EP3329030B1 - Method and device for coating a surface - Google Patents

Description

TECHNICAL AREA

The present invention relates to a method for coating a surface by means of a coating jet containing coating particles, the coating jet being directed onto the surface by a spray device at an angle of spray, according to the preamble of patent claim 1. The invention further relates to a device for coating a surface by means of a Coating jet containing coating particles, the coating jet being directed onto the surface by a spray device at an angle of spray, according to the preamble of patent claim 9.

The generic method is used for coating a surface, the coating jet containing coating particles being directed by a spray device at a predetermined spray angle onto the surface to be coated.

When coating components, especially thermal coating, the aim is always to have a uniform and homogeneously coated surface. This is particularly true when coating cylinders of a piston-cylinder arrangement, such as the inside are provided, for example, in internal combustion engines. A decisive quality criterion in such a coating process, in particular in the case of thermal coating, is the angle of incidence of the coating jet on the surface to be coated and possibly also the speed of the coating particles of the coating jet. Due to wear, assembly errors, confusion of parameters or incorrect handling, it may be possible that the desired angle of incidence of the coating jet on the surface to be coated is not correctly implemented, although all process and spray parameters are set correctly. However, as soon as the angle of incidence of the coating jet on the surface to be coated lies outside predefined limits, the quality of the surface coating is changed, since the coating particles impinging on the surface strike the surface at an unsuitable angle or at an unsuitable speed. Such errors can lead to the component to be coated being rated as "waste" in quality control, even though the process and spray parameters have been set correctly.

STATE OF THE ART

It is from the DE 199 10 892 A1 It is known to produce a coating on the surface of a substrate by means of a thermal coating process, at least one feature of the thermal spraying process influencing the quality of the spray layer being recorded, checked and / or monitored using a digital camera.

The DE 198 20 195 A1 shows and describes a method and a device for thermal spraying, a powder to be sprayed being injected from above in a substantially horizontal plasma jet. A camera is used to monitor whether the powder introduced into the plasma beam from above is in the center of the plasma beam is melted or - which is undesirable - does not penetrate into the plasma jet or is blown through the plasma jet. The image captured by the camera is used in order to be able to set an optimal injection of the powder into the plasma jet. The plasma beam is not deflected here. However, it is generally mentioned that by means of a digital camera at least one feature of the thermal spraying process influencing the quality of the spray layer can be recorded, checked and / or monitored, such as the feature influencing the quality of the spray layer including the spray angle as the angle between the spray jet and sub-beam surface is mentioned casually.

Also the US 2006/0198944 A1 shows and describes a device for plasma spraying, in which powder particles are injected into the plasma jet from the side into a plasma jet directed horizontally onto a deposition surface. As a result of this oblique injection of the powder particles into the plasma jet, the powder particles which are melted in the plasma jet are sprayed onto the surface at an angle which deviates from the horizontal direction of the plasma jet.

The US 5,047,612 A also shows and describes a plasma spraying device in which powder particles to be deposited on a surface are injected at an angle of 90 ° into a plasma jet directed horizontally onto the deposition surface. A camera is aimed at the deposition surface and captures the powder deposited on the deposition surface.

The US 2004/0245354 A1 shows and describes a method for monitoring a spraying process, the particle distribution of a particle-containing spray jet being determined by means of a particle analyzer.

From the FR 2 866 902 A1 A device for spraying metal particles by means of an electric arc is known, in which a gas stream containing the metal particles melted by the arc emerges in an axial direction from a first atomizing nozzle. This gas jet with the metal particles emerging from the nozzle in the axial direction is deflected by further gas flows which emerge from channels of a deflection nozzle device oriented at right angles to the axial direction, so that the gas flow containing the metal particles is at right angles to a surface to be coated, for example, parallel to the axial direction the inner wall of a cylinder coaxial with the nozzle. The liquid metal particles are sprayed onto the surface to be coated at right angles to the surface.

