JP2021031181A - Can body - Google Patents

Abstract

To suppress buckling of a lid body while securing a constant withstanding pressure load on a can main body.SOLUTION: A can body comprises a bottomed cylindrical can main body 1 having a can axis in its center, and also has: a dome part 4 formed at a center part of a bottom part 3 of the can main body 1, the dome part being in a concave curved-surface shape concave toward a can-axially upper end side; an annular convex part 5 formed on an outer peripheral side of the dome part 4 continuously in a circumferential direction around the can axis, the annular convex part extending toward the can-axially upper end side while extending toward a radially outer peripheral side relative to the can axis after protruding toward the can-axially lower end; and a concave part 5b formed at an inner wall part 5a of the annular convex part 5 protruding from the dome part 4 toward the can-axially lower end side, the concave part being made concave toward the radially outer peripheral side relative to the can axis through bottom reformation processing. A bottom growth amount as an amount of protrusion deformation of a projection end 5d, protruding most toward the can-axially lower end side, of the annular convex part 5 toward the can-axially lower end side when internal pressure of 706 kPa is made to act on the inside of the can main body 1 in a no-load state is 1.0-2.0 mm.SELECTED DRAWING: Figure 2

Description

The present invention includes a bottomed cylindrical can body centered on a can shaft, and a can body such as an aluminum can in which the contents such as beverages are filled inside and the upper end opening is sealed by a lid. It is about.

In such a can body, a concave curved dome portion that is recessed toward the upper end side of the can body is formed in the central portion of the bottom portion of the can body, and the outer peripheral side of the dome portion has a diameter with respect to the can shaft. It is known that an annular convex portion toward the upper end side is continuously formed in the circumferential direction around the can axis after protruding toward the lower end side in the can axis direction toward the outer peripheral side.

Such a can body is filled with contents such as a carbonated water mixture of shochu (so-called shochu highball, abbreviated as chuhai) and a carbonated water mixture of whiskey (so-called highball), and then the upper end is opened. A lid with a pull tab on the part is wrapped and attached to seal it, and it is distributed on the market as a so-called two-piece can.

By the way, in recent years, there has been a strong demand for further thinning of the can body and lid in order to save resources and energy during material production of the metal material forming the can body, for example, made of aluminum alloy. In the case of the can body, it is also required to manufacture a can body by forming a cup-shaped material from a plate material made of an aluminum alloy having a plate thickness of about 0.230 mm to 0.300 mm by drawing.

However, in such a thin can body, the pressure resistance of the can body is significantly reduced, and if the content to be filled inside is like the above-mentioned carbonated drink, the can body is filled with the content. When internal pressure acts on the filled can that is sealed by the lid, a phenomenon called bottom growth occurs in which the tip of the annular convex portion at the bottom of the can body protrudes and deforms toward the lower end in the can axis direction, and the can is filled. There is a risk that the chute for transporting the can may be clogged, or a phenomenon called a buckling in which the dome portion protrudes toward the lower end side of the can body may occur.

Therefore, in order to suppress such bottom growth and buckling of the bottom of the can body, Patent Document 1 describes the annular convex portion in the can body in which the dome portion and the annular convex portion are formed on the bottom of the can body in this way. Of these, on the inner peripheral wall connected to the dome portion, a first concave curved surface portion having a curved shape that dents outward in the radial direction orthogonal to the can axis is formed by bottom reform processing in a vertical cross-sectional view along the can axis direction. At the same time, in the same vertical cross-sectional view, the dome part is connected to the dome top located on the can axis and the outside in the radial direction of the dome top, forming a concave curved surface having a smaller radius of curvature than the dome top. 2 The concave curved surface portion and the outer peripheral edge portion of the dome portion are arranged to connect the first concave curved surface portion and the second concave curved surface portion and form a linear shape in contact with the first concave curved surface portion and the second concave curved surface portion. Those in which a tapered portion is formed have been proposed.

Japanese Unexamined Patent Publication No. 2016-043991

In the can body described in Patent Document 1, the first and second concave curved surfaces connected to both ends of the tapered portion are formed so as to be bent. Specifically, in the vertical cross-sectional view of the can body. , The radius of curvature of the first and second concave curved surfaces connected to the linear tapered portion becomes smaller, and the degree of bending becomes steeper.

