JP2004148273A - Electrostatic coating method by external electrification and apparatus for the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To make an external electrification electrostatic coating immediately applicable to various atomizers by improving operability of an electrostatic coating spray gun having an external electrification electrode and protecting a worker by assuring safety, to achieve spread of electrostatic coating of water-base paints, and to improve coating efficiency and environment. <P>SOLUTION: The external electrification electrostatic coating comprises electrifying the paint sprayed from the atomizer with an external charge electrode disposed separately from a route for the paint. A high-voltage electrostatic charger including the external electrification electrode and the atomizer are separately manufactured. In electrostatic coating, the charger and the atomizer are mounted on each other and electrostatic coating is performed by activating the charger cooperatively with the operation of the atomizer and by utilizing the external electrification. The charger is integrally provided as an external electrification unit including a high-voltage generator, a high resistance to limit the excess current to the external electrode and the external charge electrode so that the electrostatic coating by the external electrification system can be easily performed by combination with the various atomizers. <P>COPYRIGHT: (C)2004,JPO

Description

[0001]
BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a spray gun for electrostatic coating which is excellent in coating efficiency, safety and workability, particularly when electrostatically coating highly conductive paints such as water-based paints and metallic paints. .
[0002]
2. Description of the Related Art Electrostatic coating is widely used as a coating method for charging sprayed paint particles with high voltage static electricity and improving the coating efficiency by an electric field formed on an object to be coated from an electrostatic spray gun. I have. Paints used for such electrostatic coating are roughly classified into solvent type paints having a large electric resistance value and high conductive paints such as water-based or metallic paints having a low electric resistance value in relation to the effect. The coating method and equipment are very different.
[0003]
That is, the use of solvent-based paints containing volatile organic compounds has been demanded to be reduced due to recent environmental problems, and a shift to water-based paints has been required. However, when an attempt is made to increase the electrostatic coating effect by directly charging the sprayed paint, in the case of a water-based paint, a high voltage that is charged in a usual apparatus flows through the paint to a grounded paint supply source, and the electrostatic force is reduced. Not only is the effect not obtained, but also a danger of high voltage flowing in the paint supply system.
[0004]
For this reason, a method and apparatus for insulating the paint supply system from the ground side and performing electrostatic coating while maintaining a high voltage have been used. However, due to the enormous amount of charge in the paint supply system, an increase in danger is unavoidable. Further, in order to increase the industrial efficiency by performing continuous coating work, paint supply as disclosed in JP-A-6-198228 is required. It is necessary to use the device, and it is necessary to introduce a large-scale device, and there are also problems in use precaution and maintenance.
[0005] Due to these problems, electrostatic coating of water-based paints and metallic paints has not spread widely and has caused delays in environmental measures. On the other hand, the paint particles passing through the area ionized by the discharge from the electrode installed outside the spray area without being directly charged with the paint are charged and placed on the line of electric force (electric field) toward the work to be painted, 2. Description of the Related Art An electrostatic coating machine using an external electrode to be coated on a substrate is known.
[0006]
As one of them, an electrostatic coating device as disclosed in JP-A-53-30646 or JP-A-7-213958 has been proposed as a device that is integrated with and cooperates with a spray gun. An external electrode type electrostatic coating spray gun applies a high voltage to an external electrode installed at a position outside the spray paint area by the spray gun, thereby discharging to the ground potential side of the object to be coated etc. to generate an electric field. It forms and charges the fine particles of the paint passing therethrough and places it on an electric field formed toward the object to be coated to promote coating. However, the effect of charging the paint particles passing through the discharge area is lower than that of the direct charging method described above, and a sufficient electrostatic effect has not been obtained.
[0007]
In general, as a spray gun for electrostatic coating that can obtain the effects of commercial use, in the case of a direct charging type used mainly for solvent-based coatings, the charging voltage to the electrode is about -30 kV to about -70 kV, and the potential difference is The effect is obtained as much as possible, but it is required to be as low as possible in view of the increased risk of spark discharge or electric shock discharge due to high voltage and the withstand voltage strength of the device. Therefore, it is often used at around -50 kV. On the other hand, in the case of the external electrode system, it is general that the electric potential is charged with a high potential difference from -70 to -90 kV.
