Device for cleaning at least one conveyor belt with an electromagnetic radiation source

Abstract

Device for cleaning at least one conveyor belt (1) and / or workpieces (4) transported by means of the conveyor belt (1), wherein the conveyor belt (1) is driven around a holding device (2), wherein at least one vacuum device (7) is provided for generating a cleaning air flow in a cleaning chamber (8), and wherein the conveyor belt (1) optionally passes through the cleaning chamber (8) with the workpieces (4) located on or attached to it, characterized in that an electromagnetic radiation source (9, 10, 11, 12) is additionally provided which acts on the conveyor belt (1) and / or the workpiece (4) and which dissolves impurities which are in turn carried away by the cleaning air flow.

Description

[0001] The invention relates to a device for cleaning at least one conveyor belt and / or workpieces transported by means of the conveyor belt, wherein the conveyor belt is driven around a holding device, wherein at least one vacuum device is provided for generating a cleaning air flow in a cleaning chamber, and wherein the conveyor belt optionally passes through the cleaning chamber with the workpieces located on or attached to it.

[0002] Contamination often occurs when workpieces are conveyed along a holding device using conveyor belts. This applies both when the workpieces are magnetically fixed using magnetic holding elements arranged longitudinally along the holding device and when the fixing is achieved using vacuum units. The workpieces are transported either lying on the conveyor belt or suspended from it in the longitudinal direction of the holding device.

[0003] Typically, workpieces are contaminated with chips, dust, and drilling fluids or cleaning agents due to previous processing steps such as chip removal or drilling. These contaminants often adhere not only to the workpieces but can also contaminate the conveyor belt itself. Such contamination poses a long-term problem because it makes re-fixing and transporting further workpieces more difficult. This can be particularly problematic during suspended transport, as it reduces the adhesion of the workpieces to the conveyor belt, potentially leading to unintentional falls. Therefore, conveyor belts, in particular, must be cleaned regularly. This takes place in the cleaning chamber through which the conveyor belt passes, either with or without workpieces on the belt.

[0004] This is especially true when different workpieces are to be transported on the same conveyor belt. For example, aluminum plates require different corrosion protection compared to steel plates, meaning that different deposits will be present on the conveyor belt and must be removed before the workpieces being transported are changed.

[0005] Currently, mechanical cleaning methods are predominantly used in practice to clean both workpieces and conveyor belts. However, it has become apparent that the brushes most commonly used are increasingly unsuitable for this purpose, as the workpieces transported on the conveyor belt often have a rough, uneven surface. Furthermore, brushes are often unable to reliably remove stubborn residues such as baked-on deposits or oil films from the conveyor belt.

[0006] For this reason, the prior art attributed to the applicant according to DE 295 07 865 U1 works in such a way that a scraper that can be pressed against the wall surface to be cleaned is provided. This scraper has a pivotally mounted scraper arm with a scraper blade. In addition, the scraper can be pressed against the conveyor belt by means of an adjusting device.

[0007] Such mechanical cleaning methods, whether using brushes or the described scraper, reach their limits when, for example, delicate plates with a defined surface structure and low material thickness are to be transported using such conveyor devices. Bipolar plates, used in the production of fuel cells, are an example of such plates. The same applies to films transported in an alternative manner for the production of accumulators. While approaches to gentle cleaning methods already exist in the prior art, specifically EP 4 335 560 A1, which is attributed to the applicant, the described measures are only partially suitable for cleaning the conveyor belt alone. The invention aims to remedy this situation.

[0008] The invention is based on the technical problem of further developing such a device for cleaning at least one conveyor belt and / or workpieces transported by means of the conveyor belt in such a way that a particularly gentle cleaning effect is observed.

[0009] To solve this technical problem, the invention proposes, starting from a generic device, that an additional electromagnetic radiation source be provided which acts on the conveyor belt and / or the respective workpiece, dissolving impurities which in turn are carried away with the cleaning air stream.

[0010] The invention is based on the premise that the electromagnetic radiation source is selected to dissolve contaminants present on the conveyor belt and / or the workpiece, and is particularly suitable for industrial cleaning purposes, specifically for cleaning both the conveyor belt and the transported workpieces. This is because contaminants observed in this context, such as grease, release agents, coatings, oils, etc., are dissolved, become brittle, or evaporate upon exposure to the electromagnetic radiation. The resulting debris, thus removed from the conveyor belt and / or the workpiece transported on it, can then be carried away by the cleaning airflow.

