Plasma treatment installation for containers, and method for the plasma treatment of containers

Abstract

The invention relates to a plasma treatment installation for containers (1), in particular PET bottles, the installation comprising a plurality of treatment stations (2) which are attached to a movably drivable support assembly, wherein the treatment stations (2) each have an optical emission-detection device which is designed, using an associated evaluation device (13), to measure radiation emitted in a plasma process. According to the invention, a reference light source (6) is provided, which is designed to irradiate the optical emission-detection devices which are guided past by the support assembly. The invention also relates to a method for the plasma treatment of containers (1).

Description

[0001] Plasma treatment plant for containers and process for plasma treatment of containers

[0002] The invention relates to a plasma treatment system for containers, in particular PET bottles, comprising a plurality of treatment stations mounted on a movably drivable support assembly. Each treatment station comprises an optical emission detection device configured, together with an associated evaluation device, to measure radiation emitted in a plasma process. The invention further relates to a method for plasma treatment of containers, in particular using the aforementioned plasma treatment system.

[0003] In the beverage industry, as well as for other liquid or pasty products, plastic containers, especially plastic bottles, are commonly used. Bottles made of PET (polyethylene terephthalate) are widely used, as they are characterized by good functional properties, including good recyclability.

[0004] Although PET already has good barrier properties compared to many other plastics, there is a need to further improve the barrier properties for sensitive products or those with particularly high quality requirements. For this purpose, it is known to provide the container wall with an inner barrier layer. This can be thin layers of hydrocarbon compounds or thin quartz-like layers, particularly based on SiO. xbe provided (see “Blow molding of plastic bodies”, second, updated edition 2022, Michael Thielen, Klaus Hartwig, Peter Gust, ISBN 978-3-446-45552-8, pages 211 to 213).

[0005] Corresponding devices and methods are also described in EP 3 433 395 B1, DE 10225609 A1 and WO 03 / 100120 A2.

[0006] It is also known that the plasma process takes place in multiple stages or with multiple plasma pulses, whereby different pressures and / or different process gases can be used. For example, surface cleaning and activation, the application of an intermediate layer as an adhesion promoter, or similar steps can also be provided.

[0007] In order to monitor the plasma process using comparatively simple means, it is known to measure the radiation emitted during the plasma process. The measurement can generally be carried out temporally or wavelength-integrated or resolved, which allows for different conclusions. A generic plasma treatment system according to the preamble of patent claim 1 is known from EP 2 545 196 B1.

[0008] According to EP 2 545 196 B1, a plurality of treatment stations are mounted on a movably drivable support assembly in the form of a carrier wheel. The treatment stations each have a closable reactor cavity. At a receiving section, the containers, particularly in the form of PET beverage bottles, are inserted into the open reactor cavities, which are subsequently closed. Suitable process gases are then introduced into the containers at a reduced pressure, generating plasma in the closed reactor cavities using microwaves or microwave pulses.

[0009] The optical detection devices each have an optical fiber that captures at least a portion of the radiation emitted during the plasma process and guides it to a photodiode. An evaluation device then analyzes the emitted light, enabling process control with comparatively simple means.

[0010] The treatment stations each have an associated optical emission detection device, which is therefore moved as a component of the respective treatment station by the carrier wheel together with the associated reactor cavity.

[0011] In the event of a faulty plasma process, the measured values ​​of the emitted radiation deviate from the specified values, so that, as required, for example, corresponding containers are sorted out and / or the plasma process is adjusted and / or further troubleshooting is planned.

[0012] The present invention is based on the object of improving optical monitoring in a plasma treatment system for containers. In particular, the optical monitoring should be more efficient, precise, and reliable. Furthermore, a corresponding method for the plasma treatment of containers should be specified.

[0013] The subject matter of the invention and the solution to the problem are a plasma treatment system for containers according to patent claim 1 and a method for the plasma treatment of containers according to patent claim 11.

