WO2021181949A1

WO2021181949A1 - Seamless can body and method for producing seamless can body

Info

Publication number: WO2021181949A1
Application number: PCT/JP2021/003842
Authority: WO
Inventors: 具実小林
Original assignee: 東洋製罐グループホールディングス株式会社
Priority date: 2020-03-09
Filing date: 2021-02-03
Publication date: 2021-09-16
Also published as: US20230150711A1; JP7447564B2; TW202138080A; EP4119252A1; CN115210015A; JP2021138441A; EP4119252A4

Abstract

Provided is a seamless can body having excellent pressure resistance, and a method for producing the seamless can body. This seamless can body includes a tubular body section (10), a peripheral ground section (20b) continuing from a lower end of the tubular body section, and a raised bottom section (30) continuing toward the center-axis side from the peripheral ground section. When the outer surface area of the raised bottom section is defined as AD and the area of a virtual plane the outline of which is the peripheral ground section is defined as AB, the relationship 1.55≥(AD/AB) ≥1.40 is satisfied.

Description

Seamless can body and manufacturing method of seamless can body

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 can bodies, various proposals have been made in order to maintain or improve the pressure resistance performance even if the bottom portion of the can is thinned.

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 compressive 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 a can bottom located inside in a radial direction orthogonal to the can axis is disclosed.

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

That is, in the above-mentioned bottom reforming step, it is common to form a concave portion by pressing the inner peripheral wall of the can bottom with a forming roller or the like.
Further, in recent years, in order to reduce the weight of the seamless can body, it is required to further reduce the thickness of the base plate (blank) before the drawing and ironing process. However, when the bottom reform processing is performed, the thickness of the metal material of the pressing portion to which the molding roller or the like is abutted is extended and thinned by the processing, so that the thickness of the base plate (blank) is reduced. There was a limit to that.

As a result of repeated diligent studies in view of the above-exemplified problems, the present inventor has made it possible to provide a seamless can body having excellent pressure resistance performance and a method for manufacturing the same, which has led to the present invention.

The seamless can body according to the embodiment of the present invention includes (1) a tubular body portion, a circumferential ground contact portion connected from the lower end of the tubular body portion, and a raising extending from the peripheral ground contact portion toward the central axis side. includes a bottom portion, said raised bottom outer surface area a _D of _the area of the virtual plane to outline the circumferential ground portion a _B, and when defined, _{respectively, 1.55 ≧ (a D / a} B) It is characterized in that the relationship of ≧ 1.40 is satisfied.

In the seamless can body (1), wherein, (2) volume and V _D of the space surrounded by the virtual plane and the raised _portion, the volume of the metal member forming the raised bottom V _M, and when defined, respectively, preferably satisfies the relationship _{_{26.0 ≧ (V D / V M}} ) ≧ 22.0.

Further, in order to solve the above problems, in the method of manufacturing a seamless can body in one embodiment of the present invention, (3) a metal material is provided of a tubular body portion, an outer peripheral bottom portion continuing from the lower end of the tubular body portion, and the like. A first molding step of molding into a cup body having a bulging portion that bulges at a first height from the bottom of the outer periphery toward the opening, and a second height that is lower than the first height. A second molding step of pushing down the bulging portion to form a circumferential ground contact portion continuous from the lower end of the tubular body portion and a raised bottom portion continuous from the peripheral ground contact portion toward the central axis side. wherein, the raised bottom of the outer surface area _{a D} of, _{a B} the area of the virtual plane of the circumferential ground portion to the contour, and when defined, _{_{respectively, 1.55 ≧ (a D / a}} B) ≧ 1.40 It is characterized by satisfying the relationship of.

According to the present invention, it is possible to obtain a seamless can body in which the occurrence of buckling is prevented by the raised bottom portion having excellent pressure resistance performance with a smaller amount of material.

It is a schematic diagram which shows the whole vertical cross section of the seamless can body in an embodiment. It is an enlarged view which shows the can bottom of the seamless can body in an embodiment. The outer surface area A _D of the raised _portion, the area A _B of the virtual plane to outline the circumferential ground _portion, the volume V _M of the volume V _D, and metal member forming the raised bottom of the space surrounded by the virtual plane and the raised portion It is a schematic diagram for explaining each. It is a flowchart which shows the manufacturing method of the seamless can body in an embodiment. It is a figure which shows the 1st molding process in the manufacturing method of the seamless can body of an embodiment. It is a figure which shows the 2nd molding process in the manufacturing method of the seamless can body of an embodiment. It is a schematic diagram which shows the compressive stress applied to the rising part in an embodiment. It is a schematic diagram explaining the state transition of the provisional peripheral grounding part after the 1st molding process, and the peripheral grounding part after the 2nd molding process in the seamless can body in an embodiment. It is a schematic diagram which shows the application example of the organic film on the can bottom of a seamless can body. It is a schematic diagram which shows the periphery of the bottom of a can in an experimental example.