[0011] This prevents the dissolved contaminants from being released uncontrollably into the environment. Rather, the design within the scope of the invention is such that the cleaning airflow inside the cleaning chamber is such that the detached contaminants practically do not leave the cleaning chamber and are not carried away, but rather can be separated and collected, for example.

[0012] In this way, the relevant contaminants are collected in a targeted manner and can subsequently be further processed, for example, as hazardous waste or incinerated. Furthermore, it is possible for any additional exhaust gases generated during this process to be transported away along with the cleaning air stream and, for example, recirculated – just like the cleaning air stream itself. This allows the device according to the invention to be used even in environments that are particularly sensitive with regard to potential contamination, such as inside cleanrooms. This is further enhanced by the fact that the cleaning chamber can preferably be sealed against the conveyor belt to be cleaned and / or the workpieces transported on it, as will be described in more detail below.

[0013] To realize and implement the cleaning process according to the invention, the electromagnetic radiation source is preferably designed as a laser, in particular an infrared laser, or includes one. Generally, other radiation sources such as fiber or Nd:YAG lasers or excimer lasers are also conceivable. The radiation source can, for example, be designed as a radiation source integrated into the cleaning device. Alternatively, it is also conceivable that the radiation source itself is connected to the cleaning device as an external element, so that, for example, maintenance work can be carried out easily and independently of the rest of the cleaning device.

[0014] It is particularly preferred that the infrared laser has a wavelength of 10,064 nm. This wavelength is particularly common at the output of a CO2 laser, making a CO2 laser configuration the preferred radiation source. Such a CO2 laser typically uses a gas mixture of carbon dioxide (CO2), nitrogen (N2), and helium (He) as the active medium. The gas is excited by an electrical discharge, with the nitrogen storing energy and transferring it to the CO2. The infrared light emitted in this way, in the wavelength range of 10.6 µm, is particularly suitable for industrial applications, as CO2 lasers are generally known for their high efficiency and performance combined with precise radiation, making them especially suitable for processing materials such as metals and plastics.

[0015] In a preferred embodiment, the laser or infrared laser is operated in pulsed mode, preferably with a pulse frequency of 1 kHz to 100 kHz, particularly 10 kHz to 50 kHz. The pulse frequency, among other parameters, is responsible for controlling the thermal load acting on the conveyor belt and / or workpiece to be cleaned, ensuring that no long-term damage to the conveyor belt occurs due to the laser exposure. Continuous operation is also conceivable, but pulsed laser operation is preferred. The pulse frequencies are also generally related to the cleaning intensity of the laser, with higher frequencies typically resulting in faster cleaning, while lower frequencies generally provide a more uniform energy input and thus a lower thermal load.

[0016] For this purpose, a laser pulse duration of between 1 ps and 100 ns, preferably 10 ps and 10 ns, is preferably selected. In general, the invention preferably operates with comparatively short pulse durations, as this is particularly suitable for sensitive surfaces such as thermoplastic materials. The short pulse duration ensures that the energy absorbed by the conveyor belt is kept low and that the absorbed energy can be dissipated quickly enough by the surroundings, thus minimizing the risk of the conveyor belt melting. Overall, the pulse duration should be selected to minimize thermal damage to the conveyor belt.

[0017] For this reason, the infrared laser according to the invention preferably has a power output of 10 W to 500 W, preferably 10 W to 200 W. The output power of the infrared laser also determines at least partially the energy absorbed by the conveyor belt and consequently the heat generated in the conveyor belt during the cleaning process. Low-power lasers are particularly preferred so that cleaning can be carried out gently and with at least the majority of the prevention of any thermal damage.

[0018] For this purpose, the beam power of the laser or infrared laser is preferably between 0.1 J and 5 J per pulse, in particular between 0.5 J and 1.5 J. The thermal load on the conveyor belt, which results essentially from the pulse duration and power of the laser, is generally selected such that the thermal load on the conveyor belt is kept as low as possible and that no permanent thermal damage to the conveyor belt is observed, while at the same time ensuring sufficient cleaning performance of the laser.

