System for reproducible application of surface cleaning or functional coatings with a temporary effect

Abstract

The invention relates to a system for the reproducible application of temporary surface cleaning or functional coatings by spraying through one or more pneumatic two-fluid nozzles with nozzle bodies which are connected to at least one reservoir, wherein the reservoir is filled or fillable with sprayable surface cleaning or functional coating fluid and furthermore with a pressurized gas, in particular a compressed air source, which can be connected to the respective two-fluid nozzle in order to convey the surface cleaning or functional coating fluid according to the principle of a jet pump or injector nozzle, also with Laval effect, and to apply it by spraying onto a surface to be treated, in particular the surface of an edge of a piece of furniture, wherein the respective two-fluid nozzle is designed as a minimum quantity nozzle valve with an actuating device in the nozzle body.A device for determining the acoustic sound level spectrum generated during the spraying process is provided directly on or in the nozzle body, wherein the acoustic spectrum is recorded with respect to the frequency profile of the sound level and supplied to a connected computing unit.

Description

[0001] The invention relates to a system for the reproducible application of temporary surface cleaning or functional coatings by spraying through one or more pneumatic two-fluid nozzles with nozzle bodies, which are connected to at least one reservoir, wherein the reservoir is filled or fillable with sprayable surface cleaning or functional coating fluid and furthermore with a pressurized gas, in particular a compressed air source, which can be connected to the respective two-fluid nozzle in order to convey the surface cleaning or functional coating fluid according to the principle of a jet pump or injector nozzle, also with Laval effect, and to apply it by spraying onto a surface to be treated, in particular the surface of an edge of a piece of furniture, wherein the respective two-fluid nozzle is designed as a minimum quantity nozzle valve with an actuating device on the nozzle body, according to the preamble of claim 1.

[0002] DE 10 2020 128 833 A1 discloses a supply system for applying various, application-specific, temporary surface functional coatings. The surface functional coating is applied during processing by spraying through several pneumatic two-component nozzles with nozzle bodies that can be attached to a processing machine, the nozzle bodies being connected to a reservoir.

[0003] According to the teaching there, the storage vessel is designed as a mixing vessel, which is controlled and connected to a multitude of component vessels, such that, according to a predetermined program selection, ingredients from the component vessels can be transferred into the mixing vessel, whereby the two-component nozzles are supplied from the mixing vessel.

[0004] DE 20 2016 106 913 U1 discloses pneumatic two-component nozzles with a nozzle body that can be connected to a storage vessel.

[0005] The connection between each two-component nozzle, i.e., its nozzle body, and the reservoir is sealed. This prevents contaminants from the industrial environment from entering the reservoir and potentially being transported via the surface coating fluid through the nozzle to the surface being treated, with detrimental consequences regarding nozzle wear on the one hand and potentially insufficient effectiveness of the functional coating on the surface being treated on the other.

[0006] The two-fluid nozzles are designed as minimum quantity nozzle valves with an actuating device in the nozzle body.

[0007] In a preferred embodiment, the adjusting device has an interchangeable needle with a conical seat tip. The conical seat tip dips into a bore in the nozzle body that is complementary in shape, maintaining an annular gap. By adjusting the needle, the annular gap can be increased or decreased, thereby determining the amount of functional coating fluid supplied to the spray jet.

[0008] The needle has a central first bore in the area of ​​the cone tip, oriented in the longitudinal direction of the needle over a predetermined path, which intersects with a second bore oriented in the transverse direction of the needle, such that even with a closed annular gap a defined quantity of liquid can be extracted via the bore dimensions.

[0009] In a further development of the invention according to DE 20 2016 106 913 U1, the nozzle body has a blind hole bore for receiving the needle located in a needle holder, wherein the needle holder can be screwed into the blind hole bore.

[0010] The needle holder, in turn, has a through-hole for guiding the needle, with the through-hole and the needle having complementary threads for needle adjustment.

[0011] The blind bore is connected to a first channel passing through the nozzle body, with the first channel ending in an opening for supplying the liquid.

[0012] This opening may have a screw thread or screw connection, or transition into such a screw connection, for example to enable a hose connection.

[0013] The annular gap transitions into a second channel, which leads to a third channel to which the pressurized gas source can be connected. The end of this third channel also features a screw connection or similar fitting. At the intersection of the second and third channels, a two-component mixture channel connects, leading into a nozzle opening in the nozzle body.

[0014] The proposed two-component nozzle can preferably be used for edge coating of furniture panels, wherein the coating also includes surface cleaning of the edge or the application of release agents.

