JPH03262558A - Electrostatic painting apparatus - Google Patents

Abstract

PURPOSE:To adapt a direct charging system to conductive paint by making it possible to wash the supply pipeline between a paint/washing fluid supply means and a change-over valve means. CONSTITUTION:The interior of a cylinder container 1 composed of a hollow cylindrical hermetically closed cylinder body is demarcated into a paint chamber 3 and an insulating liquid chamber 4 by a free piston 2. Paint and a washing fluid are supplied to the paint chamber 3 of the container 1 by a paint/washing fluid supply means 5 through a supply pipeline 10. Further, a change-over valve device 12 is provided on the way of the supply pipeline 10 to selectively connect the means 5 to the container 1 and a waste liquid tank 14. An insulating liquid supply and discharge means 15 performs the supply and discharge of an insulating liquid with respect to the insulating liquid chamber 4 of the container 1. Further, high voltage is applied to the painting machine 22 connected to the paint chamber 3 of the container 1 to spray paint to an object to be painted by a high voltage applying means 27. As a result, a direct charging system can be adapted even to conductive paint such as aqueous paint or metallic paint.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to an electrostatic coating device suitable for use in electrostatically coating conductive paints such as water-based paints and metallic paints.

[Prior Art] In general, paints used for electrostatic painting are broadly divided into solvent-based paints (oil-based paints) with relatively high electrical resistance values and water-based paints (water-based paints) with relatively low electrical resistance values. can be,
Among solvent-based paints, oil-based metallic paints in which metal powder is dispersed are known, and there are three types of paints in total. As described above, since the electrical resistance value of paint differs depending on the type of paint, the method of applying high voltage to the coating machine also differs depending on the type of paint.

In other words, electrostatic coating equipment is used with the paint supply pipe, paint tank, color change valve device, etc. connected to ground to prevent dangers such as ignition and fire outbreaks, but solvent-based paints have relatively large Since it has an electrical resistance value, even if a high voltage is directly applied to the atomizer, the atomizer will not be at ground potential through the paint supply pipe. Therefore, paint sprayers used for solvent-based paints apply a high voltage directly to the sprayer to directly charge the paint particles. (referred to as charging method)
.

On the other hand, water-based paints have a low electrical resistance value, so if a high voltage is applied directly to the paint sprayer, the sprayer will short-circuit to ground potential through the paint in the paint supply pipe, causing the paint particles to become electrically charged. I can't do it. Therefore, in the case of water-based paints, an external electrode is installed radially outward from the paint sprayer, and a high voltage is applied to the external electrode to form a corona discharge area in front of the paint sprayer. The joints are charged while the paint particles sprayed from the inside pass through the corona discharge area (hereinafter, the method of applying a high voltage to the external electrode is referred to as the indirect charging method).

Furthermore, since the metallic paint itself is a solvent-based paint, the electric resistance value of the paint is relatively high, and a direct charging method in which a high voltage is directly applied to a coating machine is often applied.

However, since metallic paints are made by dispersing metal powder in a solvent, when a bridging phenomenon occurs, the electrical resistance value decreases, and the paint in the paint supply pipe connects to the paint machine and the paint tank. Or, there may be a short circuit with the color change valve device. Note that the bridging phenomenon refers to a phenomenon in which a discharge phenomenon occurs between metal powders dispersed in a solvent, and the metal powders are arranged and become electrically conductive.

Therefore, in addition to the above-mentioned direct charging method, some coating machines for use with metallic paints use an indirect charging method using external electrodes to prevent the bridging phenomenon as much as possible.

[Problem to be Solved by the Invention 1] Incidentally, in recent years, attention has been paid to water-based paints instead of solvent-based paints from the viewpoint of pollution prevention and the like. For this reason, in the field of electrostatic coating equipment, a rotary atomizing head-type atomizer for water-based paints is used, and an external electrode is provided on the radial outside of the rotary atomizing head to support the application of water-based paints. The reality is that there are. However, in the indirect charging method using an external electrode, the sprayed paint particles are only charged while passing through a corona discharge region formed by ionization of air near the external electrode. Therefore, even if paint particles sprayed at ground potential pass through the corona discharge region,
It is impossible to charge the particles to the same potential as the voltage applied to the external electrode; for example, even if -90 KV is applied to the external electrode, the charged paint particles are only about -40 KV, which poses the problem of poor coating efficiency. .

