JP6760460B1 - Manufacturing method of seamless can body and seamless can body - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a seamless can body which is less likely to be distorted near the lower end of a can body and can realize uniform mapping in the axial direction, and a method for manufacturing the same. SOLUTION: A seamless can body of the present invention has a tubular body portion and a can bottom portion provided with at least a continuous outer peripheral bottom portion so as to reduce the diameter inward from the lower end of the tubular body portion via a boundary portion. It is characterized in that the plate thickness of the lower end of the tubular body portion is substantially equal to the plate thickness of the intermediate portion in the axial direction of the tubular body portion. [Selection diagram] Fig. 1

Description

The present invention relates to a seamless can body and a method for manufacturing a seamless can body.

Conventionally, a so-called seamless can body in which a can body and the like are formed by squeezing and ironing is known. This seamless can body is excellent in light weight because the can body is thinned by ironing after shallow drawing. On the other hand, in these seamless cans, various proposals have been made in order to maintain or improve the pressure resistance even if the thickness is reduced.

For example, Patent Document 1 and Patent Document 2 disclose so-called bottom reform processing, which is performed for the purpose of preventing a phenomenon (buckling) in which the dome portion of the can bottom is inverted, which appears when the internal pressure of the can exceeds the pressure resistance strength. Has been done. Specifically, a bottom reforming process for forming a concave portion by pressing an inner peripheral wall of a ground contact portion of the can bottom located inside in the radial direction orthogonal to the can axis is disclosed.

Japanese Unexamined Patent Publication No. 2018-10322 Japanese Unexamined Patent Publication No. 2016-47541 Japanese Unexamined Patent Publication No. 2016-43991

As described above, although the conventional seamless can body is excellent in light weight, there are still points to be improved in the can body portion which is a side surface thereof. That is, in recent years, various designs have been applied to the can body to ensure product competitiveness, and from this point of view, as uniform mapping as possible is required for the can body.

However, in the conventional method for manufacturing a seamless can body, the surface state of the can body portion after molding is not aligned along the axial direction, and particularly exists near the lower end of the can body portion or between the can body portion and the can bottom portion. It was not possible to obtain a high metallic luster in the reduced diameter portion (bottom of the outer periphery).
This point will be described in detail with reference to FIG.

FIG. 10A schematically shows a partial state of the can body and the tip of the ironing punch immediately after the ironing process is completed. As shown in the figure, a tapered shape is provided from point A to point B near the tip of the cylindrical portion of the punch. This taper shape is provided so that the ironing rate is gradually increased when the ironing process is started. Therefore, the can body portion corresponding to this tapered portion is a region having a wedge-shaped plate thickness distribution. As shown in FIG. 2 and the like, this region may also be referred to as "body wall step (BWS)". Further, on the lower side of the BWS, a portion also called a body wall radius (BWR) is formed, which has a relatively large diameter reduction toward the inside of the can.

When the above-mentioned ironing process is performed, the glossiness of the ironed surface is almost the same glossiness as the original material surface at the point B located at the lower end of the above-mentioned BWS, and the point located at the upper end of the above-mentioned BWS. The glossiness increases as it approaches A, and the maximum glossiness is exhibited after the point A.
FIG. 10B shows a partial portion of the can body and the tip of the ironing punch at the time when the dome portion is formed on the bottom of the can by relatively immersing the doming die inside the tip of the ironing punch after the ironing process is completed. It is a figure which shows the state. The bottom surface of the can bottom is pulled in as a dome portion, so that the portion located at the point A in FIG. 10 (a) is located at the point A', and the portion located at the point B is located at the point B'. It will shift. The amount of movement (deviation amount) of each of these points is, for example, about 2 to 5 mm. In this way, there is still a part of the can body near the bottom of the cylindrical part where the glossiness is low and the print quality is inferior, but the design property has a higher metallic luster in this part than before. There was also a demand for a seamless can body with a high quality.
Although it is possible to increase the amount of deviation by simply increasing the amount of immersion of the doming die, the content of the can to be molded is significantly reduced, and at the same time, the amount of material used in the can is increased. Such issues remain.

As a result of repeated diligent studies in view of the above-exemplified problems, the present inventor has determined to provide a seamless can body capable of imparting excellent image quality to the can body portion after squeezing and ironing, and a method for producing the same. This has made it possible and led to the present invention.
Further, it has become possible to provide a seamless can body having a high metallic luster and a method for manufacturing the same in a reduced diameter portion (outer peripheral bottom portion) existing between the can body portion and the can bottom portion, which has led to the present invention. is there.

The seamless can body according to the embodiment of the present invention has (1) a can bottom portion having at least a tubular body portion and a continuous outer peripheral bottom portion such that the diameter is reduced inward from the lower end of the tubular body portion via a boundary portion. When, wherein the thickness of the lower end of the tube-shaped body portion, the plate thickness at the boundary portion, and at least part of the thickness of the outer peripheral bottom, the intermediate portion in the axial direction of each of the tube-shaped body portion It is characterized in that it is almost equal to the plate thickness.

Further, in the seamless can body described in (1) above, ( 2 ) the plate thickness at the lower end of the tubular body is t _WL, and the plate thickness of the intermediate portion in the axial direction of the tubular body is t _WC. In this case, it is preferable that the relationship is t _WC ≤ t _WL <1.09 × t _WC .

In the seamless can body according to the above (2), (3) in the cylindrical body _portion, a relationship of _{t WC ≦ t0 <1.09 × t} WC ( although t0 is the thickness of the boundary ) Is preferable.

