JP3749890B2 - Externally charged electrostatic spray gun - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a spray gun for electrostatic coating that is excellent in coating efficiency, safety, and workability, which is optimal when electrostatically coating a highly conductive paint such as water-based paint and metallic paint.
[0002]
[Prior art]
Electrostatic coating is widely used as a coating method in which high-voltage static electricity is charged to sprayed paint particles and the coating efficiency is improved by an electric field formed on an object to be coated from an electrostatic spray gun. 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.
[0003]
That is, solvent-based paints containing volatile organic compounds are required to be reduced in use due to environmental problems in recent years, and have been required to shift to water-based paints. However, if the sprayed paint is directly charged to increase the electrostatic coating effect, in the case of water-based paints, in a normal device, a charged high voltage flows to the grounded paint supply source through the paint, and electrostatic Not only can the effect not be obtained, but a high voltage flows through the paint supply system, causing a danger.
[0004]
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 supply as disclosed in JP-A-6-198228 is required. It is necessary to use a device, and it is necessary to install a large-scale device, which causes problems in use 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.
[0006]
As one of them, an electrostatic coating apparatus such as Japanese Patent Publication No. 56-38267 and Japanese Patent Application Laid-Open No. 53-30646 has been proposed as an apparatus that is integrated with and integrated with a spray gun. The external electrode type electrostatic spray gun applies an electric voltage to the ground potential side of the object to be painted by applying a high voltage to the external electrode installed at a position away from the spray paint area by the spray gun. It is formed and charged to the fine particles of the paint that passes through each of them, and is applied to an electric field formed toward the object to be coated to promote the coating. However, compared to the direct charging method described above, the charging effect on the paint particles passing through the discharge region is low, and a sufficient electrostatic effect is not obtained.
[0007]
In general, as a spray gun for electrostatic coating, which is effective for commercial use, in the case of the direct charging type mainly used for solvent-based paints, the charging voltage to the electrode is about -30 kV to -70 kV, and the potential difference is The effect can be obtained as much as possible, but it is required to be as low as possible in view of the increased risk of spark discharge and electric shock discharge due to high voltage and the withstand voltage strength of the apparatus. Therefore, it is increasingly used at around -50 kV. On the other hand, in the case of the external electrode method, charging is generally performed with a higher potential difference.
[0008]
Compared with the method in which the charged electrode is installed directly in the spray center of the paint and charged efficiently, the external charging method requires a higher voltage as described above in order to obtain a practical effect, and the position of the charged electrode is It is said to be 80mm to 150mm, and has a structure that protrudes greatly. In order to prevent a dangerous discharge to the spray outlet of the spray paint on the ground potential side in order to obtain a substantially high charging effect and to prevent a voltage drop of the charged electrode due to the discharge, a necessary distance is placed in front of the spray device, and Installed as close as possible to the spray flow.
[0009]
Usually, in the case of a commercial spray gun, when charging the above-mentioned high voltage, if the electrode position is not sufficiently separated from the spray center, the paint adheres due to the spread of the sprayed paint particles, reducing the discharge effect, The result is that coarse particles adhere to the object to be coated due to re-scattering of the adhering paint. In general, spray guns for painting use an oval or oval flat pattern, and depending on the shape of the object to be coated, a pattern that spreads vertically and a pattern that spreads horizontally can be used properly. By placing it at a close position, a preferable electrostatic effect and prevention of adhesion can be achieved.
[0010]
Because of the high voltage and the external electrode configuration that protrudes excessively, most of these devices are attached to the spray gun and attached to the spray gun, and most of the automatic spray guns are used in a fixed state during operation. There was no easy-to-use handheld spray gun. That is, as a hand-held spray gun, the charged electrode protrudes greatly forward, and is placed on the side to remove the spraying paint to prevent the function from being deteriorated. It was supposed to become a gun and increase the burden on the workers.
On the other hand, in the case of a hand-held type that needs to use various conditions more than the automatic spray gun and use different operating directions, that is, the pattern spreading direction with respect to the object to be coated, a device that can change the electrode position more easily is required. However, the conventional technology is insufficient.
[0011]
[Problems to be solved by the invention]
As described above, as an electrostatic spray gun using an external electrode, the electrode protruding from the tip at a practical level deteriorates operability, and it takes time for setting according to the painting work, and obtains an appropriate electrostatic effect. However, there is a problem that the work is continued without being set at a sufficient position. The position of the externally charged electrode greatly affects the coating efficiency and workability, especially when using a hand-held spray gun, and is as small as possible. It is desirable to be able to set.
[0012]
The fundamental problem to be solved by the present invention is to improve the operability of an electrostatic coating spray gun having an external charging electrode. Furthermore, the electrostatic coating spray gun itself has been downsized to ensure reliability and improve coating efficiency as a device that can be used with handheld spray guns. This is to reduce the use of volatile organic compounds that affect the environment.
