METHOD AND DEVICE FOR THERMALLY ACTIVATING A FUNCTIONAL LAYER OF A COATING MATERIAL

Abstract

The present invention relates to a method for thermally activating a functional layer of a coating material, preferably an edge material, wherein the method comprises the following steps: providing the coating material; feeding the coating material to a device for thermally activating a functional layer of the coating material; and thermally activating the functional layer of the coating material, wherein the thermal activation of the functional layer of the coating material occurs by microwaves which are generated by at least one semiconductor wave generator. The present invention also relates to a device for thermally activating a functional layer of a coating material.

Claims

1. A method for thermally activating a functional layer of a coating material (3), wherein the method comprises the following steps: providing the coating material (3); feeding the coating materials (3) into a device (10) for thermally activating a functional layer of the coating material; and thermally activating the functional layer of the coating material (3), wherein the thermal activation of the functional layer of the coating material (3) is performed by electromagnetic waves, in particular microwaves which are produced by at least one semiconductor wave generator (11a, 11b, 11c).

2. The method according to claim 1 also having the following steps: recording at least one process variable (T.sub.i, P.sub.i, N.sub.i) of the method, controlling the semiconductor wave generator (11a, 11b, 11c) using this process variable (T.sub.i, P.sub.i, N.sub.i).

3. The method according to claim 2, wherein the at least one process variable (T.sub.i, P.sub.i, N.sub.i) comprises at least the temperature of the functional layer of the edge strip at a particular point before, during or after thermal activation with the semiconductor wave generator (11a, 11b, 11c) or the power, amplitude or phasing of incoming or reflected microwaves.

4. The method according to claim 2 or 3, wherein the at least one process variable (T.sub.i, P.sub.i, N.sub.i) comprises a plurality of temperatures from the functional layer of the edge strip at particular points before, during or after thermal activation with the semiconductor wave generator (11a, 11b, 11c) to thus allow a specific and defined thermal activation of the functional layer of the coating material (3).

5. The method for applying coating material (3) to an area of a workpiece, in particular to a narrow area, comprising the following steps: thermal activation of a functional layer of the coating material (3) using a method according to one of claims 1 to 4; injection of the coating material (3) onto the narrow area of the workpiece.

6. A device (10) for thermally activating a functional layer of a coating material (3) having: at least one semiconductor wave generator (11a, 11b, 11c), wherein the semiconductor wave generator (11a, 11b, 11c) is able to produce electromagnetic waves, preferably microwaves, which are then able to thermally activate the functional layer of the coating material (3).

7. The device (10) according to claim 6 also having: an applicator (12a, 12b, 12c); a waveguide which is able to forward electromagnetic waves produced in the semiconductor wave generator (11a, 11b, 11c) to the applicator (12a, 12b, 12c), in order to thermally activate the functional layer of the coating material (3) there.

8. The device (10) according to claim 6 or 7 also having: a device for recording measurements (15) and a control device (16), wherein the device for recording measurements (15) is designed to record measurements taken during thermal activation of a functional layer of a coating material (3) and then forward these measurements to the control device (16), and the control device (16) is designed to regulate or control the semiconductor wave generator (11a, 11b, 11c) using the measurements received.

9. The device (10) according to one of claims 6 to 8 also having: an additional semiconductor wave generator (11a, 11b, 11c) and an additional applicator (12a, 12b, 12c), wherein the first semiconductor wave generator (11a, 11b, 11c) and the additional semiconductor wave generator (11a, 11b, 11c) are designed to produce microwaves that are synchronised by means of PLL synchronisation.

10. A device for applying coating material (3) to a narrow area of a workpiece having: a device (10) for thermally activating a functional layer of a coating material (3) according to one of claims 6 to 9, and an injection device for injecting the coating material onto the narrow area of the workpiece.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0041] FIG. 1 shows a preferred embodiment of the coating device according to the invention.

[0042] FIG. 2 is a functional diagram of a preferred embodiment of the coating device according to the invention.

[0043] FIG. 3 shows a graph of an application of energy applied via the frequency of various microwave generators.

[0044] FIG. 4 shows a control loop of a preferred embodiment of the device according to the invention or the corresponding method.