[0015] A method for monitoring the function of a spray jet, especially in painting plants, is known from DE 196 51 702 C1.

[0016] In this regard, the use of an acoustic system is proposed, in which a useful signal is determined from the noise of the spray jet and the useful signal is subjected to analysis to assess the function of the spray jet.

[0017] In the device unit for determining a flow rate of at least one first nozzle according to DE 10 2020 204 686 A1, it is assumed that a certain flow rate leaving the nozzle has a natural frequency from an acoustic point of view.

[0018] The device there has a processing unit and a microphone, wherein the processing unit is configured to detect a frequency spectrum by means of the microphone at a predetermined time and to determine the flow rate of the at least first nozzle as a function of the detected frequency spectrum.

[0019] In the injection pump test bench according to DE 34 02 804 A1, the injection quantity is recorded by means of a microphone.

[0020] The microphone detects pressure surges during injection in a closed air space, with the integral of the microphone signal representing a measure of the injected quantity. The total injected quantity can then be determined using a calibration system.

[0021] The nozzle flow detection system according to US 2017080445 A uses a microphone attached to each nozzle under test to capture and store the corresponding nozzle's sound signature. By determining changes in sound at each nozzle, it should be possible to detect flow changes before a pressure change manifests as a problem in the system.

[0022] A significant change in sound should be detectable in the case of clogged nozzles or nozzles with excessive wear and excessive flow.

[0023] From the foregoing, the object of the invention is to provide a further developed system for the reproducible application of temporarily acting surface cleaning or functional coatings by means of spraying through one or more pneumatic two-component nozzles with nozzle bodies, whereby the teaching according to DE 20 2016 106 913 U1 is used as an example with regard to the nozzle bodies.

[0024] The novel system is designed to utilize a known method of capturing the frequency spectrum of the relevant two-component nozzles, but in comparison to previously known spray systems, it focuses on minimizing consumption.

[0025] This requires attention to the specific technological challenges of edgebanding machines in the furniture industry and related sectors. These machines require the application of minute, finely atomized liquids—for example, as release agents, cooling agents, or cleaning agents—to defined sides or edges of typically panel-shaped furniture pieces that pass the nozzles at relatively high belt speeds. The minimal amounts applied are not intended to remain on the edge or furniture surface, especially not for extended periods, but rather to support or enable the subsequent technological step.

[0026] Due to automated manufacturing in the furniture industry, a key objective of the present invention is to design the minimum quantity spraying system in such a way that the corresponding liquids or solutions can be applied uniformly and reproducibly over a longer period of time without manual intervention.

[0027] In addition, it is important to monitor the current condition of the two-component nozzles, the quantity applied, the quality of the spray jet and the reliability of the two-component nozzles in question, in order to carry out preventive replacement or maintenance work if necessary and to avoid production interruptions.

[0028] The problem of the invention is solved by the teaching according to the applicable main claim, wherein the dependent claims include at least expedient embodiments and further developments.

[0029] It is therefore assumed that a system for the reproducible application of temporary surface cleaning or functional coatings is used by spraying through one or more pneumatic two-component nozzles with nozzle bodies, wherein the nozzle bodies are connected to at least one reservoir.

[0030] The reservoir(s) are filled or fillable with sprayable surface cleaning or functional coating fluid. Furthermore, a pressurized gas connection, in particular a compressed air source, is provided, which can be connected to the respective two-fluid nozzle in order to convey the surface cleaning or functional coating fluid according to the principle of a jet pump or injector nozzle, also with Laval effect, and to apply it by spraying it onto a surface to be treated, in particular the surface of an edge of a piece of furniture, wherein the respective two-fluid nozzle is designed as a minimum quantity nozzle valve with an actuating device in the nozzle body.

[0031] According to the invention, a device for determining the acoustic sound level spectrum generated during the spraying process is provided directly on or in the nozzle body.

[0032] The acoustic sound level spectrum is recorded with respect to the frequency response of the sound level and fed to a connected processing unit.

[0033] In the computing unit, a comparison is made with a calibration or target spectrum and a check for significant deviations is carried out, so that targeted actuation of the actuating device of the two-fluid nozzle, a nozzle replacement and / or maintenance can be carried out to restore the calibration or target spectrum.

[0034] The aim here is to ensure a consistent and reproducible output and application of the surface cleaning or functional coating fluid throughout the respective operating period.

