Patent Application
20160288408
The invention relates to a method of applying a coating, which preferably consists at least partly of plastic, onto workpieces, which preferably consist at least partly of wood, derived wood products, plastic or the like, in which the coating is activated at least in one bonding region and is bonded to the workpiece in this region. According to the invention, a device for such coating of workpieces is also provided.
Devices and methods of the aforementioned type are widely used for the coating of workpieces and for bonding workpieces to a coating. In particular, laser radiation is used for activation, as is described in EP 1 163 864 B1, for example. With laser radiation, a sufficiently high energy input into the bonding region can take place, by which the bonding region is activated.
However, apart from high costs, the use of a laser entails a complex construction and a comparatively high space requirement for the laser components.
In view of this background, it is the object of the present invention to facilitate a method and a device for coating a workpiece of the aforementioned type with a simple construction and a low space requirement.
According to the invention, this object is solved by the method of applying a coating according to claim 1 and the device for coating workpieces according to claim 6. Particularly preferred further developments of the invention are given in the dependent claims.
Accordingly, a method of applying a coating, which preferably consists at least partly of plastic, onto workpieces, which preferably consist at least partly of wood, derived wood products, plastic or the like, is provided, with the coating being activated, in particular melted, with the method at least in one bonding region, and the coating being bonded to the workpiece by the bonding region, with the bonding region being irradiated with incoherent radiation, in particular infrared radiation, which is preferably emitted by a light-emitting diode arrangement, for activation, in particular melting.
Moreover, it is provided according to the invention that the device for coating workpieces, which preferably consist at least partly of wood, derived wood products, plastic or the like, with at least one coating, which preferably consists at least partly of plastic, by bonding the coating and the workpiece in a bonding region comprises a support and an activation device, with the support serving to support at least one workpiece and the activation device comprising a light-emitting diode arrangement for irradiating the bonding region for activating, in particular melting, the coating in the bonding region, with the light-emitting diode arrangement serving to emit radiation, in particular infrared radiation, and being arranged such that the bonding region is irradiated with the radiation.
By using incoherent radiation such as radiation emitted by a light-emitting diode arrangement, the bonding region can be activated with simple and space-saving constructive means, a high energy input by monochromatic radiation being possible in particular due to the use of the light-emitting diode arrangement.
The invention is based on the idea to implement the coating of a workpiece using reduced constructive effort and space requirements without having to accept restrictions with regard to the quality of the bonding between the coating and the workpiece. In particular, coherent radiation generated by a laser is not necessary. In this way, numerous complex components of a laser device requiring installation space are not necessary, such as, for example, beam guidance means, beam deflection means, beam focusing means, etc.
The bonding region is to be understood in general as the region in which the bonding between the coating and the workpiece takes place. In particular, the bonding region is to be understood also as the region to be bonded when bonding between the bonding region and the workpiece has not yet taken place. In particular, the bonding takes place in the region in which the activation takes place and sufficient mechanical bonding, for example by pressing, subsequently takes place between the coating and the workpiece.
The activation is to be understood as energy supply by electromagnetic radiation and in particular in that the coating in the bonding region is chemically changed by electromagnetic radiation. In particular, the activation leads to the melting of the coating in the bonding region and to a liquefaction of the coating at least in sections.
The coating is to be understood as a layer which is to be applied onto the workpiece at least in sections. The coating itself can consist of plural materials, sections and/or layers such that, for example, only a part of an adhesive layer or a layer that can be made adhesive, which is part of the coating, is activated. Preferably, the coating comprises an integral or discrete adhesive layer which develops adhesive properties due to activation and energy supply.
Preferably, monochromatic, electromagnetic radiation in a wavelength range of 0.78 to 1000 μm is essentially used, which corresponds to the infrared part of the electromagnetic spectrum.
Particularly advantageous further developments of the invention are given in the dependent claims which will be discussed below. In particular, the features of the dependent claims dependent on the method claim also pertain to the claimed device. Likewise, the claimed method is characterized by the claims dependent on the device claim.
In particular, the activation device, i.e. the device, is free of a resonator and/or an optical amplifier. This reduces the size of the radiation source and enables an arrangement thereof also in the vicinity of the bonding region. The light-emitting diode arrangement serves to emit incoherent radiation and is arranged such that the bonding region is irradiated with the incoherent radiation. This is to be understood in contrast to a device in which the radiation is generated by a laser which comprises a resonator and an optical amplifier and emits coherent radiation.
Preferably, the coating is directly irradiated such that the beam path between the radiation source, in particular the light-emitting diode arrangement, and the bonding region is free during activation, in particular free of beam-shaping elements, furthermore in particular free of a lens. Likewise, in the device, the beam path between the light-emitting diode arrangement and the bonding region is free during activation, in particular free of beam-shaping elements, furthermore in particular free of a lens. Owing to this direct irradiation of the bonding region, further elements, for example beam-shaping elements, do not have to be procured and adjusted, which additionally simplifies the construction and makes it more compact and cost-efficient.
A further preference is that the radiation can be emitted by a light-emitting diode arrangement comprising at least one array and preferably plural arrays, each of which preferably comprises plural light-emitting diode chips. Accordingly, the device preferably comprises a light-emitting diode arrangement in which at least one array and preferably plural arrays are provided, each of which preferably comprises plural light-emitting diode chips.
