JPS633663B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a can body with an integral bottom formed by drawing and ironing, a so-called DI can body, and an annular protruding portion on the periphery of the can bottom (this serves as legs when the can body stands upright). ) related to coating rolls used for coating. The conventional coating roll used for coating the cylindrical body of DI cans is as shown in Figure 1.
This is a roll A composed of a cylindrical metal base 1 and a rubber layer 2 with a smooth outer surface surrounding it.
3 is the rotation axis of roll A). The rubber material of the above rubber layer 2 is nitrile rubber or butyl rubber with a hardness range of 30° to 50° (measured by JIS K6301 spring type hardness tester A type), and the film thickness changes due to swelling by the paint solvent. A material with a swelling rate of 40% or less is used to prevent damage, and a material with good solvent resistance is used to prevent damage due to deterioration of physical properties. The thickness of the rubber layer is usually 20
~30mm. This coating roll uses a rubber material with a high hardness of 30° to 50°, so its outer circumferential surface can be easily formed into a cylindrical shape, and prevents uneven coating that occurs when the outer circumferential surface is non-cylindrical. There are advantages that can be achieved. However, due to its hardness, it is extremely unsuitable for painting not only the flat surface of the body but also protruding parts such as the peripheral annular protrusion of the can bottom. As shown in FIG. 2, in a DI can body B having a can body 41 and a can bottom 42, this protrusion is present at the periphery of the can bottom, surrounding the can bottom central dome portion 43 in an annular shape. If we look at the details, we can see that the outer inclined wall 44 and the inner inclined wall 4
5 and a small circular arc portion 46 connecting these two walls (Fig. 2a), the entire semicircular curve 4
7 (Fig. 2b), but in all cases, the height H of the protrusion is approximately 3 to 5 mm. On the other hand, the rubber layer of conventional coating rolls is hard and has a high degree of denting. This is because the coating of such protrusions requires a great deal of effort since there is little amount of paint. For example, to explain the painting of a protrusion with a curved surface structure as shown in Fig. 2b, as shown in Fig. 3,
Hang the DI can body B on the can body support part 31, apply a roll (not shown) to the protrusion of the can bottom periphery, and apply a pressing force within a range that does not deform the opening edge 48 of the can body (usually
7.5Kg/cm ² ) is used for pressure and rolling contact, but under such pressure the rubber layer of a conventional roll would normally only dent about 1.5 to 1.8 mm, so the height H would be 3 to 5 mm. It is not possible to paint the entire surface of the protruding part at once with one roll, so the only option is to divide the painting area into several parts and paint each part separately, as shown schematically in Figure 4, for example. . That is, the vicinity of the tip S of the protrusion is first
The second roll 22 coats the area T left uncoated by the main coating roll M that coated the outer surface of the body 41, and then coats the central dome 43 with the coating roll 21.
The side portions R are painted together when spray painting the central dome portion 43, which inevitably requires a lot of effort. In this case, it is easy to think of using a rubber material with low hardness and easy to dent as the rubber layer of the coating roll, but experiments have shown that it has a lower hardness than conventional rubber materials.
Even if you use a material with a hardness of 15°, which is much lower,
It can be seen that if the pressing force is applied to an extent that the can body opening edge 48 is not deformed, an unpainted area will be left on the protrusion, and if the pressing force is increased to prevent the unfilled area from being left unpainted, the edge 48 will be deformed. Ivy. Furthermore, it is also known that softer rubber materials with a hardness of less than 15° are affected by paint solvents and swell, resulting in deformation of the roll diameter and the softening agent of the rubber material leaching out, increasing the hardness. It was discovered that simply reducing the hardness of the rubber material did not solve the problem. The present invention provides a coating roll that can coat the entire surface of the annular protrusion around the bottom of a DI can body in one go, while retaining the advantages of conventional coating rolls (no uneven coating). Its feature is that the rubber layer surrounding the cylindrical metal base is made up of two layers: an inner sponge-like rubber layer and an outer rubber layer.Moreover, the inner sponge-like rubber layer has a swelling rate of 40% or less. , a rubber material (layer thickness of 10 to 50 mm) with a hardness of 5° or more and 10° or less (measured with JIS K6301 spring type hardness tester C type), and the outer layer of the rubber is
40% or less, and a hardness of 10° to 15° (measured using JIS K6301 spring type hardness tester A type). Here, "A type", "C type" in the hardness tester
Type A is distinguished by the shape of the tip of the indentation needle that comes into contact with the object to be measured. In Type A, the tip is a flat surface with a diameter of 0.79 mm and a conical shape that expands upward at an angle of 30 degrees. The C type has a hemispherical shape with a diameter of 5.08 mm. (The hardness of the sponge-like rubber inner layer cannot be measured with the A-type test material, so a C-type test material was used.) The roll of the present invention has an extremely soft sponge-like rubber inner layer, which is softer than conventional rubber layers. Since it has a rubber outer layer, its dentability is much larger than that of conventional rolls, so it is possible to completely coat the protruding parts.On the other hand, the hardness of the rubber outer layer (10
15°) allows the surface to be formed smoothly, making it possible to paint evenly as with conventional rolls. In addition, in the present invention, the reason why the layer thickness and hardness of the sponge-like rubber inner layer are set to the above values is that the thickness is 50 mm.
If the thickness exceeds mm or the hardness is less than 5°, it will be virtually impossible to form the surface of the coating roll into a cylindrical shape, and if the thickness is less than 10mm or the hardness exceeds 10°, the required This means that concavity cannot be obtained.
Similarly, if the thickness of the rubber outer layer exceeds 1 mm or the hardness exceeds 15°, the hardness of the rubber outer layer will increase due to the elution of the softener, and therefore, almost the entire recess formed by deformation will become a protrusion. It may not form a dent that can be adhered to, and there may be some remaining paint, and
If the thickness is less than 0.5 mm, it is virtually impossible to form a layer.
This is because if the hardness is less than 10°, the surface cannot be formed smoothly. In addition, the swelling rate of both rubber layers was set to 40
% or less in order to make the film thickness control as good as that of conventional coating rolls. With reference to FIG. 5, the coating agent applied to the annular protrusion on the periphery of the can bottom using the coating roll C of the present invention will be explained. This roll C consists of a cylindrical metal base 11, a spongy rubber inner layer 12 thereon, and an outer rubber layer 13 thereon (14 is a shaft). The specific contents of these rubber layers in this example are as follows.

