WO2005117507A2

WO2005117507A2 - Method for removing at least one inorganic layer from a component

Info

Publication number: WO2005117507A2
Application number: PCT/EP2005/005792
Authority: WO
Inventors: Peter FÖRNSEL; Christian Buske; Uwe Hartmann; Peter Kleinemas
Original assignee: Plasmatreat Gmbh; Hella Kgaa Hueck & Co.
Priority date: 2004-05-28
Filing date: 2005-05-30
Publication date: 2005-12-08
Also published as: WO2005117507A3

Abstract

The invention relates to a method for removing at least one inorganic layer from a component, whereby a plasma jet is produced in a working gas containing a reactive gas by means of an atmospheric discharge, the plasma jet is oriented towards the inorganic layer, the inorganic layer is at least partially melted by means of the plasma jet, and the at least partially melted inorganic layer is removed from the surface by the gas flow of the plasma jet. The inventive method can be used especially for delayering adhesive surfaces of two components, and for machining headlight components. The invention also relates to a device for producing a plasma jet for carrying out the inventive method.

Description

Method for removing at least one inorganic layer from a component

The invention relates to a method for removing at least one inorganic layer from a component, a method for gluing two components, each with an adhesive surface, and a device for generating an atmospheric plasma jet for carrying out the method.

A plasma source is known from the prior art of EP 0 761 415 AI and EP 1 335 641 AI, in which a plasma jet is generated by means of a non-thermal discharge from the working gas by applying a high-frequency high voltage in a nozzle tube between a pin electrode and a ring electrode is generated, which emerges from the nozzle opening. With a suitably set flow rate, this non-thermal plasma jet has no electrical streamer, so that only the high-energy but low-temperature plasma jet can be directed onto the surface of a component. Streamers are the discharge channels along which the electrical discharge energy runs during the discharge.

The surface is thus cleaned of dust particles and activated so that subsequent coating with a liquid, in particular with an adhesive, is possible. The high electron temperature, the low ion temperature and the high gas velocity can also be used to characterize the plasma beam. It is also known from the prior art of EP 1 410 852 that a layer of organic material, for example a lacquer layer, can be removed from a surface with the plasma jet. The organic material is pyrolyzed and / or sublimated at low temperatures. In any case, the detachment processes take place at low plasma intensities and can be carried out with the plasma source described above.

Furthermore, it is known that inorganic layers can be detached using a laser beam. The inorganic layer absorbs a relatively large amount of energy from the laser beam and evaporates. The laser light couples into the vapor phase. The detachment of the inorganic layer is sometimes explosive, so that there is often an irregular detachment of the inorganic layer. The surface treated in this way is sometimes not completely cleaned and cannot be further processed, for example glued, without further pretreatment. This is because the laser beam generates a plasma which at least partially contains ions of the evaporated inorganic material or metal ions. There is therefore no sufficiently high oxygen concentration in the plasma which is required for an oxidic pretreatment and activation of the surface. A separate pretreatment and activation of the surface is therefore necessary as an additional step. Because oxidation products adhere to the surface, which originate from post-oxidation of the heated areas.

An inorganic layer can also be removed by means of a purely mechanical treatment. The inorganic However, the layer is only removed unevenly and surface activation takes place in this step only in exceptional cases.

Since the mechanical detachment of the inorganic layers or the detachment with the aid of a laser beam means only an at least partial cleaning, the adhesive surface to be glued is only prepared for gluing to a limited extent. Because the adhesive surface is only slightly surface activated and usually covered with cracked hydrocarbons, so that a further pretreatment step is required. The surface can be activated on the one hand with chemical means or with the help of an atmospheric plasma beam, as described above.

In contrast, detachment of the inorganic layers with the aid of the plasma source known from the above-mentioned prior art is only insufficiently possible, since a sufficiently excited plasma cannot be generated without individual streamers being blown out of the plasma source. For the generation of a sufficiently intense plasma jet, the flow rates of the working gas have to be increased so far that the electrical discharge streamers ignited to generate the plasma emerge from the outlet opening of the plasma source and come into contact with the surface. This then creates a plasma on the surface that contains ions of the inorganic material or metal ions. The concentration of oxygen ions in the plasma is considerably reduced as a result, so that the detachment of the inorganic layer proceeds unevenly and the activation of the surface is impaired or even prevented. It also comes from creating one further plasma on the surface to be processed for a chemical / physical shielding effect of the protective gas against the plasma jet emerging from the plasma source, so that the latter can no longer reach the surface, at least not to a sufficient extent.

The problems outlined above occur in particular in the production of components from layer materials in which a part of the coating has to be removed again in a targeted manner after a coating. This is necessary, for example, for gluing the component if the uppermost inorganic layer of the component is poorly suited for gluing because of its low adhesion to the base material.

