JP2008119557A - External charging type electrostatic coating gun equipped with external electrode - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an external charging type electrostatic coating gun with an external electrode which eliminates the danger and discomfort through discharging to fingers of operators due to the generation of coating attachment at the surface of an external electrode or the body side of an external charging type electrostatic coating gun. <P>SOLUTION: In the external charging type electrostatic coating gun equipped with the charged electrode extended ahead at the outside of the atomization area of the electrostatic gun, which disposes at the center of the insulation electrostatic gun a nozzle to jet the coating at earth electric potential, an earth electrode which is comprised of a conductive material and which is connected with the earth electric potential is installed at the root surrounding of the external electrode body equipped with the charged electrode of the conductive material exposed to the distal end portion, in which the connection conductor is covered with the insulator. The earth electrode is connected with the earth member of the gun body through the conductive material. The earth member of the body includes the coating to be sent to the coating feeding path. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

The present invention relates to an externally charged electrostatic coating gun particularly suitable for electrostatic coating of paint having a low resistance value such as water-based paint and metallic paint.

Electrostatic coating is widely adopted as a coating method that charges high-voltage static electricity to the sprayed paint particles, improves the coating efficiency by the electric field formed on the object to be coated from the electrostatic spray gun, and makes effective use of resources. ing. Paints used for such electrostatic coating are roughly classified into solvent-based paints with a large electrical resistance value and water-based or metallic paints with a high electrical resistance value, such as water-based or metallic paints. The painting method and equipment are very different.

Among them, solvent-based paints containing volatile organic compounds have been required to be reduced in use due to environmental problems in recent years, and a shift to water-based paints has been required. However, when charging the sprayed paint directly to increase the electrostatic coating effect, it is most efficient to provide a charged electrode at the spray center of the paint. The charged high voltage flows through the paint to the grounded paint supply source, and the electrostatic effect cannot be obtained. In addition, the high voltage flows through the paint supply system, and there is a risk of fire due to the occurrence of sparks due to the large charge amount. .

For this reason, a method / apparatus is used in which the paint supply system is insulated from the ground side and electrostatic coating is performed while maintaining a high voltage. However, due to the enormous amount of charge in the paint supply system, an increase in danger is unavoidable, and in order to increase the industrial efficiency by continuously performing the painting operation, the paint as shown in JP-A-6-198228 It is necessary to use a supply device, and it is necessary to introduce a large-scale device, which also poses a burden on usage and maintenance.

Due to these problems, electrostatic coating of water-based paints and metallic paints has not been popularized, causing delays in environmental measures. On the other hand, the paint particles that are not directly charged to the paint but charged through the ionized area from the electrode installed outside the spray area are charged and placed on the lines of electric force (electric field) toward the object to be painted. There is known an electrostatic coating machine using an external electrode to be applied to the surface.

As one of them, as an apparatus that is integrated with and integrated with a spray gun, Japanese Patent No. 2770079 and an electrostatic coating apparatus such as JP-A-7-213958 have been proposed.
An externally charged electrode type electrostatic paint spray gun applies a high voltage to the external electrode installed at a position outside the spray paint area by the spray gun, thereby discharging the ground potential side of the object to be painted, etc. And is charged to the fine particles of the paint passing therethrough, and is applied to the electric field formed toward the object to be coated to promote the coating.

In this case, in order to increase the charging effect on the paint by the charged electrode placed outside the spray area of the paint, it is desirable to provide the position of the charge electrode as close as possible to the atomization. However, if the charged electrode is brought closer to the atomization position, that is, the nozzle outlet where the paint is ejected, it will be closer to the finger of the operator who holds and operates the electrostatic gun, and there is a risk that high voltage will be discharged to the operator's finger Leads to an increase.

The external charged electrode is generally charged with a high voltage of about −30 kV to −70 kV, and there is a large potential difference between the nozzle outlet of the paint on the ground electrode side, and the paint particles immediately after being sprayed In this case, charge between the charged electrode and the counter electrode is induced. In addition to the periphery of the charging electrode, the electrostatic gun body, spraying device, and the like are dielectrics formed of an insulating material, so that the surface is charged with negative charges. For this reason, some paint particles which are sprayed and floated adhere to the periphery of the externally charged electrode, and the attached paint having a low electrical resistance value has conductivity and further approaches the finger of the operator. Therefore, it is necessary to prevent such paint adhesion.

Techniques for preventing the adhesion of paint to a spraying device such as an air cap formed of an insulating material that is a dielectric in the external charging electrode method are disclosed in JP-A Nos. 9-136047 and 2006-247556. It is configured so that the surrounding insulator is charged to the same polarity as the ground electrode by arranging an electrode having a grounding function at a position surrounding the periphery around the paint outlet, and the paint adheres to the spraying device. It is preventing.

