DE29923824U1 - Infrared radiation - Google Patents

Description

Meissner, BtokiE &·

Law firm GbR . PO Box 860624 81633 Munich

Advanced Photonics January 18, 2001

Technologies AG M/IND-022-DE/G

Bruckmühler Str. 27 MB/BO/HZ/hk 83052 Bruckmühl-Heufeld

Infrared irradiation

Description

The invention relates to a system for irradiating objects with infrared radiation, in particular for drying and/or fixing surface layers.

For example, when painting the surfaces of objects in series, it is known to transport the objects through a painting chamber. In the painting chamber there is a mist of paint droplets that settle on the surfaces of the objects. The objects are then transported to a drying chamber where the paint layer is dried.

Particularly for objects with irregularly shaped, complicated surfaces, it is also known to use industrial robots that are freely programmable and spray largely evenly thick layers of paint onto the areas of the surface to be painted. With the help of industrial robots, even hard-to-reach areas of the surface can be reached, such as in the area of recesses, cavities, joints and the like. It is also possible to paint only parts of the surface by using industrial robots.

In automobile manufacturing, industrial robots are used in a similar way to seal cavities, for example in the wheel arches of a car body.

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Pasty or liquid sealing material is applied to the cavity surface, for example via a spray gun carried by the industrial robot.

The drying or fixing of the above-mentioned materials, which are applied with the help of industrial robots, usually takes place in continuous furnaces. The objects pass through the continuous furnace in a predetermined throughput time, which is calculated in such a way that the desired drying or fixing of the applied materials is achieved. The throughput times are typically several minutes.

Drying or fixing in continuous flow chambers in which large-area infrared radiators are arranged, for example on the chamber walls, is also known. These infrared radiators are typically operated at surface temperatures of less than 1000 K.

In continuous furnaces or radiation chambers, large surface areas of the objects or even the entire object are inevitably heated. Material that has been placed in hard-to-reach and/or hidden places on the surface can therefore usually only be dried or fixed by heating the object at least in the area of these places. Drying or fixing therefore takes place through heat conduction. The heat transported in this process must have previously penetrated the object via the surface. Furthermore, it is not possible to start drying or fixing the applied materials while other parts of the object's surface are still being applied.

The object of the present invention is to provide a system for irradiating objects with infrared radiation, which provides a fast-acting infrared radiation itself

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in hard-to-reach places and allows targeted irradiation of individual surface areas of the irradiated objects. A further object of the present invention is to provide a means suitable for the system for irradiating the irradiated objects with infrared radiation.

These objects are achieved by a system having the features of claim 1. Further developments are the subject of the dependent claims.

According to a core idea of the invention, an infrared radiation source is moved by means of a robot into one or more working positions in which the respective object to be irradiated is irradiated. The term robot refers to industrial robots and similar movable devices that are able to bring the radiation source into the desired working position or positions. The robot is expediently freely programmable so that any position within its working area can be approached and preferably the radiation source can be freely aligned in each of the positions.

A halogen lamp is preferred as the radiation source, which can in particular have an annular, radiation-permeable tube and a filament extending in the tube. Alternatively or additionally, the halogen lamp can have at least one radiation-permeable tube running in a straight direction with a filament extending in the tube.

Preferably, the radiation source is combined with a reflector for reflecting infrared radiation from the radiation source in the direction of one or more irradiation objects. The reflector is combined with the radiation source

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can be moved by the robot. In a special embodiment, the reflector can be moved independently of the movement of the radiation source, in particular it can be opened up, so that it can be aligned in a working position for concentrated irradiation of the object(s) to be irradiated. The alignment movement, which is independent of the movement of the radiation source, can begin or take place while the radiation source is being moved by the robot. In this way, the combination of radiation source and reflector can be brought into working positions that are difficult to access, for example into hollow spaces.

The robot expediently has a holder for holding the radiation source, the holder being connected to a support device for stationary support of the robot via a pivotable and/or linearly movable robotronic mechanism. In a manner known per se, the robotronic mechanism can be pivoted in particular along multiple axes, for example six axes. By combining it with a suitable robot control, the above-described, freely definable and arbitrary positioning and alignment of the radiation source can be approached or set.

In a further development of the method according to the invention, the radiation source is moved continuously in a range of working positions in such a way that the infrared radiation covers one or more surface areas of the object being irradiated. The radiation source "scans" the surface of the object being irradiated, so to speak. In this way, even surfaces with the most complicated geometries can be irradiated with a uniform energy input per surface unit. It is also possible, for example, when coating car bodies, to use the radiation source in a surface area or in the area of joints, cavities or similar receiving spaces.

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Radiation can be started while material is still being applied elsewhere. In particular, it is therefore not necessary to treat the entire surface or the entire object to be irradiated or at least large parts of it if irradiation or treatment is only necessary in smaller areas. The invention can therefore shorten production times and, under certain circumstances, make it possible to save on continuous furnaces, irradiation chambers and similar large-scale facilities.

