JP2000343002A - Electrostatic coating device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To improve coating efficiency by incorporating an electrifying part for charging an atomized particle from an atomizer and plural ring like electrode and uniformizing potential gradient from the electrifying part to an outlet of an electric field transporting device. SOLUTION: A coating material 2 housed in a tightly closed vessel 1 is sucked by a two fluid nozzle 3 having a sucking function to be atomized and the atomized particle is sprayed on a collision plate 4. At this time, an unapplied coating material particle group 5 having relatively small particle size enters to a conduit pipe 6 with the atomized air from the two fluid nozzle and is introduced into the electric field transporting device 7. An acicular electrode 8 of the electrifying part is arranged at the 1st stage of the electric field transporting device 7, the acicular electrode 8 and the ring like electrode 9 of the next stage are connected with a high resistor 10 to cause voltage drop by the current flowing the circuit and as a result, the potential gradient form the acicular electrode 8 to the electric field transporting device 7 is uniformalized.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic coating apparatus capable of transporting atomized paint particles to an object to be coated and applying the same efficiently.

[0002]

2. Description of the Related Art
The electrostatic coating device charges the atomized particles with an applied electrode and applies the charged paint particles to the object by the action of an electric field formed between the applied electrode and the grounded object. Met.

[0003] In addition, for the application electrode, a needle-shaped electrode is used for an air atomizing or airless atomizing device, for example, and a bell or a disk is applied as it is for a rotary bell or a rotating disk type atomizing device. Used as an electrode.

The electric field formed between the applied electrode and the object to be coated is generally called an uneven electric field. The potential gradient near the applied electrode is large, and the electric field strength, that is, the degree of change in the space potential depending on the distance is small. Although large, the potential gradient is generally small near the object to be coated.

[0005] However, these conventional electrostatic coating machines have the following disadvantages.

In the electrostatic coating apparatus, it is necessary to apply the atomized paint particles to the object as much as possible, that is, to enhance the electrostatic effect in order to improve the coating efficiency. Voltages as high as -120 kV were commonly used. This applied voltage is directly applied to the applied electrode, and furthermore, since the applied electrode is used in a bare state, there is a problem that the safety of an emergency worker is ensured.

[0007] Furthermore, the charged paint particles are applied while moving to the object to be coated by an electric field formed between the application electrode and the object to be grounded, because the electric field is an uneven electric field. Particles that easily adhere to the object to be coated, that is, particles that reach the object while moving in a region having a relatively small particle size and high electric field strength, and particles that are difficult to apply, that is, particles that have a relatively large particle size Some particles tend to deviate from the working range of
In the conventional electrostatic coating apparatus, the mechanical kinetic energy of the atomized particles is directed toward the object to be coated as the number of relatively large particles increases, and also due to the effect of the atomization mechanism. There is a problem in that the coating efficiency is reduced with an increase in the number of particles that do not exist.

[0008] An object of the present invention is to provide a high voltage application electrode in a state where the electrode is not exposed, and a relatively small particle and a relatively large particle are easily applied to an object to be coated. An object of the present invention is to provide an electrostatic coating device capable of obtaining a deposition efficiency.

[0009]

Means for Solving the Problems The inventors of the present invention have conducted intensive studies in order to achieve the above object, and as a result, have incorporated a charging portion for charging the atomized particles from the atomizing device with electric charges and a plurality of ring-shaped electrodes. However, the inventors have found that the above object can be achieved by an electrostatic coating apparatus having an electric field transport device capable of making the potential gradient from the charging section to the outlet of the electric field transport device uniform, and have completed the present invention. .

That is, according to the present invention, an atomizing device for atomizing a liquid material, a charging unit for charging the atomized particles of the liquid material with electric charge, and the charged atomized particles are conveyed toward an outlet of the electric field conveying device. An electric field transport device including a plurality of ring-shaped electrodes therein, and the atomizing device and the electric field transport device are connected so that atomized particles from the atomizing device can move into the electric field transport device. And the plurality of ring-shaped electrodes are capable of setting the potential of each ring-shaped electrode so that the potential gradient from the charging section of the electric field transport device to the last-stage ring-shaped electrode can be made uniform. The present invention is to provide an electrostatic coating device that performs the following.

Further, according to the present invention, the potential of each ring-shaped electrode is set by using the above-mentioned electrostatic coating apparatus and so as to make the potential gradient from the charging section of the electric field transfer device to the last-stage ring-shaped electrode uniform. Another object of the present invention is to provide an electrostatic coating method characterized in that electrostatic spraying is performed by bringing an ejection port of atomized particles in the electric field transport device close to an object to be coated.

