JPH0985133A - Electrostatic coating gun - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable to adjust the intensity of electric field between a corona discharge electrode and a material to be coated in an electrostatic coating gun having the corona discharge electrode. SOLUTION: An earth electrode 4 is mounted around a corona discharge electrode 1 and the distance between the earth electrode 4 and the corona discharge electrode 1 is made variable by moving the earth electrode 4 by a moving means such as a feed screw mechanism 5.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrostatic coating gun having a corona discharge electrode for charging powder coating material.

[0002]

2. Description of the Related Art In this type of electrostatic coating gun, the surface of a coating film is easily roughened by corona discharge, and the coating film surface is apt to become an uneven surface which is referred to as yuzu skin.

For this reason, an earth electrode is provided around the corona discharge electrode of the electrostatic coating gun, and the intensity of the electric field between the corona discharge electrode and the object to be coated is adjusted to obtain a smooth coating surface. I am trying to be.

[0004]

However, as described above, the strength of the electric field between the corona discharge electrode of the electrostatic coating gun and the object to be coated is determined by the ground electrode so that the surface of the coating film does not form a scratched surface. Adjustment, the electric field tends to concentrate on the edges of the object to be coated, so the coating film thickness at the edges of the object becomes thicker than at other parts, and scratches appear on the edges. Easy to form.

[0005] When the thickness of the coating on the edge of the object to be coated is increased, when the edge of the object to be coated is inserted into a slit or a recess having a predetermined width and assembled, the insertion is hindered. A problem arises.

Accordingly, the present invention provides an electrostatic coating gun capable of adjusting the intensity of an electric field between a corona discharge electrode and an object so that the electric field of the corona discharge does not concentrate on the edge of the object. It is intended to provide.

[0007]

In order to solve the above problems, the present invention provides a ground electrode around a corona discharge electrode of an electrostatic coating gun, and a distance between the ground electrode and the corona discharge electrode. The moving means for changing is provided on the ground electrode.

As described above, if the distance between the ground electrode and the corona discharge electrode is made variable, when the object to be coated is passed by the transfer device in a face-to-face condition with the electrostatic coating gun and coating is performed,
When the edge of the work piece approaches the front of the electrostatic coating gun, the ground electrode is moved closer to the corona discharge electrode to create an electric field between the corona discharge electrode and the edge of the work piece. By weakening, it becomes possible to reduce the concentration of the electric field on the edge of the object to be coated.

[0009]

1 (a) and 1 (b) show a first embodiment of an electrostatic coating gun according to the present invention.

In this electrostatic coating gun, a muzzle 2 provided with a corona discharge electrode 1 is attached to a discharge port of powder paint, and a ground electrode 4 is evenly provided around a cap nut 3 on which the muzzle 2 is attached. It has a structure with six installed.

The above-mentioned six earth electrodes 4 are attached to an electrode holder 6 which is slidably movable with respect to the cap nut 3 by a feed screw mechanism 5, and the electrode holder 6 is slid by the feed screw mechanism 5. The distance between the corona discharge electrode 1 and the ground electrode 4 can be changed.

The corona discharge electrode 1 is connected to a high voltage generator and charges the powder coating material discharged from the muzzle 2 by corona discharge.

Since the ground electrode 4 is grounded via the ammeter 7 and free electrons due to corona discharge are removed from the ground electrode 4, the distance between the ground electrode 4 and the corona discharge electrode 1 is reduced. Thus, the strength of the electric field between the corona discharge electrode 1 and the object to be coated changes.

The earth electrode 4 is made of a conductive material such as tungsten, and is used as an electrode holder 6.
Is formed of a non-conductive resin such as vinyl chloride.

As described above, since the distance between the ground electrode 4 and the corona discharge electrode 1 can be changed by sliding the electrode holder 6 with respect to the cap nut 3 by the feed screw mechanism 5, this distance can be adjusted by coating. By changing the inside as follows, it becomes possible to control the strength of the electric field between the corona discharge electrode 1 and the object to be coated. Therefore, in the case where the electric field is concentrated on the edge of the object to be coated and the coating film on the edge becomes thick, the earth electrode 4 is corona-discharged when applying the edge. When it is brought close to the electrode 1, the electric field is weakened, and the concentration of the electric field on the edge can be reduced. Also, in the case of an uneven coating object, when the convex surface of the coating object that is close to the corona discharge electrode of the electrostatic coating gun is painted, bring the corona discharge electrode and the ground electrode close to weaken the electric field. On the contrary, by controlling the electrostatic field by separating the corona discharge electrode and the ground electrode of the electrostatic coating gun to strengthen the electric field, a coating film with a uniform film thickness without scratches can be formed on the entire surface of the uneven object. can do.

