Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
CA 02327752 2000-12-07
Atty. Docket No. 965
ELECTROSTATICALLY COATING NON-CONDUCTIVE BOTTLES
BACKGROUND OF THE INVENTION
The invention relates generally to electrostatic coating, and more
particularly
to processes and systems for electrostatically coating non-conductive
articles.
It is known generally to electrostatically coat non-conductive articles. U.S.
Patent No. 5, 830,274 entitled "Electrostatic Deposition of Charged Coating
Particles Onto A
Dielectric Substrate", for example, discloses an electrostatic coating system
having a pointed
electrode with screw-like projections protruding therefrom disposed in a non-
conductive bottle
for drawing electrically charged paint onto an outer surface thereof.
An object of the present invention is to provide novel processes and systems
for electrostatically coating non-conductive articles that improve upon and
overcome problems
in the prior art.
Another object of the invention is to provide novel electrostatic coating
processes and systems for non-conductive articles having improved efficiency.
A further object of the invention is to provide novel electrostatic coating
processes and systems having improved coating coverage, particularly on non-
conductive
articles, for example non-conductive bottles.
Another object of the invention is to provide novel electrostatic coating
processes and systems for non-conductive containers comprising an electrode
with a plurality
of bristles disposed in the container to draw a charged coating onto an outer
surface thereof.
It is yet another object of the invention to provide novel electrostatic
coating
processes and systems for non-conductive containers having an electrode
comprising water
disposed within the container to draw a charged coating onto an outer surface
thereof.
A more particular object of the invention is to provide novel systems for
electrostatically coating non-conductive articles generally comprising an
electrostatic dispenser
on one side of the non-conductive article, and an electrode at an electrical
potential different
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from that of the coating dispenser on an opposite side of the article as the
coating dispenser,
the electrode having a plurality of discrete conductive protrusions extending
therefrom.
Another more particular object of the invention is to provide novel systems
for
electrostatically coating non-conductive articles generally comprising an
electrostatic coating
dispenser on one side of the article, and a conductive fluid at an electrical
potential dilTerent
from that of the coating dispenser disposed on an opposite side of the article
as the dispenser.
These and other objects, aspects, features and advantages of the present
invention will become more fully apparent upon careful consideration of the
following
Detailed Description of the Invention and the accompanying Drawings, which may
be
disproportionate for ease of understanding, wherein like structure and steps
are referenced
generally by corresponding numerals and indicators.
BRIEF DESCRIPTION OF THE DRAWINGS
FIG. 1 is an exemplary system for electrostatically coating non-conductive
articles.
FIG. 2 is an alternative electrode configuration for electrostatically coating
non-
conductive articles.
DETAILED DESCRIPTION OF THE INVENTION
FIG. 1 illustrates a system 10 for electrostatically coating non-conductive
articles, for example glass and plastics and other dielectric materials, and
particularly non-
conducting containers having openings. In the exemplary application, the
container is a plastic
bottle 20 having a neck portion 22 with the opening thereon.
The system 10 generally comprises an electrostatic coating dispenser 30, for
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example the Aerobell-33 coating applicator by ITW Ransburg, Indianapolis,
Indiana, that
dispenses an electrostatically charged coating material supplied from a supply
32 toward the
non-conductive article. The coating dispenser 30 is generally coupled to a
high voltage supply
34 that imparts electrostatic charge to the coating material.
In FIG. 1, an electrode 50 at an electrical potential different from that of
the
electrostatic coating dispenser 30 is disposed generally on an opposite side
of the non-
conductive article as the coating dispenser 30, thereby drawing the charged
coating material
toward the non-conductive article. In the exemplary application, the electrode
50 is disposed
least partially iv the non-conductive container or bottle 20, thus drawing the
charged coating
material toward an outer surface thereof.
In the exemplary embodiment, the electrode 50 is coupled to ground potential
by a conductive element 51. The electrode 50 and the conductor 51 may for
example be
mounted in an insulated work holder 60 suitable for holding the container 20
during the
coating operation, as is known to those of ordinary skill in the art.
The electrode generally comprises a plurality of discrete conductive
protrusions
extending therefrom. The discrete conductive protrusions preferably have
pointed tips, and
in one embodiment the plurality of discrete protrusions are a corresponding
plurality of
electrically conductive bristles.
In the exemplary embodiment, the electrode comprises an axial member 52
with a tip 53, and a plurality of bristles 54 protruding generally radially
from the axial member
52. For some applications, including the exemplary bottle coating application,
the electrode
may be in the form of a commercially available metal brush.
In the exemplary bottle coating application, the electrode and the bristles
thereof are disposed at least partially into the neck portion 22 of the bottle
20.
In the embodiment of FIG. 2, a conductive fluid 70 is disposed in the non-
conductive container 20 and is in electrical contact with the conductive
element 51 of the work
holder 60, which holds the non-conductive container. The work holder 60 may be
configured
with a sealing member to prevent leakage of the conductive fluid therefrom
when the container
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20 is inverted or may be configured to suspend the container 20 upright.
In one embodiment, the conductive fluid is water, but other conductive fluids
and conductive additives may be used alternatively. In one application, the
non-conductive
container 20 is filled with the conductive fluid.
The conductive fluid 70 generally draws the charged coating material dispensed
from the coating dispenser 30 toward the non-conductive container 20, whereby
the coating
material is relatively effciently deposited on an outer surface thereof.
While the foregoing written description ofthe invention enables one of
ordinary
skill to make and use what is considered presently to be the best mode
thereof, those of
ordinary skill will understand and appreciate the existence of variations,
combinations, and
equivalents of the specific exemplary embodiments herein. The invention is
therefore to be
limited not by the exemplary embodiments herein, but by all embodiments within
the scope
and spirit of the appended claims.