This is particularly the case in the manufacture of headlights and decorative layers. Here, a reflection layer and a protective layer serving as corrosion protection are applied to an electrically insulating boundary layer of a carrier material. Plastics, in particular thermosets and paints, can be used as carrier materials. If the carrier material itself is electrically conductive, an intermediate layer is arranged between the carrier material in order to produce a galvanic separation of the carrier material from the reflection layer. The carrier material consists preferably of metal, preferably of a galvanized steel sheet. The intermediate layer consists of a lacquered, preferably powder-lacquered layer. The reflection layer preferably consists of aluminum, which is sputtered onto the electrically insulating boundary layer. Finally, the protective layer is preferably made of SiO ₂ . The edge area of a headlamp constructed in this way is then connected, in particular glued, to a cover plate. As is known, an aluminum layer coated with Si0 ₂ has little adhesion to the thermoset or lacquer. For this reason, the adhesive surfaces have previously been processed mechanically or with the aid of a laser beam in order to at least partially detach the inorganic layers of aluminum and SiO ₂ . The then released electrically insulating boundary layer can be provided with adhesive so that gluing to the cover plate is facilitated.

The application example shown above of removing an inorganic layer in the manufacture of a headlamp is only one example. The invention described below is not limited to this application, nor is the characteristic layer structure indicated a necessary prerequisite for the application of the invention.

The invention is based on the technical problem of further simplifying and improving the removal of inorganic layers in preparation for further treatment of a component. Another technical problem is to improve the bonding of components with inorganic coatings.

According to a first teaching of the present invention, the technical problem indicated above is solved by a method for removing at least one inorganic layer from a component according to claim 1. With the help of an atmospheric discharge, a plasma jet is generated in a working gas containing a reactive gas, which is directed onto the inorganic layer. The inorganic layer is at least partially melted by the plasma jet and the at least partially melted inorganic layer is removed from the surface by the gas stream of the plasma jet. In this case, a sequence of discharges between two electrodes of a plasma nozzle is preferably generated using a high-frequency high voltage, so that the working gas is excited to a plasma jet emerging from the plasma nozzle.

The term "reactive gas" is understood to mean that the gas is reactive in the plasma state. The property of reactivity, on the other hand, does not necessarily have to be present in the non-excited state, ie in the ground state.

In particular, an oxidizing gas, in particular oxygen-containing gas, preferably air, or a reducing gas, in particular hydrogen-containing gas, preferably forming gas, is used as the working gas. These gases are already reactive in the non-excited state, this property then increases in the plasma state.

In addition, nitrogen can also be used as the working gas, which in the non-excited state has predominantly inert properties, but is reactive in the excited plasma state.

Furthermore, other inert gases, for example argon or helium, can be mixed into the working gas. These gases are not reactive even when excited but contribute to an advantageous increase in the temperature of the plasma.

The high-frequency series of discharges appears as a discharge ^'in the form of an arc discharge, actually consisting of a plurality of individual streamers and not of a constant burning arc.

The method described above makes special use of the properties of the plasma jet in order to detach the inorganic layer. Since the working gas contains a reactive gas, the high electron temperature results in great aggressiveness of the reactive gas within the plasma. This triggers an exothermic reaction between the inorganic material and the reactive gas, although the ignition temperature has not yet been reached. This combustion process releases heat of combustion, which then additionally maintains the combustion process. Thus, with the help of the non-thermal plasma jet at high electron temperatures, despite the low ion temperature, a combustion process of the inorganic material can be generated without the plasma jet itself leading to excessive heating. This is also called cold combustion.

To generate a suitable plasma jet, the plasma nozzle is operated at high frequencies in the range from 1 to 30 kHz. Furthermore, the high power densities are achieved in that the pressure of the working gas and thus the flow rate is increased in order to increase the exit velocity of the plasma jet from the nozzle. This also results in increased cooling of the nozzle head, which is due to the increased Power consumption is necessary without the need for separate cooling, for example water cooling.

The plasma beam is preferably generated as a streamer-free plasma beam. For this purpose, constructive measures are taken, particularly in the nozzle head, to prevent the streamers from escaping. In principle, the nozzle opening is reduced so that, for geometric reasons alone, individual streamers cannot escape together with the plasma jet. However, in order to be able to ensure a sufficiently large flow of the working gas without excessive backflow, a working gas passage is provided according to the invention, the total cross section of which is at least twice as large as the cross section of the nozzle opening.

With the method described above, inorganic layers can be removed. The thickness of the layers to be completely removed depends on the selected boundary conditions. For thicker layers, which may not be able to be completely removed in a plasma coating cut, it is preferred that the surface is pre-processed with a laser beam and a portion of the inorganic layer is removed by the laser beam before treatment with the plasma beam. Pre-cleaning is thus carried out by the laser beam, followed by the aftertreatment, that is to say the removal of the remaining inorganic layer and surface activation by the plasma beam.

