JP2934849B2 - Paint insulation equipment in electrostatic coating - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a paint insulating device for electrostatic coating, and more particularly to a paint insulating device for performing electrostatic coating using a conductive paint such as a water-based paint.

[0002]

2. Description of the Related Art Conventionally, in electrostatic coating, an organic solvent-based coating (oil-based coating) has been used from the viewpoint of coating efficiency and the like. However, in addition to the problem of air pollution, these paints are toxic and flammable.Therefore, many restrictions are imposed by the Fire Service Law and so on. Have been. On the other hand, water-based (aqueous) paints are preferred as various kinds of paints because of their low toxicity and flammability. However, since water-based paints are conductive paints, in order to electrostatically paint them, it is necessary to sufficiently insulate the paint supply system, maintain the applied voltage at the paint spraying section, and sufficiently charge the paints. There is. In view of this, various studies have been made on this point, but no effective means has been proposed to date. However, as a method of insulating a water-based paint in electrostatic coating, there is a method of injecting paint from a conductive paint supply source into the hollow body from the upper end of the insulating closed hollow body and bringing the paint in the hollow body into contact with the wall of the hollow body. An insulating method in which a high voltage applied to an electrode is prevented from being discharged to a conductive paint supply source by spraying the paint downward without spraying the paint (see JP-B-56-3108). I have. Specifically, "inside an insulating hollow body having a paint inflow hole at an upper end and a paint outflow hole at a lower end, and being inclined toward the center of the hollow body at the upper end thereof. In addition, a plurality of insulating annular baffles having holes in the center are arranged at appropriate intervals in the vertical direction, and formed so that the diameter of the holes in the baffles becomes smaller as going downward. A ceiling plate having a surface inclined downward from the center to the outer periphery is provided above the uppermost baffle plate, and a flow-down hole for controlling the flow rate of the paint is formed near the outer periphery of the ceiling plate. Configuration ". And in the case of the above-mentioned insulation method, since the paint is dropped at predetermined intervals in the form of water droplets,
As long as the dripping paint does not wet the wall of the hollow body, the paint can be kept in an insulated state.

[0003]

However, as the hollow body goes downward, the possibility that the paint comes into contact with the inner wall increases, and once it comes into contact, the inner wall of the insulating hollow body becomes conductive. In addition, there is a problem that the dripping paint becomes conductive and the dripping paint adheres to the inner wall of the hollow body, so that an electrostatic effect cannot be obtained by applying the high voltage. Therefore, the present inventor has described the problems of the above-described insulation method and apparatus,
As a result of research and examination, the mechanism that caused the problem was clarified. And, explaining the mechanism,
It is as follows. First, paint is dropped inside the hollow body,
When a part of the paint adheres to the inner wall of the insulating hollow body due to scattering or the like, creeping insulation breakdown occurs on the inner wall of the hollow body due to a high voltage applied to the paint spraying unit, and the adhered paint is also applied with a high voltage. Then, the dripping paint is attracted toward the portion in the high voltage charged state by electrostatic induction, and at the moment of contact with the portion (charged portion), the impact of the collision and the action of the high pressure cause a drop of water. Things scatter and adhere. Then, a creepage leak current occurs again to the paint newly attached to the portion other than the high-voltage charging portion, and the same repetition is performed. Even if it has a shape, the inside becomes conductive for a very short time due to the action of the high pressure, and acts so that the paint that cannot be insulated can not be substantially insulated. Therefore, the present inventor has determined that the coating can be easily insulated by preventing the above mechanism. SUMMARY OF THE INVENTION The present invention has been made in view of the above points, and an object thereof is to provide a paint insulating device capable of insulating a conductive paint such as a water-based paint used in electrostatic coating. It is in.

[0004]

According to the present invention, there is provided a paint insulating apparatus in electrostatic coating according to the present invention for achieving the above object, wherein a liquid paint supplied from a conductive paint supply source is converted into a hollow paint. The paint is dropped from the paint dropping part provided at the upper part toward the lower part of the paint drop and the high voltage of the high voltage applying part for electrostatic coating can prevent the paint from adhering to the inner wall surface of the hollow body. A paint insulating device for electrostatic coating, wherein the paint dripping section includes a plurality of dripping grooves that divide the paint blown upward from a central portion in a circumferential direction, and the hollow body is made of an insulating material, A potential rise preventing portion provided with a grounded electrode made of a conductive material is provided at a position above the dripping paint flow lower part and at least on the outer periphery of the lower part of the hollow body.