The FR 2 865 218 A1 shows and describes a method and a device for coating at least one cylinder bore by thermal arc spraying. In this prior art too, the material jet emerging from a spray nozzle of an arc spray device axially inserted into the cylinder bore is deflected by a gas jet emerging at right angles, that is to say in the radial direction of the cylinder bore, so that the molten material strikes the inner wall of the cylinder in the radial direction essentially at right angles.

PRESENTATION OF THE INVENTION

The object of the present invention is to provide a generic method for adjusting a coating jet, with which it is possible to improve the coating quality and to reduce the number of components to be referred to as "rejects" in quality control in order to achieve that all components obtain a surface coated uniformly via a coating process.

This object is achieved by the method having the features of patent claim 1.

In a method for coating a surface by means of a coating jet containing coating particles, the coating jet being directed onto the surface from a spray device at an angle of spray, the coating jet being formed from at least two partial jets, each of which emerges from an outlet opening of an associated outlet channel of the spray device, the respective axes of the outlet channels being at an angle to one another, one of the outlet channels being a spray channel for a first gas stream containing the coating particles, the outlet opening of this spray channel forming a spray nozzle and the other of the outlet channels being a control channel for a second gas deflecting the first gas stream Is gas flow, the outlet opening of this control channel forming at least one control nozzle, according to the invention the outlet opening of the spray channel forming the spray nozzle is also f the surface to be coated is directed and the coating jet emerging from the spraying device is captured with an image capturing device. The spray angle during the coating process or between two coating processes is determined from the captured image of the coating jet, and if the determined spray angle deviates from a predetermined target spray angle, the spray angle is adjusted and thereby readjusted to the target spray angle. If the determined spray angle deviates from a predetermined desired spray angle, the spray angle is adjusted and thereby readjusted to the desired spray angle, wherein if the determined spray angle deviates from the predetermined desired spray angle, the volume flow of a first partial jet of the at least two partial jets increases and the volume flow of a second sub-beam of the at least two sub-beams is reduced.

BENEFITS

This determination and adjustment of the spray angle according to the invention with an image capturing device makes it possible in a particularly advantageous manner to either keep the spray angle constant during a coating process or to control the spray angle between two coating processes and to readjust it for one or more subsequent coating processes. In this way, a longer service life of the spraying device can be achieved while at the same time ensuring a constant coating quality. The wear of the spray device or of parts of the spray device, for example of its nozzles, can also be recognized in good time and, if necessary, compensated for before a wear-related change in the spray angle leads to an incorrect method result.

In contrast to a prior art, where at most a deflection of the plasma jet occurs due to the powder to be melted from the side into the plasma jet, in the present case a plasma jet already containing the coating particles (first gas stream) is applied to the first gas stream from the side acting second gas flow specifically deflected. This control of the first gas stream containing the coating particles by means of the second gas stream allows the spray angle to be set in a targeted manner without influencing the distribution of the coating particles in the first gas stream. The process of mixing the coating particles with the first gas stream is thus in the present invention in contrast to the prior art according to the DE 198 20 195 A1 provided separately from the influence on the spray angle.

Advantageous developments of the method according to the invention are specified in the subclaims which refer back to claim 1.

It is also advantageous if the coating jet emerging from the spray device is detected to determine the spray angle from the side, that is to say transversely, preferably at right angles, to the plane in which the coating jet is deflected by the spray angle. The determination of the spray angle can be carried out particularly precisely by means of the image acquisition described when the coating jet emerges as a free jet from the spray device.

The spray angle can also be adjusted in another way, for example by pivoting outlet nozzles provided with the outlet openings for the partial jets or by pivoting at least one spray nozzle for the coating jet or by providing mechanically variable jet deflecting means for at least one of the partial jets and / or for the coating jet.

Preferably, the increase in the volume flow of the first partial jet and the decrease in the volume flow of the second partial jet always take place in such a way that the sum of the volume flows of the partial jets is constant. In this way it is achieved that a change in the spray angle due to a change in the volume flows of the partial jets does not lead to a change in the quality of the coating due to a change in the total volume flow.