[0014] Accordingly, in a plasma treatment system for containers, in particular PET bottles, according to the preamble of claim 1, the invention provides for at least one reference light source, which is configured to irradiate the optical emission detection devices guided past the support assembly. During operation, the treatment stations are moved with the support assembly, with the reference light source then being arranged in a stationary manner, in particular, so that the optical emission detection devices can be guided past them with the support assembly.

[0015] Within the scope of the invention, the term "treatment station" refers in particular to an assembly with which exactly one container is treated at a time. Within the scope of the invention, it is also possible to combine several, for example, two or four, treatment stations into a module. Such a module can then group the multiple treatment stations together, and common connections, lines, or the like can also be provided for the module.

[0016] In this context, the present invention is based on the realization that the emission detection devices provided for each treatment station and also, if applicable, the associated evaluation devices may be subject to a certain aging, which may change the sensitivity for measuring the radiation emitted in the plasma process.

[0017] According to a preferred embodiment of the invention, the emission detection devices can, for example, comprise an optical waveguide. Optical waveguides can age, for example, due to moisture, UV radiation, and mechanical stress, to such an extent that the transmission and aperture decrease over time. With an unchanged plasma process, the measurement signal with respect to the emitted radiation decreases accordingly.

[0018] Corresponding aging processes can also occur in other possible components of the emission detection device such as optics, in particular lens optics, photo elements and also downstream electronic components of the evaluation device in the form of diodes, resistors or electronic components.

[0019] It should also be noted that the aging of the optical detection devices and associated evaluation devices of the various treatment stations can occur differently, resulting in a certain statistical scatter.

[0020] In this context, the reference light source allows the determination of correction parameters for the emission detection devices and associated evaluation devices of the various treatment stations.

[0021] The reference light source essentially constantly emits light of a specified wavelength or spectrum, so that all passing optical emission detection devices are illuminated equally. Different measured values ​​of the emitted radiation for the treatment stations and thus the respective emission detection devices and evaluation devices then reveal a different sensitivity of the optical detection devices in combination with the associated evaluation devices. This different sensitivity can also be caused, in particular, by the aging described above.

[0022] Within the scope of the invention, it is then possible to determine correction parameters which compensate for the different sensitivities and thus enable a very precise determination of the emitted radiation even when the components age.

[0023] It is clear that the constant or essentially constant emission of the reference light source allows the optical detection devices to be calibrated relative to each other with the associated evaluation devices of the various treatment stations, allowing differences in plasma generation at the individual treatment stations to be determined with very high accuracy. It is understood that the reference light source should be operated with an essentially constant reference emission, although, for example, a power supply with a constant current source is possible.

[0024] If the reference light source is subject to only minor fluctuations over the long term, corrections in the sense of absolute calibration are also possible. For example, light sources are known that allow precisely adjustable emission even over the long term. Suitable light sources are marketed, for example, by the company Admesy BV, Netherlands, under the name "Steropes-LED lightsource."

[0025] Relative calibration allows deviations between the various treatment stations to be detected with very high accuracy. This makes it possible to determine if the plasma process is not running properly at individual treatment stations, for example, leaks could be the cause.

[0026] Global or absolute calibration also allows for influencing factors that affect all treatment stations equally to be taken into account. Examples of such influencing factors include deviations in vacuum generation, gas supply, and similar factors.

[0027] The invention not only enables more precise and reliable process monitoring, allowing corresponding limit values ​​for optical process detection to be defined more precisely, thus also reducing the variation in coating quality. Additionally or alternatively, further optimization of the plasma process is possible.

[0028] In this context, there is also the advantage of reducing the risk of false positives or false negatives when rejecting bottles. This means there is a lower risk that properly coated bottles will be identified as rejects or that actually defective containers will be correctly classified.

[0029] In addition, the aging of the optical detection devices and the associated evaluation devices can be accepted because corresponding influences can be compensated for by the correction parameters within the scope of the invention. Even if significant aging influences already occur and the sensitivity of the optical detection varies considerably between different treatment stations, a significantly longer service life is possible by determining the associated correction parameters.

[0030] Additionally or alternatively, it is also possible to use more robust and / or more cost-effective components, which may be subject to a certain degree of wear within the scope of the invention.