For this reason, stress can be easily concentrated on the first and second concave curved surfaces, so that a plurality of places where stress is concentrated can be stably secured, and the strength of the bottom of the can body is improved. Deformation is suppressed. Therefore, when the internal pressure of the can body rises, the stress is dispersed in the first and second concave curved surfaces, so that the pressure resistance strength of the can body is increased, so that the bottom growth and buckling of the bottom of the can body are increased. It can be suppressed.

However, when the bottom growth and buckling of the bottom of the can body are suppressed by increasing the pressure resistance of the can body in this way, the lid is also thinned for resource saving and energy saving. In the case of a can, when the internal pressure of the can body rises in the filled can as the pressure resistance of the lid decreases, the back of the lid projects so that the lid bulges toward the upper end side of the can body. Rings may occur.

The present invention has been made under such a background, and while ensuring a constant pressure-resistant load on the can body, it suppresses the occurrence of buckling of the lid when an internal pressure acts on the can body. The purpose is to provide a can body that can be used.

In order to achieve such an object by solving the above problems, the present invention is a can body provided with a bottomed cylindrical can body centered on a can shaft, which is provided on the bottom of the can body. Is formed with a concave curved dome portion recessed toward the upper end side in the can axis direction in the central portion, and on the outer peripheral side of the dome portion, after projecting toward the lower end side in the can axis direction, with respect to the can shaft. An annular convex portion toward the upper end side in the can axis direction is continuously formed in the circumferential direction around the can axis as it goes toward the outer peripheral side in the radial direction, and projects from the dome portion toward the lower end side in the can axis direction. The inner wall of the annular convex portion is formed with a concave portion recessed on the outer peripheral side in the radial direction with respect to the can shaft by bottom reform processing, and an internal pressure of 706 kPa is applied to the inside of the can body from a no-load state. The bottom growth amount, which is the amount of protrusion deformation of the tip of the annular convex portion toward the lower end side in the can axis direction, which is the amount of protrusion deformation toward the lower end side in the can axis direction, is within the range of 1.0 mm to 2.0 mm. It is characterized by being.

In the can body configured in this way, the lower end in the can axial direction of the tip of the annular convex portion protruding toward the lower end side in the can axial direction when an internal pressure of 706 kPa is applied to the inside of the can body from a no-load state. The amount of bottom growth, which is the amount of protrusion deformation to the side, is within the range of 1.0 mm to 2.0 mm, that is, within the range that does not cause clogging of the chute for transporting the filled can, the annular convex portion. Some bottom growth is allowed.

Therefore, even if the internal pressure acts on the sealed can body with the lid attached to the upper end opening, the internal pressure can be absorbed by the bottom growth of the annular convex portion at the bottom of the can body. Therefore, according to the can body having the above configuration, the internal pressure acting on the lid body can be reduced, so that it is possible to suppress the occurrence of buckling on the lid body.

Here, if the amount of bottom growth of the annular convex portion when an internal pressure of 706 kPa is applied to the inside of the can body is less than 1.0 mm, the buckling of the lid cannot be prevented. On the contrary, when the bottom growth amount of the annular convex portion when an internal pressure of 706 kPa is applied to the inside of the can body exceeds 2.0 mm, the filled can filled with the contents is conveyed. There is a risk of clogging of the chute.

It is desirable that the ratio of the increase in the amount of bottom growth to the increase in the internal pressure is stable because it is possible to avoid an unreasonable stress acting on the annular convex portion. Therefore, the amount of bottom growth at the tip of the annular convex portion when an internal pressure of 686 kPa is applied to the inside of the can body from a no-load state is within the range of 0.89 mm to 1.71 mm. The amount of bottom growth at the tip of the annular protrusion when an internal pressure of 618 kPa is applied to the inside of the can body from a no-load state is within the range of 0.55 mm to 1.29 mm. It is desirable that it is said.

That is, if the amount of bottom growth when an internal pressure of 686 kPa is applied and the amount of bottom growth when an internal pressure of 618 kPa is applied are smaller than the above range, the amount of bottom growth when an internal pressure of 706 kPa is applied is 1. In order to be within the range of 0.0 mm to 2.0 mm, the tip of the annular convex portion is rapidly projected and deformed, and stress is concentrated. Further, if the amount of bottom growth when an internal pressure of 686 kPa is applied or the amount of bottom growth when an internal pressure of 618 kPa is applied is larger than the above range, the annular convexity is reached from the no-load state to these internal pressures. The tip of the part is suddenly projected and deformed, which also causes stress concentration.

It is desirable that such a can body of the present invention is applied to a can body provided with a thinned can body for resource saving and energy saving as described above. Here, in the can body of such a can body, the thickness on the can shaft at the dome portion at the bottom of the can body is substantially equal to the thickness of the plate material (original plate thickness) before being formed into the can body.

