Fluid sprinkling – spraying – and diffusing – Electrostatic type – With automatic safety feature
Patent
1989-11-30
1991-04-30
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Electrostatic type
With automatic safety feature
B05B 500
Patent
active
050110861
DESCRIPTION:
BRIEF SUMMARY
The invention concerns a spray coating apparatus according to the preamble of claim 1.
In a preferred embodiment, the invention concerns a spray coating apparatus for electrically conductive coating liquids. The atomizer is preferably a rotary atomizer.
A spray coating apparatus according to the preamble of claim 1 is previously known from the German patent application M 15 973 IVa/75c. In this device, the electrode arrangement is located completely outside the ring. Both are connected to high voltage.
Electrically conductive coating liquids are specifically enamels containing water or metal particles for so-called metallic finishes. It is customary to electrostatically charge the coating liquid prior to atomization so that it will be electrically attracted by the object being coated, which is grounded. But this involves difficulties in that the electrical voltage is transmitted back into the feed lines through the electrically conductive coating liquid, whereas the storage container for the coating liquid is on ground potential. Therefore, great efforts have already been made toward interrupting the backward electrical current path given through the coating liquid, between the atomizer and the liquid supply system. Devices of this type are known from the German patent disclosure 34 40 381, German patent document 29 37 890 and the British patent document 1,478,853. Reference is also made to: U.S. Pat. No. 3,393,662; German Patent document 3,609,240 Al; German Patent document 3,716,776 Al; U.S. Pat. No. 4,447,008; U.S. Pat. No. 3,049,092; and U.S. Pat. No. 3,408,985.
The problem underlying the invention is to provide a simpler and nonetheless safe method by which a strong electrical charging of possibly all particles of the coating material is generated while at the same time avoiding a voltage back transmission from the sprayed, electrically conductive coating material to the atomizer and into the coating material supply system.
This problem is inventionally solved through the characterizing features of claim 1.
Inventionally, gas flows out the two gas channels transmit electrical charges from the electrode or the electrodes to the atomized coating material only in the spray cloud area. Customarily, the electrical charge transfer from the gas to the coating material takes place in an area in which the atomized coating material particles already have a distance from each other so large that no direct electrical path from the atomized coating material back to the atomizer can occur. The complicated, expensive devices for interruption of the voltage respectively current path in the material supply system of the prior art for electrically conductive coating materials, which again and again needs to be cleaned, becomes unnecessary. This makes the manufacture and the operation of such spray coating devices considerably more inexpensive. Accomplished at the same time, according to the invention, is a more uniform and stronger electrical charging of all particles of the atomized coating material.
The invention is especially advantageous in connection with rotary atomizers which, as is commonly known, have the form of disks, bells or cups and serve the spraying of liquid coating materials. But the invention is not limited thereto; it can be favorably used also with stationary atomizers which, as is known, are of nozzle design and serve the spraying of liquid or powdered coating materials
Further characteristics of the invention are contained in the sub-claims.
The invention will be described hereafter with reference to the drawing and with the aid of preferred embodiments, as examples.
FIG. 1 shows a side elevation of an inventional spray coating apparatus;
FIG. 2, a front view of an electrode arrangement of the spray coating apparatus relative to FIG. 1;
FIG. 3, an axial section of the spray coating apparatus along the plane III--III in FIG. 2;
FIG. 4, scaled up, an illustration of a detail IV in FIG. 3;
FIG. 5, a side view of another embodiment of a spray apparatus according to the invention, partially in section
REFERENCES:
patent: 3393662 (1968-07-01), Blackwell
patent: 3764068 (1973-10-01), Lacchia
patent: 4114810 (1978-09-01), Masuda
patent: 4572437 (1986-02-01), Huber et al.
Bergmann Karl H.
Sonnleitner Adolf H.
Kashnikow Andres
Morris Lesley D.
Ransburg Corporation
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