Note : Les descriptions sont présentées dans la langue officielle dans laquelle elles ont été soumises.
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BACKGROUND OF THE INVENTION
1. Field of the Invention ~-~
This invention relates to a method for coating the -
~urfaae of a bottle or a cylindrical article. It is particularly
effective for the coating of high viscosity liquid coatings
such as paints, and is suitable for use in coating the surfaces
of bottles for beer, carbonated beverages, alcoholic liquors
and foods, and other articles of a cylindrical or like shape.
2. Description of the Prior Art
.,
Losses of liquid coatings as a result of scattering
generally occurs in spray coating. Particularly in the coating
of articles having narrow coating surfaces such as bottles, a
large amount of the liquid coating is scattered away and does not ; -
come into contact with the surfaces to be coated. This, o
course, gives rise to loss of liquid coating, inefficiency, surface
areas possibly not coated and great economical disadvantages.
SUMMARY OF THE INVENTION
The present invention was accomplished as a result of
inve~tigations made in an attempt to remove these defects.
According to this invention, spraying is carried out at a short
distance from the surface to be coated so that the range of
spray-coating a liquid coating will not fall outside the surface
to be coated, and this brings about a reduction in the losses of
the liquid coating. Since the area to be spray-coated is
small, the surface to be coated is moved to form a ribbon-like
coated zone. By moving the spray nozzle or bottle or both the
nozzle and the bottle or using a number of spray nozzles similarly,
the ribbon-like coated zone or zones are formed in a helical shape,
in contact with each other or in a partly overlapping manner,
thereby to coat the surface.
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1 Thus, the present invention provides a method for
spray-coating the surface of bottles or the like which comprises
spraying a liquid coating onto the side surface of the bottle or
the like from a spray nozzle or a plurality of juxtaposed spray
nozzle~ positioned a short distance from the bottle while
rotating the bottle around the long axis of the bottle, moving
the nozzle or nozzles, the bottle, or the nozzle or nozzle~ and
the bottle relative to each other such that the movement is
along the long axis of the bottle whereby a ribbon-like spray-
coated zone or zones in a helical shape are formed, the spray-
coated zone or zones contacting each other or partially overlapping
each other,and then spray-coated the bottom surface of the bottle '
by orienting the bottle, the spray nozzle or nozzles, or the
bottle and the spray nozzle or nozzles such that the spray ;
stri~e~ the bottom ~urface of the bottle.
BRIEF DESCRIPTION OF THE DRAWINGS
Figure 1 shows an example of an apparatus for use in
coating the entire surface including the bottom of a glass bottle
in accordance with this invention.
Figure 2 shows an example of an apparatus for coating
the side surface of a glass bottle in accordance with the present
invention.
Figure 3 shows an example of an apparatus for coating
the cylindrical article by using a number of juxtaposed spray
nozzles in accordance with the invention.
DETAILED DESCRIPTION OF THE INVENTION
The present invention is especially effective for
liquid coatings having a high viscosity of, e.g., about 10,000 to
500,000 cps,such as paints. This means that liquid coatings
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1 which do not produce a wide spraying area because of their high
viscosity can also be applied by the method of this invention.
~igh viscosity liquid coatings can be spray-coated if their
viscosity is reduced by heating, e.g, to about 50C. Furthermore,
when a gas heated, e.g., such a~ air or an inert gas, at about
50 to 250C i9 used for spraying, the time required to heat the
paint can be markedly shortened. If such a heated gas is used
concurrently in the present invention, reactive high viscosity
liquid coatings which tend to react by heating can be easily
spray-coated. A suitable pressure range which can be employed
in the spray coating is about 3 to 5 kg/cm . Thus, according to
the present invention, the range of spray-coatable viscosities,
e.g, as high as about 500,000 cps, and the range of components
that can be incorporated in the liquid coating can be broadened.
Thi~ is in contrast to conventional methods in which difficulties
occur in spray coating of liquid coatings having a viscosity of
only as high as about 10,000 cps. Further, this permits the use
of reactive liquid coatings and high viscosity liquid coatings
which do not contain toxic solvents, and is effective not only
for reducing the losses of liquid coating by spraying but also
for controlling pollution and maintaining a clean environment.
Suitable liquid coatings which can be effectively coated in the
invention include, but are not to be construed as being limited
to, polyurethane coatings ~non-solvent type) (either one-package
type or two-package type), epoxy-polyamide-type coatings (non-
solvent type), etc.
