EP1782892A2 - Device and method for treating the surfaces of workpieces - Google Patents

Abstract

The device (1) has a pre-treatment area operating with an aqueous treatment fluid e.g. water, and a dehumidifier device (33) for drying of the aqueous treatment fluid that adheres on a surface of workpieces (3). The dehumidifier device has circular magnetrons (37) for drying of the aqueous treatment fluid, where the workpieces are from plastic or metal. The magnetrons are arranged around a conveyance path (5) of the workpieces. An independent claim is also included for a method of for wet-chemical pre-treatment of a surface of a workpiece that is to be varnished.

Description

The invention relates to a device for surface treatment of workpieces, in particular for wet-chemical pretreatment of subsequently to be painted workpieces, with at least one working with a hydrous treatment liquid pretreatment zone and at least with a drying device for drying adhering to the surfaces of the workpieces aqueous treatment liquid.

Moreover, the invention relates to a method for surface treatment of workpieces, in particular for wet-chemical pretreatment of subsequently to be painted workpieces, in which the surfaces of the workpieces subjected to a treatment with a water-containing treatment liquid and drying on the surfaces of the workpieces adhering treatment liquid is dried.

Known devices and methods of the type mentioned are used, for example, to pretreat workpieces, especially vehicle attachments, in chemical baths or rinses with particular grease removers and / or surfactants for subsequent painting. To ensure good adhesion of the paint, coating defects due to adhering water residues and Blistering is avoided, on the surfaces of the workpieces adhering treatment liquid, especially water in drop form, must be removed. This is done by drying with special drying equipment.

It is known to use this circulating air dryer, such as convection, in which the workpieces are blown and dried in a dryer with mostly very hot air and then the moist warm air is removed from the dryer cubicle. When drying plastics, the drying temperature must not exceed 90 ° C to 100 ° C, otherwise they will become unstable.

Other known drying devices use condensation dryers, which time and energy consuming the surfaces of the workpieces are dried.

In addition, it is known to dry water-based paints on plastic surfaces with microwaves. In order to achieve a high Lakkierqualität, a uniform drying of the full-surface lacquer coating, which forms the surface of the workpiece, is necessary. With microwaves, it is self-regulating and volumetrically dried over the entire lacquer coating. In order to avoid blistering and / or chemical reactions in the paint layer, the self-regulating process must be based on the water content and the optimized adsorption properties of the water-based paint are controlled. The drying of water-based paints, therefore, completely different requirements than the drying of adhesive water on surfaces of the workpieces. The adhesive water adheres to the surfaces of the workpieces in the form of individual, largely incoherent drops. When drying adhesive water therefore a full-surface heating over the entire surface is not desirable. On the contrary, ideally, only the drops should be locally heated and evaporated to achieve rapid drying with high energy efficiency. In addition, the adsorption properties of the workpiece surfaces play no role in the drying of adhesive water. There are therefore completely different, even mutually groundbreaking, requirements for the dryer device, so that known microwave dryers, such as those used for drying water-based paints, have hitherto not been considered for drying adhesive water on surfaces of workpieces.

Object of the present invention is to design a device and a method of the type mentioned above, that in particular individual drops of an aqueous treatment liquid, in particular water, can be dried on the surface of the workpieces technically simple, fast and with high energy efficiency.

This object is achieved in that the dryer device has at least one microwave generator for drying the aqueous treatment liquid.

According to the invention, therefore, microwaves are produced with at least one microwave generator, in particular a magnetron, with which, in particular, drops of water-containing treatment liquid adhering to the surfaces of the workpieces can be directly heated and evaporated. So also scooping sites, such as sinks, and capillary areas, such as holes can be dried in the surfaces of the workpieces without the workpieces themselves are heated unnecessarily. The workpieces can be dried in this way very efficiently, so that a carryover of the treatment liquid is avoided, for example, in a subsequent Lakkierzone and also no reworking of the surfaces to eliminate drops of a treatment liquid is required. Also, almost no heat transfer of the treatment liquid takes place on the material surfaces, since the water evaporates very quickly. The low heating of the workpieces has the great advantage that they are spared, so that the device can be used for sensitive workpieces, for example made of plastic. Since the individual drops of water are locally heated and evaporated with a low volume, a greater energy efficiency and a much faster drying than with the circulating air dryers or condensation dryers known from the prior art are possible in which the air surrounding the workpiece and under certain circumstances even the conveyor technology and the goods carriers are heated. In this way, any subsequent cooling zone requires less cooling power so that energy is also saved here. Depending on the workpiece geometry, even a cooling zone can be dispensed with. Overall, the drying of adhesive water on the surfaces of the workpieces with microwaves leads to a very high compared to conventional dryers efficiency and significantly shorter drying times and thus to a significant reduction in operating costs, especially in terms of gas and electricity consumption. If the drying time in a conventional dryer is about 20 to 25 minutes, it can be reduced to about 3 to 4 minutes in the microwave dryer according to the invention. Incidentally, the microwave generator requires significantly less space than, for example, a hot air blower of a conventional circulating air dryer. Furthermore, the maintenance is significantly lower because the microwave generator has no moving parts and therefore also has a low wear.

