Coating processes – Spraying – Moving the base
Reexamination Certificate
1999-08-25
2001-05-29
Bareford, Katherine A. (Department: 1762)
Coating processes
Spraying
Moving the base
C427S421100, C427S426000, C118S302000, C118S324000
Reexamination Certificate
active
06238746
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Field of the Invention
The present invention relates to a method and an apparatus for painting vehicle bodies successively carried along a painting line with a suitable color paint selected from a variety of color paints.
2. Prior Art
In well-known prior art painting method, a vehicle body is coated in three different steps, i.e. primer coating for corrosion proofing with the use of electrodeposition coating method; surfacer painting for painting an intermediate coat such as gray color on the primer coating layer; and top coating for painting a desired paint on the intermediate coating layer. In top coating, a variety of different color paints (10 to 30 colors,) are applied to the vehicle bodies, which are successively carried along a conveyor and divided into groups according to a color paint to be applied. To this end, the painting apparatus comprises pluralities of parallel paint-transferring lines L
1
, L
2
, L
3
. . . LN, such as shown in FIG.
6
. The number of the paint-transferring lines corresponds to the variety of the color paints applied to vehicle bodies. At one end of the respective paint-transferring lines L
1
, L
2
, L
3
. . . LN, a paint tank
35
is positioned so as to reserve a paint having a certain viscosity, which is prepared from different color paints to be mixed. Provided at the other end of these lines L
1
, L
2
, L
3
. . . LN is a paint-changing unit
32
such as disclosed in Japanese Patent No. 1822017. The paint-changing unit
32
is used for in turn selecting a required color paint and transferring the selected color paint to a spray gun G.
In such painting apparatus, there is provided a washing unit C in parallel relation to the paint-transferring lines L
1
, L
2
, L
3
. . . LN. When changing a color paint to be applied, the washing unit C ejects washing liquid into a connecting hose
33
between the paint-changing unit
32
and the spray gun G, thereby cleaning remaining paint within the hose. New color paint is then supplied to the spray gun G through the connecting hose
33
thus cleaned.
SUMMARY OF THE INVENTION
In the above conventional method and apparatus, since a variety of color paints are applied on the intermediate coating layer which is formed by a single common intermediate coat such as gray color, in most cases there are no similarities in hue between the paints applied for the surfacer painting and the top coating. In order to ensure uniform appearance of the top coating applied on the intermediate coating layer having non-similar hue, the top coating layer should be thicker such as 60 microns thick. This leads to increasing amount of the paints to be applied. Further, since top coating is also required for the reverse side of a trunk and the reverse side of a bonnet, where appearance of the coating layer is not normally required, operation for the top coating would be time-consuming. Moreover, since a large number of paint-transferring lines L
1
, L
2
. . . are provided in parallel and each of the paint-transferring lines includes a flow control valve
31
, the painting apparatus would be larger in its layout space and be complicated in its construction.
In the above conventional painting apparatus, since the paint-changing unit
32
for 10 to 30 kinds of top coating color paints would be larger in its size and weight, it is not mounted on an arm of a vehicle body painting robot, which holds the spray gun G. The paint-changing unit
32
is therefore attached to the factory building adjacent to the paint-transferring lines, and a huge length of connecting hose
33
connects the paint-changing unit
32
and the spray gun G. When the top coating color paint now in use is changed to another color paint, the remaining paint within the connecting hose
33
should be discharged. For this reason, washing liquid made from organic solvents is used for cleaning such huge length of connecting hose
33
. As a result, a large amount of the washing liquid is required to clean the connecting hose
33
and a large amount of paint is discharged, leading to increasing amount of toxic liquid wastes from the factory as well as increasing amount of waste materials. Further, since cleaning of the connecting hose
33
is time-consuming, operation for changing a color paint affects the efficiency for painting vehicle bodies.
Meanwhile, emission regulation for carbon dioxide and regulation for toxic industrial liquid waste such as organic solvents tend to be more and more strict, and accordingly technology development in the related field is required on decreased use of organic solvents and toxic wastes in the painting line. The present invention seeks to provide a method and an apparatus for painting vehicle bodies with a variety of color paints, which eliminate the above difficulties of the prior art and satisfy the above requirements in this field.
In view of the above, the object of the invention is to provide a method of painting successively carried vehicle bodies with a suitable color paint selected from a variety of color paints, comprising the steps of:
transferring a plurality of primary color paints along corresponding paint-transferring lines;
selecting and extracting necessary primary color paints for preparation of said suitable color paint at the end of the paint-transferring lines and setting a certain ratio between said extracted primary color paints based on delivery rate of a delivery pump provided in the respective paint-transferring lines; and
preparing the suitable color paint having a certain viscosity by mixing the thus extracted primary color paints at an intermediate of a paint-transferring passage connecting the end of the paint-transferring lines and a spray gun.
Another object of the invention is to provide a method of painting vehicle bodies, the method including primer coating, surfacer painting and top coating, characterized in that the surfacer painting is carried out by the aforementioned method and in that paint used for the surfacer painting has the same or similar color to that used for the top coating.
The present invention also provides an apparatus for painting successively carried vehicle bodies with a suitable color paint selected from a variety of color paints by the use of a spray gun comprising:
a plurality of parallel paint-transferring lines, each provided with a primary color paint tank and a delivery pump;
a primary color paint selecting/extracting unit having a change valve and connected to one end of the paint-transferring lines;
an agitating unit provided at an intermediate of a paint-transferring passage between the primary color paint selecting/extracting unit and the spray gun and preparing the suitable color paint having a certain viscosity by mixing the primary color paints selected and extracted at the primary color paint selecting/extracting unit;
a washing unit connected at one end of the paint-transferring passage; and
a control unit which, based on a previously input painting program, automatically controls:
(a) opening and closing operation of the change valve so as to select and extract necessary primary color paints for preparation of the suitable color paint;
(b) delivery rate of the respective delivery pumps in the paint-transferring lines so as to adjust the mixing ratio of the extracted primary color paints;
(c) viscosity of the suitable color paint at the agitating unit; and
(d) cleaning operation in the paint-transferring passage by the washing unit.
According to the present invention, in stead of the conventional painting method and apparatus, in which all the color paints extending to 30 kinds are separately prepared and reserved in the corresponding paint tanks and supplied to the spray gun, said all the color paints are prepared from a few kinds of primary color paints reserved in corresponding primary color paint tanks. Necessary primary color paints are selected and extracted from the few kinds of primary color paints, and they are mixed such that a certain amount of a suitable color paint having a certain viscosity is prepared and supplied to
Fukuoka Hidemoto
Hirata Koutarou
Tajima Emitsu
Yasuda Tetsuya
Bareford Katherine A.
Honda Giken Kogyo Kabushiki Kaisha
Liniak Berenato Longacre & White
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