Further, in the seamless can body according to any one of (1) to ( 3 ) above, ( 4 ) the 60-degree mirror glossiness from the lower end of the tubular body portion to the vicinity of the boundary portion is 300% or more. Is preferable.

Further, in the seamless can body according to any one of (1) to ( 4 ) above, ( 5 ) the outer peripheral bottom portion is formed from the second outer peripheral bottom portion continuous from the tubular body portion and the second outer peripheral bottom portion. When the plate thickness of the second outer peripheral bottom portion at the intermediate position in the height direction of the can is t1 and the plate thickness of the peripheral grounding portion is t2, t2 includes the peripheral ground contact portion located inside. > T1 is preferable.

Further, in the seamless can body described in ( 5 ) above, ( 6 ) the bottom portion of the can further includes an inner end portion located inside the peripheral ground contact portion, and the plate thickness of the inner end portion is t3. When, it is preferable that t3> t1.

Further, in the seamless can body according to any one of ( 6 ) above, ( 7 ) the plate thickness gradually increases from the bottom of the second outer circumference to the inner end so that t3 is larger than t2. Is preferable.

In order to achieve the above object, the method for manufacturing a seamless can body in one embodiment of the present invention is to: ( 8 ) from a tubular body whose metal material is thinned by ironing and a lower end of the tubular body. A first molding step of molding into a cup body having a subsequent outer peripheral bottom portion and a bulging portion that bulges at a first height from the outer peripheral bottom portion toward the opening, and a second molding lower than the first height. In the first molding step, the thickness of the lower end of the tubular body portion is an intermediate portion in the axial direction of the tubular body portion, including a second molding step of pushing down the bulging portion so as to have a height of The lower end of the tubular body is pulled in so as to be substantially equal to the plate thickness of the above, and the outer peripheral bottom is formed so as to reduce the diameter inward from the lower end of the tubular body through the boundary. It is characterized by that.

According to the present invention, it is possible to obtain a seamless can body in which the can body portion has high glossiness from the upper end to the lower end in the axial direction and has uniform mapping property.

It is a schematic diagram which shows the whole vertical cross section of the seamless can body 1a in 1st Embodiment. It is a comparative figure in the vicinity of the lower end 10e of the tubular body portion 10 between the seamless can body 1a in the first embodiment and the seamless can body in the conventional structure. It is a figure which shows the 1st molding process in the manufacturing method of a seamless can body 1a. It is a schematic diagram which partially enlarged each of the α part and β part in FIG. It is a figure which shows the 2nd molding process in the manufacturing method of a seamless can body 1a. It is a schematic diagram which shows the compressive stress applied to the rising part in 1st Embodiment. It is a schematic diagram which shows a part of the seamless can body 1b in 2nd Embodiment. It is an enlarged view which shows the can bottom of the seamless can body 1b. It is a graph which shows the plate thickness of each point in a seamless can body 1b. It is a schematic diagram for comparing the structure of the seamless can body by the conventional method and the seamless can body by this embodiment. It is a schematic diagram which shows another example (the 1) applicable to the 1st molding process in the manufacturing method of the seamless can body 1a shown in FIG. It is a schematic diagram which shows another example (the 2) applicable to the 1st molding process in the manufacturing method of the seamless can body 1a shown in FIG. It is a schematic diagram for demonstrating the position of the boundary part BP in this embodiment.

Hereinafter, the seamless can body of the present invention and the method for producing the same will be specifically described with reference to the drawings as appropriate. In addition, the following embodiment shows an example of the present invention and describes the content thereof, and does not intentionally limit the present invention.

[First Embodiment]
<Seamless can body 1a>
As shown in FIG. 1, the seamless can body 1a of the present embodiment has a tubular body portion 10 and an outer peripheral bottom portion 20a that is continuous so as to reduce the diameter inward from the lower end of the tubular body portion 10 via the boundary portion BP. It is a seamless can body having a can bottom portion 20 provided with at least. In the illustration, the neck / flange shape is drawn above the tubular body 10 as an example, but a known seamless can body structure having an opening 10a above the tubular body 10 can be applied. Here, the "lower end 10e of the tubular body portion 10" in the present embodiment is a portion substantially located at the lower end of the cylindrical surface, and is known, for example, when printing is performed on the outer surface of the seamless can body. It can be defined as the lower end of the area where curved surface printing by the dry offset method is possible.

The tubular body portion 10 is a portion that constitutes the side surface of the seamless can body 1a, and is formed by drawing and ironing a known metal plate such as aluminum or steel, which will be described later. The tubular body portion 10 has a width depending on the application, but is configured to have a thickness of, for example, about 0.07 to 0.40 mm.
The tubular body portion 10 in the present embodiment is defined with the lower end portion 10e, which will be described later, as the lower end portion, and the upper end portion up to the boundary with the neck shoulder (a portion whose diameter is reduced as it goes upward in the axial direction) as shown in FIG. Will be done.

As shown in FIG. 1, the can bottom portion 20 has a continuous outer peripheral bottom portion 20a that contracts inward from the lower end 10e of the tubular body portion 10 and a bulge that bulges from the outer peripheral bottom portion 20a toward the opening 10a. It is configured to include at least part 20b.
As is clear from FIG. 1, the outer peripheral bottom portion 20a and the bulging portion 20b in the present embodiment are separated by a circumferential grounding portion 20c that is grounded when the seamless can body 1a is placed on a flat surface such as a table. Has been done.

