JPS604757B2 - Method for spraying can body protective film on cans - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to the manufacture and inner surface coating of a so-called three-piece can body consisting of a lid plate, a can cover plate, and a bottom plate.

Conventionally, there are many types of tin cans that can be filled with a wide variety of contents, including the acidity of the contents,
Due to various conditions such as toughness, it has been pointed out that the inside of the can becomes discolored and corroded, as well as the precipitation of tin and iron. In order to eliminate these drawbacks, the inner surface of the can is painted after the can body is created.

This inner surface coating is applied to three-piece cans, in which case the can body is rotated after cylindrical forming and flange processing to reduce the processing steps after paint spraying and to reduce damage to the paint due to post-painting processing. At the same time, paint was being sprayed on the inside surface. (See Figures 1 and 2). However, the cans 8 and 10, which are simply cylindrically formed, are weak against external pressure and easily deform, are often not perfectly round, and are deformed when pressed by a rotary rotor to rotate the can body.

If it is not a perfect circle, the coating may become uneven due to changes in the area facing the spray coating means or changes in the degree of flow. Therefore, as shown in FIG. 2, a flange portion 15 was provided at the same end of the can 8 to prevent deformation of the cylindrical can chest. As shown, the coating on the flange 15 is thinner than the coating 21 on the center of the can, and in addition, the coating 22 on the shoulder of the flange is applied to the inner surface of the can while rotating it. Due to the centrifugal force caused by the rotation of the can body, the paint flows to the tip 16 of the flange portion, so that the paint on the curved portion is the thinnest. Due to the non-uniformity of the coating inside the can as described above, the flange portion 15 in particular is susceptible to damage to the coating due to contact with the vertical direction of the lid plate and bottom plate, and this cannot be said to be sufficiently prevented.

The present invention eliminates the above-mentioned drawbacks through a simple procedure, and has various advantages as described below.

In the present invention, when creating a can body, a neck portion 17 is created by reducing the diameter at positions 12 and 12' near both ends of the can body after or simultaneously with cylindrical molding (hereinafter referred to as necking).

After the necking process is performed, the inner surface of the can Tsukioka is spray-painted before the flange is processed. (See Figure 4). In this way, since the netting process is performed without performing flange processing,
In the can bodies according to the present invention, the diameters of the end portions 12 of the cans 8 and 10 are smaller than the diameter of the middle portion 11 of the can body, and the end portions 12 are not widened. When paint is sprayed onto the inner surface of the can body 10 while rotating, the vicinity 13 of the can body end portion, which was conventionally the flange portion 15, becomes the neck portion 17 in the present invention.
Since the cross-sectional shape is not a morning glory-like opening, the coating near the same end 13 of the can is prevented from becoming thin. Therefore, even if flange processing and can lid seaming are performed after spray painting, the end of the can body can be seamed without any defects such as bare metal appearing because the coating has been sufficiently applied. This prevents the defect that most of the corrosion of the can body occurs near the seams. Furthermore, after spray painting inside the can, when transferring the can to the same dryer using a belt, roller, etc., conventionally, the end portion 13 of the can has a larger diameter than the center portion 11 of the can 8 as a flange portion 15. Since the painted part faces outward, contact between the guide or the can body during transportation can cause paint to peel off and hardened paint to adhere to the guide.
In contrast to the can 8 which was subjected to the netting process according to the present invention, it was a cause of poor tightening in later can lid binding.
This is because the diameter of the can body end portion 13 is smaller than the diameter of the can body center 11, and because the painted part does not face outward, the ear end portions 12 do not touch when the cans 8 come into contact with each other and the comparison guide. It also helps reduce vertical winding defects. Furthermore, since the diameters of the can body center portion 11 and the neck portion 17 are different, the can body according to the present invention is more resistant to pressure than the conventional can body that is simply cylindrically formed, and the can body can be rotated more easily. In this process, deformation caused by the pressure roller is prevented, and deformation is also less likely to occur during transport, thereby reducing the incidence of defective products. As described above, in the production of can ears, the present invention involves creating a can body that is necked after cylindrical molding or at the same time as cylindrical molding, and then spraying the inner surface of the can body before performing flange processing on the can body. Therefore, by making slight improvements to the conventional can arm manufacturing and painting procedures, it is possible to prevent the occurrence of defective products during the transfer of can bodies and the tightening of can lids. It has many advantages such as preventing discoloration, corrosion, and precipitation of tin and iron.

In addition, for 3-piece cans, not only when both ends of the can body are closed, but also when either the bottom plate or the lid plate is seamed, if necking is applied to the opening at the other end, the main body can be closed. It goes without saying that the advantages of the invention and the anti-corrosion can coating are not limited to tin cans.

[Brief explanation of the drawing]

Figures 1 and 2 are diagrams showing the conventional inner surface coating, Figure 3 is an enlarged sectional view of the main part of the can body of the secondary can body, and Figure 4 is a diagram showing the inner surface coating of the can body according to the present invention. be. 10 = Can Tsukioka, 11: Center of can 8, 12 = Can and end, 13 = Near end, 15 = Flange, 16 = Tip of flange, 17 = Neck, 21 = Painted center, 22 = Painted flange shoulder. Figure 1 Figure 2 Figure 3 Figure 4

Claims (1)

[Claims] 1. A method for spraying and painting a can body with a protective film, which is characterized in that when producing a can body, the can body is formed into a cylinder, subjected to a netting process, and then a protective film paint is sprayed onto the inner surface while rotating the can body.