JPH0768198A - Triboelectrification gun for electrostatic powder coating - Google Patents

Abstract

PURPOSE:To provide a triboelectrification gun for powder coating without lowering the electrification efficiency and capable of being miniaturized by reducing the area of the electrifying part. CONSTITUTION:The powder electrifying part is formed with a conductive material in the triboelectrification gun for electrostatic coating, and the electrifying part is grounded 8. The fact that the powder is electrified by the conductive member 3 has been found out by experiment, the charge opposite to that of the generated powder is not accumulated on the member 3 since the member 3 is conductive and grounded, and hence the electrification efficiency is not lowered.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a triboelectric charging gun used for electrostatic powder coating.

[0002]

2. Description of the Related Art Conventionally, in the electrostatic spray system for powder by corona charging, it is very difficult to completely coat powder on the deep groove corners and complicated shapes of the object to be coated. Has applied correction coating once or several times with a hand gun to difficult parts of these coatings. Therefore, there is no influence due to the Faraday cage effect, and excellent throwing power is obtained. Therefore, reverse ionization does not occur, and an electrostatic spray system of powder by a friction charging gun that can be used for cosmetic painting is implemented. (See, for example, Japanese Patent Publication No. Sho 62-24135).

[0003]

In the conventional triboelectric charging gun used in the electrostatic spray system for powder by triboelectrification as described above, the charging portion is made of non-conductive fluorine resin, and the outer periphery thereof is formed. Is provided with a conductive layer which is connected to the ground in order to release the accumulated charge, and the powder carried is brought into contact with the charging portion to be charged.

However, in such a conventional triboelectric charging gun, a charge having a polarity opposite to the charge of the powder is generated and accumulated in the charging portion, and the charging efficiency of the powder is reduced.
In order to increase the area of the charging portion, it was necessary to lengthen the powder passage for charging, and it was not possible to reduce the size. Further, the charging efficiency is improved as the powder is strongly contacted with the charging section, but there is a defect that the life of the charging section is shortened.

An object of the present invention is to provide a friction charging gun for powder coating, which eliminates the above-mentioned conventional defects, does not reduce charging efficiency, and can reduce the area of the charging portion to make it compact. .

[0006]

In order to achieve the above object, the present invention is a frictional charging gun for electrostatic powder coating, wherein the powder charging portion is formed of a conductive member, and the charging portion is grounded. It was done. In addition, it is advantageous to form the charging portion by a charging member made of a conductive fluorine resin or a conductive nylon resin. Further, the charging portion may be formed by a composite plating film in which fine particles of a fluorine resin are co-deposited on a powder friction surface of a metal material or an insulating material, or a thermal spray coating.

Further, the friction charging gun for electrostatic powder coating of the present invention has an inlet portion having a compressed fluid supply portion for giving a swirling flow to the powder and a plurality of powder passages parallel or twisted in the axial direction. It is preferable that it is composed of a central portion having the above and an outlet portion having a gun head or a connecting portion for spraying the charged powder.

[0008]

In the conventional technology, the charging efficiency is lowered because the charge having the opposite polarity to the charge of the powder is generated in the charging portion and the charge portion is made of the non-conductive material. It is known that the cause is accumulation in the department. As a result of experiments, the present invention was made by discovering that the charging part can be made electrically conductive to charge the powder. That is, since the charging section is electrically conductive and is grounded, the charges of the opposite polarity generated in the charging section do not flow to the ground and accumulate, so that the charging efficiency of the powder is reduced. There is no such thing.

When the charging portion is formed of a charging member made of conductive fluorine resin or conductive nylon resin, conductive material such as carbon, graphite, carbon fiber, copper alloy is mixed in the resin. Therefore, it is superior in abrasion resistance as compared with usual fluorine resin and nylon resin, and is particularly suitable as a charging member. Also,
When the electrified part is formed by a composite plating film in which fine particles of fluorine resin are co-deposited on the powder friction surface of a metal material or an insulating material, or a thermal spray coating, the formed powder friction surface is hard and wear resistant. It is possible to obtain a triboelectrification gun for electrostatic powder coating, which is further excellent in properties and has a long life.