Further, the "boundary portion BP" in the present embodiment is a boundary of a region related to the appearance on the bottom side of the can (that is, normally observable from the outside of the can), and is a tubular body as shown in FIG. It is defined as a point that is inflectional from the lower end 10e of the portion 10 and is continuous to the outer peripheral bottom portion 20a, and the angle γ formed by the tangent line of the outer surface and the ground contact surface P at this boundary portion BP is 45 °. Will be done.

The reason for defining the point where the angle γ is 45 ° in the present embodiment as the boundary portion BP is as follows. That is, at a position where this γ is smaller than 45 °, the above-mentioned normal of the outer surface becomes too downward. Then, for example, when the can to which the present invention is applied is normally placed on a display shelf or the like (upright), it becomes difficult for the reflected light to enter the field of view, so that the excellent glossiness of the outer surface of the can, which is the main object of the present invention, is obtained. This is because it becomes difficult to exert.

As shown in FIG. 2A, in the conventional structure, the amount of the thin portion of the tubular body portion drawn downward when molding the above-mentioned dome portion is very small, so that the vicinity of the above-mentioned boundary portion BP Is a relatively thick part.
On the other hand, in the seamless can body 1a of the present embodiment, as shown in FIG. 2B, one of the lower end side of the tubular body portion 10 including the lower end 10e of the tubular body portion 10 that has undergone ironing processing. Since the portion is pulled toward the outer peripheral bottom portion 20a, the metal plate after the ironing process is formed so as to exceed the boundary portion BP and at least to the vicinity of the boundary portion BP in the outer peripheral bottom portion 20a.

In other words, in the seamless can body 1a of the present embodiment, at least the plate thickness t0 at the boundary portion BP is substantially equal to the plate thickness _tWC (see FIG. 1) at the intermediate portion of the tubular body portion 10. I can say.
Therefore, the tubular body portion 10 of the present embodiment has higher glossiness from the upper end to the lower end and the position of the boundary portion BP in the axial direction (Z direction in FIG. 1) as compared with the conventional structure, and has uniform imageability. It is possible to demonstrate. The ironing rate for the tubular body 10 that has undergone ironing to exhibit high glossiness is not limited to this because it varies depending on the characteristics of the material used and the processing conditions, but as an example, the total ironing rate is at least 60% or more. Is preferable.

In the present embodiment, as shown in FIG. 1, the plate thickness in the vicinity of the boundary portion BP (for example, the lower end of the tubular body portion 10) of the tubular body portion 10 is _tWL, and the axial direction of the tubular body portion 10 is set. If the thickness of the intermediate portion in the (Z direction) and _{t WC,} have a relationship of _{t WC ≦ t WL <1.09 ×} t WC, more preferably from _{t WC ≦ t WL <1.05 ×} t WC It is desirable to have a relationship. This makes it possible to maintain the pressure resistance of the seamless can body 1a while improving the imageability of the side surface of the can. The "intermediate portion in the axial direction of the tubular body portion 10" in the present embodiment does not necessarily have to be strictly an intermediate plate thickness in the axial direction, and can be defined to include the vicinity of the intermediate plate.

Further, in the present embodiment, similarly as shown in FIG. 1, when the thickness of the intermediate portion in the axial direction of the cylindrical body 10 and _{t WC,} have a relationship of _{t WC ≦ t0 <1.09 × t} WC More preferably, it is desirable that the relationship is _tWC ≦ t0 <1.05 × _tWC . t0 is a problem that there is a possibility that the axial load strength of this portion is lowered may occur is less than t _WC, t0 glossiness at the lower end portion of a the cylindrical body by 1.09 times or more of t _WC is This is because there arises a problem that the amount is lowered and the effect of the present invention is difficult to obtain.
This makes it possible to maintain the pressure resistance of the seamless can body 1a while improving the imageability of the side surface of the can.

Further, since the metal plate after the ironing process reaches at least a part of the outer peripheral bottom portion 20a beyond the boundary portion BP, the 60-degree mirror glossiness in the vicinity of the boundary portion BP from the lower end 10e of the tubular body portion 10 is 300%. The above is desirable. If the 60-degree mirror glossiness in the vicinity of the boundary portion BP is less than 300%, there arises a problem that the appealing power as a product is lowered because the surface becomes rough or dull in the corresponding portion in appearance. Because.
The mirror glossiness of this embodiment is measured according to the measuring method specified in JIS Z 8741-1997.

In the present embodiment, the type of metal material used for the seamless can body 1a is not particularly limited. That is, a known metal plate usually used for a seamless can body, for example, an aluminum alloy plate or a steel plate (for example, tin plate) can be used. Further, the metal plate may be appropriately surface-coated, such as one in which a known film is laminated on the inner surface side thereof, one coated with an organic resin, or one subjected to chemical conversion treatment.
Further, the seamless can body 1a of the present embodiment is subjected to, for example, known flange processing, necking processing, screw processing, etc., and after beer, sparkling beverage, coffee, juice, liquid food, etc. are contained as contents. , The lid is attached to the opening 10a by a known method.

<Manufacturing method of seamless can body 1a>
Next, the method for manufacturing the seamless can body 1a in the present embodiment will be described with reference to FIGS. 3 to 6 as appropriate.
The method for manufacturing the seamless can body 1a in the present embodiment is a method for manufacturing the seamless can body having the tubular body portion 10 and the can bottom portion 20 as shown in FIG. 1, and is the first molding described in detail below. It is characterized by including a step and a second molding step.