[0031] According to the invention, all optical detection devices with the associated evaluation devices can be checked and corrected using a single fixed reference light source. The optical emission detection devices are guided past the reference light source, so that the reference measurement values ​​for each treatment station can be recorded as a measurement curve, particularly depending on time and / or angle.

[0032] The recorded measurement curve can be evaluated and analyzed differently depending on the constellation.

[0033] The reference light source can be designed as an LED or an LED arrangement, wherein the reference light source preferably has a certain radiation angle so that light emitted by the reference light source in an oblique direction can also be recorded by the optical emission detection devices guided past.

[0034] In the case of beam-like light propagation emanating from the reference light source, signal detection would only occur if the reference light source on the one hand and the optical detection devices passing by on the other hand are precisely aligned and positioned exactly opposite each other.

[0035] According to a preferred embodiment of the invention, it is provided against this background that the reference light source has a radiation angle which is larger than an aperture of the emission detection device and / or that the reference light source is designed as an extended linear or planar radiation source.

[0036] Within the scope of such a design, with a correspondingly large linear or planar extension or a correspondingly large radiation angle of the reference light source, it can be ensured that radiation emitted by the reference light source can be recorded over the entire detection cone predetermined by the aperture of the emission detection device.

[0037] When the emission detection devices are then moved past the reference light source, a characteristic measurement curve is obtained with a rising edge, a maximum value, and a falling edge. The exact shape of the measurement curve depends in detail on the radiation characteristics of the reference light source and the detection cone or detection sensitivity of the emission detection device. While the exact relationships can be considered and, if necessary, determined for each specific setup, it is generally clear that, under the aforementioned boundary conditions, the width of the measurement curve correlates with the aperture of the emission detection devices.

[0038] If the aperture of the optical emission detection device, which in particular comprises an optical fiber, decreases due to aging, this leads to a narrower width of the measurement curve determined, in particular, as a function of time and / or angular position. With knowledge of the movement speed, it is of course possible to convert the time axis into an angular position and vice versa.

[0039] A reduction in the transmissivity of the optical fiber, on the other hand, can be determined in particular by the fact that the height of the measurement curve decreases overall.

[0040] By means of suitable mathematical methods, influences caused by a reduction in the aperture and a reduction in the transmissivity or, in general, the sensitivity of the combination of emission detection device and evaluation device can be distinguished from one another in a light guide, at least to a certain extent.

[0041] With this in mind, one or more correction parameters can be determined and stored for each treatment station. For example, one correction parameter can be provided for the transmissivity and one for the aperture.

[0042] Such a distinction can also be useful because the emission during the plasma process can vary significantly for containers of different sizes and / or shapes. With a different size and / or shape, the plasma is generated in a correspondingly different volume, so that different emissions also result along the detection cone of the optical emission detection devices for different containers. Depending on the arrangement of the optical emission detection device, a reduction in the aperture can be particularly important, especially for large containers, because previously detected areas with relevant emission can then no longer be detected during plasma generation.

[0043] For correspondingly small containers, however, it is possible that a reduction in the aperture may not have a significant impact, because even then, essentially the entire emission along the viewing direction can still be captured. A precise consideration of the optical conditions also depends on the volume of the plasma as well as the precise geometry and, in particular, the arrangement of the optical emission detection device.

[0044] Against this background, according to a preferred embodiment of the invention, it is possible to determine different correction parameters for containers of different shapes and / or sizes. It is known to provide different default values ​​for containers of different shapes and / or sizes in a machine control system. Such different default values ​​are also referred to in practice as a machine recipe. Corresponding machine recipes can therefore also include different correction parameters for optical emission detection.

[0045] The emission detection device can be aligned or arranged differently with respect to the respective associated treatment station. In a typical design of the plasma treatment system, containers, particularly in the form of PET bottles, are aligned vertically with a longitudinal axis. It is particularly expedient if the container opening is arranged at the bottom and the base at the top. With respect to the vertical alignment, the viewing direction of the optical emission detection device can be lateral, i.e., horizontal, or vertical.

