JPH0417712B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a method for manufacturing a can body, and more particularly to a method for producing a can body, and more specifically to a can body manufacturing method, and more particularly to a can body manufacturing method, and more particularly to a can body manufacturing method, and more particularly to a can body manufacturing method. This invention relates to a method for manufacturing can bodies used for beer cans, etc.

(Prior art) In order to improve the corrosion resistance of the inner surface of the side seam of a can body, for example, the welded part of a welded can body, the inner surface of the welded part is powder coated while the can body is being transported, and the coating is protected by a coating film. A method to do this is disclosed in Japanese Patent Application Laid-open No. 56-2873,
Japanese Patent Application Laid-open No. 58-196869 and U.S. Patent Specification No.
It has been proposed in No. 3526027, etc.

In these conventional methods, the can bodies are transferred (in the axial direction) such that a predetermined distance is left between adjacent can bodies. As a result, a relatively large amount of powder paint spills out from the gap between adjacent can bodies, reducing coating efficiency, and the electrically charged powder paint adheres to the outer surface near both ends of the side seam.
If the powder coating is a colored (for example, white) powder coating, the problem arises that the outer surface is stained and the commercial value of the product is reduced.

Furthermore, in order to prevent the above-mentioned flying powder paint from scattering and contaminating the surrounding area of the equipment, and to collect and reuse the powder paint in-line, a projector is installed on the outside of the can body near the coating nozzle. The problem is that a powder paint collection device with a complex mechanism must be installed, including a suction hood to suck up the paint, and a filter to remove factory dust such as iron powder mixed into the powder paint during suction. occurs.

Furthermore, the powder paint sprayed into the can tends to electrostatically adhere to the inner surface of the can other than the side seam, but the powder paint electrostatically applied only to the side seam and its vicinity is heated and fused to form a coating film. Therefore, the powder paint adhering to the inner surface of the can other than the above-mentioned side seam remains in a state where it is easily detached as a powder. This powder tends to get mixed into the contents of canned goods produced from this can body, causing discomfort to consumers and sometimes causing hygiene problems.

(Problems to be Solved by the Invention) The present invention has a high coating efficiency of powder coating, and prevents the outer surface near both ends of the side seam from being stained by the applied powder coating or by spouting powder. The inner surface of the side seam part eliminates the risk of damaging the commercial value of the product due to electrostatic adhesion of body paint to the inner surface of the can other than the side seam part, and does not require a complex powder paint collection device including a suction hood. An object of the present invention is to provide a method for producing a can body covered with a coating film formed by powder coating.

(Means for Solving the Problems) The method for manufacturing a can body of the present invention is a method for manufacturing a can body in which the inner surface of the side seam portion is coated with a coating film, and the method includes: Based on the transfer speed, the speed of the belt conveyor that transfers the can bodies with side seam portions formed therein is controlled so that the distance between adjacent can bodies becomes substantially 0 mm, while conveying the can bodies. The inner surface of the side seam of the can body is electrostatically powder coated by ejecting powder paint from the spout of the powder coating nozzle, and the uncoated powder paint is transferred to the powder coating nozzle. It is characterized in that the collection is carried out through a conduit having an inlet extending forwardly and backwardly along the side seam part in continuation with the spouting outlet.

Here, the term “substantially 0 mm spacing” means that the spacing is 0 to 3 mm.
mm, more preferably 0 to 1 mm, and still more preferably 0 to 0.5 mm. Can bodies include pine seam electric resistance welded can bodies, laser welded can bodies, etc.

(Function) The can bodies are transferred by controlling the speed of the belt conveyor that transfers the can bodies so that the distance between adjacent can bodies is substantially 0 mm, so the distance between adjacent can bodies is substantially reduced. 0 mm and uncoated powder coating is passed through a simply constructed conduit that has an inlet that extends forward and rearward continuously from the spout of the powder coating nozzle and along the side seam. Therefore, when the gap between adjacent cans passes through the spout, the powder paint sprayed on the inner surface of the side seam does not substantially escape from the can. Therefore, the coating efficiency is improved, and there is virtually no powder coating on the outer surface near both ends of the side seam, and even if it is coated, the amount or area of the powder coating will be smaller than that of the product. In addition, a powder coating recovery device with a complicated mechanism including a suction hood is not required.