Therefore, it is desirable that the thickness of the dome portion of the bottom of the can body on the can shaft is in the range of 0.270 mm to 0.290 mm. If the thickness of the dome portion on the can shaft is less than 0.270 mm, it may not be possible to secure the pressure resistance required for the can body, and conversely, if it exceeds 0.290 mm, sufficient resource saving may be achieved. And there is a risk that energy saving cannot be achieved.

Further, when the tip of the annular convex portion is formed in a convex arc shape in which the periphery of the tip is convex toward the lower end side in the can axis direction in a cross section along the can axis, the convex arc is formed. The radius inside the can body (punch R described later) is R (mm), the diameter of the circle formed by the tip around the can axis (ground diameter) is D (mm), and the concave portion is in the radial direction with respect to the can axis. The diameter of the circle (bottom reform inner diameter) formed by the bottom that is most recessed on the outer peripheral side around the can axis is d (mm), and the tip is closest to the can axis between this bottom and the tip of the annular convex portion. Bottom reform depth represented by the absolute value of (D-2 × (R + t) −d) / 2, where t (mm) is the wall thickness of the bottom of the can body in the radial direction with respect to the can axis at the protruding position. It is desirable that the diameter is in the range of 0.680 mm to 1.085 mm.

If the bottom reform depth exceeds 1.085 mm, the stretchability of the annular convex portion at the bottom of the can body is impaired, and the bottom growth amount is set within the range of 1.0 mm to 2.0 mm of 1.0 mm or more. You may not be able to do it. On the other hand, if the bottom reform depth is less than 0.680 mm, the pressure resistance strength at the annular convex portion may decrease.

As described above, according to the present invention, even if an internal pressure acts on the can body in a state where the lid is attached to the upper end opening of the can body and is sealed, the annular convex portion at the bottom of the can body is bottomed to some extent. By growing, it becomes possible to absorb the internal pressure, and even if the lid is thinned for resource saving and energy saving, it is possible to suppress the occurrence of buckling on the lid due to such internal pressure. it can.

It is sectional drawing along the can axis of the can body which shows one Embodiment of this invention. It is an enlarged sectional view of the bottom part of the can body of the embodiment shown in FIG. In the embodiment shown in FIG. 1, it is a cross-sectional view along the can axis when measuring the bottom growth amount of the can body before the necking process is applied to the upper end opening side. It is a figure which shows the relationship between the internal pressure of the can body and the amount of bottom growth in the embodiment shown in FIG.

1 and 2 show an embodiment of the present invention, and FIG. 3 shows a state in which the bottom growth amount of the can body before the necking process is applied to the upper end opening side is measured in this embodiment. Is shown. Further, FIG. 4 is a diagram showing the relationship between the internal pressure of the can body and the amount of bottom growth in the embodiment shown in FIG.

The can body of the present embodiment includes a bottomed cylindrical can body 1 centered on a can shaft C as shown in FIG. 1 formed of a metal material such as aluminum or an aluminum alloy. That is, the can body 1 has a substantially cylindrical body portion 2 centered on the can shaft C and an opening on the lower end side (lower side in FIGS. 1 and 2; upper side in FIG. 3) of the body portion 2. It is configured by being integrally formed with a substantially disk-shaped bottom portion 3 that closes the bottom portion 3.

The bottom 3 of the can body 1 has a concave curved dome recessed in the center of the bottom 3 toward the upper end side (lower side in FIGS. 1 and 2; upper side in FIG. 3) in the can axis C direction. Along with the formation of the portion 4, the outer peripheral side of the dome portion 4 protrudes toward the lower end side in the can shaft C direction, and then an annular shape toward the upper end side in the can shaft C direction toward the radial outer peripheral side with respect to the can shaft C. The convex portion 5 is continuously formed in the circumferential direction around the can axis C. Here, in the present embodiment, the thickness of the dome portion 4 of the bottom portion 3 of the can body 1 on the can shaft C is in the range of 0.270 mm to 0.290 mm.

The bottom portion 3 of the inner wall portion 5a facing the can shaft C side of the annular convex portion 5 is subjected to bottom reform processing, so that the cross section along the can shaft C is shown in FIG. In addition, a concave portion 5b recessed in a concave curved shape is formed on the outer peripheral side in the radial direction with respect to the can shaft C. Further, the protruding end portion (lower end portion) 5c of the annular convex portion 5 has a protruding end portion 5d in which the protruding end portion 5c protrudes most toward the lower end side in the can axis C direction, as shown in FIG. It is formed in a convex arc shape that is convex toward the lower end side in the can axis C direction around the can axis.

