JPH1099737A - Electrostatic coating device for powder coating and disk fitted to the same - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a device appropriately used for coating an inner surface of a cylindrical body having a closed bottom and a side wall in which recessed and projecting parts are formed, such as drum can. SOLUTION: This device 1 is provided with a rotary disk 4 having a lower-side disk 6 as its component and openings 9 and vanes 7 are formed in this lower-side disk 6. Also, a powdery coating material is supplied to the central part of a coating material discharge passage 17 of the rotary disk 4, namely, the central part of the rotary disk 4, through a coating material supply passage 18 formed by an inner/outer double cylinder consisting of an inner cylinder 2 and an outer cylinder 3. Also, the supply passage 20 is fitted with two corona pins 20 and the powdery coating material is charged by the corona pins 20 in the preceding step to the transfer of the coating material to the rotary disk 4. In the process of outwardly discharging the charged powdery coating material from the device 1 through the rotary disk 4 in the radial direction, a part of the powdery coating material falls downward through the openings 9. Further, a carrier air accompanying the powdery coating material that passes through the coating material discharge passage 17 of the rotary disk 4, is allowed to impinge on the vanes 7 to apply rotational force to the rotary disk 4 and to rotate the rotary disk 4 by this force.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention generally relates to electrostatic powder coating, and more particularly, to an electrostatic coating machine suitable for coating the inner surface of a bottomed cylindrical body such as a drum and an electrostatic coating machine. Regarding the disc to be mounted.

[0002]

2. Description of the Related Art Electrostatic coating machines for powder coatings are roughly classified into three types, similar to those for liquid coatings. The first is a bell type, the second is a disk type, and the third is a gun type. The principle of these electrostatic coating machines is that the charged paint powder particles are electrically adsorbed on the object to be coated. They are common in that they let them. Practical application technology in electrostatic coating of powder coatings has historically evolved from an electrostatic coating machine for liquids, and the technology of this electrostatic coating machine for liquids is currently being used. For this reason, for example, in a gun-type coating machine, typically, a needle-shaped electrode is provided at the center of the paint outlet,
Disc-type and bell-type coating machines have electrodes on the periphery of the disk or bell, and form an electrostatic field between these electrodes and the object to be coated to perform powder coating. (For example, JP-B-56-29588, JP-B-56-29588)
-35903).

[0003]

Regardless of whether the paint is a powder or a liquid, a common problem of electrostatic coating is that when a coating object having an uneven surface or an edge is coated, the coating surface becomes unclear. There is a problem that the thickness of the protruding portion or the edge portion becomes relatively thicker than the other portions. This problem is caused by the fact that the lines of electric force formed between the electrode and the object to be coated tend to concentrate on the protruding portion or the edge portion of the object to be coated.

[0004] By the way, when coating the inner surface of a drum can, conventionally, a bell type or disk type coating machine is moved up and down along the axis of the drum can using a liquid paint. In addition to the problem that it is difficult for the paint to enter into the bead portion provided on the side wall of the drum, the supply of the paint to the bottom surface is insufficient compared to the side surface of the drum and the desired film thickness cannot be obtained. Had a problem.

Accordingly, an object of the present invention is to provide an electrostatic coating machine for powder coating which is suitable for coating the inner surface of a bottomed cylindrical body having irregularities on a side wall such as a drum can. A further object of the present invention is to provide an electrostatic coating machine for powder coating that can further coat the bottom surface of a bottomed cylindrical body to a desired film thickness in addition to the above objects. Another object of the present invention is to provide an electrostatic coating machine for powder coating that can keep the influence of the lines of electric force on the coating film within an allowable range even when the voltage applied to the electrodes is increased. . Another object of the present invention is to provide a disk mounted on a powder coating electrostatic coating machine suitable for coating the inner surface of a bottomed cylindrical body having irregularities on a side wall such as a drum can.

[0006]

In view of the technical problem, the present inventors have noticed the following points, and as a result, have devised the present invention. That is, the existence of the lines of electric force formed between the electrostatic coating machine and the object to be coated can be said to be indispensable for the liquid paint. In other words, since liquid paints are generally conductive, even if the paint particles are charged, the paint particles themselves do not have the ability to maintain a charged state, and therefore, an electrostatic field is applied between the coating machine and the object to be coated. Only by the presence of, can the charged state be maintained until the paint reaches the object to be coated.