Japanese Patent Laid-Open No. 9-136047 JP 2006-247556 A

As described above, in the case of the external charging type, since a charged electrode must be disposed close to the atomizing device in order to obtain a charging effect, the paint is likely to adhere to the periphery of the external electrode. As a result, a high voltage leaks to the operator holding the electric gun, causing discomfort and anxiety such as numbness in the fingers. Although the improvement can be achieved by separating the electrode positions, other problems such as a decrease in electrostatic effect and a decrease in operability caused by the electrode body extending toward the tip end will occur.

The present invention eliminates the unpleasant sensation by preventing the danger of discharging to the fingers of the operator without causing the electrostatic effect and operability deterioration, and the external electrode surface of the externally charged electrostatic gun or the electrostatic gun body It is an object to prevent the adhesion of the paint to the side and facilitate maintenance of the electrostatic gun.

In order to solve the above problems, the present invention has a nozzle that ejects paint placed at a ground potential at the center of an insulating electrostatic gun body, and a charged electrode that extends forward outside the atomization region of the electrostatic gun. The externally charged electrostatic coating gun provided is composed of a fuselage whose connection conductor is covered with an insulator, and is made of a conductive material around the base of the fuselage of the external electrode body with the tip electrode exposed at the tip, and is grounded. A grounding ring connected to the potential is provided.

In addition, the grounding ring is provided with a sharp pointed part on the part, so that discharge from the tip electrode is concentrated, enabling stable discharge, and connecting to the grounding member of the gun body with a conductive material And

According to the above configuration, the high voltage charged on the externally charged electrode arranged outside the atomization region of the electrostatic gun forms an electric field toward the object to be coated installed on the counter electrode, and is electrically connected to the ground potential. The sprayed paint particles are discharged to form an ionized sphere region and charge the atomized paint particles.
Furthermore, since a high voltage is discharged to the grounding ring that is arranged at the base of the external electrode and serves as a ground electrode, the high voltage is not discharged to the finger of the operator gripping at the rear part.

Therefore, the operator can work with peace of mind without feeling the danger of electric discharge. In addition, the grounding ring placed at the ground potential keeps the surface of the external electrode body, gun body, spraying device, etc. formed of an insulating material as a dielectric around the ground potential to prevent adhesion of paint particles. Reduce the burden of maintenance work.

Since the mounting position of the grounding ring is fixed, the distance between the tip electrode and the ground electrode that is the counter electrode is stabilized, so that it is not affected by the state of the spray paint particles, and the ionization region is formed by the discharge of the tip electrode. It is stable and the charge on the paint particles can be kept constant. In particular, by forming a pointed portion where discharge concentrates on a part of the grounding ring, it is possible to achieve further stabilization and improve coating quality.

Embodiments of the present invention will be described below with reference to the drawings.
Reference numeral 1 denotes an externally charged electrostatic spray gun according to this embodiment, and the spray gun is a hand-held example. The gun body 1 is formed of an insulating material, is gripped with a handle 2 at the rear, and is operated with a trigger 3. The barrel part 4 extending forward controls the paint sprayed from the atomizing device 5 provided at the tip, and controls the input / output of the low voltage power source housed in the barrel part 4 and supplied to the high voltage generator 6, The high voltage charged in the tip electrode 71 of the external electrode 7 provided outside the spray gun 1 is controlled.

In the case of this embodiment, the atomizing device 5 shows an air spray gun for atomizing paint with compressed air, an air cap 51 is arranged around the paint nozzle 52, and a desired spray pattern is shown in the air cap. The object to be coated is formed by 51. These structures employ a well-known spray gun structure, but are formed of an electrically insulating material including the barrel portion 4 in electrostatic coating. In the present invention, in the case of a spray gun using a water-based or highly conductive paint and having an externally charged electrode, since the paint path is connected to the ground side potential, the needle valve 53 in the paint nozzle 52 is metallic, and the rear part It is electrically connected to the handle 2 located at the position. The handle is conductive like a normal electrostatic spray gun. In this embodiment, a semiconductive resin is used so that the ground potential is obtained when the operator operates the hand.

The high voltage generator 6 includes a low frequency transformer, a Cockcroft Walton multi-stage voltage doubler rectifier circuit, a cartridge in which a high resistance for protection is cast with an insulating resin, and is formed of an insulating material. It is attached to.

FIG. 2 is a partial cross-sectional view of the distal end portion of the gun body 1 when viewed from above in FIG. In the barrel part 4 of the gun body 1, an electrode connection part 13 of an external electrode is provided on the outer rear side of the atomization device 5 provided at the tip so that a high voltage from the high voltage generator 6 is connected. The other end of the conducting wire 12 is exposed inside the electrode connecting portion 13 made of an insulating material as a connection terminal 14.