Hereinafter, the seamless can body of the present invention and the manufacturing method thereof 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 1>
As shown in FIG. 1, the seamless can body 1 of the present embodiment has a tubular body portion 10 and a can bottom portion 20 having at least an outer peripheral bottom portion 20a continuous from the lower end of the tubular body portion 10. It is a can body. In the figure, 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.

The tubular body portion 10 is a portion that constitutes the side surface of the seamless can body 1, 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 as an example.
The tubular body portion 10 in the present embodiment is defined with the lower end 10e, which will be described later, as the lower end, and the upper end 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 described above, and bulges from the inside of the outer peripheral bottom portion 20a toward the opening 10a. It is configured to include at least a raised bottom portion 30.
As is clear from FIG. 1, the outer peripheral bottom portion 20a and the raised bottom portion 30 in the present embodiment are separated by a circumferential grounding portion 20b that is grounded when the seamless can body 1 is placed on a flat surface such as a table. ing. In other words, it can be said that the circumferential ground contact portion 20b is a portion connected to the lower end 10e of the tubular body portion 10, and the outer peripheral bottom portion 20a is a portion located between the tubular body portion 10 and the circumferential ground contact portion 20b.

As described above, the seamless can body 1 includes a raised bottom portion 30 formed in a convex shape upward from the circumferential ground contact portion 20b. As is clear from the drawing, the raised bottom portion 30 of the present embodiment is formed so as to be continuous from the circumferential ground contact portion 20b toward the central axis side. In the present embodiment, the raised bottom portion 30 has a shape like a gentle dome (convex toward the tip) after rising from the circumferential ground contact portion 20b, but the shape is not limited to this form, and at least the top portion is at least. A part may be flat plate-shaped.

In the present embodiment, the type of metal material used for the seamless can body 1 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 at least one side, one coated with an organic resin, or one subjected to chemical conversion treatment.
Further, the seamless can body 1 of the present embodiment is subjected to, for example, known flange processing, necking processing, screw processing, etc., and after beer, soft drinks, coffee, juice, liquid foods, etc. are contained as contents. , A lid, a cap, or the like is attached to the opening 10a by a known method.

<Structural features of raised bottom 30>
Next, the structure of the raised bottom portion 30 in the present embodiment will be described in detail with reference to FIGS. 1 and 3.
As is clear from these figures, the raised bottom 30 of the seamless can body 1 of this embodiment, the outer surface area A _D of the raised bottom _30, the area of the virtual plane VP to outline the circumferential ground portion 20b A _B When each of the above is specified, the relationship shown by the following equation (1) is satisfied.
_{_{1.55 ≧ (A D / A B}} ) ≧ 1.40 ··· (1)

As mentioned above, in recent years, a wide variety of beverages have been introduced into the beverage market, such as so-called strong carbonated beverages that increase the internal pressure of cans. With the widening of this need, it can be assumed that excellent pressure resistance is required for seamless cans in which carbonated drinks such as strong carbonated drinks and beer and non-carbonated drinks such as fruit juice drinks are stored. It is conceivable to simply increase the plate thickness in order to improve the pressure resistance performance of the seamless can body, but this is not realistic because it causes an increase in the weight and cost of the can itself.

Therefore, as a result of diligent studies by the present inventor, it has been concluded that the raised bottom portion 30 disclosed in the present embodiment can exhibit excellent pressure resistance performance when satisfying the relational expression (1) above. That is, the above-mentioned (A D _{/ A} _B) is a concept bulging degree upward raised portion 30 in this embodiment made into parameters (numeric), as the expanded degree (A D _/ A _B ) Exceeds 1.40, a balance between the plate thickness and pressure resistance performance normally accepted in the product market can be secured.

Note the area of the outer surface area A _D and the virtual plane VP of the raised portion 30 A _B, which can be calculated by a known calculation formula can be obtained with good easily and accurately, for example by a commercial form measuring instrument. In this embodiment, as such a shape measuring machine, a contour record (model number 1600 DH) manufactured by Tokyo Seimitsu Co., Ltd. was used for measurement. That is, the shape data generated by the vertical movement of the stylus moving on the plane passing through the central axis of the cup is transferred to the CAD to obtain the cross-sectional shape, and based on this, the surface area as a rotating body and the plate thickness (measured separately) The volume was measured with sufficient precision (by multiplying the data).

