Device and method for checking container-producing moulds for residues

Abstract

The present invention relates to a device for checking a container-producing mould for residues. The device comprises a container-producing mould, for example a blow mould, and an inspection device comprising: a light source designed to emit light towards the container-producing mould; a light detector designed to detect light reflected or scattered by the container-producing mould; and a control unit designed to determine, on the basis of the light detected by the light detector, whether there is a residue on the container-producing mould. The present invention further relates to a method for checking container-producing moulds, for example blow moulds, for residues.

Description

[0001] Device and method for checking molds for producing a container for residues

[0002] The present invention relates to a device for checking molds for producing a container, as well as a method for checking molds for producing a container.

[0003] State of the art

[0004] A variety of manufacturing processes are known for the production of containers, such as beverage bottles. Blow molding is widely used, in which a preform is heated, blown into a suitable mold for shaping, removed from the mold, and finally cooled, resulting in a finished container. Molds are also used in other container manufacturing processes, for example, in the production of pulp containers.

[0005] In the described manufacturing processes, it may happen that residues remain in the mold after the finished container has been removed from the mold, e.g., remnants of the container if it could not be removed cleanly from the mold. However, such residues influence the production of subsequent containers in this mold and can, for example, lead to defects such as deformation, contamination, or leaks. For an efficient and smooth manufacturing process, it is therefore essential that the molds used to produce a container are always free of residues from a previous manufacturing process. This requires an efficient inspection mechanism.

[0006] Task

[0007] Therefore, it is an object of the present invention to provide an apparatus and a method with which a mold for producing a container can be efficiently and reliably inspected for residues. To this end, the invention provides an apparatus according to claim 1 and a method according to claim 9. Further aspects are found in the respective subclaims.

[0008] Solution

[0009] According to the invention, a device for checking a mold for producing a container for residues is provided, which device comprises a mold for producing a container, for example a blow mold, and an inspection device. The inspection device comprises a light source configured to emit light toward the mold for producing a container, a light detector configured to detect light reflected or scattered by the mold for producing a container, and a control unit configured to determine, based on the light detected by the light detector, whether a residue is present on the mold for producing a container.

[0010] In this context, a residue refers to contamination of the mold used to produce a container. This includes, in particular, residues from a previous container manufacturing process, but also includes dust or other contaminants (foreign matter) that would have a detrimental effect on the mold during the production of a container.

[0011] The device and method described herein utilize an optical inspection in which the light from a light source is reflected, scattered, or converted by the mold and detected by a light detector. Based on the light detected by the light detector, the control unit determines whether residues are present on the mold for producing a container. In principle, the optical inspection can be performed with high speed and precision. The detection of artifacts, such as residues in this case, can be detected quickly and with high reliability using appropriate light detectors, such as high-speed cameras. Therefore, the device described solves the initially posed problem of efficiently and reliably checking molds for residues.

[0012] A light source generally refers to a device designed to emit light. This light is radiated / emitted toward the mold used to produce a container. Examples of light sources include LEDs, LED panels, halogen lamps, lasers, or gas discharge lamps. The light source can be designed to emit visible light in a polarized, directed, and / or homogeneous manner.

[0013] A light detector is a device that detects light (in this case, light reflected or scattered by the mold) and generates an electrical signal based on it. This signal is then used by the control unit to determine whether there are residues on the mold. This is explained in more detail below. Examples of light detectors include cameras, photodiodes, or CCD chips.

[0014] A control unit comprises, for example, a computer or a similar device with a storage medium and a processor. The control unit is designed to determine, based on the signal from the light detector, whether there are residues on the mold. Examples of these determinations are given below. The device can be designed to emit UV light, and / or the light detector can be designed to receive light in the visible spectral range and in the infrared. The visible spectral range refers to the range normally visible to humans with a wavelength between 400 nm and 800 nm (visible light). Accordingly, UV light originates from a range with a shorter wavelength than the visible range, in particular between 200 nm and 400 nm. Infrared light refers to the wavelength range above visible light, in particular between 800 nm and 1600 nm.

[0015] It is known that pulp converts incident UV light into visible light. In other words, pulp absorbs UV light and emits visible light. The device is therefore able to exploit and detect this effect. This enables reliable and efficient testing of the mold used to manufacture a container for pulp residues. Recently, pulp has also been shown to offer a way to produce beverage containers from a recyclable and sustainable material.