[0013]
In addition to electrostatic painting, spray guns for painting are partly used for mass-production painting in automated lines in factories, and many operations are performed manually by the operator, especially in the final process of determining coating quality. It has been broken. In this way, the handling and operability of the spray gun not only improve the efficiency of coating, but also improve the work efficiency and the quality and stability of the coating, leading to improvements over the long term. Effectiveness is a very important factor.
[0014]
If painting is continued with the paint adhering to the external electrode or electrode holder, the accumulated paint particles will accumulate and cause the paint to sag, reducing the finish quality of the paint and impairing the reliability of the coating machine. There is a problem. In addition, when it is easy to harden like a water-based paint and is difficult to dissolve in a diluent in the paint, the solid content gradually laminated acts as an insulation, and the effect as an electrode is extremely reduced.
In addition, when changing the charging conditions according to the coating conditions as necessary, the electrostatic coating can be performed under the optimum conditions by making it possible to adjust the position of the external electrodes. Therefore, it is required that the external electrode is always kept in a suitable state and can withstand long-term use.
[0015]
The present invention has been made in view of the above-described problems and demands of the prior art. In the main range of electrostatic coating used, the operator is safe to use, easy to use, and productive and economical. It is possible to obtain a spray gun for electrostatic coating that can contribute to the widespread use of water-based paints that are effective and result in significant improvements in environmental problems.
[0016]
[Means for Solving the Problems]
In the present invention, an atomizing device provided at the tip of the barrel as an electrostatic coating spray gun, and an atomizing device and a high voltage generator at the rear thereof are provided. The static electricity is provided with an externally charged electrode that is separated from the high voltage output unit of the high voltage generator and protrudes to a position in front of the nebulizer that avoids the outer spray flow. In the electric spray gun, an annular insertion groove having at least 1/4 or more of the circumference is formed sufficiently deep in the axial center of the atomizing device from the front end surface of the spray nozzle on the paint nozzle mounting side , and the groove is formed at the bottom of the groove. A contact terminal to be connected to the output portion of the high voltage generator is arranged, and the insertion groove is entirely composed of an insulating material, and a tip electrode is inserted at one end and an external electrode exposing the contact end is inserted at the other end. in parts are connected to the contact terminal position It is characterized in that it has a constant possible.
[0017]
A suitable position is selected for the tip position of the external electrode depending on the shape of the spray pattern of the spraying device, so that the connection position of the external electrode can be rotated, and when it rotates, the spray cap determines the pattern shape of the atomizing device. The electrode tip can be arranged while avoiding the spray flow without setting it by mistake.
[0018]
Furthermore, the electrode tip position can be set at a necessary interval by allowing the electrode body having a predetermined length to be attached to and detached from the connecting portion. The predetermined length may be changed by preparing several electrode bodies with different dimensions fixed and replacing them, or the electrode body itself may be expanded or contracted.
[0019]
DETAILED DESCRIPTION OF THE INVENTION
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 the present embodiment. The spray gun 1 is a hand-held type and is operated with a handle 2 and a trigger 3. The gun barrel 4 controls the paint sprayed from the atomizing device 5 provided at the tip and controls the input / output of the low voltage power source supplied to the high voltage generator 6 arranged in the gun barrel 4 to thereby spray the gun 1. The high voltage charged in the tip electrode 71 of the external electrode 7 provided outside is controlled.
[0020]
In this embodiment, the atomizing device 5 is an air spray gun that atomizes paint with compressed air. An air cap 52 is disposed around the paint nozzle 51, and a desired spray pattern is formed in the air cap 52. The object to be painted is formed. 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, the paint path is connected to the ground side potential, so the needle valve 53 in the paint nozzle 51 is metallic, and the rear part It is electrically connected to the handle 2 located at the position. The handle is conductive, as is the case with regular electrostatic spray guns, and in this embodiment, a semiconductive resin is used so that it is at ground potential when the operator operates it by hand. I have to.
[0021]
The high voltage generator 6 is integrally constituted by a low frequency transformer, a multistage voltage doubler rectifier, and a cartridge in which a high resistance for protection is cast with an insulating resin. The supply power is supplied from the rear input terminal 65 through the handle 2, boosted to a high voltage, and then sent to the output terminal 66 exposed at the tip of the high voltage generator 6 through a high resistance. When the high voltage generator 6 is assembled in the barrel part, the internal connection piece 45 and the output terminal 66 are in contact with each other and are electrically connected.
[0022]
On the other hand, the connection piece 45 is connected to the contact terminal 12 disposed on the circumference around the spray axis in the back ( bottom ) of the insertion groove 13 formed from the distal end side of the barrel part 4. The contact terminal 12 is disposed at a position that is sufficiently away from the tip of the paint nozzle 51 exposed to the outside and inside the insulating barrel portion 4 to prevent creeping discharge.