Alternatively, the increase in the volume flow of the first partial jet and the decrease in the volume flow of the second partial jet always take place in such a way that the energy content of the coating jet formed from the partial jets remains constant. The energy content of a gas jet containing coating particles is determined by the Mass of the individual particles contained in a gas volume, the temperature of each particle, the speed of each particle and the (mostly negligible) energy content of the gas.

In a further advantageous embodiment of the method according to the invention, the angle between the axes of the outlet channels is a right angle, so that the partial beams strike one another at right angles. As a result, the control partial jet emerging from the control nozzle with the lowest volume flows can already effect an effective deflection of the partial particle jet emerging from the spray nozzle and containing the coating particles.

The method is preferably designed for thermal coating of the surface, the spraying device being a thermal spraying device with a particle flow generator. However, the method can also be designed as a kinetic coating method, the particles generated in a particle flow generator being applied to the surface to be coated at a very high speed (for example greater than 600 m / sec).

It is particularly advantageous if the first gas stream flows through the particle stream generator, which passes through the spray channel as a gas stream enriched with coating particles and exits the spray nozzle.

In such a method for thermal coating, the first partial jet comprising the coating particles is advantageously a plasma jet generated by a plasma torch.

In the case of such a plasma coating, the power of the at least one is used to regulate the energy content of the coating beam Plasma torch regulated. Such regulation of the plasma torch, in addition to the regulation of the volume flows of the two partial jets, ensures in a particularly reliable manner that both the energy content and the particle content in the coating jet remain constant while the spray angle is being changed.

The invention is also intended to provide a device for adjusting a coating jet, which is particularly suitable for carrying out the method according to the invention. This part of the task is solved by the device with the features of claim 9.

In a device according to the invention for coating a surface by means of a coating jet containing coating particles, wherein the coating jet can be directed onto the surface from a spray device at a spray angle, in particular for carrying out a method according to one of the preceding claims, the spray device having a spray channel for a coating particle the first gas stream and at least one control channel for a second gas stream deflecting the first gas stream is provided, the outlet opening of the spray channel forming a spray nozzle and the outlet opening of the at least one control channel forming a control nozzle, the gas streams emerging from the outlet openings in each case forming a partial jet and together the Forming the coating jet and the axes of the outlet channels being at an angle to one another is, according to the invention, the outlet forming the spray nozzle Open the spray channel towards the surface to be coated. In addition, at least one image capturing device is provided, which is designed to capture the coating beam during the coating process or between two coating processes, and an image evaluation device is provided, which is designed to detect that of the to receive at least one image acquisition device and to determine the spray angle of the coating jet and / or the angle of incidence of the coating jet impinging on the surface. Means are also provided with which the spray angle can be adjusted. wherein the means by means of which the spray angle can be adjusted are means with which the volume flow of the gas flow exiting through the outlet channel can be varied.

This device enables the adjustment of a coating beam in a particularly advantageous and reliable manner both during the coating of a surface and for calibration between two coating processes. This device is particularly suitable for carrying out the method according to the invention.

Advantageous further developments of this device are specified in claims 10 to 13 which are dependent on claim 9.

It is advantageous if the means for changing the volume flow are formed by throttle devices adjustable by means of a respective actuator. Such automatically adjustable throttle devices make it possible to vary the gas flows in the control channel or in the spray channel in such a way that the respective volume flow required for the desired setting of the spray angle passes through the channels.

It is particularly advantageous if an actuating or regulating device is provided which acts upon the means for changing the volume flow, in particular the actuators of the throttle devices, with an actuating or regulating signal. This enables process automation.

In this embodiment of the device, the control device receives the spray angle and / or the angle of incidence supplied by the image evaluation device as a control variable. With this data, the control or regulating device can then make the necessary adjustment of the partial jets and thus adjust the spraying angle of the coating jet to the desired dimension or adjust it accordingly. In principle, it would also be possible to determine the angle of incidence of the coating jet impinging on the surface and to determine the spray angle from this.

