METHOD AND DEVICE FOR COATING A WORKPIECE

Abstract

Method for coating a workpiece which preferably consists at least in sections of wood, wood-based materials, plastic or the like, comprising the steps of: supplying a coating material to a surface to be coated of the workpiece, and bonding the coating material to the surface to be coated using a bonding agent.

Claims

1. Method for coating a workpiece comprising the steps of: supplying a coating material to a surface of the workpiece, and bonding the coating material to the surface using a bonding agent.

2. Method according to claim 1, wherein the bonding agent comprises at least two bonding agent components, with the adhesiveness of the bonding agent being increased by combining the components.

3. Method according to claim 2, wherein at least one first bonding agent component comprises resin.

4. Method according to claim 3, wherein at least one second bonding agent component is selected from gas, comprising air, moisture, hardener and combinations thereof.

5. Method according to claim 4, wherein the bonding agent or at least one bonding agent component comprises a thermally activatable adhesive.

6. Method according to claim 5, wherein the second bonding agent component, is applied to the surface to be coated of the workpiece and/or the surface to be bonded of the coating material.

7. Method according to claim 6, wherein the first bonding agent component, is supplied as a web-shaped or strip-shaped material.

8. Method according to claim 7, wherein the bonding agent is made adhesive by mechanical force.

9. Method according to claim 8, wherein the bonding agent or at least one bonding agent component is stored in an adhesive state and supplied to the bonding process.

10. Method according to claim 9, wherein the adhesive bonding agent is provided in the stored state with an anti-adhesion cap, which is removed before the bonding process is carried out.

11. Method according to claim 10, wherein the adhesive bonding agent is provided on the surface to be bonded of the coating material or as a separate web-shaped or strip-shaped material.

12. Method according to claim 11, wherein the bonding agent or at least one bonding agent component is applied to the surface to be bonded of the coating material and/or the surface to be coated of the workpiece by way of a drop-on-demand method.

13. Method according to claim 12, wherein the bonding agent or at least one bonding agent component has a temperature of at least 30° C.

14. Method according to claim 13, wherein the bonding agent or at least one bonding agent component has a viscosity of at least 30 mPa s.

15. Method according to claim 14, wherein the bonding agent or at least one bonding agent component is brought into a web-shaped or strip-shaped form prior to bonding and subsequently, in the course of the further bonding process, is no longer supplied with thermal energy.

16. Method according to claim 15, wherein the bonding agent or at least one bonding agent component is brought into a web-shaped or strip-shaped form prior to bonding, which form has a mass per unit area of at most 150 g/m2.

17. Device for coating a workpiece for carrying out the method according to claim 1, comprising a means for supplying a coating material to a surface to be coated of the workpiece, a means for bonding the coating material to the surface to be coated using a bonding agent, and a conveying means for causing a relative movement between the workpiece and the bonding means.

18. Device according to claim 17, wherein the device comprises a DoD application unit which is configured to apply the bonding agent or at least one bonding agent component to the surface to be bonded of the coating material and/or the surface to be coated of the workpiece by way of a drop-on-demand method.

19. Device according to claim 18, wherein the DoD application unit comprises at least one microactuator for discharging the bonding agent or at least one bonding agent component.

20. Device according to claim 19, wherein the DoD application unit comprises a liquefaction means which is configured to increase the viscosity of the bonding agent or at least one bonding agent component.

21. Device according to claim 20, wherein the device further comprises a liquefaction unit upstream of the DoD application unit, which unit is configured to increase the viscosity of the bonding agent or at least one bonding agent component.

22. Device according to claim 21, wherein the device further comprises a sealing means for sealing off the bonding agent or at least one bonding agent component contained in the DoD application unit from the environment.

23. Device according to claim 22, wherein the device further comprises a mixing means for mixing a plurality of supplied bonding agents or bonding agent components.

24. Device according to claim 23, wherein the device comprises a supply means for supplying and storing at least one bonding agent or at least one bonding agent component.

25. Device according to claim 24, wherein the supply means supplies a plurality of bonding agents or bonding agent components having different properties.