The external electrode 7 attached to the electrode connecting portion 13 is formed entirely of an insulating material by providing a rod-like body 70 with the tip electrode 71 exposed at the tip and a detachable portion 72 at the rear end. The connection terminal 73 is exposed from one end of the detachable portion 72, and the connection terminal 73 and the tip electrode 71 are connected by a conducting wire 74. When the external electrode 7 is attached to the electrode connection part 13 of the barrel part 4, the connection terminal 73 and the connection terminal 14 on the barrel part 4 side come into contact with each other and are electrically connected. In the present embodiment, the connection terminal 73 has a spring configuration for reliable connection, but the connection terminal 14 side may be formed by a spring.

A circular grounding ring 75 is mounted on the outer periphery of the base portion of the body 70. In the figure, a ring-shaped part having a rectangular cross section is fixed in a configuration that fits into a tapered portion 76 that connects the detachable portion 72 and the body, but the structure is not limited to this, and the surface of the base portion of the body It may be possible to coat the substrate with a conductive material or to attach an annular ring. This ground ring is connected by a connection line 77 to a conductive member placed at the ground potential of the gun body. That is, as shown in FIG. 2, an appropriate electrical connection may be configured by taking the metal trigger 3 connected to the ground potential as an example.

Similarly, the inside of the paint passage inside the gun body 1 is maintained at the ground potential, and the above-described metallic needle valve 53 is also at the same ground potential, so that the connection terminal is exposed in the paint passage or slides on the needle valve 53. You may arrange | position the connecting terminal to be made.

As can be understood from the figure, when the gun body is gripped, the finger is at the most distal side is the finger that operates the trigger 3, and the ground ring 75 is sufficiently forward of the finger on the trigger 3, The high voltage from the tip electrode 71 is discharged to the ground ring 75 before reaching the finger. Therefore, no dangerous discharge occurs to the operator. As shown in the embodiment shown in FIG. 3, by providing a pointed portion 78 protruding at the front portion of the ground ring 75, the discharge can be stabilized at a certain position.

When the electrostatic gun having such a structure is used, the paint sprayed from the paint nozzle 52 is atomized by the air sprayed from the air cap 51 to form a desired spray pattern (not shown). No). At the same time, the tip electrode 71 is charged, and the high voltage is discharged toward the paint outlet of the counter electrode and the grounding ring 75, and is discharged toward the object to be coated of the counter electrode to form an electric field. A strong ionization area is formed around the atomization area by the discharge to the paint side placed in the close position, and the paint particles that are sprayed toward the object to be coated by the atomizing air are charged. The negative charge is charged and attracted with the positive charge induced on the surface of the object to be coated, thereby promoting the coating.

On the other hand, the paint particles immediately after spraying float in a state in which the charge induced on the plus side by the earth electrode (plus) on the nozzle side is charged, but the surface of the external electrode or the surface of the gun body induced on the plus side by the ground ring 75. Is repelled and adhesion is prevented.

Further, in the spray gun, the spraying conditions change depending on the coating specifications, and the discharge state from the tip electrode 71 changes depending on the paint conditions to be ejected. For this reason, a change occurs in the charging effect and the like, and the electrostatic coating effect, that is, the coating efficiency varies, and stable performance cannot be obtained. In the embodiment of the ground ring 75 of FIG. 3, a sharp tip 78 is formed in the front to make it easy to receive the electric field concentration stably. According to this configuration, since the distance between the tip electrode and the ground ring is constant and discharge is performed at an external position that is not affected by spraying, it is possible to always maintain stable discharge and form an ionization region. For this reason, a stable electrostatic effect can be obtained and the coating quality can be stabilized.

FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
FIG. 2 is a partial cross-sectional view showing a mounting portion of an external electrode provided with a ground ring.
FIG. 3 is an external view of a mounting portion of an external electrode showing another embodiment of the ground ring.

Explanation of symbols

1. Electrostatic gun main body 2, handle 3, trigger 4, barrel portion 5, nebulizer 6, high voltage generator 7, external electrode 13, electrode body attaching / detaching portion 71, tip electrode 72, attaching / detaching portion 73, connection terminal 75, grounding ring 77, connecting wire 78, tip

Claims (3)

A spray nozzle is provided at the tip of an electrostatic gun body made of an insulating material, and a paint nozzle for ejecting paint supplied at a ground potential is disposed at the center of the spray gun, and the paint nozzle is disposed outside the spray area. A grounding ring made of a conductive material and connected to the ground potential around the rear base of the external electrode, which has a fuselage that is arranged to extend further forward, expose the tip electrode at the tip, and cover the inner conductor with an insulator. Externally charged electrostatic painting gun with 2. The externally charged electrostatic coating gun according to claim 1, wherein at least a part of the grounding ring is provided with a sharp point. 2. The externally charged electrostatic coating gun according to claim 1, wherein the grounding ring is directly connected to the grounding member of the gun body with a conductive material.

Images