JP2001276674A - Electrostatic powder coating apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To conduct coating without causing coating defects such as blisters and ruggednesses even though a powder paint containing the paint grains coarsened due to blocking is used. SOLUTION: The powder paint whirled up from a powder paint storage tank (10) formed at the bottom of a coating booth (2) is charged, suspended and electrostatically deposited on a work(W) of reverse polarity to be coated. In this case, an ultrasonic vibrating screen (13) is arranged between the tank (10) and work(W) to sort out the paint grains having a diameter larger than the maximum permissible diameter suitable for coating.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic powder coating apparatus which flies powder coating particles in an electrostatic field formed in a coating chamber and attaches the particles to an object having the opposite polarity.

[0002]

2. Description of the Related Art Electrostatic powder coating is a coating in which a negatively charged powder coating is electrostatically applied to a grounded object, and the powder coating is sprayed onto the object using a spray gun. Electrospray coating and electrolytic fluidized immersion coating in which powder coating is sowed and adhered to an object to be coated are known.

Meanwhile, the latter type of the electrostatic powder coating apparatus for performing the electrolytic fluidized immersion coating is configured to blow powder paint upward by blowing air upward from a tank bottom of a powder paint storage tank formed at the bottom of a coating chamber. Fluidized, further flours up the powder coating by the air current formed in the coating chamber, and the electrostatic force generated between the grounded coating object and the negative electrode arranged opposite to the coating surface, causes the coating material to flow It is designed to be electrostatically applied.

According to this method, it is not necessary to preheat the object to be coated, and the paint does not adhere more than necessary due to electrostatic repulsion, so that a coating film having a uniform thickness is formed, and it is easy to collect unadhered paint particles. This has the advantage that the amount of paint used can be saved.

[0005] By the way, in automobile coating and the like that require high coating quality, a fine coating film is formed, and the particle size is 2
It is said that the coating is preferably performed using a powder coating having a sharp particle size distribution of 0 to 50 μm. And

[0006]

The electrostatic force that causes paint particles to adhere to the surface of an object to be coated is inversely proportional to the particle size, and the smaller the particle size is, the more the fine-grained and beautiful coating film is formed. It is said that it is preferable to apply a powder coating material having a sharp particle size distribution having a particle size of 20 to 50 μm in an automobile coating or the like that requires high coating quality.

[0007] However, even if the powder paint having such a particle size distribution is used, the paint control is not sufficient, or the powder paint storage tank is heated to a high temperature between the end of painting on the previous day and the start of painting on the next day. When the powder coating material is exposed to humid air or absorbs moisture, there is a problem that the coating particles are blocked and become coarse, causing coating defects such as bumps and rough skin.

[0008] In addition, since such a coating failure can be found only after the powder coating is electrostatically applied and then baked, all of the coating that has been electrostatically applied and carried into the baking furnace during that time. There is a possibility that defective coating may occur on the object to be coated.

Further, when such a coating failure occurs, the powder paint is discarded and replaced with a new powder paint at present, and there is a problem that the paint is wasteful and the cost increases. there were.

[0010] Therefore, the present invention is to make it possible to perform coating without causing coating defects such as bumps and rough skin, even when using a powder coating containing coating particles which are coarsened due to blocking. Is a technical issue.

[0011]

SUMMARY OF THE INVENTION To solve this problem, the present invention provides a method of floating a powder paint, which is soaked from a powder paint storage tank formed at the bottom of a coating chamber, in an electrically charged state, so as to have an opposite polarity. In an electrostatic powder coating apparatus that electrostatically coats an object to be coated, an ultrasonic vibrating sieve that sorts paint particles having a diameter larger than a maximum allowable particle diameter is provided between the powder paint storage tank and the object to be coated. It is characterized by being arranged.

According to the present invention, an ultrasonic vibrating sieve for selecting paint particles having a diameter larger than the maximum allowable particle size suitable for coating is disposed between the powder paint storage tank and the object to be coated. Coating particles that have become coarse due to blocking are captured, and only coating particles having a relatively small diameter pass through the ultrasonic vibrating sieve and are electrostatically applied to the substrate. Therefore, a beautiful coating film is formed without causing coating defects such as bumps and rough skin due to the application of the coarsened coating particles.

The large-diameter paint particles captured by the ultrasonic vibrating sieve are redispersed into individual paint particles by the impact of ultrasonic vibration, and the small-diameter paint particles smaller than the maximum allowable particle size suitable for coating. As a result, it falls into the powder paint storage tank.
Therefore, there is no need to discard the powder coating containing the coating particles that have become coarse due to blocking, or replace the powder coating with a new powder coating, and it is possible to use the powder coating to the end without waste.

[0014]

Embodiments of the present invention will be specifically described below with reference to the drawings. FIG. 1 is a schematic configuration diagram showing an electrostatic powder coating apparatus according to the present invention, and FIG. 2 is an explanatory diagram showing an operation.

In the electrostatic powder coating apparatus 1 of this embodiment, air is introduced into the coating chamber 2 through a ceramic porous plate 4 below a chamber 3 in which a coating chamber 2 for coating an object W is formed. Is formed.

The workpiece W is suspended from the conveyor 7 disposed outside the chamber 3 through the slit 6 formed in the ceiling of the chamber 3 into the coating chamber 2 by the hanger 8 and the conveyor 7 and the hanger 8. Connected to earth through Also, on both the left and right sides along the transport direction,
Electrodes 9 to which a high voltage of −60 to −90 kV is applied are arranged, and an electrostatic field E is formed between the electrodes 9 and 9 and the article W to be coated.