PREFERRED EMBODIMENTS OF THE PRESENT INVENTION

[0045] FIG. 1 shows an embodiment of the present invention. It should be noted that a number of possible features are included in the embodiment shown to allow a comprehensive understanding of the present invention, which features can be omitted or combined in different configurations according to the aforementioned general summary and the enclosed claims.

[0046] FIG. 1 shows a coating material 3 which is transported in a feed device 2 through an applicator 12a of a device for thermally activating a functional layer of a coating material 10 (hereinafter referred to as the device 10). A possible feed device is not shown in this drawing, nor is any other possible injection device for subsequent injection of the coating material. The present description focuses on the device 10 and its interaction with the coating material 3.

[0047] In addition to the applicator 12a mentioned at the beginning of the description, the device 10 also has a semiconductor wave generator 11a, a wave conductor 13a, an interface 14a and a coupler 15a.

[0048] In the semiconductor wave generator 11a, the microwaves are produced with semiconductor technology. The exact production of the waves in terms of energy level and frequency can be defined with a control loop; this is explained in further detail in relation to FIGS. 2 and 3. The microwaves thus produced are forwarded in the waveguide 13a. The waveguide 13a is connected to the coupler 15a by the interface 14a. This interface can be designed so that these two devices can be disconnected from each other if necessary, for maintenance, for example, or to replace faulty components. The coupler 15a in turn is connected to the applicator 12a. The microwaves thus reach the coating material 3 to thermally activate its activation layer.

[0049] It must also be mentioned in this context that the applicator works as a cavity resonator in this preferred embodiment and, on appropriate excitation, a resonance situation within the applicator can be achieved in relation to the behaviour of the electric field strength on the basis of its resonance frequency. The electric field strength within the applicator is thus significantly increased. This has a favourable effect on the application of heat to a coating material with high dielectric losses, which can then be brought to the required temperature more quickly.

[0050] Compared to conventional production of microwaves with magnetrons, the entire device 10 can be made considerably more compact in terms of the space required by using a semiconductor wave generator. This is particularly attributable to the fact that there is no need to provide a separate circulator for the purposes of deflecting reflected microwaves. In fact, a bleeder resistor built into the semiconductor wave generator can be used that will perform the function of a circulator. In addition, the function elements can predominantly be incorporated into the design of the semiconductor generator and therefore also be designed in a considerably more compact configuration.

[0051] FIG. 2 shows a functional diagram of a preferred embodiment of the device. This has been expanded compared to the components from FIG. 1 to include the following components: The device 10 also has an additional semiconductor wave generator 11b, an additional applicator 12b, an additional waveguide 13b, an additional interface (not shown) and an additional coupler (not shown). If, for example, the power of the semiconductor wave generator 11a is not sufficient, this additional semiconductor wave generator 11b can be used. PLL synchronisation is provided between these semiconductor wave generators 11a and 11b which ensures that any phase deviation between the microwaves of the two semiconductor wave generators 11a and 11b is kept to a minimum. This prevents destructive interference, which admittedly would not occur in the embodiment shown here with a plurality of applicators 12a and 12b but would enable the semiconductor wave generators 11a and 11b to be operated with a single applicator. An additional semiconductor wave generator 11c is also indicated, which would allow the generation of additional power. Not shown are a corresponding applicator 12c, a waveguide 13c, an interface 14c and a coupler 15c for applying thermal power to a third position. In an alternative embodiment, not shown, several semiconductor wave generators can apply the electromagnetic waves in a single applicator to a coating material. This may be preferable, as the cost of the additional applicator can be saved with this embodiment.

[0052] Furthermore, the recording and processing of process variables are also shown in this drawing. The process variables N.sub.i from the semiconductor wave generators (hereinafter referred to, in short, as process variables N.sub.i) comprising various process variables N.sub.i to N.sub.3 of the semiconductor wave generator 11a, and so on, are forwarded to a control device 16. Examples of process variables N.sub.i include the frequency of the microwaves produced and their power (in other words, the forward power).

[0053] The same applies to process variables P.sub.i from the applicators (hereinafter referred to, in short, as process variables P.sub.i); these process variables Pi are also forwarded to a control device 16. Examples of process variables P.sub.i include the frequency of the reflected microwaves and their power (in other words the reflected power).