26. Device according to claim 25, wherein the device further comprises a cleaning means for the DoD application unit.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0032] FIG. 1 schematically shows a first embodiment of the device according to the invention;

[0033] FIG. 2 schematically shows a second embodiment of the device according to the invention and a side view of a coating material;

[0034] FIG. 3 schematically shows a third embodiment of the device according to the invention;

[0035] FIG. 4 schematically shows a fourth embodiment of the device according to the invention;

[0036] FIG. 5 schematically shows a fifth embodiment of the device according to the invention;

[0037] FIG. 6 schematically shows a detailed view of the device shown in FIG. 5; and

[0038] FIG. 7 schematically shows a sixth embodiment of the device according to the invention.

DETAILED DESCRIPTION OF PREFERRED EMBODIMENTS

[0039] In the following, preferred embodiments of the invention will be described in detail with reference to the accompanying drawings.

[0040] A device 20 for coating a workpiece 1 as according to a first embodiment is schematically shown in FIG. 1 in plan view. The device 20 is used for coating a workpiece 1 which can consist, entirely or in part, of wood, wood-based materials, plastic or similar materials, for example. Such workpieces are widely used in the field of the furniture and components industry and are often provided with a coating material on their narrow and/or wide surfaces, which coating material can fulfil both decorative and technical purposes, such as protection against mechanical loads, moisture, heat and the like.

[0041] In the present embodiment, the device 20 comprises a means 22 for supplying a coating material 2 to a surface 1′ to be coated of the workpiece 1, which in the present embodiment comprises a plurality of supply rollers. Furthermore, although not shown in FIG. 1, the supply means 22 may also contain a supply of coating material which may be in the form of one or more rollers or containers, for example. Moreover, the supply means 22 can also be configured to supply, in alternating operation, different coating materials as required, and to this end it may comprise a plurality of supply lines.

[0042] Furthermore, the device 20 comprises a means 24 for bonding the coating material 2 to the surface 1′ to be coated using a bonding agent 10, which in the present embodiment comprises one or more pressing rollers 24.

[0043] Moreover, the device 20 comprises a conveying means 26 for causing a relative movement between the workpiece 1 and the bonding means 24. In the present embodiment, these are configured as a so-called continuous conveying means, with which the workpieces 1 are conveyed along a bonding means 24 which is stationary or movable within limits. It should be noted, however, that in the context of the present invention other conveying concepts are also possible, such as, for example, so-called stationary machines, with which the workpiece 1 to be coated is arranged in a substantially stationary manner and the bonding apparatus 24 is moved relative to the workpiece 1 (cf. also FIG. 7 in this regard). Combinations of this concept are also possible.

[0044] As can be seen from FIG. 1, the coating material 2 is bonded to the surface 1′ to be coated of the workpiece 1 using a bonding agent 10, which can be provided on the surface 1′ to be coated and/or on the facing surface of the coating material 2 as strips or webs, for example. What is decisive here is that the bonding agent 10 is present as strips or webs, such that in the course of the further bonding process it no longer needs to be supplied with energy (such as thermal energy). Accordingly, the device 20 shown in FIG. 1 is also free of a corresponding energy source such as a laser or hot air assembly, for example.

[0045] To realize this concept, various bonding agent systems can be considered; some examples of these will be described in the following with reference to FIGS. 2 to 6.

[0046] In the embodiment shown in FIG. 2, the bonding agent 10 comprises two bonding agent components 12 and 14, wherein the adhesiveness of the bonding agent 10 formed is increased by combining components 12 and 14. The first bonding agent component 12 may comprise, for example, a resin, in particular synthetic resin. In contrast, a second bonding agent component 14 can be selected from gas, such as, in particular, air, moisture, hardener and combinations thereof. This means that the first bonding agent component 12 can react for example with the ambient air and possibly the moisture contained therein in order to increase the adhesiveness of the bonding agent 10 formed as a result. Alternatively or additionally, it is also possible for the second bonding agent component 14 to be removed from the surface 1′ to be coated of the workpiece 1, for example in the form of moisture, binding agent or hardener, which are present in the workpiece 1. In this regard it should be noted that each of the two bonding partners (coating material 2 and workpiece 1) can be provided with both a first bonding agent component 12 and a second bonding agent component 14 and optionally also further bonding agent components, and that these bonding agent components are either provided separately or they are already intrinsically contained in one or both bonding partners.

