JPH08299857A - Applicator for resin powder - Google Patents

Abstract

PURPOSE: To apply resin powder promptly and stably to the welded joint part of a can cylinder. CONSTITUTION: In an applicator for resin powder 11, the powder 11 to be stuck to the welded joint part 10a of the inside of a can cylinder 10 which travels continuously is held in a suspended state and charged to be applied electrostatically to the joint part 10a. A powder diffusing part 21b which holds the powder 11 in a suspended state is installed in the traveling direction of the can cylinder 10 to face the joint part 10a. A conductive metal plate 23 is arranged in the diffusion part 21b with its one side marginal part positioned in parallel with the joint part 10a. A numbers of edge parts 23a of the same shape are formed projectingly toward the joint part 10a in one side marginal part of metal plate 23, and the metal plate 23 and the can cylinder 10 are charged oppositely to each other.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a device for coating a weld seam on the inner surface side of a can body with a molten film of resin powder, mainly for the purpose of preventing corrosion, and particularly to welding on the inner surface side of the can body. The present invention relates to a device for stably applying resin powder to a seam portion.

[0002]

2. Description of the Related Art The inner surface and outer surface of a can body of a three-piece can used as a container for food and drink are subjected to surface treatment such as painting, offset printing or laminating treatment in order to prevent corrosion and decoration. Has been done. Although such a treatment is performed while the can material is in a flat plate state, roll processing and welding of the overlapped side edges are performed in order to process it into a can body. It is done by leaving the part that will be the side edge. Then, a film for mainly preventing corrosion is formed in a post-process in the welded seam portion including the portion not subjected to the surface treatment.

This film is generally composed of a cured film obtained by drying and baking a thermosetting resin solution to cure it, or a molten film of resin powder. Japanese Patent Publication No. 1-46184 discloses an example of an apparatus for applying a resin powder to a weld seam portion of a can body to form a molten coating of the resin powder. This is shown in FIG. 4 and briefly described.

This resin powder coating device is provided with an opening 2 facing the welding seam portion of the traveling can body 1 and configured to form a dense flow of the resin powder. A plurality of corona charging pins 3 for charging the resin powder are arranged in the opening 2 in a line in the longitudinal direction. By connecting the corona charging pin 3 and the can body 1 to a DC power source, the resin powder introduced into the opening 2 is charged and electrically attached to the welding seam portion of the can body 1, It is configured to perform electrostatic coating of resin powder.

[0005]

[Problems to be Solved by the Invention] Japanese Patent Publication No. 1-46184
The powder coating device disclosed in Japanese Patent Laid-Open Publication No. 9-187242 not only effectively charges the powder that enters the opening 2, but also charges the powder that has rebounded without adhering to the inner surface of the can body so that it can be further charged. It is considered that the coating can be efficiently performed because the time can be lengthened.

However, at the present time when it is required to increase the can making speed to reduce the manufacturing cost, the powder coating apparatus disclosed in Japanese Patent Publication No. 46184/1989 has not yet been solved in order to meet this demand. Turns out there is a problem that must be addressed.

That is, in order to accelerate the charging of the resin powder to cope with the speedup and to rapidly apply a predetermined amount of the resin powder,
Although it is necessary to take measures such as increasing the number of corona charging pins to increase the coating efficiency, it is difficult to adjust the heights of the corona charging pins 3 arranged to be equal to each other completely. A uniform electric field is not formed between the tip and the weld seam on the inner surface of the can body, and an unequal electric field is likely to be generated.If the electric charge is increased while maintaining this unequal electric field, a discharge will occur between the tip of the corona charging pin and the can body. And the powder adheres to the tip of the corona charging pin to prevent the charging action. As a result, there is an inconvenience that the resin powder is not applied stably and the resin powder is not applied uniformly.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a resin powder coating device capable of stably coating the resin powder on the weld seam portion of the can body. It is intended.

[0009]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention holds in a floating state resin powder to be attached to a weld seam portion on the inner surface side of a can barrel that continuously runs,
In addition, in a resin powder coating device that electrostatically coats the resin powder on the welded seam portion of the can body, a powder diffusing section that holds the resin powder in a floating state is used for running the can body. While being provided along the direction and facing the welding seam portion, a conductive metal plate is disposed in the powder diffusion portion with one side edge thereof being substantially parallel to the welding seam portion, A large number of sharp portions are formed on the one side edge of the metal plate so as to project toward the welded seam portion, and the metal plate and the can body are charged with opposite polarities. .

