Assembly for the treatment of materials with microwaves
Technical field
The invention relates to an assembly for the treatment of materials with microwaves. Particularly materials can be dried or composite materials can be cured with such an assembly.
Prior Art
Various microwave generators are known. In a monomode applicator, also called monomode furnace, a stationary wave is formed having a wavelength which is set by the operating frequency. The furnace usually consists of a slotted rectangular hollow conductor wherein the width of the slot is set by a given wavelength or frequency. A good homogeneity can be achieved, however, inside the normally very small slot. If the width of the slot is selected larger, the wave exits. This is not desired. Thick or bent materials, therefore, cannot be treated with such a monomode applicator.
In a multimode applicator, also called multimode furnace, several modes are formed and materials with larger diameters may also be treated. It is disadvantageous with such assemblies that the field strength is not evenly distributed in the treatment space whereby thin materials are treated not at all at some positions and excessively treated in some other positions.
Known microwave assemblies either operate in batch mode, where individual pieces are treated or in a continuous mode where the material - either in the form of individual pieces or in the form of continuous material - is consecutively moved through the treatment range.

DE 10 2008 001 637 B4 and DE 200 18 925 U1 disclose examples for microwave assemblies with continuous mode.
Practice examples of microwave applicators are disclosed on the internet site http://www.anton-paar.com/ca-en/products/details/microwave-synthesis/.
Disclosure of the invention
It is an object of the invention to provide an assembly of the above mentioned kind, where thin materials as well as thick materials may be evenly treated.
According to the invention this object is achieved with an assembly with the features of claim 1. The assembly comprises:
(a) a multimode microwave applicator for the treatment of the material with microwaves in a first treatment range;
(b) a multi-component monomode microwave applicator for the treatment of the material with microwaves in a second treatment range; and
(c) means for conveying the material to be treated consecutively through the first and the second treatment range; wherein
(d) a drive is provided for moving two parts of the monomode microwave applicator either by moving them apart from each other or removing them in such a way that the dimensions of the second treatment range perpendicular to the conveying direction are increased.
With the assembly according to the present invention there are two treatment ranges provided. The material is conveyed through both such treatment ranges with each treatment. Depending on the material the monomode applicator, the multimode applicator or both can be switched on. Therefore, all kinds of materials can be treated with one assembly, independent of its diameters. Since the monomode applicator lets only thin materials pass through the narrow treatment range a drive is provided furthermore for moving the two parts of the monomode microwave applicator apart or remove them in such a way that the diameters of the second treatment range are increased

perpendicular to the conveying direction. It is understood, that the drive may be any kind of drive, for example mechanical, hydraulic, pneumatic or electric. Also, the drive can be operated manually or automatically. The movement can be initiated manually or by a control device.
In a preferred embodiment of the invention a switch is provided for switching off the monomode microwave applicator when moving its two portions apart from each other or removing them. The switch ensures that the monomode microwave applicator is switched on only if it is really needed and closed.
The treatment with microwaves is effected mostly inside the material. It may, therefore, be advantageous if additional energy is transferred onto the surface of the material. In a preferred embodiment of the invention, therefore, at least one additional infrared radiation source is provided for irradiating the material with infrared light. The infrared radiation source may be positioned in such a way that the material is irradiated in the first treatment range. It is, however, also possible to arrange the infrared radiation source in the second treatment range or separately before or behind the treatment ranges.
Preferably, the microwaves have a wavelength between 0.1 and 30 GHz, preferably between 1 and 6 GHz and most preferably in the range between 2.44 and 2.46 GHz. The advantage thereof is that the wavelengths in many countries are admitted for such use and a sufficient energy transfer onto the material is ensured. Different free frequencies, in the range around 915 MHz, which may be rather high for homogenous fields, and 5,8 GHz are also available.
In a further modification of the invention it is provided that the means for conveying the material to be treated comprise a conveyor belt. The material is then put on the conveyor belt and conveyed with it through the treatment ranges. It is, however, also possible that the material is conveyed in a different way through the treatment ranges, such as with rollers, driving devices, carriers, robots or the like. With continuous material the material may be clamped and conveyed through the inside of the microwave assembly without any further auxiliary devices. The material may be, if necessary, be moved backwards or "oscillating" forwards and backwards.

Preferably, the conveyor belt is transparent for the generated microwaves. Then, the microwave field is influenced only by a small degree. Particularly well suitable is a conveyor belt, which is a glass fiber reinforced Teflon grid. The conveyor belt may be formed by a grid with a grid spacing between 1 and 10 mm. The grid spacing is preferably selected such, that the material is securely supported.
If the assembly according to the present invention is used for the treatment of prepregs it is advantageous, if a device for the manufacturing of prepregs is provided upstream for feeding prepregs to the assembly. The assembly may be fed with individual pieces or with continuous materials.
In a particularly preferred invention it is provided, that the two-part monomode microwave applicator is adapted to be moved apart in such a way that materials with a maximum thickness of 20 cm, preferably with a maximum thickness of 15 cm and most preferably with a maximum thickness of 10 cm can be conveyed through the second treatment range. The term "thickness" herein designates the diameters perpendicular to the parts of the monomode microwave applicator. It is understood, that the diameters in the other directions may be selected at random, i.e. in particular also larger or smaller than the selected thickness.
Modifications of the invention are subject matter of the subclaims. An embodiment is described below in greater detail with reference to the accompanying drawings.
Brief description of the drawings
Fig.1 is a side view of an assembly for treating materials with microwaves with a
multimode applicator, a monomode applicator and an infrared radiation source.
Fig.2 is a top view of the assembly of Figure 1.
Fig.3 is a front view of the assembly of Figure 1.