[0008]
The external charging method requires a higher voltage in order to obtain a practical effect, compared to a method in which a charging electrode is placed directly at the center of the paint spray to efficiently charge, and the position of the charging electrode is substantially equal to the ground potential. It is installed in front of the spraying device in order to prevent dangerous discharge to the ejection port of the spray paint on the side and voltage reduction of the charging electrode due to the discharge.
Usually, the position of this charging electrode is said to be 80 mm to 150 mm in the case of a commercial spray gun, and has a configuration that protrudes greatly. For this reason, many are used as automatic spray guns that are driven by being attached to an automatic coating apparatus. In other words, as a hand-held spray gun, the charged electrode protrudes greatly forward and is placed off the axis of the spray to prevent its function from deteriorating due to spray paint, so it is large and difficult to operate. It becomes a gun and increases the burden on the worker.
[0009]
Proposals have been made for hand-held electrostatic spray guns, but at the practical level, the problems that the electrodes protruding at the tip degrade operability and that there is the danger of hitting and damaging items during operation have become widespread. Was braking. In addition, there is a big difference between the direct charging of paint and the charging by the discharge of an externally provided electrode.It is necessary to use a higher voltage, and in view of the withstand voltage, further increase in size is inevitable. In addition, a problem spreads to the cost, and there is a demand for an effective electrostatic coating method or apparatus using a commercially available external charging system.
[0010]
As described above, in the case of the external charging type, it is necessary to use a higher voltage and to consider the danger to this, to make the spray gun smaller, and to improve the use thereof. Therefore, it has not been possible to use it easily and safely in practical use in performing electrostatic coating using external electrodes.
A fundamental problem to be solved by the present invention is to improve the operability of an electrostatic spray gun having an externally charged electrode and to protect workers by ensuring safety. Then, considering a method that can be widely used, the present invention is applied to various cases to expand the range of use and spread the electrostatic coating of the water-based paint.
[0011]
It is easy to obtain the effect of electrostatic coating by external charging and relatively easy to use, increasing the demand for coating, and using water-based paint instead of solvent-based paint, which uses a large amount of volatile organic compounds that have a large effect on the environment. Shift to use of paint, reduction of loss by improving coating efficiency in electrostatic coating, and the like can be achieved. Therefore, the present invention provides a method and an apparatus which can achieve the effect of the present invention.
This type of apparatus that has been seen so far has been configured integrally with the spray gun as a dedicated apparatus equipped with a charging device and an atomizing device, and it was necessary to arrange a required number of each as a set.
[0012]
[Means for Solving the Problems]
According to the present invention, the action of an electric field formed toward an object to be coated is performed by separating the paint sprayed from the atomizer from the path of the paint, charging the paint by an external charging electrode provided outside the atomizer, and charging the paint. In the case of externally charged electrostatic coating, which is applied by adding an external electrode, a high-voltage electrostatic device including an externally charged electrode and an atomizing device are separately prepared, and these devices are combined at the time of electrostatic coating, and the atomizing device is used. The electrostatic painting is performed by utilizing the external charging by operating the high voltage electrostatic device in conjunction with the operation.
[0013]
In factory coatings that require industrial productivity, many atomizers are prepared and used separately, or used as spares when problems occur. There are various types of atomizing devices depending on the purpose, and in coating, a suitable device is used depending on the degree of coating quality of the paint and the object to be coated, the shape and material of the object to be coated, and the like. In this case, the external charging device for increasing the efficiency of electrostatic coating can be applied to a common device without the need for a device corresponding to each.
[0014]
According to the above method, it can be applied to many atomizing devices with a minimum number of external charging devices, and it is possible to reduce equipment costs and maintenance.
