JP7584590B2 - Can body - Google Patents

Description

The present invention relates to a can body having a bottomed cylindrical can body centered on the can shaft, which includes a can bottom and a cylindrical can body portion that extends from the outer periphery of the can bottom to the upper end of the can axial direction and is centered on the can shaft.

As an example of such a can body and finished can, Patent Document 1 describes a can body (beverage can) that includes a cylindrical can body with a bottom and a can lid that is wrapped around the opening of the can body and has a planned drinking spout, where the can body includes a cylindrical can body that extends along the can axis, a can bottom that is provided on the lower end side of the can body in the axial direction, and a necking portion that is connected to the upper end side of the can body in the axial direction and that gradually reduces in diameter as it moves upward in the axial direction.

Here, in the can body and finished can described in Patent Document 1, the outer diameter of the can body is in the range of 55 mm to 60 mm, the axial height from the upper end of the seaming panel of the can lid to the lower end of the necking portion is in the range of 9 mm to 20 mm, and the difference between the outer diameter of the can body and the minimum outer diameter of the necking portion is in the range of 6 mm to 8 mm. In addition, the axial height of the can body is in the range of 120 mm to 190 mm.

Such can bodies are manufactured by first punching a metal plate into a disk shape in the cupping press process using a cupping press machine, and then forming a shallow cup-shaped material by drawing it. Next, this cup-shaped material is redrawn and ironed with a punch in the DI press process using a DI press machine, and is stretched in the axial direction of the can, forming the bottomed cylindrical can body described above.

In addition, it is known that such a can body has a constant outer diameter (diameter) of the can body, while the bottom side of the can body is a wall part with a thin wall thickness, and the part on the upper end opening side opposite the can bottom is a flange part that is thicker than the wall part. For example, Patent Document 2 describes a DI can body to be manufactured into a bottle can, in which the original thickness of the metal plate is 0.345 mm to 0.390 mm, but the difference in thickness between the flange part (flange thickness) and the wall part (wall thickness) is 0.110 mm or less.

To form wall and flange sections of different thicknesses in the can body, as described above, a recess with a depth that takes into account the difference in thickness (step) between the wall and flange sections is formed at a position corresponding to the flange section on the outer surface of the punch that performs the ironing process between the multiple ironing dies in the DI press.

JP 2016-005967 A JP 2018-131261 A

However, in recent years, there has been a strong demand for further thinning of the can body and lid in order to conserve resources from the metal materials that form such can bodies and product cans, and to conserve energy during material production. For example, in the case of aluminum alloy can bodies, there is a demand to manufacture the can body by forming a cup-shaped material by drawing from a plate of aluminum alloy with a plate thickness of about 0.230 mm to 0.300 mm.

However, particularly in such a thinned can body, the bottom side of the can body is a wall portion with a reduced thickness, as described above, and the portion on the top opening side opposite the can bottom is a flange portion that is thicker than the wall portion. If there is a large difference in thickness between the flange thickness and the wall thickness, the can body is likely to break during ironing between the punch and ironing die in the DI press molding machine, a phenomenon known as body breakage.

Once this type of can breakage occurs, the broken can body remains inside the DI press molding machine, and the molding operation using the DI press molding machine must be stopped temporarily to remove the broken can body. This inevitably leads to a significant drop in the productivity of the can body, and ultimately the productivity of finished cans.

The present invention was made against this background, and aims to provide a can body that can prevent the can from splitting even when the can body is thinned.

In order to solve the above problems and achieve the above object, the can body of the present invention has a bottomed cylindrical can body centered on the can axis, the can body includes a can bottom and a cylindrical can body centered on the can axis extending from the outer periphery of the can bottom to the upper end side in the can axial direction, the outer diameter of the can body is within a range of 55 mm to 60 mm in diameter, the can height from the bottom of the can bottom to the upper end opening of the can body is within a range of 150 mm to 190 mm, and the thickness of the can bottom on the can axis is 0.27 The thickness of the flange portion on the upper opening side of the can body is greater than the thickness of the wall portion on the can bottom side, the wall thickness measured at eight equally spaced points around the wall has a variation of ±7 μm, the flange thickness measured at eight equally spaced points around the flange has a variation of ±10 μm, and the can body step, which is the difference between the average flange thickness and the average wall thickness, is 60 μm or less.