[First molding process]
In the method for manufacturing the seamless can body 1a in the present embodiment, as in the first molding step shown in FIG. 3, a metal material (precursor 3) is used for the tubular body portion 10 and the lower end of the tubular body portion 10. It has an inclined portion S extending inward and upward from the boundary portion BP in the above portion, and a cup dome portion D extending upward from the end portion Se of the inclined portion S at a first height Ho. Mold into cup body 2. Here, the end portion Se of the inclined portion S can also be said to be a connection point with the cup dome portion D.

Then, the first molding step of the present embodiment is carried out by using the upper die and the lower die with respect to the precursor 3 in which the tubular body portion 10 thinned by ironing by a known pressing step or the like is formed. To. That is, the first molding step of the present embodiment can be performed at the end position (near the bottom dead center) of the punch stroke of the molding machine that performs the ironing process, and is different from the machine that performed the ironing process. It is also possible to do it at.
As a specific example, as shown in FIG. 3, a tubular punch 401 located in and supporting the precursor 3 having a cup shape, and the outer peripheral bottom portion of the precursor 3 cooperate with the punch 401. The first molding step is carried out by the doming die 501 that works and supports. Of these, the lower end of the punch 401 has an upwardly convex concave shape corresponding to the doming die 501, and a peripheral wall portion 402 is formed along the circumferential direction. In FIG. 3 in the present embodiment, a single circular arc is illustrated as the cross-sectional shape of the peripheral wall portion 402, but the cross-sectional shape is not limited to this shape, and a plurality of arcs and tapered surfaces are shown, for example, as shown in FIGS. 11 or 12. It may be a combination of shapes.

First, when the precursor 3 is pressed so as to sandwich the precursor 3 between the punch 401 and the doming die 501, the bottom surface of the precursor 3 bulges toward the opening by the doming die 501, and the lower end peripheral edge is pulled by the peripheral wall portion 402. It becomes. In other words, in the first molding step, the peripheral wall portion 402 of the punch 401 supports the outer periphery of the precursor 3, and the punch 401 and the doming die 501 are driven so as to mesh with each other, thereby increasing the height to the bottom. A cup body 2 having a cup dome portion D of Ho can be obtained.

If wrinkles occur in the peripheral wall portion 402 and its vicinity when forming the cup dome portion D in this first molding step, a wrinkle pressing member 80 (also referred to as a holddown ring) illustrated in FIG. 12 is used as necessary. It can also be installed and molded by applying a wrinkle pressing force by the peripheral wall portion 402 and the wrinkle pressing member 80.

At this time, the amounts of the materials constituting the cup dome portion D, the end portion Se, and the inclined portion S are adjusted so that the can bottom portion 20 in FIG. 1 can be formed by the second molding step later. It is necessary to set the height Ho of. As a result, the height Ho in the present embodiment is higher than the height of the dome of the conventional structure, and therefore the amount of the tubular body portion 10 drawn toward the outer peripheral bottom portion 20a is also increased accordingly.

As a result, as shown in FIG. 4, the portion that normally constitutes the lower end of the tubular body portion 10 during the ironing process exceeds the boundary portion BP between the tubular body portion 10 and the outer peripheral bottom portion 20a and is the outer peripheral bottom portion. It will be pulled in to the 20a side (more specifically, in the example shown in FIG. 4, the points A and B located on the tubular body are pulled in beyond the boundary portion BP, respectively). In other words, in this first molding step, a part of the outer peripheral bottom portion 20a (substantially still) in which the lower end 10e of the tubular body portion 10 is pulled in and the diameter is reduced from the lower end 10e of the tubular body portion 10 to be continuous. It is a state of a curved surface near the boundary portion BP, and this is referred to as a first outer peripheral bottom portion 20a').

Here, the shape of the cup body 2 obtained by the first molding step will be described.
The inclined portion S in the cup body 2 extends inward and upward from the first outer peripheral bottom portion 20a'. That is, as shown in FIG. 3C and the like, the inclined portion S of the cup body 2 is sandwiched between the lowest portion of the cup body 2 in the Z-axis direction and the connection point (end portion Se) with the cup dome portion D. It shall refer to the curved part and the straight part.
In the first molding step, the inclined portion S and the cup dome portion D described above are also referred to as a bulging portion. Therefore, it can be said that the cup body 2 of the present embodiment includes a tubular body portion 10 and a bulging portion formed on the bottom surface of the tubular body portion 10.
The shape of the cup dome portion D described above is an example, and the top of the dome may not be curved but may be horizontal, for example.

Further, the height Ho of the cup dome portion D in the cup body 2 is preferably larger than the height Hp of the can dome portion 201d in the seamless can body 1 obtained by the second molding step described later. One of the reasons for this is to apply compressive stress to the inclined portion S while pushing down the cup dome portion D in the cup body 2 in the second molding step described later. That is, the height Ho of the cup dome portion D in the cup body 2 is increased in advance, and finally the preferable height Hp of the can dome portion 201d in the seamless can body 1 is obtained.

That is, in this first molding step, a bulging portion that bulges at the first height Ho from the first outer peripheral bottom portion 20a'near the boundary portion BP toward the opening 10a is first formed, and the second molding step described later. Then, the bulging portion is pushed down so as to have a second height lower than the first height Ho.

[Second molding process]
Next, the second molding step of the manufacturing method of the seamless can body 1a in the present embodiment will be described with reference to FIG.
After the cup body 2 having the first outer peripheral bottom portion 20a'and the inclined portion S is molded by the first molding step, the following second molding step is performed.

