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Method and apparatus for spray coating a workpiece
| Details |
Inventors: Kahmann, Ralf; Klein, Udo; Ott, Winfried; Weiss, Volker;
Assignee: LacTec GmbH Gesellschaft fuer Moderne Lackiertechnik (Rodgau, DE)
Primary Examiner: Beck; Shrive
Assistant Examiner: Calcagni; Jennifer
Attorney, Agent or Firm: Fasse; W. F., Fasse; W. G.
An apparatus and method for painting a workpiece while switching paint colors between successive painting cycles includes a paint supply switching device, a paint feed line connected to the paint supply switching device, a separating element adapted to move back and forth in at least a portion of the paint feed line, first and second receiver stations adapted to receive the separating element at the end positions of its travel in the paint feed line, and a paint spray nozzle at a terminal end of the paint feed line. The separating element is actively held in the first receiver station while paint of a first color is supplied through the paint feed line and sprayed from the nozzle onto a workpiece. To switch to a paint of a second color, the supply of the first paint is terminated, the separating element is released from the first receiver station, and a pushing medium pushes the separating element through the paint feed line, while residual paint is pushed from the paint feed line out through the spray nozzle. The separating element forms a sealing barrier between the pushing medium and the residual paint. Sensors detect the arrival of the separating element in the second receiver station, and the flow of pushing medium is terminated to avoid spraying the pushing medium out through the spray nozzle. Then a pushing medium pushes the separating element back into the first receiver station. |
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DETAILED DESCRIPTION In view of the above, it is an object of the invention to provide a method and an apparatus for carrying out the spray application of paint or other coating materials while changing the color or other characteristics of the coating material in successive paint application cycles, using a pushing medium to push the residual paint out of the paint feed line at the end of a given paint application cycle and reliably separating the pushing medium from the residual paint that is to be used for normal painting spray application.
The invention further aims to avoid or overcome the disadvantages of the prior art, and to achieve additional advantages, as apparent from the present specification.
The above objects have been achieved according to the invention in a method for changing the paint in a paint feed line leading from a paint color switching device to an atomizing spray nozzle, comprising the following steps and features.
Before the end of a given paint application cycle, the method includes a step of stopping the supply flow of a first paint and instead supplying a pushing medium such as pressurized air to push a residual amount of paint through the paint feed line to the spray nozzle.
The method also involves introducing a shuttle element or separating element into the paint feed line between the residual paint and the pushing medium while the residual paint is being pushed through the paint feed line by the pushing medium, and the step of removing the separating element from the paint feed line or otherwise providing for fluid flow past the separating element before the separating element reaches the atomizing spray nozzle.
The separating element is substantially form-stable and provides a good seal between the residual paint and the pushing medium when the separating element is being pushed through the paint feed line.
Thus, it is possible to achieve a highly accurate or exact separation between the still-usable residual paint and the pushing medium.
Throughout this specification, the terms "painting" and "paint" will be used for simplicity and without limitation to refer generally to the application of any type of coating material, such as paint, lacquer, polymeric coatings, clear-coat, varnish, stain, wax, and the like, for example
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Semiconductor manufacture 