At the bottom of the coating chamber 2, the porous plate 4
A powder paint storage tank 10 having a bottom plate is formed,
The air supplied from 1 to the positive pressure chamber 5 is blown up through the porous plate 4, and the powder paint in the storage tank 10 is fluidized.

In the coating chamber 2, ejectors 12 which form a convection for sowing the powder coating material toward an electrostatic field E formed between the electrodes 9, 9 and the workpiece W are arranged vertically. They are arranged in two stages, each of which blows air upward.

Further, an ultrasonic vibrating sieve 13 for selecting paint particles having a diameter larger than the maximum allowable particle size is disposed between the powder paint storage tank 10 and the workpiece W. The sieve 13 is provided with a filter screen 14 so as to partition the coating chamber 2 up and down between the upper and lower ejectors 12... And an ultrasonic wave for applying ultrasonic vibration of about 36 kHz to the filter screen 14. A vibrator 15 is attached.

The filter screen 14 is exchangeably mounted so that it can be replaced with a different mesh according to the maximum allowable particle size that varies depending on the type of the object to be coated W and the purpose of coating. For example, the maximum allowable particle size is reduced to 50 μm. When setting, a 300 mesh mesh may be used, and when it is necessary to set the maximum allowable particle size to 20 μm as in the case of thin film coating, a 635 mesh mesh may be used.

The above is an example of the present invention, and the operation will be described next with reference to FIG. First, when air is started from the air supply pipe 11 to the positive pressure chamber 5, the air is supplied to the porous plate 4.
Through the bottom of the powder paint storage tank 10
The powder coating in the tank 10 is in a fluidized state.

Next, when the filter screen 14 is ultrasonically vibrated by the ultrasonic vibrator 15 and air is blown out from the ejectors 12, a convection is formed in the coating chamber 2, and the fluidized state in the storage tank 10 is obtained. Powder paint soars.

When a high voltage is applied to the electrodes 9 and 9 to carry in the article to be coated W, air is ionized by the electrostatic field E formed between the electrode 9 and the article to be coated W, and the paint particles soared up Is charged in the negative electrode, floats in the coating chamber 2, and is electrostatically applied to the grounded workpiece W.

At this time, since the paint particles applied to the article to be coated W have passed through the ultrasonic vibrating sieve 13, there are only paint particles smaller than the maximum allowable particle size. Does not occur.

That is, even if the paint particles that have become coarse due to blocking are lifted from the powder paint storage tank 10, they are captured by the ultrasonic vibrating sieve 13, so that they pass through the sieve 13 and are applied to the workpiece W. Will not be worn.

The large-diameter paint particles captured by the ultrasonic vibrating sieve 13 are re-dispersed into individual paint particles by the impact of ultrasonic vibration via the filter screen 14, and the maximum allowable particle size suitable for coating is obtained. The particles become small diameter paint particles having a diameter equal to or less than the diameter and fall into the powder paint storage tank 10.

Therefore, there is no need to discard the powder coating containing the coating particles that have become coarse due to blocking, or replace the powder coating with a new powder coating, and it is possible to use the powder coating to the end without waste.

Then, the supply of air to the positive pressure chamber 5 and the ejectors 12 is stopped, and the high voltage applied to the electrodes 9, 9 is turned off. The paint particles floating inside fall by gravity.

At this time, the paint particles that have risen to the upper part of the ultrasonic vibrating sieve 13 are paint particles having a small diameter smaller than the maximum allowable particle size that passes through the ultrasonic vibrating sieve 13, and thus pass through the ultrasonic vibrating sieve 13 again. Then, it falls to the powder paint storage tank 10.

The paint particles are applied to the filter screen 14.
Even if the filter screen 14 is piled up or caught on the mesh, the filter screen 14 is vibrated by the ultrasonic waves, and thus the filter screen 14 is shaken off by the vibration and can be reliably recovered.

[0031]

As described above, according to the present invention, even if the powder coating contains blocking and coarsened coating particles, the coating particles are captured by the ultrasonic vibrating sieve, Since it is not applied to the object to be coated, it does not cause coating defects such as bumps and rough skin, so there is no need to dispose or replace such powder coating, and further, it is captured by the ultrasonic vibration sieve Since the large paint particles are redispersed by the impact of the ultrasonic vibration, there is an excellent effect that the coarse paint particles can be used without waste.

[Brief description of the drawings]

FIG. 1 is a schematic explanatory view showing an example of a powder electrostatic coating apparatus according to the present invention.

FIG. 2 is an explanatory diagram illustrating the operation.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Electrostatic powder coating device 2 ... Coating room W ... Coating object 10 ... Powder paint storage tank 13 ... Ultrasonic vibration sieve

Claims (1)

[Claims] 1. A powder paint blown up from a powder paint storage tank (10) formed at the bottom of a coating chamber (2) is floated in a charged state and electrostatically applied to an object (W) of opposite polarity. In the electrostatic powder coating apparatus to be applied, ultrasonic vibration for selecting paint particles having a diameter larger than the maximum allowable particle size suitable for coating between the powder paint storage tank (10) and the object to be coated (W). An electrostatic powder coating device comprising a sieve (13).