[0047] In the embodiment illustrated in FIG. 3, the bonding agent 10 is present as a web-shaped material (for coating wide surfaces) or as a strip-shaped material (for coating narrow surfaces). For this purpose, the coating device 20 shown in FIG. 3 comprises a supply means 80 for the web-shaped or strip-shaped bonding agent 10, in order to feed said bonding agent into the join gap between the workpiece 1 and the coating material 2. In this regard it should be noted that one or more bonding agent components 12, 14 can also be supplied in a web-shaped or strip-shaped form instead of a bonding agent 10.

[0048] A further distinctive feature of the embodiment shown in FIG. 3, which does not require a web-shaped or strip-shaped form of the bonding agent 10 either structurally or functionally, however, is the property of the bonding agent 10 of being able to be made adhesive by mechanical force, such as, in particular, by the application of pressure. For this purpose, with the coating device 20 shown in FIG. 3 an increased pressing force F can be applied by means of the pressing roller 24 shown in the drawing to the bonding agent 10 (which can optionally be formed from a plurality of bonding agent components 12, 14), such that the bonding agent 10 develops the desired adhesive effect. For this, substances may be encapsulated in the bonding agent 10, for example, which are released by the application of pressure and which result in an increased adhesive effect.

[0049] The embodiment illustrated in FIG. 4 of the device 20 according to the invention is based on the embodiment shown in FIG. 3, but it additionally comprises a means 82 for removing and storing an anti-adhesion cap 16. The reason for this is that in the embodiment shown in FIG. 4, the bonding agent 10 or at least one bonding agent component is already stored in an adhesive state in the means 80 and supplied to the bonding process. In order to prevent self-adhesion of the web-shaped or strip-shaped bonding agent with this concept, the bonding agent 10 or the corresponding bonding agent component has in the stored state an anti-adhesion cap 16. As soon as the adhesive bonding agent 10 has been supplied to the bonding process, the anti-adhesion cap 16 is removed by the means 82 and stored/disposed of or re-used.

[0050] A fourth preferred embodiment of the coating device 20 according to the invention is shown in FIG. 5. This is characterized inter alia in that it comprises a DoD application unit 30, which is configured to apply the bonding agent 10 or at least one bonding agent component to the surface to be bonded of the material 2 and/or to the surface to be coated of the workpiece 1 by means of a drop-on-demand method. The bonding agent or at least one bonding agent component may be, for example, a thermally activatable adhesive such as, in particular, a hot-melt adhesive, which is preferably selected from thermoplastic polyurethane, EVA, polyolefin, polypropylene, polyamide and polyacrylate.

[0051] Further details of the DoD application unit 30 and other components linked thereto are schematically shown in FIG. 6. In the present embodiment, the DoD application unit 30 comprises a plurality of microactuators 32 which are configured as piezo actuators, for example, and which are used for discharging the bonding agent 10 or at least one bonding agent component 12, 14 via discharge openings 33. The microactuators 32 are controlled by means of a control device, which is not shown, and can also be controlled individually, so that, where necessary, just some the discharge openings 33 are used for discharging a bonding agent or at least one bonding agent component. This allows, for example, the desired application width of the bonding agent or bonding agent component to be adjusted, optionally in combination with a positional adjustment of the DoD application unit. Furthermore, the selective controllability of the microactuators 32 can also be used to discharge different application amounts through the discharge openings 33, for example to adapt in a targeted manner the application amount to the coating material and/or the workpiece to the respective requirements (such as the porosity of the workpiece or particular imperviousness requirements at the edges).

[0052] Although not shown in FIG. 6, the DoD application unit 30 can also comprise discharge openings 33 on different side surfaces, for example to simultaneously provide both the coating material and the workpiece 1 with bonding agent or with the same or different bonding agent components (cf. also FIG. 5). Alternatively, it is, of course, also possible to provide a plurality of independent DoD application units 30.