The technical problem shown above is solved according to a second teaching of the invention by a method for gluing two components, each with an adhesive surface solved the features of claim 6, wherein at least one adhesive surface has an inorganic coating.

First of all, the inorganic layer is removed from the at least one adhesive surface using the method described above. The adhesive surface freed from the inorganic layer is glued by applying an adhesive and by contact with the further adhesive surface. According to the invention, use is made of the fact that the removal of the inorganic layer also leads to an activation of the adhesive surface, so that the surface is cleaned and activated in one work step. This has particular procedural advantages.

In a preferred manner and not restricting the present invention, the previously described method is suitable for processing a headlight. The headlamp has a layer structure made of at least one carrier material, a reflection layer, and preferably a protective layer. The reflection layer and possibly the protective layer are then removed using the method according to the invention described above and the surface of the carrier material located below is activated.

The carrier material preferably consists of metal, preferably of a galvanized steel sheet. Furthermore, an intermediate layer is preferably arranged between the carrier material and the metal layer, which consists of a lacquered, preferably powder-lacquered layer. The carrier material can also consist of a plastic, in particular a thermoset. The inorganic layer preferably consists of aluminum and the protective layer of SiO ₂ . So with both Alternatives of the carrier material are applied to the aluminum layer on an electrical insulator and thus thermally poorly conductive material.

The section of the headlight freed from the protective layer and the metal layer can then serve as an adhesive surface and can be glued using the previously explained method. If the methods described above are applied to the edge area of the headlight, this edge area can subsequently be glued to a holder without further pretreatment. Further intermediate steps for cleaning and / or activating the adhesive surfaces are not necessary.

The technical problems indicated above are also solved by a device for generating an atmospheric plasma beam with the features of claim 16. This device is particularly suitable for carrying out the method according to the invention.

The device mentioned has a nozzle tube connected to a gas inlet, a nozzle head having a nozzle opening, an irine electrode electrically insulated from the nozzle head, and a working gas passage arranged in the nozzle head and connected to the nozzle tube in terms of flow technology, the tip of the inner electrode being axially opposite to the working gas in the flow direction Nozzle head is arranged set back. According to the invention, the cross-sectional area of the working gas passage is larger than the cross-sectional area of the nozzle opening.

To generate the plasma jet, it is placed inside the nozzle tube and inside the nozzle head a high-frequency alternating voltage in the working gas, which preferably consists of air or forming gas, ignites a discharge, the individual streamer channels of which appear like an arc due to the high frequency. Nevertheless, this arc discharge consists of individual, very short-lasting streamers and not of an ongoing arc. The frequency is for example in the range of over 1 kHz, preferably in the range of 10 to 30 kHz. The frequency is preferably above 20 kHz in order to ensure a particularly high power of the plasma beam. The size of the AC voltage (measured peak to peak, U _ss ) is in the range greater than 0.5 kV, preferably in the range greater than 1 kV kV. A voltage greater than 5 kV is preferred in order to ensure a particularly high power density of the plasma beam.

The nozzle opening has the function of the passage for the plasma jet, that is to say the opening through which the plasma jet generated in the nozzle tube emerges from the nozzle head. This function is supported by the fact that the gas inlet introduces the working gas into the essentially cylindrical nozzle tube in such a way that the gas flow is twisted, that is, a gas vortex is formed. This forces the individual streamers of the discharge into the area of the axis of the nozzle tube. Only at the downstream end of the discharge section, as seen in the direction of flow, does the arc branch and end on an electrically conductive inner surface of the nozzle head. This inner surface can be cylindrical and / or conical. If the nozzle opening is then arranged substantially axially with respect to the axis of the nozzle tube, then the plasma jet strikes the nozzle opening directly and not the working gas passage spaced apart from it. The working gas passage has the function of discharging part of the working gas from the nozzle pipe. This is necessary if the plasma source is operated with a high power density, in particular if the flow rate of the working gas is set significantly higher than the flow rate of the working gas emerging from the nozzle opening with the plasma. So that there is no build-up of the working gas and a disturbance of the flow conditions in the nozzle pipe occurs, the excess part of the working gas is drained through the working gas passage, so that a sufficient flow through the nozzle pipe and the nozzle head can be ensured. In addition, the strong flow through the entire device leads to adequate cooling, in particular of the nozzle head. A separate and complex cooling is then not necessary. It has been shown that when the cross-sectional area of the working gas passage is larger than the cross-sectional area of the nozzle opening, the effects described above occur. This construction means that the plasma jet is concentrated and guided by the surrounding flow through the working gas passage onto the nozzle opening. The flow through the working gas passage can be laminar.

It has also proven to be particularly advantageous that the cross-sectional area of the working gas passage is at least twice, preferably three times as large as the cross-sectional area of the nozzle opening. This ensures that, in comparison to the proportion of the gas quantity emerging through the nozzle opening, the greater part of the working gas emerges from the nozzle head through the working gas passage opening. A higher power density will achieved while cooling is increased.