Here, as the hollow body having an insulating property,
Usually, a plurality of bottomed containers provided with a hole for dropping paint in the center are formed by superimposing a plurality of containers in the vertical direction, and the outer peripheral portion of each bottomed container can be grounded. The dropping hole may be formed in a gear shape. Further, a configuration may be employed in which a paint dropping portion for shunting and dropping paint is provided above the insulating hollow body, and the diameter of the paint dropping hole of the bottomed container is made larger than the average diameter of the paint dropping portion. Furthermore, as the insulating hollow body, a configuration in which a bottomed container having a larger hole diameter than the upper stage is provided in the middle, or a configuration in which the insulating hollow body is formed in a hermetically sealed manner may be employed. The potential rise preventing portion means the grounded electrode and the hollow body wall which is in contact with the electrode and has an insulating property.

According to the present invention, there is provided a paint insulating apparatus for electrostatic coating in which a liquid paint supplied from a conductive paint supply source is dropped from a paint dropping portion provided on an upper portion of a hollow body toward a lower portion of a dropping paint flow. Then, the paint is insulated by the dropping interval, but the paint adheres to the inner wall of the hollow body, and a part of the paint adheres, and the paint becomes conductive due to a leakage current due to a high voltage applied to the electrostatic coating machine. In this case, the leakage current is induced to the earth side by means such as grounding provided on the outer peripheral wall of the hollow body, and the inner wall of the hollow body located above the same is maintained in an insulated state, and the inner wall of the hollow body is coated with the dripping paint. The high voltage applied to the electrostatic coating machine does not discharge.

[0007]

As is apparent from the above description, according to the paint insulating apparatus for electrostatic coating of the present invention, the insulating hermetically sealed tubular body is caused to have a voltage drop by means such as grounding. This has the effect that discharge to the dripping paint can be prevented. Therefore, the paint insulating device for electrostatic coating according to the present invention has an effect that a conductive paint such as a water-based paint used in electrostatic coating can be insulated. In addition, the outer peripheral wall of the insulating hollow body is grounded or the like to cause a voltage drop at the inner peripheral wall of the insulating hollow body so as to prevent the inside of the insulating hollow body from being charged to a high voltage. This feature has the special effect that the insulation of the dripping paint can be easily and continuously performed. And since the paint dripping part is provided with a plurality of dripping grooves that divide the paint blown upward from the central portion in the circumferential direction, a large amount of paint is dripped at once by dripping the paint from each dripping groove. It is possible,
In addition, it is hardly affected by the flow rate of the paint to be blown out, and the paint can be dropped more uniformly.

[0008]

Preferred embodiments of the present invention will be described below with reference to the drawings. 1 to 9 show an embodiment of the present invention. FIG. 1 is a schematic configuration diagram of an electrostatic coating apparatus, FIG. 2 is a block diagram, FIG. 3 is a schematic cross-sectional view of a paint insulating section, and FIG. FIG. 5 is a perspective view of a paint inflow portion forming a paint insulation portion, FIG.
FIG. 6 is a perspective view of a bottomed container forming a paint insulating portion, and FIGS.
9 shows another embodiment, FIG. 7 is a schematic sectional view of a paint insulating section, and FIGS. 8 and 9 are perspective views of bottomed containers forming the paint insulating section, respectively.

