JPS61114773A - Method for electrostatic painting of low conductivity parts - Google Patents

Abstract

PURPOSE:To perform uniform painting all over an article to be painted with high efficiency, by guiding heated air charged to polarity opposite to that of a paint across the article to be painted from bellow to above and spraying the charged paint to said article to be painted in this state. CONSTITUTION:The emitting port 4 of a duct 5 is directed to the lower part of a low conductivity article 3 to be painted such as a resin and, because air heated by a heater 7 and charged with a positive ion being charge opposite to that of a paint by a charging means 8 has specific gravity smaller than that of atmospheric air, the charged air rises along the surface of the article 3 to be painted to cover the same. When the paint is emitted from a spray gun 1 in a sprayed form in this state, the negatively charged paint is attracted to the article 3 to be painted by the positive ion covering the surface thereof to be surely adsorbed by the surface of the article 3 to be painted.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an electrostatic coating method for seven external conductive parts, which enables a coating film to be uniformly applied to M conductive parts such as resin.

(Conventional technology) In order to apply electrostatic coating to difficult-to-conduct parts such as resin and glass,
Conventionally, paint is charged with a positive or negative charge, while the surface to which this paint is applied is electrically conductive. ! I! There is a method of applying the paint to the object to be coated from the back side under a state in which the object is charged with an electric charge opposite to that charged on the paint, or as shown in Fig. 2, there is a method of applying the paint to the object to be coated. The paint applied from the gun 1 is charged with a negative charge by the high-pressure generator 2, while
The back side of the flT1 conductive object 3 to which this paint is applied is supported by a grounded conductive electrode 10 on a support 9, and the electric charge accumulated on the object 3 is transferred to the ground wire 11. There is a method in which the paint is applied to the object 3 under a condition where the paint is released.

(Problems to be Solved by the Invention) However, in the conventional painting method described above, there is a problem in that the concentration of electric charge at the edges causes paint to flow, increasing the defective rate of the product. Ta.

The present invention has focused on the problems of the prior art described above, and has an object to make it possible to uniformly apply a paint over the entire object to be coated with high application efficiency.

(Means for Solving the Problems) In order to achieve the above object, the present invention provides an object to be coated made of a poorly conductive material and a paint applied to the surface of the object to be painted. In the method, the paint is charged with a positive or negative charge, while the air blown towards the object to be coated is heated and charged with a charge opposite to that of the paint, and after heating and charging. The paint is applied to the object to be coated while air is guided along the surface of the object to be coated from the bottom to the top of the object. This is an electrostatic coating method for parts.

(Function) The high-temperature air charged with the opposite charge to the paint is blown onto the bottom of the object to be coated, and then rises to cover the surface of the object due to the difference in specific gravity with the ambient air. By spraying the charged paint under this condition, the paint can be uniformly adhered to the object to be coated with high coating efficiency.

(Example) Hereinafter, the present invention will be explained based on the drawings. FIG. 1 shows a state in which an object to be coated is coated by the electrostatic coating method of the present invention (this is a gi plane view).

The paint is discharged in the form of a spray from a spray gun 1, and a negative charge is applied by, for example, a high-pressure generator 2 for generating a negative voltage.

The object 3 to be coated, to which the paint charged in this manner is applied, is supported by a support 4 on the back side thereof. At one end of the duct 5, which has a discharge port 5a for discharging air toward the object 3 to be coated, a blowing means 6 such as a fan or a blower is attached to the other end.

Further, a heater 7 is installed in the duct 5 to heat the air passing through the duct 5, and a charging means 8 is provided for ionizing and charging the air heated by the heater 7.

As the charging means 8, there is one which utilizes a gas discharge phenomenon such as corona discharge, as disclosed in Japanese Patent Laid-Open No. 58-79°568. In case of corona discharge,
When a high DC voltage is applied to the needle-flat electric bridge provided in the duct 5 and the elephant 1 electrode is made positive, negative ions generated as a result of ionization of air molecules accumulate near the needle electrode where the electric field is strong. Positive ions under a weak electric field are discharged toward the object 3 from the discharge port 5a by the air flow. Incidentally, when utilizing the induction charging phenomenon, a polar plate is used inside the duct 5.

The discharge port 4 of the duct 5 is directed toward the lower part of the object 3 to be coated, and the air heated by the heater 7 and charged by the charging means 8 to positive ions, which have the opposite charge to the paint, is higher than the air in the atmosphere. Since the specific gravity is small, it rises along the surface of the object 3 to be coated and covers the surface of the object 3 to be coated. In this state, when the paint is discharged from the gun 1 in the form of a spray, the negatively charged paint is attracted by the positive ion air that covers the surface of the object 3, ensuring that it is coated. It is adsorbed to the surface of the coating material 3. Note that when the paint is to be positively charged, the air blown onto the object 3 to be coated may be negatively charged.

Next, the effect will be explained. Electrostatic painting usually involves applying a negative electric charge to the paint that has been atomized by a spray gun, and guides the air, which has been charged to the opposite charge to the paint, to the outer surface of the object to be coated 3. By doing so, the paint is drawn around the object to be coated by electrostatic attraction and is applied to the object with high paint efficiency.

(Effects of the Invention) As described above, according to the present invention, the paint is charged with a positive or negative charge, while the air blown toward the 'fi painted object is heated, and the air opposite to the paint is heated. The paint is applied to the object to be coated under a condition in which the heated and charged air is guided along the surface of the object to be coated from the bottom to the top of the object to be coated. 15, the paint can be applied uniformly with high coating efficiency even to externally conductive objects.

4. Drawing 1! ! 'i, 1! Explanation: FIG. 1 is a sectional view showing an electrostatic coating method according to an embodiment of the present invention, and FIG. 2 is a sectional view showing a conventional electrostatic coating method.

DESCRIPTION OF SYMBOLS 1... Spray gun, 2... High pressure generator, 3... To be coated, 6... Air blowing means, 7... Heater, 8... Charging means.

Claims (1)

[Claims] In a method of painting by applying an electric charge to an object to be coated made of a poorly conductive object and a paint applied to the surface of the object, the paint is charged with a positive or negative charge, while the object to be coated is charged with a positive or negative charge. The air blown toward is heated and charged to an opposite charge to the paint, and the heated and charged air is directed from the bottom of the object to the top onto the surface of the object to be coated. 1. A method for electrostatic coating of poorly conductive parts, characterized in that the paint is applied to the object under a condition of being guided along the same direction.