Another advantage is that the working gas passage surrounds the nozzle opening at least in sections. Form thereby. Support jets of working gas surround the plasma jet emerging from the nozzle opening and accelerate the surrounding air. The nozzle jet thus largely maintains its speed which it has obtained as a result of the acceleration occurring within the nozzle tube, within the nozzle head and within the nozzle opening. Both acceleration effects within the arc and nozzle effects are involved.

In principle, a stable minimum flow of the working gas is required inside the nozzle tube and the nozzle head in order to stabilize the core discharge. By increasing the total amount of working gas, the discharge conditions inside the nozzle tube and the nozzle head are further improved and concentrated.

In terms of production technology and flow technology, it is also advantageous that the working gas passage has a plurality of individual openings. These individual openings can be arranged at least partially around the nozzle opening. Likewise, the individual openings can be arranged at least partially in the side wall of the nozzle head. In addition, the individual openings can be circular, ring-shaped, elliptical or rectangular. The working gas passage can therefore be designed in a wide variety of forms in order to at least partially fulfill its previously described functions. The invention is therefore not limited to one special arrangement or configuration of the working gas passage limited.

Likewise, the shape of the nozzle opening is not limited per se. The nozzle opening is preferably circular, elliptical or rectangular. In addition, the maximum inside dimension of the nozzle opening can be less than 4 mm, preferably less than 3 mm and in particular less than 2 mm. The nozzle opening is intended to ensure that no discharge streamers can escape from the interior of the nozzle tube and the nozzle head. Since the gas throughput, as already explained, is high in order to achieve a powerful plasma jet and the cooling required as a result, there would be the danger with a conventionally designed nozzle opening that individual streamers would escape and come into contact with the inorganic surface. This would significantly impair the removal of the inorganic layer, so that special measures must be taken for the generation of a streamer-free, that is to say potential-free, plasma.

In particular, if individual openings are positioned close to the nozzle opening, there is a risk that the plasma will not seek its way through the nozzle opening, but through one of the individual openings. In order to prevent this, the nozzle opening preferably has a cross section which is larger than the cross section of each of the individual openings. As a result, the flow resistance through the individual opening is increased in comparison to the nozzle opening, which results in a concentration on the central jet through the nozzle opening. Further embodiments of the present invention are explained below using exemplary embodiments, for which reference is made to the attached drawing. Show in the drawing

1 shows a device according to the invention for generating an atmospheric plasma jet for removing an inorganic layer from a component,

2 shows the nozzle head of the device shown in FIG. 1 in cross section,

3 shows the nozzle head of the device shown in FIG. 1 in a front view,

4 shows the nozzle head of the device shown in FIG. 1 in a perspective view,

5 shows a part of a first component with an inorganic layer in cross section,

6, a part of a second component with an inorganic layer in cross section,

7 is a schematic representation of a headlamp with an inorganic coating in cross section,

8 shows the second component during processing with the device according to FIGS. 1 to 4,

9 shows the second component with a partially detached inorganic layer and 10 shows a processing station for carrying out the method according to the invention.

1 to 4 show a device 10 according to the invention for generating a plasma jet for removing an inorganic layer from a component. Before going into the special features of the device according to the invention, a detailed description of the functioning of the device 10 is given below, which is also referred to below as the plasma nozzle 10.

The plasma nozzle 10 shown in FIG. 1 has a nozzle tube 12 which is connected to a nozzle head 14 or is formed in one piece therewith. In the present case, the nozzle head 14 is designed in a special way for generating an intense plasma jet and is explained in more detail below.

The nozzle head 14 consists at least on the inside of an electrically conductive material, in particular a metal. The nozzle tube 12 is also preferably made of metal, but non-electrically conductive materials can also be used. At the end opposite the nozzle head 14, the nozzle tube 12 has a gas inlet 16 for a working gas, for example for compressed air.

Other gases or gas mixtures than air or forming gas are also suitable as working gases. It is preferred that a proportion of a reactive gas is present. For example, a pure oxygen gas, a mixture of a noble gas such as argon and oxygen or a mixture of hydrogen and nitrogen (forming gas) be used. Air is preferred, not least for process engineering reasons, since this working gas is very easily available and often does not require any additional installations.

For the mode of operation of the device 10, it has been found to be very advantageous that the working gas flows through the nozzle tube in the form of a vortex. Nevertheless, the present invention is not limited to the fact that such a vortex is generated during the operation of the device.

In the exemplary embodiment shown in FIG. 1, an intermediate wall 18, which preferably consists of an electrically conductive material, is provided in the device 10 and separates the gas inlet 16 from the interior of the nozzle tube 12. For a targeted admission of the working gas, the intermediate wall 18 has a ring of bores 20 made obliquely in the circumferential direction and thus forms a swirl device for the working gas. The downstream part of the nozzle tube 12 is therefore flowed through by the working gas in the form of a vortex 22, the core of which runs on the longitudinal axis of the nozzle tube 12.

