JP5352799B2 - Corona charging device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a corona electrification-type coating device which is almost free from the deposition of powder coating material on a corona electrode 4 and can optimize the position setting of the corona electrode 4. <P>SOLUTION: This corona electrification-type coating device features the covering of the corona electrode 4 exposed at the gun tip 2 of a spray gun for discharging the powder coating material by a flexible non-conducting resin tube 5. Thus it is possible to inhibit the deposition of the powder coating material on the corona electrode 4 and adjust the position of the corona electrode 4 in compliance with coating speed, the distance to an article to be coated, habit of the operator, etc. by flexing the non-conducting resin tube 5. Consequently, an optimal electric field for coating conditions can be formed. <P>COPYRIGHT: (C)2010,JPO&amp;INPIT

Description

  The present invention relates to a corona charging type coating apparatus that applies a high voltage to a corona electrode, attaches ions generated by corona discharge to the powder coating material, and electrically coats the coating material with the powder coating material. .

  Powder coating is a coating method in which a charged powder coating is sprayed on the object to be coated, and the powder coating is electrically attached to the object to be coated. It is an environmentally friendly painting method that can be recovered and reused.

  By the way, in powder coating, in order to make the smoothness of a coating film better, atomization of the powder coating is progressing.

  In recent years, the demand for metallic coatings using metallic powder coatings containing aluminum pigments has also increased.

  7 and 8 show a conventional general electrostatic powder coating gun 1 in which a flat type nozzle 3 for forming a fan-shaped discharge pattern is mounted on a cylindrical gun tip 2 from which powder paint is ejected. In addition, an electrode 4 connected to a high voltage generator is installed on the cylindrical gun tip 2 in a state where it protrudes from the central part inside the flat nozzle 3.

  When the electrostatic powder coating gun 1 having such a structure is used and atomized powder coating or metallic powder coating containing an aluminum pigment is sprayed, in particular, at the tip of the electrode 4 that performs corona discharge, As shown by the symbol D in FIG. 7, the powder coating is likely to adhere as if it is hardened.

  When the amount of the powder coating material adhering to the tip of the electrode 4 is increased, the powder coating material adhering to the electrode 4 is peeled off during coating, and the lump of the powder coating material peeled off adheres to the object to be coated. The problem of causing poor coating occurs.

  In particular, the aluminum pigment contained in the metallic powder coating tends to adhere to the electrode 4, and it is not uncommon for the aluminum pigment to cover the gun tip of the spray gun that discharges the powder coating so that the aluminum pigment covers it. Since the aluminum pigment is conductive, the aluminum pigment grown at the tip of the electrode 4 has a problem that corona leak increases and the coating efficiency is lowered. Further, when the corona leak increases, there is a problem in the safety of powder coating.

  Next, in the corona charging type coating apparatus, the position setting of the corona electrode is extremely important in order to give an optimum charge to the powder coating material and improve the coating efficiency.

  For this reason, the position of the corona electrode is optimally set depending on the shape of the gun tip, the type of powder coating, the shape of the object to be coated, the distance to the object to be coated, or, in the case of hand-blown guns, the operator's heel It is necessary to make it.

  However, in reality, there has been nothing that can adjust the position selection of the corona electrode.

  In view of the above, the present invention is intended to provide a corona charging type coating apparatus in which the powder coating is less likely to adhere to the corona electrode and the position setting of the corona electrode can be optimized.

  In order to solve the above-mentioned problems, the present invention is a non-conductive material capable of bending an electrode exposed at the tip of a spray gun that discharges powder paint or an electrode exposed in a booth sprayed with powder paint. By covering with a conductive resin tube, it prevents powder paint from adhering to the electrode, and by bending the non-conductive resin tube, the electrode can be used according to the coating speed, distance to the object to be coated, worker's wrinkles, etc. This makes it possible to form an electric field optimal for the coating conditions.

  Furthermore, the introduction of air or inert gas into the non-conductive resin tube that covers the electrode ensures that the powder coating does not adhere to the tip of the electrode, and the contact between the powder coating and the non-conductive resin tube Even if the non-conductive resin tube is worn and a hole is formed, the powder coating material is prevented from entering the non-conductive resin tube from the hole.