[0016] A mixture referred to as pulp can consist of water, fibers, and optionally other additives. The fibers can be of natural origin and be biodegradable. The fibers can include lignin, banana leaves, and / or quinine. The fibers can include, for example, cellulose fibers, fibers from conifers, deciduous trees, and / or plane trees, and / or from grasses, reeds, and / or bamboo, or the like. The fibers can include silk threads, spider fibers, algae, natural fibers (such as Danube silphium fibers, hemp, corn, and cotton), banana peels, orange peels, grass, straw, potato starch, or processed cow dung. Cellulose fibers derived from a process through which they were artificially cultivated can also be used. These alternative materials can fully or partially replace the raw material in the event of a shortage of wood as the raw material for a fluid mass containing fibers.The fibers may also comprise fiber mixtures of non-wood materials, such as cotton, hemp, and / or textile fibers.

[0017] The light detector may comprise a camera configured to capture an image of at least a portion of the mold for producing a container. Furthermore, the control unit may be configured to detect, in the image captured by the camera, whether a residue is present in the mold for producing a container.

[0018] The camera can, in particular, be a high-speed camera, allowing a large number of shapes to be viewed within a given time. Capturing an image and examining it with the control unit also offers a versatile way to examine the shapes for residues. This aspect will be discussed in more detail below. The control unit can be configured to detect shadows in the captured image.

[0019] A shadow cast on a mold can indicate that there is a residue in the mold that is blocking the light from the light source, thus creating a shadow on the mold. Such shadows occur primarily across a broad spectral range, including ultraviolet, visible light, and infrared, and can therefore be combined with a variety of light sources. Shadow detection therefore represents a flexible tool for detecting residues in a mold used to manufacture a container.

[0020] In this context, a shadow does not exclusively refer to a darkening effect caused by the residue blocking the light. Rather, the residue can change the brightness distribution in the mold compared to a mold without residue, for example, even leading to a brightening effect. This case, too, is subsumed under the general term "shadow" in this description. A shadow therefore refers to a change in the brightness distribution compared to a mold in which no residue is present.

[0021] An image captured by the camera can be analyzed by comparing it with a template. For this purpose, the control unit, or the control unit's storage medium, has stored reference images. These reference images show, for example, a correct mold without contamination and therefore without the shadows caused by them, so that the mold is completely and evenly illuminated by the light source. The control unit then compares the image captured by the camera with the reference image or a suitable reference image. If, for example, an area is detected in the captured image that is darker than the reference image, the control unit recognizes that this is a shadow. The position of the darkened area can then be derived from the position of the darkened area.

[0022] Alternatively or in addition to illumination using UV light, the mold can be illuminated using homogeneous visible or infrared lighting.

[0023] Another alternative is that the control unit is equipped with an artificial intelligence (Kl) that is trained to recognize shadows in recorded images.

[0024] The light source can be designed to generate an optical pattern, wherein the optical pattern is in particular grid-shaped and / or comprises concentric circles.

[0025] The two types of patterns mentioned allow for the most unambiguous identification of residues in the molds. At the residues, the optical pattern bends / deforms due to the deviating contour of the mold. The bending, which describes a deviation from a regular pattern consisting of a grid or concentric circles, can be evaluated in the image captured by the camera. Deviations from straight lines (in a grid) or (concentric) circles are particularly reliably detectable.

[0026] Furthermore, the control unit can be configured to detect a deviation of the optical pattern from a predefined reference pattern in the captured image. The determination of whether residues are present on the mold for producing a container can be made based on the detected deviation. In other words, the control unit can be configured to determine whether residues are present on the mold for producing a container based on the detected deviation.

[0027] The above statements regarding the comparison with a reference pattern in connection with the detection of a shadow apply analogously to the detection of a deformation of the optical pattern. If the optical pattern represented in the captured image deviates from a reference image taken from a mold without residue, the control device accordingly concludes that a residue is present in the mold.

[0028] Compared to detection based on a shadow, the use of an optical pattern and the detection of a deformation of the optical pattern offers another advantage. A deformation of the optical pattern occurs not only when there is a residue in the mold made of largely or partially opaque material (e.g. pulp), but also when the material has a different refractive index than air. In the case of transparent residues (e.g. from PET), a shadow may be very weak and therefore not detected. A deformation of the optical pattern, however, still occurs and this deviation can therefore be reliably detected. In this respect, the use of an optical pattern in conjunction with the detection of a deviation from a reference image offers a particularly reliable method of detecting residues in the molds.