[0019] For this purpose, the power density of the laser is preferably 10 MW / cm². 2 up to 100 MW / cm² 2 , preferably 10 MW / cm² 2 up to 50 MW / cm² 2The area illuminated by the laser is particularly important in this context for determining the achieved power density. In addition to the illuminated area, the conveyor belt speed is also a crucial factor when it comes to estimating the thermal effects on the conveyor belt as a function of the power density and adjusting it for gentle cleaning. The cleaning area irradiated by the laser can preferably be designed as a rectangle completely illuminating the conveyor belt in the transverse direction.

[0020] For this purpose, the infrared laser may preferably include an optical element, in particular a beam expander. The beam expander is generally located downstream of the laser, so that it essentially determines the radiation area. The beam expander can, for example, be a lens, in particular a cylindrical lens. The lens can, for example, be concave. Preferably, the beam expander is selected such that the resulting irradiation area projects a shape that is at least roughly rectangular onto the surface to be cleaned. A two-dimensional shape for the laser projection area, such as a line running perpendicular to the conveying direction, is also conceivable.

[0021] Preferably, light is coupled into the cleaning chamber via an optical fiber. The optical fiber can be, for example, a glass fiber or a plastic fiber, in particular a POF (polymer optical fiber). The optical fiber is preferably selected such that infrared light, in particular, is guided into the cleaning chamber with minimal loss. For this purpose, the optical fiber can be, for example, a quartz glass fiber (silica fiber), a fluoride glass fiber, or a plastic infrared fiber.

[0022] The light coupling into the cleaning chamber is typically located centrally inside the chamber and directed towards the conveyor belt or the workpieces being transported by the conveyor belt. This allows for the possibility of implementing a suction channel on at least one side of the optical fiber, which communicates with the vacuum system for generating the cleaning airflow. Usually, a suction channel is provided on both sides of the optical fiber, each of which can be equipped with its own vacuum system. Furthermore, it has proven advantageous for the cleaning airflow and any additional carrier gas used, or a carrier gas airflow generated by it, to coincide. Nitrogen under positive pressure, for example, can be used as the carrier gas.

[0023] Preferably, the device includes at least one gas source for flooding the cleaning chamber with gas. The gas source can be either an integrated unit within the device or an external gas unit connected to the cleaning device, for example, via a gas line. In particular, a gas line is provided from the gas source to the cleaning chamber. It is conceivable, for example, that the gas or carrier gas introduced under pressure has a temperature different from, and especially lower than, the ambient temperature, in order to achieve a cooling effect in addition to the cleaning effect. This would allow, for example, the cooling of the conveyor belt heated by the laser, thus minimizing or preventing any thermal damage.

[0024] In this context, it has proven particularly advantageous to install a filter upstream of the vacuum system to separate the contaminants. To facilitate cleaning, the filter is generally replaceable. Furthermore, the design is usually such that the cleaning chamber extends across the conveyor belt in a transverse direction. In addition, the cleaning chamber can be mounted to float relative to the conveyor belt to ensure the most effective possible seal between the cleaning chamber and the conveyor belt, as well as against the workpieces being transported on the conveyor belt.

[0025] For this purpose, the floating bearing features, for example, guide pins oriented transversely to the longitudinal direction of the conveyor belt, as will be explained in more detail below with reference to the figure description. Each guide pin can have a cup bearing in the cleaning chamber at its corresponding end. Furthermore, it has proven advantageous in this context if the respective guide pin is made of plastic.

[0026] The conveyor belt to be cleaned at this point within the scope of the invention is usually a toothed belt or toothed belt conveyor. This is typically made of plastic, and in particular thermoplastic plastic, preferably polyurethane. In this context, at least one surface coating is also conceivable, which, for example, repels contaminants and foreign bodies. An additional layer, preferably made of a temperature-stable plastic, is also possible, so that any damage to the conveyor belt caused by laser irradiation is prevented.

[0027] According to the invention, the conveyor belt preferably incorporates color pigments, preferably dark color pigments. These color pigments can be, for example, carbon particles or similar pigments incorporated into the conveyor belt. The color pigments are particularly preferably incorporated into the conveyor belt material during the (extrusion) manufacturing process. This dark coloration of the conveyor belt enables the laser irradiation to be absorbed particularly efficiently by the conveyor belt and, in particular, by the contaminants located on the conveyor belt.

