JP3213150B2 - Electrostatic coating method of metallic paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic coating method for supplying a metallic paint from a paint supply source through a paint pipe connected to an electrostatic painting machine to which a high voltage is applied. Related to the painting method.

[0002]

2. Description of the Related Art In electrostatic coating, a coating material is electrostatically atomized by applying a high voltage to an electrostatic coating machine. In this case, since the non-conductive paint has a large electric resistance, when a high voltage is applied to the electrostatic coating machine, the high voltage does not leak through the paint supply system, but the conductive paint has an electric resistance. Therefore, high voltage may leak through the paint supply system, and therefore, insulation measures are taken for the paint supply system.

[0003] By the way, the metallic paint contains a conductive fine metal foil or the like dispersed in an organic paint component, and is non-conductive as a paint. It is known that when a phenomenon called metal bridges are arranged in a line, the electric resistance is reduced like a conductive paint. When the metallic paint is flowing through the paint pipe, the metal bridge is unlikely to occur even when a high voltage is applied, and when the metallic paint is stopped flowing rapidly (1 second). It has been found that when a high voltage is applied by boosting the voltage to within), a metal bridge is likely to occur due to the shock. In particular, when the object to be coated is continuously conveyed, when the application of the preceding object to be coated is completed and the application of the high voltage is stopped, and when the subsequent object to be applied arrives and the high voltage is applied, Overcurrent flows through the metal bridge, causing the high voltage generator to switch off and the paint line to shut down.

For this reason, when performing electrostatic coating with a metallic paint, first, a metallic paint is supplied to flow the metallic paint in the paint pipe, and then a high voltage is applied so as not to cause a metal bridge. In a state where the metallic paint in the paint pipe is not flowing, the pressure is gradually increased over several seconds (3 to 5 seconds), a high voltage is applied, and then the metallic paint is supplied to start painting.

[0005]

However, when applying a high voltage after flowing the metallic paint in the paint pipe, paint that is not electrostatically atomized is first sprayed from the painting machine. When the portion is used for painting, there is a problem that paint that has not been atomized adheres, resulting in poor painting. In order to prevent this, immediately before the start of painting, the paint that has not been electrostatically atomized must be sprayed and discarded, but at that time, the paint is already attached to the work because it is already approaching. It is very difficult to not spray.

In this regard, if the metallic paint is supplied and the coating is started after applying a high voltage by gradually increasing the pressure, it is not necessary to wastefully discard the paint. Depending on the coating color of the object to be transported, paint piping and coating must be completed within a limited short time from the end of coating of the preceding object to the start of coating of the subsequent object. The paint remaining in the machine must be cleaned, filled with the next color paint, and then waited. Therefore, if a boosting time of several seconds must be secured during this time, the cleaning time is further shortened, so that sufficient cleaning cannot be performed, and there is a problem that color mixing occurs. Therefore, the present invention
When applying electrostatic paint using metallic paint, there is no need to wastefully discard paint that has not been atomized immediately before the start of painting, and also avoid metal bridges when high voltage is applied. Is a technical issue.

[0007]

In order to solve this problem, the present invention is to supply a metallic paint from a paint supply source through a paint pipe connected to an electrostatic coating machine to which a high voltage is applied. In a method of electrostatically coating a metallic paint for performing electrostatic painting, the metallic paint is separated from a portion to which a high voltage is applied by a distance longer than a predetermined insulation length along a paint pipe. And a switching valve device for switching and supplying a cleaning solvent and cleaning air is interposed,
After application ends, as well as emptied by supplying cleaning solvent and cleaning air from said switching valve device to wash the inside coating pipes, to wait in a state in which no high voltage is applied to the electrostatic coating machine, the switching Supply of metallic paint from valve unit started
At the start of painting, paint pipes that are not separated by a predetermined insulation length from the part to which high voltage is applied in the electrostatic painting machine
Before the metallic paint reaches the high voltage region, a high voltage is applied to the electrostatic coating machine in advance.