In the present embodiment, roughly, the paint supply unit 1
And a paint insulating unit 2 and a power supply unit 3 so that the paint is insulated and the paint spraying unit 4 can perform electrostatic painting. The paint supply unit 1 includes a paint tank 5
And a stirrer 6 for stirring the mixed paint in the paint tank 5 and a low-pressure pump 7 for supplying the paint in the paint tank 5 to the paint insulating unit 2. The low-pressure pump 7 is driven so that a five-phase pulse motor M can be used to supply a constant amount of paint. The paint insulating section 2 is constituted by an isolator 8 for insulating the paint. The isolator 8 is formed by an insulating sealed cylindrical body (hollow body) 9, and has a paint inflow portion 10 at a center portion of an upper end portion and a dripping paint flow lower portion 11 at a lower end portion. The plurality of (six in the drawing) bottomed containers 9a, 9b,... Made of an insulating material such as polyethylene, polypropylene, polyester, and polycarbonate.
Are vertically superposed and detachably polymerized. Are provided at the bottom centers of the bottomed containers 9a, 9b,... So that the centers of the paint descending holes 12a, 12b,. It is configured to be polymerized. Here, the hole diameters of the paint descending holes 12a, 12b... Are made smaller as they go from the upper container to the lower container, and a container provided with a paint descending hole having a small hole diameter is interposed in the middle. I have. However, if necessary, a configuration may be adopted in which a container provided with a paint-falling hole having a small hole diameter is not interposed on the way (FIG. 7).
reference). Also, the paint drop hole 12 (12a, 12b,...)
.) Usually indicates that the hole end 12 ′ has a plane wave shape (FIGS. 6 and 9).
See). However, it may be a circular hole (see FIG. 8) or the like. Furthermore, ribs (or, particularly, the lowermost 9f of the bottomed containers) are provided inside the bottomed containers 9a, 9b,.
A groove 9 ′ (see FIG. 9) may be provided. Also, electrodes 13a, 13b... Made of a conductive material such as aluminum are attached to the outer periphery of each bottomed container 9a, 9b..., And the electrodes 13a, 13b. I have.
Here, the interval between the electrodes 13a, 13b,... Needs to be an interval at which a high voltage does not discharge to the electrodes from the joint of the bottomed container, and is usually arranged in a band shape at the center of the peripheral surface of each container. Has become. The outer peripheral walls of the bottomed containers 9a, 9b,... Contacting the electrodes 13a, 13b,. 13a, 13b,... Constitutes a potential rise preventing section. Low pressure pump 7 of paint supply unit 1
And the insulating tube 14 are connected to each other. The insulating tube 14 is connected to the paint inflow portion 10 of the bottomed container 9a, and the low-pressure pump 7
The coating material transferred in a fixed amount is dropped onto the insulating sealing cylinder 9. The paint inflow section 10 includes a paint supply guiding section 15 and a paint dropping section 16, each of which is made of an insulating material such as polyethylene or polypropylene. The paint supply guiding section 15 is formed by an elbow-shaped cylindrical body having a horizontal section 15a and a rising section 15b, an insulating tube 14 is connected to an end of the horizontal section 15a, and a paint dropping section 16 is formed on the rising section 15b. Is formed. The rising portion 15b has a large-diameter portion, and the paint dripping grooves 18, 18 radiating from the central hole 17 on the upper end surface thereof.
.. Are formed. The paint dripping grooves 18, 18,... Are formed as dispersing / diverting grooves inclined downward from the start end 18a to the end 18b.
The paint is dispersed and diverted. Here, the paint dropping portion 16 makes the diameter φ smaller than the diameter of the paint dropping hole 12 of the bottomed container 9, and the dropped paint falls vertically and contacts the paint dropping hole 12 of the bottomed container 9. It is arranged not to be. The size (groove width) and the distance between the grooves of the paint dripping groove 18 are defined by the viscosity and flow rate of the paint. The configuration of the paint inflow section 10 is preferably a configuration that is unlikely to cause clogging and that is easy to maintain. This is because, for example, in the case of a configuration in which a hole is formed in a dish-shaped bottom, even if the hole (groove) is clogged little by little, the pressure loss does not change extremely, so that the paint concentrates in several holes (grooves). This is because the necessity of taking into account the fact that a water droplet does not form at the time of dropping and causes insulation failure is considered. In addition, if the paint used is water-based or the like and once formed into a film, clogging is likely to occur when a paint that does not melt again is used. In addition, the dripping paint downstream 11
Is for supplying the paint dripped from the insulating sealing cylinder 9 to the paint spraying unit 4, and also serves as the paint drop hole 12f of the lowermost bottomed container 9f. The drip paint flow lower part 11 of the insulating sealing cylinder 9 also serves as a drain hole, and is configured to return the paint to the paint tank 5 of the paint supply unit 1 by the drain pipe 19. Power supply unit 3
Is a digital multimeter 21, a programmable controller 22 for controlling the amount and speed of supply of paint, and a high-voltage power supply for applying a high voltage to the paint injectors 26 and 26 of the paint ejecting unit 4 using a 100V AC power supply. 23, an electrostatic voltmeter 24 and a microampere meter 25, which are responsible for driving the pulse motor M of the paint supply unit 1 and applying a high voltage to the paint spraying unit 4.