An inner electrode 24 is arranged centrally on the underside of the intermediate wall 18 and projects coaxially into the nozzle tube 12. In the present exemplary embodiment, the inner electrode 24 is formed by a rotationally symmetrical pin rounded off at the tip, for example consisting of copper, which is electrically insulated from the intermediate wall 18 and the other parts of the nozzle tube 12 by an insulator 26. Other embodiments of the inner electrode with the Shown deviating dimensions and even asymmetrically arranged internal electrodes are also possible.

Ultimately, it is only important that the inner electrode 24 is electrically insulated from the nozzle head 14 which acts as the counter electrode. Thus, the partition 18 and / or the nozzle tube 12 itself can also consist of an electrically insulating material.

Via an insulated shaft 28, the inner electrode 24 is connected to a high-frequency transformer 30, which can generate a high-frequency AC voltage. The high-frequency alternating voltage is preferably variably controllable and is - measured peak-to-peak, U _ss - for example 500 V or more, preferably 1-5 kV, in particular also greater than 5 kV.

The frequency is, for example, in the order of magnitude of 1 to 30 kHz or even higher and is preferably also adjustable. The shaft 28 is connected to the high-frequency transformer 30 via a preferably flexible high-voltage cable 32.

The specified values for the size and frequency of the AC voltage therefore have such large ranges that these values depend significantly on the geometry of the device 10 selected. The shape of the voltage curve is also not essential. The AC voltage can therefore be a sinusoidal voltage or a pulsed voltage. The discharge is ignited in the form of an arc 34 between the inner electrode 24 and the nozzle head 14 by the applied high-frequency voltage, the plasma being caused by the high Frequency of voltage is stabilized at low currents. The high frequency of the voltage leads to an interruption of the discharge which occurs in time with the frequency and is thus ignited again and again at the same frequency. With a sinusoidal AC voltage, for example, the process can also be described as a permanent ignition of the discharge in each half-wave.

If there is also a swirling flow of the working gas within the nozzle tube 12, the arc 34 is channeled in the vortex core on the axis of the nozzle tube 12 due to the slight negative pressure and the insulating effect of the gas flow. As a result, the arc 34 branches only in the region of the nozzle head 14 and hits the electrically conductive inner wall there.

The inlet 16 is connected via a hose, not shown, to a compressed air source with variable throughput, which is preferably combined with the high-frequency generator 30 to form a supply unit. The plasma nozzle 10 can thus be moved effortlessly by hand or with the aid of a robot arm. The nozzle tube 12 and the intermediate wall 18 are preferably grounded, provided that they themselves consist of an electrically conductive material.

The working gas, which rotates in the region of the vortex core and thus in the immediate vicinity of the arc 34, comes into intensive contact with the arc 34 and is thereby partially converted into the plasma state. As a result, a plasma jet 36 of an atmospheric plasma, shown in dashed lines in FIG. 1, emerges from the nozzle head 14 through a nozzle opening 38. The plasma jet 36 has approximately the shape of a candle flame. The ion temperature of the plasma jet is low compared to thermal plasmas. For example, a temperature in the plasma jet with a thermocouple PT100 at a distance of 10 mm from the nozzle opening was measured a temperature of less than 300 ° C. This measured value is only explanatory and does not limit the invention.

The plasma jet emerging from the nozzle opening 38 is mainly accelerated before emerging through the pinch effect occurring in the discharge. Likewise, the gas pressure and the nozzle effect can contribute to acceleration when the plasma jet emerges from the nozzle opening. In any case, a high exit speed is achieved. The height

The exit velocity of the plasma jet in turn causes many interactions with the surface to be processed and at the same time a greater range of the plasma jet. Because the impact losses in the plasma jet are lower at high exit speeds.

In addition, a working gas passage 40 is provided in the nozzle head 14 and is connected to the interior of the nozzle tube 12 in terms of flow. The working gas passage 40 serves to pass the working gas which has not been converted into a plasma jet 36 within the nozzle tube 12. According to the invention, it has been recognized that the cross-sectional area of the working gas passage 40 should be larger than the cross-sectional area of the nozzle opening 38 in order to increase the proportion of the working gas which does not emerge from the nozzle head 14 as a plasma jet 36. This results in an increased intensity of the plasma beam 36 as well improved cooling in particular of the nozzle head 14 is achieved.

It has proven to be advantageous that the cross-sectional area of the working gas passage 40 is at least twice, preferably three times as large as the cross-sectional area of the nozzle opening 38. This increases the advantages described above. Because there is less mixing of the core area of the plasma with the working gas.