[0008]

According to the present invention, when a high voltage is applied to the electrostatic coating machine and the paint pipe at the start of coating, the paint pipe is empty and the electrostatic coating to which the high voltage is applied is applied. No metal bridge is formed even if the pressure is increased rapidly because the metallic paint is not filled in the machine and the paint piping. Then, when the metallic paint is supplied and reaches the high voltage region where the high voltage is applied, since the high voltage is applied to the region, the high voltage is applied in a state where the metallic paint is flowing, Therefore, no metal bridge occurs. Further, since the metallic paint sprayed from the coating machine is electrostatically atomized from the beginning and is not sprayed without applying a high voltage, it is not necessary to wastefully discard the paint.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be specifically described below based on embodiments shown in the drawings. FIG. 1 is a time chart showing an example of the method of the present invention, and FIG. 2 is a flow sheet showing an example of an electrostatic coating apparatus used in the method of the present invention.

In FIG. 2, reference numeral 1 denotes an electrostatic coating apparatus which supplies a metallic paint through a paint pipe 3 connected to an electrostatic coating machine 2 to which a high voltage is applied to perform electrostatic coating. The electrostatic coating machine 2 is electrically connected to the high voltage generator 4, and the paint pipe 3 is formed of an insulating paint hose. Then, when the distance from the portion where the high voltage is applied to the electrostatic coating machine 2 is longer than the predetermined insulation length Y along the paint pipe 3, the metallic paint of each color, the washing solvent and the washing air are switched. A color changing device (switching valve device) 5 for supplying the paint and a regulator 6 for supplying paint to the electrostatic coating machine 2 at a constant rate are provided.

The color changing device 5 supplies paint valves V _{1 to} Vn, which supply metallic paint of each color to the manifold 7.
Become washed air valve Va and cleaning solvent valve Vt is provided, wherein with each paint valves V ₁ to Vn are connected to the paint supply source for each color metallic coating each, washed air valve Va and cleaning solvent valve Vt is, compressed air It is connected to a supply source and a cleaning solvent supply source, respectively, and is electrically connected to ground.

In the electrostatic coating machine 2, the paint supplied through the paint pipe 3 at the time of painting is supplied to the atomizing head 8, and the cleaning solvent and the cleaning solvent supplied through the paint pipe 3 at the time of cleaning. A trigger dump valve Vp for discharging air to the waste liquid tank 9 together with the remaining paint in the paint pipe 3 is incorporated.

[0013] Next, the present invention method, color change of the object to be coated prior to coating with silver metallic paint supplied from the paint valve V _1, red metallic paint supplied subsequent article to be coated from the coating valve V ₂ An example of the case of painting will be described with reference to FIG.

First, during the coating of the preceding object,
With triggers dump valve Vp is connected to the atomizing head 8 side, the paint valve V ₁ of the color change device 5 is opened is supplied silver metallic paint, a high voltage electrostatic coating machine 2 by the high voltage generator 4 (FIG. 1: T _{1 to} T
₂ ). At this time, the high-voltage region 3a in which the distance from the portion of the electrostatic coating machine 2 to which the high voltage is applied is not separated by the predetermined insulation length Y along the paint pipe 3 is affected by the high voltage. . When the painting is completed, the trigger dump valve Vp is connected to the waste liquid tank 9 side, and at the same time, the paint valve V ₁ is closed to stop the supply of the silver metallic paint, and the supply of the high voltage from the high voltage generator 4. Is stopped (FIG. 1: T ₂ ).

Next, the cleaning air valve Va and the cleaning solvent valve Vt are alternately opened and closed to supply the cleaning air and the cleaning solvent alternately, and the paint remaining in the paint pipe 3 is removed by the cleaning air,
When the inside of the paint pipe 3 is cleaned by discharging to the waste liquid tank 9 with the cleaning solvent, the inside of the paint pipe 3 becomes empty (FIG. 1: T ₃ to T ₃ ).
T _4).

In this state, the apparatus waits until the subsequent object arrives (FIG. 1: T _{4 to} T ₅ ). When the subsequent object arrives, the trigger dump valve Vp is moved to the atomizing head 8 side. connect, opening the paint valve V2 to start supply of use and red metallic (Figure 1: T _5), performs a painting. At this time ,
The high voltage area 3a of the paint pipe 3 where the distance from the portion of the electrostatic coating machine 2 to which the high voltage is applied is not separated by a predetermined insulation length.
Before the red metallic paint arrives, a high voltage is applied to the electrostatic coating machine 2 in advance .