Here, the inner wall portion 5a of the annular convex portion 5 facing the can shaft C side is subjected to bottom reform processing, whereby the inner wall portion 5a is radially oriented from the dome portion 4 to the recess 5b with respect to the can shaft C. After denting on the outer peripheral side, the tip portion 5c protrudes in a radial inner peripheral side with respect to the can shaft C in a convex curve shape in cross section to reach the tip 5d of the tip portion 5c having a convex arc shape in cross section. Further, the annular convex portion 5 extends from the protruding end 5d toward the outer peripheral side in the radial direction with respect to the can shaft C while being inclined toward the upper end side in the can shaft C direction, and is connected to the lower end of the body portion 2.

Furthermore, from the position where the inner wall portion 5a of the annular convex portion 5 protrudes most to the radial inner peripheral side with respect to the can shaft C, the concave portion 5b formed by the bottom reforming process is moved to the radial outer peripheral side with respect to the can shaft C. The recessed amount to the most recessed bottom 5e, that is, the bottom reform depth e, has a radius of R (mm) inside the can body 1 of the convex arc formed by the periphery of the tip 5d of the annular convex portion 5 in the cross section along the can axis C. ), The diameter of the circle formed by the tip 5d around the can shaft C (ground diameter) is D (mm), and the diameter of the circle formed by the bottom 5e of the recess 5b around the can shaft C (bottom reform inner diameter) is d (mm). ), The thickness of the bottom portion 3 of the can body 1 in the radial direction with respect to the can shaft C at the position where the tip portion 5c protrudes most toward the can shaft C side from the portion of the bottom 5e to the tip end 5d of the annular convex portion 5. When t (mm), it is represented by an absolute value of (D-2 × (R + t) −d) / 2. The bottom reform depth e is in the range of 0.680 mm to 1.085 mm in the present embodiment.

Then, the bottom portion 3 of the can body 1 is formed so that when an internal pressure is applied to the inside of the can body 1, the annular convex portion 5 is deformed so as to protrude toward the lower end side in the can axis C direction to cause bottom growth. When an internal pressure of 706 kPa is applied to the inside of the can body 1 from a no-load state, the amount of bottom growth, which is the amount of protrusion deformation of the protruding end 5d of the annular convex portion 5 toward the lower end side in the can axis C direction, is increased. It is set to be within the range of 1.0 mm to 2.0 mm.

Further, in the present embodiment, the bottom growth amount of the tip 5d of the annular convex portion 5 when an internal pressure of 686 kPa is applied to the inside of the can body 1 from a no-load state is within the range of 0.89 mm to 1.71 mm. It is designed to be. Further, in the present embodiment, the bottom growth amount of the tip 5d of the annular convex portion 5 when an internal pressure of 618 kPa is applied to the inside of the can body 1 from a no-load state is within the range of 0.55 mm to 1.29. It is designed to be.

In the present embodiment, the body 2 of the can body 1 has a thin wall portion 2a on the lower end side connected to the outer peripheral portion of the bottom portion 3, and the upper end side portion is the wall portion 2a. The flange portion 2b is thicker than the wall thickness. Further, as shown in FIG. 1, the upper end portion of the thick flange portion 2b is formed with a shoulder portion 2c so as to gradually reduce the diameter toward the upper end side, and further, the shoulder portion 2c is the maximum. At the upper end, a lid attachment portion 2d to which a lid with a pull tab (not shown) is wound and attached is formed so as to project on the outer peripheral side in the radial direction with respect to the can shaft C.

The can body 1 of such a can body is manufactured by first forming a shallow cup-shaped material by punching a metal plate into a disk shape and drawing it in a cupping press process using a cupping press machine. .. In the present embodiment, the metal plate formed into the cup-shaped material in this cupping press step has a base plate thickness of 0.270 mm to 0, which is substantially equal to the thickness on the can shaft C of the dome portion 4 of the bottom portion 3 of the can body 1. a A3004 or aluminum alloy plate A3104 in the in the aluminum plate or JIS H 19 which is the range of .290mm, 0.2% proof stress after 205 ° C. × 20 minutes baking of 255N ^/ mm ² ~295N ^/ mm 2 scope of what is used, more preferably in the range of 265N ^/ mm ² ~284N ^/ mm 2 is used.