In addition, between the first molding step and the second molding step, the cup body 2 is appropriately known as a cleaning step, a surface treatment step, a printing step, a painting step, and a shape imparting process to the tubular body. Alternatively, neck-in (mouth drawing) processing or the like may be performed within a range that does not hinder the second molding step. Further, if necessary, for the purpose of ensuring the transportability and corrosion resistance after the first molding step, the outer surface coating can be applied to the portion in the range from the ground contact portion at the lowermost end of the cup body 2 to the inclined portion S.

In the second molding step, the cup body 2 is processed by a different mold in the above-mentioned first molding step, and the seamless can body 1a is molded. That is, as shown in FIG. 5, while the cup body 2 is brought into contact with the lower mold forming member, the upper mold forming member is used in the can outer direction (−Z axis direction) with respect to the cup dome portion D of the cup body 2. Apply pressing force.

More specifically, as shown in FIG. 5A, the vicinity of the boundary portion BP of the cup body 2 is placed on the cup outer peripheral side holder 60. Next, the dome pushing tool 70 is relatively lowered, and the support portion 701 of the dome pushing tool 70 comes into contact with the cup dome portion D as shown in FIG. 5 (b). In FIG. 5, the shape of the support portion 701 is drawn to substantially match the shape of the cup dome portion D. However, for example, a difference in curvature is provided so that strong pressure is applied to the outer peripheral portion of the cup dome portion D. It is not always necessary to match the shapes.

Here, the cup outer peripheral side holder 60 has a tapered surface 601 and a groove 602, and after the boundary portion BP of the cup body 2 and the first outer peripheral bottom portion 20a ′ come into contact with the tapered surface 601, the dome pushing tool 70 moves. It is pushed down further. As a result, as shown in FIG. 5C, the metal of the inclined portion S of the cup body 2 is formed so as to follow the tapered surface 601 while receiving compressive stress.

Next, as shown in FIG. 5D, when the dome pushing tool 70 is further pushed down, the remaining portion of the inclined portion S of the cup body 2 (the portion other than the metal following the tapered surface 601) is formed in the groove 602. You will be guided. At this time, the cup dome portion D is pushed down so as to have a second height Hp lower than the first height Ho described above. At the same time, using the upper mold forming member (dome pushing tool) and the lower mold forming member (cup outer peripheral side holder), the compressive stress σ _{φ in the} meridian direction and the compressive stress σ _θ in the circumferential direction are applied to the inclined portion S. Make it work. (See Fig. 6)
As a result, the metal of the cup body 2 that imitates the tapered surface 601 constitutes the outer peripheral bottom portion 20a, the metal guided into the groove 602 constitutes the above-mentioned circumferential ground contact portion 20c, and further from the circumferential ground contact portion 20c. The upper part constitutes each of the bulging portions 20b. (See FIG. 5 (e))

FIG. 6 is a state diagram schematically showing a state in which the inclined portion S receives the compressive stress σ _{φ in the} meridian direction and the compressive stress σ _θ in the circumferential direction in the present embodiment.
As is clear from FIG. 6, when the inclined portion S is pressed against the lower mold forming member, the thickness of the metal material in the inclined portion S increases (arrow direction σ _ψ in FIG. 6).
In this way, the can bottom 20 of the seamless can body 1a can be obtained after the second molding step.
When the above molding is completed, as shown in FIG. 5E, the dome pushing tool may be relatively raised and the seamless can body 1 may be taken out from the cup outer peripheral side holder.

In the seamless can body 1a molded by the manufacturing method according to the present embodiment described above, first, the tubular body portion 10 which is the side surface of the can can form a substantially uniform surface state from the upper end to the lower end in the axial direction. It can exhibit excellent appearance and mapping.

[Second Embodiment]
<Seamless can body 1b>
Next, the seamless can body 1b according to the second embodiment of the present invention will be described with reference to FIGS. 7 to 9 as appropriate. Elements having the same configuration and function as the seamless can body 1a of the first embodiment are designated by the same numbers, and the description thereof will be omitted as appropriate.
First, as shown in FIG. 7, the seamless can body 1b of the present embodiment is basically a seamless can body having a tubular body portion 10 and a can bottom portion 20 as in the first embodiment.

On the other hand, as shown in FIG. 7, the can bottom portion 20 in the present embodiment has a can bottom central portion 201 that does not come into contact with the horizontal plane when the seamless can body 1b is placed on the horizontal plane, and the outside of the can bottom central portion 201. It is preferable to include the foot portion 202 located at.
The foot portion 202 corresponds to the outer peripheral bottom portion 20a, the circumferential ground contact portion 20c, and the bulging portion 20b in the first embodiment.
Further, similarly to the first embodiment, the can bottom central portion 201 of the seamless can body 1b in the present embodiment may have a horizontal shape, or as shown in FIG. 7, rises toward the inner surface of the can (convex upward). It may have a dome shape (which bulges so as to become).

In the present embodiment, as shown in FIG. 7, the foot portion 202 in the can bottom portion 20 is the outermost end 201e of the can bottom central portion 201 from the lower end 10e of the tubular body portion 10 toward the can body axis RA direction. Is defined as the part up to.
In the present embodiment, as shown in the enlarged cross-sectional view of the foot portion 202 in FIG. 8, the “outermost end 201e of the can bottom central portion 201” is the case where the can bottom central portion 201 has a dome shape. The part where the diameter of the dome is the largest in the dome shape.

