JPH11179246A - Gun for electrostatic powder coating - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an electrostatic powder coating gun for performing powder coating with high coating efficiency and also enabling to easily adjust a diameter of a coating pattern. SOLUTION: Mixing air is ejected from a mixing air introduction port of a swirl stream forming member 31 within a flow path 12 in the tangent direction, and a powder paint is ejected from an annular nozzle opening 13 toward the front while it is swirling. Dispersion air ejected toward the front of a gun main body 1 from a dispersion air ejection port 21 at a dispersion air forming member 20 is brought into collision with a dispersion tip 22, and ejected from a path 23 to the radial outside, and the powder paint is dispersed to the radial outside with the dispersion air. The dispersed powder paint is suppressed the excessive dispersion with the control air passing through the control air ejection port 17 to be ejected to the front, and is sprayed toward an article to be coated.

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 gun which applies an electric charge to a powder coating, sprays the coating, and applies static electricity to a coating object.

[0002]

2. Description of the Related Art From the viewpoint of environmental protection, electrostatic powder coating has attracted attention as an environmentally friendly and pollution-free coating method that does not use a solvent. In this electrostatic powder coating, powder paint is supplied from a paint tank to a coating gun via an injector, and is sprayed from a nozzle opening formed at the tip of the coating gun together with a conveying air flow toward an object to be coated. You. At this time, a high voltage is applied to the pin-type electrode provided at the tip of the coating gun, and the object to be coated is grounded, and corona discharge is generated from the electrode of the coating gun toward the object to be coated. .
Therefore, when the powder paint sprayed from the nozzle opening passes near the electrodes, the powder paint collides with ions generated by corona discharge and is charged. The charged powder coating material is applied on the surface of the object to be coated under the influence of the transport air flow and the electric force along the line of electric force.

[0003]

However, simply spraying the powder coating material together with the carrier air flow from the nozzle opening limits the diameter of the coating pattern in accordance with the shape, direction, size, etc. of the nozzle opening. . Flow velocity of the conveying air,
The diameter of the coating pattern can be adjusted to some extent by pressure or the like.However, when the flow velocity of the conveying air toward the object is increased, the powder paint once adhered to the surface of the object is blown off by the air flow. There arises a problem that it is difficult to perform a desired coating. There is also a method of changing the diameter of the coating pattern by introducing dispersion air in the conveying air flow in the radial direction.In this method, the powder paint toward the object to be coated is scattered by the dispersion air together with the conveyance air, and the coating is performed. There was a risk that efficiency would decrease.

SUMMARY OF THE INVENTION The present invention has been made to solve such a problem, and an electrostatic powder coating gun capable of performing powder coating with high coating efficiency and easily adjusting the diameter of a coating pattern. The purpose is to provide.

[0005]

SUMMARY OF THE INVENTION An electrostatic powder coating gun according to the present invention is an electrostatic powder coating gun for electrostatically applying a charged powder coating on the surface of an electrically grounded object to be coated. A gun body for ejecting powder paint forward from an annular nozzle opening formed at the tip, and a powder paint provided at the tip of the gun body and charged from the nozzle opening. A corona electrode, a dispersing air ejecting means for ejecting dispersing air radially outward from the inside of the nozzle opening to the powder paint ejected from the nozzle opening, and a control air ejector formed along an outer peripheral portion of the nozzle opening. Control air jetting means for jetting control air forward to suppress excessive dispersion of the powder coating material radially outward due to the dispersed air.

[0006] As the corona electrode, a plurality of corona electrodes may be arranged at equal intervals on the concentric circle with the nozzle opening between the nozzle opening and the air ejection port of the control air ejection means, or radially inside the nozzle opening. It is also possible to arrange a plurality of corona electrodes. As the dispersing air jetting means, a plurality of dispersing air jets each directed toward the front of the gun body are arranged annularly inside the nozzle opening, and a dispersing tip is provided in front of these dispersing air jets. The dispersing air jetted forward can collide with the dispersing tip and change its direction radially outward. The control air ejection port of the control air ejection means may be one in which a plurality of ejection ports each having a predetermined divergent angle with respect to the central axis of the gun body are annularly arranged along the outer peripheral portion of the nozzle opening.

Further, a plurality of ion trap electrodes which are arranged on the outer periphery of the gun body and are electrically grounded for trapping free ions generated by corona discharge may be arranged on the outer periphery of the gun body. . Further, a swirl flow forming means for forming a swirl flow in the powder flow path in the gun body may be provided. An air chamber may be formed in the gun body so as to communicate with the control air outlet, and an electrode for preventing paint adhesion to which a voltage having the same polarity as that of the corona electrode is applied may be arranged in the air chamber.

