DEVICE AND METHOD FOR COATING A WORKPIECE

Description

Technical field

[0001] The invention relates to a device for coating a workpiece, which preferably consists at least partially of wood, wood-based material, plastic or the like, according to the preamble of claim 1, and to a method for coating a workpiece. State of the art

[0002] In the furniture and building component industries, workpieces made of materials such as wood, wood-based materials, or plastics are frequently coated, particularly on their narrow surfaces. In addition to other joining techniques, an adhesive is often used, applied, for example, with a glue roller to the surface of the workpiece to be coated or to a joint surface of the coating material. A typical adhesive is hot melt, which is melted and then applied.

[0003] This joining technology has proven itself for decades. However, the demands placed on the joint have steadily increased in recent years. The quality of the joint is determined, among other things, by its strength (e.g., peel resistance), durability, and tightness (e.g., against moisture), as well as its appearance. There is still potential for improvement in these areas.

[0004] Furthermore, it has been shown that the joining process is also influenced by diverse environmental conditions, which reduces the reproducibility of the coating process and increases the need for user intervention.

[0005] Furthermore, EP 4 124 431 A1 discloses a coating device and a method for operating a coating device. The coating device comprises a first energy supply section and a second energy supply section, which are arranged such that the first energy supply section and the second energy supply section can act on a coating material. The coating device also comprises a shielding device that is movable into a first position in which the shielding device at least partially shields the second energy supply section. Description of the invention

[0006] The invention is based on the objective of providing a device for coating a workpiece of the type mentioned above, which enables a high quality of the joining connection with high reproducibility.

[0007] This problem is solved by a device for coating a workpiece according to claim 1 and a method for coating a workpiece according to claim 11. Particularly preferred embodiments of the invention are specified in the dependent claims.

[0008] The invention is based on the understanding that the quality and reproducibility of the bond are significantly influenced by a precise adjustment of the properties of the adhesive, such as temperature, pressure, layer thickness, and surface area. Against this background, the invention provides that a coating device of the type mentioned above includes a detection unit for detecting at least one property of the applied adhesive and a reactivation unit for at least partially reactivating the applied adhesive. The detection unit is configured to detect at least one property of the applied adhesive in an area between the adhesive application unit and the reactivation unit.

[0009] In this way, both the quality of the bond and the reproducibility of the joining process can be significantly improved. In particular, one or more properties of the adhesive, which are crucial in this respect, can be precisely detected by the first detection unit. Based on this, the joining process can be controlled more precisely than before. The reactivation unit enables a particularly precise adjustment of the adhesive's activation level, which on the one hand leads to a particularly high-quality bond, and on the other hand also increases reproducibility. To achieve this, the reactivation unit is positioned downstream of the first detection unit and can thus react immediately to any fluctuations in one or more properties of the adhesive.

[0010] Last but not least, the design according to the invention also reduces the demands placed on the operator, and the coating process proves to be stable and reproducible even under changing environmental conditions. Finally, the invention also contributes to reducing workpiece rejects.

[0011] According to a further development of the invention, the first detection unit is configured to detect the temperature and / or layer thickness of the applied adhesive. These parameters have proven to be particularly crucial for the quality and reproducibility of the bond.

[0012] Furthermore, according to a further development of the invention, the detection unit is configured to detect at least one property of the applied adhesive over a wide area, in particular across the entire surface. This ensures that the adhesive is actually present at all, or at all desired, locations on the surface to be coated and / or the coating material to be joined, which is also crucial for the quality and reproducibility of the bond. The use of a camera has proven particularly effective for this purpose.

[0013] Furthermore, according to a further development of the invention, the device includes a second sensing unit for detecting at least one property, in particular the temperature, of the applied adhesive. The use of a second sensing unit initially enables even greater precision in achieving the desired properties of the adhesive. Moreover, different sensing units can be combined in this way, which can be tailored to the respective application. For example, the second sensing unit can primarily serve to provide final verification of the coating process, which has already been optimized by the first sensing unit. This allows the second sensing unit to be designed to be significantly more compact than the first.This, in turn, opens up the possibility of positioning the second detection unit virtually anywhere, in particular in such a way that at least one property of the applied adhesive can be determined immediately before the coating material is pressed onto the workpiece. This is precisely the point and time at which one or more of the desired properties of the applied adhesive should be present to achieve an optimal coating result. The use of a second detection unit makes a significant contribution to this.