Next, FIG. 2 shows a second embodiment of the electrostatic coating gun according to the present invention.

This electrostatic coating gun does not attach the plurality of earth electrodes 4 to one electrode holder 6 and move them integrally as in the first embodiment, but moves the plurality of earth electrodes 4 individually. For this reason, the electrode holder 6 and the feed screw mechanism 5 are installed on each of the plurality of ground electrodes 4.

When the plurality of ground electrodes 4 are individually moved as in the second embodiment, a strong electric field and a weak electric field are formed at the same time, and the electric field has a directional characteristic. Adjustment is possible.

Next, FIG. 3 shows a third embodiment of the electrostatic coating gun according to the present invention.

In this electrostatic coating gun, the earth electrode 4 is attached to the rotary shaft 8 so as to be opened and closed in a fan shape, and the earth electrode 4 is swung by moving the connecting member 9 of the rotary shaft 8 back and forth by the feed screw mechanism 5. I am trying. As a result, when the ground electrode 4 is opened, the distance between the ground electrode 4 and the corona discharge electrode 1 is increased, and when the ground electrode 4 is closed, the distance between the ground electrode 4 and the corona discharge electrode 1 is decreased. .

Next, FIG. 4 shows a fourth embodiment of the electrostatic coating gun according to the present invention.

In this electrostatic coating gun, a corona discharge electrode 1 and a ground electrode 4 are installed inside a powder coating material discharge passage 10.

The fourth mode is called an internal corona charging method because the corona discharge electrode 1 is inside the discharge passage 10. This form is effective for an electrostatic coating gun in which the discharge passage 10 is formed of a non-conductive resin such as Teflon, that is, an electrostatic coating gun in which friction charging and corona charging are combined.

[0024]

EXAMPLES Using the electrostatic coating gun of the form shown in FIG. 1, a steel plate-like object having a height of 1000 mm and a width of 500 mm was hung at a hanger pitch of 900 mm and a conveyor speed of 1.0.
Table 1 shows the results of coating with a gun distance of 180 mm, a reciprocating stroke of 1000 mm above and below the gun, a reciprocating speed of 30 m / min, and a discharge rate of 100 g / min while being transported at m / min.

The results in Table 1 show that the distance between the corona discharge electrode 1 and the ground electrode 4 was fixed at 80 mm without moving the ground electrode 4 during coating and the coating was performed, and the end of the object to be coated. The distance between the ground electrode 4 and the corona discharge electrode 1 should be 80 mm to 40 mm only when the edge passes.
This is a comparison with the case where the ground electrode 4 is moved so as to approach the corona discharge electrode 1 by the feed screw mechanism 5. When the ground electrode 4 is moved, the center part and the edge part of the object to be coated are compared. It was confirmed that and did not cause much difference in film thickness.

In Table 1, the film thickness shows the average film thickness measured at a pitch of 10 mm at the width of 50 mm at the left and right edge portions and at a pitch of 100 mm at the central width of 400 mm.

[0027]

[Table 1]

[0028]

As described above, the electrostatic coating gun of the present invention adjusts the strength of the electric field between the corona discharge electrode and the object to be coated by moving the ground electrode with respect to the corona discharge electrode. Therefore, there is an effect that a smooth coating film surface having a constant film thickness and no scratched skin can be obtained.

[Brief description of drawings]

FIG. 1A is a schematic side view showing a first embodiment of an electrostatic coating gun of the present invention, and FIG. 1B is a front view of the same.

FIG. 2 is a schematic side view showing a second embodiment of the electrostatic coating gun of the present invention.

FIG. 3 is a schematic side view showing a third embodiment of the electrostatic coating gun of the present invention.

FIG. 4 is a schematic side view showing a fourth mode of the electrostatic coating gun of the present invention.

[Explanation of symbols] 1 Corona discharge electrode 2 Muzzle 3 Cap nut 4 Ground electrode 5 Feed screw mechanism 6 Electrode holder 7 Ammeter 8 Rotating shaft 9 Connecting member 10 Discharge passage

Claims (1)

[Claims] 1. An electrostatic coating gun having a corona discharge electrode for charging powder coating material, wherein a ground electrode is provided around the corona discharge electrode, and a distance between the ground electrode and the corona discharge electrode is changed. An electrostatic coating gun characterized in that a moving means is provided on the ground electrode.