Fig.4 shows a detail of Figure 1 with the monomode applicator in the operating
state.
Fig.5 shows a detail of Figure 1 with the monomode applicator in an open state.
Description of the embodiment
In Figures 1 to 3 an assembly for the treatment of materials with microwaves is shown which is generally designated with numeral 10. In the assembly all kinds of materials in the form of batch goods or continuous goods can be treated, such as, for example, prepregs, composite materials, brake linings and the like. Energy is fed to the materials by microwaves which will cause the material to cure, heat up and/or dry.
The figures show by way of example a substrate 12 which is conveyed on a conveyor belt 14 made of a glass fiber reinforced Teflon grid. The conveyor belt is transparent for microwaves. The direction of the conveyance is indicated by an arrow 28. The conveyor belt 14 enters a treatment chamber 16 which is limited by a housing. Microwaves with the frequency of 2.45 GHz are generated by a multimode applicator in the treatment chamber 16 in a first treatment space 20. Microwaves with the frequency of 2.45 GHz are generated by a monomode applicator 24 in a second treatment space 22. Microwave traps 15 and 17 are provided before and behind the multimode applicator 18 which prevent the exiting of the microwaves from the assembly. Microwave traps of the monomode applicator are provided inside its own housing.
A thin substrate 12, as it is shown in the figures, can be moved through both treatment spaces 20 and 22 in the treatment chamber 16 by the conveyor belt. Drivers 19 and 21 are provided for this purpose. If both applicators are switched on the substrate 12 is exposed to the treatment with microwaves two times. If the sample is moved backwards and forwards accordingly more often.
Depending on the selected material the microwaves enter the material deeply. Absorbing material has a temperature gradient when treated with microwaves. The surface emits

heat to the exterior and is slightly cooler than the inside of the material. Furthermore, there are materials which do not absorb microwave radiation, such as polypropylene or glass. Materials which do not absorb nor transmit will reflect the microwaves. Therefore, additionally, several infrared radiation sources 26 are provided for irradiating the surface which are provided in the first treatment range 20 in this embodiment. It is understood, that the infrared radiators may also be positioned at a different position.
Each of the microwave applicators and the infrared radiation sources may be switched on and its power may be controlled independently from each other whereby a plurality of possibilities to treat different kinds of materials are achieved.
Figure 4 shows a section of Figure 1 with the monomode applicator 24. It can be recognized that the slot extending through the material 12 is very narrow in a vertical direction in this embodiment. The assembly, therefore, provides that the upper and lower part of the monomode applicator has a distance 30 to the conveyor belt. The slot may, therefore, be increased to accommodate thick or bent materials also which are preferably treated in the multimode applicator 18. A drive 32 is provided for this purpose. Thereby, materials with higher thickness in a vertical direction may be transported through the assembly also, without the need of alterations or the like.
In an alternative embodiment it is provided that the components of the monomode applicator 24 are completely removed from the treatment range if thick or bent materials with larger diameters in a vertical direction shall be conveyed through the first treatment range 20.
In a further, alternative embodiment it is provided that the parts of the monomode applicator can be set to different distances. The maximum distance corresponds to the passing height in the multimode applicator.
The assembly may be mounted not only in a horizontal direction, but also in a vertical direction. This is reasonable in particular with continuous materials.

Claims
1. Assembly (10) for the treatment of materials (12) with microwaves, comprising:
(a) a multimode microwave applicator (18) for the treatment of the material with microwaves in a first treatment range (20);
(b) a multi-component monomode microwave applicator (24) for the treatment of the material with microwaves in a second treatment range (22); and
(c) means (14) for conveying the material to be treated consecutively through the first and the second treatment range; wherein
(d) a drive (32) is provided for moving two parts of the monomode microwave applicator either by moving them apart from each other or removing them in such a way that the dimensions (30) of the second treatment range perpendicular to the conveying direction (28) are increased.

2. Assembly according to claim 1, characterized by a switch for switching of the monomode microwave applicator when moving its portions apart from each other or removing them.
3. Assembly according to any of the preceding claims, characterized by at least one additional infrared radiation source (26) for irradiating the material with infrared light.
4. Assembly according to claim 3, characterized in that the infrared radiation source is positioned in such a way that the material is irradiated in the first treatment range.
5. Assembly according to any of the preceding claims, characterized in that the microwaves have a wavelength between 0.1 and 30 GHz, preferably between 1 and 6 GHz and most preferably in the range between 2.44 and 2.46 GHz.

6. Assembly according to any of the preceding claims, characterized in that the means for conveying the material to be treated comprise a conveyor belt (14).
7. Assembly according to claim 6, characterized in that the conveyor belt is transparent for the generated microwaves.
8. Assembly according to claim 7, characterized in that the conveyor belt is a glass fiber reinforced Teflon grid.
9. Assembly according to claim 7 or 8, characterized in that the conveyor belt is formed by a grid with a grid spacing between 1 and 10 mm.
10. Assembly according to any of the preceding claims, characterized in that a device for the manufacturing of prepregs is provided upstream for feeding prepregs to the assembly.
11. Assembly according to any of the preceding claims, characterized in that the two-part monomode microwave applicator is adapted to be moved apart in such a way that materials with a maximum thickness of 20 cm, preferably with a maximum thickness of 15 cm and most preferably with a maximum thickness of 10 cm can be conveyed through the second treatment range.