As shown in FIGS. 2 to 4, the working gas passage 40 surrounds the nozzle opening 38, wherein a plurality of individual openings 42 are provided which form the working gas passage 40 as a whole. The individual openings 42 are arranged in a circle around the nozzle opening, an inner circle and an outer circle of individual openings 42 being provided, in the center of which the nozzle opening 38 is arranged. This symmetrical arrangement has proven to be advantageous since the working gas emerging from the individual openings 42 forms a plurality of support jets 44 which uniformly surround the plasma jet 36. The support beams 44 are shown in FIG. 1 as dotted lines.

However, it is also possible to provide asymmetrical arrangements or distributions of the individual openings 42. This can be selected depending on the application. In particular, the individual openings 42 can also be partially arranged in the side wall 46 of the nozzle head 14.

The shape of the individual openings 42 of the exemplary embodiment shown are round, so that they can be produced in a simple manner through bores. Of course, the individual openings 42 can also have an annular, elliptical, rectangular or any other shape.

Likewise, the shape of the nozzle opening 38 can be circular - as shown in FIGS. 1 to 4 -, elliptical, rectangular or in any other shape. A slot-shaped nozzle opening is also given as an example.

This symmetrical structure is advantageous, but not essential for the configuration of the invention. An asymmetrical arrangement of the nozzle opening relative to the central axis of the plasma nozzle 10 is also possible.

It has also proven to be advantageous that the maximum inside dimension of the nozzle opening 38 is less than 4 mm, preferably less than 3 mm and in particular less than 2 mm. This ensures that, even with high gas throughputs of the working gas, no discharge streamers can emerge from the nozzle head. This ensures the potential freedom of the plasma jet.

1 to 4, the nozzle opening 38 has a cross section that is larger than the cross section of each of the individual openings 42. This measure means that the plasma jet 36 passes through the nozzle opening 38 and not through one of the individual openings 42. It can thus be ensured that the device always works in the same way, in particular that the plasma beam 36 always runs from the center on the central axis of the device 10 exits. Furthermore, the plasma beam 36 is always surrounded in the same way by the support beams 44.

1 and 2 also show that bores 48 and 50 are provided in the nozzle head 14, which on the one hand have the nozzle opening 38 on the front of the nozzle head 14 and on the other hand the individual openings 42 of the

Form working gas passages 40 and fluidically connect them to the nozzle tube 12. It has again proven advantageous that the bores 48 and 50 have a length that corresponds to at least four times the diameter of the bores 48 and 50. The length of the bores 48 and 50 favors the heat transfer between the nozzle head 14 and the working gas and thus improves the cooling of the nozzle head 14. This in turn results in less wear on the nozzle head.

The bores 48 and 50 end - as shown in FIGS. 1 and 2 - on the inside of the nozzle head 14 facing the nozzle tube 12 on a conically tapering surface 52. The cone reduces the occurrence of additional gas vortices. This design favors the effect described above that the plasma jet 36 passes through the nozzle opening 38 provided for this purpose and not through one of the individual openings 42. The same applies to the fact that a cylindrical surface 54 is arranged within the nozzle head 14, which adjoins the conically tapering surface 52.

The following describes the method for removing an inorganic layer, the method for gluing two components and the method for processing a headlight. First, two exemplary embodiments of components with one inorganic layer shown, the processing of which is explained with reference to FIGS. 7 to 10.

FIG. 5 shows a first exemplary embodiment of a component 60 which consists of a layer 62 made of a carrier material made of plastic, in particular of a thermoset. A further layer 64 made of a metal, in particular aluminum, is arranged on the layer 62. The aluminum is preferably applied by sputtering during manufacture. This layer 64 is in turn provided with a protective layer 66, for example made of SiO ₂ , which prevents the layer 64 from corroding.

FIG. 6 shows an alternative construction of a component 60, in which the carrier material of the layer 62 consists of a metal, preferably a galvanized steel sheet. Furthermore, as already described, the metal layer 64 and the protective layer 66 are provided. Since a smooth layer must be present for the sputtering process, the one shown in FIG

In the exemplary embodiment, an electrically and also thermally insulating intermediate layer 68 is arranged between the carrier material of the layer 62 and the metal layer 64, which preferably consists of a lacquered, preferably powder-lacquered layer.

A layer structure according to FIG. 5 or FIG. 6 is characteristic of reflective components such as headlights, mirrors or other optical or shiny decorative elements. 7 shows an example of a headlight 70 in cross section in schematic form. The headlight 70 has a layer structure according to FIG. 6. 5 can also be used. The layer structure extends over the three-dimensional shape of the headlight 70. An opening is shown at the lower end of the recess 72 of the headlight 70 in which the illuminant of the headlight 70 can be arranged.