When the atomizing device is a hand-held type, the operability and safety can be maintained by interlocking and controlling the charge together with the spraying by the trigger operation. Further, the nebulizer and the high voltage charging may be controlled by an external signal.
[0015]
Further, according to the present invention, the atomizing device, the high voltage generating device, and the path of the paint supplied to the atomizing device are separated and provided outside the atomizing device, and the high voltage from the high voltage generating device is charged. An externally charged electrostatic coating gun having an externally charged electrode, a high voltage generator, a high resistance for limiting an excessive current to the external electrode, and an externally charged unit including the externally charged electrode. And is detachable from the atomizing device.
Therefore, a unit is provided with the electrical components necessary for performing electrostatic coating by an external charging system. This unit is used immediately in combination with a desired atomizing device to immediately form an electrostatic coating device. It can be used as
[0016]
Preferably, by making the external charging electrode detachable from the external charging unit, it is easy to replace only the electrode, and it is possible to cope with a change in the electrode position. Also, a plurality of external charging electrodes can be provided as needed, and the range of correspondence can be expanded.
[0017]
Also, a power supply terminal is provided in the atomizing device section, and is configured to be connected to an input terminal of the high voltage generator when the external charging unit is mounted, and the high voltage charging is turned on by operation of the atomizing device side. Can be turned off.
The attachment / detachment portion has a locking means that can be attached with a single touch, and the removal is achieved by releasing the locking means and removing it.
[0018]
Furthermore, by using a chemical sprayer as the atomizing device, it can be easily used in fields such as spraying chemicals and spraying treatment agents other than coating, which has been delayed in the past, and improving coating efficiency. And the prevention of scattering of harmful and toxic substances.
[0019]
Embodiments of the present invention will be described below with reference to the drawings.
FIG. 1 shows an externally charged electrostatic spray gun according to the present embodiment. The spray gun is a hand-held type and is operated by holding a handle 2 and a trigger 3 of a spray gun body 1. The barrel section 4 incorporates a valve for compressed air for atomizing paint ejected from an atomizing device 5 provided at the tip, a device for adjusting the flow rate of paint, and the like.
[0020]
In this embodiment, the atomizing device 5 is an air spray gun for atomizing the paint with compressed air. An air cap 51 is provided around a paint nozzle 52, and a desired spray pattern is applied to the air cap 51. The coating of the object to be coated is performed. These structures adopt a widely known structure of a spray gun, but are formed of an electrically insulating material including the barrel 4 in electrostatic coating. In the case of a spray gun in which a water-based or highly conductive paint is used in the present invention and a charged electrode is provided outside, the paint path is connected to the ground side potential, so that the needle valve 53 in the paint nozzle 52 is made of metal, Is electrically connected to the handle 2. The handle is electrically conductive, as is the case with conventional electrostatic spray guns, and in this embodiment, a semi-conductive resin is used to provide a ground potential for manual operation by an operator. I have to.
[0021]
The external charging unit 9 disposed on the upper part of the barrel 4 incorporates a high-voltage generator 6 as shown in FIG. 5, and is configured to be separated from the spray gun main body 1 including the atomizing device 5. . The external charging unit 9 includes a high-frequency generator 6 composed of a low-frequency transformer 61, a Cockcroft-Walton multi-stage voltage doubler rectifier circuit 62, a cartridge 64 in which a protective high resistance 63 is cast with an insulating resin, and an external electrode. 7 are incorporated in a unit cover 68 made of an insulating material.
[0022]
The cartridge 64 has an electrically insulating strength maintained except that the input terminal 65 is exposed to the low voltage supply side and the output terminal 66 is exposed to the high voltage output side. Connected to conducting wire 12. An electrode connection portion 13 of an external electrode is separately provided on the unit cover 68, and the other end of the conductive wire 12 is exposed as a connection terminal 14 inside the electrode connection portion 13 of an insulating material. When the external charging unit 9 is incorporated in the spray gun main body 1, the electrode connecting portion 13 is arranged so as to be located outside the barrel 4 behind the atomizing device 5 as shown in FIGS. 2 to 4. .