Next, the cup-shaped material is re-squeezed and ironed by a punch in a DI pressing process using a DI press machine and stretched in the can shaft C direction, so that the outer peripheral portion is a cylindrical portion 12 centered on the can shaft C. The bottom portion 3 is formed with a dome portion 4 and an annular convex portion 5 similar to those of the can body 1, and a bottomed cylindrical body 11 as shown in FIG. 3 is formed.

The thickness of the bottomed cylinder 11 and the dome portion 4 of the bottom portion 3 of the can body 1 on the can shaft C is substantially equal to the original plate thickness of the metal plate formed into the cup-shaped material in the cupping press step. The radius R (mm) inside the can body 1 of the convex arc formed by the periphery of the tip 5d of the annular convex portion 5 in the cross section along the can axis C is the convex arc formed by the tip of the punch in the cross section along the can axis C. Approximately equal to the radius (punch R).

Further, the cylindrical portion 12 of the bottomed cylindrical body 11 has a constant outer diameter whose outer diameter (diameter) is substantially equal to the outer diameter of the body portion 2 of the can body 1. Further, the portion of the cylindrical portion 12 on the bottom 3 side is a wall portion 13 which is a thin portion having a thin wall thickness as described above, and the upper end side opposite to the bottom portion 3 (lower side in FIG. 3). The portion of is a flange portion 14 which is thicker than the wall portion 13 as described above.

Here, in order to form the wall portion 13 and the flange portion 14 having different thicknesses on the cylindrical portion 12, the punch that irons the wall portion 13 and the flange portion 14 with the plurality of ironing dies in the DI press machine as described above is used. A recess having a depth considering the difference in wall thickness may be formed at a position corresponding to the flange portion 14 on the outer surface. Further, the inner wall portion 5a of the bottom portion 3 of the can body 1 is subjected to bottom reform processing to form the recess 5b as described above.

The bottomed cylindrical body 11 formed in this way is washed and dried in the first washing step after the upper end edge of the cylindrical portion 12 is cut by a predetermined trimming allowance and the heights are made uniform in the trimming step by the trimmer. Then, in the painting process, the inner and outer surfaces are painted and baked. Further, in the bottomed cylindrical body 11 that has been painted, in the bottleneck forming process by the bottle necker, the range of the flange portion 14 of the cylindrical portion 12 is reduced in diameter to form the shoulder portion 2c, and the shoulder portion 2c is expanded. In the process, the lid attachment portion 2d is formed, and after the contents such as a carbonated drink are filled, the lid is wound and attached.

In the can body having the above structure formed and manufactured in this manner, the most can of the annular convex portion 5 when an internal pressure of 706 kPa is applied to the inside of the can body 1 from a no-load state as described above. As shown in FIG. 4, the bottom growth amount, which is the amount of protrusion deformation of the protruding end 5d protruding toward the lower end side in the shaft C direction toward the lower end side in the can shaft C direction, is within the range of 1.0 mm to 2.0 mm. That is, a certain amount of bottom growth is allowed in the annular convex portion 5 as long as the chute for transporting the filled can filled with the contents is not clogged.

Therefore, even if the lid is attached to the lid attachment portion 2d of the upper end opening of the can body 1 and an internal pressure acts on the sealed can body 1, the annular convex portion 5 of the bottom 3 of the can body 1 is the bottom. By growing, this internal pressure can be absorbed, so that the internal pressure acting on the lid can be reduced. Therefore, according to the can body having the above configuration, it is possible to suppress the occurrence of buckling on the lid body due to such internal pressure.

Here, in order to measure the amount of bottom growth of the annular convex portion 5 on the bottom portion 3 of the can body 1, the upper end opening of the bottomed cylindrical body 11 is airtight with the bottom portion 3 facing upward as shown in FIG. The bottom growth amount (protruding deformation amount) of the tip 5d at the annular convex portion 5 of the bottom portion 3 may be measured by the displacement meter 21 while the internal pressure is increased to 706 kPa by supplying compressed air or the like to the inside. The bottom of the bottomed cylindrical body 11 may be turned downward or sideways, or the bottom growth amount of the tip 5d may be measured in the can body 1 in which the shoulder portion 2c and the lid mounting portion 2d are formed. Good.