In addition, in the above-mentioned can body, the can body is made of an aluminum alloy material, and the material strength is either 27k material, 26k material, or 25k material.

In addition, in the can body, the wall portion is formed within a range of 132.0 mm from the can bottom to the upper end in the can axial direction, and the flange portion is formed within a range of 15.4 mm from the upper end opening to the lower end in the can axial direction, and the can body step portion that serves as the can body step is formed within a range of 10.0 mm between the wall portion and the flange portion.

As explained above, according to the present invention, even in the case of a thin-walled can body, it is possible to prevent the occurrence of body breakage due to the step between the flange portion and the wall portion, and it is possible to prevent the molding operation by the DI press molding machine from being interrupted due to body breakage, thereby improving the productivity of the can body.

1 is a cross-sectional view taken along a can shaft, showing one embodiment of a can body of the present invention. FIG. 5 is an enlarged partial cross-sectional view showing the can bottom (part A in FIG. 1 ) of the product can of the embodiment shown in FIG. 1 and the embodiment shown in FIG. 4 . 2 is a partial cross-sectional view showing an outline of the can body of the embodiment shown in FIG. 1 (however, for the purpose of explanation, the thickness of the flange portion is exaggerated). 2 is a cross-sectional view taken along a can shaft, showing a state in which a shoulder portion, a neck portion, and a seam portion have been formed on the flange portion of the embodiment shown in FIG. 1. FIG. 5 is a side view showing an embodiment of a product can of the present invention in which a lid body is attached to the seam portion of the can body shown in FIG. 4. FIG. 6 is an enlarged cross-sectional view of a portion B in FIG. 5 showing the seaming portion of the embodiment shown in FIG. 5 .

Figures 1 to 3 show one embodiment of a can body of the present invention (however, Figure 2 is also common to one embodiment of a finished can of the present invention), and Figure 4 shows the state in which a shoulder portion, neck portion, and seam portion have been formed on the flange portion of the can body of this embodiment. Also, Figures 5 and 6 show one embodiment of a finished can of the present invention in which a lid body is seamed and attached to the seam portion of the can body shown in Figure 4.

The can body of this embodiment has a bottomed, cylindrical can body 1, as shown in FIG. 1, formed from a metal material such as aluminum or an aluminum alloy and centered on a can axis C. That is, this can body 1 is integrally formed with a roughly cylindrical can body 2 centered on the can axis C and a roughly disk-shaped can bottom 3 that closes the opening at the lower end side of this can body 2 (the lower side in FIGS. 1 to 3).

Among these, the can bottom 3 of the can body 1 has a dome section 4 formed in the center of the can bottom 3, which has a concave curved surface that is concave toward the upper end side in the can axis C direction (upper side in Figures 1 to 3), and on the outer periphery of this dome section 4, an annular protrusion 5 is formed continuously in the circumferential direction around the can axis C, protruding toward the lower end side in the can axis C direction and then toward the upper end side in the can axis C direction as it moves toward the radial outer periphery relative to the can axis C. Here, in this embodiment, the thickness t0 of the dome section 4 of the can bottom 3 of the can body 1 on the can axis C is within the range of 0.270 mm to 0.285 mm.

The inner wall of the annular protrusion 5 protruding from the dome portion 4 to the lower end in the direction of the can axis C is a counter portion 5a that extends in a linear incline toward the upper end in the direction of the can axis C as it approaches the inner periphery of the can body 1 in a cross section along the can axis C, as shown in FIG. 2. The counter angle θ that the counter portion 5a makes with respect to a straight line L parallel to the can axis C in the cross section along the can axis C is within the range of 4° to 7° in this embodiment.

On the other hand, the can body 2 has an outer diameter D that is a constant size within a range of 55 mm to 60 mm. Also, the can height H1 from the can bottom 5b of the annular protrusion 5 of the can bottom 3 (the position where the annular protrusion 5 protrudes furthest toward the lower end in the can axis C direction) to the upper end opening 2a of the can body 2 in the can axis C direction is a constant size within a range of 150 mm to 190 mm, and is 157.4 mm in this embodiment.