[0029] The described device may further comprise a cleaning unit or a control of a cleaning device for cleaning the mold for producing a container for which the control unit has determined a residue.

[0030] In conjunction with the other components described (mold and inspection device), an efficient device is provided that reliably detects residues and cleans affected molds. This ensures a smooth production process for the containers. Furthermore, cleaning only those molds in which residues have been detected saves time and resources (e.g., cleaning agents and water) compared to cleaning all molds.

[0031] The inspection device may be stationary and / or the inspection device and the mold for producing a container may be movable relative to each other.

[0032] Machines for manufacturing containers are often so-called rotary machines, where the mold used to produce a container is inspected after the container has been manufactured. Such a machine also comprises a fixed number of molds, which are reused in a cycle for a new container manufacturing process after the container has been manufactured. If the inspection device and the mold are movable relative to one another, a separate inspection device is not required for each mold, so the overall device comprises fewer components. A stationary inspection device, past which the molds move, is advantageous. In this case, the device only requires one inspection device, while it can comprise a large number of molds, which move past the inspection device, particularly in a single-lane transport system.

[0033] The present invention further provides a method for inspecting a mold for producing a container, for example, a blow mold, for residues. The method comprises illuminating at least a portion of a mold for producing a container using a light source, detecting light reflected, converted, or scattered by the mold for producing a container using a light detector, and determining, based on the light detected by the light detector, whether residues are present on the mold for producing a container.

[0034] Just like the device described above, the method solves the aforementioned problem of efficiently and reliably checking molds for residues in container manufacturing. Some of the advantages mentioned below are analogous to those mentioned in connection with the device and will therefore not be explained in more detail here.

[0035] The light source can emit UV light and / or detect light in the visible spectral range. Detection can be achieved, in particular, with the light detector.

[0036] As already mentioned, the emission of UV light with simultaneous detection of visible light enables a reliable and efficient inspection of the container mold for pulp residues, since such a conversion of light takes place in pulp. The method step of determining whether residues are present on the container mold may comprise capturing an image of at least a portion of the container mold with a camera and detecting, in the image captured by the camera, whether a residue is present in the container mold.

[0037] Taking an image and examining it with the control unit also offers a versatile way to examine the molds for residues.

[0038] The residue in the mold for producing a container can be determined based on a shadow detected in the image.

[0039] The detection of a shadow cast therefore represents a flexible tool for detecting residues in a mold used to manufacture a container. As explained previously, the detection of the shadow cast can be carried out by comparing it with a reference image.

[0040] When illuminating at least part of the mold for producing a container, an optical pattern can be emitted in the direction of the mold for producing a container, wherein the detection of the residue in the mold for producing a container in the recorded image comprises the detection of a deviation of the optical pattern from a predetermined reference pattern, wherein the determination of whether there is a residue on the mold for producing a container is carried out based on the detected deviation, and wherein the optical pattern is in particular grid-shaped and / or comprises concentric circles.

[0041] The use of an optical pattern in conjunction with the detection of a deviation from a reference image represents, as already explained in detail, a particularly reliable way of detecting residues in the molds.

[0042] The container may comprise fiber-based material such as pulp. Alternatively, the container may also be made of the fiber-based material.

[0043] The described method can be carried out using the described device. It is therefore understood that features of the device can also be applied to the method in a suitable manner.

[0044] Brief description of the figures Further features and advantages are explained below using the example figures.

[0045] Showing:

[0046] Figure 1 is a schematic side view of an apparatus for checking a mold for producing a container for residues according to a first embodiment;

[0047] Figure 2 is a schematic side view of a device for checking a mold for producing a container for residues according to a second embodiment,

[0048] Figure 3A is a schematic representation of a shadow cast by a residue on the mold, the mold being shown in plan view, and

[0049] Figure 3B is a schematic representation of an optical pattern being deformed by a residue in the mold, the mold being shown in plan view.

[0050] In the following and in the figures, the same reference numerals are used for the same or corresponding elements in the various embodiments, unless otherwise specified.

