Device for coating a workpiece

Abstract

A device (1) for coating a workpiece (2), which preferably consists of wood, wood material, plastic or the like, at least in some sections, comprises a pressing unit (10) for pressing a coating material (4) onto a surface (2') to be coated of the workpiece (2), a conveying unit (20) for creating a relative movement between the workpiece (2) and the pressing unit (10) in a conveying plane, and at least one sensor (30), more particularly a temperature sensor, for capturing an operating parameter, more particularly temperature, of an adhesive (4') that is provided to adhesively attach the coating material to the workpiece. The at least one sensor (30) has a main measurement direction (32) that is at an angle to the conveying plane, at least in the region of the adhesive.

Description

[0001] Device for coating a workpiece

[0002] Technical area

[0003] The invention relates to a device and a method for coating a workpiece which preferably consists at least in sections of wood, wood materials, plastic or the like.

[0004] State of the art

[0005] In the furniture and construction component industries, workpieces are often coated on one of their surfaces, for example, an edge. The coating material is usually applied using a suitable joining or bonding tool.

[0006] Adhesive which is applied to the workpiece or to the coating material, for example in the form of hot melt adhesive.

[0007] Alternatively, it is also common to provide the joining or bonding agent in advance on the coating material or the workpiece or to form it integrally with them. In this case, the joining agent is activated or kept activated during the coating process by means of a suitable device, usually heated by means of a suitable energy source. Lasers and hot air units in particular have proven to be popular as energy sources, although numerous other technologies such as microwaves, infrared, plasma, ultrasound or the like are also possible. For the quality of the coating result, it is crucial, among other things, that the joining agent is heated to the appropriate temperature or temperature window. Against this background, DE 10 2017 122 701 A discloses a coating device according to the preamble of claim 1, in which the temperature of the joining agent is monitored by a temperature sensor.However, it has been shown in practice that the measurement results of the temperature sensor are susceptible to fluctuations, so that the desired optimization of the joining agent temperature cannot be achieved with sufficient reliability.

[0008] Furthermore, DE 10 2019 133 934 A discloses a generic device in which a sensor measures the temperature of the adhesive through a hot air nozzle. However, it has been shown that such devices have a comparatively complex design. Furthermore, the measurement results often do not achieve the desired accuracy.

[0009] Description of the invention

[0010] The invention is based on the object of providing a device of the type mentioned at the outset which, with a simple construction, enables precise monitoring of at least one operating variable of the adhesive.

[0011] This object is achieved according to the invention by a device for coating a workpiece according to claim 1. Preferred developments of the invention are specified in the dependent claims.

[0012] The invention is based on the idea of ​​taking into account the exceptionally difficult conditions and tight space conditions in the area of ​​the pressing unit by means of a novel arrangement in which the at least one sensor or its imaginary sensor beam is guided out of the plane of the workpiece to be coated. To this end, the invention provides that, in a generic device, the at least one sensor has a main measuring direction which, at least in the area of ​​the adhesive, is at an angle to the conveying plane.

[0013] The inventive design provides completely new arrangement options for the at least one sensor without requiring complex additional components. The angled arrangement of the main measuring direction makes it possible to integrate the at least one sensor not into the narrow joining gap, but rather at any location, which can also be located at a greater distance from the joining area. This protects the at least one sensor from excessive contamination or temperature fluctuations, allowing for significantly increased precision of the measurement result.

[0014] Furthermore, the angular arrangement of the main measuring direction also allows measurements to be taken particularly close to the actual joining point and thus particularly meaningful measurement results to be obtained.

[0015] Precise and meaningful measurement results are not an end in themselves, but represent an important basis for achieving a high-quality joining result between the workpiece and the coating material.