[0008]

Embodiments of the present invention will be described below with reference to the accompanying drawings. Embodiment 1 FIG. FIG. 1 shows a configuration of an electrostatic powder coating gun according to Embodiment 1 of the present invention. The electrostatic powder coating gun has a substantially cylindrical gun body 1, a powder passage 2 is formed on the central axis of the gun body 1, and an outer cylinder 3 is provided in a front half of the gun body 1. Is provided. As clearly shown in the enlarged view of FIG. 2, inner cylinders 4 and 5 are provided in the outer cylinder 3, and the inner cylinder 4 communicates with the powder flow path 2 and faces forward of the gun body 1. A conical opening 6 whose diameter is increased is formed. Cylindrical openings 7 and 8 communicating with the opening 6 of the inner cylinder 4 are formed inside the inner cylinder 5 and the outer cylinder 3. A cylindrical head 9 is disposed in the openings 7 and 8, and a conical diffuser 10 disposed in the opening 6 of the inner cylinder 4 is connected to a base end of the head 9. A conical flow path 11 communicating with the powder flow path 2 is formed between the outer peripheral surface of the diffuser 10 and the opening 6 of the inner cylinder 4,
A cylindrical channel 12 communicating with the channel 11 is formed between the outer peripheral surface of the head 9 and the openings 7 and 8. The distal end of the flow path 12 is exposed to the front outside of the gun body 1 as an annular nozzle opening 13.

At the front end of the outer cylinder 3, a pin-shaped corona electrode 14 is provided outside the nozzle opening 13 so as to protrude forward. As shown in FIG. 3, eight corona electrodes 14 are arranged at equal intervals on a concentric circle with the nozzle opening 13. The corona electrodes 14 are electrically connected to each other, and are connected to a high-voltage generator (not shown) through the outer cylinder 3 and the inner cylinders 4 and 5.

A front cover 15 is provided on the outer periphery of the distal end of the outer cylinder 3, and an annular control air chamber 16 is formed between the front cover 15 and the outer cylinder 3. Front cover 1
The front surface of each of the control air outlets 1 is inclined to have a predetermined spread angle with respect to the center axis of the gun body 1.
7 are formed and connected to the control air chamber 16.
As shown in FIG. 3, a large number of control air outlets 17 are arranged concentrically with the nozzle opening 13 and outside the corona electrode 14 at equal intervals. The control air chamber 16 communicates with a control air supply port (not shown) at the back of the gun body 1 via a pressurized air passage 18.

A dispersion air chamber 19 is provided at the front end of the head 9.
Is formed, and a dispersion air forming member 20 is provided so as to cover the dispersion air chamber 19. As shown in FIG. 4, a large number of dispersed air ejection ports 21 communicating with the dispersed air chamber 19 are annularly arranged in the dispersed air forming member 20. A hemispherical dispersing tip 22 is disposed in front of the dispersing air forming member 20.
A circular passage 23 communicating with each of the dispersing air jets 21 is formed between the second dispersing air forming member 20 and the front surface of the dispersing air forming member 20.
The dispersion air chamber 19 communicates with a dispersion air supply port (not shown) at the back of the gun body 1 via a pressurized air passage 24.

An assembly ring 25 is mounted on the base end of the outer cylinder 3, and an annular paint adhesion preventing air chamber 27 is formed between the assembly ring 25 and a flange 26 of the outer cylinder 3. An annular air outlet 28 communicating with the air chamber 27 is formed between the outer cylinder 25 and the outer peripheral surface of the outer cylinder 3. The air chamber 27 is provided with a pressurized air passage 29.
Is connected to a paint adhesion preventing air supply port (not shown) at the back of the gun body 1 through the air supply port.

A cylindrical swirl flow forming member 31 is provided in the opening 8 of the outer cylinder 3 so as to form an annular mixed air chamber 30 with the outer cylinder 3. An opening 32 is formed at the center of the swirling flow forming member 31 so as to be continuously connected to the opening 8 of the outer cylinder 3. As shown in FIG. A plurality of mixed air inlets 33 are formed tangentially to 32. The mixing air introduction port 33 allows the mixing air chamber 30 and the flow path 12 to communicate with each other. The mixed air chamber 30 is connected to a mixed air supply port provided on the back of the gun body 1 via an air supply pipe (not shown).