Of the powder coating sprayed onto the inner surface of the side seam portion, a portion having a thickness exceeding a certain level is not electrostatically coated on the inner surface of the side seam portion and remains uncoated. However, the conduit for collecting the powder coating has an inlet that extends forward and backward along the side seam part in continuation with the jet nozzle of the powder coating nozzle. While the powder coating is being sprayed onto the inner surface of the side seam, uncoated powder, including powder coating that is about to scatter toward the inner surface of the can other than the side seam, Substantially all of the paint is recovered through the inlet. Therefore, unapplied powder coating remains on the inner surface of the can body other than the side seam area, and mixes with the contents of the can, causing discomfort to consumers and sometimes causing hygiene problems. There is no risk of lowering the product value.

(Example) Hereinafter, an example of the present invention regarding a pine seam welded can body will be described.

In FIG. 1, reference numeral 1 denotes a can body preform, and while being transported in the direction of arrow A, a wire electrode (not shown) is connected to the overlapped portion 2 by a pair of opposing outer electrode rolls 3 and inner electrode rolls 4.
The pine seam is electrically resistance welded to form a welded can body 6 having a welded portion 5.

Next, the inner surface of the welded portion 5 of the welded can body 6 is electrostatically powder-coated with powder paint 10 that is ejected from the spout 8a of the powder coating nozzle 8 built into the horn 7 and charged by the corona pin 9. The corona pin 9 is connected to a high voltage DC power supply (not shown) via a conductor 15. Reference numeral 11 denotes a coating layer of powder coating, and as shown in FIG. 2, its width is regulated to a predetermined value by a pair of opposing brushes 12 that contact near both sides of the inner surface of the welded part. Ru. The brush 12 is preferably formed from ceramic fibers such as glass fibers.

Next, an outer surface repair paint is applied to the outer surface of the welding part by an outer surface repairing device (not shown), and then the powder paint of the coating layer 11 is heated and melted by a heating device (not shown), and welded to the inner surface of the welded part (including the vicinity). and is formed on the inner surface repair coating.

Powder coatings 10' and 10'' that have not been electrostatically applied to the welding part 5 are applied to the spout 8a of the powder coating nozzle 8.
is fed in the direction of the arrow through conduits 13 and 14 with inlets 13a and 14a extending along the weld 5 successively forward (in the direction of transition of the welded can body 6) and backwards into the powder tank. (not shown) to be collected. 16 is a grounding brush.

The welded can bodies 6 are spaced between adjacent welded can bodies 6 = 30
the distance x is substantially 0 mm, i.e. 0 to 3 mm,
More preferably 0 to 1 mm, still more preferably 0 to 1 mm
Powder coating is applied while being transferred so that the thickness is 0.5mm. It is most desirable that the interval x be exactly 0 mm, but in reality, as shown in Figure 3,
Because of small protrusions 17 and the like that protrude in the axial direction during welding at both ends of the welded part 5, it is extremely difficult to set the interval x exactly to 0 mm, and the interval x is usually about 0.2 to 0.4 mm. be.

Control of the interval x is performed as follows. The transition speed V ₁ of the can body preform 1 during welding, ie the speed V ₁ when the welded can body 6 leaves between the electrode rolls 3 and 4, is equal to the circumferential speed of the outer electrode roll 3, which is the drive roll. The outer electrode roll 3 is the motor 1
The peripheral speed V ₁ of the outer electrode roll 3 is proportional to the rotational speed of the motor 18 . Therefore, if the output of the pulse generator 20 that detects the rotation speed of the motor 18 is _P1 , then _the following relationship holds true: _V1 = _C1P1 ...(1). Here C ₁ is a constant.

On the other hand, since the welded can body 6 after leaving between the electrode rolls 3 and 4 is transferred by the rubber belt conveyor 21, the transfer speed of the welded can body 6 during powder coating is V ₂
is equal to the traveling speed of the conveyor 21. The conveyor 21 is driven by a motor 22 and a drive roll 24 via a power transmission mechanism 23 . Therefore, if the output of the pulse generator 25 that detects the rotational speed of the motor 22 is P ₂ , then the following relationship holds true: V ₂ =C ₂ P ₂ (2). Here C ₂ is a constant.

Therefore, the outputs P ₁ and P ₂ of the pulse generators 20 and 25 are inputted to the speed controller 26 of the motor 22, and C ₂ P ₂ /C ₁ P ₁ and therefore V ₂ /V ₁ is a predetermined value slightly greater than 1. , for example, by controlling the rotational speed of the motor 22 to be 1.005,
The distance x of 30 between adjacent welded can bodies 6 during powder coating can be made substantially 0 mm.

Next, a specific example will be explained.