[0016] According to a further development of the invention, the main measuring direction of the at least one sensor has an angle α of at least 10° with respect to the conveying plane, at least in the region of the adhesive. This allows an imaginary measuring beam extending along the main measuring direction to be introduced particularly effectively into the usually narrow joint gap between the workpiece and the coating material, while achieving the above-mentioned advantages. Alternatively or additionally, according to a further development of the invention, the main measuring direction of the at least one sensor has an angle α of at most 40°, preferably at most 30° with respect to the conveying plane, at least in the region of the adhesive. In this context, the inventors have found that larger angles do not generally lead to the above-mentioned advantages becoming even more pronounced.However, larger angles beyond the ranges mentioned would increasingly lead to reduced measurement precision, which should be avoided as far as possible within the scope of the invention.

[0017] The at least one sensor can, in principle, measure the operating variable of the adhesive at any location. However, according to a further development of the invention, the at least one sensor is configured to measure the operating variable of the adhesive in the area of ​​the pressure unit or the corresponding joining point. This yields particularly meaningful measurement results, which represent a good basis for achieving high joining quality.

[0018] In order to achieve precise and reliable measurement results in continuous operation, according to a further development of the invention, the sensor comprises a pyrometer and / or bolometer and / or a semiconductor sensor.

[0019] Furthermore, according to a development of the invention, the at least one sensor is provided with a focusing device which is preferably designed to focus an imaginary measuring beam of the sensor towards the adhesive to be measured. This configuration contributes to precise measuring results, among other things because the imaginary measuring beam can be directed particularly precisely to suitable measuring points. On the other hand, the focusing also allows the geometry of the imaginary measuring beam to be adapted to the spatial conditions in the narrow joining gap and to make the imaginary measuring beam narrower, for example in the area of ​​the joining gap, so that it can reach the adhesive layer to be measured without collision. This makes a significant contribution to achieving the advantages mentioned above.

[0020] According to a further development of the invention, the device has an adjustable guide, in particular a hold-down device, for the coating material, with at least one sensor being attached to the adjustable guide. The use of an adjustable guide firstly enables flexible adaptability of the device according to the invention to changing geometries of the workpiece or of the coating material. Furthermore, the attachment of at least one sensor to the adjustable guide allows the position of the sensor to adapt automatically to the changing geometries of the coating material, which in turn contributes to a precise and meaningful measurement result.

[0021] Furthermore, according to a further development of the invention, at least one sensor is mounted on a holder that has a comparatively low thermal conductivity. This prevents the sensor mounted on the holder from being exposed to excessive temperature influences, which in turn improves measurement accuracy and increases the service life of the sensor.

[0022] Furthermore, according to a further development of the invention, at least one sensor can have a protective sheath, preferably made of a material with high thermal conductivity, such as aluminum. This measure, which initially sounds paradoxical, results in any heat applied to the sensor being evenly distributed within the protective sheath, resulting in a uniform heating of the sensor. This further increases the measurement accuracy, since inhomogeneous heating of the sensor would impair the measurement accuracy.

[0023] It is particularly preferred that the protective sheath has a thermal conductivity that is at least 3 times, preferably at least 10 times, greater than the thermal conductivity of the conductor. This results in a good combination of both thermal separation of the sensor from the heat source and, if possible, uniform heating of the sensor.

[0024] According to a further development of the invention, the protective cover has a permeable, particularly transparent, section through which the sensor can measure. This allows effective thermal decoupling of the sensor to be combined with high measurement accuracy.

[0025] In this regard, according to a further development of the invention, it is also provided that the at least one sensor has a shielding unit, such as in particular a protective shield, at least in the measuring direction, which preferably has heat-insulating properties. This allows for effective thermal decoupling of the sensor to be achieved in a simple manner, thereby further increasing the measuring accuracy and the service life of the sensor.

[0026] The inventive concept unfolds its advantages particularly in a device which, according to a further development of the invention, has an adhesive application unit for applying adhesive to the coating material and / or the workpiece and / or which has an adhesive activation unit for activating adhesive. By integrating these units in a device with the at least one sensor, a particularly good coordination of the application and / or activation of the respective adhesive can be achieved, which results in an improved joining result between the workpiece and

[0027] Coating material results in .