[0010]

According to the present invention, the resin powder adhered to the welded seam portion of the can body is held in a floating state in the powder diffusion portion. The conductive metal plate disposed in the powder diffusion section faces the welding seam portion of the can body with the floating resin powder interposed therebetween, and the metal plate and the can body are charged with opposite polarities. Therefore, the resin powder charged from the metal plate is sucked toward the welding seam portion of the can body and adheres thereto. In that case, the electric charge is mainly applied to the resin powder from the sharp portion where the electric charge is concentrated, and the sharp portion is continuously formed on one side edge of the metal plate, and the tip of each of the plural sharp portions is arranged. Since the facing distance between the and the welded part of the can body can be made almost constant without performing it for each sharp part, it is easy to make the electric field between each sharp part and the can body uniform, and Does not occur. Therefore, the resin powder is stably charged by the sharp portion of the metal member, and uniformly flies toward the welding seam portion of the traveling can body, and is evenly distributed to the welding seam portion of the can body by Coulomb force. Adhere to.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the embodiments shown in FIGS. In FIG. 3, the coating apparatus for resin powder of this embodiment is mainly equipped with a welding seam and its vicinity (hereinafter referred to as a welding seam portion 10a) in a cylindrical barrel 10 to prevent corrosion. The resin powder 11 (hereinafter referred to as powder) made of epoxy resin, nylon resin, polyester resin, or the like is applied.

In this resin powder coating device, a welding means 12 for welding both side edges of a can-making material which has been formed into a cylindrical shape and is stacked, and a can body 10 formed by the welding means 12 are continuously connected. Transporting means 13 for efficiently transporting, and cooling means 14 for cooling at least the welding seam portion 10a of the can body 10.
A coating means 15 for electrostatically coating the powder 11 on the weld seam portion 10a on the inner surface side of the can body 10 cooled by the cooling means 14, and the weld seam portion 1 of the can body 10 being conveyed.
Suction means 16 disposed substantially opposite to coating means 15 with 0a interposed, and weld seam portion 1 on the inner surface side of can body 10.
Heating means 17 for heating the welded seam portion 10a of the can body 10 so as to form a molten coating of the powder 11 applied to 0a.
It has and.

Each means will be specifically described below. The welding means 12 includes a pair of electrode rollers 18a and 18b arranged so that their circumferential surfaces are opposed to each other, and both sides are overlapped by roll-forming a plate-shaped can-making material cut into a predetermined size. Electrode rollers 18 whose edges are arranged to face each other
It is configured to obtain a can body 10 by passing between a and 18b and performing resistance mash seam welding. Then, an injection nozzle of an inert gas (for example, N ₂ gas) (not shown)
It is appropriately provided toward the welding position by the electrode rollers 18a and 18b, and the welding by the welding means 12 is performed in an inert gas atmosphere. Therefore, the welding seam portion 10a of the can body 10 is prevented from being oxidized, and the powder 1
The molten coating film No. 1 is formed well.

The conveying means 13 conveys the can body 10 obtained by the welding means 12 with the weld seam portion 10a thereof positioned on the upper side, and rotates with a drive roller 19a connected to a drive shaft (not shown). Driven roller 1 held freely
A belt 20 made of an appropriate rubber material, which is hung on the 9b.
Are arranged so as to come into contact with both sides of the can body 10 led out from the welding means 12. Then, the drive roller 19a is driven so that the can body 10 sent out from the welding means 12 is continuously conveyed at a speed of about 100 m (1.7 m / s) per minute while keeping a predetermined interval. ing.

The cooling means 14 is arranged between the welding means 12 and the coating means 15, and cools the air cooled to a predetermined temperature supplied from an air supply source (not shown) through the chiller to the can body. A predetermined range from above 10, that is, the can body 10
It is configured to be sprayed onto the welded seam portion 10a at a predetermined flow rate.