[0054] Other process variables can be measured. For example, the temperature of the continuous coating material is measured at various points; these temperatures are process variables T.sub.i. A device 17 for recording measurements is provided in this embodiment for recording these process variables T.sub.i.

[0055] In summary, these process variables N.sub.i, P.sub.i and T.sub.i are forwarded to a control device 16. This control device 16 has, for example, a PID controller which is able to produce control values Si with these process variables N.sub.i, P.sub.i and T.sub.i that are forwarded to the semiconductor wave generators 11a and 11b. Examples of these control values Si are the frequency and power of the semiconductor wave generators 11a and 11b.

[0056] Due to the adjustable transmission frequency on the semiconductor wave generators 11a and 11b, the adaptation of the resonance condition to the heating medium can, unlike with conventional production of microwaves, be done with a magnetron without additional tuning elements (such as a linear or rotatory tuner). The adaptation can only be achieved by means of targeted control of the transmission frequency of the semiconductor wave generators 11a and 11b. The properties relevant to microwaves of a medium used can therefore also change during operation.

[0057] To this end it is necessary to simply measure a reflected power from the loading of the applicator with coating material and to factor this into the calculation of the control variable. If, for example, the free volume within the applicator is reduced, its resonance frequency is typically actually increased, therefore the target frequency of the microwave from the generator is reduced accordingly, and vice versa.

[0058] To this end, the forward and reflected power, or the forward and reflected microwaves, are measured with suitable measuring devices such as directional couplers and taken into consideration in a control loop for setting the ideal frequency for the microwave. This is explained further in relation to FIG. 4. It is therefore possible to configure the optimum behaviour of the power of the semiconductor wave generators 11a and 11b for the medium to be heated, in other words for the functional layer of the edge strip of the invisible joint.

[0059] The transmission frequency can technically be adjusted with a frequency synthesiser. Resonators are thus easier to implement, as the resonance condition can be adapted to the load by means of the frequency and there is therefore no need for additional tuning elements. This also reduces costs and results in a more compact applicator design. In addition, the amount of installed technology is reduced. Control concepts in which the reflection coefficient is maintained at a minimum or desired value using a suitable algorithm can be achieved more appropriately with a semiconductor wave generator. Superimposed process controls with additional process variables can thus be implemented more easily, as will be shown in relation to FIG. 4.

[0060] FIG. 3 shows a qualitative representation of two exemplary transmission spectrums of a magnetron I and a semiconductor wave generator II as an amount of energy applied via the frequency. Both microwave generators have the same nominal frequency; this can be adjusted variably as described above with a semiconductor wave generator (II, continuous line) and is determined by the design in the case of a microwave generator which is based on magnetron technology (I, broken line). It can be seen that the transmission spectrum I is significantly broader and also has a lower power density at nominal frequency, whereas transmission spectrum II has a very narrow spectrum and a higher power density. Further advantages and comparisons of the various technologies for generating microwaves are described in the introductory section.

[0061] FIG. 4 shows a control loop of a preferred embodiment of the device according to the invention or the corresponding method. This is a twin-circuit control loop, in other words a loop that provides a single control in relation to two parameters.

[0062] Firstly, the temperature process variable T.sub.i is controlled. This can be provided as the main process variable, as the final temperature of a functional layer of a coating material is of crucial importance. A target temperature T.sub.i,target can be specified for each individual temperature measuring point, and this measuring point must be reached as accurately as possible. The actual values for the temperature of an activation process 5, which correspond to the measured status variables, are accordingly incorporated into the control device 16 by means of feedback loop.

[0063] A further process variable is the reflection coefficient r. This is derived from a comparison of the forward power, in other words the power of the semiconductor wave generators and the reflected power, or the reflected power that was not dissipated by the functional layer of the coating material. A change in this variable can be achieved in particular by varying the frequency. These variables can accordingly be linked to each other using a control algorithm, in other words if the reflection coefficient r.sub.actual is not optimal, the frequency can be varied. The reflection coefficient will preferably be maintained at a very low value, for example at no more than 10 to 20 dB or even more preferably at 0.

[0064] The integration of a field bus and controller is easily possible with a controlled system of this kind.