Since plural light-emitting diode chips are compiled into one array, the radiated power of the light-emitting diode arrangement can be increased, by which the energy input into the bonding region can be increased. Moreover, radiation can be applied extensively to the bonding region.
According to the method, the arrays and/or chips can be switched on and off in accordance with the area of the bonding region. Likewise, the arrays and/or chips of the device can be switched on and off in accordance with the area of the bonding region. This means that the arrays and/or chips can be controlled separately and a selection can be made, for example by an operator, as to which array and/or which chip is to be switched on and off. For example, if a large-surface bonding region is to be activated, many or all arrays and/or chips are switched on. However, if only a relatively small bonding region is to be activated, it is sufficient to switch on only a small part of the arrays, possibly only one array. By individually switching on and off arrays and chips, the respective desired area of the bonding region can be activated.
It is preferred that the radiation source of the incoherent radiation, in particular the light-emitting diode arrangement, is arranged at a distance of 2 to 20 mm, preferably 5 to 15 mm, from the bonding region during activation of the bonding region and/or between the workpiece and the bonding region. Likewise, in the device, the light-emitting diode arrangement, in particular the array(s), and the bonding region are spaced apart during activation preferably by 2 to 20 mm, further preferably 5 to 15 mm, and/or the light-emitting diode arrangement, in particular the array(s), is preferably arranged between the workpiece and the bonding region during activation. This means that the light-emitting diode arrangement is provided directly at the joint gap. For example, additional light guides for guiding coherent light generated in a remotely arranged laser are not necessary. Once again, this leads to a simple, compact and cost-efficient construction.
If the radiation source of the incoherent radiation such as the light-emitting diode arrangement is arranged between the workpiece and the bonding region for activation or the distance between the radiation source of the incoherent radiation such as the light-emitting diode arrangement and the bonding region is between 2 and 20 mm or 5 to 15 mm during activation, the energy input can take place with sufficient intensity, and it can be ensured at the same time that there is a distance between the individual components, which is sufficient for operability. Moreover, a space-saving implementation of the coating and a space-saving device for coating the workpieces is possible.
A further preference is that the entire radiating area at the light-emitting diode arrangement, in particular the radiating area of the entirety of the arrays, is at least 3000 mm2, preferably at least 4000 mm2. The entire radiating area is to be understood as the area which leads to a radiation contribution, i.e. the area by which the radiation can be emitted. If the radiating area is at least 3000, preferably at least 4000, further preferably at least 5000 mm2, an area to be activated or a large-surface bonding region can be activated and bonded. The coating can be applied in an accelerated manner thereby.
A further preference is that the radiated power of a light-emitting diode chip is at least 100 W and/or the radiated power of an array is at least 2 kW, preferably 2.5 kW. With such light-emitting diodes, a sufficiently large energy input onto the coating can take place.
The method can be carried out by a device in which the support is configured as a continuous conveying device such that with the method the workpieces are transported in a conveying direction. Alternatively, the method can also be carried out by a device designated as a so-called stationary machine, in which the workpieces are stationary and the activation device is moved. Combinations of these two concepts are also conceivable.
Further features and advantages of the invention will become more evident by means of the detailed description below.
A preferred embodiment of the present invention will be described in detail below with reference to the enclosed drawings.
In the device, i.e. the coating device 1, for coating workpieces 2, bonding a coating 12 configured as strip material and the workpiece 2 takes place in a bonding region 25, as is shown in a side view in
In the continuous process shown, a support, i.e. a conveying device 4, serves to support and convey the workpiece(s) 2. In the embodiment shown, conveyance takes place from the left to the right, as is indicated in
The coating 12 consists of a general layer and an adhesive layer or a layer of a material 14 that can be made adhesive, which is activated by the incoherent radiation in the bonding region 25. In the embodiment shown, the coating 14 or a part thereof is melted.
The coating 12 is provided as strip material in the form of a roll in the feeding device 10. The coating is guided out of the feeding device 10 and subsequently brought between the upper surface 2a of the workpiece 2 and the pressing device 20 pressing thereon. The pressing device 20 is a pressure roller which rolls over the surface 2a of the workpiece 2 and in this way presses the coating 12 onto the surface 2a of the workpiece 2.
Between the feeding device 10 and the pressing device 20, the activation device such as the light-emitting diode arrangement 30 is provided which is arranged such that electromagnetic radiation, in particular infrared radiation, impinges onto a region, i.e. the bonding region 25, of the coating. The coating 12 or rather the adhesive agent 14 is activated in this region.
The activation device such as the light-emitting diode arrangement 30 is provided upstream of the pressing device. Moreover, the light-emitting diode arrangement does not comprise a resonator or optical amplifier. Consequently, the light-emitting diode arrangement emits incoherent radiation onto the bonding region.
It is evident from
The distance A between the light-emitting diode arrangement 30 and the bonding region 25 can be indicated as the shortest length of the beam path S, as is shown in
| Number | Date | Country | Kind |
|---|---|---|---|
| 102013222636.5 | Nov 2013 | DE | national |
| Filing Document | Filing Date | Country | Kind |
|---|---|---|---|
| PCT/EP2014/073923 | 11/6/2014 | WO | 00 |