On the other hand when serving as the bulging degree _(A D _/ A _B) is less than 1.40, can not be carried out ensuring rigidity of the raised portion, for example, waste of greater Senebanara not a cost increase and resources the thickness It becomes difficult to secure the balance between the above-mentioned plate thickness and the pressure resistance performance.
Note that although the upper limit of _(A D _/ A _B) as a bulge degree, can be variously set by the specifications of the can body market demands, for example, preferably 1.55 or less. When the _{_{(A D / A B)>}} 1.55, since inconvenience that leads to waste of increase or resource cost becomes excessive material area may occur.

Further, in consideration of transportation costs and the like, it is desirable that the seamless can body 1 of the present embodiment is lightweight while having excellent pressure resistance performance. As a result of the pursuit of the present inventor based on such a viewpoint, the raised bottom portion 30 disclosed in the present embodiment is reduced in weight in addition to the above-mentioned excellent pressure resistance performance when further satisfying the above-mentioned relational expression (2). It resulted in the realization of.
That is, the above-mentioned volume of V _D of the space surrounded by the virtual plane VP and the raised bottom _30, volume V _M of the metal member forming the raised bottom _30, and when defined, respectively, by the following equation (2) It is desirable to satisfy the relationship shown.
_{_{26.0 ≧ (V D / V M}} ) ≧ 22.0 ··· (2)

Note the same manner as described above, the volume V _M of the above-mentioned volume V _D and the metal member of the raised portion 30, can also be calculated by a known calculation formula, it is determined with ease and accuracy by a commercially available form measuring instrument can. In this embodiment, the shape measuring machine; Been (Tokyo Seimitsu Co., trade name contour records, model number 1600DH) also measured volume V _D and volume V _M with.

Incidentally, the above-mentioned _(V D _/ V _M) is functioning as a balance indicator of pressure resistance and light weight and the container having an internal volume in this embodiment, the upper limit of _(V D _/ V _M) is a 26 or less Is preferable. When the _{(V D / V M)>} 26, since disadvantages such as reduction cost increase and content weight than the improvement of withstand voltage performance can occur.

<Manufacturing method of seamless can body 1>
Next, the method for manufacturing the seamless can body 1 in the present embodiment will be described with reference to FIGS. 4 to 8 as appropriate.
The method for manufacturing the seamless can body 1 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, as STEP 1 as shown in FIG. It includes at least a first molding step and a subsequent second molding step as a STEP.

[First molding process]
In the method for manufacturing the seamless can body 1 in the present embodiment, in the first molding step, the metal material (precursor 3) is attached to the tubular body portion 10 and the outer peripheral bottom portion 20a continuing from the lower end 10e of the tubular body portion 10. And the cup body 2 having the bulging portion 4 bulging from the outer peripheral bottom portion 20a toward the opening at the first height Ho (see FIG. 5). At this time, the provisional circumferential ground contact portion 20a'is positioned at the lower end inside the tubular body portion 10 and at the boundary with the bulging portion 4. The cup body 2 can be formed by a known molding method such as drawing / re-drawing and drawing / ironing.
In other words, in this first molding step, the metal material (precursor 3) is divided into a tubular body portion 10 and a provisional peripheral ground contact portion 20a'located at the lower end inside the tubular body portion 10. It can be said that the cup body 2 has a bulging portion 4 having a first height Ho located inside the provisional peripheral ground contact portion 20a'.

As shown in the figure, the bulging portion 4 of the cup body 2 in the present embodiment has an inclined portion S extending inward and upward from the outer peripheral bottom portion 20a and a cup dome inside from the end portion Se of the inclined portion S. It is composed of a part D and. Further, in the method for manufacturing a seamless can body of the present embodiment, as a method for molding the tubular body portion 10, for example, a known method as described in JP-A-9-285832 can be adopted.

The steps illustrated in FIGS. 5A to 5C will be described in more detail.
First, a precursor 3 having a cup shape is prepared by forming a can body portion by a known method using the above-mentioned metal material (blank).
Then, the metal material (precursor 3) is directed toward the tubular body portion 10, the cup outer peripheral bottom portion A that continues so as to reduce the diameter from the lower end 10e of the tubular body portion 10, and the inner upper side from the cup outer peripheral bottom portion A. It is formed into a cup body 2 having the above-mentioned bulging portion 4 that bulges at the first height Ho. 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.

