particular only the paths with which a colour-giving component of the coating agent and the mixture of the two components comes into contact;

    (p) filling or wetting the inside or outside surfaces of the nozzle printhead which come into contact with coating agent with a fluid which prevents coating agent deposits and/or the reaction of two coating agent components.
22. Method according to any one of claims 17 to 21, characterised in that, during flushing of the nozzle printhead,

    (a) the losses of coating agent or at least one parent lacquer component caused by the flushing are limited to less than 5 1, 2 1, 200 ml, 20 ml, 10 ml, 5 ml or 2 ml, and/or

    (b) the flushing medium consumption is limited to less than 10 1, 5 1, 2 1, 200 ml, 100 ml, 50 ml, 20 ml or 10 ml.

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