[0010] The electrostatic coating apparatus of this embodiment operates as follows. First, the water-based paint is put into the paint tank 5, the power is turned on, the stirrer 6 is driven, the paint is sufficiently mixed, the programmable controller 22 is operated, and the pulse motor M and the low-pressure pump 7 are driven. Then, the paint is quantitatively supplied to the paint insulating unit 2. Then, the paint supplied to the paint insulating unit 2 is supplied to a paint supply guiding unit 15 provided at an upper end portion of the insulating sealing cylinder 9 constituting the isolator 8, and the horizontal portion 15a and the rising portion 15 are provided.
It is guided to the paint dropping part 16 through b. Paint dripping part 1
In 6, the paint overflows from the central hole 17. This is because water-based paints having a high viscosity are unlikely to form water droplets. For this reason, in order to surely make the paint in the form of water droplets, it is necessary to reduce the amount of dripping from one place, so that the paint dripping grooves 18, 18,.
・ ・ Dispersed, diverted and dropped. Here, since the paint is guided so as to be quantitatively induced, and is formed so as to be dispersed and divided and fall, the paint falls in a water-drop shape without causing clogging of the paint. The dropped paint is insulated according to the drop interval, but when the paint is partially adhered to the inner wall of the insulating sealing cylinder 9, the applied height to the paint spraying unit 4 is increased. Creepage dielectric breakdown occurs due to the voltage, and the applied paint is also in a state where a high voltage is applied. Then, the dripping paint is attracted toward the high-voltage charged portion by electrostatic induction, and at the moment of contact with the charged portion, the impact of the collision and the action of the high pressure cause the water-drop-shaped material to scatter and adhere. Then, a creepage leak occurs again to the paint that has newly adhered to the portion other than the high-voltage charged portion, and the same repetition is performed, even if the inside of the closed container has a shape that does not easily cause creepage breakage such as unevenness,
Due to the action of the high pressure, the inside becomes conductive for a very short time, and paint insulation becomes impossible. However, it is provided on the outer periphery of each bottomed container 9a, 9b,. Are grounded independently, the paint adheres to the bottomed container made of the insulating material, and the high-voltage charging section progresses. The bottomed container wall gradually becomes charged to a high pressure. The moving speed of the electric charge is low because it is an insulating material, but the electric charge gradually flows out to an electrode provided on the outer periphery as a leak current. For this reason, a voltage drop gradually occurs at the ground electrode portion, and the adsorption and collision phenomena due to electrostatic induction are extremely reduced, and the insulation state above the ground electrode is maintained. At this time, the applied voltage is 60 KV, and the leak current is about 5 to 7 μA. The bottomed container is made of polypropylene and has a thickness t of about 1.3 mm. At this time, the discharge current was 80 μA, and the applied voltage was 60 KV, so that the electrostatic coating was sufficiently performed. The leakage current is induced to the ground side, and the conductive portion and the upper portion of the inner wall of the cylindrical body are kept in an insulated state, and serve to prevent a short circuit with the dripping paint. Each of the bottomed containers 9a, 9b,... Constituting the insulating sealed cylindrical body 9 has paint descending holes 12a, 12b,.
, 2a, 12b,... Have smaller opening diameters as they go to the lower stage, but on the way, they become paint descending holes 12c with an opening diameter smaller than the lower-stage paint descending holes 12d. It acts to prevent the conduction state from spreading. And the paint, which is kept insulated,
From the drip paint flow-down portion 11 formed at the lower end of the insulating sealing cylinder 9, a fixed amount is supplied to the paint spraying section 4 by the high-pressure pump 20 while a high voltage is applied due to the conductivity of the water-based paint. Is done.