The can body 2 has a wall portion 2b on the side of the can bottom 3 and a flange portion 2c on the side of the upper end opening 2a. The wall thickness t1, which is the radial thickness of the wall portion 2b relative to the can axis C, is greater than the flange thickness t2, which is the radial thickness of the flange portion 2c relative to the can axis C, and a can body step portion 2d, which is a step in the can body 1, is formed between the wall portion 2b and the flange portion 2c.

Here, the wall portion 2b is formed within a range of 132.0 mm from the can bottom 5b to the upper end in the can axis C direction (106.0 mm from the boundary between the can body 2 and the can bottom 3 to the upper end in the can axis C direction), and the flange portion 2c is formed within a range of 15.4 mm from the upper end opening 2a to the lower end in the can axis C direction, and the can body step portion 2d is formed within a range of 10.0 mm between the wall portion 2b and the flange portion 2c.

The can body step t2-t1 between the flange thickness t2 of the flange portion 2c and the wall thickness t1 of the wall portion 2b is set to 60 μm or less. It is preferable that the can body step t2-t1 between the flange thickness t2 of the flange portion 2c and the wall thickness t1 of the wall portion 2b is set to 50 μm or more.

In this embodiment, the thickness is measured at eight equally spaced points in the circumferential direction at a height h1 that is 79 mm from the can bottom 5b toward the upper end in the can axis C direction, and the average value is the wall thickness t1. It is desirable that the variation in the wall thickness t1 at this time is ±7 μm. In this embodiment, the thickness is measured at eight equally spaced points in the circumferential direction at a height h2 from the can bottom 5b, which is 7 mm from the upper end opening 2a of the can body 2 toward the lower end in the can axis C direction, and the average value is the flange thickness t2. It is desirable that the variation in the flange thickness t2 at this time is ±10 μm.

The upper end opening 2a of the can body thus formed is trimmed as necessary to adjust it to the specified can height H1, and then, as shown in FIG. 4, the flange portion 2c is reduced in diameter in the necking process toward the upper end opening 2a to form a shoulder portion 6, and a cylindrical neck portion 7 is formed that is connected to the upper end of the shoulder portion 6 and is centered on the can axis C. Furthermore, the upper end opening 2a from the neck portion 7 is expanded in diameter in a curved shape in cross section along the can axis C toward the upper end in the direction of the can axis C, forming a seam portion 8 that is connected to the upper end of the neck portion 7.

The can thus formed is filled with the beverage or other contents, and then a lid 9 equipped with a pull tab (not shown) is wound and attached to the above-mentioned winding section 8 as shown in Figures 5 and 6, to produce one embodiment of the finished can (filled can) of the present invention. That is, this embodiment of the finished can also has a cylindrical finished can body 10 with a bottom centered on the can axis C, and the above-mentioned disk-shaped lid body 9 centered on the can axis C that is wound and attached to the upper opening of the finished can body 10.

This finished can body 10 also has a can bottom 3 similar to that of the can body 1 of the above-mentioned can body, and a generally cylindrical can body 2 centered on the can axis C, excluding a shoulder 6, neck 7, rolled seam 8, and lid 9, which extend from the outer periphery of the can bottom 3 toward the upper end in the direction of the can axis C. Here, the outer diameter of the can body 2 is within the range of 55 mm to 60 mm, the same as the can body 1, and the can height H2 of the finished can from the can bottom 5b of the can bottom 3 to the upper end 9a of the lid 9 is within the range of 150 mm to 190 mm, and in this embodiment is 155.6 mm, which is slightly lower than the can height H1 of the can body.

Here, the wall thickness t3 of the wall portion 2b in the product can body 10 of this product can is approximately equal to the wall thickness t1 of the can body 1. Meanwhile, by reducing the diameter of the flange portion 2c in the necking process to form the shoulder portion 6 and neck portion 7, the flange thickness t4 of the flange portion 2e in the shoulder portion 6 and neck portion 7 of the product can body 10 of this product can becomes thicker than the flange thickness t2 of the flange portion 2c in the can body 1 of the can body.