The workpieces can be appropriately pretreated in the pretreatment zone of the device, in particular degreased, cleaned and rinsed with aqueous treatment liquid, and then dried, without any displacement of the workpieces from the device out is required. The transport of the workpieces through the zones can be clocked, continuous or reversing. All known types of material transport on goods carriers are possible.

The workpieces can be made of plastic or metal. On workpieces made of certain plastic microwaves have the positive side effect that, for example, their outgassing can be improved in preparation for the subsequent Lakkierung.

In order to be able to uniformly penetrate the surroundings adjacent to the surfaces of the workpieces with microwaves, so that the adhering treatment liquid is exposed to the undamped microwaves, the dryer device can have a multiplicity of microwave generators, in particular magnetrons, arranged in particular around a transport path of the workpieces.

Furthermore, the conveying path in front of the microwave zone can lead through a blowing zone and / or following the microwave zone through a cooling zone. In the blowing zone, the largest part of the treatment liquid can be blown from the surface of the workpieces, so that there are then only a few drops of treatment liquid on it, which can be heated quickly and with low energy expenditure with microwaves in the microwave zone and evaporate. In the subsequent Cooling zone, the workpieces can be cooled so that they can then be fed directly to a painting for painting.

The inventive method is characterized in that the treatment liquid is dried with microwaves. With microwaves, treatment liquid adhering to the surfaces of the workpieces is heated and evaporated rapidly and with great energy efficiency. In this process, also filling areas and capillary areas are dried without the workpieces themselves having to be heated.

The workpieces can be cleaned in this way, rinsed with the treatment liquid, and then dried directly. The treatment liquid, in particular the water, is removed without residue, so that no reworking of the surface is required.

The treatment liquid may be blown away from the surfaces of the workpieces before microwave-drying the adhering treatment liquid still adhering to the surfaces, and / or the workpieces may be cooled after drying the adhering treatment liquid with microwaves. By blowing away a large part of the treatment liquid before drying with microwaves, the drying process is significantly accelerated and also saves energy. Cooling The workpieces following microwave drying have the great advantage that the workpieces can then be directly painted without or without long cooling times.

Figur 1

schematisch eine Draufsicht einer Vorbehandlungsvorrichtung zur nass-chemischen Vorbehandlung von Werkstückoberflächen;

Figur 2

schematisch eine Draufsicht einer Mikrowellenzone der Vorbehandlungsvorrichtung aus Figur 1 im Detail;

Figur 3

schematisch eine isometrische Detaildarstellung der Mikrowellenzone aus Figur 2 im Bereich eines Magnetronrings.

Embodiments of the invention will be explained in more detail with reference to the drawing; show it

FIG. 1

schematically a plan view of a pretreatment apparatus for wet-chemical pretreatment of workpiece surfaces;

FIG. 2

schematically a plan view of a microwave zone of the pretreatment device of Figure 1 in detail;

FIG. 3

schematically an isometric detail of the microwave zone of Figure 2 in the range of a magnetron ring.

FIG. 1 shows a plan view of a pretreatment device provided overall with the reference numeral 1 for wet-chemical pretreatment of surfaces of workpieces 3 made of plastic to be subsequently painted.