Next, in order to confirm the effect of the present embodiment, the object to be coated (cement roof tile) was coated with an aqueous paint under the same conditions by using the apparatus of the present embodiment and the conventional apparatus. Painted. According to the test results, in the case of the present embodiment, the insulation state of the paint can be maintained continuously for 2 hours or more, the application efficiency exceeds 90%, and the fact that the water content in the paint is small reflects that. In contrast to the conventional apparatus, electrostatic coating with the above paint of 150 to 300 μm was performed, but in the conventional apparatus, the dripping paint adhered to the inner wall of the hollow body in about 5 to 15 minutes, and the insulating state of the paint could not be maintained. The result was that the painting had to be interrupted.

It should be noted that the present invention is not limited to the above-described embodiments, but includes those which can be modified and implemented without departing from the gist of the present invention. Incidentally, the following modification may be performed. (1) At a predetermined interval inside one cylindrical body, the insulating cylindrical body is not formed by stacking a plurality of bottomed containers.
A structure with a "circular fin (projection)" that forms a dropping paint drop hole inside. (2) Without making the insulating sealed cylindrical body circular in plan view,
For example, a configuration in which a hollow container having a square or elliptical shape in plan view is used. (3) A configuration in which the electrodes are integrally disposed on the insulating sealed cylinder. (4) A configuration in which the insulation resistance of the wall of the insulating sealed cylinder is partially changed.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a paint insulating device in electrostatic coating according to an embodiment of the present invention.

FIG. 2 is a block diagram.

FIG. 3 is a schematic sectional view of a paint insulating section.

FIG. 4 is a perspective view of a paint inflow portion forming a paint insulation portion.

FIG. 5 is a front view of FIG. 4;

FIG. 6 is a perspective view of a bottomed container forming a paint insulating portion.

FIG. 7 is a schematic cross-sectional view of a paint insulating section according to another embodiment.

FIG. 8 is a perspective view of a bottomed container forming a paint insulating portion.

FIG. 9 is a perspective view of a bottomed container forming a paint insulating portion. DESCRIPTION OF SYMBOLS 1 ... paint supply part, 2 ... paint insulation part, 3 ... power supply part, 4 ... paint spraying part, 5 ... paint tank, 7 ...
..Low-pressure pumps, 8 ... isolators, 9 ... insulated sealed cylinders, 9a, 9b to 9f ... bottomed containers, 10 ...
..Paint inflow section, 11 ... Drip paint downstream, 12, 1
2a, 12b to 12f: paint downhole, 12 '...
Hole ends, 13a, 13b to 13f ... electrodes, 14 ...
Insulating tube, 15: paint supply guiding section, 15a: horizontal section, 15b: rising section, 16: paint dropping section, 17: center hole, 18: paint dropping groove, 18a
... the beginning of the paint dropping groove, 18b ... the end of the paint dropping groove, 19 ... the drain pipe, 20 ... the high pressure pump,
21: Digital multimeter, 22: Programmable controller, 23: High voltage power supply, 24 ...
・ Electrostatic voltmeter, 25 ... microampere meter, 26 ・
..Paint injectors, M pulse motors

Claims (1)

(57) [Claims] 1. A liquid paint supplied from a conductive paint supply source is dropped from a paint dropping portion provided in an upper portion of a hollow body toward a lower portion of a dropping paint flow, and a high voltage for electrostatic coating is applied. A paint insulating device in electrostatic coating that can prevent the paint from adhering to the inner wall surface of the hollow body by a high voltage of an application unit, wherein the paint dropping unit is configured to circularly paint the paint blown upward from a central portion. A plurality of drip grooves diverging in a circumferential direction, wherein the hollow body is made of an insulating material, at a position above the lower part of the dripping paint flow, at least on a lower periphery of the hollow body, and is grounded made of a conductive material. A paint insulating device for electrostatic coating, comprising a potential rise preventing portion provided with an electrode.