One specific procedure for coating a bottle or the
like by the present invention involves moving a spray nozzle, whose
orifice can be of any conventional size and shape, along the long
axis of the bottle or the like at a short distance from the surface
to be coated. Desirably, the distance between the nozzle and
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1 the surface to be coated is adjusted suitably according to the
shape or size of the portion to be coated. In the case of coating
hottles, it is desirable to move the nozzle while changing
the distance between the nozzle and the surface to be
coated according to the diameter or shape, etc., of the bottle
at a position on its long axis. Alternatively, if desired, the
bottle can be moved with respect to the spray nozzle or both the
nozzle and the bottle can be moved with respect to each other.
In any of the embodiments suitably used in the present invention
the relative movement is along the long axis of the bottle.
The bottom surface of the bottle can be coated by -
directing the nozzle toward the bottom surface at a position
beyond the bottom of the bottle. Furthermore, two or more spray
nozzles can be used, and the position, spraying conditions and
moving range of each of the nozzles can be determined according
to the shape, size, etc., of the position of the bottle. Instead
of forming the coated zone in a helical shape by moving the
nozzle, the bottle or both, a number of spray nozzles can be
disposed along the long axis of the bottle, thus maintaining the
coated zbnes in contact with each other in juxtaposition or in a
partly overlapping manner. Again, if desired, a similar relative
movement of the bottle with respect to the spray nozzles as
described above can be employed. It is also possible to fix a
spray nozzle for coating the bottom of the bottle at a suitable
position near the bottle in a manner such that the spray from the
nozzle is directed toward the bottom surface of the bottle.
It is to be further emphasized that the method of this
invention is applicable to both regularly shaped cylindrical
articles to be coated and irregularly shaped cylindrical articles
to be coated and that the spray nozzle and the cylindrical article
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1 can be moved relative to each other by moving either or both so
that the distance between the spray nozzle and the article surface
at any point along the article surface and the spray area are
maintained substantially constant. Particularly where the surface
of the article is irregularly shaped, it is simpler and
preferred to maintain the article in a stationary position while
rotating the article about its long axis and moving the spray
nozzle along the bottle surface in the direction of the long
axis and at the same time following the contour of the article
~urface along the long axis so as to maintain the spray distance
and spray area covered substantially constant. Similarly, where
a plurality of spray nozzles is employed and they are positioned
along the cylindrical article surface the same techniques can
be employed, of course, with-appropriate modifications in
relative movement being made since more of the article surface
is being spray-coated at the same time because of the use of more
than one spray nozzle. Further, where a plurality of spray
nozzles are used, they can be positioned and spaced such that
the contour of the article surface and the spray area resulting -
is taken into consideration.
As described hereinbefore, a conventionally sized and
shaped nozzle or nozzles are used in this invention. Therefore,
when the liquid coating of this invention is sprayed on the
surface of a bottle at a gas pressure of about 3 to 5 kg/cm2, a
suitable range of the distance of the spray nozzle(s) from the
surface of the bottle is about 2 to 10 cm. That is, since, in
- general, an oval sprayed shape is generated on the bottle surface,
the spray angles to the surface are about 30 and about 60 with
respect to the short axis of the oval and to the long axis of the
oval, respectively, it is necessary to spray the liquid coating
at a distance of 3.7 cm or less and 14 cm or less in narrow
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1 portions of the bottle or cylindrical article to be coated (e.g.,
a diameter: 2.5 cm) and in the broader portions of the bottle or
cylindrical article to be coated (e.g., a diameter: 7.5 cm),
respectively, and in practice, the liquid coating is preferably
~prayed onto the surface of the bottle at a distance of 3 cm and
6 to 10 cm in the narrow and broad portions, respectively.
Apparatuses for performing the present invention are
illustrated by the accompanying drawings. Figure 1 shows an
example of an apparatus for use in coating the entire surface
(including the bottom surface) of a glass bottle using a two-
package high viscosity liquid coating. Figure 2 shows an example ;
of an apparatus for coating the side surface of a glass bottle.
Figure 3 shows an example of an apparatus for coating a cylindri-
cal article by using a number of spray nozzles disposed in
juxtaposition; and in Figure 1, reerence numeral 1 represents
a glass bottle; 2 and 2', a spray nozzle; 3, a tank for stirring
a liquid coating: 4, a heating device for the spray gas; 5 and
5', a reservoir for a two-package liquid coating; 6 and 6', a
metering pump for the liquid coating; 7 and 7', the moving path
of the spray nozzle; and 8, a device for maintaining and rotating
the bottle. In Figures 2 and 3, reference numeral 1 represents
an article to be spray-coated; 2, a spray nozzle; 3, a liquid
coating inlet of the spray nozzle; and 4, a spray gas inlet of the
spray nozzle.