[0023]
The external electrode 7 attached to the electrode connection portion 13 has the tip electrode 71 exposed at the tip and a detachable portion 72 provided at the rear end, and is entirely formed of an insulating material. The connection terminal 73 is exposed from one end of the attaching / detaching portion 72, and the connection terminal 73 and the tip electrode 71 are connected by a conductor 74. When the external electrode 7 is mounted on the electrode connection portion 13 of the unit cover 68, the connection terminal 73 and the connection terminal 14 on the side of the external charging unit 9 come into contact and are electrically connected. In the present embodiment, the connection terminal 73 is formed of a spring in order to ensure connection, but the connection terminal 14 may be formed of a spring.
[0024]
As shown in FIG. 4, the external electrode 7 is inserted into the electrode connecting portion 13 and fixed by locking the locking piece 75 in the locking groove 15 by slightly rotating the external electrode 7 so that the external electrode 7 has a required tip electrode position. Can be arranged. This locking method is not limited to this example, and the locking means that is normally used, that is, simply inserts, tightly adheres by its dimensional accuracy, and obtains the necessary fixing force by frictional force, but the deformation of the locking piece and the groove which are deformed. When engaging and disengaging, and detaching, it is possible to select a method such as using a method in which the engaging piece is opened and removed.
[0025]
The means for incorporating the external charging unit 9 into the spray gun body 1 is not limited, and a general-purpose fixing means is adopted. Here, a concave portion is formed in the front of the barrel portion of the spray gun body 1, a locking piece engaging with the concave portion is formed on the side of the external charging unit 9, and further fitted to the rear end portion with both sides of the barrel portion sandwiched and fixed. It has the shape to be done. The unit cover 68 can be attached and detached by hand utilizing the elastic deformation of the resin. However, in order to eliminate the risk of detachment during use, use of another fixing means such as a set screw is required. But it's fine.
[0026]
The power supplied to the high voltage generator 6 of the external charging unit 9 is sent from a power cable connected to the spray gun body 1 via a switch that is opened and closed according to a trigger operation. When the external charging unit 9 is incorporated, the output terminal on the side of the spray gun body 1 and the input terminal 65 of the cartridge 64 are positioned so as to be connected to each other, and are electrically connected, thereby facilitating the connection. As the contact, an existing connection method such as a slide type or a press type is adopted.
[0027]
When performing electrostatic coating using these devices, the spray gun main body 1 is combined with an external charging unit 9 and a predetermined connection is made to supply a predetermined power supply, paint, and compressed air for atomization, and the spray gun is operated. When operated, a high voltage is sent to the charging electrode from the power supply sent to the external charging unit 9 together with the spraying of the paint, and the sprayed paint particles are charged by the high voltage static electricity discharged from the charging electrode, and the counter electrode is charged. It can be applied to the object to be coated and electrostatically applied.
[0028]
Since the external charging unit 9 is configured as a unit for generating high voltage and charging electrodes, it can be separately manufactured and prepared, and even if a problem arises in which the use must be stopped due to an electrical trouble. By simply replacing this part, the spray gun itself including the paint supply path can be used as it is.
[0029]
Further, in this embodiment, the present invention is applied to the case of an air spray gun.However, it is not necessary to specify the atomization method to charge the sprayed paint and increase the coating efficiency by the action of the electrostatic field. The same effect can be obtained by applying the present invention to a spray gun such as an airless or airless spray method. The present invention is not limited to a hand-held spray gun, and can be applied to a spray gun that automatically controls the operation of spraying.
[0030]
Furthermore, the present invention is to charge a spray liquid to a spray device as an atomizing device and to assist in application to an object to be coated placed on the earth side. It is also possible to attach the external charging unit of the invention. In this case, charging is not necessarily performed via the sprayer, and the voltage is boosted to a high voltage by directly supplying the external charging unit, and an electrostatic charging effect can be obtained by discharging from the external electrode.