[0046] In order to achieve the most complete detection of the light emitted in the plasma process, detection along a vertical line of sight is particularly advantageous because common containers in the form of PET bottles have a greater height than width.

[0047] The challenge arises that, with regard to the described arrangement, the optical detection device must be arranged either in the area of ​​the microwave coupling or in the area of ​​the fluid connections.

[0048] According to a particularly preferred embodiment of the invention, detection takes place along a vertical viewing direction, wherein the optical emission detection device is arranged above the respective container under consideration and then, in the described orientation, the measurement of the radiation emitted in the plasma process takes place through a bottom of the container.

[0049] In principle, however, a side view or a view from below is also possible.

[0050] Within the scope of the invention, the at least one reference light source must be arranged in such a way that it can illuminate the emission detection device in a suitable manner.

[0051] The treatment stations typically each have a sealable reactor cavity for accommodating and treating a single container. Plasma generation occurs when a container is accommodated and the reactor cavity is closed. Loading and unloading of the reactor cavity occurs while it is open.

[0052] Against this background, it is particularly expedient if the stationary reference light source is arranged in such a way that it engages in the area of ​​the open reactor cavity as the optical emission detection devices are guided past. This can also ensure that the reference light source is located exactly where the emission occurs in the plasma process, so that geometric considerations regarding different light propagation are less significant. With regard to the closable reactor cavity, against this background, it is also particularly preferred if the optical emission detection direction is not moved during a corresponding opening and closing movement. In particular, comparable conditions then arise when generating a plasma and a closed reactor cavity, as well as when guiding past the reference light source and an open reactor cavity.

[0053] As part of the measures described, it is necessary that the reactor cavity is open so that the reference light source can be arranged on the part of the movement path of the treatment stations where plasma generation would otherwise take place.

[0054] In a preferred embodiment, the support arrangement is designed as a support wheel on which the treatment station is arranged. The support wheel can then be driven in rotation, whereby the containers can be inserted from the outside when the treatment station, and in particular when the reactor cavity, is open, and removed again after treatment. The treatment stations are then attached to the support wheel radially inward. The reference light source can then easily be arranged radially outward when the treatment stations, and in particular when the reactor cavities, are open.

[0055] The reference light source can, for example, be mounted radially outwardly to the support arrangement and then engage in the open treatment stations or reactor cavities.

[0056] Against this background, a preferred embodiment of the invention provides that, relative to a predetermined direction of movement of the support assembly, the reference light source is arranged behind a delivery section and in front of a container feed section. The treatment stations are then open for the transfer of the containers and are also empty between the delivery section and the feed section. It is then also possible for the reference light source to be permanently installed at the corresponding position.

[0057] The reference light source represents a comparatively simple means of enabling the determination of correction parameters or calibration for all treatment stations with regard to optical detection. The reference light source can therefore be permanently mounted, allowing for continuous monitoring and, if necessary, adjustment. In principle, it is also possible to upgrade existing plasma treatment systems using this method.

[0058] Furthermore, it is also possible that the reference light source is arranged only for the purpose of maintenance or inspection, in which case a reference light source can in principle also be used universally as a maintenance accessory in different places and with different systems.

[0059] Even if continuous monitoring and, if necessary, adjustment is advantageous, the determination of suitable correction parameters can also be carried out at somewhat longer time intervals, so that in principle corresponding measures are only considered during maintenance work or other control intervals.

[0060] The previously described arrangement of the reference light source behind the discharge section and in front of the feed section is particularly preferred, although, especially for the determination of correction parameters in a maintenance operation, the arrangement of the reference light source at a different location is possible if the treatment stations there are open during the maintenance operation.

[0061] As explained above, within the scope of the invention, optical emission detection devices and associated evaluation devices can also be used in the plurality of treatment stations, which differ significantly in their actual sensitivity, which is why wear and ageing can be accepted and compensated for to a greater extent.

[0062] The associated advantages in terms of investment and maintenance costs naturally also depend on the number of treatment stations. Against this background, it should be noted that a larger number of treatment stations is particularly beneficial for increasing the efficiency of the plasma treatment system.

