JP2791599B2 - Electrostatic coating equipment - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to an electrostatic coating apparatus suitable for electrostatically applying a conductive paint such as a water-based paint or a metallic paint.

[Conventional technology]

Generally, paints used for electrostatic coating are roughly classified into solvent-based paints (oil-based paints) having relatively large electric resistance values and water-based paints (water-based paints) having relatively small electric resistance values. Among them, oil-based metallic paints in which metal powder is dispersed are known, and there are three types of paints as a whole.
As described above, since the paints have different electric resistance values according to their types, the method of applying a high voltage to a coating machine also differs according to the types of paints.

That is, in the electrostatic coating apparatus, the paint supply pipeline, the paint tank, the color changing valve device, and the like are connected to the ground from the viewpoint of prevention of danger such as ignition or fire, but the solvent paint is relatively large. Since it has an electric resistance value, even if a high voltage is directly applied to the coating machine, the coating machine does not reach the ground potential via the paint supply pipe. Therefore, the coating machine used for solvent-based paint, apply a high voltage directly to the coating machine,
The paint particles are directly charged (hereinafter, a method of directly applying a high voltage to a coating machine is referred to as a direct charging method).

On the other hand, water-based paints have a small electric resistance, so if a high voltage is applied directly to the painter, the painter will be short-circuited to ground potential via the paint in the paint supply line, and the paint particles will be charged. I can't let it. Therefore, in the case of a water-based paint, an external electrode is provided at a position radially outside the coating machine, a high voltage is applied to the external electrode, and a corona discharge region is formed in front of the coating machine. Is indirectly charged while the paint particles sprayed from the same pass through a corona discharge area (hereinafter, a method of applying a high voltage to an external electrode is referred to as an indirect charging method).

Furthermore, since the metallic paint is itself a solvent paint, the electrical resistance of the paint is relatively large, and a direct charging system in which a high voltage is directly applied to a coating machine is often used.

However, since metallic paint is a dispersion of metal powder in a solvent, the electrical resistance decreases when a bridging phenomenon occurs, and the paint machine and paint tank pass through the paint in the paint supply pipe. Alternatively, a short circuit may occur with the color changing valve device. Note that the bridge phenomenon is a phenomenon in which a discharge phenomenon occurs between metal powders dispersed in a solvent, and the metal powders are arranged to be in a conductive state.

Therefore, as a coating machine applied to a metallic paint, there is known a coating machine which uses an indirect charging system using an external electrode in addition to the above-described direct charging system to prevent the occurrence of a bridge phenomenon as much as possible.

[Problems to be solved by the invention]

By the way, in recent years, from the viewpoint of pollution prevention and the like, water-based paints have been paid attention instead of solvent-based paints. For this reason, in the field of electrostatic coating equipment, a rotary atomizing head type coating machine for water-based paint is used, and an external electrode is provided on the radially outer side of the rotary atomizing head to cope with the coating of water-based paint. That is the fact. However, the indirect charging method using an external electrode only charges the sprayed paint particles while passing through a corona discharge region formed by ionization of air near the external electrode. For this reason, even if the paint particles sprayed at the ground potential pass through the corona discharge region, it is impossible to charge to the same potential as the voltage applied to the external electrode, for example, by applying -90 KV to the external electrode. However, there is a problem that the charged paint particles are about -40 KV, and the coating efficiency is poor.

In addition, as described above, since there is a potential difference between the external electrode and the charged paint particles, the charged paint particles are attracted toward the external electrode, and contaminate the external electrode and the front end of the coating machine. There is a point. In particular, when a rotary atomizing head such as a bell type or a disk type is used as a coating machine, the paint particles caught in the negative pressure region generated in front of the rotary atomizing head flow backward to cover the coating machine. There is a problem that it is soiled.

In addition, the external charging method using external electrodes requires the electrodes to be mounted on the outside of the coating machine in the radial direction, so that the coating machine becomes large, which makes it inferior to reciprocators and coating robots. There is a problem that it becomes complicated.

SUMMARY OF THE INVENTION The present invention has been made in view of such problems of the related art, and provides an electrostatic coating apparatus capable of applying a direct charging method to conductive paints such as water-based paints and metallic paints. With the goal.