Additionally, as mentioned above, since there is a potential difference between the external electrode and the charged paint particles, the charged paint particles are attracted towards the external electrode, resulting in the problem of contaminating the external electrode and the front end of the paint sprayer. There is a point. In particular, when a rotating atomizer head such as a bell-type or disk-type is used as a sprayer, paint particles caught in the negative pressure area generated in front of the rotary atomizer head flow backwards, such as the cover of the sprayer, etc. There is a problem in that it contaminates the

Furthermore, the external charging method using an external electrode requires the electrode to be installed on the outside in the radial direction of the paint sprayer, which increases the size of the paint sprayer, making it less easy to attach to reciprocators, painting robots, etc., and making the entire device larger. The problem is that it becomes complicated.

The present invention has been made in view of the problems of the prior art, and it is an object of the present invention to provide an electrostatic coating device that can apply a direct charging method to conductive paints such as water-based paints and metallic paints. With the goal.

[Means for Solving the Problems] In order to achieve the above object, the present invention provides a cylinder container consisting of a hollow cylindrical sealed cylinder body, the interior of which is defined by a free piston into a paint chamber and an insulating liquid chamber. a paint/cleaning fluid supply means for supplying paint and cleaning fluid to the paint chamber of the cylinder container via a supply pipe line; a switching valve means selectively connected to a container side and a drain side; an insulating liquid supply/discharge means for supplying and discharging an insulating liquid to an insulating liquid chamber of the cylinder container; and an insulating liquid supply/discharge means connected to a paint chamber of the cylinder container. The present invention consists of a coating machine that sprays paint onto an object to be coated, and a high voltage application means that applies a high voltage to the coating machine.

[Effect]

With this configuration, with the switching valve means switched to the cylinder container side, paint is supplied from the paint/cleaning fluid supply means to the cylinder container via the supply pipe line, and then the switching valve means is switched to the cylinder container side. supplying cleaning fluid from the paint/cleaning fluid supply means to clean the inside of the supply pipe line, and then supplying insulating liquid into the insulating liquid chamber of the cylinder container from the insulating fluid supply/discharge means. When the free piston is pressed and the paint in the paint chamber is discharged towards the paint sprayer,
A coating machine to which a high voltage is applied from a high voltage application means sprays paint particles charged by a direct charging method. At this time, since the inside of the paint supply pipe has been cleaned in advance, even if conductive paint is used, there is electrical continuity between the paint sprayer and the paint/cleaning fluid supply means, causing a short circuit to ground potential. You can prevent this from happening.

C Embodiment] Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 and 2.

In the drawings, reference numeral 1 denotes a cylinder container made of a closed cylinder body with a hollow space, and the cylinder container 1 is made of glass material, for example.
It is made of an electrically insulating material such as an insulating resin material, and its inner circumferential surface is finished with a highly accurate mirror finish so that no paint remains on the inner circumferential surface even when the free piston 2 (described later) slides and displaces.

The front end side of the cylinder container 1 is provided with a paint inflow hole I.
A, a paint outlet IB is formed, and an insulating oil inlet IC and an insulating oil outlet ID are formed at the rear end side. Reference numeral 2 denotes a free piston that is fluid-tightly and slidably provided in the cylinder container l, and the free piston 2 allows the paint chamber 3
and an insulating oil chamber 4. Note that the volume of the paint chamber 3 is large enough to secure the paint necessary for one painting operation;
For example, it is set to 200 to 500cc.

5 is a color change valve device constituting a paint/cleaning fluid supply means;
The color change valve device 5 has an air valve 7, a thinner valve 8, and paint valves 9A, 9B for A color, B color, . . . N color on both sides of a manifold 6.
,...9N (totally referred to as paint valves 9), each of these valves is connected to an air source, a thinner tank, a paint tank for each color, etc. via a circulation vibrator. Note that the color change valve device 5 is held at ground potential to ensure safety.

] O is a supply pipe connecting between the manifold 6 of the color change valve device 5 and the paint inlet IA of the cylinder container l, and the supply pipe 10 is a long pipe. A washable cleaning/next color supply pump 11 is provided in the middle of the supply pipe 10, and the pump 11 constitutes the paint/cleaning fluid supply means of the present invention together with the color change valve device 5. held at earth potential.