The product can step t4-t3 between the flange thickness t4 of the flange portion 2e and the wall thickness t3 of the wall portion 2b in this product can body 10 is 74 μm or less. It is preferable that the product can step t4-t3 between the flange thickness t4 of the flange portion 2e and the wall thickness t3 of the wall portion 2b in this product can body 10 be 60 μm or more.

Here, in the product can of this embodiment, the wall thickness t3 of the wall portion 2b is determined by measuring the thickness of the can body 2 at eight equally spaced points in the circumferential direction at a position at a height h1 of 79 mm from the can bottom 5b toward the upper end in the direction of the can axis C, as in the can body, and averaging the measurements to determine the wall thickness t3. It is desirable for the variation in the wall thickness t3 to be within ±7 μm.

In the finished can of this embodiment, the flange thickness t4 of the flange portion 2e is measured at eight equally spaced points around the circumference at a height h3 of 4 mm from the upper end 9a of the lid 9 toward the lower end in the direction of the can axis C, as shown in FIG. 6, and the average value is taken as the flange thickness t4. The position of this height h3 roughly corresponds to the position of the neck portion 7. It is desirable that the variation in the flange thickness t4 at this time be within ±10 μm.

Furthermore, in this finished can, the shape and dimensions of the can bottom 3 are almost the same as those of the can body. Therefore, in the finished can of this embodiment, the thickness t0 of the dome portion 4 of the can bottom 3 on the can axis C is in the range of 0.270 mm to 0.285 mm, and the counter angle θ that the counter portion 5a makes with respect to a line L parallel to the can axis C in a cross section along the can axis C is also in the range of 4° to 7°.

In the can body and product can thus constructed, the can body step t2-t1, which is the difference between the flange thickness t2 and the wall thickness t1 of the can body 1, is set to 60 μm or less, and the product can step t4-t3, which is the difference between the flange thickness t4 and the wall thickness t3 of the product can body 10, is set to 74 μm or less. In both cases, the flange thicknesses t2 and t4 are thicker than the wall thicknesses t1 and t3, but the can body step t2-t1 and the product can step t4-t3 are set small.

As a result, the step of the recess on the outer surface of the punch that performs the ironing process between the multiple ironing dies in the DI press machine can be made smaller, so that even when forming the can body 1 from a thin metal plate, it is possible to prevent the can body 1 from getting caught on this step and breaking, causing the can body 1 to break. Therefore, it is possible to prevent the molding operation by the DI press molding machine from being interrupted due to the can body breaking, which can improve the productivity of the can body and, ultimately, the productivity of the finished cans.

Here, if the can body step t2-t1, which is the difference between the flange thickness t2 and the wall thickness t1 of the can body 2 of the can body 1, exceeds 60 μm, the can body 1 is prone to breaking. Also, in a finished can, as described above, the flange thickness t4 becomes thicker as the flange portion 2c of the can body 1 of the can body is necked and the flange portion 2c is reduced in diameter, so if the finished can step t4-t3 is 74 μm or less, which is larger than the can body step t2-t1, it can be said that breaking is prevented in the DI press process by the DI press molding machine for the can body.

On the other hand, in such can bodies and finished cans, the punch and ironing die of the DI press molding machine form a dome section 4 in the shape of a concave curved surface recessed toward the upper end in the direction of the can axis C in the center of the can bottom section 3 of the can body 1 and the finished can body 10, as described above, and a ring-shaped protrusion 5 is formed continuously in the circumferential direction around the can axis C on the outer periphery of this dome section 4, which protrudes toward the lower end in the direction of the can axis C and then faces the upper end in the direction of the can axis C as it moves toward the radial outer periphery relative to the can axis C. Here, the shape and dimensions of this can bottom section 3 are almost the same between the can body 1 and the finished can body 10, as described above.

In the can body and product can of this embodiment, the inner wall portion of the annular protrusion 5 that protrudes from the dome portion 4 at the can bottom 3 toward the lower end in the direction of the can axis C is a counter portion 5a that extends linearly and inclined toward the upper end in the direction of the can axis C as it approaches the inner periphery of the can body 1 or the product can body 10 in a cross section along the can axis C, and the counter angle θ that this counter portion 5a makes with a straight line L parallel to the can axis C in the cross section is within the range of 4° to 7°.