[0028] In principle, the conveyor belt can be made entirely or partially of metal. Hybrid forms combining plastic and metal are also conceivable. Other materials can also be used, such as minerals as additives, natural fibers like hemp or rayon, etc. That is to say, the term "conveyor belt" is to be interpreted broadly according to the invention and ultimately refers to any elongated belt, which is usually guided over rollers at its ends and is suitable for transporting objects.

[0029] The invention provides a device for cleaning at least one conveyor belt and / or workpieces transported by the conveyor belt, enabling particularly effective cleaning of the conveyor belt and / or the workpieces transported by it. To achieve this, the invention utilizes an electromagnetic radiation source that acts upon the surface of the conveyor belt and / or the workpieces transported by it. This allows any contaminants or adhering substances to be, for example, burned off or removed from the surface by the directed beam.

[0030] All of this takes place inside the cleaning chamber, which is positioned next to the conveyor belt or the workpieces being transported. This prevents the loosened contaminants from being released into the environment. Instead, the contaminants are carried away by the cleaning airflow passing through the chamber and can be removed by the filter upstream of the vacuum system. This is where the key advantages lie.

[0031] The invention will now be explained in more detail with reference to a drawing that illustrates only one embodiment; the drawing shows: Fig. 1 the device according to the invention in a basic overview and Fig. 2. The electromagnetic radiation source in detail.

[0032] In the Fig. Figure 1 shows a device for cleaning at least one conveyor belt 1. The conveyor belt 1 is made of plastic, in particular polyurethane according to the exemplary embodiment. Furthermore, the conveyor belt 1 is designed as a toothed belt conveyor belt and can be manufactured, for example, by extrusion. The conveyor belt 1 is guided around a holding device 2 by a drive mechanism. Drive wheels 3, arranged at each end of the holding device 2, provide the drive for the conveyor belt 1.

[0033] With the help of conveyor belt 1, in a space located in the Fig. 1. Workpieces 4 are transported in the longitudinally oriented conveying direction F. The workpieces 4 may be plate-shaped objects that are magnetizable and are therefore held in contact with the conveyor belt 1 by means of magnetic units located inside the holding device 2 (not shown). Alternatively or additionally, a vacuum is generated inside the holding device 2, which, according to the exemplary embodiment, is provided by means of a vacuum device 5.

[0034] The vacuum device 5 can be a suction blower, which generates the desired vacuum inside the holding device 2. The vacuum inside the holding device 2 communicates with the conveyor belt 1 or suction openings 6 in the conveyor belt 1, which are shown in the enlarged illustration, via vacuum channels. The workpiece 4 can be held in contact with the conveyor belt 1 via these suction openings 6 and transported together with the conveyor belt 1.

[0035] According to the exemplary embodiment, in addition to the vacuum device 5 or the suction blower, a further vacuum device 7 is implemented, with the aid of which a vacuum device located in the Fig. 1. The cleaning airflow, indicated by arrows, is generated in and through a cleaning chamber 8. It is also possible to combine the respective vacuum devices 7 and the vacuum device 5 provided at this point. In any case, the design is such that the cleaning chamber 8 is arranged above the conveyor belt 1 and the conveyor belt 1 passes through the cleaning chamber 8 at its lower edge. This can also apply to the workpieces 4 located on the conveyor belt 1 in the exemplary embodiment and in the surface transport shown here.

[0036] As a rule, the cleaning chamber 8 is located in the upper run of the conveyor belt 1. In contrast, the workpieces 4 are guided in the conveying direction F on the lower run of the conveyor belt 1 and transported suspended from it. They can be picked up at one point and placed down at a distance from it. This allows the upper run of the conveyor belt 1 to be cleaned of any contaminants, for example, on its surface during the transport of the workpieces 4, using the cleaning airflow. In principle, the workpieces 4 can also be cleaned on their respective surfaces using the method described below, although this is not shown.

[0037] For cleaning the conveyor belt 1, the invention utilizes a radiation source 9, 10, 11, 12, which acts on the conveyor belt 1 and / or the respective workpiece 4 and loosens contaminants from its surface, which are then carried away by means of the cleaning airflow. For this purpose, the radiation source 9, 10, 11, 12 is described in detail and as shown in the illustration. Fig. 1 is equipped with a beam device 9, 10. The beam device 9, 10 has a laser beam 9 at its output, which extends inside the cleaning chamber 8, approximately in the center. It can also be seen that the laser beam 9 is directed approximately perpendicularly to the conveyor belt 1 or its surface. This allows the laser beam 9 to clean the surface of the conveyor belt 1 particularly effectively of contaminants.