[Means for solving the problem]

In order to achieve the above-described problems, the electrostatic coating apparatus according to the present invention includes a hollow cylindrical closed cylinder body, and a cylinder container whose interior is defined by a free piston into a paint chamber and an insulating liquid chamber, A color changing valve device for supplying a paint and a cleaning fluid to the paint chamber of the cylinder via a supply pipe; and a paint change valve provided in the middle of the supply pipe for supplying the paint or the cleaning fluid to the paint chamber of the cylinder. Sometimes, the color change valve device and the paint chamber are connected, and the first change valve means for connecting the color change valve device to the drainage tank when the supply line is washed, and an insulating liquid tank for storing the insulating liquid, Provided in the middle of an insulating liquid supply pipe communicating between the insulating liquid tank and the insulating liquid chamber of the cylinder container, displacing the free piston by supplying the insulating liquid to the insulating liquid chamber during coating, Before A paint discharge pump for discharging paint in the paint chamber, and provided in the middle of an insulating liquid discharge line communicating between the insulating liquid chamber and the insulating liquid tank of the cylinder container, and provided from the color changing valve device to the cylinder container. When the paint is supplied to the paint chamber, the second switching valve means for connecting the insulating liquid chamber to the insulating liquid tank and the paint chamber of the cylinder container are connected to spray the paint in the paint chamber onto the object to be coated. A coating machine which is provided between the coating machine and the coating chamber of the cylinder container, and connects the coating chamber to the coating machine at the time of coating and at the time of cleaning the coating machine; and at the time of cleaning the cylinder container, And a high voltage applying means for applying a high voltage to the coating machine at the time of coating.

[Action]

In the electrostatic coating apparatus configured as described above, it is assumed that the supply line, the coating chamber of the cylinder container, and the front color in the coating machine have been cleaned in advance.

In this state, in order to perform the painting operation using the next color paint, the first switching valve means is switched to the cylinder container side, and the second switching valve means is connected to the insulating liquid chamber and the insulating liquid tank of the cylinder container. In the communication state, the next color paint is supplied from the color changing valve device into the paint chamber of the cylinder container via the supply pipe.

Next, in a state where the second switching valve means is closed and the first switching valve means is switched to the drain tank side, a cleaning fluid is supplied from the color changing valve device to clean the inside of the supply pipe. .

Next, the third switching valve means is brought into a state of communicating the paint chamber of the cylinder container with the coating machine, and an insulating fluid is supplied to the insulating liquid chamber of the cylinder container by the paint discharge pump to press the free piston.

As a result, the paint in the paint chamber of the cylinder container becomes the third
Is supplied to the coating machine through the switching valve means, and the coating apparatus to which the high voltage is applied from the high voltage applying means sprays the paint particles charged by the direct charging method toward the object to be coated.

At this time, since the inside of the paint supply pipe has been washed in advance,
Even if the conductive paint is used, it is possible to prevent a situation where the coating machine is electrically connected to the color changing valve device and the coating machine is short-circuited to the ground potential.

Next, when the coating by the coating machine is completed, the coating chamber of the cylinder container is washed. For this reason, the first switching valve means is switched so that the color changing valve device and the paint chamber communicate with each other.
The third switching valve means is switched so that the paint chamber communicates with the drainage tank, and a cleaning fluid is supplied from the color changing valve device to clean the paint chamber of the cylinder container.

Further, the pre-color paint remaining in the coating machine is washed. For this reason, the third switching valve means is set in a state in which the paint chamber of the cylinder container is in communication with the coating machine, and a cleaning fluid is supplied from the color changing valve device to the coating machine to wash the coating machine. This makes it possible to prepare for the next coating.

〔Example〕

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIG. 1 and FIG.

In the drawings, reference numeral 1 denotes a cylinder container formed of a hollow cylindrical closed cylinder body. The cylinder container 1 is formed of an electrically insulating material such as a glass material, an insulating resin material, and the like, and a free piston 2 described below slides and displaces. Even so, the inner peripheral surface is mirror-finished with high precision so that no paint remains on the inner peripheral surface. A paint inlet 1A and a paint outlet 1B are formed at the front end of the cylinder container 1, and an insulating oil inlet 1C and an insulating oil outlet 1D are formed at the rear end. Reference numeral 2 denotes a free piston slidably provided in the cylinder container 1 in a liquid-tight manner. The free piston 2 defines a paint chamber 3 and an insulating oil chamber 4. The volume of the paint chamber 3 is set to a size that secures paint required for one painting operation, for example, 200 to 500 cc.

