JPS5824186B2 - Electrostatic coating method for metallic paint - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for electrostatic coating of metallic paints containing conductive metal pigments.

Conventionally, when electrostatically painting paints containing conductive metal pigments such as metallic paints, due to the nature of metallic paints, one end of the paint supply hose is provided with a grounding section, and the other end is grounded. When a high voltage was applied to the metallic paint in the hose, under certain conditions during electrostatic painting, the dielectric strength of the metallic paint was suddenly destroyed, causing a large current to flow through the metallic paint.

This phenomenon is generally called the pearl chain phenomenon or bridge phenomenon, and the metal pigments contained in the metallic paint are connected in a series to form a chain, and this metal pigment conducts between the high voltage application part and the ground part. It is something that is caused.

This phenomenon is influenced by the metal pigment content in the metallic paint, the diameter and length of the paint hose, the flow rate of the paint flowing through the paint hose, etc.

When this phenomenon occurs, the paint in the paint hose becomes
Electrically, it exhibits properties similar to metal conductors, and the high voltage applied to the electrostatic coating machine is short-circuited to ground, preventing normal electrostatic coating.

Once this bridging phenomenon or Perlchen phenomenon occurs, it is difficult to destroy it, but if the high voltage applied to the high voltage application section is interrupted even temporarily,
It has the characteristic that it can be easily destroyed.

The purpose of the present invention is to automatically detect the so-called bridging phenomenon or pearl chain phenomenon described above in an air electrification type or hydraulic atomization type electrostatic coating machine, and to destroy this phenomenon. To provide a method for electrostatically coating a metallic paint with a simple structure and capable of automatically performing normal electrostatically coating again after the coating has been applied.

The basic structure of the present invention is an electrostatic coating method for metallic paint, in which metallic paint is atomized and simultaneously charged by a high-voltage electrode, and the metallic paint is applied to an object to be coated to which a high voltage is applied at a potential opposite to that of the metallic paint. In this case, high-voltage electrode force is created by connecting the metal pigments contained in the metallic paint supplied from the paint supply source in a chain.
A current flowing toward the grounding part of the paint supply source is detected, and upon detection of this current, the high voltage application to the high voltage electrode is interrupted, and after one moment, the electrical conductivity of the metallic paint disappears, and then the high voltage is applied to the high voltage electrode. This electrostatic coating method for metallic paint is characterized by automatically restarting high voltage application and continuing coating.

Hereinafter, one embodiment of the present invention will be described based on the drawings.

The figure shows a schematic diagram of the configuration of an apparatus for carrying out the electrostatic coating method of the present invention, and an electrostatic coating machine 1 is positioned facing an object 2 to be coated.

The object 2 to be coated is grounded and is applied with a potential opposite to that of the high voltage application electrode 1a of the electrostatic coating machine 1.

The electrostatic coating machine 1 has high resistance (for example, 120MΩ to IO
2) A built-in high voltage frame 1b is installed, and the high voltage frame 1b is in contact with the electrode 1a.

The high voltage frame 1b is connected to a high voltage generator 4 via a high voltage cable 3, and the high voltage generator 4 is connected to a primary power source 5 for the high voltage generator.

6 indicates a high voltage interlock contact.

The high voltage generator 4 is connected to a high voltage and current detector 7, and the high voltage and current detector 7 is connected to a high voltage interlock circuit 8.

High voltage current detector 7 is grounded.

A paint on-off valve 10 is attached to the electrostatic coating machine 1 via a resin paint hose 9, and the paint on-off valve 10 is grounded.

Reference numeral 11 indicates a paint supply device and a paint on-off valve 1 (not shown).
0 shows a resin paint hose that connects to 0.

The high voltage interrupting device is comprised of a high voltage current detector 7 and a high voltage interlock circuit 8.

When applying metallic coating to the object to be coated 2, metallic paint is supplied from the paint hose 9 to the electrostatic coating machine 1 of the air atomization type or hydraulic atomization type, and paint mist is supplied from the atomization air inlet (not shown). At the same time, the high voltage generator 4
By applying a high voltage to the electrode 1a, the sprayed paint is charged at a high voltage and applied to the object 2 which is at an opposite potential to that of the electrode 1a.

At this time, when the so-called Perlchen phenomenon (bridge phenomenon) occurs in the paint hose 9, the electrode 1a and the paint on-off valve 10 are electrically connected by the conductive metal pigment present in the paint hose 9, so that the current does not flow. It will be grounded through the paint on-off valve 10.

Then, the current change at this time is detected by the high voltage current detector 7, and the high voltage interlock circuit 8 is driven by the discrimination signal generated from the high voltage current detector 7.

By driving the high voltage interlock circuit 8, the high voltage interlock contact 6 is interlocked to cut off the supply of current to the high voltage generator 4.

Then, the application of high voltage to the electrode 1a is cut off, so that the Pearlchen phenomenon (bridge phenomenon) occurring in the paint hose 9 disappears.

It is important that the coating continues even while the application of high voltage to the electrode 1a is interrupted.

Then, after a predetermined period of time (approximately several seconds) has elapsed, the high voltage interlock contact 6 is automatically restored to its original state, and normal electrostatic painting is resumed.

As explained above, according to the electrostatic coating method for metallic paint of the present invention, the pearl chain phenomenon (
Even if a bridging phenomenon (bridging phenomenon) occurs, the high voltage current can be momentarily limited by the high resistance built into the high voltage frame 1b, and then this phenomenon can be automatically eliminated. Electrostatic coating of metallic paints always continues, and if this invention is used in an automatic coating line, coating can continue even when high voltage is cut off to the electrodes, reducing line operating rates. This produces the effect of minimizing noise.

In addition, since all Pearlchen phenomena (bridge phenomena) are automatically eliminated, there is a great effect on labor saving, and there is also an effect that there is no danger at all since no human intervention is required.

Furthermore, it has the advantage of being simple in structure and reliable in operation.

[Brief explanation of the drawing]

The figure is a schematic side view showing the initial configuration of an apparatus for implementing the present invention. 1...Electrostatic coating machine, 2...Object to be coated, 1
a...High voltage application electrode, 3...High voltage cable, 4...High voltage generator, 5...
...Primary side power supply, 6...High voltage interlock contact, 7...High voltage current detector, 8...
...High voltage interlock circuit, 9...Paint hose, 10...Paint on-off valve.

Claims (1)

[Claims] 1. In an electrostatic coating method for metallic paint, the metallic paint is simultaneously atomized and charged by a high-voltage electrode, and a high voltage is applied to the opposite potential to the metallic paint to apply the metallic paint to the object to be coated. The metal pigments contained in the supplied metallic paint are connected in a chain, so that a current flowing from the high-voltage electrode toward the ground part of the paint supply source is detected, and by detecting the current, a high voltage is applied to the high-voltage electrode. An electrostatic coating method for metallic paint, characterized in that after voltage application is interrupted and the electrical conductivity of the metallic paint disappears, high voltage application to the high voltage electrode is automatically restarted to continue applying the paint.