In FIG. 1, a ring member 34 is provided on the outer peripheral portion of the gun body 1, and a plurality of pin-type ion trap electrodes 35 are mounted on the ring member 34 so as to project toward the front of the gun. I have. The plurality of ion trap electrodes 35 are fixed to a ring-shaped conductive member 36, and pressurized air ejection ports 37 formed on the ring member 34, respectively.
The tip part protrudes forward through the inside. The pressurized air outlet 37 is formed slightly thicker than the ion trap electrode 35, and forms a gap between the pressurized air outlet 37 and the ion trap electrode 35 for allowing pressurized air to flow. Each pressurized air jet 37 is provided between the ring member 34 and the outer peripheral portion of the gun body 1.
8 and the air chamber 38 is connected to the pressurized air passage 3.
9 communicates with the ion trap air supply port 40 at the back of the gun body 1. In addition, each ion trap electrode 3
Numeral 5 is electrically connected to a ground terminal 41 provided on the outside of the gun body 1 via a conductive member 36.

The control air supply port, the dispersion air supply port, the paint adhesion prevention air supply port, the mixing air supply port, and the ion trap air supply port 40 formed on the back of the gun body 1 are provided with:
Air supply means for supplying pressurized air is connected to each. Further, a powder paint supply port 42 communicating with the powder flow path 2 is provided at the back of the gun body 1.

Next, the operation of the first embodiment will be described. First, when a high voltage is generated by a high voltage generator (not shown) and applied to the corona electrode 14, the corona electrode 1
Corona discharge is generated from No. 4 toward the object to be coated. At this time, since the ion trap electrode 35 at the ground level is disposed behind the corona electrode 14, the lines of electric force concentrate on the ion trap electrode 35, and most of the free ions generated near the corona electrode 14 are electrically charged. It moves along the line of force and is trapped by the ion trap electrode 35.

In this state, the powder paint is conveyed to the carrier air and supplied from the powder paint supply port 42, and pressurized air is supplied from the control air supply port, the dispersion air supply port, and the mixed air supply port. You. The powder paint collides with the diffuser 10 through the powder flow path 2, and the agglomerated powder paint is crushed and dispersed to form a conical flow path 11 to a cylindrical flow path 12.
Flows to Here, the pressurized air supplied to the mixing air chamber 30 is jetted tangentially into the channel 12 from the mixing air inlet 33 as the mixing air. As a swirling flow around the central axis, the powder paint is ejected forward from the annular nozzle opening 13 while swirling.

At this time, the pressurized air supplied to the dispersing air chamber 19 is ejected to the front of the gun body 1 through the dispersing air ejection port 21 of the dispersing air forming member 20, and further collides with the dispersing tip 22. The direction is changed, and the air is ejected radially outward from the circular passage 23 as dispersed air.
Therefore, the powder paint ejected forward from the nozzle opening 13 is dispersed radially outward by the dispersed air, and is charged by ions generated by corona discharge near the corona electrode 14. Further, the pressurized air supplied to the control air chamber 16 passes through the control air jet port 17 and is jetted forward as a control air at a predetermined spread angle.
The powder coating material dispersed radially outward by the dispersion air is suppressed from being excessively dispersed, and is sprayed toward an object (not shown).

The powder coating charged near the corona electrode 14 is supplied to the corona electrode 14 and the ion trap electrode 35.
However, since the control air is ejected forward from the control air ejection port 17, it is suppressed from being attracted to the ion trap electrode 35 because the control air is ejected forward from the control air ejection port 17. Head to the object to be coated.

FIG. 6 shows a measurement result of a 1/2 pattern width when powder coating is performed by using the electrostatic powder coating gun according to Embodiment 1 and changing the dispersion air pressure. 1 /
The two-pattern width represents the diameter of a portion having a thickness of 1/2 of the maximum thickness when a coating film is formed on a substrate. In FIG. 6, A1 to A4 each have a control air flow rate of 70 l / min, A1 has no mixed air,
2 is a mixed air pressure of 1 kgf / cm ² , A3 is a mixed air pressure of 2
kgf / cm ² and A4 indicate measured values when the mixed air pressure was 3 kgf / cm ² . FIG. 7 shows the measurement results of the パ タ ー ン pattern width when the mixed air pressure was changed. B1 to B3 each have a control air flow rate of 70 l / m.
in, B1 is the dispersion air pressure 1.5 kgf / cm ² , B
2 distributed air pressure 2.0 kgf / ^cm 2, B3 indicates a measured value in the case of a dispersion air pressure 2.5 kgf / cm ^2. FIG. 8 shows the measurement results of the 1/2 pattern width when the control air flow rate was changed. C1 to C3 are each without mixed air, and C1 is a dispersed air pressure of 1.5 kgf / c.
m ^2, C2 distributed air pressure 2.0kgf / ^cm 2, C3 represents the measured values in the case of a dispersion air pressure 2.5 kgf / cm ^2. As can be seen from these measurement results, the diameter of the coating pattern can be changed by adjusting the pressure or flow rate of the mixing air, the dispersing air, and the control air.