Reference numeral 12 denotes a three-way valve constituting the switching valve means of the present invention, and the three-way valve 12 is composed of, for example, a three-bottom, three-position electromagnetic directional switching valve.
The outflow side of the supply pipe 10 and the boat C are connected to a drain tank 14 via a drain pipe 13, respectively. Then, the three-way valve 12 switches the boat A according to the switching operation.
and Boat B, and Boat A and Boat C are selectively connected.

and an insulating oil supply pipe 8 whose one end opens into the insulating oil tank 17 and whose other end is connected to the insulating oil inlet IC of the cylinder container 1, and an insulating oil supply pipe 18 provided midway through the insulating oil supply pipe 18. an insulating oil discharge pipe 20 whose one end is connected to the insulating oil outlet ID of the cylinder container 1 and whose other end is open to the insulating oil tank 17;
The insulating oil discharge pipe 20 is generally composed of a two-way valve 21 which is a two-bottom, two-position electromagnetic directional switching valve provided in the middle of the insulating oil discharge pipe 20. The insulating oil supply and discharge device 15 configured as described above drives the paint discharge pump 19 with the two-way valve 21 closed, and supplies the insulating oil 16 to the insulating oil chamber 4 of the cylinder container 1. As a result, the free piston 2 is displaced to the right position 2' shown by the two-dot chain line, and the paint in the paint chamber 3 is discharged. Furthermore, if the paint chamber 3 of the cylinder container 1 is filled with paint with the three-way valve 21 open, the free piston 2 can be moved toward the left side indicated by the two-dot chain line while the insulating oil in the insulating oil chamber 4 is being discharged. It can be displaced up to position 2''.

Next, 22 is a rotary atomizing head type atomizer having a rotary atomizing head 22A, for example, and the atomizing machine 22 is supplied by rotating the rotary atomizing head 22A at high speed with an air motor installed inside the atomizing machine 22. The paint is rotary atomized.

Reference numeral 23 indicates a relatively short discharge pipe, one end of which is connected to the paint outlet IB of the cylinder container l, and the other end connected to the atomizer 22. Reference numeral 24 denotes a coating control valve installed in the middle of the discharge pipe 23, and the coating control valve 25 is composed of, for example, a 3-bot, 3-position electromagnetic directional switching valve. B is connected to the coating machine 22, and boat C is connected to the drain tank 14 via a drain pipe 25 and a drain valve 26, respectively. The coating control valve 24 selectively connects boat A and boat B and boat A and boat C according to the switching operation thereof, and also controls the spraying of paint from the coating machine 22. . The drain valve 26 is composed of a two-bottom, two-position electromagnetic directional switching valve, which is opened only during cleaning operations and is normally closed.

Furthermore, 27 indicates a high voltage generator, and the high voltage generator 27 generates a high voltage of, for example, -40 to -120 KV, and applies the high voltage to the coating machine 22 via a high voltage cable 28. be.

In the figure, reference numeral 29 indicates an electric motor, and 30 indicates a clutch. By switching the clutch 30, the cleaning/next color supply pump 11 and the paint discharge pump 19 are driven.

The present embodiment is constructed as described above, and its operation will now be described with reference to FIG. 2.

First, the first step is a step of supplying color A paint to the paint chamber 3 of the cylinder container 1. Therefore, the boats A and B of the three-way valve 12 are brought into communication, and the two-way valve 21
Open the valve. Note that the coating control valve 24 is kept in a closed state. Now, in this state, the A color paint valve 9A of the color change valve device 5 is opened, and the cleaning/next color supply pump 1 is opened.
1, the A color paint is supplied to the supply pipe 10 and the three-way valve 12.
At this time, the insulating oil in the insulating oil chamber 4 is discharged, so the free piston 2 is displaced to the left position 2'' and is filled by a predetermined amount (for example, 3
00 cc) of A color paint is stored. In addition, two-way valve 2
If valve 1 is closed midway, the discharge of the insulating oil is stopped, so the displacement of the free piston 2 is also stopped, and filling of the paint can be completed at that position.

The second process is to apply color A paint to the rotary atomizing head 22A of the coating machine 22.
It is about the same as a fludge unit where it is discharged for a moment. For this reason,
The painting control valve 24 is communicated from boat A to boat B, the two-way valve 21 is closed, and the A color paint valve 9A is momentarily opened as in the first step, and cleaning and next color supply are performed. The pump 11 is driven for a moment. As a result, the discharge pipe 23 is filled with the color A paint, and the color A paint is also supplied to the rotary atomizing head 23A, completing preparation for painting.