[0028] In this respect, according to a development of the invention, the device has an electronic control unit which is connected to at least one sensor and to the adhesive application unit and / or the adhesive activation unit and / or the conveyor unit and is set up to control the adhesive application unit and / or the adhesive activation unit and / or the conveyor unit on the basis of a measurement result obtained from the at least one sensor. In this way, an optimal joining connection between the workpiece and the coating material can be achieved because the operation of the adhesive application unit and / or adhesive activation unit and / or the conveyor unit can be set and, if necessary, regulated in such a way that optimal operating parameters of the adhesive are obtained during joining.Should operating parameters, such as the temperature of the adhesive, deviate from suitable target values, this is detected by the at least one sensor so that the control unit can adapt the operation of the adhesive application unit and / or adhesive activation unit and / or the conveyor unit accordingly in order to bring the actual value closer to the target value.

[0029] A particularly rapid and, with regard to the geometry of the workpiece to be coated, particularly flexible process sequence results if, according to a development of the invention, at least the pressing unit and the at least one sensor in the device can be moved together and rotated about an axis perpendicular to the conveying plane. This means that, for example, round or arbitrarily shaped workpieces can also be reliably coated. Alternatively, however, it is also possible for the pressing unit and the sensor and, if necessary, other components to be arranged stationary and for the workpiece to be moved in relation to these components. Mixed forms of both concepts are also possible within the scope of the invention.

[0030] Short description of the drawings

[0031] Fig. 1 shows schematically a partial perspective view of a device according to an embodiment of the invention;

[0032] Fig. 2 shows schematically a partial plan view of the device shown in Fig. 1.

[0033] Detailed description of preferred embodiments

[0034] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0035] A device 1 for coating a workpiece 2 is shown schematically in a partial perspective view in Fig. 1. The device 1 is used for coating workpieces 2, which preferably consist at least in sections of wood, wood-based material, plastic or the like, as are widely used in the furniture and building element industry. The coating material 4 can, for example, be a narrow-surface coating (edge) made of a wide variety of materials, such as plastic, veneer, paper or metal. Alternatively or additionally, however, a wide surface or any other desired surface of a workpiece 2 can also be provided with a coating material 4.

[0036] Although the present invention is not limited thereto, the coating material 4 in the present embodiment comprises an adhesive 4' provided on the side of the coating material 4 facing the workpiece 2. The adhesive 4' may, for example, be a heat-activated adhesive such as a hot-melt adhesive.

[0037] Alternatively, it is also conceivable for the coating material 4 to have an integral layer 4' which, when activated, develops adhesive properties, such as those on various meltable plastics. The entire coating material 4 can also consist of a corresponding material, so that there is no discrete adhesive layer 4'. The adhesive 4' can also be supplied separately from the coating material 4, for example as an adhesive web or adhesive strip. Furthermore, the adhesive 4' can also be applied to the coating material 4 in a conventional manner by means of an application roller, wherein the component 70 shown in Fig. 1 can then have a corresponding adhesive application unit. Overall, the adhesive can also first be applied to the surface of the workpiece to be coated.

[0038] The coating device 1 comprises a pressing device 10, which in the present embodiment has a pressure roller and serves to press the coating material 4 onto a surface 2' of the workpiece 2 to be coated.

[0039] In addition, the coating device 1 comprises a conveyor unit which, in the present embodiment, is designed in the manner of a so-called stationary machine. The conveyor unit has a support section 20 which, together with the components of the device 1 shown in Fig. 1, can be moved parallel to a conveyor plane and can rotate about an axis (C) perpendicular to the conveyor plane. The conveyor plane corresponds to the plane of the workpiece 2, which is arranged stationary via suitable holding means 2 (not shown). However, the conveyor unit can serve to convey the workpiece 2 and for this purpose can have, for example, a conveyor element in the form of a conveyor belt, conveyor belt, conveyor chain or the like. Mixed variants of the two concepts are also possible within the scope of the invention, wherein the conveyor unit 20 always serves to bring about a relative movement between the workpiece 2 and the pressing device 10.