[0014] The aforementioned effects of the second detection unit can be achieved particularly effectively if, according to a further development of the invention, the second detection unit detects at least one property of the applied adhesive in an area between the reactivation unit and the pressure unit. This allows not only the effect of the reactivation unit to be checked and, if necessary, controlled, but also—as mentioned above—the at least one property of the applied adhesive to be checked and controlled as close as possible to the joining point (where the coating material is pressed onto the workpiece).

[0015] To achieve these advantages, it has proven sufficient, according to a further development of the invention, for at least one property to be detected point- or line-wise by means of the second detection unit. In this way, particularly simple components, such as a pyrometer, can be used for the second detection unit. The detection result is nevertheless meaningful, since other properties of the applied adhesive – such as surface area and layer thickness – can already be detected upstream by means of the first detection unit.

[0016] Furthermore, according to a further development of the invention, the device includes a control unit for controlling at least one unit, selected from the adhesive application unit, the reactivation unit, and the delivery unit. In this way, a high-quality bond with high reproducibility can be ensured precisely and without (necessary) user intervention. It has proven particularly advantageous that the control unit is configured to receive a detection result from the first and / or second detection unit and, based on this, to control at least one of the units.

[0017] In addition to these control tasks, the control unit can also perform further tasks according to a further development of the invention. In particular, the control unit can be configured to receive a data acquisition result from the first and / or second acquisition unit and, based on this, output information, especially to an operator and / or a database. Such information output allows necessary measures to be initiated early to maintain joining quality and reproducibility, such as initiating and preparing maintenance or repairs. The output information can also be used to reject tools as scrap based on certain data acquisition results. Furthermore, the results from one or more devices can be evaluated in a database and used as a basis for further optimization of the coating process.

[0018] The reactivation unit can be configured in various ways within the scope of the invention. However, with a view to achieving an effective, gentle and uniform reactivation of the applied adhesive, it is preferred that the energy source be selected from an infrared source, laser source, microwave source, hot gas source or combinations thereof.

[0019] A method for coating a workpiece is defined in claim 11. This method is characterized by the fact that the at least one detected property is compared with a target value, and suitable measures are taken based on this comparison. If the at least one detected property deviates from the respective target value by more than a predetermined amount, the applied adhesive is reactivated accordingly. Alternatively or additionally, the properties can also be adjusted during the application of the adhesive, for example, by increasing or decreasing the temperature and / or layer thickness of the adhesive being applied.

[0020] Within this concept, according to a further development of the invention, a target-actual comparison with a second predetermined value can also take place. That is, if the at least one detected property deviates from the respective target value by more than a second predetermined value, the corresponding workpiece is identified as scrap and rejected. Alternatively or additionally, the deviation by more than the second predetermined value can also serve as a trigger for the output of certain information (typically the first and / or second detected property), in particular to an operator and / or a database. This allows the advantages already described above to be achieved particularly effectively and without the need for user intervention. Brief description of the drawings

[0021] Fig. 1 schematically shows a top view of a device for coating a workpiece according to an embodiment of the invention. Detailed description of preferred embodiments

[0022] Embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0023] A device 1 for coating a workpiece 2 is in Fig. 1 The device 1 is shown schematically in a top view. It is used for coating workpieces made of materials such as wood, wood-based materials, plastics, or various composite materials, as commonly used in the furniture and building component industries.

[0024] The workpiece 2 is to be coated with a coating material 4, which can be, for example, in the form of a web or strip. In the present embodiment, the coating material 4 is to be applied to a narrow surface 2' of the workpiece, although alternatively or additionally, a broad surface or other workpiece surfaces can also be coated. The coating material can consist, for example, of plastic, veneer, aluminum, paper, and a variety of other materials and material combinations.

[0025] As in Fig. 1 As can be seen, the device 1 initially comprises an adhesive application unit 10 for applying an adhesive 6 to the surface 2' of the workpiece 2 to be coated. Although in Fig. 1Not shown, an adhesive can alternatively or additionally be applied to a joining surface 4' of the coating material 4 facing the workpiece 2. The adhesive can be, for example, a hot melt adhesive. To melt the adhesive, the adhesive application unit 10 has a melting unit that melts an adhesive, for example, in the form of granules, and feeds it to an application roller 14, which applies the melted adhesive 6 to the narrow surface 2' of the workpiece.