[0063] Within the scope of the invention, for example, 20 to 150, in particular 40 to 120, preferably 48 to 96 treatment stations can be provided.

[0064] According to EP 2 545 196 B1, radiation emitted during the plasma process is evaluated to a particular extent in a wavelength range above 500 nm. The measures described in EP 2 545 196 B1 have proven successful in practice and allow for comparatively reliable monitoring of the plasma process.

[0065] Against this background, according to a preferred embodiment of the invention, the reference light source, in particular in the form of at least one LED or an LED arrangement, emits light in a wavelength range from 600 nm to 1000 nm, in particular 600 nm to 850 nm. The emission can occur as a spectrum or in the form of predetermined emission lines. In principle, it may be sufficient if a simple diode emits light only in a suitable wavelength range that is particularly meaningful for the analysis. For example, with an LED or an LED arrangement, emission at a wavelength of 680 nm can be provided as an example.

[0066] The measurement of the radiation emitted in the plasma process can be integrated or resolved over time or according to wavelength. Integration in this sense can also be achieved by defining relevant time windows or wavelength ranges, for which optical filters can also be used. To enable the simplest possible measurement, it may be sufficient to integrate the radiation emitted in the plasma process over the entire treatment process of a container, although a time-resolved determination is also possible in principle. A time-resolved analysis can be particularly useful when different treatments take place in a coating cycle and need to be monitored or analyzed separately.

[0067] The invention also relates to a method for the plasma treatment of containers, in particular using the plasma treatment systems described above. In this method, containers are picked up in a movable treatment station in a production facility, treated with a plasma, in particular coated, and subsequently discharged. The treatment stations have optical detection devices with which light emissions from the plasma occurring during the plasma treatment are recorded and evaluated. The optical detection devices are additionally illuminated by a reference light source, and reference measurement values ​​are determined in the process. Using the reference measurement values, individual correction parameters are then determined for each treatment station.

[0068] According to a preferred embodiment of the invention, the determination of the reference measurement values ​​can be carried out during actual production. Automatic monitoring and, if necessary, adjustment then take place, so that even short-term changes in the optical emission detection devices can be detected and—where possible—compensated for by determining suitable correction parameters. It may, of course, be expedient to smooth and / or average several consecutive measurements for statistical reasons on the recorded measurement curve. Corresponding mathematical methods are known to those skilled in the art.

[0069] Within the scope of the invention, the provision of the reference light source achieves a certain degree of brightness adjustment. It is understood that the emission of the reference light source—as previously explained—should be as consistent as possible and preferably also defined, thus enabling at least a relative calibration of the various treatment stations to one another and, if necessary, also an absolute calibration.

[0070] Within the scope of the method, the reference measurement values ​​are preferably recorded as a measurement curve as a function of time and / or angular position, whereby an integral and / or a maximum value and / or a curve width are determined for each measurement curve, and / or values ​​in a predefined grid from the measurement curve are used for evaluation. It is understood that a certain amount of noise suppression is applied or an offset is subtracted. The course of the measurement curve is then essentially attributable to the emission of the reference light source when determining the reference measurement values.

[0071] The measures described allow a particularly precise determination of the light emission occurring during plasma treatment, although further controls and optimizations are also conceivable.

[0072] For example, it is also possible to determine a signal from the optical emission detection devices in the area of ​​the reference light source when the source is switched off. Typically, only typical noise will be expected in this case. However, through appropriate measurement or control, it is then possible to exclude or identify theoretically conceivable systematic errors such as recurring reflections or the like and to take them into account in further calculations. It should be noted that the plasma treatment system consists largely of metallic components, and rotation or movement of the treatment station may result in unforeseeable light refraction and reflections.

[0073] As already explained above, within the scope of the invention, reference measurement values ​​can also be determined directly during production. Taking into account the typical speeds of the plasma treatment system, reference measurement values ​​can then be determined per second for, for example, 4 to 50, in particular 5 to 13, treatment stations as described above.