In a particularly advantageous embodiment of the device according to the invention, the spraying device is equipped with a particle flow generator. The particle flow generator, which can have, for example, a plasma burner, a wire spray burner or a cold gas burner, generates a metallic and / or ceramic particle mist as a coating jet together with the gas flow. In the case of a plasma torch, the plasma can be used to form a metallic and / or ceramic particle mist in conjunction with the gas stream as a coating jet.

It is particularly advantageous if the control device - in addition to the respective volume flow of the gas flows - acts on the at least one particle flow generator with a signal which regulates its particle output power. This makes it possible to keep the particle density constant in the coating jet.

A coated surface is obtained with the method of the present invention. In particular, the method according to the invention is used to obtain a coated surface of an inner cylinder wall of a piston-cylinder arrangement. It is particularly advantageous if the method for coating on the inner wall of the cylinder provided tread of a piston-cylinder arrangement is used in an internal combustion engine, so that such an internal combustion engine with treads coated according to the invention is also included as a result of the method.

Preferred exemplary embodiments of the invention with additional design details and further advantages are described and explained in more detail below with reference to the attached drawing.

BRIEF DESCRIPTION OF THE DRAWINGS

Fig. 1

ein schematisches Prozessschaubild eines erfindungsgemäßen Verfahrens anhand einer schematisch dargestellten erfindungsgemäßen Vorrichtung;

Fig. 2

einen schematisch dargestellten Aufbau einer Spritzeinrichtung der erfindungsgemäßen Vorrichtung und

Fig. 3

einen alternativen Aufbau einer Spritzeinrichtung.

It shows:

Fig. 1

a schematic process diagram of a method according to the invention using a schematically illustrated device according to the invention;

Fig. 2

a schematically illustrated structure of a spray device of the device according to the invention and

Fig. 3

an alternative structure of a spray device.

PRESENTATION OF PREFERRED EMBODIMENTS

In Fig. 1 A process diagram of a coating system is shown, with which a particularly advantageous implementation of a method according to the invention for adjusting a coating jet can be carried out.

One below in connection with Fig. 2 Spray device 1 described in more detail is arranged such that it directs a coating jet S containing coating particles from a spray nozzle 10 onto a surface 2 to be coated at a predetermined spray angle α. For this purpose, the surface is preferably arranged perpendicular to a longitudinal axis x of the spray device 1.

In the example shown, an image capturing device 3 for taking images of the coating jet S is arranged laterally offset next to the coating jet S between the spray device 1 and the surface 2. The image capture device 3 has a camera 30, which captures the coating beam S from the side, so that the spray angle α lies in an image plane recorded by the camera 30. The camera 30 preferably captures the entire longitudinal extent of the coating jet S from its exit from the spray device 1 to the surface 2, so that the impact area S ′ formed by the coating jet S on the surface 2 is also captured by the camera 30. Alternatively, the spray angle α can also be determined in the free jet, that is to say without providing the surface 2 to be coated.

The image recorded by the camera 30 is converted in the image capture device 3 by means of an image sensor (not shown) in a manner known to the person skilled in the art into electrical signals which are forwarded to an image evaluation device 31. The image evaluation device 31 analyzes the image signals and uses them to determine the spray angle α and thus the angle that hits the surface 2 Impingement angle β of the coating beam S. These determined angle data are then forwarded to an actuating or regulating device 32. The control or regulating device 32 compares the angle or angles obtained (spray angle α and / or impact angle β) with a respectively assigned, predetermined target spray angle stored in a storage device 33 and determines the corresponding angular deviation. From this angular deviation Δα between the measured actual spray angle and the target spray angle, an actuating signal is generated which is forwarded to the spray device 1 and there adjusts the spray angle α of the coating jet S to the predetermined target spray angle in a manner described further below. If such an adjustment is not possible, a wear alarm signal is generated and preferably the further operation of the spray device 1 is prevented.