5 is a color change valve device, and the color change valve device 5 is a manifold 6
, N-color paint valves 9A, 9B,... 9N (collectively referred to as paint valves 9) on both sides of the air valve 7, thinner valve 8,. Is connected to an air source, a thinner tank, a paint tank of each color, and the like via a circulation pipe. Note that the color changing valve device 5 is maintained at the ground potential for ensuring safety.

Reference numeral 10 denotes a supply pipe connecting between the manifold 6 of the color changing valve device 5 and the paint inlet 1A of the cylinder container 1, and the supply pipe 10 is a long pipe. A washing / next color supply pump 11 capable of washing is provided in the middle of the supply line 10, and the pump 11 is maintained at the ground potential.

12 is a three-way valve constituting the first switching valve means of the present invention,
The three-way valve 12 is composed of, for example, a three-port three-position electromagnetic directional control valve. Port A is the inlet side of the supply line 10, port B is the outlet side of the supply line 10, and port C is the drain line. Each of them is connected to the drainage tank 14 via 13. And
The three-way valve 12 selectively connects ports A and B and ports A and C in accordance with the switching operation.

Reference numeral 15 denotes an insulating oil supply device.
It comprises an insulating oil tank 17 described later, an insulating oil supply line 18, a paint discharge pump 19, an insulating oil discharge line 20, a two-way valve 21, and the like.

That is, reference numeral 17 denotes an insulating oil tank, which stores insulating oil 16 such as hydraulic oil and thinner. The insulating oil supply pipe 18 has one end open into the insulating oil tank 17 and the other end connected to the insulating oil inlet 1C of the cylinder container 1. Can be supplied. Reference numeral 19 denotes a paint discharge pump. The paint discharge pump 19 is provided in the middle of the insulating oil supply pipe 18 and supplies insulating oil to the insulating oil chamber 4 of the cylinder container 1 at the time of coating, and the free piston 2 It is displaced to the side.

On the other hand, reference numeral 20 denotes an insulating oil discharge line.
Has one end connected to the insulating oil outlet 1D of the cylinder container 1 and the other end opened to the insulating oil tank 17. Reference numeral 21 denotes a two-way valve constituting a second switching valve means according to the present invention.
Reference numeral 21 denotes a two-port, two-position electromagnetic directional control valve provided in the middle of the insulating oil discharge line 20, which is normally closed and opened when the paint is supplied to the paint chamber 3 of the cylinder container 1. The valve is discharged to discharge the insulating oil 16 in the insulating oil chamber 4 to the insulating oil tank 17.

And the insulating oil supply / discharge device 15 thus configured is
Drive the paint discharge pump 19 with the two-way valve 21 closed,
By supplying the insulating oil 16 to the insulating oil chamber 4 of the cylinder container 1, the free piston 2 is displaced to a right position 2 'shown by a two-dot chain line, and the paint in the paint chamber 3 is discharged. . When the paint is filled in the paint chamber 3 of the cylinder container 1 with the two-way valve 21 opened, the free piston 2 is indicated by a two-dot chain line while discharging the insulating oil in the insulating oil chamber 4. To position 2 ".

Next, 22 is a rotary atomizing head type coating machine having, for example, a rotary atomizing head 22A, and the coating machine 22 is supplied by rotating the rotary atomizing head 22A at a high speed by an air motor provided therein. Paint is made to rotate and atomize.