Here, if the amount of bottom growth of the annular convex portion 5 when an internal pressure of 706 kPa is applied to the inside of the can body 1 is less than 1.0 mm, the absorption of the internal pressure by the can body 1 becomes insufficient, so that the lid body Buckling cannot be prevented. On the contrary, when the bottom growth amount of the annular convex portion 5 when an internal pressure of 706 kPa is applied to the inside of the can body 1 exceeds 2.0 mm, the can body 1 is filled with the contents and the lid. The chute for transporting the filled can with the body attached may be clogged. 706 kPa is a guaranteed pressure resistance value of a 206-caliber can body as shown in FIG.

Further, in the present embodiment, the bottom growth amount of the annular convex portion 5 when an internal pressure of 686 kPa is applied to the inside of the can body 1 from a no-load state is within the range of 0.89 mm to 1.71 mm. In addition, the bottom growth amount of the annular convex portion 5 when an internal pressure of 618 kPa is applied to the inside of the can body 1 from a no-load state is within the range of 0.55 mm to 1.29 mm, and the internal pressure is set. Since the ratio of the increase in the amount of bottom growth to the increase in the amount is stable, it is possible to avoid an unreasonable stress acting on the annular convex portion 5.

That is, if the amount of bottom growth when an internal pressure of 686 kPa is applied and the amount of bottom growth when an internal pressure of 618 kPa is applied are smaller than the above range, the amount of bottom growth when an internal pressure of 706 kPa is applied is 1. In order to be within the range of 0.0 mm to 2.0 mm, the tip 5d of the annular convex portion 5 is suddenly projected and deformed, and the stress is concentrated. Further, if the amount of bottom growth when an internal pressure of 686 kPa is applied or the amount of bottom growth when an internal pressure of 618 kPa is applied is larger than the above range, the annular convexity is reached from the no-load state to these internal pressures. Since the tip 5d of the portion 5 is suddenly projected and deformed, stress concentration is also caused.

Further, in the can body of the above embodiment, the thickness of the dome portion 4 of the bottom portion 3 of the can body 1 on the can shaft C is in the range of 0.270 mm to 0.290 mm. In the can body 1 of such a can body, the thickness of the dome portion 4 of the bottom portion 3 of the can body 1 on the can shaft C becomes substantially equal to the thickness of the plate material before being formed into the can body 1. In the can body 1 formed from such a thin plate material, the can body 1 is formed by suppressing the buckling of the lid by controlling the bottom growth amount of the annular convex portion 5 as described above. It is effective for saving resources and energy of metal materials.

Further, in the present embodiment, the protruding end portion 5c of the annular convex portion 5 is formed in a convex arc shape in which the periphery of the protruding end 5d is convex toward the lower end side in the can axis C direction in a cross section along the can axis C. The radius (punch R) inside the can body 1 of this convex arc is R (mm), the diameter of the circle (ground contact diameter) formed by the tip 5d around the can axis C is D (mm), and the annular convex portion is formed by bottom reforming. The diameter of the circle (bottom reform inner diameter) formed by the bottom 5e, which is the most concave on the outer peripheral side in the radial direction of the recess 5b formed in the inner wall portion 5a of 5, around the can shaft C, is d (mm), and this bottom. The wall thickness of the bottom portion 3 of the can body 1 in the radial direction with respect to the can shaft C at the position where the tip portion 5c protrudes most toward the can shaft C side from the portion 5e to the protrusion 5d of the annular convex portion 5 is t (mm). The bottom reform depth e represented by the absolute value of (D-2 × (R + t) −d) / 2 is within the range of 0.680 mm to 1.085 mm.

Therefore, the buckling of the lid is suppressed by surely setting the bottom growth amount within the range of 1.0 mm to 2.0 mm of 1.0 mm or more without impairing the buckling strength and the pressure resistance strength of the annular convex portion 5. Can be done. That is, when the bottom reform depth e exceeds 1.085 mm, the stretchability of the annular convex portion 5 at the bottom 3 of the can body 1 is impaired, and the bottom growth amount is 1.0 mm to 2. On the other hand, if the bottom reform depth e is less than 0.680 mm, the pressure resistance strength at the annular convex portion 5 may be impaired.

Next, the effect of the present invention will be described with reference to examples of the present invention. In this embodiment, the can height H1 from the tip 5d to the upper end opening of the lid mounting portion 2d at the annular convex portion 5 of the bottom 3 of the can body 1 as shown in FIG. 1 is 122.2 mm, and the tip 5d. The height H2 from the lower end of the shoulder 2c to the lower end is 102.2 mm, the height H3 to the upper end of the shoulder 2c is 118 mm, the inner diameter A of the body 2 is 66.3 mm, and the inner diameter B of the lid mounting portion 2d is 57. .3 mm, the amount E of the lid mounting portion 2d extending to the outer peripheral side in the radial direction with respect to the can shaft C is 2.25 mm, and the radius r in the cross section of the portion where the lid mounting portion 2d overhangs along the can shaft C is 1. A can body having a diameter of a circle (ground contact diameter) D of 8.8 mm and a tip 5d forming around the can shaft C was formed from an aluminum alloy material having a base plate thickness of 0.285 mm.