The third step is a supply pipe cleaning step for cleaning the A color paint remaining in the supply pipe 10. For this purpose, the three-way valve 12 is switched to a state where boats A and C are in communication, the cleaning/next color supply pump 11 is driven, and the air valve 7 and thinner valve 8 of the color change valve device 5 are opened alternately. The supply pipe line 10, the pump 11, etc. are cleaned, and the drained liquid is made to flow out from the three-way valve 12 through the drain line 13 to the drain tank 14.

As a result, the A color paint in the supply pipe IO becomes completely empty, and even if the A color paint is a water-based paint or a metallic light paint, a high voltage is applied to the coating machine 22 in the coating process described later. This prevents an accident in which a short circuit occurs between the coating machine 22, the color change valve device 5, and the cleaning/next color supply pump 11.

The fourth step is a coating step with A color paint. In this painting process, the painting control valve 24 is switched so that boat A and boat B communicate with each other, the three-way valve 12 and the two-way valve 21 are kept closed, and the high voltage generator 27 is connected to the painting machine 22. Apply voltage. In this state, when the paint discharge pump 19 is driven, the insulating oil 16 in the insulating oil tank 17 is supplied to the insulating oil chamber 4 of the cylinder container 1, displacing the free piston 2 to the right in the figure.

As a result, the A color paint in the paint chamber 3 is supplied to the paint machine 22 via the discharge pipe 23 and the paint control valve 24, and
The paint particles are directly charged by the high voltage applied to the rotary atomizer head 22A, and charged paint particles are atomized from the rotary atomizer head 22A and applied to the object along the lines of electric force. At this time, the high voltage applied to the atomizer 22 is passed through the discharge pipe 23 to the cylinder container 1.
It acts so that the inside of the paint chamber 3 and the boat B of the three-way valve 12 are at the same potential. However, since the cylinder container 1 itself is made of an insulating material and its insulating oil chamber 4 is only filled with insulating oil, high voltage does not act on the insulating oil supply/discharge device 15 side. Furthermore, as mentioned earlier, since the supply pipe 10 between the boat A of the three-way valve 12 and the color change valve device 5 has been cleaned, there is no risk that the paint machine 22 will be short-circuited to the ground potential. It is something.

Now, after completing the painting of color A as described above, the fifth
This step is a cylinder container cleaning step in which the inside of the paint chamber 3 of the cylinder container 1 is cleaned. In this process, the two-way valve 21 is closed, the free piston 2 is held at the right position 2', the three-way valve 12 is switched to the position where boats A and B are connected, and the painting control valve 24 is switched to the position where boats A and B are connected. At the same time, the drain valve 26 is opened.

In this state, the cleaning/next color supply pump 11 is driven, and the air valve 7 and thinner valve 8 of the color change valve device 5 are opened alternately. As a result, the cleaning fluid consisting of air and thinner is supplied to the supply pipe 10, the three-way valve 12, and the paint chamber 3 of the cylinder container 1. Discharge pipe 23, coating control valve 24, drain pipe 25, drain valve 2
6 are sequentially valved to circulate and wash the A color paint in the paint chamber 3.

In addition, since the inner circumferential surface of the cylinder container 1 is smoothly mirror-finished, paint does not remain attached to the inner circumferential surface while the free piston 2 is slidingly displaced to the right. The cylinder container 1 can be cleaned while the free piston 2 is held at the right position 2'.

Furthermore, the sixth step is a coating machine cleaning process in which the coating machine 22 is cleaned. In this process, the painting control valve 24 is switched to the position where boats A and B are connected, and as in the cylinder container cleaning process described above, the cleaning/next color supply pump 11 is driven, and the air valve 7 of the color change valve device 5 is driven. and the thinner valve 8 are opened alternately.

As a result, the cleaning fluid consisting of air and thinner is supplied to the supply pipe 1.
0. Three-way valve 12. Paint chamber 3 of cylinder container l, discharge pipe 23. supplied to the coating machine 22 via the coating control valve 24;
The inside of the coating machine 22 and its rotating atomizing head 22A are cleaned together with the inside of the discharge pipe 23.

