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

Technical field

[0001] The invention relates to a device for coating a workpiece, which preferably consists at least partially of wood, wood-based materials, plastic or the like. State of the art

[0002] In the furniture and building component industries, workpieces are frequently coated on one of their surfaces, for example, an edge. The coating material is typically applied using a suitable adhesive or bonding agent, such as a hot melt adhesive, which is applied to the workpiece or to the coating material.

[0003] Alternatively, it is also common to pre-apply the bonding agent or adhesive to the coating material or workpiece, or to integrate it as an integral part of the process. In this case, the bonding agent is activated or kept activated during the coating process using a suitable device, usually heated by an appropriate energy source. Laser and hot air units have become particularly established as energy sources, although numerous other technologies such as microwave, infrared, plasma, ultrasound, and the like are also suitable.

[0004] For the quality of the coating result, it is crucial, among other things, that the bonding agent is heated to the appropriate temperature or temperature range. 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 material is monitored by a temperature sensor. However, practical experience has shown that the temperature sensor readings are prone to fluctuations, meaning that the desired optimization of the joining material temperature cannot be achieved with sufficient reliability.

[0005] 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. Moreover, the measurement results often do not achieve the desired accuracy.

[0006] Features of a device for coating a workpiece according to the preamble of claim 1 are known from EP 1 800 813 A2. Furthermore, DE 10 2016 213 216 A1 also describes a device for coating a workpiece. Description of the invention

[0007] The invention is based on the objective of providing a device of the type mentioned above which, with a simple design, enables precise monitoring of at least one operating parameter of the adhesive.

[0008] This problem is solved according to the invention by a device for coating a workpiece according to claim 1. Preferred embodiments of the invention are specified in the dependent claims.

[0009] The invention is based on the idea of ​​addressing the exceptionally difficult conditions and limited space in the area of ​​the pressure unit by means of a new arrangement in which the at least one sensor or its imaginary sensor beam is led out of the plane of the workpiece to be coated. For this purpose, the invention provides that, in a device of this type, the at least one sensor has a main measuring direction that is perpendicular to the conveying plane, at least in the area of ​​the adhesive.

[0010] The inventive design offers entirely new arrangement possibilities for the at least one sensor, without requiring complicated 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 at any desired location, even one that is at a greater distance from the joining area. This protects the at least one sensor from excessive contamination or temperature fluctuations, resulting in significantly increased measurement precision.

[0011] Furthermore, the angled arrangement of the main measuring direction also allows for measurements to be taken particularly close to the actual joining point, thus enabling particularly meaningful measurement results.

[0012] 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.

[0013] 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° relative to the conveying plane, at least in the area of ​​the adhesive. This allows an imaginary measuring beam extending along the main measuring direction to be introduced particularly effectively into the usually narrow joining gap between the workpiece and the coating material, while achieving the advantages mentioned above. 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°, relative to the conveying plane, at least in the area of ​​the adhesive. In this context, the inventors have found that larger angles generally do not result in the advantages mentioned above being further pronounced.However, larger angles beyond the aforementioned areas would increasingly lead to reduced measurement precision, which is to be avoided as far as possible within the scope of the invention.

[0014] The at least one sensor can, in principle, measure the operating size of the adhesive at any point. However, according to a further development of the invention, the at least one sensor is configured to measure the operating size of the adhesive in the area of ​​the pressure unit or the corresponding joining point. This results in particularly meaningful measurement results, which provide a good basis for achieving high joining quality.

[0015] In order to achieve precise and reliable measurement results in continuous operation, a further development of the invention provides that the sensor comprises a pyrometer and / or bolometer and / or a semiconductor sensor.

[0016] Furthermore, according to a further development of the invention, the at least one sensor has a focusing device, preferably configured to focus an imaginary measuring beam from the sensor towards the adhesive to be measured. This design contributes to precise measurement results, among other things because the imaginary measuring beam can be directed with particular accuracy 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, making the imaginary measuring beam narrower, for example, in the region 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 aforementioned advantages.