The pretreatment device 1 comprises along a transport path indicated by arrows 5, which in FIGS 1, 2 and 3 substantially horizontally from left to right, one behind the other a wet-chemical pre-treatment zone 7, a blowing zone 9, a in Figures 2 and 3 also shown in detail microwave zone 11 and a cooling zone 13. The zones 7, 9, 11 and 13 are each surrounded by a cuboidal cabin 15, 17, 19 and 21, respectively, which can be opened to the respectively adjacent zone 7, 9, 11 and 13, respectively. The cabin 17 of the wet-chemical pretreatment zone 7 is in the feed direction for the workpieces 3, left in Figure 1, and the cabin 21 of the cooling zone 13 in the export direction, right in Figure 1, outwardly open to the environment or accessible via an airlock.

From the left along the transport path 5 leads to the cabins a straight, two parallel guideways exhibiting conveying system 23 visible in Figure 3 supports 25 in the cabin 15 of the wet-chemical pre-treatment zone 7, through this and the cabins 17 and 19 of the subsequent blowing zone and microwave zone 11 and right out of the cab 21 of the cooling zone 13 back out. On the conveyor system 23 are known, rectangular Skids 25 with visible in Figure 3 goods carriers 31 on which the workpieces are 3, along the transport path 5 through all zones 7, 9, 11 and 13 through conveyed. FIG. 3 shows in detail a section of the microwave zone 3, through which the conveyor system 23 runs, on which a skid 25 with two similar to those of FIG vertical fabricated from profiles goods carriers 31 is located on which a cuboid workpiece 3 is mounted.

In the wet-chemical pretreatment zone 7 are not shown in detail chemical baths with grease removers and surfactants in which the workpieces 3 can be cleaned and pretreated. In addition, purging devices, not shown in detail there, are also provided there, with which the workpieces 3 can be rinsed with deionized water after cleaning and pretreatment. Alternatively, any other known type of cleaning such as acidic cleaning, CO ₂ ice et cetera can be used.

The blowing zone 9 has a blower, not shown, with which after the rinsing in the wet-chemical pretreatment zone 7 adhering water on the surfaces of the workpieces 3 can largely be blown away, so that only a few drops of water remain adhering to the surfaces.

The microwave zone 11 comprises a drying device, indicated overall by the reference numeral 33, for drying the water droplets, which are still occasionally adhered to the surfaces of the workpieces 3 after being blown away.

The drying device 33 has, visible in Figures 1 and 2, four successively arranged in the direction of the conveying path 5 magnetron rings 35. Each magnetron ring 35 comprises magnetrons 37 which are directed inwards onto the workpieces 3 and are approximately annularly arranged in a plane perpendicular to the conveying direction 5, as can be seen in FIG. The magnetrons 37 are each mounted in pairs on the two side walls 39 and the top wall 41 of the cabin 19 of the microwave zone 11. They are arranged so that they can emit microwaves to the interior of the cabin 19 of the microwave zone 11, ie to the surfaces of the workpieces 3, out.

The magnetrons 37 are connected via supply lines, not shown, with a control cabinet 43, which is located next to the cabin 19 of the microwave zone 11, in Figure 2 above. In the cabinet 43 not shown supply sources and control means for the magnetron 37 are arranged.

By driving the magnetrons 37 are generated by these microwaves with an optimally suitable for the heating of water wavelength, which are preferably absorbed in the water droplets on the surfaces of the workpieces 3. The water drops are heated by the microwaves and evaporate without residue, so that no adhesive water carryover into the subsequent cooling zone 13 or in the not shown, subsequent process zones takes place.

In particular, the special arrangement of the magnetrons 37 and the choice of the wavelength of the microwaves ensures that the water droplets are locally heated by the microwaves on the surfaces of the workpieces 3, also at scooping points, for example depressions, and in capillary areas, for example in holes become and evaporate. The workpieces 3 themselves, the goods carriers 31 and also the skids 25 are here hardly, that is heated to less than 60 ° C, since the microwaves act substantially selectively on the water. In this way it is achieved that a rapid drying of adhering to the surfaces of the workpieces 3 adhesive water can be done with a very high energy efficiency. In addition, as a side effect of the microwaves, the outgassing of the plastic of the workpieces 3 can be improved.

For cooling the drying device 33, in particular the magnetron 37, with cooling water is also next to the cabin 19 of the microwave zone 11, arranged in Figure 2 next to the cabinet 43, a cooling unit 45 and not shown cooling lines to the dryer 33 and cooling shells not shown magnetrons 37 connected.