In this embodiment, the inner wall portion 5a of the annular convex portion 5 in the bottom portion 3 of the can body 1 is subjected to bottom reform processing so that concave portions 5b of different sizes are formed, and the concave portion 5b is subjected to bottom reform processing with respect to the can shaft C of the concave portion 5b. Six types of cans with different diameters (bottom reform inner diameter) d and bottom reform depth e of the circle formed by the bottom 5e, which is the most concave on the outer peripheral side in the radial direction, around the can axis C, are manufactured for each 100 cans, as shown in FIG. The amount of bottom growth was measured by the measuring method as shown. These are referred to as Examples 1 to 6.

In Examples 1 to 6, the thickness (wall thickness) of the wall portion 2a of the body portion 2 is 0.101 mm, the thickness of the flange portion 2b (flange thickness) is 0.161 mm, and that of the can body 1. The mass is 11.7 g, and the radius inside the can body 1 of the convex arc formed by the periphery of the tip 5d of the tip 5c in the cross section along the can axis C is 1.2 mm, which is equal to the tip radius (punch R) of the punch. Met.

In Examples 1 to 6, after filling the inside of such a can body with the contents, the lid body is attached to manufacture a filled can, and the buckling of the lid body is subjected to a retention test at 60 ° C. for 10 to 40 minutes. In addition to confirming the presence or absence of the can, it was confirmed that the chute for transporting the filled can was clogged. The content was a carbonated water split (highball) of whiskey with a gas volume (GV) of 3.0, and the pressure resistance strength of the lid was 740 kPa. The specifications of Examples 1 to 3 are shown in Table 1 together with the pressure resistance strength, buckling strength, bottom growth amount, and pressure resistance strength of the lid body of the can body 1.

Further, as a comparative example with respect to Examples 1 to 6, 100 cans having an external size substantially equal to that of Examples 1 to 6 are molded from an aluminum alloy having a base plate thickness of 0.285 mm, which is the same as that of Examples 1 to 6. The amount of bottom growth was measured. This is referred to as Comparative Example 1. However, the bottom reform inner diameter d and the bottom reform depth e of Comparative Example 1 are larger than those of Examples 1 to 6.

Further, 100 cans having substantially the same external dimensions as those of Examples 1 to 6 and Comparative Example 1 are formed from an aluminum alloy having a base plate thickness of 0.335 mm, which is thicker than that of Examples 1 to 6 and Comparative Example 1, and bottom growth is performed. The amount was measured. This is referred to as Comparative Example 2. However, this Comparative Example 2 is not subjected to bottom reform processing.

Furthermore, 100 cans having a size substantially equal to that of Examples 1 to 6 were formed from an aluminum alloy having a base plate thickness of 0.285 mm, which is the same as that of Examples 1 to 6 and Comparative Example 1, and the amount of bottom growth was measured. .. This is referred to as Comparative Example 3. However, even in this Comparative Example 3, the bottom reform process is not performed.

Then, also in these Comparative Examples 1 to 3, the same contents as in Examples 1 to 6 are filled and the lid is attached to manufacture a filled can, and the presence / absence and contents of the buckling of the lid are made under the same conditions. It was confirmed that the chute carrying the filled can filled with the material was clogged. The specifications of these Comparative Examples 1 to 3 are also shown in Table 1 together with the pressure resistance strength of the can body, the buckling strength, the amount of bottom growth, and the pressure resistance strength of the lid. The specifications and the like shown in Table 1 are the average values of 100 cans and filled cans in both Examples 1 to 6 and Comparative Examples 1 to 3.

In Table 1, the bottom growth amount when an internal pressure of 706 kPa is applied to the can body 1 is within the range of 1.0 mm to 2.0 mm, and the bottom growth amount when an internal pressure of 686 kPa is applied is set. In the cans of Examples 1 to 6, the bottom growth amount was in the range of 0.89 mm to 1.71 mm and the bottom growth amount when an internal pressure of 618 kPa was applied was in the range of 0.55 mm to 1.29 mm. Even if the original plate thickness is as thin as 0.285 mm, none of the filled cans manufactured from 100 cans have a backing on the lid, and the filled cans are filled with the contents. There was no clogging in the chute that carried the.