[0074] Within the scope of the invention, particularly reliable and accurate detection of the radiation emitted in the plasma process is made possible by providing a single reference light source, which is arranged in a fixed position and then illuminates the optical emission detection devices passing by. However, it is also conceivable to use more than one reference light source in the manner described. Multiple reference light sources can differ, for example, in terms of their brightness, extension, wavelength, and radiation characteristics.

[0075] The invention is explained below with reference to the figures. They show:

[0076] Fig. 1 is a schematic view of a plasma treatment plant, particularly for the internal coating of PET bottles,

[0077] Fig. 2 a treatment station of the plasma treatment plant,

[0078] Fig. 3 a longitudinal section in the area of ​​a coupling channel of the treatment station,

[0079] Fig. 4 a detailed view of an open treatment station in the area of ​​a fixed reference light source,

[0080] Fig. 5 Curves of reference measured values ​​for different, consecutive treatment stations as a function of a rotation angle,

[0081] Fig. 6 shows two exemplary curves corresponding to Figure 5 after aging of the plasma treatment system.

[0082] Fig. 1 shows a plasma treatment system for containers 1 in the form of PET bottles with a plurality of treatment stations 2, which are attached to a movably drivable support arrangement in the form of a support wheel 3.

[0083] The containers 1 are transferred to the treatment stations 2 at a receiving section 4 relative to a predetermined direction of movement B of the support wheel 3, are subsequently provided with an internal coating by a plasma process, and then removed from the treatment stations 2 at a discharge section 5. Along the predetermined direction of movement B, an area then remains between the discharge section 5 and the receiving section 4 in which the treatment stations 2 are not loaded. A reference light source 6, explained further below, is arranged there, as shown in Fig. 1.

[0084] Fig. 2 shows a possible embodiment of a treatment station 2 immediately after the container 1 in the form of a PET bottle has been picked up or immediately before it is dispensed. The container 1 is arranged with its opening at the bottom on a lower part 7 of the treatment station 2, from which suitable media for generating a plasma are introduced after a negative pressure has been generated. Before the plasma is generated, a movable upper part 8 of the container treatment station 2 is lowered to form a closed reactor cavity in which a plasma with microwaves is then generated within the container 1. For this purpose, the treatment station 2 has a microwave generator 9, with the microwave energy then being introduced via a coupling channel 10 into the reactor cavity, which is closed after the upper part 8 has been lowered.

[0085] In this context, it should be noted that the illustration in Fig. 2 is only exemplary. In principle, two or four treatment stations 2 can be combined into one module on the support wheel 3.

[0086] Fig. 3 shows a section of the treatment station 2 in the area of ​​the coupling channel 10. Accordingly, an optical waveguide 11 is arranged within the coupling channel 10, with which radiation emitted in the plasma process is received and guided to a schematically shown photodiode 12.

[0087] The transmission of the radiation emitted in the plasma process through the optical waveguide 11 enables the photodiode 12 to be

[0088] Microwave radiation is separated so that spaced from the

[0089] Microwave generator 9 and the coupling channel 10 enable detection and evaluation of the emitted radiation.

[0090] The optical fiber 11 and the photodiode 12 together form an emission detection device, which is connected to an associated evaluation device 13, particularly in the form of a measuring circuit. A separate emission detection device and evaluation device 13 are expediently provided for each treatment station 2, with the evaluation devices 13 of the treatment stations 2 then being jointly connected to a central controller 14.

[0091] With the optical waveguide 11 shown in Fig. 3, the emission detection device is configured for detection along a vertical line of sight. Radiation emitted during the plasma process then travels along the vertical line of sight through a bottom of the respective container 1 to the optical waveguide 11. The aperture of the optical waveguide 11 is also important for detecting the radiation emitted during the plasma process, resulting in a different detection cone depending on the aperture.

[0092] According to the invention, the fixed reference light source 6 is provided which, when the reactor cavity is open, illuminates the passing emission detection devices, ie in particular the optical waveguides 11.

[0093] As shown in Fig. 4, the upwardly radiating reference light source 6 in the form of an LED is located on the movement path of the treatment stations 2 where the plasma is formed in the closed reactor cavity and radiation is emitted accordingly.