[0040] In addition, the coating device 1 comprises an adhesive activation unit 70 which, in the present embodiment, comprises a nozzle arrangement 74 for dispensing a heated fluid which serves to activate the adhesive 4'. As can be best seen in Fig. 2, the heated fluid is supplied as a volume flow V via a feed line 72 to the nozzle arrangement 74, with a fluid supply and a heating device, for example, being provided upstream. The fluid supply can advantageously also be a pressurized fluid supply which supplies the fluid to the nozzle arrangement 74 at an overpressure of, purely by way of example, at least 1.5 bar.

[0041] In the simplest case, the heated (pressurized) fluid can be hot air. However, it is equally possible for the fluid to contain other gases and possibly also liquids or liquid droplets. Furthermore, it should be noted that the adhesive activation unit 70 can also comprise a variety of other energy sources, such as a laser source, an LED source, an infrared source, a microwave source, a plasma source, etc.

[0042] As can be seen in Fig. 1, the coating device 1 in the present embodiment has a temperature sensor 30 for detecting a temperature of the adhesive 4', which can be designed, for example, as a pyrometer or bolometer or semiconductor sensor or (thermo-) camera. Alternatively or in addition to the temperature sensor, other sensors for detecting an operating variable can also be used within the scope of the invention, for example for detecting the porosity of the workpiece, the viscosity of the joining agent, the layer thickness of the joining agent or the like.

[0043] The temperature sensor 30 has a main measuring direction 32, which is shown in dashed lines in Fig. 1 and can be regarded as the center line of an imaginary measuring beam 34.

[0044] Although the imaginary measuring beam 34 in Fig. 1 extends in a straight line from the sensor 30 to the adhesive 4 ' to be measured, it is also possible within the scope of the invention to deflect the imaginary measuring beam by suitable means, such as by (at least) one mirror, one prism or other deflection means (not shown).

[0045] As can be best seen in Fig. 1, the imaginary measuring beam 34 strikes the adhesive layer 4' immediately in front of the joining point, at which the coating material 4 and the workpiece 2 are brought into contact with one another. At least in this area, which can also be referred to as the joining gap, the main measuring direction 32 of the sensor 30 has an inclination with respect to the conveying plane and is thus arranged at an angle to the conveying plane. The angle of inclination α between the main ring measuring direction 32 and the conveying plane can be, for example, 20° and is preferably in a range between 10° and 40°, more preferably at most 30°.

[0046] In Fig. 1 it can also be seen that the imaginary measuring beam 34 tapers towards the adhesive layer 4'. This focusing of the imaginary measuring beam is produced by a focusing device 40 which can have, for example, a lens or other suitable focusing elements. In the present embodiment the focusing device 40 is integrated into a holder 50, by means of which the sensor 30 is attached to the device 1. In this case the holder 50 in the present embodiment is attached to a hold-down device 6 which is vertically adjustable and serves to guide the coating material 4 vertically. Due to the vertical adjustability of the hold-down device 6, the holder 50 with the sensor 40 is also vertically adjustable and can therefore be adapted to different coating materials 4.

[0047] In the present embodiment, the holder 50 is made of a material with comparatively low thermal conductivity, such as steel, stainless steel, or a ceramic material. Other suitable materials may, of course, also be used within the scope of the invention.

[0048] In the present embodiment, the sensor 30 is housed in a protective sheath 36, which, in contrast to the holder 50, comprises a material with high thermal conductivity, such as aluminum. The thermal conductivity of the protective sheath 36 in the present embodiment is at least three times, for example, ten times, greater than the thermal conductivity of the holder 50.

[0049] In order to still be able to carry out a measurement, the protective sheath 36 has a transparent section 38 in the measuring direction of the sensor 30, through which the sensor 30 can measure. Furthermore, in the present embodiment, a protective screen 60 is provided in the measuring direction of the sensor 30 as a shielding unit, which preferably also has heat-insulating properties and has a section 62 that is permeable or designed as a free space. The protective screen 60 helps to protect the sensor 30 from heat radiation or convection. Furthermore, the device comprises, as can be seen in Fig. 1, an electronic control unit 80, such as a control computer. The control unit 80 is connected to the sensor 30 and to the adhesive activation unit or adhesive application unit 70 and can also be connected to the conveyor unit 20.The electronic control unit 80 receives measurement data from the sensor 30 regarding the temperature or other important parameters measured by the sensor 30. The electronic control unit 80 can then compare the obtained measured values ​​with suitable target values.

