Fluid sprinkling – spraying – and diffusing – Processes – Including electrostatic charging
Patent
1988-09-16
1990-05-01
Lawrence, Evan
Fluid sprinkling, spraying, and diffusing
Processes
Including electrostatic charging
239112, 239690, B05B 502, B05B 508
Patent
active
049211692
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention refers to a method for supplying an electrically conductive, floating medium, e.g. paint, from a storage system via a feed conduit to a consumption station in which is incorporated an electrostatically chargeable distribution device, e.g. a paint spraying gun, for treatment, e.g. painting of treatment units, whereby the medium is supplied to an intermediate storage forming part of the feed conduit between the consumption station and the storage system, and which feed conduit is adapted to be interrupted electrically and physically between the storage system and the intermediate storage by means of an interruption unit. The invention furthermore incorporates a device for performing the method.
BACKGROUND OF THE INVENTION
The use of water based paints in combination with electrostatic charging has brought about that the safety aspects have been focused, as short circuits between the high-voltage electrostatic charging in the paint gun and the grounded paint conduit system may occur.
Different devices are earlier known for preventing such potential differences to arise. All these known methods operate according to the so called "rain-drop principle", which means that the storage container, in which the paint is stored, is separated from the electrostatically charged paint gun, and supplies the paint drop by drop via such a big air-gap that no spark-over can occur. These devices however have the drawback of having a very limited capacity and do not allow a continuous spray painting, particularly if it concerns bigger painting objects, such as e.g. car bodies.
Another problem at conventional painting paints is the difficulty to change paint during the short time required for moving away the treated object and placing a new painting object within the action radius of the paint gun. As the painting ever more is carried out with aid of robots it is preferred that the paint change shall be effected without the need of changing spraying equipment.
SUMMARY OF THE INVENTION
The purpose of the invention is to provide a method and a device wherein the electrostatic charging in the spraying nozzle is not transferred to the storage system of the painting plant. Another purpose is to become independent of the comparatively long time required for the dielectric transfer of the paint, and to be able to make a paint change in a simple and very swift manner. The demand from the car producer can be, e.g. that before painting of each car body it shall be possible to make a paint change. These tasks have been solved in that the medium is pumped from the storage system via a first feed conduit to a first closed valve part forming part of said interruption unit, the second valve part of which, which is connected to a second feed conduit, at interconnection thereof establishes a closed medium connection between the feed conduits, that the medium during the interconnection period of the valve parts is pumped to the intermediate storage, whereby the electrostatic charging is interrupted, and that after disconnection of the valve parts the medium is subjected to pressure in the intermediate storage and during electrostatic charging is supplied to the distribution device.
The device according to the invention is characterized therein that the interruption unit incorporates a first valve part forming part of the feed conduit of the storage system and a second valve part forming part of the feed conduit of the distribution device, that the valve parts are connectable in a fluid-tight manner and electrically, physically releasable from each other by means of an actuator, which creates an air-gap between the spaced apart valve parts, that upstream of the interruption unit in the conduit is provided an intermediate storage, the volume of which at least corresponds to the treatment of a treatment object, and that a control device is provided, which during the interconnecting phase of the valve parts interrupts the electrostatic charging.
BRIEF DESCRIPTION OF THE DRAWINGS
The invention wil
REFERENCES:
patent: 3906122 (1975-09-01), Krause et al.
patent: 3937400 (1976-02-01), Krause
patent: 4771729 (1988-09-01), Planert et al.
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