As described above, in the present embodiment, the lowermost portion of the foot portion 202 in the Z-axis direction is referred to as the circumferential ground contact portion 202b. That is, the circumferential ground contact portion 202b can be said to be a portion that comes into contact with the horizontal plane when the seamless can body 1 of the present embodiment is placed on the horizontal plane.
Then, the area from the lower end 10e of the tubular body portion 10 to the peripheral ground contact portion 202b is defined as the second outer peripheral bottom portion 202a.

In the present embodiment, the foot portion 202 has a second outer peripheral bottom portion 202a that is continuous so as to reduce the diameter inward from the lower end 10e of the tubular body portion 10, and a circumferential shape that is located inside the second outer peripheral bottom portion 202a. The grounding portion 202b and the like are included.
In other words, in the seamless can body 1b of the present embodiment, the second outer peripheral bottom portion 202a is located in a ring shape to the lower end 10e of the tubular body portion 10 outside the peripheral ground contact portion 202b.

In the present embodiment, the ring width and the area of the second outer peripheral bottom portion 202a are not particularly limited, and a known shape can be applied to the inclination angle and the curved state thereof. That is, the cross section may be linear, may be arcuate curved toward the inside of the can body, or conversely may be arcuate curved outward. Further, a part may be curved inward and the rest may be curved outward, and these may be continuously connected.
As shown in FIG. 8, the second outer peripheral bottom portion 202a may have an inflection point IP in its cross-sectional view. For example, when the seamless can body 1b is canned, another canned product may be placed on the lid of the same type of canned product. It is preferable because it is easy to stack and place.

As shown in FIGS. 7 and 8, the seamless can body 1b of the present embodiment further includes an inner end portion 202c located inside the peripheral ground contact portion 202b. The inner end portion 202c is defined as the portion of the above-mentioned foot portion 202 closest to the can body axis RA side in the cross-sectional view.
Further, the seamless can body 1b of the present embodiment includes a rising portion 202d extending upward (+ direction of the Z axis) from the inner end portion 202c. The rising portion 202d is defined as a portion from the inner end portion 202c to the outermost end 201e in the can bottom central portion 201 direction in the cross-sectional view shown in FIG. 7 or FIG.

In the seamless can body 1b of the present embodiment, the plate thickness of the second outer peripheral bottom portion 202a at the intermediate position in the height direction of the can is t1 (see FIG. 13 and the like), and the plate thickness of the peripheral ground contact portion 202b is t2. In each case, it is preferable that the relationship of "t2> t1" is established. The method for measuring the thickness of the above-mentioned plate thickness is as follows. That is, after the molded seamless can body 1 was embedded with the epoxy resin, the entire epoxy resin was cut along the vertical axis (Z axis) of the seamless can body 1. Then, after the central cross section was exposed by careful polishing after this cutting, the thicknesses of the t1 and t2 portions were measured with a measuring microscope.

By satisfying such a relationship, in the seamless can body 1b of the present embodiment, it is possible to impart a particularly preferable pressure resistance in the case of a canning application that requires internal pressure resistance.
Since the thickness of the foot portion 202 changes from the boundary portion BP (see FIG. 8) toward the circumferential ground contact portion 202b, the actual thickness is t1 as is clear from FIGS. 1, 2 and 4. The position is shifted to the circumferential grounding portion 202b side from the position of the plate thickness t0 at the boundary portion BP with the tubular body portion 10 described in the first embodiment described above.

As described above, the outer peripheral bottom portion of the present embodiment includes a second outer peripheral bottom portion 202a continuous from the tubular body portion 10 and a circumferential ground contact portion 202b located inside the second outer peripheral bottom portion 202a. Then, as described above, the relationship t2> t1 is established between the plate thickness t1 at the intermediate position of the second outer peripheral bottom portion 202a in the height direction of the can and the plate thickness t2 of the peripheral ground contact portion 202b described above. It will be.

Here, in the seamless can body 1b of the present embodiment, it is preferable that the relationship of "t3> t1" is further established when the plate thickness of the inner end portion 202c is t3. By satisfying such a relationship, it is possible to impart preferable pressure resistance to the seamless can body 1b of the present embodiment.

FIG. 9 shows a graph comparing the plate thicknesses of each point in the seamless can body 1b suitable for the present embodiment as an example. In addition, tz indicates the plate thickness of the metal plate (base plate) before seamless can body processing.
The reason for such a thickness regulation is as follows.
That is, when the liquid contained in the seamless can body is beer or a carbonated beverage, internal pressure is always applied to the bottom of the can. When an impact is applied to the bottom of the can while the internal pressure is applied in this way, or when the internal pressure applied to the bottom of the can suddenly increases for some reason, the internal pressure of the can exceeds the pressure resistance strength of the bottom of the can. A phenomenon (buckling) in which the dome portion of the bottom of the can is inverted occurs.

On the other hand, in the present embodiment, the lower end 10e of the tubular body portion 10 is pulled toward the side of the second outer peripheral bottom portion 202a beyond the boundary portion BP, and the can bottom is thickened to increase the pressure resistance strength of the can bottom. Realized to do.
As a result, according to the present embodiment, with respect to the tubular body 10, distortion is suppressed from the upper end to the lower end, and while exhibiting excellent appearance and mapping, the demand for weight reduction and pressure resistance of the can bottom is high. It is possible to achieve both.