[0023]
An insertion groove 13 extending from the front end of the spray gun 1 to which the atomizing device is attached to the contact terminal 12 is provided on the circumference, and the external electrode 7 is inserted into the insertion groove 13. As shown in FIG. 4, the opening is 180 ° in this example. However, when the horizontal and vertical spray patterns are used, the range may be 90 °. The external electrode 7 has an electrode tip 71 exposed at the tip, is entirely made of an insulating material, and a contact end 72 is exposed at the other end. Reference numeral 73 denotes a conductive wire, and a metal wire is usually used, but a semiconductive material may be used as a high-voltage conductive wire. The contact end portion 72 is configured to be securely connected to the contact terminal 12 by adding elastic means such as a spring even if there is a slight back and forth movement.
The tip of the external electrode 7 protrudes from the outside of the air cap 52 of the atomizing device 5 and is arranged at a position of about 70 mm forward and about 30 mm from the shaft center. This position is not limited, and is preferably changed at the coating conditions and used at the optimum position.
[0024]
The air cap 52 is generally formed with a flat pattern, and the electrostatic charging efficiency can be improved by placing the electrode tip 71 as close as possible without being affected by the spray particles. . Therefore, it is desirable that the flat pattern is not spread, and when the direction of the air cap 52 is changed, the position on the circumference of the electrode needs to be changed accordingly. In the embodiment, a rotation plate 54 is provided inside a cover 57 for fixing the air cap 52, the external electrode 7 is fixed to the cover 57, and the rotation of the rotation plate 54 changes the position of the external electrode 7 around the spray axis. be able to.
[0025]
In the example of FIG. 3 showing another embodiment, when the external electrode 7 is positioned on the solid line, the spray gun is operated in the vertical direction by the horizontally long pattern, and at the position indicated by the dotted line, the horizontal direction Shows the operation of the spray gun. The direction of the air cap 52 is usually used in the range of 90 °, but the electrode position may be changed by 180 ° between the case of operating with the right hand and the case of operating with the left hand so as not to impair the operability.
[0026]
In the case of a hand-held spray gun, the ability to easily change the electrode position is an extremely important factor in terms of workability as well as changing the air cap 52 during operation, and is an essential requirement. In this respect, according to the present invention, the operation can be easily changed without interrupting the operation, and an implementation effect can be obtained.
[0027]
Further, as shown in FIG. 6, a pin 55 protrudes from a part where the air cap 52 and the rotating plate 54 are combined, and a groove 56 that engages with the pin 55 at a fixed position is provided in the rotating plate 54. If the position of the electrode is fixed, and the electrodes move together at the same time, the electrode position corresponding to the spray position can always be maintained. Use can be continued without spending.
[0028]
【The invention's effect】
As described above, according to the present invention, an external electrode is attached to a hand-held electrostatic coating gun having a high voltage generator, and the external electrode is easily placed at an efficient position closer to the spray pattern state of the gun body. Therefore, it is possible to obtain a highly practical externally charged electrostatic coating machine that is excellent in operability and handling, and can be applied to a spraying operation and various coating conditions as a hand-held type.
[0029]
Also, since the high-voltage output terminal arranged inside the spray gun corresponds to the periphery of the spray axis, the external electrode that changes position is simply made of an insulating material and the contact electrode that sends high voltage to the tip electrode It only needs to have a part and a conductor. Therefore, it is possible to spread the use without taking time and effort for replacement due to breakage, contamination, etc. and daily handling.
[Brief description of the drawings]
1 is a cross-sectional view showing an embodiment of the present invention. FIG. 2 is a side view of the tip of a spray gun according to another embodiment. FIG. 3 is a front view of FIG. 2 is a partial cross-sectional view of the combined portion of the air cap 52 and the rotating plate 54.
1, spray gun 2, handle 3, trigger 4, barrel portion 5, atomizing device 6, high voltage generator 7, external electrode 12, contact terminal 13, insertion groove 51, paint nozzle 52, air cap 54, rotating plate 71, electrode tip 72, contact end

Claims (2)

A nebulizer provided at the tip of a hand-held spray gun barrel with a grip at the rear and a high voltage generator at the rear to maintain electrical insulation between the paint path supplied to the nebulizer In an electrostatic spray gun provided with an external charging electrode protruding to a front position avoiding the outer spray flow of the atomizing device, the electrode connected to the high voltage output portion of the high voltage generating device is separated. An annular insertion groove having at least 1/4 or more of the circumference is formed sufficiently deep in the axial center of the atomizing device from the front end surface of the spray nozzle on the paint nozzle mounting side, and the high voltage generator is formed at the bottom of the groove A contact terminal to be connected to the output portion, and the insertion groove is entirely composed of an insulating material, and a tip electrode is inserted at one end and an external electrode exposing the contact end is inserted at the other end, and the contact end is the contact and fixable connection position to the terminal External charging type electrostatic paint spray gun characterized and. The electrostatic coating spray gun according to claim 1, wherein the external electrode is fixed to a part of a spray cap that determines a pattern shape of an atomizing device, and an external electrode rotating means that moves integrally with the spray cap is provided.

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