The first molding step shown in FIG. 5 may be carried out as a step of separating the precursor 3 in which the tubular body portion 10 is molded by a known press step or the like by using an upper mold and a lower mold. It can be done, or it can be done at the end of the stroke following the step of ironing.
As a specific example, as shown in FIG. 5, 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 holddown ring 501 that moves and supports the dosing die 502.

First, the tapered portion 402 of the punch 401 and the tapered support portion 503 of the holddown ring 501 hold the outer peripheral bottom portion of the precursor 3, and drive the punch 401 and the dome 502 so as to engage with each other so that they are relatively close to each other. Therefore, a cup body 2 having a Ho cup dome portion D at the bottom can be obtained.
Here, the shape of the cup body 2 obtained by the first molding step will be described. That is, the inclined portion S in the cup body 2 extends inward and upward from the outer peripheral bottom portion A of the cup.

That is, as shown in FIG. 5, the inclined portion S of the cup body 2 includes a curved portion sandwiched between the lowest portion of the cup body 2 in the Z-axis direction and the boundary (end Se) with the cup dome portion D. It shall refer to the straight part.
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.

Inclined portion S as shown in FIG. 5 (c), may even vertical, but it is more preferable to incline at a predetermined angle theta _1. _{That is, the angle θ 1} formed by the inclined portion S and the Z axis is preferably 5 ° to 30 °, and spray coating is easy when a coating film is formed on the inner surface by a spray coating method after the first molding step. Therefore, it is more preferably 10 ° to 30 °.

_{Further, for the radius of curvature R (see FIG. 5C) at the angle θ 2} formed by the inclined portion S from the bottom of the outer periphery of the cup, a curve in which a plurality of different radii of curvature are connected in addition to a single radius of curvature is set. You can also. For example, in the case of a single radius of curvature R, the thickness of the base plate (blank) is set to t0, and R = 5 × t0 to 15 × t0. It is more preferable because it facilitates spray coating when forming the above.
Further, it is preferable that the first height Ho of the cup dome portion D in the cup body 2 is larger than the height Hp of the raised bottom portion 30 in the seamless can body 1 obtained by the second molding step described later. The reason for this is that compressive stress is applied 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 first 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 raised bottom portion 30 in the seamless can body 1 is obtained.

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

That is, in the method for manufacturing the seamless can body 1 in the present embodiment, in this second molding step, the above-mentioned bulging portion 4 is pushed down so as to have a second height Hp lower than the above-mentioned first height Ho. , A peripheral ground contact portion 20b continuous from the lower end 10e of the tubular body portion 10 and a raised bottom portion 30 continuous from the peripheral ground contact portion 20b toward the central axis side are formed.
In other words, in this second molding step, by pushing down the above-mentioned bulging portion 4 with respect to the cup body 2, the peripheral ground contact portion 20b arranged at a position different from the provisional peripheral ground contact portion 20a', and the peripheral ground contact portion 20b. It can also be said that the raised bottom portion 30 having a height Hp lower than that of the first height Ho is formed.

Shape of the raised portion 30 at this time, as described above, satisfies the equation is defined by the area A _B of the outer surface area A _D and the virtual plane VP (1). The shape of the raised portion 30 in this case, the formula is defined as the volume V _D of the space surrounded by the virtual plane VP and the raised bottom 30, the volume of the metal member forming a raised bottom with a V _M ( It is desirable to satisfy 2).

More specifically, in the second molding step, the cup body 2 is processed with a mold different from the molding die in the above-mentioned first molding step to form the seamless can body 1. That is, while the cup body 2 is brought into contact with the lower mold forming member, a pressing force is applied to the cup dome portion D of the cup body 2 in the can outer direction (−Z axis direction) by using the upper mold forming member.
Alternatively, while the cup body 2 is brought into contact with the lower mold forming member and the upper mold forming member, a pressing force may be applied in the + Z axis direction using the lower mold forming member.

More specifically, as shown in FIG. 6, the cup outer peripheral bottom portion A of the cup body 2 is placed on the cup outer peripheral side holder 60. 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. Here, the cup outer peripheral side holder 60 has a tapered surface 601 and a groove 602, and the dome pushing tool 70 is further pushed down after the cup outer peripheral bottom portion A of the cup body 2 comes into contact with the tapered surface 601. The metal of the inclined portion S of the cup body 2 is guided into the groove 602 and pushed into the groove 602 while receiving compressive stress.