The temperature of the weld seam portion 10a of the can body 10 cooled by the cooling means 14 is set to a temperature (for example, about 55 ° C.) lower than the softening temperature (about 60 ° C.) of the powder 11 and the cooling is performed. An increase in the heat load of the means 14 and of the heating means 17 arranged subsequently is avoided.

The coating means 15 is for coating the welding seam portion 10a of the can body 10 with the powder 11 so that the coating film formed by the powder 11 has a thickness of about 50 μm. As shown in FIG. 3, a can body 1 to be conveyed.
The powder nozzle main body 21a is provided on the inner peripheral side of 0, and the earth brush 22 is in contact with the outer surface of the can body 10 passing through the coating means 15 and is grounded.

The powder nozzle body 21a is a rectangular parallelepiped block-shaped member made of an insulating material such as synthetic resin, and has a size that can be inserted into the can body 10. The can body 10 is positioned inside the can body 10 which is continuously conveyed by the conveying means 13.
Are arranged along the traveling direction of.

On the upper surface side of the powder nozzle body 21a, a powder nozzle portion 21b which is recessed in a rectangular shape is formed along the longitudinal direction thereof, and the powder nozzle portion 21b is formed.
Along the longitudinal direction of the bottom part of the metal plate, a metal electrode 23 made of a rectangular metal plate having abrasion resistance and conductivity (alloy tool steel in this example) is arranged.

The metal electrode 23 is for charging the powder 11, and the length of one side thereof is about 128 mm,
It has a thickness of 0.6 mm and one side of this is the powder nozzle 2
1b of the powder nozzle body so as to protrude near the bottom surface of 1b.
It is embedded in 1a. The side edge of the metal electrode 23 protruding into the powder nozzle portion 21b has a bottom of about 2 mm.
The same triangular pointed portions 23a having a height of about 1 mm and a triangular shape are continuously formed at substantially regular intervals (in the present example, the pointed portions are machined), and a charge is applied to the apex of each pointed portion 23a. Are concentrated. And this metal electrode 23
Is electrically connected to the negative pole of a static electricity generating device (multiplier) 24 arranged adjacent to the powder nozzle body 21a along the axial direction of the can body 10.
Further, the metal electrode 23 is installed such that one side portion thereof having a pointed portion 23a formed in a sawtooth shape is parallel to the inner surface of the can body 10.

Further, in the upper part of the powder nozzle body 21a, on the left and right sides sandwiching the powder nozzle portion 21b,
A pair of masking members 25, the tip portions of which are in sliding contact with the inner surface of the can body 10, are attached so that their heights can be adjusted. The masking member 25 is a brush member made of glass fiber having excellent heat resistance and abrasion resistance or a sheet member made of fluororesin in which glass fiber is woven, and is provided over substantially the entire length of the powder nozzle body 21a. The masking members 25 are arranged so as to be inclined so that the upper ends thereof are close to each other, and the intervals between the leading ends thereof are slightly wider than the width of the welding seam portion 10a of the can body 10.

Of the powder nozzle portion 21b, the can body 1
A powder supply path 26 for supplying the powder 11 to the powder nozzle portion 21b is connected to the rear side (so-called upstream side) of the transport direction 0. A powder recovery path 27 is connected to a portion of the powder nozzle portion 21b on the front side (so-called downstream side) in the transport direction of the can body 10. The powder supply path 26 and the powder recovery path 27 are tubes each having a small diameter, and are configured to carry the powder 11 by a carrier gas (for example, air). That is, the powder supply path 26 is connected to a powder reservoir (not shown) that stores the powder 11 in a fluidized state by the carrier air, and the powder 11 is charged from the powder reservoir by the carrier air to the powder nozzle portion 21b. It is designed to be supplied to. Further, the powder recovery path 27 is arranged so as to be folded back at the tip end side of the powder nozzle body 21a so as to extend to the rear side in the conveying direction of the inner peripheral side of the can body 10, and the powder recovery path 27 has a predetermined negative pressure. It is connected to a power source and is configured to suck and convey the powder 11 together with air from the powder nozzle portion 21b.