[Table] The protruding parts to be painted are composed of full-surface curves (second
(see Figure b), and its height H was 5 mm. The roll C rotates in the X direction, and the can body B advances in the Y direction while pressing its can bottom 42 against the outer circumferential surface of the roll C at the same speed as the circumferential speed of the roll C, and the protruding portion is painted in the meantime. do. FIG. 6 shows the relationship between the pressing force applied to the roll of this example and the amount of depression at that time. As can be seen, the roll of this example shows a dent of 5.5 mm at a pressing force of 7.5 Kg/cm ² . Therefore, the protruding portion having a height H of 5 mm could be completely coated at once without any uneven coating under a pressing force that did not cause any deformation of the can opening edge 48. . Note that similar results were obtained when the protrusion included a non-curved surface as shown in FIG. 2a. As described above, according to the roll of the present invention, the annular protrusion around the bottom of the DI can can be coated in one operation without causing uneven coating. Furthermore, conventionally, as described above, only a portion of the central dome side portion of the protrusion (indicated by R in FIG. 4) is coated by the first coating roll 21, and most of the remaining portion is coated. was painted together with the dome portion 43 when it was spray-painted, so there was a risk that the atomized paint would go beyond the tip S of the protrusion, spread outward, and reach the body. Use of the roll of the present invention has the added benefit of avoiding such paint spreading, since spray coating can be confined to the dome area only.

[Brief explanation of the drawing]

Fig. 1 is a partial perspective view of a conventional coating roll, Fig. 2 is a partial sectional view showing an example of the form of an annular protrusion around the bottom of a DI can, and Fig. 3 is a DI suspended on a can support part. A cross-sectional side view of the can body, FIG. 4 is an explanatory diagram of the coating process of the protrusion using a conventional coating roll, and FIG. 5 is an explanatory diagram of the coating process of the protrusion carried out using the coating roll of the present invention. FIG. 6 is a diagram showing the relationship between the pressing force and the amount of dent in a roll example of the present invention. A: Example of a conventional coating roll, C: Example of a coating roll of the present invention, 11: Base, 12: Spongy rubber inner layer, 13: Rubber outer layer.

Claims (1)

[Scope of Claims] 1. A roll for applying an annular protrusion around the bottom of a DI can body, which comprises a cylindrical metal base, a spongy rubber inner layer surrounding the base, and a spongy rubber inner layer surrounding the spongy rubber layer. A coating roll comprising a rubber outer layer. 2. The coating roll according to item 1 above, wherein the sponge-like rubber inner layer has a swelling rate of 40% or less and a hardness of 5° or more and 10° or less (measured with JIS K6301 spring type hardness tester C type). Made of rubber material, the layer thickness is 10 to 50 mm, and the rubber outer layer has a swelling rate of 40%.
The following is a coating roll made of a rubber material with a hardness of 10° to 15° (measured using a JIS K6301 spring type hardness tester type A) and a layer thickness of 0.5 to 1.0 mm.