On the other hand, in Comparative Example 1 in which the amount of bottom growth was 0.92 mm, which was smaller than 1.0 mm, buckling of the lid was observed in 10 of the 100 cans. Further, in Comparative Example 2 in which the original plate thickness was as thick as 0.335 mm, the buckling of the lid was not observed, but the mass of the can body was 13.3 g, which was 1 g or more heavier than that of Example 1, and was molded into the can body. It is not possible to save resources or energy for the metal materials (aluminum alloy materials) that are used. In Comparative Examples 1 and 2, there was no clogging in the shoot.

On the other hand, in Comparative Example 3, although the buckling of the lid was not observed, the bottom growth amount was as large as 3 mm or more, so that the chute was filled with the contents and conveyed the filled can with the lid attached. Occurrence of clogging occurred frequently.

1 Can body 2 Body 2a, 13 Wall 2b, 14 Flange 2c Shoulder 2d Lid mounting 3 Bottom 4 Dome 5 Circular convex 5a Inner wall 5b Recess 5c Protrusion 5d Projection 5e Recess 5b Can shaft C The bottom that is most recessed on the outer peripheral side in the radial direction with respect to the base 11 Bottomed cylinder 12 Cylindrical part 21 Displacement meter C Can shaft D The diameter of the circle formed by the tip 5d of the tip 5c around the can shaft C (ground contact diameter)
R The radius (punch R) inside the can body 1 of the convex arc formed around the tip 5d of the tip 5c in the cross section along the can shaft C.
d Diameter of the circle formed by the bottom 5e of the recess 5b around the can shaft C (bottom reform inner diameter)
t The thickness of the bottom 3 of the can body 1 in the radial direction with respect to the can shaft C at the position where the protrusion 5c protrudes most toward the can shaft C from the portion of the bottom 5e of the recess 5b to the protrusion 5d of the annular convex portion 5. e Bottom reform depth

Claims (5)

It is a can body equipped with a bottomed cylindrical can body centered on the can shaft.
At the bottom of the can body, a concave curved dome portion is formed in the center portion, which is recessed toward the upper end side in the can axis direction, and on the outer peripheral side of the dome portion, the dome portion projects toward the lower end side in the can axis direction. After that, the annular convex portion toward the upper end side in the can axis direction is continuously formed in the circumferential direction around the can axis as it goes toward the outer peripheral side in the radial direction with respect to the can axis.
The inner wall portion of the annular convex portion protruding from the dome portion toward the lower end side in the can axis direction is formed with a concave portion recessed on the outer peripheral side in the radial direction with respect to the can axis by bottom reform processing.
The bottom growth amount, which is the amount of protrusion deformation of the tip of the annular convex portion toward the lower end side in the can axial direction when an internal pressure of 706 kPa is applied to the inside of the can body from a no-load state, is 1.0 mm or more. A can body characterized in that it is within the range of 2.0 mm. The bottom growth amount of the tip of the annular convex portion when an internal pressure of 686 kPa is applied to the inside of the can body from a no-load state is within the range of 0.89 mm to 1.71 mm. The can body according to claim 1. The bottom growth amount of the tip of the annular convex portion when an internal pressure of 618 kPa is applied to the inside of the can body from a no-load state is within the range of 0.55 mm to 1.29 mm. The can body according to claim 1 or 2. Any one of claims 1 to 3, wherein the thickness of the dome portion of the bottom of the can body on the can shaft is in the range of 0.270 mm to 0.290 mm. The can body described in the section. The tip portion of the annular convex portion is formed in a convex arc shape in which the periphery of the tip is convex toward the lower end side in the can axis direction in a cross section along the can axis.
The radius of the convex arc inside the can body is R (mm), the diameter of the circle formed by the tip around the can axis is D (mm), and the recess is most recessed on the outer peripheral side in the radial direction with respect to the can axis. The diameter of the circle formed by the bottom around the can axis is d (mm), and the can in the radial direction with respect to the can axis at the position where the tip portion protrudes most toward the can axis between the bottom portion and the tip of the annular convex portion. When the wall thickness of the bottom of the main body is t (mm), the bottom reform depth represented by the absolute value of (D-2 × (R + t) −d) / 2 is 0.680 mm to 1.085 mm. The can body according to any one of claims 1 to 4, wherein the can body is within the range.

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