On the other hand, since powder coatings are generally insulative, once charged, the coating particles have the property of maintaining this charged state for a long time. Focusing on this property of powder paint, if the electrostatic coating machine for powder paint has the function of charging the powder paint and the function of sending the charged paint toward the workpiece Frequently, it is possible to perform electrostatic coating even if there is no electrostatic field between the coating machine and the object to be coated. The electric lines of force have the function of transporting the paint particles to the workpiece, but this function can be supported by transporting the paint to the workpiece using transport air. Therefore, there is little need to consider the electrostatic coating of the powder paint by sticking to the lines of electric force.

Based on such a viewpoint, the present invention provides:
An electrostatic coating machine comprising a rotating disk rotating in a horizontal plane and discharging powder paint outward from an outer peripheral edge of the disk, wherein a corona electrode is provided in a paint supply passage for supplying the powder paint to the rotating disk. The disk is provided with a plurality of openings formed to allow the paint to pass downward.

According to the coating machine according to the present invention, the corona electrode is not directly exposed to the object to be coated, and a part of the coating machine is interposed on a straight line connecting the corona electrode and the object to be coated. Therefore, the line of electric force formed between the corona electrode and the object to be coated can be weakened by a part of the intervening coating machine, or the generation of the line of electric force can be suppressed. In other words, even if a large potential is applied to the corona electrode due to the inclusion between the corona electrode and the object to be coated, that is, the presence of a part of the coating machine, this immediately causes electric field lines between the object and the object to be coated. Is not to be strengthened. Also,
Since a part of the charged powder that has passed through the corona electrode drops through the opening of the disk, a sufficient paint can be supplied to the bottom surface of the bottomed cylinder that is the object to be coated.

Therefore, according to the present invention, there is a problem associated with generation of lines of electric force between an electrode and an object, which is a bottomed cylindrical body having irregularities on a side wall, that is, a convex portion of a coating surface of the object to be coated. , The formation of a relatively thick coating film can be suppressed. In other words, according to the present invention, even if the potential of the corona electrode is set to be relatively high, the above-mentioned problem does not become remarkable. Further, the bottom surface of the bottomed cylindrical body can be coated with a sufficient film thickness.

Another object of the present invention is to provide a bell type electrostatic device in which powder paint is supplied to the center of a bell through a paint supply passage extending along the axis of the main body and a corona electrode is provided in the paint supply passage. A disk for attaching to a bell of a powder coating machine, wherein the disk has an opening provided with a plurality of opening and closing doors, and the opening and closing door is hinged to a main body of the disk to rotate the bell. This is achieved by providing a disk that is in a closed position.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In a coating machine according to the present invention,
A wing may be provided in the paint discharge passage of the rotating disk, and the wing may receive the paint conveying air to rotate the disk. According to this, it is not necessary to provide a driving source, which is a heavy object for rotationally driving the disk, as in the related art, so that the weight of the rotary disk type coating machine can be significantly reduced. This has a great practical advantage that the load on the reciprocator can be reduced when the rotating disk type coating machine is mounted on the reciprocator. When the rotating disk is rotated by the paint conveying air in this manner, providing a cylindrical skirt, for example, on the lower surface of the rotating disk allows the powder falling through the rotating disk to fall gently without being scattered. It is a good thing.

Preferably, the wing is disposed near a powder drop opening of the disk. According to this, the wing body functions as a baffle plate for the powder accompanying the transport air, and the powder can be reliably dropped through the opening. When the electrostatic coating machine for powder coating is a disk type, it is practically preferable to make the rotating disk detachable from the coating machine body. According to this, it is possible to prepare a plurality of disks with different openings, wings, etc. of the disks, and to use the disks properly according to the coating conditions.

For a bell-type electrostatic coating machine, substantially the same function and effect can be obtained by attaching the disk to the bell, but the rotation of the bell is used to open the disk. If a door that opens and closes according to the rotation speed of the disk is provided, the opening and closing of the door, that is, the amount of powder falling through the opening can be controlled by controlling the rotation speed of the bell.

[0015] In the application of the present invention, outside the coating machine,
An earth pin for capturing free ions may be provided, and the free ions may be removed by the earth pin. Note that, as described in detail in, for example, Japanese Patent Application Laid-Open No. 8-57364,
It is known that it occurs around a coating machine to lower the efficiency of applying a powder coating and to cause roughening of the coating film.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will be described below with reference to the accompanying drawings. First Embodiment FIG. 1 schematically shows a coating machine according to a first embodiment of the present invention.
The coating machine 1 of the first embodiment is a so-called rotary disk type electrostatic coating machine. The electrostatic coating machine 1 has an inner cylinder 2 having a circular cross section extending along the axis of the main body, and an outer cylinder 3 having a circular cross section having a larger diameter than the inner cylinder 2.
And the outer cylinder 3 are coaxially arranged. A rotating disk 4 is attached to a lower end of the outer cylinder 3.