[0012]

DETAILED DESCRIPTION OF THE INVENTION An electrostatic coating apparatus according to the present invention includes an atomizing device and an electric field transport device, and communicates so that particles atomized by the atomizing device can move into the electric field transport device. The atomized particles that have moved into the electric field transport device travel toward the outlet of the electric field transport device and are applied to an object to be coated. The atomizing device and the electric field transport device may be directly connected, or may be connected via a conduit.

[0013] The electric field transfer device has at least an inner portion made of an insulator. The electric field transfer device includes a charging unit for charging the atomized particles of the liquid material with electric charge and a charged atomized particle of the electric field transfer device. A ring-shaped electrode that conveys toward the outlet is built in. Since the charging section is built in the first stage of the electric field transport device, the charging section, which is a high-voltage part, is not directly exposed to the outside, and the electric field formed by the grounded coating object is in the final stage. And a ring-shaped electrode.

As the charging section, a needle electrode (corona discharge electrode) known per se in a conventional electrostatic coating machine can be suitably used. The voltage of the applied electrode of the charging section is usually about −25 to −90 kV, preferably −
It is in the range of about 30 kV to -60 kV. Further, the voltage of the ring-shaped electrode at the last stage is usually in the range of about -5 to -20 kV, preferably in the range of about -8 to -15 kV.

The plurality of ring-shaped electrodes are set so that the potential gradient from the charging section to the outlet of the electric-field transport device can be made uniform, and the potential of the ring-shaped electrode is usually close to the outlet of the electric-field transport device. The lower the potential is set. Since the potential of the ring-shaped electrode closest to the outlet of the electric field transport device has a voltage drop, electric shock due to high voltage can be prevented, and the safety of the worker can be ensured.

The shape of the ring electrode may be a ring shape, and may be a circular or polygonal shape. Also, the ring may be broken and have ends. The number of ring-shaped electrodes is suitably two or more, preferably 3 to 10, and the distance between the ring-shaped electrodes is preferably about 3 to 10 cm. In addition, the ring-shaped electrode is easily embedded in the inner wall of the electric-field transport device and can be easily cleaned.

In the conventional electrostatic coating machine, the potential gradient is large near the application electrode and the degree of change in the space potential depending on the electric field strength, that is, the distance is large. However, the potential gradient is small near the object to be coated. There is a problem such as lowering.

In the present invention, the non-uniformity of the potential gradient from the applied electrode, which is a charging unit, to the outlet of the electric field transport device is made uniform by the ring-shaped electrode, and the potential of the ring-shaped electrode near the applied electrode is made uniform. Is set high, and the potential of each ring-shaped electrode up to the ring-shaped electrode near the outlet of the electric field transport device is set so that the potential gradient is uniform, that is, close to a uniform electric field.

In the present invention, "uniform" means not only uniformity but also approaching a uniform state.

The voltage of each ring-shaped electrode is sequentially reduced in the direction of the exit of the electric field transport device by, for example, connecting each ring-shaped electrode in series and interposing a high resistor between the ring-shaped electrodes. Can be.

In the present invention, the atomized and charged particles move in the electric field formed by the ring-shaped electrode, head toward the outlet of the electric field transport device, and squirt from the outlet to coat the object to be coated. Since there is no influence of external factors before the electric field transport device exits, nearly 100% of the atomized particles can be moved from the entrance to the exit of the electric field transport device. Further, at the time of coating, the coating efficiency can be improved by bringing the outlet portion of the electric field transport device and the object to be coated close to each other.

In the case of coating using the apparatus of the present invention, it is preferable that the distance between the application electrode of the charging section and the object to be coated is usually in the range of 10 to 30 cm.

[0023]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in more detail with reference to the drawings.

FIG. 1 shows a first embodiment of the electrostatic coating apparatus of the present invention.
It is explanatory drawing which shows Example of this. In FIG. 1, a paint 2 placed in a closed container 1 is atomized while being sucked up by a two-fluid nozzle 3 having a sucking function, and atomized particles are sprayed on a collision plate 4. The particles applied to the collision plate flow down and are collected as they are, and are sucked up again and atomized. At this time,
The relatively small paint particles 5 that have not been applied enter the conduit 6 together with the atomizing air of the two-fluid nozzle and are introduced into the electric field transport device 7. Here, three needle-shaped electrodes 8 arranged at the first stage of the electric field transport device are arranged concentrically at equal intervals with respect to the cylindrical electric field transport device made of an insulator, and have a high voltage (−30 kV). (Not shown) was applied. The paint particles passing through the needle-shaped electrode portion are charged by air ions generated by corona discharge generated near the needle-shaped electrode and become charged particles. The first-stage needle-shaped electrode 8 and the next-stage ring-shaped electrode 9 are connected by a high-resistance (50 MΩ) 10, and a voltage drop occurs due to a current flowing through the circuit. An electric field is formed between them, and the charged particles are transported to the ring-shaped electrode. Similarly, since the ring electrodes of each stage are connected by a high resistor, the charged particles are transported toward the ring electrode 11 of the final stage by the electric field formed between the ring electrodes. To go. Then, the charged particles are applied to the object to be coated by an electric field formed by the ring-shaped electrode 11 at the final stage and the object to be coated 12 placed. At this time, the voltage of the last-stage ring-shaped electrode 11 was set to -10 kV.