[0035] In particular, if a piezoelectric disc microphone or similar sound transducer is integrated on or in the nozzle bodies, continuous measurement of the sound level spectrum of the nozzle jet is possible in a simple manner.

[0036] Extensive tests, initiated by the applicant, have shown that the measured sound level spectrum has two essential components.

[0037] Firstly, in the higher frequency range, there is a typical sound level profile for an outlet nozzle with turbulent outflow, featuring a characteristic Strouhal maximum, and secondly, in the lower frequency range, a rapid drop in level to a local minimum. The frequency of the Strouhal maximum is directly related to the jet velocity in the nozzle or the first few millimeters after the jet exits.

[0038] A reduction in beam velocity is noticeable in the spectrum by a shift of the Strouhal maximum towards lower frequencies and by a reduction in the sound level in the intensity bell.

[0039] It was recognized that the origin of the sound components is, among other things, the vortex shedding from turbulent nozzle jets in the first few millimeters after jet exit. The width of a measured sound dome is therefore related to the homogeneity of the fluid turbulence in the spray jet. An undesirable widening of the intensity dome indicates a less uniform fluid turbulence in the jet, which negatively affects the homogeneity of the material application.

[0040] A uniform absorption of material into the flowing air manifests itself in a narrow and relatively high sound dome.

[0041] In an embodiment of the invention, the system comprises a device for determining the acoustic spectrum, in particular in the form of a piezoelectric transducer or a condenser microphone.

[0042] According to the exemplary embodiment, the actuating device of the two-component nozzle can be operatively connected to an electromechanical actuator.

[0043] This actuator can be an electronically controlled stepper motor to achieve automatic correction of the spray jet or the discharge quantity.

[0044] The Strouhal maximum and its distribution in the higher frequency range of the spectrum, and the fall or fall rate of the respective low frequency peak of the spectrum, are therefore used as significant values ​​for the spray jet.

[0045] The necessary calibration or target spectrum is specified to achieve the highest possible frequency of the Strouhal maximum for homogeneous turbulence in the spray jet and the lowest possible drop in the low-frequency peak, and is readjusted or recalibrated as needed.

[0046] Frequency analysis includes recording the frequency response or sound level spectrum in the range of at least up to 15 kHz and above.

[0047] To determine a target frequency spectrum specific to each individual case, an analysis of the spray jet and the distribution of functional coating particles within the spray jet can be performed using optical or optoelectronic means. This simultaneously determines the expected application rate per unit of time.

[0048] According to extensive investigations, the working pressure of the compressed air source is set to a range of essentially 2.0 to 3.5 bar, particularly preferably to essentially 3 bar, such that the supersonic shock range, resulting from an opening nozzle channel and expansion of the compressed gas within the nozzle body, is formed.

[0049] The distance between the exit point of the respective two-component nozzle and the surface to be treated is set to a range between 2.5 and 5.0 cm, in particular essentially 3.0 cm.

[0050] The invention will be explained in more detail below with reference to an exemplary embodiment and with the aid of figures.

[0051] This shows: Fig. 1 shows an exemplary sound level spectrum of a two-fluid nozzle with the sound level over frequency in the range from greater than 0 Hz to approximately 20 kHz; Fig. 2 shows a further representation of the sound level spectrum along with the corresponding sound level, linearized with recognizable changes in the Strouhal maximum or its shift at a relatively low mass flow rate (solid line) and a large-volume mass flow rate (dashed line); Fig. 3 shows a cross-section through a typical nozzle for solvent application in edgebanding machines and the pressure profile as well as the flow velocity profile within the nozzle, spatially assigned to the respective nozzle sections and with the sections labeled from compressed air inlet DE to the throttle channel DK to the enlarged channel EK with liquid inlet FE.

[0052] The exemplary embodiment focuses on investigations of two-material nozzles for edgebanding machines and the sound pressure generated by the nozzles in the audible range of essentially 16 Hz to 20 kHz.

[0053] All investigated nozzles, which mix liquid solvent into the compressed air carrier via the Venturi effect, exhibit a broadband sound level spectrum in the frequency range between 2 and 20 kHz, which is reproducible using the similarity function for turbulent outflow. A characteristic average velocity of the free jet can be determined from this similarity function, which is suitable as a parameter for film deposition.

[0054] In the lower frequency range between 16 Hz and 2 kHz, the measured sound level of all investigated nozzles drops hyperbolically with increasing frequency. This low-frequency sound is attributed to the flow and the solvent admixture in the actual nozzle channel.