Therefore, according to this embodiment, while ensuring the pressure resistance of the can bottom 3, it is possible to avoid the occurrence of cracks in the can bottom 3 during the DI press process, which would impair the productivity of the can body and the finished can. In other words, if the counter angle θ is greater than 7°, the counter portion 5a will be inclined at a large angle relative to the can axis C, which may impair the pressure resistance of the can bottom 3.

On the other hand, if the counter angle θ is less than 4°, the counter portion 5a becomes nearly parallel to the can axis C, and the portion of the punch and ironing die of the DI press molding machine that forms the counter portion 5a cuts vertically into the bottom surface of the cup-shaped material, which may cause cracks to form in the can bottom 3.

In addition, in this embodiment, the thickness t0 of the dome portion 4 of the can bottom 3 on the can axis C is within the range of 0.270 mm to 0.285 mm, and the thickness t0 of the dome portion 4 on the can axis C is approximately equal to the thickness of the metal plate formed into the can body, so the can body and product can can be formed from a thinner metal plate. Therefore, according to this embodiment, it is possible to conserve resources in the metal material that forms the can body and product can, and to conserve energy when manufacturing such materials.

Here, if the thickness t0 of the dome portion 4 on the can axis C is thin enough to be less than 0.270 mm, it may not be possible to ensure the necessary pressure resistance for the can body 1, and the pressure resistance of the product can body 10 may also be insufficient. On the other hand, if the thickness t0 of the dome portion 4 on the can axis C is thick enough to exceed 0.285 mm, the thickness of the metal plate formed into the can body and the product can may also become too thick, making it impossible to achieve sufficient resource and energy conservation.

Next, the effects of the present invention will be demonstrated by giving examples of the present invention. In these examples, one million can bodies 1 of seven types of can bodies were formed using a DI press molding machine from three types of metal plate made of aluminum alloy material with a plate thickness of 0.285 mm and material strengths of 27k, 26k, and 25k. The flange thickness t2 and wall thickness t1 were measured using the measurement method described above, and the can body step t2-t1 was calculated. These are shown in Table 1 as Examples 1 to 7, along with the counter angle. Note that the counter angle is different between Examples 1 to 3, Examples 4 to 6, and Example 7.

Then, shoulder 6 and neck 7 were formed on these can bodies by necking, seamed portion 8 was formed, and lid 9 was attached by seaming to produce product can body 10 of the product can. Similarly, flange thickness t4 and wall thickness t3 were measured using the measurement method described above, and product can step t4-t3 was calculated. Furthermore, drop pressure resistance and column strength of these product cans were calculated by simulation, and actual measurements were taken. The results are also shown in Table 1.

As a comparative example to Examples 1 to 7, one million cans each were made from three types of metal plate made of aluminum alloy material with a plate thickness of 0.285 mm and varying material strength in the same manner as in Examples 1 to 6, using a DI press molding machine to produce three types of can bodies. The flange thickness t2 and wall thickness t1 were similarly measured, and the can body step t2-t1 was calculated.

Furthermore, in these comparative examples, a lid 9 was attached to the molded can body to produce the product can body 10, and the flange thickness t4 and wall thickness t3 were measured to calculate the product can step t4-t3. In these comparative examples, the drop pressure resistance and column strength of the product can were also calculated by simulation, and actual values were measured. These results are also shown in Table 1 as Comparative Examples 1 to 3.

The percentages in the pressure resistance column are based on the result of Comparative Example 1 being 100%. In addition, in the examples and comparative examples, the flange thickness t4 and wall thickness t3 of the product can are thicker than the flange thickness t2 and wall thickness t1 of the can body, and this includes the thickness of the paint.

In this case, in the can bodies of Examples 1 to 7, only 5 out of 1 million cans suffered from body breaks when molded using a DI press molding machine. In contrast, in the can body of Comparative Example 1, 50 out of 1 million cans suffered from body breaks, and in the can body of Comparative Example 2, more than 500 out of 1 million cans suffered from body breaks, and even in the can body of Comparative Example 3, more than 500 out of 1 million cans suffered from body breaks. In addition, even in the product cans manufactured from the molded can bodies, the pressure resistance and column strength of Comparative Example 3 were smaller than those of Examples 1 to 7 and Comparative Examples 1 and 2. In Examples 1 to 6 and Comparative Examples 1 to 3, no cracks occurred in the can bottom 3.