[0010]

Embodiments of the present invention will be described below with reference to the powder coating triboelectric charging gun shown in the drawings. In the drawings, the same or corresponding parts are designated by the same reference numerals.

The friction charging gun 1 shown in FIGS. 1, 2 and 3 has a cylindrical outer shell 2, a charging member 3 housed in the outer shell 2, and an annular ring around the charging member 3. A plurality of powder passages 4 formed and arranged in the above, a head connecting portion 5 mounted on the powder outlet side, a compressed fluid supply portion 6 configured on the inlet side, and a hose for powder supply. It comprises a connecting portion 7 for connecting and a grounding portion 8 for grounding the charging member 3.

The tubular outer shell 2 is made of an insulating material or metal, and has ends 2a and 2b at its outlet and inlet, and a head connecting portion 5 is attached to the outlet end 2a, and the inlet end 2 is formed.
The connection part 7 is attached to b. The outer shell 2 can be molded integrally, but it is also possible to manufacture the outer shells 2 in half and connect them in the center to be integrated. The charging member 3 is fluorine outlet cone 3a, entrance cone 3b and the central cylindrical portion 3c, a conical guide portion 3d, consists conical distributor 3e and the nozzle tube portion 10, respectively conductive (10 ⁰ ~10 ¹³ Ωcm) It is made of resin (preferably polytetrafluoroethylene containing 10 to 30% carbon) and is integrated. A plurality of, for example, eight through holes, that is, eight through holes, which are formed and arranged in an annular shape around the central cylindrical portion 3 c, are formed in parallel with the central cylindrical portion 3 c, that is, the powder passages 4. The conical distributor 3e on the inlet side corresponds to the inlet conical part 3b and has a role of evenly distributing the powder to the plurality of powder passages 4 and a role of charging the powder. Further, the cone guide portion 3d on the outlet side corresponds to the outlet cone portion 3a, and has a role of sending the charged powder to the head connecting portion 5 or the powder gun head so as not to cause turbulence or vortex flow. The outlet conical portion 3a can be directly used as the gun head, and the head connecting portion can be omitted. Further, as shown in FIG. 10, it is preferable that the powder passage 4 be formed so as to be twisted by 1 to 180 degrees so as to draw a spiral shape. And the friction opportunity of the charging member can be increased. In this case, if the twisting direction of the powder passage 4 is twisted in the direction opposite to the swirling direction of the compressed fluid, the chance of friction between the powder and the charging member can be further increased. It should be noted that FIG. 10 shows only three of the eight powder passages 4 in order to facilitate understanding of the twist of the powder passages 4.

The powder charging portion is formed on the central cylindrical portion 3c,
The disposed powder passage 4, the inlet cone portion 3b, and the cone distribution portion 3e have a function as a main charging portion, and the outlet cone portion 3a, the cone guide portion 3d, the nozzle cylinder portion 10 and the like also serve as auxiliary charging portions. Have a functional function. The powder charged by the charging section is sent to the head connecting section 5 or the powder gun head H and sprayed on the object to be coated. Compressed fluid supply unit 6
Is a part that gives a swirl flow to the powder in order to frictionally charge the powder at the charging portion. That is, a compressed fluid supply pipe 9 connected to an unillustrated compressed fluid source, a nozzle cylinder portion 10, and a compressed fluid chamber 1 provided between the nozzle cylinder portion 10 and the outer shell 2.
1 and a nozzle hole 12 formed in a tangential direction with respect to the inner side surface of the nozzle tubular portion 10. This nozzle hole 1
In order to efficiently charge the powder, 2 is to supply the compressed fluid as a swirling flow to the nozzle cylinder portion 10. Here, the powder is accelerated by the swirling compressed fluid and frictionally charged by the charging member 3 to be frictionally charged. Pass through the gun.

The earth portion 8 is an annular conductor 8 provided between the outer shell 2 and the end of the entrance cone 3b of the electrically conductive charging member 3.
It has a ground contact connected to a and is fixed to the outer shell 2 with a screw. Through the earth portion 8, of the charges generated in the charging portion, the reverse polarity charges accumulated in the charging member 3 are leaked. Therefore, the charging efficiency of the powder in the charging section does not decrease, and the length of the powder passage 4 can be significantly shortened as compared with the conventional friction charging gun, and as a result, the friction charging gun 1 can be downsized. can do.