[0055] It was discovered that a shape parameter can be determined from hyperbolic adjustments to the measured level profile, which characterizes the degree of broadbandity of the low-frequency sound. This shape parameter can be used as a diagnostic parameter for beam generation and phase mixing in the nozzle channel according to the invention.

[0056] The measured sound spectra and diagnostic parameters vary with external operating pressure, compressed air volume flow rate, nozzle channel geometry, and solvent mass flow rate. For quality control during operation of the corresponding two-component nozzle, a master sound level spectrum can be recorded as a reference spectrum. Automated analysis then determines characteristic values ​​for the diagnostic parameters of the optimally operating nozzle.

[0057] Regular recording of additional sound spectra during the nozzle's operation, and comparison with the master spectrum and optimal parameter values, serves to assess the nozzle's correct function and the uniformity of the liquid application. Deviations can be corrected via manual or automated adjustment of the nozzle function.

[0058] It should be noted here that high-pressure nozzles are used in automated furniture manufacturing, in a manner known per se, to temporarily apply solvents, release agents, or cleaning agents to edges in edgebanding machines. Production efficiency and cost-effectiveness require a reliable and reproducible process in this regard. The exit of the nozzle jet into the atmospheric environment or ambient pressure generates flow noise in the audible range, which is used analytically for the problem addressed by the invention and for its solution.

[0059] The one in Fig. 1 The recorded spectra are represented by the dashed lines as a similarity function for the turbulent outflow.

[0060] For two-fluid nozzles of the type relevant here, such a similarity function for turbulent outflow describes the intensity profile of the determined spectrum more clearly. In the higher frequency range, the determined sound or sound spectrum corresponds, on the one hand, to the turbulent channel flow along a central axis of the nozzle channel, the turbulent boundary layer between the nozzle channel wall and the turbulent mixing zone, which extends over several millimeters outside the nozzle, where the fast jet flow interacts with the still outside air and atmospheric pressure, leading locally and on a small scale to the shedding of vortex pairs, and, on the other hand, to the fully developed turbulent free jet, where a more large-scale turbulence takes place.

[0061] The spectrum in the low-frequency range with the in the Figure 1The intensity shown is due to the sources of temporal fluctuations in the total mass flow at the nozzle outlet cross-section and temporal fluctuations in the local mass flow at the outlet cross-section, which arise from the uneven absorption and droplet formation of the solvent in the fast, turbulent, low-pressure flow of the nozzle channel. Furthermore, the spectrum is attributable to an alternating pressure field between the fluid and the nozzle channel wall.

[0062] The absorption of the liquid phase in the compressed air at the solvent inlet via the Venturi principle can be uneven, leading to mass density fluctuations along the nozzle channel. These fluctuations manifest as temporal variations in the total mass flow at the nozzle outlet cross-section. Such a monopole source is generally strong and can be estimated from the nozzle geometry. The peak frequency of such a source will be on the order of 100 Hz.

[0063] Droplet formation in the nozzle channel after solvent addition can lead to local, temporal fluctuations in the mass flow at the nozzle outlet cross-section. Dipole-like sound frequencies on the order of 100 Hz to 1 kHz were detected.

[0064] Tests conducted according to the exemplary embodiment ensured that vibrations of the nozzle body were not transmitted to other components via the nozzle's fixing point. This meant that unwanted resonance peaks were avoided.

[0065] In summary, it can be stated that the sound level profile measured in the higher frequency range originates in the turbulent flow of the nozzle exit, the mixing zone and the free jet, and reflects the prevailing average velocity and the strength of the turbulence of the liquid particles in the jet.

[0066] In contrast, the level profile in the low frequency range is informative for the flow in the nozzle channel and the mixing of compressed air and solvent that begins there.

[0067] For the evaluation and relevance of the determined sound spectrum, it is crucial that the fluid in question is a two-phase fluid, which, through the addition of a solvent, acts as a special functional coating fluid for application under Venturi vacuum in the nozzle channel. The velocity and turbulence of the compressed air in the nozzle channel ensure that the gaseous compressed air phase and the liquid solvent phase mix rapidly, and the fluid breaks down into very fine droplets that are carried along by the flow.

[0068] The spectra thus reveal whether there was excessive solvent flow, no solvent flow, or optimal solvent uptake. The switching intensity in the higher frequency range, which originates from the turbulent outflow, increases with both the compressed air volume flow and the solvent flow. The spectrum therefore clearly shows changes in the mixing ratio.