In the seamless can body 1b of the present embodiment, as shown in FIGS. 7 and 8, the foot portion 202 of the can bottom portion 20 is a can at the outermost end 201e via the inner end portion 202c and the rising portion 202d. It is connected to the bottom central portion 201 (can dome portion 201d).
Then, as shown in FIG. 7, the rising portion 202d of the present embodiment is directed upward so that the inner diameter (dx) of the outermost end 201e described above is larger than the inner diameter (dy) of the inner end 202c. It is preferable that the can bottom is stretched so as to be spread out and connected to the can bottom central portion 201 (can dome portion 201d).

In other words, as shown in FIGS. 7 and 8, in the vicinity of the outermost end 201e, the cross-sectional view is generally in the shape of “⊂” or “⊃”.
In other words, the seamless can body 1b of the present embodiment is located most toward the outside of the can body axis RA between the inner end portion 202c and the can dome portion 201d in the + direction of the Z axis. It is preferable that the outer end 201e has a convex ring groove.
By forming the shape as described above, it is possible to improve the pressure resistance of the seamless can body 1b of the present embodiment.

As described above, in the present embodiment, it is preferable that the second outer peripheral bottom portion 202a has an inflection point IP in its cross-sectional view. As shown in FIG. 8, the inflection point IP may be located in the + direction of the Z axis with respect to the outermost end 201e, or conversely, may be located in the − direction of the Z axis.

Further, in the present embodiment, when the plate thickness of the outermost end 201e portion where the rising portion 202d and the can bottom central portion 201 are connected is t4, the relationship of "t4> t1" is also established, which is also pressure resistant. From the point of view, it is preferable.

As shown in FIG. 7, the seamless can body 1b of the present embodiment further preferably includes a can dome portion 201d in the can bottom portion 20 that bulges upward in succession with the rising portion 202d. That is, in the present embodiment, it is preferable that the shape of the central portion 201 of the can bottom is a dome shape as shown in FIG.

Then, it is preferable that the following relationship is satisfied in the relationship between the plate thickness (t3) of the inner end portion 202c and the plate thickness (t4) of the rising portion 202d.
t3> t4
That is, this means that the plate thickness of the metal plate continuous from the central portion of the can dome portion 201d to the inner end portion 202c toward the outside gradually increases.

Further, in the present embodiment, as shown in FIG. 9, when the plate thickness of the base plate (blank) is tz, "t1>tz","t2>tz","t3>tz", and "t4". It is preferable to satisfy the relationship of ">tz" from the viewpoint of achieving both pressure resistance and weight reduction, which are desired for the seamless can body 1b.
On the other hand, in the present embodiment, there is no problem even if the plate thickness (t5) near the center of the can dome portion 201d is equal to or less than the plate thickness (ts) of the base plate (blank) (t5 ≦ tz).

In this embodiment, as shown in FIG. 9, it is preferable that each plate thickness has a relationship of "t3>t2>t1". In other words, it is preferable that the plate thickness is gradually increased in the order of the second outer peripheral bottom portion 202a, the circumferential ground contact portion 202b, and the inner end portion 202c.
By satisfying each of the above relationships, it is possible to superimpose and impart preferable pressure resistance in the seamless can body 1 of the present embodiment.

The thickness tz of the base plate (blank) may be any thickness as long as it is usually used when a seamless can body is manufactured, and a metal plate having a thickness of about tz = 0.15 mm to 0.4 mm may be used depending on the application. It can be punched out and used as a base plate (blank), but is not limited to the above thickness.

Further, the method for manufacturing the seamless can body 1b in the present embodiment can be carried out, for example, by applying the molding mold used in the first embodiment described above.
More specifically, the outer peripheral side of the cup is formed so that the second outer peripheral bottom portion 202a, the circumferential ground contact portion 202b, the inner end portion 202c, the rising portion 202d, and the can dome portion 201d are respectively molded in the second molding step. The groove 602 of the holder 60, the lower end shape of the dome pushing tool 70, and the like may be improved.

As described above, the second molding step in the present embodiment has the following features.
That is, in the second molding step, the above-mentioned cup body 2 is pressed against the lower mold molding member (cup outer peripheral side holder 60) in the second molding step, so that the inclined portion S is made to be the second outer peripheral bottom portion 202a. The peripheral ground contact portion 202b located inside the second outer peripheral bottom portion 202a, the inner end portion 202c located inside the peripheral ground contact portion 202b, and the can dome rising upward from the inner end portion 202c. It is formed in a rising portion 202d connected to the portion 201d.

Further, by this second molding step, the inner diameter (dx) of the connection point (outermost end 201e) between the rising portion 202d of the seamless can body 1b and the can dome portion 201d is changed to the inner diameter (dy) of the inner end portion 202c. A ring groove is formed in which the outermost end 201e is convex toward the outside of the can body shaft RA so as to be larger than the above.

As described above, in the second molding step of the present embodiment, the portion that was the inclined portion S of the cup body 2 is combined with the portion that formed the first outer peripheral bottom portion 20a'in the first molding step to form the second outer peripheral bottom portion 202a. In addition to being configured, it is further formed into the above-mentioned circumferential ground contact portion 202b, inner end portion 202c, and rising portion 202d.

By going through the above steps, the seamless can body 1b of the present embodiment is formed.
In the seamless can body 1b formed by the manufacturing method according to the present embodiment, the tubular body portion 10 which is the side surface of the can forms a substantially uniform surface state from the upper end to the lower end in the axial direction, and has excellent appearance and imageability. At the same time, it is possible to achieve both excellent pressure resistance at the bottom of the can.