[0050] If the measured values ​​deviate from the target values, the electronic control unit can control or adjust the operating parameters of the adhesive activation unit or adhesive application unit 70 and / or the conveyor unit 20 or other relevant units of the device 1 to ensure that the measured values ​​approximate the desired target values. In this way, not only can the quality of the joining result be monitored, but the operating parameters of the device 1 can also be optimized and, if necessary, controlled fully or partially automatically in order to achieve an optimal coating result.

Claims

CLAIMS Device (1) for coating a workpiece (2), which preferably consists at least in sections of wood, wood material, plastic or the like, comprising: a pressing unit (10) for pressing a coating material (4) onto a surface (2') of the workpiece (2) to be coated, a conveying unit (20) for bringing about a Relative movement between the workpiece (2) and the Pressing device (10) in a conveying plane, and at least one sensor (30), in particular a temperature sensor, for detecting an operating variable, in particular the temperature, of an adhesive (4') which is provided for adhering the coating material to the workpiece, characterized in that the at least one sensor (30) has a main measuring direction (32) which, at least in the region of the adhesive, is at an angle to the conveying plane. Device according to claim 1, in which the main measuring direction (32) of the at least one sensor (30) has an angle (α) of at least 10° with respect to the conveying plane, at least in the region of the adhesive. Device according to claim 1 or 2, in which the main measuring direction (32) of the at least one sensor (30) has an angle (α) of maximum 40°, preferably maximum 30° relative to the Conveying plane. Device according to one of the preceding claims, in which the at least one sensor (30) is arranged to Operating size of the adhesive (4' ) in the area of Pressure unit to measure. Device according to one of the preceding claims, in which the at least one sensor (30) is selected from a pyrometer, bolometer, semiconductor sensor and camera. Device according to one of the preceding claims, in which the at least one sensor (30) has a focusing device (40) which is preferably configured to focus an imaginary measuring beam (34) of the sensor (30) towards the adhesive (4') to be measured. Device according to one of the preceding claims, in which an adjustable guide (6), in particular a hold-down device, is provided for the coating material (4), wherein at least one sensor (30) is attached to the adjustable guide. Device according to one of the preceding claims, in which at least one sensor is attached via a holder (50) which has a comparatively low thermal conductivity and is preferably made of steel, stainless steel or ceramic.Device according to one of the preceding claims, in which at least one sensor (30) has a protective cover (36) which preferably comprises a material with high thermal conductivity, such as in particular aluminum. Device according to claim 9, wherein the protective cover (36) has a thermal conductivity which is at least 3 times, preferably at least 10 times as great as the Thermal conductivity of the holder (50). Device according to claim 9 or 10, wherein the Protective cover (36) has a permeable, in particular transparent section (38) through which the sensor (30) can measure. Device according to one of the preceding claims, in which at least one sensor (30) has a shielding unit, such as in particular a protective screen (60), at least in the measuring direction, which preferably has heat-insulating properties. Device according to one of the preceding claims, in which an adhesive application unit (70) is provided for applying adhesive to the coating material and / or the workpiece, and / or an adhesive activation unit (70) is provided for activating adhesive (4').Device according to one of the preceding claims, in which an electronic control unit (80) is provided which is connected to at least one sensor (30) and to the adhesive application unit and / or the adhesive activation unit (70) and / or the conveyor unit (20) and is configured to control the adhesive application unit and / or the adhesive activation unit (70) and / or the conveyor unit (20) on the basis of a measurement result obtained from the at least one sensor (30). Device according to one of the preceding claims, in which at least the pressing unit (10) and the at least a sensor (3) can be moved together and rotated about an axis (C) perpendicular to the conveying plane.

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