  According to the present invention, as described above, the powder coating can be effectively prevented from adhering to the electrode that undergoes corona discharge, so that it is possible to form a good coating film without blisters, and by adjusting the position of the electrode, An electric field that is optimal for the coating conditions can be formed, and optimal coating with high coating efficiency can be achieved.

  The electrostatic powder coating gun 1 shown in FIG. 1 is equipped with a flat nozzle 3 that forms a fan-shaped discharge pattern on a cylindrical gun tip 2 from which powder paint is ejected.

  An electrode 4 connected to a high voltage generator passes through the gun tip 2 and is drawn inside the flat nozzle 3 at the cylindrical gun tip 2.

  The electrode 4 projecting inside the flat nozzle 3 is drawn out to the center of the flat discharge port 9 of the nozzle 3.

  The electrode 4 is made of a metal such as tungsten, iron, copper, or stainless steel, and a portion that protrudes into the nozzle 3 is covered with a bendable non-conductive resin tube 5 and passes through the gun tip 2. Does not contact the electrode 4. Thereby, it is possible to prevent the powder paint from adhering to the metal electrode 4 or the metallic pigment contained in the powder paint from being stuck.

  The material of the non-conductive resin tube 5 may be nylon, polyethylene, or polyacetal based on the powder coating used in addition to the tetrafluoroethylene resin.

  As shown in FIGS. 2 and 4, the rear end of the non-conductive resin tube 5 placed on the electrode 4 is inserted into a fixing hole formed on the end face of the cylindrical gun tip 2.

  Next, in the embodiment of FIGS. 2 to 4, the electrode 4 is embedded and installed in the cylindrical portion of the gun tip 2, but as in the embodiment of FIG. The compressor air supplied through the through-hole 6 is provided with a through-hole 6 through which compressor air or inert gas passes, the electrode 4 is passed through the through-hole 6, and a non-conductive resin tube 5 is inserted into the tip of the through-hole 6. Alternatively, the inert gas may pass through the nonconductive resin tube 5 and flow out from the tip of the nonconductive resin tube 5.

  In this way, by causing air or inert gas to flow out from the tip of the non-conductive resin tube 5, adhesion of the powder paint to the tip of the electrode 4 is reliably prevented. Even if the non-conductive resin tube 5 in the nozzle 3 constantly collides with the powder coating and the collision causes the non-conductive resin tube 5 to wear and have a hole, as described above, the non-conductive resin tube 5 By allowing air or inert gas to pass through the resin tube 5, the inside of the non-conductive resin tube 5 is always kept in a positive pressure state, so that the powder paint is non-conductive from the hole of the non-conductive resin tube 5. Intrusion into the resin tube 5 can be prevented.

  Next, FIG. 6 shows an embodiment of a corona charging type coating apparatus in which powder paint is sprayed in the booth 7 and the powder paint is charged by the electrode 4 applied in the booth 7 to which a high voltage is applied. The booth 7 is formed of a nonconductive resin panel.

  In the embodiment of FIG. 6, the electrode 4 is branched so that an electric field due to corona discharge is generated on the entire surface of the object A to be coated, and the branched electrodes 4 are positioned on the side surface and the upper and lower surfaces of the object A to be coated. I am doing so. The electrodes 4 positioned on the upper and lower surfaces of the article A are drawn out to the vicinity of the center of the booth 7. The outer surface of the drawn electrode 4 is covered with a non-conductive resin tube 5, and the electrode 4 The powder coating is prevented from adhering to the outer surface of the.

  Also in the embodiment of FIG. 6, the non-conductive resin tube 5 can be bent, and the installation position of the electrode 4 can be adjusted by bending according to the shape of the article A to be coated.

  Also in the embodiment of FIG. 6, a passage 8 through which the electrode 4 is inserted is provided on the wall surface of the booth 7 in which the electrode 4 is embedded, and compressor air or inert gas is supplied into the passage 8. Thus, compressor air or inert gas may be caused to flow into the non-conductive resin tube 5, and air or inert gas may be allowed to flow out from the tip of the non-conductive resin tube 5.

  In the embodiment of FIG. 6, the symbol B indicates the sprayed powder paint, and C indicates the flowing air.