[0053] Moreover, in the present embodiment the DoD application unit 30 comprises a liquefaction means 34, which is used to liquefy supplied bonding agent or at least one supplied bonding agent component by way of heating, thereby adjusting it to the desired viscosity. A further liquefaction or heating unit 40 is arranged upstream of the DoD application unit and also serves to adjust the viscosity of the bonding agent to the respective requirements in a targeted manner, such that overall a multi-stage liquefaction process results in the present embodiment.

[0054] Furthermore, in the embodiment shown in FIG. 6, the coating device 20 comprises a supply means 60 for supplying and in the present case also storing a plurality of bonding agents 10 or bonding agent components 12, 14.

[0055] In the present embodiment, the supply means 60 contains a plurality of different bonding agents 10 or bonding agent components 12, 14 of different colors, such as black (B), cyan (C), magenta (M) and yellow (Y). However, it is also possible to provide completely different bonding agent categories here, such that different bonding technologies can be alternated between depending on requirements (such as type of workpiece and intended use).

[0056] For this reason, the DoD application unit 30 comprises a mixing chamber 50, as shown in FIG. 6, in which the various bonding agents 10 or bonding agent components 12, 14 supplied via the supply means 60 can be mixed in a targeted manner to set the desired color, for example, or to allow bonding agent components to react with one another to form a bonding agent.

[0057] In the region of the discharge openings 33, the DoD application unit comprises a sealing means 36 which in the present embodiment is formed as a slider or valve through which the bonding agent contained in the DoD application unit 30, or at least one bonding agent component 12, 14 contained in said bonding agent, can be sealed off from the environment.

[0058] Furthermore, a cleaning means 70 is provided, which in the present embodiment is configured as a rinsing means. This is connected to the supply lines of the DoD application unit, such that, where necessary, a rinsing agent or cleaning agent such as a suitable fluid can be supplied and discharged via the discharge openings 33 in order to clean the DoD application unit 30.

[0059] The operation of the coating device 20 shown in FIGS. 5 and 6 is carried out as follows, for example. The adhesive 10 stored in the supply means 60 is initially pre-heated in the heating unit 60 to a temperature of 50° C., for example, and is subsequently supplied to the heating means 34 in order to be heated there to a processing temperature of 100° C., for example. In this state, the bonding agent 10 is fed from the various (colored) strands into the mixing chamber 50, in order to set the desired color of the bonding agent or other properties of the bonding agent there depending on the workpiece. Next, by activating the microactuators 32 the bonding agent 10 is applied via the discharge openings 33 to the surface 1′ to be coated of the workpiece 1 and/or to the facing surface of the coating material 2, in order to be present there in a web-shaped or strip-shaped form.

[0060] Now, the coating material 2 is pressed onto the surface 1′ to be coated of the workpiece 1 by means of the pressing roller 24. In this stage of the procedure, from forming a web-shaped or strip-shaped bonding agent film or bonding agent component film, no further energy input is required, and therefore there is no need for a separate energy source.

[0061] Alternatively or additionally to setting the temperature, the viscosity can also be set in a targeted manner by means of the heating unit 40 and the heating means 34 to advantageous values which, depending on the bonding agent or bonding agent components, may lie in the region of at least 30 mPa s, preferably at least 50 mPa s and/or at most 800 mPa s, preferably at most 500 mPa.

[0062] A further embodiment of the coating device 20 according to the invention is schematically shown in FIG. 7 in plan view. This is characterized in that the conveying means, which is not shown in any more detail, serves to move the bonding means 24 along a workpiece 1 which is arranged in a substantially stationary manner (a so-called “stationary machine”). To this end, in the embodiment shown in FIG. 7 a plurality of components such as, in particular, the bonding means 24 and the supply means 22, are arranged on a common carrier 100 which can be moved along the workpiece 1 and optionally also around the workpiece 1. For this, the carrier 100 can be mounted onto a beam-shaped guiding means (not shown) such as a gantry or a cantilever, or also onto a robot arm or the like. The carrier 100 can also be exchanged for a spindle unit 20 of a machining unit arranged on a guiding means, for which tool or machining assemblies can also be exchanged.

[0063] In the present embodiment, a DoD application unit 30 is advantageously also arranged on the carrier 100. Depending on the bonding agent technology, this can also be omitted, however.