JP4815422B2 - Electrostatic powder coating equipment - Google Patents

Description

  The present invention relates to an electrostatic powder coating apparatus that discharges powder coating material from a gun tip nozzle of an electrostatic powder coating gun to a coating material in a coating booth and adheres the powder coating material to the coating material by static electricity. It is about.

  Powder coating is expected as an environmentally friendly coating that does not contain organic solvents, as well as aqueous coating.

The electrostatic powder coating apparatus is an apparatus that discharges a powder coating material from a gun tip nozzle of a powder coating gun to an object to be coated in a coating booth and adheres the powder coating material to the object to be coated by static electricity. As a method for applying static electricity to the powder coating, a corona electrode is installed at the tip of the powder coating gun, and a corona charging type that charges the powder coating by corona discharge, and a non-conductive tube with powder There is a triboelectric charging type in which a paint is passed and charges are applied to the powder paint by friction.
In either case, the powder coating gun tip is inserted into the painting booth to discharge the powder paint toward the object to be coated. It does not adhere, but overspray powder that does not adhere to the substrate is produced. The overspray powder in the painting booth is collected and mixed with new powder for reuse.

  By the way, the above-mentioned overspray powder is collected by a dust collector provided in the painting booth, but drifts in the painting booth and adheres to the wall of the painting booth, or reflects off the object to be coated in the direction opposite to the discharge direction. Some overspray powders come back and adhere to the outer surface of the gun tip nozzle of the powder coating gun and the outer surface of the powder coating gun.

  In particular, in the case of a corona-charged electrostatic powder coating gun, if a pinhole occurs in the nozzle tip of the gun where the electrode is installed, corona discharge leaks from the pinhole and this leaked portion Overspray powder tends to adhere toward the surface, and this adhesion weakens the corona discharge, resulting in poor powder paint adhesion efficiency.

In addition, in the case of a frictionally charged electrostatic powder coating gun, the nozzle extended from the gun body is also formed by a non-conductive tube. The charge opposite to that of the powder coating is accumulated in the nozzle of the non-conductive resin. For this reason, the overspray powder is attracted electrostatically to the outer surface of the nozzle of the non-conductive resin and easily adheres to it, and the outer surface of the nozzle becomes dirty and the efficiency of adhesion to the object to be coated also deteriorates.
In both the case of the corona charging electrostatic powder coating gun and the case of the friction charging electrostatic powder coating gun, if the amount of powder coating adhering to the nozzle outer surface of the gun tip increases, There is also a problem that the body paint is peeled off in a small lump state, and a coating failure called spit where the peeled lump adheres to the object to be coated occurs.

  Therefore, the present invention is intended to provide a powder coating apparatus capable of preventing the overspray powder from adhering to the outer surface of the nozzle tip of the electrostatic powder coating gun.

In order to solve the above-described problems, the present invention shields the insertion opening of the electrostatic powder coating gun provided on the side wall of the coating booth with a shielding panel, and electrostatic powder is inserted into the nozzle insertion hole provided in the shielding panel. The tip of the gun tip nozzle of the paint gun was inserted .

  As a result, even if the powder coating material discharged from the gun tip nozzle of the electrostatic powder coating gun returns to the opposite side of the discharge direction as overspray powder, the overspray powder will not adhere to the tip of the gun tip nozzle. Since it is shielded by the conductive shielding panel, adhesion of the powder coating to the outer surface of the gun tip nozzle and the outer surface of the coating gun is prevented.

  According to the present invention, as described above, it is possible to prevent the overspray powder from adhering to the outer surface of the gun tip nozzle and the outer surface of the coating gun. Therefore, even in the case of a corona charging type electrostatic powder coating gun, the friction charging type In the case of the electrostatic powder coating gun, the adhesion efficiency to the object to be coated is improved. In addition, since the powder paint does not adhere to the outer surface of the gun tip nozzle, it is possible to prevent the occurrence of spits that the powder paint lump is peeled off and adheres to the coating film.

  As an example of the powder coating apparatus according to the present invention, an example using a triboelectric electrostatic powder coating gun will be described.

  As shown in FIG. 1, a frictionally charged electrostatic powder coating gun 1 used in this embodiment has a gun body 2 made of fluorotetrafluoroethylene, and is extended so as to branch from the gun body 2. The nozzle coating 3 is composed of a nozzle tube 3, and the powder coating is frictionally charged by passing the powder coating through the gun body 1 and the nozzle tube 3 by the carrier air, and the powder coating is applied to the gun body 2 and the nozzle tube 3. The opposite charge accumulates.

  As the nozzle tube 3, for example, a tube made of 5 × 8φ tetrafluorofluoroethylene is used, and the tip portion is installed in a line with the tube support 4.

  In the coating booth 5 shown in FIG. 2 and FIG. 3, four sets of the electrostatic charging type electrostatic powder coating gun 1 described above are disposed so as to face two side walls, and the four electrostatic powders. The powder coating material is discharged from the coating gun 1 to the article A suspended from the hanger 7 of the conveyor 6. A dust collection duct 8 is connected to the painting booth 5, and overspray powder is collected from the bottom of the painting booth 5.