[0051] Detailed description

[0052] Figure 1 shows a device 1 for inspecting a mold 20 for producing a container for residues according to a first embodiment. This is a schematic side view. The device 1 comprises a mold 20 for producing a container and an inspection device 10, wherein the inspection device 10 comprises a light source 11, a light detector 12, and a control unit 14.

[0053] The mold 20 is used to produce containers, such as beverage bottles made of pulp or plastic (PET or similar), and blow molding is the preferred process. The mold 20 itself is made of metal in particular to withstand the high temperatures of the preforms that are blown into the mold 20 during blow molding. However, other materials for the mold 20 are also conceivable. The mold comprises a base 20a and a side wall 20b and can, for example, be cylindrical.

[0054] The light source 11 is designed to emit light L toward the mold 20 for producing a container and, optionally, to illuminate the mold homogeneously, because fluctuations in brightness could lead to errors in the detection of residues. This can be a directed light source or an omnidirectional light source. In the latter case, suitable apertures and shields should be used to ensure that the light L is emitted toward the mold 20. Suitable light sources include, for example, LED panels with chip-on-board LEDs (achieving high light output in a small area), lasers, incandescent and halogen lamps, etc. Optionally, the mold 20 is completely illuminated by the light source 11, but it may also be sufficient to illuminate only part of the mold 20, for example, the base. The dashed lines schematically represent the beam path of the light L.

[0055] The mold 20 reflects and / or scatters the light from the light source 11. This light is received and detected by the light detector 12. In this embodiment, the light detector 12 is a combination of a camera 12a and a lens 12b, with the lens 12b projecting the light onto the camera 12a (or its corresponding imaging chip). In particular, the camera 12a is a high-speed camera, as this allows the inspection of the mold 20 to be carried out in a particularly short period of time and increases the efficiency of the device 1. In principle, a different type of light detector 12 can also be selected, for example a photodiode, and a lens 12b does not necessarily have to be provided either.

[0056] The light source 11 is arranged laterally next to the light detector 12, more precisely, next to the lens 12b. In particular, the light source 11 surrounds the light detector 12. This results in homogeneous illumination of the mold 20, which is located below the light source 11 and the light detector 12. Furthermore, in this arrangement, no light can enter the light detector 12 directly from the light source 11, but only the light reflected and / or scattered by the mold 20. This results in a stronger contrast in an image captured by the camera because the incidence of background illumination is reduced.

[0057] The light detector 12, such as the camera 12a, generates an electrical signal from the detected light, which is transmitted to the control unit 14. Based on this signal, and thus also on the detected light, the control unit 14 determines whether a residue is present on the mold 20. Specific examples of residue detection are explained below with reference to Figures 3A and 3B.

[0058] The control unit 14 can be a computer or comparable device with a processor and a storage medium. The purpose of these components will be explained below. The inspection device 10 and the mold 20 can be movable relative to one another. In particular, the mold 20 is movable, while the inspection device 10 is stationary. This has the advantage that the device 1 only requires one inspection device 10, past which the mold 20 or the plurality of molds is / are guided. The device 1 can be a rotary machine in which the plurality of molds 20 are guided past the inspection device 10 in a circuit along a transport path. A stationary inspection device 10 with the optical components is also more compact and easier to construct.It is also understood that the device 1 can in principle have more than one inspection device 10, which generates a higher throughput when a large number of shapes are to be examined.

[0059] Overall, the described device 1 achieves an efficient and reliable detection of residues in the mold 20 by optically inspecting the mold 20 for producing a container. This advantage is further clarified by the following explanations.

[0060] A second embodiment of the device 1 for checking a mold 20 for producing a container for residues is shown in Figure 2. Some elements are analogous to the first embodiment, so they will not be explained again here, but only the differences will be highlighted.

[0061] The device 1, in particular the inspection device 10, comprises a pattern projector 16 designed to generate and emit an optical pattern. This optical pattern is, for example, a pattern with regular and / or periodic elements such as a grid or concentric circles. This optical pattern is emitted in the direction of the mold 20. For this purpose, the device 1 further comprises a beam splitter 15 arranged such that the light emitted by the pattern projector 16 is reflected by the beam splitter 15 and redirected in the direction of the mold 20. For this purpose, the beam splitter, which is shown here as part of the lens 12b, is arranged between the mold 20 and the camera 12a. The schematic beam path of the optical pattern is represented by dashed lines.