With the above, the painting work with color A paint has been completed, and if you want to continue painting work with color B paint,
The above-described first to sixth steps may be repeated using the colored paint valve 9B. The same applies to C-color to N-color paints.

As described above, according to the present embodiment, the cylinder container 1 and the three-way valve 12 are separated, and the paint machine 22 and the color change valve device 5. Washing·
Since it can be electrically insulated from the next color supply pump 11, even when using conductive paint such as water-based paint or metallic paint, the direct charging method can be used while applying a high voltage to the coating machine 22. Painting is possible. For this reason, the coating efficiency is significantly increased compared to the indirect charging method such as the conventional technology, and the coating installation is easy! ! 22 can be prevented from being contaminated.

Also, when performing painting work while sequentially changing the colors of multi-color paints from A to N colors, there is no need for new painting techniques, and the conventional color change valve device 5 can be used to completely eliminate the need for solvent-based paints. Cleaning operations can be carried out using similar means.

Further, the electrostatic coating machine is not limited to the rotary atomizing head type coating machine 22 according to the embodiment, but can be any electrostatic coating machine applicable to solvent-based paint, such as an air atomization type electrostatic spray gun, a disk type static coating machine, etc. An electric coating machine can also be used, and all the problems of water-based paints can be overcome.

In the embodiment, the paint/cleaning fluid supply means has been described as being composed of the color change valve device 5 and the cleaning/next color supply pump 11, but if the circulation pipe side has high pressure, the pressure A regulator may be used, and if a pressure regulator is provided between the air, thinner, and each color circulation pipe and the color change valve device 5, the pump 11 itself may be omitted.

In addition, a discharge pipe 2 is connected between the cylinder container 1 and the coating machine 22.
3, and the coating control valve 24 is provided between them, but the discharge pipe 23 may be abolished and the cylinder container 1 and the coating machine 22 may be integrated. The control valve 24 can also be built into the coating machine 22.

Furthermore, the insulating liquid supply and discharge means is not limited to the configuration of the embodiment, and for example, a two-way valve or a flow rate control valve may be provided on the outflow side of the paint discharge pump 19 on the insulating oil supply and discharge pipe 18 side. .

〔Effect of the invention〕

The electrostatic coating device according to the present invention is as described in detail above, and since the supply pipe line between the paint/cleaning fluid supply means and the switching valve means is configured to be washable, it is possible to prevent conductive paint from being applied. By applying a direct charging method, there is no risk of the coating machine shorting to ground potential even when painting is performed with high voltage applied to the coating machine, and the coating efficiency is the same as that of solvent-based paints. It also has the effect of making it possible to apply multi-colored paints.

[Brief explanation of drawings]

FIG. 1 is a system diagram showing the overall configuration according to an embodiment of the present invention;
FIG. 2 is an explanatory diagram showing the operation of each part during painting work. 1... Cylinder container, 2... Free piston, 3...
...Paint room, 4...Insulating oil room, 5...Color change valve device,
7...Air valve, 8...Thinner valve, 9...Paint valve,
10... Supply pipe line, 11... Cleaning/next color supply pump, 12... Three-way valve (switching valve device), 13.25...
Drainage pipe line, 15... Insulating oil supply/drainage device, 16... Insulating oil, 17... Insulating oil tank, 18... Insulating oil supply pipe line, 19... Paint discharge pump, 20. ...Insulating oil discharge pipe, 21...Two-way valve, 22...Painting machine, 23...
-Discharge pipe line, 24... Paint control valve, 26... Drain valve, 27... High voltage generator, 28... High voltage cable.

Claims (1)

[Claims] A cylinder container consisting of a hollow cylindrical sealed cylinder body, the interior of which is defined by a free piston into a paint chamber and an insulating liquid chamber, and paint and cleaning fluid are supplied to the paint chamber of the cylinder container via a supply pipe. paint/cleaning fluid supply means;
A switching valve means is provided in the middle of the supply pipe line and selectively connects the paint/cleaning fluid supply means to the cylinder container side and the drain side, and an insulating liquid is provided in the insulating liquid chamber of the cylinder container. an insulating liquid supply and discharge means for supplying and discharging water; a paint machine that is connected to the paint chamber of the cylinder container and that sprays paint onto the object to be coated; and a high voltage application means that applies a high voltage to the paint machine. Electrostatic painting equipment.