[0026] Furthermore, the device 1 comprises, in a known manner, a pressure unit 20 with several pressure rollers for pressing the coating material 4 onto the workpiece 2, while it is operated by means of a Fig. 1The illustrated conveying unit 30 is guided along the pressure unit 20. In the present embodiment, the conveying unit 30 is shown as a continuous conveying unit, which moves the respective workpiece from right to left. Fig. 1 The conveying unit 30 transports the workpiece in a continuous direction. It can, for example, comprise conveyor chains, conveyor belts, conveyor belts, or other suitable conveying means. Alternatively or additionally, the conveying unit 30 can also serve to move the pressure unit 20 and, optionally, the adhesive application unit 10 and other components relative to a stationary or, within limits, movable workpiece 2. Hybrid forms of both concepts are also possible within the scope of the invention.

[0027] In the present embodiment, a reactivation unit 50 is located between the adhesive application unit 10 and the pressure unit 20 for at least partially reactivating the applied adhesive 6. In the present embodiment, reactivation primarily involves reheating or keeping the applied adhesive 6 warm, although the invention is not limited to this. For this purpose, the reactivation unit 50 can have a suitable energy source, such as an infrared source, a laser source, a microwave source, a hot gas source, or various other energy sources and combinations thereof.

[0028] Upstream of the adhesive application unit 10, a preheating unit 80 is provided in the present embodiment. This unit serves to preheat the workpiece surface 2' to be coated if necessary, for example, if the workpiece was previously stored at a cool temperature. This prevents excessive cooling of the adhesive 6 applied to the narrow surface 2'. The preheating unit 80 can have a similar design to the reactivation unit 50.

[0029] Furthermore, in the present embodiment, the device 1 comprises two detection units 40, 60 for detecting at least one property of the applied adhesive 6. Various properties of the adhesive can be detected, such as temperature, layer thickness, or surface area. For this purpose, the first detection unit 40 in the present embodiment includes a digital camera, in particular a thermal imaging camera, which scans the adhesive applied to the surface 2' of the workpiece 2 to be coated. In addition to temperature, the camera is capable of detecting the surface structure and, for example, providing information as to whether the entire surface 2' to be coated is covered with adhesive 6 and whether the adhesive application is uniform. Furthermore, conclusions can also be drawn about the layer thickness, for example, based on the cooling behavior of the applied adhesive 6.The first detection unit 40 scans the applied adhesive 6 in an area between the adhesive application unit 10 and the reactivation unit 50.

[0030] In the present embodiment, the second detection unit 60 comprises a pyrometer with a point-shaped measuring beam, which thus scans the surface 2' of the workpiece 3 in a line-like pattern when the workpiece 3 is moving. The main function of the pyrometer 60 is therefore to perform a final check of the temperature of the applied adhesive 6, which may be reactivated by the reactivation unit 50. To obtain the most meaningful results for the joining process, the pyrometer scans an area immediately upstream of the pressure unit 20, i.e., immediately upstream of the so-called joining point. This allows the second detection unit 60 to provide particularly meaningful results regarding the quality and reproducibility of the joint between the coating material 4 and the workpiece 2. At the same time, the pyrometer 60 is compact enough to be accommodated within the narrow joining gap between the coating material 4 and the workpiece 2.to perform a scanning. In contrast, with the concept of the present invention, the first detection unit 40, which has larger dimensions and in which the relative positioning to the workpiece surface also plays a greater role for the accuracy of the detection results, can be positioned more freely and does not have to be integrated into the narrow joining gap.

[0031] Furthermore, in the present embodiment, the device 1 comprises a control unit 70 for controlling the various units of the device, such as, in particular, the adhesive application unit 10, the reactivation unit 50, the preheating unit 80, and also the conveying unit 30. For this purpose, the control unit 70 is connected to these units, although this is not necessary in Fig. 1This is only indicated. Furthermore, the control unit 70 is also connected to the first and second detection units 40, 60 and thus receives the respective detection results of at least one property of the applied adhesive 6. On this basis, and possibly taking into account other parameters, influencing factors and specifications, the control unit 70 controls the aforementioned units of the device. 1. The control unit 70 can output the recording results themselves or derived information such as warnings, maintenance requirements, repair requirements or the like to an operator and / or a database.