[0062] The optical pattern, like the light emitted by the light source 11, is reflected and / or scattered by the mold 20 and detected by the camera 12a to generate a corresponding image of the mold 20. The imaging process, the generation of the electrical signal, and the transmission of the electrical signal proceed analogously to the first embodiment. The beam splitter 15, for example, is a 50:50 beam splitter that reflects 50% of the incident light intensity and transmits 50% of the incident light intensity. In principle, other beam splitters can also be used (e.g., 60:40 or 75:25).

[0063] The light source 11 and the pattern projector 16 can be operated independently of each other. For example, it is possible to use only the light from the pattern projector 16 while the light source 11 remains switched off. In an alternative, the light source 11 itself is configured to generate the optical pattern and emit it toward the mold 20. As described with reference to Figure 3B, the use of an optical pattern allows for particularly reliable detection of a residue on the mold.

[0064] With this second embodiment of the device 1, two images can be recorded consecutively. For the first image, the mold 20 is illuminated as homogeneously as possible by the light source 11. This serves to identify residues, obscuring contaminants, and / or holes in the mold 20 by comparison with a suitable reference image (see below). For the second image, the mold 20 is illuminated with the optical pattern. In this way, residues on the mold 20 can also be detected by comparison with a suitable reference image, because the preferably otherwise regular optical pattern is distorted / deformed by the residues. Checking the mold for shadows and for deformation of the optical pattern using the two images together allows for particularly reliable detection of residues on the mold 20.It goes without saying that the two images can also be taken in reverse order.

[0065] The temporal interval between the two images should be as small as possible, for example, less than 100 ps, ​​less than 500 ps, ​​or less than 1000 ps. Typically, the mold 20 is located on a transport device and is transported beneath the inspection device 10. The transport is not stopped for the optical inspection. Therefore, the mold 20 moves slightly between the two images. If the temporal interval is short enough, this spatial offset is also small enough, for example, in the range of less than 1 mm, so that neither the illumination of the mold 20 nor the viewing angle of the camera 12a onto the mold change significantly.

[0066] The following explains by way of example how the control unit 14 can determine whether a residue 21 is located on the mold 20 for producing a container. These examples are not to be understood as limiting, and it is understood that the control unit can also detect a residue 21 on the mold 20 in other ways. Figure 3A shows a mold 20 for producing a container as a schematic top view, so that primarily the bottom 20a can be seen. The mold 20 is homogeneously illuminated by the light source 11. On the bottom of the mold there is a residue 21, which casts a shadow 21a on the bottom 20a of the mold 20. In this example, the brightness of the area in question is reduced compared to surrounding areas.

[0067] The camera 12a captures an image of the mold 20 and transmits the image to the control unit 14. The control unit 14 comprises a storage medium on which reference images are stored, which were recorded for a clean mold without residues. A processor is then configured to compare the image captured by the camera 12a with a matching reference image from the storage medium. As a result of this comparison, the processor receives the information that there is a darkening at the location of the residue, i.e., the associated pixels have a lower brightness. From this, the processor, and thus the control unit 14, concludes that a shadow 21a is present at said location, which is caused by a residue 21 on the mold 20. It should be noted that the shadow 21a does not necessarily lead to a darkening, but generally to a change in the brightness distribution compared to the reference image.

[0068] Classic image analysis algorithms are preferably used for defect evaluation. These algorithms first center at least one ROI (region of interest) on the image section to be evaluated using position detection. Subsequently, whether the mold is contaminated or not is determined using light / dark jump detection, edge filtering, and error pixel detection, among other methods.

[0069] Alternatively, image analysis can be performed using artificial intelligence. The machine learning model for contamination identification is preferably based on an (artificial) neural network.

[0070] In this way, the described device 1 can efficiently and reliably / precisely determine, using optical means, whether a residue is present in a mold under examination. If a comparison of the captured image with the reference image reveals no difference, the control unit 14 concludes that there is no residue on the mold 20.

[0071] Figure 3B shows a mold 20 for producing a container as a schematic top view, so that primarily the base 20a is visible. An optical pattern in the form of a grid is shown on the mold 20. A grid comprises a plurality of lines running parallel and perpendicular to one another. If a clean mold 20 without residues is illuminated with the optical pattern, this regular grid will also be visible on the mold 20, here on its base 20a. In this example, there is now a residue 21 in the form of a raised area on the base 20a of the mold 20. The residue can, for example, be part of a previously produced container that was not cleanly removed from the mold. This residue 21 then causes the optical pattern at the location of the residue to be deformed accordingly and is no longer a regular grid.