[0017] According to the invention, the device comprises an adjustable guide, in particular a hold-down device, for the coating material, with at least one sensor attached to the adjustable guide. The use of an adjustable guide initially allows the device according to the invention to be flexibly adapted to changing geometries of the workpiece or the coating material. Furthermore, the attachment of at least one sensor to the adjustable guide allows the sensor's position to automatically adjust to the changing geometries of the coating material, which in turn contributes to a precise and meaningful measurement result.

[0018] 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 the measurement accuracy and increases the sensor's service life.

[0019] Furthermore, according to a further development of the invention, at least one sensor can have a protective casing, preferably made of a material with high thermal conductivity, such as aluminum. This initially paradoxical measure ensures that any heat applied to the sensor is distributed evenly within the casing, resulting in uniform heating of the sensor. This further increases the measurement accuracy, as uneven heating of the sensor would impair it.

[0020] It is particularly preferred that the protective casing 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 necessary, uniform heating of the sensor.

[0021] According to a further development of the invention, the protective casing has a permeable, in particular transparent, section through which the sensor can measure. This allows effective thermal decoupling of the sensor to be combined with high measurement accuracy.

[0022] In this respect, a further development of the invention also provides that the at least one sensor has a shielding unit, such as a protective aperture, at least in the measuring direction, which preferably has heat-insulating properties. This allows for effective thermal decoupling of the sensor in a simple manner, thereby further increasing the measuring accuracy and the service life of the sensor.

[0023] The concept according to the invention 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 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, resulting in an improved joining result between the workpiece and the coating material.

[0024] In this respect, a further development of the invention provides that the device has an electronic control unit which is connected to and configured with at least one sensor as well as with the adhesive application unit and / or the adhesive activation unit and / or the conveying unit, and is configured to control the adhesive application unit and / or the adhesive activation unit and / or the conveying unit based on a measurement result obtained from the at least one sensor. In this way, an optimal bond between the workpiece and the coating material can be achieved, since the operation of the adhesive application unit and / or the adhesive activation unit and / or the conveying unit can be set and, if necessary, regulated in such a way that optimal operating parameters of the adhesive are achieved during the joining process.Should operating parameters, such as the temperature of the adhesive, deviate from suitable target values, this is detected by at least one sensor, so that the control unit can adjust the operation of the adhesive application unit and / or adhesive activation unit and / or the conveying unit accordingly in order to bring the actual value closer to the target value.

[0025] A particularly fast and, with regard to the geometry of the workpiece to be coated, especially flexible process sequence is achieved if, according to a further development of the invention, at least the pressure unit and the at least one sensor are jointly movable and rotatable about an axis perpendicular to the conveying plane. This allows, for example, the reliable coating of round or arbitrarily shaped workpieces. Alternatively, it is also possible for the pressure unit and the sensor, as well as any other components, to be arranged in a stationary position and for the workpiece to be moved relative to these components. Hybrid forms of both concepts are also possible within the scope of the invention, provided they fall within the scope of the appended claims. Brief description of the drawings

[0026] Fig. 1 schematically shows a partial perspective view of a device according to an embodiment of the invention; Fig. 2schematically shows a partial top view of the in Fig. 1 device shown. Detailed description of preferred embodiments

[0027] Preferred embodiments of the invention are described in detail below with reference to the accompanying drawings.

[0028] A device 1 for coating a workpiece 2 is in Fig. 1The device 1 is shown schematically in a partial perspective view. It is used for coating workpieces 2, which preferably consist at least partially of wood, wood-based materials, plastic, or the like, as commonly used in the furniture and building component industries. The coating material 4 can, for example, be a narrow-surface coating (edge) made of various materials such as plastic, veneer, paper, or even metal. Alternatively or additionally, a wide surface or any other surface of a workpiece 2 can also be coated with the material 4.

[0029] Although the present invention is not limited to this, in the present embodiment the coating material 4 has an adhesive 4' which is provided on the side of the coating material 4 facing the workpiece 2. The adhesive 4' can, for example, be a heat-activated adhesive such as a hot melt adhesive. Alternatively, it is also conceivable that the

[0030] The coating material 4 has an integral layer 4' which, upon activation, develops adhesive properties, such as various meltable plastics. Alternatively, the entire coating material 4 can consist of a suitable material, so that no discrete adhesive layer 4' is present. 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 using an applicator roller, whereby the Fig. 1 The component shown, 70, can then have a corresponding adhesive application unit. Alternatively, the adhesive can first be applied to the surface of the workpiece to be coated.