[0032] The control unit 70 allows for the storage of target values ​​for one or more properties of the applied adhesive 6, such as a target temperature, a target layer thickness, etc. Furthermore, source values ​​or bandwidths can also be stored, and if these are exceeded, the control unit 70 initiates specific actions. For example, if at least one detected property deviates from the respective stored target value by more than a first predetermined value, a suitable control command can be issued to the reactivation unit 50 and / or the adhesive application unit 10. Thus, if, for example, one of the actual temperatures measured by the first detection unit 40 and the second detection unit 60 deviates from the stored target temperature by more than, say, 5°C, the control unit 70 activates the reactivation unit 50 to perform a more intensive reactivation of the applied adhesive 6.Alternatively or additionally, the control unit 70 can also control the adhesive application unit 10 to increase the heating of the adhesive by the melting unit 6 and to apply the adhesive to the workpiece 2 at a higher initial temperature.

[0033] Furthermore, it may occur that the measures described above are insufficient to keep the measured temperature of the adhesive 6 sufficiently close to the stored target value. If the measured temperature deviates from the stored target value by more than, for example, 10°C, the control unit 70 can initiate further measures. For example, the control unit 70 can mark the corresponding workpiece as scrap and reject it. Alternatively or additionally, a warning message can be issued to an operator and / or a database so that appropriate measures can be taken.

[0034] The design and method according to the invention ensure a high quality of the joint between coating material 4 and workpiece 2 and increase reproducibility. At the same time, possible deviations in the joining process can be detected and addressed early on, thus minimizing operational disruptions and workpiece scrap.

Claims

1. A device (1) for coating a workpiece (2), which preferably consists at least in sections, of wood, wood-based material, plastic or the like, with a coating material (4), comprising: an adhesive application unit (10) for applying an adhesive (6) to a surface (2') of the workpiece (2) to be coated and / or a joining surface (4') of the coating material (4), a pressing unit (20) for pressing the coating material (4) onto the workpiece (2), and a conveyor unit (30) for bringing about a relative movement between the pressing unit (20) and the workpiece (2), characterised in that the device has a first detection unit (40) for detecting at least one property of the applied adhesive (6), and a reactivation unit (50) for at least partially reactivating the applied adhesive (6), wherein the first detection unit (40) is configured to detect the at least one property of the applied adhesive (6) in a region between the adhesive application unit (10) and the reactivation unit (50).

2. The device according to claim 1, in which the first detection unit (40) is configured to detect the temperature and / or layer thickness of the applied adhesive (6).

3. The device according to claim 1 or 2, in which the first detection unit (40) is configured to detect the at least one property of the applied adhesive (6) over a surface, in particular over the entire surface, and preferably has a camera.

4. The device according to any one of the preceding claims, in which a second detection unit (60) is provided for detecting at least one property, in particular temperature, of the applied adhesive (6).

5. The device according to claim 4, in which the second detection unit (60) is configured to detect the at least one property of the applied adhesive (6) in a region between the reactivation unit (50) and the pressing unit (20).

6. The device according to claim 4 or 5, in which the second detection unit (60) is configured to detect the at least one property in the form of a point or line and preferably has a pyrometer.

7. The device according to any one of the preceding claims, in which a control unit (70) is provided for controlling at least one unit, selected from the adhesive application unit (10), the reactivation unit (50) and the conveyor unit (30).

8. The device according to claim 7, in which the control unit (70) is configured to receive a detection result of the first and / or second detection unit (40, 60) and to control at least one of the units (10, 50, 30) on this basis.

9. The device according to claim 7 or 8, in which the control unit (70) is configured to receive a detection result of the first and / or second detection unit (40, 60) and to output information on this basis, in particular to an operator and / or a database.

10. The device according to any one of the preceding claims, in which the reactivation unit (50) has at least one energy source, which is preferably selected from an infrared source, a laser source, a microwave source, a hot gas source, or a combination thereof.

11. A method for coating a workpiece (2), which preferably consists at least in sections of wood, wood-based material, plastic or the like, with a coating material (4), in particular using a device (1) according to any one of the preceding claims: applying an adhesive (6) to a surface (2') of the workpiece (2) to be coated and / or a joining surface (4') of the coating material (4), detecting at least one property of the applied adhesive (6), comparing the at least one detected property with a target value, and if the at least one detected property deviates from the respective target value by more than a first predetermined value: - reactivating the applied adhesive (6), and / or - adjusting the properties of the adhesive (6) during application.

12. The method according to claim 11, in which, if the at least one detected property deviates from the respective target value by more than a second predetermined value: - the corresponding workpiece (2) is ejected, and / or - information is output, in particular to an operator and / or a database.