FIG. 4 shows the friction charging gun 1 of FIG. 1, that is, the charging member 3 made of conductive fluorine resin (polytetrafluoroethylene containing 20% carbon) and the powder passage 4.
The charging efficiency of the triboelectric charging gun is compared between the case of forming the same and the case of forming the same powder passage 4 in the charging member 3 made of the conventional non-conductive fluorine resin (polytetrafluoroethylene containing no carbon). Therefore, when a polyester-based paint was used as the powder and the experiment was carried out at a compressed air pressure of 2 kgf / cm ² , the amount of charge of the sprayed powder paint (μC
/ G) and the discharge amount (g / min) of the powder coating material. The ground was connected to the charging member 3 in the case of the friction charging gun of the present invention, and was connected to the outer conductive layer of the charging member in the case of the conventional friction charging gun. According to this graph, the larger the discharge amount of the powder coating material is, the more the charge amount of the discharged powder coating material is predominant in the friction charging gun in which the charging member 3 is conductive.

FIG. 5 is a graph showing the charge amount (μC / g) of the powder coating material over time in the same experiment as in FIG. As is apparent from this graph, in the case of the friction charging gun in which the powder passage 4 is formed in the conventional charging member 3 made of non-conductive fluorine resin, the charge amount decreases with the passage of time. In the case of the friction charging gun in which the powder passage 4 is formed in the charging member 3 made of conductive fluorine resin, the rate of decrease is extremely small. From these experimental results, when the charging part is formed of a conductive material, the charge having the opposite polarity to the charge of the powder does not accumulate in the charging part. It is clear that it can be charged.

That is, as shown in FIGS. 4 and 5, the triboelectrification gun in which the electrification part is formed by the electroconductive electrification member 3 gives a larger amount of stable electric charge to the powder than the conventional triboelectrification gun. be able to.

Even if a charging member made of a conductive nylon resin is used in place of the charging member made of a conductive fluorine resin in order to form the conductive powder passage 4, the same action and effect can be obtained. You can In addition, a conductive material having abrasion resistance can be used as the charging member.

In order to make the charging portion conductive, as shown in FIG. 6, the charging member 3 is made of a metal material (aluminum, iron or brass), and the surface of the powder contacting is made of fine particles of fluorine resin. It is also possible to disperse and co-deposit the composite plating film 13 on the surface of the powder passage 4 or the like by electroless plating with a plating solution in which a fluorine resin is dispersed in a nickel plating solution to form a plating film. Plating film 1
Even if 3 is grounded by the ground portion 8, the same action and effect can be obtained. In addition, it is preferable to select a plating film 13 having high hardness to increase wear resistance.

In order to make the charging portion conductive, as shown in FIG. 7, the charging member 3 is made of an insulating material, and a fluorine resin is uniformly dispersed and co-deposited on the surface in contact with the powder. 13 may be used. In this case, the same action and effect can be obtained by grounding the grounding member 8 via the annular conductor 8a at the end of the charging member 3. Further, the surface of the charging member 3 in contact with the powder is formed by a metal spray coating,
Similarly, the same action and effect can be obtained by connecting the grounding portion to the surface of the charging member 3 via the annular conductor 8a at the end of the charging member 3.

As the fluorine resin which can be used as the charging member 3, it is obvious that hexafluoroethylene resin can be used instead of tetrafluoroethylene resin.

Further, as shown in FIG. 8, when the triboelectric charging gun is constructed in multiple stages, the charging effect is improved. In this case, of the charging member 3, only the place where the swirling flow of the compressed fluid becomes weak, that is, only the outlet cone portion 3a, the cone guide portion 3d and the gun head H are made of non-conductive material, and the other charging members are made of conductive material. In that case, the charging efficiency is improved. This is shown in FIG. Therefore, it is desirable that only the outlet cone portion 3a, the cone guide portion 3d, and the gun head H are made of a non-conductive material. The friction charging gun according to the present invention can be used as a precharger, and a charging gun (corona discharge type) using a high voltage can be connected in the subsequent stage to improve the charging effect.