[0031] The coating device 1 comprises a pressure 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.

[0032] Furthermore, the coating device 1 includes a conveying unit, which in the present embodiment is designed in the manner of a so-called stationary machine. The conveying unit has a support section 20, which together with the in Fig. 1The components of the device 1 shown are movable parallel to a conveying plane and rotatable about an axis (C) perpendicular to the conveying plane. The conveying plane corresponds to the plane of the workpiece 2, which is stationary via suitable holding means 2 (not shown). The conveying unit can, however, serve to convey the workpiece 2 and for this purpose may, for example, have a conveying element in the form of a conveyor belt, conveyor belt, conveyor chain, or the like. Hybrid versions of both concepts are also possible within the scope of the invention, wherein the conveying unit 20 always serves to bring about a relative movement between the workpiece 2 and the pressure device 10.

[0033] Furthermore, the coating device 1 comprises an adhesion agent activation unit 70, which in the present embodiment includes a nozzle arrangement 74 for dispensing a heated fluid that serves to activate the adhesion agent 4'. As in Fig. 2As can be best seen, the heated fluid is supplied as a volume flow V via a supply line 72 to the nozzle arrangement 74, with, for example, a fluid supply and a heating device 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, for example, at least 1.5 bar.

[0034] The heated (pressure) fluid can, in the simplest case, be hot air. However, it is also possible that the fluid contains other gases and possibly also liquids or liquid droplets. Furthermore, it should be noted that the adhesion promoter activation unit 70 can also include a variety of other energy sources, such as a laser source, an LED source, an infrared source, a microwave source, a plasma source, etc.

[0035] As in Fig. 1As can be seen, the coating device 1 in the present embodiment has a temperature sensor 30 for detecting the temperature of the adhesive 4', which can be designed, for example, as a pyrometer, bolometer, semiconductor sensor, or (thermal) camera. Alternatively or additionally to the temperature sensor, other sensors for detecting an operating parameter can also be used within the scope of the invention, such as the porosity of the workpiece, the viscosity of the adhesive, the layer thickness of the adhesive, or the like.

[0036] The temperature sensor 30 has a main measuring direction 32, which is in Fig. 1 is shown as a dashed line and can be considered the center line of an imaginary measuring beam 34.

[0037] Although the imagined measuring beam 34 is in Fig. 1Extending 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 (at least) a mirror, a prism or other deflecting means (not shown).

[0038] As in Fig. 1 As can be seen most clearly, the imaginary measuring beam 34 strikes the adhesive layer 4' immediately in front of the joining point where the coating material 4 and the workpiece 2 are brought into contact. 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 relative to the conveying plane and is thus arranged perpendicular to the conveying plane. The angle of inclination α between the main ring measuring direction 32 and the conveying plane can, for example, be 20° and is preferably in a range between 10° and 40°, preferably at most 30°.

[0039] In Fig. 1It can further 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 may, for example, comprise 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 the present embodiment, the holder 50 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 thus adaptable to different coating materials 4.

[0040] In the present embodiment, the holder 50 is made of a material with a comparatively low thermal conductivity, such as steel, stainless steel, or a ceramic material. Of course, other suitable materials can also be used within the scope of the invention.

[0041] In the present embodiment, the sensor 30 is enclosed in a protective casing 36, which, unlike the holder 50, is made of a material with high thermal conductivity, such as aluminum. The thermal conductivity of the protective casing 36 in the present embodiment is at least three times, for example ten times, greater than the thermal conductivity of the holder 50.

[0042] To still enable measurement, the protective cover 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 aperture 60 is provided as a shielding unit in the measuring direction of the sensor 30. This aperture preferably also has heat-insulating properties and a transparent section 62, or a section designed as a free space. The protective aperture 60 helps to protect the sensor 30 from thermal radiation or convection.