The rotating disk 4 includes an upper disk 5 and a lower disk 6 which are vertically separated from each other. The upper and lower disks 5 and 6 each include a plurality of wings 7 arranged at equal intervals in the circumferential direction. Are connected via The wing body 7 is formed integrally with the upper surface of the lower disk 6 in this embodiment, but may be formed on the lower surface of the upper disk 5. The lower disc 6 also has a downwardly extending cylindrical skirt 8 on its lower surface, which skirt 8 is
And are arranged concentrically. Also, on the lower disk 6,
An opening 9 is provided in a portion adjacent to each wing body 7, through which the powder paint can be dropped, as will become clear later.

The rotary disk 4 has a sleeve 13 having a circular cross section extending upward from the periphery of the center opening 12 of the upper disk 5, and is formed between the inner peripheral surface of the sleeve 13 and the outer peripheral surface of the lower end of the outer cylinder 3. A bearing 14 is interposed between them. An upper cover member 15 is disposed above the rotating disk 4. The upper cover member 15 has a shape that covers the upper region of the upper disk 5 and surrounds the sleeve 13 described above. It is airtightly attached to.

In the coating machine 1, the space between the upper cover member 15 and the upper disk 5 in the rotating disk 4 constitutes a shaping air passage 16, and is sandwiched between the upper disk 5 and the lower disk 6. The space defined constitutes the paint discharge passage 17. The supply of the powder paint to the paint discharge passage 17 is performed through the paint supply passage 18 and the paint supply passage 1 is supplied.
Reference numeral 8 denotes a space defined between the inner cylinder 2 and the outer cylinder 3.

Two corona pins 20 are provided at the lower end portion of the paint supply passage 18, and the two corona pins 20 are arranged 180 degrees apart in the circumferential direction. A high voltage (for example, 0 to -100 kV) is applied to the corona pin 20 by a cascade (step-up unit) not shown, and this voltage can be arbitrarily adjusted. The powder paint conveyed by air from a paint source (not shown) is charged by the corona pin 20 while passing through the paint supply passage 18, and then moves to the paint discharge passage 17, and passes through the paint discharge passage 17. It moves outward in the radial direction and is discharged from the paint discharge port 21 (the discharge of the paint is indicated by an arrow A). The rotating disk 4 is provided with the upper disk 5 and the lower disk 6 in consideration of the magnitude of the neutralizing power of the free ions, the magnitude of the electric force lines, the magnitude of the aerial discharge amount, and the degree of reduction of the charge amount of the powder paint. It is preferably made of a material having some conductivity (10 ⁶ to 10 ¹² Ωm).

The air carrying the powder paint is discharged to the outside from the paint discharge port 21 through the paint supply passage 18 and the paint discharge passage 17 together with the paint. A rotational force is applied to the rotating disk 4, and the rotating force drives the rotating disk 4 to rotate in one direction. A part of the powder paint that has hit the wing body 7 together with the paint transport air falls from the lower disk 6 through the paint drop opening 9 and is protected by the skirt 8 while being protected from the influence of the air flow. To fall. The shaping air passage 16 is supplied with shaping air from a pressurized air source (not shown) via a hose 23.
An air outlet 24 formed at the outer peripheral edge of the upper disk 6 and the upper cover member 15 is discharged radially outward.

This rotating disk type electrostatic coating machine 1 is suitable for coating the inner surface of a bottomed cylindrical body such as a drum can. As is well known, a drum can has a plurality of outwardly projecting circumferential beads spaced apart from each other on a side wall (peripheral wall), and the circumferential bead forms a concave streak on an inner wall surface of the drum can. I have. In the coating machine 1, since the corona pin 20 is disposed in the coating material supply passage 18, it does not directly face the inner wall surface of the drum can, and therefore, the electric force generated between the inner surface of the drum and the opening end of the concave surface. Since the line is weak, the powder coating, which is a charged particle, easily enters the concave streak. In addition, an amount of paint necessary for painting the bottom surface of the drum can to a desired thickness can be supplied through the opening 9 of the lower disk 6.