The following Examples are given to specifically
illustrate the method of this invention.
EXAMPLE 1
-
Using an apparatus of the type shown in Figure 1, the
entire surface of a beer bottle was spray-coated in the following
manner with a reactive-curable two-package coating (IM-178 ENAMEL,
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1(~ii~095 ~
1 trademark for a product of Toyo Ink Mfg. Co., Ltd.; viscosity,
#4 Ford cup, 4 seconds). The beer bottle was held by a holding
member 8, and the bottle was rotated at a speed of 60 revolutions
per minute. The coatings were supplied in predetermined propor~
tions to a mixing-stirring tank 3 from reservoirs 5 and 5' by
means of metering pumps 6 and 6^. The mixture was fed to spray
nozzles 2 and 2', and sprayed using air heated at 150C in
an air-heating device 4. The spray nozzles 2 and 2' were moved
at a rate of 3 cm/sec through the paths shown by 7 and 7'. The -
liquid coating was sprayed at a distance of 2 to 5 cm from the
surface of the bottle. The edge areas of the ribbon-like coated
zones, each with a width of about 2 to 5 cm, were caused to ~ -
partly overlap in a helical shape, and the side surface of the
bottle was thus coated. The spray nozzle-Q were directed at the
posi~ion 7' toward the bottom surface of the bottle, as shown at
2'. After the coating, the coated bottle was heated at 120~C
for 20 minutes to cure the coating.
EXAMPLE 2
As shown in Figure 2, a glass bottle 1 with a capacity
of 633 ~ was maintained transversely horizontal or longitudinally
vertical, and rotated at a rate of 60 revolutions per minute.
A reactive one-package urethane coating (SLN-7, trademark for a
product of Toyo Ink Mfg. Co., Ltd.; viscosity 100,000 cps at
25C) was placed in a pressure tank. The tank was connected to
a spray gun 2(W-61~0, a trade name of Iwata Tosoki Kogyo
Kabushiki Kaisha), and using air 4 heated at 150C, the paint
was spray-coated on the bottle at a blow pressure of 3.5 kg/cm2.
The distance between the side surface of the glass bottle and
the spray nozzle was 3 cm, and the rate of the movement of the
nozzle parallel to the bottle axis was 3 cm/sec. After the
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1 coating,the bottle was maintained horizontal ~ if the bottle is
maintained vertical at the time of coating, the bottle is then
turned horizontal) and baked in an oven at 220C for 12 minutes
while rotating the bottle. A coated bottle having a coating
with a thickness of 200 microns was obtained.
EXAMPLE 3
A tin can, 70 mm in diameter and 120 mm length was
coated with a reactive-curable two-package mixed liquid coating
~IM-178 ENAMEL, trademark for a product of Toyo Ink Mfg. Co.,
Ltd.; viscosity, #4 Ford cup, 20 seconds) using the same spray
gun as described in Example 2 at a blow pressure of 3.~ kg/cm2
using air at room temperature (i.e., 20~-30C). After the
coating, the coated tin can was baked at 120& for 20 minutes to
form a coating having a thickness of about 50 microns.
EXAMPLE 4
A~ shown in Figure 3, a glass tube 1 with a diameter
of 60 mm and a length of 1300 mm was maintained horizontal, and
while the glass tube was rotated at a speed of 30 revolutions per
minute, the glass tube was coated with a solvent-type urethane
resin coating (IX-060 CLEAR, trademark for a product of Toyo Ink
Mfg. Co., Ltd.; viscosity, #4 Ford cup, 20 seconds) by spraying
at a blow pressure of 3 kg/cm2 from spray nozzles 2 disposed at
intervals of 5 cm ~ATOMIZING NOZZLE JBC, trademark for a product
sold by Empire Trading Co., Ltd,) using air at room temperature.
The coated glass tube was dried at 120C for 30 minutes to form
a coating having a thickness of 50 microns.
While the invention has been described in detail and with
reference to specific embodiments thereof, it will be apparent to
one skilled in the art that various changes and modifications can
be made therein without departing from the spirit and scope thereof.
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