That is, the powder nozzle body 21a described above.
Then, in the upper portion of the powder nozzle portion 21b opening on the upper surface thereof, a space closed in the left-right direction with respect to the longitudinal direction is formed by the masking members 25, 25 and the inner surface of the can body 10 slidingly contacting the tip end thereof. The powder 11 supplied to the powder nozzle portion 21b together with the carrier air from the powder supply passage 26 is configured to be in a floating turbid state in the closed space portion. That is, the powder nozzle portion 21b and the masking member 25 form a powder diffusion portion.

Further, the powder 11 in the powder supply path 26
The pressure of the carrier air and the suction force in the powder recovery passage 27 are set to a pressure that keeps the floating turbid state of the powder 11 in the powder nozzle portion 21b, that is, the powder diffusion portion in a good state.

In the powder diffusing section, the powder 11 is charged by the metal electrode 23, and the powder 11 is attached and deposited on the inner surface of the can body 10 by an electric attraction force generated between the powder 11 and the inner surface of the body 10. It is like this.
Further, the excess powder 11 that could not be attached to the inner surface of the can body 10 is configured to be recovered from the powder recovery path 27.

Next, the suction means 16 will be described.
The suction means 16 is for collecting the powder 11 leaked to the outside without being attached to the inner surface of the can body 10.
A suction hood 16a having a width of about 20 mm and substantially the same length as the powder nozzle main body 21a is arranged so as to face the powder nozzle main body 21a with the can body 10 being conveyed interposed therebetween. The suction hood 16a is connected to a predetermined suction source (not shown) such as a suction port of a blower via a duct 16b. The suction pressure by the suction means 16 is set in the powder nozzle portion 21b by the powder 1
The pressure is set so that the floating turbidity of No. 1 is not disturbed.

Further, the heating means 17 is for melting the powder 11 applied to the welding seam portion 10a of the can body 10 to form a film, and is located on the downstream side of the applying means 15, that is, the can body 10. Are arranged on the front side in the transport direction of the. Since this heating means 17 needs to accurately heat the predetermined area coated with the powder 11, that is, the welding seam portion 10a of the can body 10 partitioned by the masking member 25, for example, a high frequency induction heating device is adopted. .

The operation of the above-mentioned powder coating device will be described below. The can-making material cut into a rectangular flat plate is roll-processed to be formed into a cylindrical shape.
Welding is performed by passing between 8a and 18b. In that case, since the non-oxidizing atmosphere is maintained by the injection of N ₂ gas or the like, oxidation of the weld seam portion 10a and its vicinity is prevented.

The can body 10 thus formed is sandwiched by the pair of rubber belts 20 in the conveying means 13 and conveyed at a high speed in the axial direction thereof, and when passing through the cooling means 14, the welding seam portion 10a. By blowing the cooling air toward the welding seam portion 10
a is cooled to a predetermined temperature, specifically, a temperature at which the powder 11 is not softened or melted. In that case,
The cooling air does not enter the inside of the powder nozzle body 21a in the coating means 15 in the next step, and the floating turbid state of the powder 11 inside the powder nozzle body 21a is not disturbed.

On the other hand, in the inside of the powder nozzle portion 21b of the coating means 15, from the powder supply passage 26 to the powder 11
Are supplied together with the carrier air, and as a result, the powder 11 is diffused in a floating turbid state inside the powder nozzle portion 21b. The metal electrode 23 is negatively charged by the multiplier 24,
On the other hand, since the can body 10 is grounded, the electric charges are concentrated on the sharp portions 23a on one side of the metal electrode 23 which are arranged facing the powder nozzle portion 21b. Therefore, the powder 11 in the floating turbid state receives an electric charge from the sharp portion 23a and is negatively charged.

On the other hand, the can barrel 10 having the welding seam portion 10a cooled to a predetermined temperature through the cooling means 14 has the coating means 15 with the inner surface of the welding seam portion 10a facing the powder nozzle portion 21b. Pass through. In that case,
While being grounded via the ground brush 22, a portion of the inner surface having a predetermined width sandwiching the welding seam portion 10a is partitioned by the masking member 25, so that the portion having the predetermined width floats on the powder 11. It is exposed to the powder diffusion part. Therefore, the powder 11 that is negatively charged and is floating is
It is attracted toward the inner surface of the can body 10 exposed with respect to b by an electric attraction force, and adheres to a portion having a predetermined width sandwiching the welding seam portion 10a.