Next, four types of can bodies having the same flange thickness t2, wall thickness t1, and can body step t2-t1 as in Examples 3, 6, and 7, but with different counter angles, were molded from a metal plate made of aluminum alloy material with a material strength of 25k and a thickness of 0.285 mm, as in Examples 3, 6, and 7, in the same numbers as in Examples 3, 6, and 7.

The can body thus formed was further subjected to necking to form a shoulder 6 and a neck 7, a seamed portion 8 was formed, and a lid 9 was attached by seaming to produce a product can body 10. For this product can body 10, the flange thickness t4 and wall thickness t3 were also measured, and the product can step t4-t3 was calculated. The drop pressure resistance and column strength of the product can were calculated by simulation, and actual measurements were also taken. The results are shown in Table 2 as Comparative Examples 11 to 14.

Of these Comparative Examples 11 to 14, in Comparative Examples 11 and 12, the counter angle was greater than 7° and the counter portion 5a was inclined at a large angle relative to the can axis C, so the pressure resistance was low in the simulation. In Comparative Examples 13 and 14, the product cans manufactured from the molded can bodies had sufficient pressure resistance and column strength, but because the counter angle was less than 4°, cracks occurred in the can bottom 3 in one can out of one million cans during molding of the can bodies using a DI press molding machine. Product cans with cracks in the can bottom 3 are defective products that are functionally defective, so even one can cannot be distributed on the market.

1 Can body 2 Can body 2a Upper end opening of can body 2 2b Can body and product can wall 2c Flange of can body 2d Can body step 2e Flange of product can 3 Can bottom 4 Dome 5 Annular convex 5a Counter 5b Can bottom 6 Shoulder 7 Neck 8 Seaming 9 Lid 9a Upper end of lid 9 10 Product can body C Can axis D Outer diameter of can body 2 H1 Can height of can body H2 Can height of product can h1 Height of 79 mm from can bottom 5b of can body and product can to upper end in the can axis C direction h2 Height of 150 mm from can bottom 5b of can body to upper end in the can axis C direction h3 Height of 4 mm from upper end 9a of lid 9 to lower end in the can axis C direction t0 Thickness of dome 4 of can bottom 3 on can axis C t1 Wall thickness at the can body t2 Flange thickness at the can body t3 Wall thickness at the product can t4 Flange thickness at the product can L Straight line parallel to the can axis C θ Counter angle

Claims (3)

The can has a cylindrical body with a bottom, the can body being centered on the can axis.
The can body includes a can bottom and a cylindrical can body extending from an outer periphery of the can bottom toward an upper end in the can axial direction and centered on the can axis,
A can body, wherein the outer diameter of the can body is within a range of 55 mm to 60 mm in diameter, and the can height from the bottom of the can bottom to the upper end opening of the can body is within a range of 150 mm to 190 mm,
The thickness of the can bottom on the can axis is within a range of 0.270 mm to 0.285 mm;
The can body has a flange portion on the upper opening side that is thicker than a wall portion on the can bottom side,
The wall thickness measured at eight equally spaced points in the circumferential direction of the wall portion has a variation of ±7 μm;
The flange thickness measured at eight equally spaced points in the circumferential direction of the flange portion has a variation of ±10 μm.
A can body characterized in that a can body step, which is a difference between the average flange thickness and the average wall thickness, is 60 μm or less. The can body according to claim 1, characterized in that the can body is made of an aluminum alloy material and has a material strength of 27K, 26K, or 25K. the wall portion is formed within a range of 132.0 mm from the can bottom to an upper end in the can axial direction,
the flange portion is formed within a range of 15.4 mm from the upper end opening toward a lower end in the can axial direction,
3. The can body according to claim 1, wherein a can body step portion serving as the can body step is formed within a range of 10.0 mm between the wall portion and the flange portion.

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