Reference numeral 23 denotes a relatively short discharge pipe. One end of the discharge pipe 23 is connected to the paint outlet 1B of the cylinder container 1, and the other end is connected to the coating machine 22. 24 is the discharge pipe
A paint control valve constituting a third switching valve means of the present invention provided in the middle of 23. The paint control valve 25 is, for example, a 3 port 3
Port A is a paint outlet 1A, port B is a coating machine 22, and port C is a drainage line.
25, are connected to the drainage tank 14 via the drainage valve 26, respectively. The coating control valve 24 selectively connects the port A to the port B and the port A to the port C in accordance with the switching operation, and controls the spraying of the paint from the coating machine 22. . The drain valve 26 comprises a two-port, two-position electromagnetic directional control valve, which is opened only during the cleaning operation and is normally closed.

Reference numeral 27 denotes a high voltage generator, which 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. is there.

In the figure, reference numeral 29 denotes an electric motor, and reference numeral 30 denotes a clutch. The switching of the clutch 30 drives the cleaning / next color supply pump 11 and the paint discharge pump 19.

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

First, the first step is a step of supplying an A-color paint to the paint chamber 3 of the cylinder container 1. For this reason, the port A and the port B of the three-way valve 12 are brought into a communicating state, and the two-way valve 21 is brought into an open state. Note that the coating control valve 24 is in a closed state. In this state, when the A color paint valve 9A of the color changing valve device 5 is opened and the cleaning / next color supply pump 11 is driven, the A color paint is supplied to the cylinder via the supply pipe 10 and the three-way valve 12. Filled in the paint chamber 3 of the container 1, the insulating oil chamber 4
The free piston 2 is displaced to the left position 2 "due to the discharge of the insulating oil therein, and a predetermined amount (for example, 300 cc) of the A color paint is stored. The two-way valve 21 is closed halfway. Then, since the discharge of the insulating oil stops, the displacement of the free piston 2 also stops, and the filling of the paint can be terminated at that position.

The second step is a flash step in which the A-color paint is ejected momentarily from the rotary atomizing head 22A of the coating machine 22. For this reason, the paint control valve 24 is communicated from the port A to the port B, and the two-way valve 21 is closed.
The color paint valve 9A is momentarily opened, and the washing / next color supply pump 11 is momentarily driven. As a result, the color A paint is discharged from the discharge line 23.
And the rotary Atomizing head 23A is also supplied with the A-color paint, and the preparation for painting is completed.

The third step is a supply pipe cleaning step of cleaning the A color paint remaining in the supply pipe 10. Therefore, the three-way valve 12 is switched to a state in which the port A and the port C communicate with each other, the cleaning / next color supply pump 11 is driven, and the air valve 7 of the color changing valve device 5 is operated.
And the thinner valve 8 are alternately opened, and the supply line 10, the pump
11 and the like are washed, and the drainage is caused to flow from the three-way valve 12 to the drainage tank 14 via the drainage line 13.

As a result, the A-color paint in the supply conduit 10 becomes completely empty, and when the A-color paint is a water-based paint or a metallic light paint, even if a high voltage is applied to the coating machine 22 in a later-described coating process. , The coating machine 22 and the color changing valve device 5,
An accident in which a short circuit occurs between the next color supply pump 11 and the next color supply pump 11 can be prevented.

The fourth step is a step of applying the A color paint. In this coating process, the coating control valve 24 is switched so that port A and port B communicate with each other, and the three-way valve 12 and the two-way valve 21 are kept closed. 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 and displaces the free piston 2 to the right in the drawing. The A-color paint is discharged quantitatively in the same amount as the insulating oil supplied to the insulating oil chamber 4.

As a result, the A-color paint in the paint chamber 3 is supplied to the coating machine 22 via the discharge pipe 23 and the coating control valve 24, and is adjusted and charged by the high voltage applied to the coating machine 22, and is rotated and atomized. Head 22
From A, charged paint particles are sprayed and applied to the object along the lines of electric force. At this time, the high voltage applied to the coating machine 22 acts so as to have the same potential between the interior of the coating chamber 3 of the cylinder container 1 and the port B of the three-way valve 12 via the discharge pipe 23. However, since the cylinder container 1 itself is formed of an insulating material and the insulating oil chamber 4 is merely filled with insulating oil, a high voltage does not act on the insulating oil supply / discharge device 15 side. Also, as described above, the port A of the three-way valve 12
Since the supply line 10 between the first and second color changing valve devices 5 is cleaned, there is no possibility that the coating machine 22 is short-circuited to the ground potential.