[0031]
【The invention's effect】
As described above, according to the present invention, it is possible to develop a wide range of uses by using one external charging unit, and as an apparatus applicable to electrostatic coating, particularly a highly conductive coating such as a water-based coating, an external charging type. A situation where the electrostatic coating apparatus can be used easily can be obtained.
[0032]
In addition, since the nebulizing device and the external charging device can be prepared separately and used in combination as needed, efficient use with a small amount of equipment can reduce the overall equipment cost and maintenance cost, and can reduce the cost of each part. Since only a necessary part can be exchanged for a problem in which a trouble or a use is limited, it is possible to obtain an effect that a trouble can be dealt with without interruption of work.
[0033]
Furthermore, the position of the charging electrode, which needs to be slightly changed, which is limited to the individual spray guns, can be more extensively controlled by configuring the electrode body to be detachable from the external charging unit so that it can be replaced. Enables electrostatic coating, enhances the effect of applying electrostatic coating to water-based paints, promotes the application of electrostatic coating with it, and improves the efficiency of coating obtained. It can lead to reduction in the use of compounds.
In addition, the high-voltage charging according to the present invention is only the portion of the external electrode attached to the front end portion of the external charging unit, and the effect of electrostatic coating can be obtained extremely safely and in any place. Therefore, it can be easily used in fields such as chemical spraying and treatment agent spraying other than the coating which has been delayed in the past, improving coating efficiency and preventing scattering of harmful and toxic substances. Become like
[Brief description of the drawings]
FIG. 1 is an overall sectional view showing one embodiment of the present invention.
FIG. 2 is an external view when the spray gun main body and the external charging unit of FIG. 1 are separated.
FIG. 3 is an external view of the combination.
FIG. 4 is a plan view of the tip portion of FIG.
FIG. 5 is a schematic diagram illustrating a configuration of an external charging unit.
FIG. 6 is a schematic diagram showing a configuration of a high-voltage generator.
[Explanation of symbols]
1, spray gun body 2, handle 3, trigger 4, barrel 5, atomizing device 6, high voltage generator 7, external electrode 9, external charging unit 13, electrode connection 71, tip electrode

Claims (8)

The paint sprayed from the atomizer is separated from the paint path, charged by the external charging electrode provided outside the atomizer, and applied by the action of an electric field formed toward the object to be coated. When performing externally charged electrostatic coating, a high-voltage electrostatic device including externally charged electrodes and an atomizing device are separately prepared, and these devices are attached to each other during electrostatic coating to operate the atomizing device. Method of performing electrostatic coating using external charging by operating a high voltage electrostatic device in conjunction with it 2. The electrostatic coating method according to claim 1, wherein a desired atomizing device that differs according to the atomizing characteristics is selected, and the charging of the high-voltage electrostatic charging device mounted by controlling the operation of the atomizing device is controlled. The electrostatic coating method according to claim 1, wherein the atomizing device and the high-voltage electrostatic device are controlled by an external signal. The atomizing device, the high voltage generating device, and the path of the paint supplied to the atomizing device are separated from each other and provided outside the atomizing device, and the external charging in which the high voltage from the high voltage generating device is charged. In an externally charged electrostatic painting gun having electrodes, a high voltage generator, a high resistance for limiting an excessive current to the external electrodes, and an externally charged unit including the externally charged electrodes are integrally provided, and the unit is provided. Is an electrostatic coating device which is detachably attached to the atomizing device. The electrostatic coating apparatus according to claim 4, wherein an external charging electrode is detachable from the external charging unit. 5. The electrostatic coating device according to claim 4, wherein a power supply terminal is provided in the atomizing device, and the power supply terminal is connected to an input side of a high voltage generator of the external charging unit when the external charging unit is mounted. 5. The electrostatic coating apparatus according to claim 4, wherein the attaching / detaching portion has a locking means to be attached with one touch, and the detaching means releases the locking means to remove. The electrostatic coating device according to claim 4, wherein the atomizing device is a chemical sprayer.

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