[0094] The reference light source 6 formed as an LED or LED arrangement can, for example, emit light in a wavelength range from 600 nm to 1000 nm, in particular 600 nm to 850 nm.

[0095] The reference light source 6 is configured to emit a continuous or substantially continuous luminous flux. The passing emission detection devices are then illuminated as they move along the reference light source 6, thereby determining reference measurement values.

[0096] Within the scope of the invention, it is then provided that individual correction parameters are determined using the reference measurement values ​​for each treatment station 2. It should be noted that all emission detection devices are illuminated equally by the reference light source 6, so that measurement signals of varying strengths for the individual container treatment stations 2 can then be calibrated relative to one another or absolutely.

[0097] In particular, it is possible within the scope of the invention to detect different degrees of aging of the optical emission detection devices of the various container treatment stations 2 and to compensate for this using the correction parameters.

[0098] In order to also be able to determine a change in the aperture of optical waveguides 11, it is preferably provided that the reference light source 6 has a radiation angle that is larger than an aperture of the emission detection device and / or that the reference light source 6 is designed as an extended linear or planar radiation source.

[0099] Fig. 5 shows exemplary measurement curves for reference measured values ​​from successive treatment stations 2 as a function of the rotation angle of the support wheel 3 in a new plasma treatment system. The optical fibers 11, photodiodes 12, and evaluation devices 13 of the various treatment stations 2 initially have largely identical characteristics, so that almost identical measurement curves are determined. However, even in a new system, the determination shown in Fig. 5 makes it possible to determine correction parameters in order to record and compare the radiation emitted in the plasma process with particular precision at the individual treatment stations 2.

[0100] Fig. 6 shows two exemplary measurement curves of differently aged components of two treatment stations 2. In particular, the optical fibers 11 are subject to aging, which can lead to both a reduction in transmissivity and a reduction in aperture.

[0101] Furthermore, the photodiode 12 and the components of the evaluation devices 13, such as electronic components or the like, may also be subject to aging, so that the sensitivity with respect to the detection of radiation emitted in the plasma process may change. This aging can vary considerably for different treatment stations 2.

[0102] The measurement curve shown on the right side of Fig. 6 is similar in height and shape to the originally determined measurement curves shown in Fig. 5. The absolute height of the measurement curve is somewhat lower, which can be attributed, for example, to a certain reduction in the transmissivity of the corresponding optical fiber 11. However, the width and relative shape of the measurement curve are essentially unchanged. From this, it can be concluded that, for example, the aperture of the optical fiber 11 has not changed significantly.

[0103] The measurement curve shown on the left side of Figure 6 not only shows a lower peak value, but also the entire measurement curve is significantly narrower and exhibits a significant deviation in the flank shape. This suggests that light from the reference light source 6 is only being detected at a smaller detection angle, so that, with regard to the previously described design of the optical emission detection device, a reduction in the aperture of the optical waveguide 11 can be concluded.

[0104] Since, according to the invention, the optical detection devices of the various container treatment stations 2 are illuminated equally, individual correction parameters can be determined for the container treatment stations 2 based on the measurement curve shown in Fig. 6, so that, despite the advanced aging, a very accurate relative comparison and, if necessary, also an absolute evaluation of the various container treatment stations 2 with regard to the radiation emitted in the plasma process is possible.

[0105] This allows significantly tighter limits to be set for the measured values ​​expected in the plasma process, which can contribute to a significant improvement in the coating process overall. It is also possible to ensure a correspondingly high level of accuracy despite a certain degree of wear and tear on the components, thus reducing overall maintenance and repair costs despite the improved accuracy.

[0106] In principle, it is also possible to determine and store individual correction parameters for the container treatment stations 2 for different containers 1.

