Fluent material handling – with receiver or receiver coacting mea – Processes – Filling dispensers
Reexamination Certificate
2001-04-26
2002-06-11
Maust, Timothy L. (Department: 3751)
Fluent material handling, with receiver or receiver coacting mea
Processes
Filling dispensers
C141S018000, C141S129000, C141S153000, C141S168000, C239S003000, C239S690000
Reexamination Certificate
active
06401768
ABSTRACT:
BACKGROUND OF THE INVENTION
Field of the Invention
The invention relates to a method and a configuration for transporting electrically conductive paint.
Painting methods are used in an extremely wide range of configurations when many identical work pieces, for example car bodies in automobile manufacturing, have to be painted. The painting methods are automated to the greatest possible extent, in order to achieve the highest possible throughput of workpieces. Conventional conveying speeds in automobile manufacturing on a production line are 2.5 m/s to 10 m/s. To this end, it is necessary to carry out a color change within 10 to 15 seconds in these painting methods.
In order to be able to meet such time constraints for a color change, the different colors are normally pumped around from a paint tank in a ring line in each case. From these ring lines, branch lines lead to a battery of valves frequently equipped as a color-change block, which then selects the chosen color and feeds the paint to a line which is connected to the paint application device. In order to shorten the times for a color change further, the battery of valves and the line to the paint application device are provided in duplicate and installed in such a way that they can be operated in parallel. The color-change block is provided as close as possible to the paint application device, in order to configure the branch lines in which the color may also sit for a relatively long time, that is to say, cannot be pumped around, to be as short as possible.
Paint tanks and paint application device are normally provided physically far from one another. Accordingly, the ring lines between the paint tank and the paint application device are often very long.
In such methods, the number of colors is restricted to normally 25 colors, since for each color a circulation line is installed and the installation outlay for further colors, which are then often also used less frequently, is no longer justified economically.
A further aspect is that during the color change there are paint losses, in particular as a result of the cleaning of the paint line between the color-change block and the paint application device, which is done before the next paint of a different color is led into the paint line. In order to minimize such paint losses, in recent times so-called scrapers or “pigs” have been used. These force the greatest possible volume of paint in the paint line back into the associated branch line for the relevant color, before the cleaning of the paint line is carried out.
The workpieces to be painted are often transported to a painting area by a conveying device and, after the painting operation, are transported out of this area again. The painting operation can also be carried out during the transport within a specific area, so that the workpieces to be painted are moved continuously.
Consequently, the painting areas are configured in different ways and provided with different paint application devices. For example, the painting area can be configured as a stationary painting cubicle. An example of a paint application device is a paint atomizer. In addition, stationary painting robots with a paint atomizer moved by the robot are also used as a paint application device. In addition, painting robots which travel along in the painting area are also used as a paint application device.
Depending on the requirement, the paint or lacquer has to be applied in layers in a number of steps, and to some extent, the different paints are also applied one above another, for example firstly a primer, then a colored paint or lacquer and finally a clear lacquer as a topcoat. The layers are then normally applied by the appropriate paint application devices in successive painting areas and baked on in drying ovens.
In addition, the painting technique used differs significantly, depending on the given boundary conditions. Initially, predominantly paints based on solvents were used. Since these paints have only a low electrical conductivity, high-voltage methods with a so-called direct charging are often used without problems here. The paint application device, including the paint in the painting area, is in this case placed under a high voltage of up to 50 kV, so that the atomized paint particles carry an electrical charge. The workpiece to be painted is connected to ground potential. The paint particles are therefore attracted by the workpiece to be painted, as a result of the electrical attraction force, and in this way the utilization of paint is considerably increased.
In the case of painting with modern, environmentally friendly water-based paints, direct charging with high voltage is not possible, since the water-based paints are electrically conductive, and the high voltage would be dissipated via the paint. However, in order to increase the utilization of paint through the use of direct high-voltage charging here too, the supply of paint has to be isolated electrically from the paint application device. If this is not possible, the charging of the paint particles can also be achieved to some extent through the use of so-called external charging electrodes. Only in flight are the paint particles charged up in the electrical field between the electrodes and the workpiece. The insulating effect of the air prevents a high-voltage discharge taking place via the water-based paint.
SUMMARY OF THE INVENTION
It is accordingly an object of the invention to provide a method and a configuration for transporting electrically conductive paint which overcome the above-mentioned disadvantages of the heretofore-known methods and configurations of this general type and through the use of which the supply of electrically conductive paint to the paint application device is improved under the required high-voltage isolation conditions, without reducing the quality of the paint or reducing the variety of colors.
With the foregoing and other objects in view there is provided, in accordance with the invention, a method of transporting electrically conductive paint, the method includes the steps of:
filling a required quantity of an electrically conductive paint into a cartridge at a location at ground potential, the location at ground potential serving as a loading station;
transporting the cartridge filled with the electrically conductive paint with a first conveying device to a second conveying device;
transporting the cartridge filled with the electrically conductive paint with the second conveying device to at least one paint application device at a high potential;
connecting, at the paint application device, the cartridge to at least one spray head provided at the at least one paint application device;
transporting an at least partly emptied cartridge with the second conveying device to a third conveying device;
transporting the at least partly emptied cartridge with the third conveying device back to the loading station;
filling a further cartridge at the location at ground potential; and
conveying the further cartridge with the first conveying device.
An advantageous mode of the invention includes the steps of filling the further cartridge at the location at ground potential while simultaneously transporting the at least partly emptied cartridge back to the location at ground potential.
Another mode of the invention includes the steps of removing the cartridge filled with the electrically conductive paint from the second conveying device by using a moving device, moving the cartridge filled with the electrically conductive paint to the paint application device, and moving the at least partly emptied cartridge from the at least one paint application device onto the second conveying device by using the moving device or a further moving device.
An advantageous mode of the invention includes the steps of transferring a filled cartridge for each of a plurality of workpieces and for each of the at least one paint application device to a first position in the second conveying device, and transferring an at least partly emptied cartridge to a second position i
Börner Thomas
Lichte Joachim
ABB Patent GmbH
Greenberg Laurence A.
Maust Timothy L.
Mayback Gregory L.
Stemer Werner H.
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