8 shows the method for removing an inorganic layer from a component 60 in schematic form. The following explains how a total of two layers, namely the protective layer 66 and the metal layer 64, are removed from the component 60. This serves to explain the special application for a headlight. Of course, the method can also be used to remove only one layer, provided that the carrier material of layer 62 is only coated with an inorganic layer. For example, this could exclusively be the metal layer 64, which is not provided with a protective layer, such as, for example, chrome-plated plastic components.

As shown in FIG. 8, a plasma jet 36 is generated with the aid of an atmospheric discharge in a working gas containing oxygen. For this purpose, a device 10 is used, for example, which was explained above with reference to FIGS. 1 to 4. 8 only the nozzle head 14 is shown as a section of the device 10.

The plasma beam 36 is directed — in the present case together with the support beams 44 — onto the inorganic layer consisting of the metal layer 64 and the protective layer 66. The plasma beam 36 transfers the chemical energy, which is also in the surface due to the high electron temperature due to the high electron temperature, to the surface of the inorganic layers 64 and 66. The transferred energy melts and sublimates at least partially the inorganic layer. A combustion process can even be started, which releases energy itself and increases the combustion. This causes the inorganic material to melt and evaporate further. The inorganic layer thus melted or melted is then blown away and removed from the surface by the gas stream of the plasma jet itself and possibly by the stream of the working gas emerging through the working gas passage.

As a result of this process, the inorganic layer is completely removed without the carrier material 62 or the intermediate layer 68 being attacked on account of their low thermal conductivity and their thermoset plasticity. In addition, the surface is activated so that it can be easily wetted with a liquid for further processing. In contrast to ablation by a laser beam, the hydrocarbons released react and do not condense next to or on the treatment track.

9 then shows the layer structure of the component 60 after complete processing by the plasma jet. The upper two layers 64 and 66 have been removed in the machined area of the surface, while the intermediate layer 68 and the carrier material 62 have remained almost unchanged.

The method described above can be used above all for the removal of relatively thin inorganic layers. In the case of thicker inorganic layers, the layer can be burned in, which in itself need not be disadvantageous, but is not the aim of the process. Therefore, preparation is recommended through a laser beam. It is therefore further proposed that the surface of the component is processed with a laser beam before the treatment with the plasma beam and that part of the inorganic layer is already removed by the laser beam. The laser beam does a rough preparatory work, while the plasma beam does the fine work.

This process is shown schematically in FIG. 10 using a processing station. The component 60 is moved relative to the processing station, which has a laser 80 and a plasma source 82, such as the plasma nozzle 10 according to FIGS. 1 to 4. During the relative movement, the surface of the component 60 is first processed with the laser beam 81 of the laser 80, as a result of which a substantial proportion of the inorganic layers 64 and 66 is removed. However, residues remain on the surface of the intermediate layer 68, which means that it is not completely cleaned.

Due to the further relative movement of the component 60 to the processing station, the surface is then processed by the plasma jet 83 of the plasma source 82, as a result of which the remaining residues of the inorganic layer are removed and the surface cleaned in this way is activated.

The method for gluing two components, each with an adhesive surface, is described below on the basis of the previously described stripping method. At least one adhesive surface of the two components initially has an inorganic coating. This is removed from the at least one adhesive surface in accordance with the method previously described with reference to FIGS. 8 and 9. Then the from the inorganic layer freed adhesive surface by applying an adhesive and glued by contact with the other adhesive surface.

FIG. 10 shows this process again. As has been described above, the surface, here the adhesive surface of the component 60, is first cleaned and activated by the laser beam 81 of the laser 82 and the plasma beam 83 of the plasma source 84. During the further movement of the component 60 relative to the processing station, an adhesive layer 86 is applied by means of an application device 84. The adhesive layer 86 can wet the largely cleaned and activated surface well and thus build up sufficient adhesion. Subsequently, the further component, which is not shown in FIG. 10, is brought with its adhesive surface into contact with the adhesive surface of the component 60 provided with the adhesive layer 86. After the adhesive has hardened, a permanent and reliable adhesive connection results.

The multi-stage method described above can be used in particular for machining a headlight.

The headlight 70 has - as has been described with reference to FIG. 7 - a layer structure composed of at least one carrier material 62, possibly an intermediate layer 68, a reflection layer 64 made of a metal and possibly a protective layer 66. At the edge area 74 of the headlight 70, the adhesive surface is arranged, which is to be glued to an adhesive surface of a cover plate.

The problem here is that the adhesive surface 74 with the protective layer 66 or possibly only with the metal layer 64 is provided, which in itself has poor adhesion to the paint.

If the adhesive surface 74 is now processed with the method shown in FIG. 10 in such a way that the protective layer and the reflection layer are removed at least in sections and the exposed surface is provided with an adhesive, the adhesive surface 74 can be bonded very well to the adhesive surface of the cover pane ,

Claims

PATENT CLAIMS

1. A method for removing at least one inorganic layer from a component in which a plasma jet is generated with the aid of an atmospheric discharge in a working gas containing a reactive gas, in which the plasma jet is directed onto the inorganic layer, in which the inorganic layer through the Plasma jet is at least partially melted and the at least partially melted inorganic layer is removed from the surface by the gas stream of the plasma jet.