The invention also makes it possible to treat surface areas that are difficult to access. For example, the application of thin liquid materials in recesses or cavities in the object to be irradiated requires rapid drying or solidification of the applied material. It is therefore not possible to wait until the object to be irradiated has been transported to a distant continuous furnace or irradiation chamber. According to a preferred development of the method according to the invention, it is therefore proposed to select at least one working position so that the infrared radiation is irradiated into a recess or cavity in the object to be irradiated.

Irradiation with infrared radiation in the sense of the invention can be used in a wide variety of applications. In addition to the drying and/or fixing of surface layers already mentioned, examples include the hardening of fillers in joints or similar receiving spaces, quality control by irradiation with infrared radiation and the heating of the irradiated object in preparation for subsequent process steps, such as the laminating of materials or objects. The invention is also fundamentally applicable to the irradiation of irradiated objects with electromagnetic radiation in other wavelengths.

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gene ranges, e.g. in the ultraviolet range or in the visible range.

The invention can be used particularly expediently if, before the irradiation of the object to be irradiated, the application of a material is started, which is arranged on the surface and/or in joints, cavities or similar receiving spaces of the object to be irradiated and which is dried and/or fixed by the irradiation. The application can then also advantageously be carried out by means of a robot that moves an application device into one or more working positions. In a further development, the movement sequence of the robot for application and the robot for irradiation at least partially coincide and/or the respective movements at least partially follow congruent movement paths. The robot for applying the material can be the same robot as that used to irradiate the object to be irradiated or a different robot. In any case, this design has the advantage that the control of the robot or robots can take place in the same or a similar way. For example, a computer program for controlling the robot or robots can run in the same or a similar way.

The use of infrared radiation in the near infrared, i.e. in the wavelength range between the visible range and 1.5 micrometers, is particularly preferred. Accordingly, a radiation source with a thermal radiator is used in particular, which is designed for the emission of electromagnetic radiation at surface temperatures of more than 2000 K, in particular more than 2500 K. Operation at such high surface temperatures has the advantage that, according to Planck's radiation law, the radiance of the emitted radiation is approximately the fourth

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Power of the absolute surface temperature (assuming that the emissivity is approximately independent of temperature). At the high temperatures proposed, the energy input required for irradiation can therefore be achieved on the object to be irradiated in a short time. The use of radiation sources with thermal radiators that can be operated at surface temperatures of more than 3000 K is therefore particularly preferred. In this case, the energetic maximum of the emitted radiation is at wavelengths of less than 1 micrometer. A further advantage of the short irradiation times that can be achieved with a correspondingly high radiation flux density is the low heating of the irradiated object. The surfaces of the irradiated objects or the layers arranged on the surface can be heated in a short time, but there is no time for the irradiated object to be heated through by heat conduction. By adjusting the irradiated radiation spectrum to the absorption properties of the surface of the irradiated object or the surface layers located there, the heating can even be specifically limited to a certain depth. If, for example, the absorption level of a surface layer is significantly lower than 1, but due to the thickness of the surface layer almost all of the radiation energy is already absorbed in the surface layer, the surface layer is heated through, but the layer or layers underneath are not significantly heated.

Embodiments of the present invention will now be explained in more detail with reference to the accompanying drawings. However, the invention is not limited to these embodiments. The individual figures of the drawing show:

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Fig. 1 a system for irradiating objects with infrared radiation and

Fig. 2 Swivel axes of a six-axis robot, similar to the robot shown in Fig. 1.

The schematic representation of Fig. 1 shows a robot 1 carrying a halogen radiator 10. In the representation of Fig. 1, the robot 1 or the halogen radiator 10 is in a standby position. From the standby position, the robot 1 can move the halogen radiator 10 into various working positions and align the halogen radiator 10 so that pre-programmed surface areas of an irradiation object (not shown) are irradiated with a defined radiation flux density and in a defined irradiation period. The movement sequence of the robot 1 required for this and the temporal control of the electrical current required for the desired infrared radiation are controlled by a control unit 15. The control unit 15 is connected to a base frame 7 of the robot 1 via control lines 16. From there, the individual control lines are led to their respective connection point.

The robot 1 can be pivoted on six axes, as shown in Fig. 2. A carousel 5 of the robot 1 can be pivoted relative to the base frame 7 about the pivot axis I, which runs in the vertical direction. In turn, a swing arm 3 of the robot 1 can be pivoted relative to the carousel 5 about the pivot axis II, which runs in the horizontal direction. At the upper end of the swing arm 3 is the pivot axis III, about which an arm 4 of the robot 1 can be pivoted relative to the swing arm 3. The pivot axis III runs parallel to the pivot axis II. The device holder 6 is located at the front end of the arm 4. However, the arm 4 is not in itself

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immobile, but offers three further possibilities for pivoting movements. Firstly, the entire front part of the arm 4 can be pivoted about the longitudinal axis of the arm 4, i.e. about the pivot axis IV, relative to the rear part, which is pivotally connected to the swing arm 3. In the front part of the arm 4 there is a central hand 2 which can be pivoted about the pivot axis V running transversely to the longitudinal axis of the arm 4. Furthermore, the device holder 6 can be pivoted about the pivot axis VI, with the pivot axis VI running perpendicular to the pivot axis V. The pivot axes IV and v&idigr; are identical in the illustration shown in Fig. 2. However, if the central hand 2 is pivoted about the pivot axis V relative to the position shown, the relative position of the two pivot axes IV and VI to one another changes in such a way that the two pivot axes lie in a common, vertical plane.