The mixing air pressure is 1 kgf / cm ² , the dispersing air pressure is 2.0 kgf / cm ² , and the control air flow rate is 70 l / m.
Under the condition of “in”, the discharge amount of the powder coating material is 180 g / min.
And 200 g / min, the coating efficiency was measured and found to be as high as 90.5 to 99.6%.

When powder coating is performed, the nozzle opening 13
A portion of the powder paint ejected from the nozzles easily adheres to the outer peripheral portion of the outer cylinder 3 and the vicinity of the ion trap electrode 35. Therefore, pressurized air is supplied from the paint adhesion preventing air supply port and the ion trapping air supply port 40 on the back of the gun body 1. The pressurized air that has entered the paint adhesion preventing air chamber 27 is jetted forward from the annular air outlet 28 along the outer peripheral portion of the outer cylinder 3, whereby the powder paint is applied to the outer peripheral portion of the outer cylinder 3. Adhesion is prevented. The pressurized air entering the ion trap air chamber 38 is supplied to each pressurized air jet port 3.
7, the powder paint is sprayed forward to prevent the powder paint from adhering to the ion trap electrode 35.

Embodiment 2 FIG. FIG. 9 shows the configuration of the tip of the electrostatic powder coating gun according to the second embodiment. This electrostatic powder coating gun is the same as the electrostatic powder coating gun according to the first embodiment, except that a plurality of corona electrodes 14 are provided between the nozzle opening 13 and the control air outlet 17 and concentrically with the nozzle opening 13. Instead of being provided, the dispersing tip 2
2, a plurality of corona electrodes 14 are provided radially. As shown in FIG. 10, eight corona electrodes 14 are arranged radially and at equal intervals. Further, in the electrostatic powder coating gun of the second embodiment, the control air chamber 1
6, a plurality of pin-type paint adhesion preventing electrodes 43 are provided, and the plurality of corona electrodes 14 and the plurality of paint adhesion prevention electrodes 43 are electrically connected to each other, and are shown via lead wires 44. Not connected to a high voltage generator.

Also in this electrostatic powder coating gun, when a high voltage is generated by a high voltage generator and applied to the corona electrode 14, a corona discharge is generated from the corona electrode 14 toward the object to be coated, and the nozzle opening 13 Is sprayed toward the object to be coated by the ions generated by the corona discharge.

At this time, since the paint adhesion preventing electrode 43 is electrically connected to the corona electrode 14, a voltage having the same polarity as the voltage applied to the corona electrode 14 is also applied to the paint adhesion prevention electrode 43. You. Therefore, the potential of the front cover 15 generated by the electric field formed around the paint adhesion preventing electrode 43 has the same polarity as the powder paint charged by the ions generated by the corona discharge, and the powder paint becomes the front cover. It is prevented from repelling from 15 and adhering to the front cover 15.

Also in the electrostatic powder coating gun of the second embodiment, the effect that the diameter of the coating pattern can be changed by adjusting the pressure or the flow rate of the mixing air, the dispersing air, and the control air can be obtained. This is the same as the electrostatic powder coating gun of the first embodiment.

[0027]

As described above, in the electrostatic powder coating gun of the present invention, the diameter of the coating pattern can be easily controlled by adjusting the pressure or the flow rate of the mixing air, the dispersing air and the control air. Powder coating can be performed with high coating efficiency. Therefore, it is possible to widely apply the powder coating to various kinds of objects to be coated having different shapes and sizes. Further, if the present invention is applied to a coating gun having an ion trap electrode for trapping free ions, the control air flow causes an electrostatic attraction to be applied from an electric field formed between the corona electrode and the ion trap electrode. It is possible to prevent the powder paint from being attracted to the ion trap electrode, which has a particularly remarkable effect in preventing the paint from adhering to the gun body and improving the coating efficiency.