After adjustment of the spray angle α, the coating beam is again measured by means of the image capture device 3, so that a closed control circuit is formed in this way. Such regulation can take place during an active coating process, as a result of which the spray angle α is continuously readjusted to the predetermined target spray angle and thus a continuous quality control of the spraying process is ensured.

However, there are also situations in which such continuous image acquisition of the coating beam S is not possible, for example if the coating is carried out in cavities in which it is not possible to place an image acquisition device next to the coating beam S. This is the case, for example, when coating cylinder inner wall surfaces in piston-cylinder arrangements, such as, for example, in piston internal combustion engines. In these cases, the described checking of the spray angle α does not take place continuously, but between two coating processes. For example, a a certain number of coating processes are carried out and then the spraying device 1 can be moved into a measuring and calibration position, for example the one in FIG Fig. 1 shown structure corresponds, but preferably the surface 2 to be coated is omitted and the coating beam S is measured as a free jet. In this measuring and calibration position, the spray angle α can then be adjusted or adjusted to a predetermined target spray angle. After such a calibration process, a plurality of coating processes can then be carried out again. It is particularly advantageous if the angular deviation compensated for in such a calibration process is recorded and is related to the coating performance achieved between the two previous calibration processes. By updating this data, it is possible to determine a wear trend, so that a forecast can be made about the remaining time of use of the spray device 1 until a wear limit is reached.

A possible construction of a spray device 1 which can be used for the method according to the invention and the device according to the invention is shown schematically in FIG Fig. 2 shown.

The spray device 1 has an elongated housing 1 'which extends along a longitudinal axis x of the spray device 1 and which is also referred to as a spray lance.

In the housing 1 'two channels 11, 13 are provided which extend essentially parallel to the longitudinal axis x in the longitudinal direction through the housing 1'. At a first end of the housing 1 ', these channels 11, 13 each open into a connection element 11', 13 'for a respectively assigned gas supply line 11 ", 13".

At the other axial end of the housing 1 ', the channels 11, 13 form outlet channels 12, 14 which each open to the outside with an outlet opening 12', 14 '. The outlet channels 12, 14 are not arranged parallel to one another, but the respective axes 12 ", 14" of the outlet channels 12, 14 are inclined at an angle γ to one another. In the in Fig. 2 the example shown, the angle γ is approximately 90 °.

The first channel 11, the outlet channel 12 of which has an axis 12 "which runs parallel to the longitudinal axis x of the spray device 1, is provided with a particle generator 17 which has a plasma torch 17 '. This particle generator 17 is supplied by a gas supply line 11" Process gas flows through, whereby melted particles are entrained by the gas stream by means of the plasma torch 17 '. The process gas jet provided with these coating particles first emerges through the outlet channel 12 and its outlet opening 12 'forming the spray nozzle 10 in an axially parallel direction from the housing 1' of the spray device as a first partial jet S1.

A second gas, which can be supplied through the second gas supply line 13 ″ and can correspond to the process gas, but which can also be simply compressed air, is introduced through the second channel 13 into the second outlet channel 14 forming a control channel, and from there passes a control nozzle 18 forming outlet opening 14 'and strikes the first gas stream emerging from the spray nozzle 10 and containing the coating particles as a second partial jet S2 at an angle γ. This second partial jet S2 deflects the first partial jet S1 from its axis-parallel direction the second partial jet S2, which forms a control gas flow, unite to form a resulting coating jet S, the jet center axis S "of which is about the spray angle α to the axis 12" of the spray channel 12 away from the control nozzle 18 (in Fig. 2 is inclined).