  In this embodiment, as shown in FIG. 2, the insertion opening 9 of the electrostatic powder coating gun 1 provided on the side wall of the coating booth 5 is shielded by a shielding panel 10 made of non-conductive resin. Then, as shown in FIG. 4, by inserting the tip of the nozzle tube 3 into the nozzle insertion hole 11 provided in the shielding panel 10, the powder paint discharged into the coating booth 5 returns in the direction opposite to the discharge direction. Even if it comes, powder coating material is prevented from adhering to the outer surface of the nozzle tube 3. The tip of the nozzle tube 3 may be inserted so as to slightly protrude from the nozzle insertion hole 11 into the coating booth 5.

  The said shielding panel 10 is being fixed with respect to the side wall of the coating booth 5 with the bolt made from nonelectroconductive resin. As a material for forming the shielding panel 10, polyethylene or the like can be used in addition to a fluorine-based resin such as tetrafluorofluoroethylene which is a non-conductive resin.

  In order to prevent the nozzle tube 3 from slipping out of the nozzle insertion hole 11 of the shielding panel 10 and to seal the gap between the nozzle tube 3 and the nozzle insertion hole 11, as shown in FIG. The polyethylene tube 13 is preferably fitted.

  Negative charge is accumulated in the nozzle tube 3 due to friction with the powder coating material. In order to prevent sparking due to air discharge of this electric charge and to remove the accumulated electric charge and perform triboelectric charging more efficiently, an aluminum tape is wound around the outer surface of the nozzle tube 3 or a copper coating is provided. It is preferable to ground the conductive layer on the outer surface of the nozzle tube 3 and remove the accumulation of charges in the nozzle tube 3.

  When the painting booth 5 shown in FIGS. 2 and 3 is used, the insertion port 9 is shielded by a non-conductive resin shielding panel 10 (Example 1), and the insertion port 9 is not shielded (Comparative Example 1). Table 1 shows the experimental results of measuring the amount of the powder coating material adhering to the article A.

  In this experiment, the distance from the tip of the nozzle tube 3 to the object A is 200 mm, the speed of the conveyor 6 that conveys the object A is 1.5 m / min, and the electrostatic powder coating gun 1 per unit. The coating amount was 30 g / min, and four units were continuously discharged at 120 g / min. Moreover, the dimension of the to-be-coated article A was 300 mm in width, 400 mm in height, and 430 mm in length, and the coating conditions were set so that the adhesion amount per piece was 33 to 35 g.

Further, Example 2 shows a case where the coating amount per unit of the coating gun 1 is set to 27 g / min in order to set the adhesion amount to a specified value of 33.2 g / min.
The adhesion efficiency is expressed in% of the amount adhered to the object to be coated with respect to the discharge amount.

  In Comparative Example 1 above, since the insertion port 9 is not shielded by the shielding panel 10, the overspray powder adheres to the entire outer surface of the nozzle tube 3 and becomes dirty. Since the mouth 9 is shielded by the shielding panel 10, there is no adhesion of overspray powder to the outer surface of the nozzle tube 3, and the adhesion efficiency is improved as compared with Comparative Example 1.

It is a front view which shows an example of the friction charging type electrostatic powder coating gun used with the electrostatic powder coating apparatus which concerns on this invention. It is a front view of the coating booth of the electrostatic powder coating apparatus which concerns on this invention. FIG. 3 is a plan view of FIG. 2. It is an enlarged view of the nozzle insertion hole part of the shielding panel of the electrostatic powder coating apparatus which concerns on this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Electrostatic powder coating gun 2 Gun body 3 Nozzle tube 4 Tube support 5 Coating booth 6 Conveyor 7 Hanger 8 Dust collection duct 9 Insertion port 10 Shielding panel 11 Nozzle insertion hole 13 Polyethylene tube

Claims (3)

In the electrostatic powder coating equipment that discharges powder paint from the gun tip nozzle of the electrostatic powder coating gun to the object in the painting booth and attaches the powder paint to the object to be coated , The insertion opening of the electrostatic powder coating gun provided on the side wall is shielded by a shielding panel, and the tip of the gun tip nozzle of the electrostatic powder coating gun is inserted into the nozzle insertion hole provided in the shielding panel, thereby An electrostatic powder coating apparatus characterized by preventing powder paint from adhering to the outer surface of a nozzle .
  2. The electrostatic powder coating according to claim 1, wherein the gun tip nozzle of the electrostatic powder coating gun comprises a plurality of nozzle tubes, and the tip of the nozzle tube is inserted into a nozzle insertion hole provided in the shielding panel. apparatus.   The electrostatic powder coating gun is a frictional charging type, wherein the nozzle tube is formed of a non-conductive resin tube, a conductive layer is provided on the outer surface of the nozzle tube, and the conductive layer is grounded. 2. The electrostatic powder coating apparatus according to 2.

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