Fluid sprinkling – spraying – and diffusing – Processes – Including electrostatic charging
Patent
1984-12-04
1988-04-05
Kashnikow, Andres
Fluid sprinkling, spraying, and diffusing
Processes
Including electrostatic charging
239705, 239296, 239403, B05B 502
Patent
active
047353600
DESCRIPTION:
BRIEF SUMMARY
The present invention relates to a method for electrostatic powder coating by spraying powder particles entrained in a carrying gas stream upon a surface to be coated, using a spray device, in particular a spray gun, in which method the powder is dispersed by carrying gas and the carrying gas powder mixture discharged from an outlet nozzle in an axial direction is expanded by control air introduced into the carrying gas powder mixture through a radial gap in a substantially radial direction, and the carrying gas powder mixture is ionized, and the invention furthermore relates to an apparatus for performing such method.
In a known spray apparatus as shown in German Patent Specification No. 23 12 363 the carrying gas powder mixture is passed by a deflection device ejecting an air stream in a radial direction. By regulating the radial air stream various patterns of a powder mist may be obtained. For ionizing the powder an electrode disposed within a tube in the path of the carrying gas powder mixture is provided.
From German Patent Specification No. 24 46 022 it has become known to branch off a partial air stream from a dispersing air stream and to ionize said partial air stream when passing by at least one needle electrode and to direct said partial air stream towards the projecting spray jet. Said needle electrode freely projects outwardly and faces the surface to be coated.
From U.S. Pat. No. 3,049,092 a spray apparatus for wet paint has become known, in which the dispersing air is radially deflected from a baffle and the ejected air stream is used to disperse the wet paint axially projecting from an annular gap. The atomizing air stream may be regulated only within restricted limits with a view to complete dispersion of the paint. Ionization is achieved by corona at the area of the peripheral edge of the baffle, a high voltage being applied to the spray head.
A primary object to be solved by the present invention is to provide a method and an apparatus for electrostatic spray powder coating allowing to achieve improved spray patterns and to ionize the powder particles such as to provide for a more uniform coating of the workpiece surface.
The present invention as well as further developments of the invention are defined in the claims.
According to the present invention the ionized gas stream is discharged separately from the control air stream serving to expand the carrying gas powder mixture. Since the control air stream is controllable both with respect to pressure and mass, a desired pattern of the spray mist may be obtained in a simple and advantageous manner. Ionization of the carrying gas powder mixture is obtained by the ionized gas stream fed into the carrying gas powder mixture downstream of the control air stream. So the ionized gas stream is fed into the carrying gas powder mixture in a zone of reduced flow velocity, i.e. downstream of the control air stream for expanding and retarding, such that the time period for ionization of the powder particles is increased.
By the positioning of the electrode a direct field influence on the surface to be coated is avoided. The indirect influence which the electrical field originating from the electrode has upon the surface to be coated is decreased. In particular a field line concentration at edges and projections of the surface to be coated is avoided such that a more uniform coating is obtained. Furthermore the ionized gas stream is independent of the control air stream and accordingly is adjustable in an extremely efficient manner.
According to patent claim 2 the carrying gas powder mixture may be directly charged additional to the electrostatic charging by the ionized gas stream. The electrostatic charging of the powder particles may be varied and effectively adjusted by controlling the direct charging and by controlling the ionized gas stream. Controlling of the direct charging may be obtained either by varying the voltage applied to the electrode or by weakening the electric field. Charging of the ionized gas stream is preferably obtained by contro
REFERENCES:
patent: 3049092 (1962-08-01), Sedlacsik et al.
patent: 3606972 (1971-09-01), Ferrant
patent: 3759151 (1972-08-01), Fabre
patent: 3819115 (1974-06-01), Soderman
patent: 4235381 (1980-11-01), Vila
patent: 4324361 (1982-04-01), Moos et al.
patent: 4341347 (1982-07-01), De Vittorio
patent: 4380320 (1983-04-01), Hollstein et al.
Gebhardt, deceased Otto
Kirchner Wolfgang
Kashnikow Andres
Kopperschmidt-Mueller GmbH & Co. KG
LandOfFree
Method and apparatus for electrostatic spray powder coating does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus for electrostatic spray powder coating, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus for electrostatic spray powder coating will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2229494