In each of the two channels 11, 13, a throttle device 15, 16 is provided which can be adjusted by means of an associated actuator 15 ', 16'. The volume flow of the process gas can be regulated by means of the first throttle device 15, which is provided in the first channel 11. The volume flow of the control gas can be regulated by means of the second throttle device 16, which is provided in the second channel 13. The respective actuators 15 ', 16' are connected to the actuating or regulating device 32 via signal lines 15 ", 16" and can each receive actuating signals from the latter.

The particle generator 17 is also connected to the actuating or regulating device 32 via an actuating signal line 17 ″ and can receive actuating signals from the latter.

Even if in the representation after Fig. 2 An example is shown in which the gas stream loaded with the coating particles emerges in a direction parallel to the longitudinal axis x of the spray device 1, variants of the spray device 1 are also conceivable in which the gas stream contaminated with coating particles emerges at an angle to the longitudinal axis x. In an extreme case, another exemplary variant can be designed such that the gas stream loaded with the coating particles emerges at a right angle to the longitudinal axis x, while the control gas stream emerges parallel to the longitudinal axis x. Such a variant is in Fig. 3 shown schematically, with the same reference numerals as in the example of Fig. 2 concern the same components.

The invention is not restricted to the above exemplary embodiment, which only serves to explain the basic idea of the invention in general. Within the scope of the protection defined by the claims, the device according to the invention can also be different from those described above Accept design forms. The device can in particular have features that represent a combination of the respective individual features of the claims.

Reference symbols in the claims, the description and the drawings serve only for a better understanding of the invention and are not intended to limit the scope of protection.

Reference list

1

Spraying device

1'

elongated housing

2nd

surface

3rd

Image capture device

10th

Spray nozzle

11

channel

11 '

Connecting element

11 "

first gas line

12th

Outlet channel / spray channel

12 '

Outlet opening

12 "

axis

13

channel

13 '

Connecting element

13 "

second gas line

14

Exit channel / control channel

14 '

Outlet opening

14 "

axis

15

Throttle device

15 '

Actuator

15 "

Signal line

16

Throttle device

16 '

Actuator

16 "

Signal line

17th

Particle flow generator

17 '

Plasma torch

17 "

Control signal line

18th

Control nozzle

30th

lens

31

Image evaluation device

32

Actuator or control device

33

Storage device

x

Longitudinal axis

S

Coating jet

S "

Blasting axis

S1

Partial beam

S2

Partial beam

α

Spray angle

β

Impact angle

γ

angle

Claims (13)