For wet-chemical pretreatment of the surfaces of the workpieces 3 to be painted, these are first conveyed intermittently with the skids 25 and the goods carriers 31 via the conveyor system 23 at a distance one behind the other along the conveying path 5 into the wet-chemical pretreatment zone 7. There, the workpieces 3 are treated in the chemical baths with the appropriate chemicals. The workpieces 3 are then rinsed with the deionized water so that the surfaces are free of treating chemicals.

Subsequently, the skids 25 and the goods carrier 31 with the workpieces 3 are cyclically successively transported through the blowing zone 9. There the water on the surfaces is largely blown away. Isolated drops of water remain adhering to the surfaces, especially at scooping or capillary areas.

Then the skids 25 are cyclically successively transported with the workpieces 3 through the microwave zone 11, where the remaining drops of water on the surfaces of the workpieces 3 are now dried without residue within 3 to 4 minutes with microwaves, so that neither a Haftwasserverschleppung takes place, nor the Surfaces must be reworked due to coating problems caused by water droplets.

Finally, the workpieces 3 are cyclically successively transported on the skids 25 through the cooling zone 13 and cooled there. The pretreatment is completed.

The arranged on the skids 25, cooled workpieces 3 can then be fed directly through the conveyor system 23 of the pretreatment device 1 subsequent, not shown, painting for painting.

The workpieces 3 can also be cleaned with the pretreatment device 1 only with water without the use of chemicals.

The pretreatment device 1 and the method are also not limited to the pretreatment of workpieces 3 to be painted. Rather, the workpieces 3 can also be treated differently after the pretreatment, for example also glued or welded.

The pretreatment device 1 and the method can also be used for drying adherent residual water on layers of already completely dry paint, for example, following a cleaning of the paint surface, after grinding processes.

The pretreatment device 1 may also have more than one dryer device 33.

The workpieces 3 can instead of intermittently also continuously or reversibly and also during transport transported in rotation along the conveying path 5.

Instead of the conveyor system 23 with the skids 25, a different type of conveyor technology can also be used.

The zones 7, 9, 11 and 13 need not be rectilinear in a row, they may also be arranged along a curve or offset horizontally or vertically.

Instead of the magnetrons 37, it is also possible to use other microwave generators, in particular microwave tubes, for example klystrons, or even microwave semiconductor components.

Also, less than six microwave generators may be provided in a different arrangement than annular. The annular arrangement of the microwave generators may also be inclined at an angle to the conveying path 5. It is also possible to use more or fewer than four ring arrangements.

The workpieces 3 may instead of plastic also made of another material, for example metal, carbon fiber, Glass, ceramics, a composite material or a material mix.

The transport path 5 for the workpieces 3 can, instead of through a wet-chemical pretreatment zone 7, also lead through a plurality of different pretreatment zones.

It may also be provided only either a blowing zone 9 or a cooling zone 13. It can also be dispensed with both.

Claims (6)

Apparatus for the surface treatment of workpieces, in particular for the wet-chemical pretreatment of subsequently to be painted workpieces, with at least one pretreatment zone operating with a hydrous treatment liquid and at least one dryer apparatus for drying hydrous treatment liquid adhering to the surfaces of the workpieces,
characterized in that
the drying device (33) has at least one microwave generator (37) for drying the aqueous treatment liquid. Device according to one of the preceding claims, characterized in that the workpieces (3) are made of plastic or metal. Device according to one of the preceding claims, characterized in that the drying device (33) has a multiplicity of microwave generators, in particular magnetrons (37), arranged in particular annularly around a conveying path (5) of the workpieces (3). Device according to one of the preceding claims, characterized in that the conveying path (5) leads in front of the microwave zone (11) through a blowing zone (9) and / or following the microwave zone (11) through a cooling zone (13). Process for the surface treatment of workpieces, in particular for wet-chemical pretreatment of subsequently to be painted workpieces, in which the surfaces of the workpieces are subjected to a treatment with a water-containing treatment liquid and dried on the surfaces of the workpieces adhering treatment liquid,
characterized in that
the aqueous treatment liquid is dried with microwaves. Method according to claim 5, characterized in that
that the treatment liquid is blown away from the surfaces of the workpieces (3) before drying on the surfaces still adhering treatment liquid with microwaves and / or the workpieces (3) are cooled after still adhering treatment liquid was dried with microwaves.

Images