[0069] For comparison, the case where no solvent was added was examined. In this case, the sound generation and the resulting spectrum are solely attributable to turbulent compressed air. The measured switching intensity in the low-frequency range is significantly lower in these cases than in normal operation. This confirms that phase mixing in the nozzle channel makes a substantial contribution to the typical low-frequency spectrum of the sound, and that changes in this range reflect the dynamics and effectiveness of the solvent addition.

[0070] The sound intensity in the higher frequency range increases with both the compressed air volume flow and the solvent flow. The spectra therefore very clearly reflect changes in the mixing ratio.

[0071] The measured switching level spectra according to Figure 1 or Figure 2For essentially optimal nozzle operation, a similarity function for turbulent outflow (dashed lines according to) was used. Figure 1 ) stored.

[0072] The similarity functions for small mass flow (solid line) and large mass flow (dashed line) according to Figure 2 show that reliable peak frequencies for the Strouhal maximum F p ' can be determined.

[0073] To solve the problem of the invention, according to an exemplary embodiment, the broadband frequency spectrum of two-fluid nozzles in the audible range of approximately 16 Hz to 20 kHz was determined as a characteristic fingerprint of an optimally functioning nozzle and thus as a reference in a master spectrum. A shape parameter F was determined from the data for the low-frequency range of 16 Hz to 2 kHz, and a characteristic velocity u of the emerging free jet was determined from the data for the high-frequency range (2 kHz to 20 kHz).

[0074] To monitor and manually or automatically operate, as well as to readjust the functional quality of the two-fluid nozzle during operation, control spectra are determined at regular intervals. These are then compared with the respective master spectrum.

[0075] Deviations in the low-frequency range or in the high-frequency range, or regarding the values ​​of F and u, then lead to targeted changes in the operating parameters of the nozzle until the shape of the master spectrum is achieved again.

[0076] According to the invention, a broadband sound spectrum can be recorded within a few seconds during machine operation and used for automated control or regulation of the corresponding nozzles.

[0077] The Fig. 3 shows a cross-section through a typical nozzle for solvent application in edgebanding machines.

[0078] Assuming an isentropic flow, the pressure profile and flow velocity for the nozzle can be estimated for a typical absolute working pressure of 3 bar.

[0079] Changes occur particularly at the beginning of the nozzle channel, at the widening of the channel or solvent admixture, and in the supersonic shock region that exists between the solvent inlet and the nozzle outlet.

[0080] It has been shown that the flow of compressed air through a typical nozzle for edgebanding machines is approximately isentropic, and furthermore, the air can be considered an ideal, compressible gas. The ratio of the applied working pressure to the atmospheric pressure at the nozzle outlet is so large that the flow velocity at the narrowest point of the nozzle channel, i.e., the throttle, is equal to the speed of sound.

[0081] A typical design of a two-fluid nozzle resembles that of Laval nozzles, featuring a relatively large inlet diameter for the compressed air flow into a narrow throttled nozzle channel. This channel then widens to accommodate the solvent and, in some cases with a conical nozzle opening, is further enlarged. At a preferred operating pressure of 3 bar, the limit for supersonic shock is exceeded in these nozzles. With increasing operating pressure, the flow velocity at the narrowest point of the nozzle no longer increases.

[0082] If the nozzle channel opens after the constriction, the velocity does not decrease there, but continues to increase due to the expansion of the compressed gas. It then reaches the supersonic range with a local coefficient of performance (M) > 1. Furthermore, the expansion causes the local pressure to drop below the ambient pressure on the outlet side.

[0083] The adjustment of the flow pressure to the ambient pressure occurs during a supersonic shock. This shock arises at the point where the pressure on the outlet side, due to the supersonic speed of the flow, no longer extends further into the nozzle channel. In the supersonic shock region, the local pressure rises abruptly to the ambient pressure on the outlet side, and the pressure value immediately drops into the subsonic range with M < 1.

[0084] A further increase in operating pressure shifts the overshock wave further to the right (see Figure 3 ) until it reaches the nozzle outlet. Higher operating pressures create an unstable flow at the outlet, as the shock wave is forced out of the nozzle and broken up.

[0085] Considerations for Laval nozzles can be applied to classic nozzles for edgebanding machines, which is in Figure 3 is shown.

[0086] A typical operating pressure of 2 bar for such nozzles, combined with atmospheric pressure of 1 bar, results in a total pressure of p = 3 bar at the compressed air inlet. The air flows at the speed of sound through the narrow nozzle channel, i.e., the restrictive throttle of the system.