As shown in Fig. 1, the halogen radiator 10 is attached to the device holder 6 so that the halogen radiator 10 can be moved in accordance with the movement options described above. The halogen radiator 10 has two quartz glass tubes 11 running in a straight direction and arranged parallel to one another, in which a tungsten filament 12 runs along the longitudinal axes of the quartz glass tubes 11 in an airtight manner in a halogen atmosphere. Since the tungsten filaments 12 are extremely thin and therefore have only a slightly small thermal mass, when the electric glow current is switched on, the desired temperature corresponding to the electric current is reached by the tungsten filaments 12 within a few fractions of a second. The surface temperature of the tungsten filaments 12 is preferably around 3100 K.

The two quartz glass tubes 11 are held at their ends by a holder (not shown) on the carrier body 14.

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tert. The carrier body 14 has a hollowed-out shape which is designed according to the shape and position of the two quartz glass tubes 11 and serves a reflector 13 for reflecting the infrared radiation emitted by the tungsten filaments 12 in the rear direction. The carrier body 14 is shown cut open from the side in Fig. 1. The reflective surface of the reflector 13 consists of polished aluminum and runs approximately along a double parabola in the illustration in Fig. 1.

The system shown in Fig. 1 is used, for example, in the manufacture of automobile bodies for drying pasty or liquid materials which have been applied to hidden places on the body, such as in wheel arches or similar cavities on the surface of the body. In order to achieve short production times, drying by means of the robot 1 and the halogen lamps 10 begins immediately after the liquid or pasty materials have been applied, while these materials are still being applied elsewhere on the body. The liquid or pasty materials are also applied using a robot of the same design as the robot 1. This robot, not shown, moves a spray nozzle into the working position from which the liquid or pasty material is sprayed onto the body. The spray nozzle and the halogen lamp 10 are designed and operated in such a way that the distance of the device holder 6 or the device holder of the other robot from the surface to be dried is the same during spraying and drying. Therefore, the two robots can carry out the same movements to bring the spray nozzle or the halogen lamp 10 into the working position. After spraying, the body is simply transported a little further so that the surface area of the body to be dried is in an accessible position for the robot 1. The effort required to control two robots

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bots is therefore not significantly greater than the effort required to control a robot. In particular, the movement sequence programmed in the control unit 15 can be carried out twice in succession in an almost identical manner with a time delay.

List of reference symbols

1 robot -

2 ' Central hand

3 Swingarm

4 arms

5 ' Carousel

6 device holders

7 Base frame

10 halogen spotlights

11 Quartz glass tube

12 Tungsten filament 13 ' Reflector

14 carrier bodies

15 Control unit

16 control lines

I-VI first to sixth swivel axis

Claims (9)

1. System for irradiating objects with infrared radiation, in particular for drying and/or fixing surface layers, with - a radiation source ( 10 ) for generating the infrared radiation and - a robot ( 1 ) for moving the radiation source ( 10 ) into one or more working positions in which the respective irradiation object is irradiated. 2. System according to claim 1, wherein the radiation source ( 10 ) comprises a thermal radiator ( 12 ) which is designed for the emission of electromagnetic radiation at surface temperatures of more than 2000 K, in particular of more than 2500 K. 3. System according to claim 1 or 2, wherein the robot ( 1 ) has a holder ( 6 ) for holding the radiation source ( 10 ), wherein the holder ( 6 ) is connected via a pivotable and/or linearly movable robotronic mechanism ( 2 . . . 6 ) to a support device ( 7 ) for stationary support of the robot ( 1 ). 4. System according to claim 3, wherein the robotronic mechanism ( 2 . . . 6 ) is pivotable in multiple axes, in particular six axes. 5. System according to one of claims 1 to 4, wherein the radiation source ( 10 ) is combined with a reflector ( 13 ) for reflecting infrared radiation from the radiation source ( 10 ) in the direction of one or more irradiation objects and wherein the reflector ( 13 ) can be moved together with the radiation source ( 10 ) by the robot ( 1 ). 6. System according to claim 5, wherein the reflector is movable, in particular foldable, independently of a movement of the radiation source such that it can be aligned in a working position for concentrated irradiation of the object(s) to be irradiated. 7. System according to one of claims 1 to 6, characterized by a halogen lamp, wherein the halogen lamp ( 10 ) can be moved by means of a robot ( 1 ) into one or more working positions in which the respective irradiation object is irradiated. 8. The system of claim 7, wherein the halogen lamp comprises an annular radiation-transmissive tube and a filament extending within the tube. 9. System according to claim 7 or 8, wherein the halogen lamp ( 10 ) has at least one radiation-transmissive tube ( 11 ) extending in a straight direction with a filament ( 12 ) extending in the tube.