[0043] Furthermore, the device includes, as described in Fig. 1The electronic control unit 80, such as a control computer, can be identified. The control unit 80 communicates with the sensor 30 and the adhesive activation unit or adhesive application unit 70, and may also communicate with the conveying unit 20. The electronic control unit 80 receives measurement data from the sensor 30 regarding temperature or other important parameters measured by the sensor 30. The electronic control unit 80 can then compare the received measurement values ​​with suitable target values.

[0044] If the measured values ​​deviate from the target values, the electronic control unit can control or adjust the operating parameters of the adhesion promoter activation unit or adhesion promoter application unit 70 and / or the conveying unit 20 or other relevant units of the device 1 in order to bring the measured values ​​closer to the desired target values. In this way, not only can the quality of the joining result be monitored, but the optimization and, if necessary, control of the operating parameters of the device 1 can also be carried out fully or partially automatically to achieve an optimal coating result.

Claims

1. Device (1) for coating a workpiece (2) which preferably consists, at least in sections, of wood, wood-based material, plastic or the like, comprising: a pressing unit (10) for pressing a coating material (4) onto a surface (2') of the workpiece (2) which is to be coated, a conveyor unit (20) for inducing 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 measuring an operating variable, in particular a temperature, of an adhesive (4') intended to bond the coating material to the workpiece, wherein the at least one sensor (30) has a main measuring direction (32) which, at least in the area of the adhesive, is oriented at an angle to the conveying plane, characterised in that an adjustable guide (6), in particular a hold-down device, is provided for the coating material (4), wherein the at least one sensor (30) is attached to the adjustable guide.

2. Device according to claim 1, wherein the main measuring direction (32) of the at least one sensor (30) is, at least in the area of the adhesive, at an angle (α) of at least 10° with respect to the conveying plane.

3. Device according to claim 1 or 2, wherein the main measuring direction (32) of the at least one sensor (30) is, at least in the area of the adhesive, at an angle (α) of no more than 40°, preferably no more than 30°, with respect to the conveying plane.

4. Device according to one of the preceding claims, wherein the at least one sensor (30) is configured to measure the operating variable of the adhesive (4') in the region of the pressing unit.

5. Device according to one of the preceding claims, wherein the at least one sensor (30) is selected from a pyrometer, a bolometer, a semiconductor sensor and a camera.

6. Device according to one of the preceding claims, wherein the at least one sensor (30) has a focusing device (40) which is preferably configured to bundle an imaginary measuring beam (34) of the sensor (30) towards the adhesive (4') to be measured.

7. Device according to one of the preceding claims, wherein at least one sensor is attached via a holder (50) which has a comparatively low thermal conductivity and preferably comprises steel, stainless steel or ceramic.

8. Device according to one of the preceding claims, wherein at least one sensor (30) has a protective sleeve (36) which preferably comprises a material with high thermal conductivity such as aluminium in particular.

9. Device according to claim 8, wherein the protective sleeve (36) has a thermal conductivity that is at least 3 times, preferably at least 10 times, the thermal conductivity of the holder (50).

10. Device according to claim 8 or 9, wherein the protective sleeve (36) has a permeable, in particular transparent section (38) through which the sensor (30) can measure.

11. Device according to one of the preceding claims, wherein at least one sensor (30) has, at least in the direction of measurement, a shielding unit, in particular a protective screen (60), which preferably has thermally insulating properties.

12. Device according to one of the preceding claims, wherein an adhesive application unit (70) is provided for the application of adhesive to the coating material and / or the workpiece, and / or an adhesive activation unit (70) is provided for the activation of adhesive (4').

13. Device according to one of the preceding claims, wherein an electronic control unit (80) is provided which is connected with at least one sensor (30) as well as with the adhesive application unit and / or the adhesive activation unit (70) and / or the conveying unit (20) and is configured to control the adhesive application unit and / or the adhesive activation unit (70) and / or the conveying unit (20) on the basis of a measurement result received from the at least one sensor (30).

14. Device according to one of the preceding claims, wherein at least the pressing unit (10) and the at least one sensor (3) can be moved together and rotated around an axis (C) perpendicular to the conveying plane.

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