FIG. 2 shows a second embodiment of the electrostatic coating apparatus of the present invention.
It is explanatory drawing which shows Example of this. In FIG. 2, a closed container 1 is filled with a coating material 2 up to a predetermined liquid level, and an atomizing device using an ultrasonic vibrator 13 is built therein. Further, an air fan 14 for carrying out atomized particles is installed in the closed container, and creates an air flow for sending particles generated by the vibration of the ultrasonic vibrator to the electric field transport device.

The second embodiment shown in FIG.
As in the first embodiment shown in FIG. 2, the paint particles fed into the electric field transport device are charged by the needle-shaped electrodes 8 of the charging unit. In FIG. 2, the eight needle-shaped applied electrodes are concentric. The structure is such that the paint particles passing through the charging section can be more effectively charged at the same time, and the charging section and the transport section (the portion where the ring-shaped electrode is disposed) in the electric field transport device can be freely detached, The ease of cleaning and repair has been improved. Further, the ring-shaped electrode is manufactured so as to be embedded in the cylindrical inner wall of the electric field transfer device, so that the inside can be easily cleaned after use.

[0027]

According to the apparatus of the present invention, the charged paint particles smoothly move in the electric field transfer device in which the potential gradient is made uniform by the ring-shaped electrode, and are grounded to the ring-shaped electrode in the final stage. Since it is controlled by the action force of the electric field formed by the coated object, the coating particles can be applied to the object with high application efficiency.

The final stage of the ring-shaped electrode is placed inside the electric field transport device, and the cylindrical portion of the electric field transport device is brought close to the object to be coated at a short distance, so that the paint particles can be externally applied such as the wind speed of the booth. Since the paint particles can be applied almost without being affected by the cause of the inhibition, dustless coating becomes possible.

[Brief description of the drawings]

FIG. 1 is an explanatory view showing a first embodiment of an electrostatic coating apparatus according to the present invention.

FIG. 2 is an explanatory view showing a second embodiment of the electrostatic coating apparatus of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Closed container 2 ... Paint 3 ... Two-fluid nozzle 4 ... Impact plate 5 ... Paint particle group 6 ... Conduit 7 ... Electric field transfer device 8 ... Needle electrode (Corona electrode) 9 Next-stage ring-shaped electrode 10 High-resistance 11 Last-stage ring-shaped electrode 12 Coating object 13 Ultrasonic vibrator 14 Air fan

Claims (6)

[Claims] An atomizing device for atomizing a liquid material, a charging unit for charging the atomized particles of the liquid material with electric charges, and a plurality of rings for conveying the charged atomized particles toward an outlet of an electric field conveying device. An electric field carrier device having a built-in electrode, and the atomizing device and the electric field carrier device are connected so that atomized particles from the atomizer can move into the electric field carrier device, In addition, the plurality of ring-shaped electrodes can set the potential of each ring-shaped electrode so that the potential gradient from the charging section of the electric field transport device to the last-stage ring-shaped electrode can be made uniform. Painting equipment. 2. The electrostatic coating device according to claim 1, wherein the atomizing device and the electric field transport device are communicated via a conduit. 3. The electric field transport device is cylindrical in shape, and the charging section for charging the atomized particles with electric charges is a plurality of needle-shaped application electrodes arranged concentrically in a cylindrical container. 3. The electrostatic coating device according to 1 or 2. 4. A plurality of ring-shaped electrodes incorporated in the electric field transport device are arranged at substantially equal intervals from the charging section to the outlet of the atomized particles in the electric field transport device. The electrostatic coating device according to any one of the above. 5. The electrostatic coating apparatus according to claim 1, wherein the plurality of ring-shaped electrodes are connected by an electric resistor. 6. The potential setting of each ring-shaped electrode is performed using the electrostatic coating device according to claim 1, so that the potential gradient from the charging section of the electric-field transport device to the last-stage ring-shaped electrode can be made uniform. An electrostatic coating method, wherein an electrostatic coating is performed by bringing an ejection port of atomized particles in the electric field transport device close to an object to be coated.