When the powder 11 is charged as described above and is attached to the inner surface of the can body 10, the powder 1
Since each sharpened portion 23a that gives an electric charge to 1 is formed continuously on one side of one metal plate in the same shape,
Further, since the distance between the sharpened portions 23a and the inner surface of the can body 10 is parallel to each other and the whole is constant, a uniform electric field is formed between the two and the powder 11 is applied. Charged well and the metal electrode 23
It is possible to prevent electric discharge from occurring between the can body 10 and the can body 10. Therefore, even if the charge is increased, discharge is generated in the sharp portion 23a, and accordingly, the sharp portion 23a is discharged.
The powder 11 hardly adheres and accumulates on the surface, and even if the powder 11 adheres, it is sufficiently charged from the thick sharp portion.

Since the powder 11 is continuously supplied to the powder nozzle portion 21b from the powder supply passage 26 and is sucked from the powder recovery passage 27, the powder nozzle portion 21b always has a stable powder inside. Eleven floating turbid states are formed. Further, the powder 11 leaked to the outside of the can body 10 is sucked and collected by the suction hood 16a of the suction means 16, and the extra powder 11 is prevented from adhering to the can body 10 and peripheral devices. Further, although not particularly shown, a liquid resin is applied to the outer surface side of the welded seam portion 10a.

The can body 10 thus coated with the resin on the inner and outer surfaces of the weld seam portion 10a is conveyed to the heating means 17, where the weld seam portion 10a is heated and the powder applied to that portion is heated. 11 and the liquid resin melt to form a film.

In the above embodiment, the shape of the sharp portion 23a of the metal electrode 23 has a base of 2 mm and a height of 1 mm.
Although the shape of the scalene is approximately equilateral and the pitch of the vertices is about 2 mm, the shape and the pitch of the sharp portions 23a can be set appropriately and are not limited to those shown in the above embodiment. For example, the shape of the sharp portion 23a may be an isosceles triangle, or the height of the triangle may be further increased to set the pitch to 1
mm to 10 mm may be used.

[0036]

As described above, according to the resin powder coating apparatus of the present invention, the electrode for charging the resin powder has a structure in which a large number of sharp portions are formed on one side of the metal plate. And since these sharp portions are arranged so as to be substantially parallel to the inner surface of the can body, the potentials of the sharp portions become equal and the discharge between the sharp portions can be prevented in advance. As a result, it is possible to prevent inconveniences such as the resin being welded to any of the sharpened portions and the charge on the resin powder being insufficient due to the welding, resulting in abnormal application of the resin powder to the can body. Moreover, since an electric field is uniformly formed between the metal electrode and the can body, discharge between the electrode and the can body is prevented, and as a result, the resin powder is welded to a part of the inner surface of the can body. As a result, it is possible to prevent abnormalities such as non-uniform coating thickness of the resin powder and welding of the resin on the sharp portions of the metal electrode to hinder the charging action.

[Brief description of drawings]

FIG. 1 is an explanatory view schematically showing a coating means in an embodiment of the present invention.

FIG. 2 is a sectional view taken along line II-II of the coating means shown in FIG.

FIG. 3 is a perspective view schematically showing an overall configuration of the embodiment shown in FIG.

FIG. 4 is a schematic view showing an example of a conventional resin powder coating device.

[Explanation of symbols]

 10 Can Body 10a Welded Seam Part 11 Powder (Resin Powder) 15 Coating Means 21b Powder Nozzle Part 23 Metal Electrode 23a Sharp Point 24 Static Electricity Generating Means (Multiplier) 25 Masking Member

Claims (1)

[Claims] 1. A welding seam on the inner surface side of the can body that holds resin powder to be attached to a welding seam portion on the inner surface side of a continuously traveling can body and charges the resin powder. In a resin powder coating device for electrostatically coating a portion, a powder diffusing portion for holding the resin powder in a floating state is provided along the traveling direction of the can body and facing the welding seam portion, A conductive metal plate is arranged in the powder diffusion portion with one side edge thereof being substantially parallel to the welded seam portion, and a number of sharp portions are provided on the one side edge portion of the metal plate. An apparatus for coating resin powder, which is formed so as to project toward the welded seam portion, and the metal plate and the can body are charged with polarities opposite to each other.