[0038] Based on the Fig. Figure 2 shows that the radiation source 9, 10, 11, 12 is initially equipped with a laser 11. In this example, and quite schematically, the electromagnetic radiation source, or laser 11, is an infrared laser, specifically a CO2 laser. The generated laser beam 9 is directed from the laser 11, or CO2 laser, to an optical fiber 10 via a beamline 12 connected to the CO2 laser. The end of the optical fiber 10 is immersed in, or sealed to, the cleaning chamber 8 mentioned earlier. The beamline 12 can preferably be identical in construction to the optical fiber 10, so that the laser beam is deflected from the laser 11, or CO2 laser, to the cleaning chamber 8 with minimal loss.

[0039] Furthermore, an external gas supply 13, 14 is connected to the cleaning chamber 8. Based on the Fig. Figure 2 shows that the gas supply 13, 14 is initially equipped with a source 13 for a carrier gas. In this example, and quite schematically, the source 13 is a pressurized gas cylinder or a pressure compressor, which supplies atmospheric air (or nitrogen) under overpressure to a gas line 14. This gas line is immersed at its end in the previously mentioned cleaning chamber or is sealed to it. The gas source 12 can also be a replaceable gas cylinder, for example, filled with nitrogen. Depending on the technical equipment at the installation site, the pressure compressor or source 13 here represents and exemplifies the simple connection of compressed air available at the installation site to the gas line 14.

[0040] If we now return to the Fig. Looking back at Figure 1, it can be seen that suction channels 15 are provided on at least one side next to the laser beam 9, which is located centrally inside the cleaning chamber 8. In fact, according to the exemplary embodiment, there are two suction channels 15 on both sides of the laser beam 9, by means of which the contaminants detached from the surface of the conveyor belt 1 by the laser beam 9 are transported out of the cleaning chamber 8. For this purpose, a filter 16, which is designed to be replaceable for cleaning purposes, is connected upstream of each of the previously mentioned vacuum devices 7. The filter 16 is located outside the cleaning chamber 8. The respective suction channel 15 is not usually formed by any guide, but mostly purely virtually by the flow conditions inside the cleaning chamber 8.

[0041] The exemplary embodiment shows that two vacuum devices 7, each with an upstream filter 16, are provided at this point to collect and separate the deposits detached from the surface of the conveyor belt 1 on both sides of the laser beam 9 and extracted by means of the suction channels 15. The suction channels 15 communicate with the respective vacuum device 7, thereby generating the previously described cleaning airflow through the cleaning chamber 8. This cleaning airflow utilizes the carrier gas, or in this example, the pressurized atmospheric air, which is fed from the source 13 via the gas line 14 into the cleaning chamber 8 and then through the suction channels 15 and the respective filters 16 to the vacuum device 7.It is understood that the cleaning airflow in question, generated in this way, can be designed to be recirculated and, if necessary, closed, thus preventing any contaminants released in cleaning chamber 8 from being observed outside of it. As a consequence, the carrier gas, or, according to the exemplary embodiment, the pressurized atmospheric air, can also be circulated. This also applies to any combustion gases produced during this process, which are likewise circulated and thus contained within the chamber. Fig. 1 The device shown in its entirety is ideally suited for installation in cleanrooms because contamination is not a concern.

[0042] It can be seen that the cleaning chamber 8 completely overlaps the conveyor belt 1, taking into account a certain length in the longitudinal direction (or conveying direction F) and perpendicular to it, that is, transversely to the longitudinal extent of the associated conveyor belt 1. Furthermore, according to the embodiment, the cleaning chamber 8 is floating relative to the conveyor belt 1. For this purpose, guide pins 17 oriented transversely to the longitudinal direction of the conveyor belt 1 and thus to the conveying direction F can be provided. It can be seen that, according to the embodiment, guide pins 17 are provided on the front and rear sides of the cleaning chamber 8 and are mounted on or in the cleaning chamber 8. For this purpose, each of the two guide pins 17 has a cup bearing at its end in the cleaning chamber 8. According to the embodiment, and without limitation, the guide pins 17 are made of plastic.