A tin-plated steel plate with a thickness of 0.30 mm, with a phenol epoxy coating on the inner surface and a dark blue printed film on the outer surface, leaving an exposed margin of 1.5 mm width on both edges to be welded. Blank (tinning amount
5.6g/m ² ) with an overlapping width of 0.4mm, an outer electrode roll 3 (outer diameter
115mm, peripheral speed V ₁ 45m/min), inner electrode roll 4
A welded can body 6 having a height of 182 mm, an outer diameter of 153 mm, and a welded part thickness of about 0.45 mm was produced by welding the can with a pine seam (outer diameter: 90 mm) using a copper wire electrode.

The inner surface of the welded part 5 of this welded can body 6 was coated with a linear polyester powder coating (melting point 170°C, titanium white content 16% by weight,
Powder size distribution 7 to 125 μm, average particle size 85 μm; VP91 White (registered trademark) manufactured by Vanicolor Co., Ltd.) was sprayed, and at the same time, uncoated powder paints 10' and 10'' were collected through conduits 13 and 14. A coating layer 11 having a width of approximately 10 mm and a thickness of approximately 80 to 90 μm (after forming a coating film) was formed.At this time, the corona pin 9 was coated with approximately -
A negative voltage of 20 kV was applied. Furthermore, this conduit 1
According to No. 3 and 14, unapplied powder paint was not collected. Next, a transparent epoxy-urea paint was applied to the outer surface of the welded portion 5.

Next, a hot air blowing device (not shown) located downstream of the nozzle 8 blows hot air onto the welded area from the outside to melt the powder paint on the coating layer 11 to form a coating film, and also to form an external paint film. I was curious. The thickness of the outer coating film after curing was 1 to 2 μm.

During the above coating, the traveling speed _V2 of the belt conveyor 21 was changed to perform powder coating at various intervals x as shown in FIG. The length hmm of the white dirt coating 28 (FIG. 3) formed on the outer surface of both ends of the welded portion 5 was measured. At the same time, the amount of powder paint scattered outside from the can body 6 between the can bodies 30 was determined as follows. A suction hood with a filter is provided below the nozzle 8 and close to the outer surface of the can body 6, and suction is carried out at a predetermined air volume.After a predetermined time has elapsed, the air passes through the gap 30, accumulates on the filter, and is collected by the suction hood. The amount W of powder coating was measured. The results are shown in Figure 4.

When double seaming the lid plate and bottom plate, the height of the edge of the can body to be seamed is approximately 5 mm, so if the distance x is less than 3 mm, the coating film 28 will not be visible after seaming. .

(Effects of the Invention) The method of manufacturing a can whose side seam inner surface is coated with powder coating according to the present invention has the following effects.

There is no risk of unapplied powder coating remaining on the inner surface of the can other than the side seam and contaminating the contents of the can, reducing the product value.

No need to install a complicated external powder paint recovery device including a suction hood or filter.
The coating efficiency is improved, and there is virtually no powder coating on the outer surface near both ends of the side seam, and even if powder coating does get coated, the amount or area of the coating will reduce the commercial value of the product. This is a level that does not decrease.

[Brief explanation of drawings]

FIG. 1 is an explanatory partially cutaway front view of an example of an apparatus for implementing the method of the present invention, FIG. 2 is a longitudinal cross-sectional view taken along the line - in FIG. 1, and FIG. Front view including welds of the manufactured can body example, No. 4
The figure is a diagram showing an example of the relationship between the distance between can bodies, the length of dirt on the outer surface of the can bodies, and the amount of powder paint scattered outside the can bodies. 5... Welded part (side seam part), 6... Welded can body (can body), 8... Powder coating nozzle, 8a...
Spout nozzle, 10...Powder coating, 11...Coating layer, 1
3, 14... conduit, 13a, 14a... inlet,
x...interval, 21...belt conveyor.

Claims (1)

[Claims] 1. Based on the transfer speed of the can bodies with side seams being formed, the speed of the belt conveyor that transfers the can bodies with side seams formed is adjusted so that the distance between adjacent can bodies becomes substantially 0 mm. While the can body is being controlled and transferred, powder coating is sprayed from a powder coating nozzle onto the inner surface of the side seam of the can body, and the inner surface is electrostatically powder coated, removing any remaining powder paint. is collected through a conduit having an inlet extending forward and backward continuously from the spout of the powder coating nozzle and along the side seam, the inner surface of the side seam being covered with a coating film. A method for manufacturing a can body.