The graph of FIG. 9 shows that when the contact surfaces of the powder are all conductive (a), the outlet cone 3a, the gun head H and the cone guides 3d and 3d 'of the charging member 3 are shown.
It is a comparison of the case (2) in which the non-conductive material is used. As is clear from FIG. 9, when the entire charging member 3 is made electrically conductive, the charge of the charged powder is discharged at the place where the swirling flow of the compressed fluid becomes weak, and the charging efficiency is reduced. Three
a or gun head H and outlet cone guides 3d, 3
When only d'is made of a non-conductive material, the discharge phenomenon disappears and the charging efficiency improves. Note that this phenomenon is
The same applies to the triboelectric charging gun of the embodiment shown in FIG.

[0024]

According to the present invention, since the charging portion of the electrostatic charging gun for electrostatic powder coating is made electrically conductive and this charging portion is grounded, charges of opposite polarity do not accumulate on the charging portion. The charging efficiency of the powder does not decrease. Therefore, since the area of the charging portion can be reduced, the friction charging gun for powder coating can be downsized.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of a friction charging gun for electrostatic powder coating showing an embodiment of the present invention.

FIG. 2 is a sectional view taken along the line AA of FIG.

FIG. 3 is a sectional view taken along line BB in FIG.

FIG. 4 is a graph showing a comparison of charge amounts when a charging member is made conductive and when it is made non-conductive.

FIG. 5 is a graph showing changes in the charge amount when the charging member is made conductive and when it is made non-conductive, as in FIG. 4.

FIG. 6 is a cross-sectional view of an essential part showing another embodiment of the present invention, in which the surface of the charging member made of a metal material, which comes into contact with the powder, is subjected to composite plating in which fine particles of a fluororesin are uniformly dispersed and co-deposited. is there.

FIG. 7 is a cross-sectional view of an essential part showing still another embodiment of the present invention, in which the surface of the charging member made of an insulating material, which comes into contact with the powder, is subjected to composite plating in which fine particles of a fluororesin are uniformly dispersed and co-deposited. Is.

FIG. 8 is a cross-sectional view showing an example in which friction charging guns are connected in multiple stages.

9 is a graph showing the amount of charge in each part of the frictional charging gun of FIG. 8 from the powder inlet to the powder outlet.

FIG. 10 is a perspective view of the charging member when the powder passage is twisted in the axial direction.

[Explanation of symbols]

 1 Electrostatic Powder Coating Friction Charge Gun 2 Outer Shell 2a Outlet Outer Shell End 2b Inlet Outer Shell End 3 Charging Member 3a Outlet Cone 3b, 3b 'Inlet Cone 3c, 3c' Central Column 3d, 3d ' Cone guide part 3e, 3e 'Cone distribution part 4, 4' Powder passage 5 Head connecting part 6, 6'Compressed fluid supply part 7 Connection part 8 Earth part 8a Annular conductor 9 Compressed fluid supply pipe 10 Nozzle cylinder part 11 Compressed fluid Chamber 12 Nozzle hole 13 Plating coating F Powder flow direction H Gun head

Claims (5)

[Claims] 1. A friction charging gun for electrostatic powder coating, characterized in that a charged portion of the powder is formed of a conductive member and the charged portion is grounded. 2. The friction charging gun for electrostatic powder coating according to claim 1, wherein the charging portion is formed of a charging member made of a conductive fluorine resin. 3. The friction charging gun for electrostatic powder coating according to claim 1, wherein the charging section is formed of a charging member made of conductive nylon. 4. The charging part is formed by a composite plating film in which fine particles of a fluorine resin are uniformly dispersed and co-deposited on a powder friction surface of a metal material or an insulating material, or a thermal spray coating. Item 3. A friction charging gun for electrostatic powder coating according to item 1. 5. An inlet part having a compressed fluid supply part for giving a swirling flow to the powder, a central part having a plurality of powder passages parallel or twisted in the axial direction, and spraying the charged powder. The triboelectric charging gun for electrostatic powder coating according to any one of claims 1 to 4, comprising a gun head or an outlet having a connecting portion.