Next, the electrostatic powder coating gun 1 of the present invention shown in FIG. 2 in which the electrode 4 is covered with a non-conductive resin tube 5 and the conventional electrode shown in FIG. 7 in which the electrode 4 is not covered with the non-conductive resin tube 5. A coating experiment was conducted with the electrostatic powder coating gun 1, and it was investigated how many spots occurred on the coating surface of the object to be coated as the coating time passed. The results are shown in Table 1. Table 2 shows the temporal change in the coating efficiency. As the non-conductive resin tube 5, a tube made of Teflon was used.
In Table 1, the number of irregularities is the total number in each time.

  As shown in Table 1, in the case of the electrostatic powder coating gun 1 of the present invention shown in FIG. 2 in which the electrode 4 is covered with the non-conductive resin tube 5, the electrode 4 is not covered with the non-conductive resin tube 5. FIG. As compared with the conventional electrostatic powder coating gun 1 shown in FIG. Further, as shown in Table 2, in the case of the electrostatic powder coating gun 1 of the present invention shown in FIG. 2 in which the electrode 4 is covered with the nonconductive resin tube 5, the electrode 4 is replaced with the nonconductive resin tube 5. The temporal change of the coating efficiency was less than that of the conventional electrostatic powder coating gun 1 shown in FIG. 7 which was not covered, and the high coating efficiency could be maintained for a long time.

  In the experiments in Tables 1 and 2, two coating guns with a discharge rate of 70 g / min were used, and a metal plate-shaped object having a height of 1000 mm and a width of 500 mm was used while reciprocating with a reciprocator. On the other hand, the powder coating was sprayed. The conveyor speed was 1.0 m / min, and the hanger interval was 600 mm.

  Further, when the electrostatic powder coating gun 1 of the present invention shown in FIG. 5 in which compressor air is caused to flow into the non-conductive resin tube 5 is used and air is caused to flow, the compressor is introduced into the non-conductive resin tube 5. With respect to the case shown in FIG. 4 in which no air is allowed to flow in, a coating experiment of a powder paint in which an aluminum pigment is dry blended was conducted to investigate how the coating efficiency changes with the lapse of the coating time. The result is as shown in Table 3. It was confirmed that when the air was introduced, it was possible to prevent the coating efficiency from decreasing for a longer time than when the air was not introduced. Further, in the case of the conventional example in which the electrode 4 is not covered with the non-conductive resin tube 5, the metallic pigment adhered to the extent that the discharge port of the nozzle 3 was closed in about 30 minutes. Other coating conditions are the same as the experiments in Tables 1 and 2.

  In Table 3, “closed” means that the discharge port of the nozzle at the tip of the gun has been closed by the aluminum pigment adhering to the electrode, and “abnormal” means that the aluminum pigment has adhered to the tip of the electrode. Indicates an overcurrent abnormal condition.

1 is a perspective view of an electrostatic powder coating gun 1 according to the present invention. It is sectional drawing of the gun tip part of FIG. It is a front view of the gun tip part of FIG. It is sectional drawing of the electrode part of the gun tip of FIG. It is sectional drawing of the electrode part of the gun tip of other embodiment of the electrostatic powder coating gun 1 which concerns on this invention. It is a schematic block diagram of the other form of the electrostatic powder coating apparatus which concerns on this invention. It is sectional drawing of the gun tip part of the electrostatic powder coating gun of a prior art example. FIG. 8 is a front view of FIG. 7.

Explanation of symbols

1 Electrostatic powder coating gun 2 Gun tip 3 Nozzle 4 Electrode 5 Non-conductive resin tube 6 Through hole 7 Booth 8 Passage

Claims (3)

  Non-conductive resin that can bend the electrode exposed in the booth in a corona charging type coating device that sprays the powder paint in the booth and charges the powder paint with the high voltage applied electrode installed in the booth A corona charging type coating apparatus characterized in that the electrode position in the booth can be adjusted by covering with a tube and bending a non-conductive resin tube. Above the gap between the non-conductive resin tube and the electrode, a corona charging type coating apparatus according to claim 1 Symbol placement flowing the air. Above the gap between the non-conductive resin tube and the electrode, a corona charging type coating apparatus according to claim 1 Symbol placement flowing the inert gas.

Images