In order to obtain a desired thickness of the bottom surface, the installation position of the opening 9 for dropping paint and the number or size of the openings may be adjusted. In order to easily perform this, the lower disk 6 is configured to be detachable from the upper disk 5 and a plurality of types of lower holes having different arrangement positions, sizes or numbers of the openings 9 and shapes of the wings. A side disk (an example of which is shown in FIG. 3) is prepared, and an appropriate lower disk 6 may be selected from these and attached to the upper disk. Further, if free ions generated around the coating machine 1 are to be removed, as shown in FIG.
It is preferable to provide a ground pin 25 on the bottom.

Second Embodiment FIG. 4 shows an outline of a coating machine according to a second embodiment of the present invention.
The coating machine 30 of the second embodiment is a so-called center feed type bell-type electrostatic coating machine. Bell type coating machine 30
Paint supply pipe 3 having a circular cross section arranged coaxially with the axis of the main body
1 and a bell 32 is integrally provided at the tip of the paint supply pipe 31. Around the paint supply pipe 31, there is a main body cover 33 arranged at an interval, and between the main body cover 33 and the paint supply pipe 31, an air turbine 34 and a plurality of axially spaced apart pipes are provided. A bearing 35 is provided. The paint supply pipe 31 and the bell 32 are driven to rotate by the air turbine 34 receiving turbine air. The bearing 35b excluding the metal bearing 35a among the plurality of bearings 35 is made of an insulating resin material. The paint supply pipe 31 has a corona pin 20 provided at a mounting portion of the metal bearing 35a, and a high voltage from the cascade 36 shown in FIG. 5 is applied to the corona pin 20 via the metal bearing 35a. .

The bell 32 has a hub 3 fixed to its inner surface.
7, and a disk 39 is mounted via the hub 37 and the support post 38. The disk 39 has a frame 40. The frame body 40 has a center circular portion 41 and four openings 42 (FIG. 7) around the circular portion 41 at equal intervals in the circumferential direction.
), And each opening 42 is provided with a door 44 for opening and closing the opening. In addition,
Reference numeral 45 in FIG. 6 indicates an insertion hole for a mounting bolt. The door 44 is rotatably attached to the frame body 40 on the leading side in the rotation direction (arrow B) of the disk 39, and is opened and closed by rotation / stop of the disk 39. The means for attaching the door 44 may be, for example, a hinge or a living hinge 45. Also, the disk 39
Is preferably made of a synthetic resin having some conductivity (10 ⁶ to 10 ¹² Ωm).

The powder paint conveyed by air from a paint source (not shown) is supplied to the center of the bell 32 through a paint supply pipe 31, and then moves along the inner wall of the bell 32 that expands to form the bell 32. The paint is discharged to the outside from the peripheral edge, hits the disk 39, moves along the upper surface of the disk 39, and is discharged radially outward from the peripheral edge of the disk 39. The powder paint discharged from the periphery of the disc 39 is charged by the corona pin 20 in the paint supply pipe 31 before reaching the bell 32. In this embodiment, the bell cover 47 disposed around the bell 32 forms a sheping air passage 48 between the bell cover 47 and the bell 32.

The disk 39 attached to the bell type coating machine 30 responds to the rotation speed of the bell 32, and when the rotation of the bell 32 is stopped or the rotation speed of the bell 32 becomes low as shown in FIG. And the powder P
Drop through the opening 42 of. On the other hand, when the rotation speed of the bell 32 increases, as shown in FIG. 8, the door 44 automatically closes, and most of the powder P moving along the disk 39 is discharged radially outward. .

The coating machine 3 provided with such a disk 39
0 is suitable for coating the inner surface of a bottomed cylindrical body such as a drum can in the same manner as the coating machine 1 of the first embodiment, and a bell 32 is used to apply a desired film thickness to the bottom surface of the drum can. Can be controlled. Even in this embodiment, the corona pin 2
Because 0 does not directly face the inner wall of the drum,
The lines of electric force generated between the concave end surface and the open end are weak, and therefore the powder coating material, which is a charged particle, easily enters the concave end surface.

Comparative Test Regarding the coating of the inner surface of the side wall of the drum can, a comparative test was performed using the rotating disk type coating machine 1 of the first embodiment to compare with the conventional example. As a conventional example to be compared, a conventional rotary disk type electrostatic coating machine was used (rotation speed of disk: 10).
0r.pm). The various conditions of the test are listed below.

(1) Coating object: drum (inner diameter: 5
(2) Powder paint discharge amount: 360 g / min. (3) Applied voltage: -60 kv (4) Paint transport air: 4.0 kgf / cm ² (5) Painting distance: 157 mm (60 mm, internal height: 850 mm) 6) Other conditions are as shown in FIG.