In this embodiment, the application of the high voltage by the high voltage generator 4 and the supply of the red metallic paint are performed simultaneously (FIG. 1: T ₅ ). This is because the red metallic paint is supplied from the manifold 7 to the paint pipe. This takes into account the time lag from the point of passing through 3 to the high voltage region 3a. That is, even if the application of the high voltage and the supply of the paint are performed simultaneously, when the paint reaches the high voltage region 3a, the high voltage has already been applied to the high voltage region 3a. If the paint pipe 3 is sufficiently longer than the predetermined insulation length Y and the time lag until reaching the portion to which the high voltage is applied is longer, the application of the high voltage and the supply of the paint are not performed at the same time. After starting the supply of the red paint, the application of the high voltage may be started. Conversely, when there is almost no time lag, the supply of the metallic paint may be started after the high voltage generator 4 is first turned on to apply a high voltage.

Therefore, a high voltage is applied to the electrostatic coating machine 2.
(Figure 1: T_Five), The high voltage area of the paint pipe 3
3a is empty and filled with metallic paint
There is no metal bridge. Ma
Also, the metallic paint reaches the high voltage area 3a of the paint pipe 3.
(Figure 1: T ₆), The metallic paint flows
Cause a metal bridge even when a high voltage is applied.
Never rub. In addition, metallic paint is used for electrostatic coating
When spraying from the machine 2, the electrostatic coating machine 2 is already high.
Since voltage is applied and electrostatic atomization always occurs,
No need to throw away.

The paint valves V _{1 to} V ₁ of the color changing device 5
n is not limited to the case where only the metallic paint is supplied,
For example the metallic coating is applied to the V ₁ ~V _5, V ₆ ~
Vn may be the case where a normal paint is supplied. In short, it is sufficient that a metallic paint is supplied even for one color.
Further, the method of the present invention can be applied not only to a multicolor coating apparatus but also to a coating apparatus to which a single-color metallic paint is supplied.

[0020]

As described above, according to the present invention, when a high voltage is applied to the electrostatic coating machine, the high-voltage region of the paint pipe is vacant. Is not applied, and when the metallic paint reaches the high voltage region, a high voltage is applied to the electrostatic coating machine, and the metallic paint is applied with a high voltage in a flowing state. It has an excellent effect that metal bridges can be prevented beforehand. Furthermore, the metallic paint sprayed from the coating machine is electrostatically atomized from the beginning,
Because it is not sprayed without high voltage applied,
This has the effect of eliminating the need to wastefully dispose of the paint.

[Brief description of the drawings]

FIG. 1 is a time chart illustrating the method of the present invention.

FIG. 2 is a flow sheet showing an electrostatic coating apparatus for implementing the method of the present invention.

[Explanation of symbols]

1 ... electrostatic coating apparatus 2 ... electrostatic coating machine 3 ... paint pipe 4 ... high voltage generator 5: color change device (switching valve device) 7 ... manifold V ₁ ~ Vn: Paint valve Vt: Cleaning solvent valve Va: Cleaning air valve Vp: Trigger dump valve

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-3-42064 (JP, A) JP-A-55-111856 (JP, A) (58) Fields investigated (Int. Cl. ⁷ , DB name) B05D 1/06 B05D 5/04

Claims (1)

(57) [Claims] 1. An electrostatic coating apparatus for supplying a metallic paint from a paint supply source through a paint pipe (3) connected to an electrostatic painting machine (2) to which a high voltage is applied to perform electrostatic painting. in the coating method, from the portion where the high voltage of the electrostatic coating machine (2) is applied
A switching valve device (5) for switching and supplying the metallic paint, the cleaning solvent and the cleaning air is interposed at a position where the distance is longer than a predetermined insulation length along the paint pipe (3), and the coating is completed. Thereafter, a cleaning solvent and cleaning air are supplied from the switching valve device (5) to clean and empty the paint pipe (3), and no high voltage is applied to the electrostatic coating machine (2). In the standby state, supply of metallic paint from the switching valve device (5) is started.
Painting start to start the coating of the distance from the portion where the high voltage electrostatic coating machine (2) is applied is not separated by a predetermined insulation length
A high voltage is applied to the electrostatic coating machine (2) before the metallic paint reaches the high voltage area (3a) of the feed pipe (3). Electric painting method.