1. A method for coating a surface (2) by means of a coating jet (S) containing coating particles, wherein the coating jet (S) is directed onto the surface (2) at a spraying angle (α) by a spraying means (1), wherein the coating jet (S) is formed from at least two partial jets (S1, S2) which emerge in each case from an exit opening (12', 14') of an associated exit duct (12, 14) of the spraying means (1), wherein the respective axes (12", 14") of the exit ducts (12, 14) are at an angle (γ) to each other, wherein one of the exit ducts (12, 14) is a spraying duct (12) for a first gas stream containing the coating particles, wherein the exit opening (12') of this spraying duct (12) forms a spray nozzle (10) and wherein the other one of the exit ducts (12, 14) is a control duct (14) for a second gas stream which deflects the first gas stream, wherein the exit opening (14') of this control duct (14) forms at least one control nozzle (18);
   characterised in that
   the exit opening (12') of the spraying duct (12) which forms the spray nozzle (10) is directed at the surface (2) to be coated;
   in that the coating jet (S) emerging from the spraying means (1) is detected with an image acquisition means (3);
   in that the spraying angle (α) is ascertained from the detected image of the coating jet (S) during the coating operation or between two coating operations;
   in that in the event of the ascertained spraying angle (α) deviating from a predetermined desired spraying angle the spraying angle (α) is adjusted and thereby readjusted to the desired spraying angle, and
   in that in the event of the ascertained spraying angle (α) deviating from the predetermined desired spraying angle the volume flow of a first partial jet (S1) of the at least two partial jets is increased and the volume flow of a second partial jet (S2) of the at least two partial jets is reduced.
2. A method according to Claim 1,
   characterised in that
   the coating jet (S) emerging from spraying means (1) is detected from the side, preferably as a free jet, with the image acquisition means (3) to ascertain the spraying angle (α).
3. A method according to one of the preceding claims,
   characterised in that
   the increase in the volume flow of the first partial jet (S1) and the reduction in the volume flow of the second partial jet (S2) always take place such that the sum of the volume flows of the partial jets (S1, S2) or the energy content of the coating jet (S) formed from the partial jets (S1, S2) is constant.
4. A method according to one of the preceding claims,
   characterised in that
   the angle (γ) between the axes (12", 14") of the exit ducts (12, 14) is a right-angle, so that the partial jets (S1, S2) meet each other at right-angles.
5. A method according to one of the preceding claims,
   characterised in that
   the method is designed for thermally coating the surface, the spraying means (1) being a thermal spraying means with a particle stream generator (17).
6. A method according to Claim 5,
   characterised in that
   the flow of the first gas stream passes through the particle stream generator (17), which stream passes as a gas stream enriched with coating particles through the spraying duct (12) and emerges from the spray nozzle (10).
7. A method according to Claim 5 or Claim 6,
   characterised in that
   the first partial jet is a plasma jet generated by a plasma burner (17'), which jet contains the coating particles.
8. A method according to Claim 7,
   characterised in that
   the output of the at least one plasma burner (17') is regulated to regulate the energy content of the coating jet (S).
9. A device for coating a surface (2) by means of a coating jet (S) containing coating particles, wherein
   the coating jet (S) can be directed onto the surface (2) by a spraying means (1) at a spraying angle (α), especially for carrying out a method according to one of the preceding claims, wherein the spraying means (1) is provided with a spraying duct (12) for a first gas stream containing coating particles and at least one control duct (14) for a second gas stream which deflects the first gas stream, wherein the exit opening (12') of the spraying duct (12) forms a spray nozzle (10) and wherein the exit opening (14') of the at least one control duct (14) forms a control nozzle (18), wherein the gas streams emerging from the exit openings (12', 14') in each case form a partial jet (S1, S2) and jointly the coating jet (S), and wherein the axes (12", 14") of the exit ducts (12, 14) are at an angle (γ) to each other;
   characterised in that

   - the exit opening (12') of the spraying duct (12) which forms the spray nozzle (10) is directed at the surface (2) to be coated;

   - in that at least one image acquisition means (3) is provided which is designed to detect the coating jet (S) during the coating operation or between two coating operations;

   - in that an image evaluation means (30) is provided which is designed to receive the image signals supplied by the at least one image acquisition means (3) and to ascertain therefrom the spraying angle (α) of the coating jet (S) and/or the angle of incidence (β) of the coating jet (S) which strikes the surface (2);

   - in that means are provided by means of which the spraying angle (α) is adjustable, and

   - in that the means by means of which the spraying angle (α) is adjustable are means with which the volume flow of the respective gas stream emerging through the exit duct (12, 14) can be changed.
10. A device according to Claim 9,
    characterised in that

    - the means for changing the volume flow are formed by choke means (15, 16) which are adjustable by means of a respective actuator (15', 16').
11. A device according to Claim 9 or Claim 10,
    characterised in that

    - an actuating or regulating means (32) is provided which acts upon the means for changing the volume flow, especially the actuators (15', 16') of the choke means (15, 16), with in each case an actuating or regulating signal, wherein preferably the actuating or regulating means (32) receives as controlled variable the spraying angle (α) supplied by the image evaluation means (30) and/or the angle of incidence (α).
12. A device according to one of Claims 9 to 11,
    characterised in that
    the spraying means (1) which is preferably designed as a thermal spraying means is equipped with a particle stream generator (17) which preferably has a plasma burner (17').
13. A device according to Claim 11 and 12,
    characterised in that
    the regulating means (32) acts upon the at least one particle stream generator (17) with a signal which regulates the particle output thereof.

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