[0087] For an absolute working pressure of p = 3 bar, a pressure drop to a throttle pressure of p* = 1.58 bar occurs at the constriction. For an absolute working pressure of 3 bar, a typical nozzle with an optimal nozzle cross-section used here results in a compressed air mass flow of 70 g per minute.

[0088] From this, the application quantity for use in an edgebanding machine can be determined. Given the machine's belt speed, the applied or applicable layer thickness of the respective liquid can be determined, thus enabling the optimization and reproducibility of the technological processes requiring the use of the nozzle and the application of microparticles.

[0089] The ratio of the diameter d* of the throttle channel DK to the diameter d of the enlarged channel EK is crucial for the flow physics in the nozzle at a given operating pressure. Figure 3 A value of d / d* = 1.1 results in a high exit velocity for the nozzle flow. A value of approximately d / d* = 1.6 creates a large and advantageous vacuum. For optimal nozzle design and its application in the proposed system, a d / d* value in the range of 1.1 to 1.6, preferably between 1.2 and 1.5, should therefore be chosen.

Claims

1. System for the reproducible application of temporary surface cleaning or functional coatings by spraying through one or more pneumatic two-fluid nozzles with nozzle bodies connected to at least one reservoir, wherein the reservoir is filled or fillable with sprayable surface cleaning or functional coating fluid and furthermore with a pressurized gas, in particular a compressed air source, which can be connected to the respective two-fluid nozzle in order to convey the surface cleaning or functional coating fluid according to the principle of a jet pump or injector nozzle, also with Laval effect, and to apply it by spraying onto a surface to be treated, in particular the surface of an edge of a piece of furniture, wherein the respective two-fluid nozzle is designed as a minimum quantity nozzle valve with an actuating device in the nozzle body. characterized by the fact thatA device for determining the acoustic sound level spectrum generated during the spraying process is provided directly on or in the nozzle body, wherein the acoustic spectrum is recorded with regard to the frequency profile of the sound level and fed to a connected computing unit, where it is compared with a calibration or target spectrum and checked for significant deviations, so that the actuating device can be operated, the nozzle replaced and / or maintenance can be carried out to restore the calibration or target spectrum, so that a uniform and reproducible output and application of the surface cleaning or functional coating fluid is ensured over the respective operating period.

2. System according to claim 1, characterized by the fact that The device for determining the acoustic spectrum is a microphone, in particular a piezoelectric transducer.

3. System according to claim 1 or 2, characterized by the fact that the actuating device is in operative communication with an electromechanical actuator.

4. System according to claim 3, characterized by the fact that The actuator is an electronically controlled stepper motor.

5. System according to any of the preceding claims, characterized by the fact that The Strouhal maximum and its distribution or course in the higher frequency range of the spectrum and the fall or fall rate of the respective low frequency peak of the spectrum are used as significant values ​​for the spray jet.

6. System according to claim 5, characterized by the fact that The calibration or target spectrum is specified at the highest possible frequency for the Strouhal maximum to ensure homogeneous turbulence in the spray jet and the lowest possible drop in the low-frequency peak, and is adjusted or readjusted as needed.

7. System according to claim 5 or 6, characterized by the fact thatThe frequency response is determined and recorded using frequency analysis in the range of at least up to 15 kHz.

8. System according to any of the preceding claims, characterized by the fact that To determine a target frequency spectrum specific to each individual case, an optical or optoelectronic analysis of the spray jet is performed, including the distribution of the functional coating particles in the spray jet, and the expected application quantity per unit of time is determined.

9. System according to any of the preceding claims, characterized by the fact that The working pressure of the compressed air source is set to a range of essentially 1.0 - 4.0 bar, particularly preferably to 2 bar, such that the supersonic shock zone, resulting from an opening nozzle channel and expansion of the respective liquid within the nozzle body, is formed.

10. System according to any of the preceding claims, characterized by the fact thatthe distance between the exit of the respective two-component nozzle and the surface to be treated is set to a range between essentially 2.5 - 5.0 cm, in particular essentially 3.0 cm.

11. Use of a nozzle with a throttle channel (DK) adjoining the compressed air inlet (DE), which transitions into an enlarged channel (EK), wherein the enlarged channel (EK) has a liquid inlet (FE) at which a vacuum (DU) is created during operation and with a throttle channel diameter d* and a diameter d of the enlarged channel (EK) further with a ratio of d / d* in the range between substantially 1.1 to 1.6 for a system according to at least one of the preceding claims.

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