[0043] In this way, the cleaning chamber 8 can be positioned against the conveyor belt 1 using the guide pins 17, thereby sealing the cleaning chamber 8 against the conveyor belt 1. Of course, other sealing methods are also possible at this point. The guide pins 17 are each equipped with springs (not explicitly shown). The surface of the conveyor belt 1 is thus exposed to the laser beam 9, which loosens the contaminants. The contaminants loosened in this way are carried away by the cleaning airflow and separated by the replaceable filter 16 outside the cleaning chamber 8.

[0044] The shape of the laser beam 9 emerging from the optical fiber is expanded by a widening optic 18, in particular a cylindrical lens 18. The cylindrical lens 18 is shown in the enlarged view of the Fig.In the embodiment shown in Figure 1, a rectangular radiation area 19 is projected onto the conveyor belt 1 within the cleaning chamber 8. In this way, the surface thermal load on the conveyor belt 1 is adjusted so that no thermal damage is observed, while simultaneously ensuring successful cleaning of the conveyor belt 1. Reference symbol list 1 conveyor belt 2 Holding device 3 drive wheel 4 Workpiece 5 Vacuum device 6 Suction opening 7 Vacuum device 8 Cleaning chamber 9 Laser beam 10 optical fibers 11 electromagnetic radiation source 12 Beam line 13 Source 14 Gas pipeline 15 Suction channel 16 filters 17 guide pins 18 cylindrical lens 19 radiation area QUOTES CONTAINED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 295 07 865 U1

[0006] EP 4 335 560 A1

[0007]

Claims

[1] Device for cleaning at least one conveyor belt (1) and / or workpieces (4) transported by means of the conveyor belt (1), wherein the conveyor belt (1) is driven in a rotating manner around a holding device (2), wherein at least one vacuum device (7) is further provided for generating a cleaning air flow in a cleaning chamber (8), and wherein the conveyor belt (1) optionally runs through the cleaning chamber (8) with the workpieces (4) located thereon or thereat, characterized by that an electromagnetic radiation source (9, 10, 11, 12) is additionally provided which acts on the conveyor belt (1) and / or the workpiece (4), which releases contaminants which in turn are transported away with the cleaning air flow. [2] Device according to claim 1, characterized by that the electromagnetic radiation source (9, 10, 11, 12) is designed as a laser (11), preferably an infrared laser (11), or contains such a laser. [3] Device according to claim 2, characterized by that the infrared laser (11) has a wavelength of 10 064 nm. [4] Device according to one of claims 1 to 3, characterized by that the laser (11) is pulsed, preferably with a pulse frequency of 1 kHz to 100 kHz, in particular 10 kHz to 50 kHz. [5] Device according to one of claims 1 to 4, characterized by that the pulse duration of the laser (11) is 1 ps-100 ns, preferably 10 ps-10 ns. [6] Device according to one of claims 1 to 5, characterized by that the laser (11) has a power of 10 W to 500 W, preferably 10 W to 200 W. [7] Device according to one of claims 1 to 6, characterized by that the beam power of the laser (11) per pulse is 0.1 J to 5 J, in particular 0.5 J to 1.5 J. [8] Device according to one of claims 1 to 7, characterized by that the power density of the laser (11) is 10 MW / cm 2 up to 100 MW / cm2 , preferably 10 MW / cm 2 up to 50 MW / cm 2 , amounts. [9] Device according to one of claims 1 to 8, characterized by that the laser (11) has an optical element (18), in particular an expansion optic (18). [10] Device according to one of claims 1 to 9, characterized by that the light coupling of the laser (11) into the cleaning chamber (8) takes place via an optical fiber (10). [11] Device according to claim 10, characterized by that a suction channel (15) is provided at least on one side, preferably on both sides, of the optical fiber (10), which communicates with the vacuum device (7) for generating the cleaning air flow. [12] Device according to one of claims 1 to 11, characterized by that the cleaning chamber (8) overlaps the conveyor belt (1) in the transverse direction. [13] Device according to one of claims 1 to 12, characterized bythat the cleaning chamber (8) is flooded with at least one gas, in particular nitrogen. [14] Device according to one of claims 1 to 13, characterized by that the conveyor belt (1) is made of thermoplastic material, preferably polyurethane. [15] Device according to one of claims 1 to 14, characterized by that the conveyor belt (1) has color pigments, preferably dark color pigments.

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