As shown in FIG. 10A, the drum 5
Numeral 0 has a bead 52 extending in the circumferential direction on the side wall 51, and each film in a nearby portion including the inside of the bead 52 (location a, location b, location c, location d in FIG. 10B). Table 1 shows the result of the thickness check. The measurement lines A, B, C, and D in Table 1 are 90 ° in the circumferential direction of the drum 50.
It means four vertical lines taken at intervals, and the film thickness was measured at the above-mentioned locations a, b, c, and d for each measurement line.

Table 1 a place b place c place d place Conventional example A line 274 μm 240 μm 609 μm 232 μm B line 257 μm 268 μm 455 μm 257 μm C line 249 μm 280 μm 400 μm 255 μm D line 237 μm 257 μm 535 μm 242 μm First embodiment μm 236 μm 236 μm Line 234μm 280μm 379μm 260μm C line 240μm 231μm 363μm 224μm D line 210μm 252μm 490μm 262μm

When Table 1 was examined, the difference in the film thickness between the measurement point b on the upper side wall and the measurement point c on the lower side wall of the bead 52 showed that the conventional coating machine 1 It can be seen that the size is smaller than that of the painting machine. This is the first
In the coating machine 1 of the embodiment, the lines of electric force generated are weaker than those of the conventional one, which indicates that the powder coating material easily enters the inside of the bead 52.

[Brief description of the drawings]

FIG. 1 is an enlarged schematic view of a main part of a rotary disk type electrostatic coating machine according to a first embodiment.

FIG. 2 is a plan view of a disc mounted on the coating machine in FIG. 1;

FIG. 3 is a plan view of a modified example of a disk mounted on the coating machine in FIG. 1;

FIG. 4 is an enlarged schematic view of a main part of a bell type electrostatic coating machine according to a second embodiment on which a disk is mounted.

FIG. 5 is an enlarged schematic view of a main part of a main part of the coating machine shown in FIG. 4;

FIG. 6 is a plan view of a disc mounted on the coating machine in FIG. 4;

FIG. 7 is an explanatory view showing a state in which the rotation of the bell type electrostatic coating machine in FIG. 4 is stopped.

FIG. 8 is an explanatory view showing an aspect when the bell type electrostatic coating machine of FIG. 4 is rotating at high speed.

FIG. 9 is a view for explaining the coating conditions in a comparative test with the related art.

FIG. 10 (a) shows a drum which is an object to be coated,
(B) is a longitudinal sectional view of a drum for explaining a film thickness measuring point.

[Description of Signs] 1 rotating disk type coating machine 4 rotating disk 7 wing body 8 skirt 9 paint opening 17 paint release passage 18 paint supply passage 20 corona pin 39 disk for bell type coating machine 42 disk opening 44 door

Claims (8)

[Claims] 1. A rotating disk rotating in a horizontal plane,
An electrostatic coating machine that discharges powder paint outward from an outer peripheral edge of the disc, wherein a corona electrode is provided in a paint supply passage that supplies powder paint to the rotating disc, wherein the disc includes: An electrostatic coating machine for powder coating, wherein a plurality of openings through which paint passes downward are formed. 2. The rotating disk is rotatably mounted on a coating machine main body, and the rotating disk is provided with a wing body disposed facing a paint discharge passage of the rotating disk. 1. An electrostatic coating machine for powder coating. 3. The electrostatic coating machine for powder coating according to claim 2, wherein said wing body is disposed near an opening of said disk. 4. The powder coating electrostatic coating machine according to claim 1, wherein said powder coating electrostatic coating machine is a disk type coating machine.
Item electrostatic coating machine for powder coating. 5. The electrostatic coating machine for powder coating according to claim 4, wherein said rotating disk is detachable from a coating machine main body. 6. The electrostatic coating machine is a bell type, and the rotating disk is detachably attached to the bell.
The electrostatic coating machine for powder coating according to claim 1. 7. The electrostatic coating machine for powder coating according to claim 6, wherein a door is provided at an opening of said disk. 8. A powder type paint is supplied to the center of the bell through a paint supply passage extending along the axis of the main body, and is attached to a bell of a bell type electrostatic powder coating machine having a corona electrode disposed in the paint supply passage. An opening having a plurality of opening / closing doors is formed in the disk, and the opening / closing door is hinged to a main body of the disk, and takes a closed position by rotation of the bell. Features disk.