When the coating of the color A is completed as described above, the fifth step is a cylinder container cleaning step of cleaning the inside of the paint chamber 3 of the cylinder container 1. In this step, 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 communication position between the port A and the port B, and the painting control valve 24 is switched to the port A. And the port C, and the drain valve 26 is opened. In this state, the cleaning / next color supply pump 11 is driven, and the air valve 7 and the thinner valve 8 of the color changing valve device 5 are alternately opened. As a result, the cleaning fluid consisting of air and thinner flows through the supply pipe 10, the three-way valve 12, the paint chamber 3 of the cylinder container 1, the discharge pipe 23, the coating control valve 24, the drain pipe 25, and the drain valve 26 in order. Circulated through
The A color paint in the paint chamber 3 is washed. In addition, since the inner peripheral surface of the cylinder container 1 is smoothly mirror-finished,
During the sliding displacement of the free piston 2 to the right, no paint remains on the inner peripheral surface thereof, and the cylinder container 1 is cleaned while the free piston 2 is held at the right position 2 '. Can be performed.

Further, the sixth step is a coating machine cleaning step of cleaning the coating machine 22. In this step, the coating control valve 24 is switched to the communication position between the port A and the port B to drive the cleaning / next color supply pump 11 and the air valve 7 of the color changing valve device 5 in the same manner as in the cylinder container cleaning step described above. And the thinner valve 8 are alternately opened. As a result, the cleaning fluid consisting of air and thinner is supplied to the supply line 10, the three-way valve 12, the paint chamber 3 of the cylinder container 1, the discharge line 2
3, is supplied to the coating machine 22 through the coating control valve 24,
The inside of the coating machine 22 and its rotary atomizing head 22A are washed together with the inside of the coating machine 23.

As described above, the painting work of the A color paint is completed, and when the painting work of the B color paint is subsequently performed,
The first to sixth steps described above may be repeated using the B color paint valve 9B. The same applies to paints of colors C to N.

As described above, according to the present embodiment, the coating machine 22 and the color changing valve device 5 and the washing / next color supply pump 11 are electrically insulated from the cylinder container 1 and the three-way valve 12, and The insulating oil chamber 4 of the cylinder container 1 is filled with insulating oil,
And the paint discharge pump 19 and the two-way valve 21 of the insulating oil supply device 15 can also be electrically insulated. Therefore, in the present embodiment, even when a conductive paint such as a water-based paint or a metallic paint is used as the paint, it is possible to perform painting by a direct charging method while applying a high voltage to the painting machine 22. For this reason, the coating efficiency can be significantly increased as compared with the indirect charging system as in the prior art, and the coating machine 22 can be prevented from being stained.

Further, even when the coating operation is performed while sequentially changing the colors of the multicolor paints of A to N colors, a new coating technique is not required, and the color change valve device 5 according to the prior art is used to completely remove the solvent-based paint. The cleaning operation can be performed by the same means.

Further, since the paint discharge pump 19 is used as means for discharging paint from the paint chamber 3 of the cylinder container 1, the same amount of insulating oil supplied to the insulating oil chamber 4 by the paint discharge pump 19 is used. The paint can be discharged, and by using a positive displacement pump as the paint discharge pump 19, the paint can be discharged from the paint chamber 3 to the coating machine 22 in a constant amount.

Furthermore, the electrostatic spraying machine is not limited to the rotary atomizing head type spraying machine 22 according to the embodiment, but any electrostatic spraying machine applicable to solvent-based paints, for example, an air atomizing electrostatic spray gun, a disk type static spraying machine, etc. An electrocoating machine or the like can also be used, and all the problems of the water-based paint can be overcome.

In the embodiment, the paint / washing fluid supply means is described as being constituted by the color changing valve device 5 and the washing / next color supply pump 11. However, when the circulation pipe side has a high pressure, the pump 11 is replaced with the pressure. A regulator may be used, and when a pressure regulator is provided between the color change valve device 5 and the air, thinner and each color circulation pipe, the pump 11 itself may be omitted.