2. The method of claim 1, wherein a sequence of discharges between two electrodes of a plasma nozzle is generated using a high-frequency high voltage and the working gas is partially excited to a plasma emerging from the plasma nozzle.

3. The method according to claim 1 or 2, wherein the plasma jet is generated as a stream-free plasma jet.

4. The method according to any one of claims 1 to 3, in which an oxidizing gas, in particular oxygen-containing gas, preferably air, or a reducing gas, in particular hydrogen-containing gas, preferably forming gas, as the working gas, or a gas containing nitrogen is used.

5. The method according to any one of claims 1 to 4, wherein the surface is processed with a laser beam before the treatment with the plasma beam and part of the inorganic layer is removed by the laser beam.

6. A method for gluing two components, each with an adhesive surface, at least one adhesive surface having an inorganic coating, in which the inorganic layer is removed from the at least one adhesive surface using a method according to one of claims 1 to 5, and in which the inorganic layer freed adhesive surface of one component is glued by applying an adhesive and by contact with the adhesive surface of the other component.

7. The method according to claim 6, wherein the adhesive surface is activated during the detachment of the inorganic layer.

8. A method for processing a headlamp in which the headlamp has a layer structure of at least one carrier material and a reflection layer and in which the reflection layer is removed at least in sections with a method according to one of claims 1 to 5.

9. The method according to claim 8, wherein the reflection layer consists of aluminum.

10. The method according to claim 8 or 9, wherein a protective layer is provided on the reflection layer, which is removed at least in sections with the reflection layer.

11. The method according to claim 10, wherein the protective layer consists of Si0 ₂ .

12. The method according to any one of claims 8 to 11, wherein the carrier material consists of metal, preferably of a galvanized steel sheet.

13. The method according to claim 12, wherein an electrically insulating intermediate layer is arranged between the carrier material and the metal layer, which consists in particular of a painted, preferably powder-coated layer.

14. The method according to any one of claims 8 to 11, wherein the carrier material consists of a plastic, in particular a thermoset.

15. The method according to any one of claims 8 to 14, wherein the portion of the component freed from the metal layer and optionally the protective layer serves as an adhesive surface and is bonded using a method according to one of claims 6 or 7.

16. Device for generating an atmospheric plasma jet, in particular for carrying out the method according to one of claims 1 to 15, with a nozzle tube (12) connected to a gas inlet (16), with a nozzle head (14) having a nozzle opening (38), with an inner electrode (24) which is electrically insulated from the nozzle head (-14) and with a working gas passage (40) arranged in the nozzle head (14) and connected to the nozzle tube (12) in terms of flow technology. , wherein the tip of the inner electrode (24) in the flow direction of the working gas is axially offset from the nozzle head (14), characterized in that the cross-sectional area of the working gas passage (40) is larger than the cross-sectional area of the nozzle opening (38).

17. The apparatus according to claim 16, characterized in that the cross-sectional area of the working gas passage (40) is at least twice, preferably three times as large as the cross-sectional area of the nozzle opening (38).

18. The apparatus according to claim 16 or 17, characterized in that the working gas passage (40) surrounds the nozzle opening (38) at least in sections.

19. Device according to one of claims 16 to 18, characterized in that the working gas passage (40) has a plurality of individual openings (42).

20. The apparatus according to claim 19, characterized in that the individual openings (42) are at least partially arranged around the nozzle opening (38).

21. The apparatus according to claim 19 or 20, characterized in that the individual openings (42) are circular, ring-shaped, elliptical or rectangular.

22. Device according to one of claims 16 to 21, characterized in that the nozzle opening (38) is circular, elliptical or rectangular.

23. Device according to one of claims 16 to 22, characterized in that the maximum inner dimension of the nozzle opening (38) is less than 4 mm, preferably less than 3 mm and in particular less than 2 mm.

24. Device according to one of claims 19 to 23, characterized in that the nozzle opening (38) has a cross section which is larger than the cross section of each of the individual openings (42).

25. Device according to one of claims 19 to 24, characterized in that bores (48, 50) are provided in the nozzle head (14) which connect the nozzle opening (38) and the individual openings (42) with the nozzle tube (12) in terms of flow.

26. The device according to claim 25, characterized in that the bores (48, 50) have a length which corresponds to at least four times the diameter of the bores (48, 50).

27. The device according to claim 25 or 26, characterized in that the bores (48, 50) end on the inner side facing the nozzle tube (12) on a conically tapering surface (52).

28. The apparatus according to claim 27, characterized in that a cylindrical surface (54) is arranged within the nozzle head (14), which adjoins the conical surface (52).