[Brief description of the drawings]

FIG. 1 is a sectional view showing a configuration of an electrostatic powder coating gun according to Embodiment 1 of the present invention.

FIG. 2 is an enlarged view of a main part of FIG.

FIG. 3 is a front view showing the tip of the gun body of the electrostatic powder coating gun according to the first embodiment.

FIG. 4 is a front view showing a dispersion air forming member used in the electrostatic powder coating gun according to the first embodiment.

FIG. 5 is a front view showing a swirl flow forming member used in the electrostatic powder coating gun according to the first embodiment.

FIG. 6 is a graph showing a relationship between a dispersion air pressure and a 1/2 pattern width by the electrostatic powder coating gun according to the first embodiment.

FIG. 7 is a graph showing a relationship between a mixed air pressure and a 1/2 pattern width by the electrostatic powder coating gun according to the first embodiment.

FIG. 8 is a graph showing a relationship between a control air flow rate and a 1/2 pattern width by the electrostatic powder coating gun according to the first embodiment.

FIG. 9 is a sectional view showing a main part of the electrostatic powder coating gun according to the second embodiment.

FIG. 10 is a front view showing the tip of the gun body of the electrostatic powder coating gun according to the second embodiment.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Gun main body 2 Powder flow path 3 Outer cylinder 11, 12 Flow path 13 Nozzle opening 14 Corona electrode 15 Front cover 16 Control air chamber 17 Control air ejection port 19 Dispersion air chamber 20 Dispersion air forming member 21 Dispersion air ejection port 22 Dispersion tip 23 Passage 30 Mixing air chamber 31 Swirling flow forming member 33 Mixing air inlet 34 Ring member 35 Ion trap electrode 41 Ground terminal 42 Powder paint supply port 43 Paint adhesion preventing electrode

 ──────────────────────────────────────────────────の Continued on the front page (72) Inventor Satoshi Nakamura 1-15-1 Nihonbashi, Chuo-ku, Tokyo Inside Nippon Park Coloring Co., Ltd.

Claims (8)

[Claims] 1. An electrostatic powder coating gun for electrostatically applying a charged powder coating on a surface of an electrically grounded object, wherein the gun is provided in front of an annular nozzle opening formed at a tip end thereof. A gun body for ejecting powder paint toward the body, a corona electrode provided at the tip of the gun body and charging the powder paint ejected from the nozzle opening, and a powder paint ejected from the nozzle opening A dispersion air ejection means for ejecting dispersion air radially outward from the inside of the nozzle opening; and a control air ejection port formed along an outer peripheral portion of the nozzle opening to inject control air forward to disperse air. An electrostatic powder coating gun comprising: a control air jetting means for suppressing an excessive dispersion of a powder coating material radially outward. 2. The electrostatic powder according to claim 1, wherein a plurality of corona electrodes are arranged at equal intervals between the nozzle opening and the air ejection port of the control air ejection means and on a concentric circle with the nozzle opening. Body painting gun. 3. The electrostatic powder coating gun according to claim 1, wherein a plurality of corona electrodes are radially arranged inside the nozzle opening. 4. The dispersed air jetting means are arranged annularly inside a nozzle opening and are provided in front of the dispersed air jets with a plurality of dispersed air jets each directed toward the front of the gun body. The electrostatic powder coating according to any one of claims 1 to 3, further comprising: a dispersing tip that causes the dispersing air jetted forward from the dispersing air jet port to collide with the dispersing air to change its direction radially outward. gun. 5. The control air ejection means includes a plurality of control air ejection ports arranged annularly along an outer peripheral portion of the nozzle opening and each having a predetermined spread angle with respect to a central axis of the gun body. The electrostatic powder coating gun according to claim 1. 6. An ion trap electrode according to claim 1, further comprising a plurality of ion trap electrodes disposed on an outer peripheral portion of said gun body and electrically grounded for trapping free ions generated by corona discharge. An electrostatic powder coating gun according to claim 1. 7. The electrostatic powder coating gun according to claim 1, further comprising a swirling flow forming means for forming a swirling flow in a powder flow path in the gun body. 8. An air chamber is formed in the gun body so as to communicate with the control air ejection port, and an electrode for preventing paint adhesion to which a voltage having the same polarity as the corona electrode is applied is formed in the air chamber. 4. The electrostatic powder coating gun according to claim 3, wherein the gun is disposed.