Further, a discharge pipe 23 is provided between the cylinder container 1 and the coating machine 22.
It has been described that the paint control valve 24 is provided during this. However, the discharge pipe 23 may be omitted and the cylinder container 1 and the coating machine 22 may be integrated. The valve 24 can also be built into the coating machine 22.

Further, the insulating liquid supply / discharge means is not limited to the configuration of the embodiment. For example, a two-way valve or a flow control valve may be provided on the outflow side of the paint discharge pump 19 on the insulating oil supply / discharge conduit 18 side. .

〔The invention's effect〕

The electrostatic coating apparatus according to the present invention is as described in detail above. After supplying the paint to the paint chamber of the cylinder container, the electrostatic coating apparatus is provided in the supply pipe between the color changing valve device and the first switching valve means. The paint remaining in the cylinder container is electrically insulated by washing the paint remaining in the cylinder container, and the insulating oil chamber of the cylinder container is supplied with the insulating oil by using the paint discharge pump and the second switching valve means. Since the coating is performed in a state of being electrically insulated, the direct charging method is applied to the conductive paint, and even if the coating work is performed while applying a high voltage to the coating machine, the coating machine remains at the ground potential. There is no danger of short-circuiting, and the same coating efficiency as that of the solvent-based paint can be obtained.

Further, since the paint discharge pump is used as a means for discharging paint from the paint chamber of the cylinder container, by controlling the supply amount of the insulating oil supplied to the insulating oil chamber by the paint discharge pump, It is possible to discharge the paint quantitatively to the coating machine.

Further, the paint chamber of the cylinder container, the coating machine, etc. can be cleaned each time using the color change valve device and the third switching valve means after the completion of the painting work with the previous color paint,
This has the effect of making it possible to apply a multicolor paint.

[Brief description of the drawings]

FIG. 1 is a system diagram showing an overall configuration according to an embodiment of the present invention,
FIG. 2 is an explanatory view showing the operation of each part during the painting operation. 1 ... cylinder container, 2 ... free piston, 3 ... paint room,
4 ... Insulating oil chamber, 5 ... Color change valve device, 7 ... Air valve, 8 ... Thinner valve, 9 ... Paint valve, 10 ... Supply line, 11 ... Washing / next color supply pump, 12 ... Three-way valve (switching valve) Equipment), 13,25… Drain line, 15… Insulation oil supply / drain device, 16… Insulation oil, 17… Insulation oil tank, 18… Insulation oil supply line, 19… Paint discharge pump, 20… Insulation oil discharge Pipe line, 21: two-way valve, 22: coating machine, 23: discharge line, 24: coating control valve, 26: drain valve, 27: high voltage generator, 28: high voltage cable.

Claims (1)

(57) [Claims] 1. A cylinder container comprising a hollow cylindrical closed cylinder body, the interior of which is defined by a free piston into a paint chamber and an insulating liquid chamber, and a paint chamber provided in the cylinder chamber via a supply pipe. And a color changing valve device for supplying a cleaning fluid, provided in the middle of the supply pipe, and connecting the color changing valve device and the paint chamber when supplying a paint or a cleaning fluid to the paint chamber of the cylinder container, A first switching valve means for connecting the color changing valve device to a drainage tank when cleaning the supply conduit; an insulating liquid tank for storing an insulating liquid; and an insulating liquid chamber of the cylinder container. A paint discharge pump that is provided in the middle of an insulating liquid supply pipe that communicates between them, displaces the free piston by supplying insulating liquid to the insulating liquid chamber during painting, and discharges paint in the paint chamber. Is provided in the middle of an insulating liquid discharge pipe communicating between the insulating liquid chamber of the cylinder container and the insulating liquid tank, and when the paint is supplied from the color changing valve device to the paint chamber of the cylinder container, Second switching valve means for connecting the insulating liquid chamber to the insulating liquid tank, a coating machine connected to the coating chamber of the cylinder container, and spraying the coating material in the coating chamber onto an object to be coated, the coating machine and the cylinder A third switch provided between the paint chamber of the container and connecting the paint chamber to a paint machine at the time of painting and washing the paint machine, and connecting the paint chamber to a drain tank at the time of washing the cylinder vessel; An electrostatic coating apparatus comprising: valve means; and high voltage applying means for applying a high voltage to the coating machine during coating.