[0072] The camera 12a captures an image of the mold 20 with the optical pattern and transmits the image to the control unit 14. As previously described, the control unit 14 compares the captured image with a reference image from the storage medium and, from this comparison, detects a deviation 21b between the optical pattern in the captured image and the optical pattern in the reference image. From this, the control unit 14 determines that a residue 21 is present in the mold and, in principle, can also determine its position.

[0073] Compared to homogeneous illumination with light, the use of an optical pattern has the advantage that the residue can be detected better or more reliably. Reflection of light in the mold 20 may reduce the brightness contrast of the shadow, making it impossible to reliably detect the shadow in the captured image. An optical pattern, on the other hand, is less susceptible to the effects of reflections and loss of contrast and thus represents an even more reliable method for checking a mold 20 used in container production for residues.

Claims

Claims 1. Device (1) for checking a mold for producing a container for residues, comprising: a mold (20) for producing a container, for example a blow mold, and an inspection device (10) comprising a light source (11) which is designed to emit light in the direction of the mold (20) for producing a container, a light detector (12) which is designed to detect light reflected or scattered by the mold (20) for producing a container, and a control unit (14) which is designed to determine, on the basis of the light detected by the light detector (12), whether a residue (21) is located on the mold (20) for producing a container.

2. Device (1) according to claim 1, wherein the light source (11) is designed to emit UV light, and / or wherein the light detector (12) is designed to detect light in the visible spectral range.

3. Device (1) according to one of the preceding claims, wherein the light detector (12) comprises a camera (12a) which is designed to record an image of at least a part of the mold (20) for producing a container, and wherein the control unit (14) is designed to recognize in the image recorded by the camera (12a) whether there is a residue (21) in the mold (20) for producing a container.

4. Device (1) according to claim 3, wherein the control unit (14) is designed to detect a shadow (21a) in the recorded image.

5. Device (1) according to one of claims 3 or 4, wherein the light source (11) is designed to generate an optical pattern, and wherein the optical pattern is in particular grid-shaped and / or comprises concentric circles.

6. Device (1) according to claim 5, wherein the control unit (14) is designed to detect a deviation (21b) of the optical pattern from a predetermined reference pattern in the recorded image, and wherein the determination of whether a residue (21) is present on the mold (20) for producing a container is carried out based on the detected deviation.

7. Device (1) according to one of the preceding claims, further comprising a cleaning unit for cleaning the mold (20) for producing a container for which the control unit (14) has determined a residue (21).

8. Device (1) according to one of the preceding claims, wherein the inspection device (10) is stationary, and / or wherein the inspection device (10) and the mold (20) for producing a container are movable relative to one another.

9. A method for checking a mold (20) for producing a container, for example a blow mold, for residues, comprising: Illuminating at least part of a mold (20) for producing a container by means of a light source (11), Detecting light reflected or scattered by the mold (20) for producing a container by means of a light detector (12), and Determining, based on the light detected by the light detector (12), whether a residue (21) is present on the mold (20) for producing a container.

10. The method according to claim 9, wherein the light source (11) emits UV light, and / or wherein light in the visible spectral range is detected by the light detector (12).

11. The method according to claim 9 or 10, wherein the step of determining comprises: taking an image of at least a part of the mold (20) for producing a container with a camera (12a), and Detecting, in the image taken by the camera (12a), whether there is a residue (21) in the mold (20) for producing a container.

12. The method according to claim 11, wherein the residue (21) in the mold (20) for producing a container is determined based on a shadow (21a) detected in the image.

13. The method according to claim 11 or 12, wherein an optical pattern is emitted in the direction of the mold (20) for producing a container, wherein the detection of the residue (21) in the mold (20) for producing a container in the recorded image comprises the detection of a deviation (21b) of the optical pattern from a predetermined reference pattern, wherein the determination of whether a residue (21) is located on the mold (20) for producing a container is carried out based on the detected deviation, and wherein the optical pattern is in particular grid-shaped and / or comprises concentric circles.

14. Method according to one of claims 9 to 13, wherein the method is carried out with the device (1) according to one of claims 1 to 8.

15. The method according to any one of claims 9 to 14, wherein the container comprises fiber-based material or consists of fiber-based material.

Images