Here, it will be described again with reference to FIG. 10 that the seamless can bodies 1a and 1b described in each of the above embodiments are advantageous over the conventional structure. Here, FIG. 10 (a) shows an excerpt of the structure near the lower end of the can body in the seamless can body immediately after being ironed by the conventional manufacturing method, and FIG. 10 (b) further performs dome forming. The structure near the lower end of the can body is excerpted and shown. On the other hand, FIG. 10C shows an excerpt of the structure near the lower end of the can body portion in the seamless can body 1a or 1b of the present embodiment. In FIG. 10C, the plate thickness t _{WL at} the lower end of the tubular body portion 10 is equal to the plate thickness t _WC of the intermediate portion in the axial direction of the tubular body portion, but the present invention is not limited to this embodiment and t _WL < As described above, it may be 1.09 × t _WC .

That is, when the ironing process for forming the seamless can body is performed, first, as described above, in FIG. 10A of the conventional method, the ironing process is started at the ironing rate 0 at the point B, and the ironing process is performed as it approaches the point A. The rate increases, and the squeezing rate becomes maximum after point A. Therefore, for example, the glossiness of the ironed surface of the can body is almost the same as the original material surface at point B, the glossiness increases as it approaches point A, and the maximum glossiness after point A. It will show the degree.

Then, FIG. 10B shows a state in which the dome portion is formed at the bottom of the can by relatively immersing the doming die inside the tip of the ironing punch after the ironing process is completed. As a result, a part of the bottom of the can is pulled into the dome part, and the part originally located at the point A shifts to the point A', and the part originally located at the point B shifts to the point B'. .. The amount of deviation of each part of the above-mentioned conventional method is, for example, about 2 to 5 mm. Therefore, a portion having a low glossiness and a poor print quality remains at the lowermost portion of the cylindrical portion of the can body.

On the other hand, in the seamless can body of the present embodiment, as is clear from FIG. 10C and the like, the metal plate after the ironing process exceeds the boundary portion BP and reaches at least a part of the outer peripheral bottom portion. The glossiness near the BP is equivalent to that of the can body. This makes it possible for the can body to have a high glossiness from the upper end to the lower end in the axial direction.

The first embodiment and the second embodiment described above are examples that embody the gist of the present invention, and may be appropriately modified without departing from the above gist of the present invention. Further, a known structure may be added to the seamless can body shown in the first embodiment and the second embodiment without departing from the above gist of the present invention.

The present invention can be applied to containers that are required to have improved appearance and mapping, and can be particularly applied to cans that can store liquids such as beverages and chemicals.

1a, 1b Seamless can body 2 Cup body 3 Precursor 10 Cylindrical body 10a Opening 10e Lower end 20 Can bottom 20a Outer outer bottom 20a'First outer peripheral bottom 20b Swelling 201 Can bottom center 201d Can dome 201e Outermost End 202 Foot 202a Second outer peripheral bottom 202b Circumferential ground contact 202c Inner end 202d Rising part D Cup dome part S Inclined part Se End part Hp Height of can dome part (second height)
Ho cup dome height (first height)
60 Lower mold member 70 Upper mold member

Claims (8)

A tubular body portion and a can bottom portion having at least a continuous outer peripheral bottom portion whose diameter is reduced inward from the lower end of the tubular body portion via a boundary portion.
The plate thickness at the lower end of the tubular body portion, the plate thickness at the boundary portion, and the plate thickness at least a part of the outer peripheral bottom portion are substantially equal to the plate thickness of the intermediate portion in the axial direction of the tubular body portion , respectively. , A seamless can body that features. When the plate thickness at the lower end of the tubular body portion is t _WL and the plate thickness of the intermediate portion in the axial direction of the tubular body portion is t _WC .
t _WC ≤ t _WL <1.09 × t _WC
The seamless can body according to claim 1, which is related to the above. In the tubular body,
t _WC ≤ t 0 <1.09 × t _WC
(However, t0 is the plate thickness of the boundary portion), the seamless can body according to claim 2 . The seamless can body according to any one of claims 1 to 3 , wherein the 60-degree mirror surface glossiness from the lower end of the tubular body portion to the vicinity of the boundary portion is 300% or more. The outer peripheral bottom portion includes a second outer peripheral bottom portion continuous from the tubular body portion and a circumferential ground contact portion located inside the second outer peripheral bottom portion.
When the plate thickness of the second outer peripheral bottom portion at the intermediate position in the height direction of the can is t1 and the plate thickness of the peripheral ground contact portion is t2,
t2> t1
The seamless can body according to any one of claims 1 to 4 . The can bottom further includes an inner end located inside the circumferential ground contact portion.
When the plate thickness of the inner end is t3,
t3> t1
The seamless can body according to claim 5 . The seamless can body according to claim 6 , wherein the plate thickness gradually increases from the second outer peripheral bottom portion to the inner end portion so that the t3 becomes larger than the t2. A tubular body whose wall thickness is thinned by ironing, an outer peripheral bottom portion that continues from the lower end of the tubular body portion, and a bulge that bulges at a first height from the outer peripheral bottom portion toward the opening. The first molding step of molding into a cup body having a portion and
Including a second molding step of pushing down the bulge so as to have a second height lower than the first height.
In the first molding step, the lower end of the tubular body portion is pulled in so that the plate thickness of the lower end of the tubular body portion is substantially equal to the plate thickness of the intermediate portion in the axial direction of the tubular body portion. A continuous outer peripheral bottom portion is formed so as to reduce the diameter inward from the lower end of the tubular body portion through the boundary portion.
A method for manufacturing a seamless can body.