[0107] For example, a reduction in the aperture is more significant for large containers 1, and especially for containers 1 with a large diameter, than for small containers 1 or containers 1 with a small diameter. For a small container 1, for example, it is possible that despite a reduction in the aperture of the optical waveguide 11, a large portion of the radiation emitted in the plasma process is still absorbed. List of reference symbols:

[0108] 1 container

[0109] 2 treatment stations 3 trolleys

[0110] B Direction of movement

[0111] 4 Recording section

[0112] 5 Submission section

[0113] 6 Reference light source 7 Lower part

[0114] 8 Top

[0115] 9 Microwave generator

[0116] 10 coupling channels

[0117] 11 optical fiber 12 photodiode

[0118] 13 Evaluation device

[0119] 14 central control

Claims

Patent claims:

1. Plasma treatment system for containers (1), in particular PET bottles, with a plurality of treatment stations (2) which are attached to a movably drivable support arrangement, wherein the treatment stations (2) each have an optical emission detection device which, with an associated evaluation device (13), is designed to measure radiation emitted in a plasma process, characterized in that a reference light source (6) is provided which is designed to irradiate the optical emission detection devices guided past with the support arrangement.

2. Plasma treatment system according to claim 1, characterized in that the optical emission detection devices each have at least one element selected from the group consisting of optical waveguides (11), optics, and photoelement.

3. Plasma treatment system according to one of the preceding claims, characterized in that the reference light source (6) is an LED or an LED arrangement and preferably emits light in a wavelength range from 600 nm to 1000 nm.

4. Plasma treatment system according to one of the preceding claims, characterized in that the reference light source (6) has a radiation angle which is larger than an aperture of the emission detection device and / or that the reference light source is designed as an extended linear or planar radiation source.

5. Plasma treatment system according to one of the preceding claims, characterized in that the emission detection device is arranged for detection along a vertical line of sight.

6. Plasma treatment system according to one of the preceding claims, characterized in that treatment stations (2) each have a closable reactor cavity for receiving and treating one Container (1), wherein the reference light source (6) is arranged such that it engages in the region of the open reactor cavity in the case of the optical emission detection devices guided past.

7. Plasma treatment system according to one of the preceding claims, characterized in that the evaluation devices (13) are connected to a common central control (14), wherein the central control (14) is designed to determine and store correction parameters assigned to each of the treatment stations (2).

8. Plasma treatment system according to one of the preceding claims, characterized in that 20 to 150, in particular 40 to 120 treatment stations (2) are provided.

9. Plasma treatment system according to one of the preceding claims, characterized in that the support arrangement is designed as a carrier wheel (3).

10. Plasma treatment system according to one of the preceding claims, characterized in that, with respect to a predetermined direction of movement (B) of the support arrangement, the reference light source (6) is arranged behind a delivery section (5) and in front of a receiving section (4) for the containers (1).

11. Method for the plasma treatment of containers (1), in particular with a plasma treatment system according to one of the preceding claims, wherein in a production plant containers (1) are received in movably guided treatment stations (2) and treated with a plasma, in particular coated, and subsequently discharged, wherein the treatment stations (2) have optical emission detection devices with which during light emissions of the plasma occurring during the plasma treatment are recorded and evaluated, wherein the optical emission detection devices are additionally illuminated with at least one reference light source (6) and reference measured values ​​are determined in the process, and wherein individual correction parameters are determined with the reference measured values ​​for the treatment stations (2).

12. The method according to claim 11, wherein the determination of the reference measured values ​​takes place during production operation.

13. The method according to claim 11 or 12, wherein the treatment stations (2) each have a closable reactor cavity, wherein the unloaded treatment stations (2) are guided past the reference light source (6) with an open reactor cavity.

14. Method according to one of claims 11 to 13, wherein for the treatment stations (2) the reference measured values ​​are recorded as a measurement curve, wherein for each of the measurement curves an integral and / or a maximum value and / or a curve width are determined and / or values ​​in a predetermined grid from the measurement curve are used for the evaluation.

15. Method according to one of claims 11 to 14, wherein reference measurement values ​​are determined per second for 4 to 50 treatment stations (2).

16. Method according to one of claims 11 to 15, wherein different correction parameters are determined for containers (1) of different shape and / or size.

17. Method according to one of claims 11 to 16, wherein the at least one reference light source (6) is operated with a constant reference emission.

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