Then, the cup dome portion D is pushed down so as to have a second height Hp lower than the first height Ho. At the same time, using the upper mold forming member (dome pushing tool 70) and the lower mold forming member (cup outer peripheral side holder 60), the compressive stress σ _{φ in the} meridian direction and the compressive stress σ in the circumferential direction with respect to the inclined portion S. _{Let θ} act.
FIG. 7 is a schematic view showing the compressive stress applied when the inclined portion S is formed on the rising portion 20d in the present embodiment. That is, when the inclined portion S is pushed into the groove 602 of the lower mold forming member, the inclined portion S _{tries to imitate the compressive stress σ φ in the} meridional direction and the lower mold forming member by the pushing force of the dome pushing tool 70. _{The compressive stress σ θ in the} circumferential direction due to the movement inward in the radial direction acts at the same time, and the thickness of the metal material in the inclined portion S increases (the arrow direction σ _ψ in FIG. 7).

In this way, the seamless can body 1 is obtained after passing through the second molding step.
When the molding is completed, 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 60.
Here, the seamless can body 1 obtained after the second molding step is preferably the seamless can body 1 in the above-described embodiment.
That is, as shown in FIG. 1, the seamless can body 1 obtained after the second molding step has an outer peripheral bottom portion 20a and a peripheral ground contact portion 20b.

It is more preferable that the second molding step has the following characteristics.
That is, in the second molding step, by pushing the cup body 2 described above into the lower mold molding member (cup outer peripheral side holder 60) in the second molding step, the inclined portion S is positioned inside the outer peripheral bottom portion 20a. It is formed into a ground contact portion 20b, an inner end portion 20c located inside the peripheral ground contact portion 20b, and a rising portion 20d rising upward from the inner end portion 20c.

Further, in this second molding step, the can body shaft is set so that the inner diameter of the connection point (outermost end 20e) between the rising portion 20d and the dome portion 20f of the seamless can body 1 is larger than the inner diameter of the inner end portion 20c. A ring groove is formed in which the outermost end 20e is convex toward the outside of the dome. In other words, as shown in the figure, in the vicinity of the outermost end 20e, the cross-sectional view is generally in the shape of “⊂” or “⊃”.
Conventionally, there has been a reform molding method (bottom reform processing) for forming a ring groove as described above using a rotary roll or a split mold. However, with the conventional method, it is difficult to form a sufficiently deep groove because the processed portion tends to be thin.
On the other hand, according to the method shown in the present embodiment, the plate thickness of the ring groove portion does not tend to be thin, but rather tends to be thick, and a deep groove can be formed without difficulty.

In the method for manufacturing a seamless can body of the present embodiment, the shape and length of the upper portion of the outer peripheral bottom portion A of the cup body 2 are not changed between the first molding step and the second molding step.
That is, when the cup body 2 is placed on the cup outer peripheral side holder 60, the lowest point in the Z-axis direction of the surface where the cup outer peripheral bottom portion A of the cup body 2 and the tapered surface 601 of the cup outer peripheral side holder 60 come into contact is defined. Let it be the T point. The position of this T point does not change as the dome pushing tool 70 is lowered and the cup dome portion D is pushed down. (See Fig. 6)

On the other hand, due to the second molding step, the portion of the cup body 2 that was the inclined portion S becomes a part of the outer peripheral bottom portion 20a of the seamless can body 1, the peripheral ground contact portion 20b, the inner end portion 20c, and the rising portion 20d. It is molded (see also FIG. 2 and the like as appropriate). That is, most of the inclined portion S of the cup body 2 finally enters the groove 602 of the cup outer peripheral side holder 60.
In this second molding step, there is no significant sliding in the contact between the cup body 2 and the upper and lower molds. Therefore, the metal surface of the cup body 2 is not damaged, and it is not necessary to use a lubricant.

Further, the plate thickness t0 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 t0 = 0.15 mm to 0.4 mm depending on the application. Can be punched out and used as a base plate (blank), but the thickness is not limited to the above.

[Surface coating treatment process]
When a metal plate having no organic coating on the surface is used as the base plate, as shown in FIG. 4, in the seamless can body manufacturing method of the present embodiment, the above-mentioned first molding step and second molding step are performed. It is preferable to further have an inner surface treatment step (STEP2) in which at least the inner surface of the cup body 2 is surface-coated. Examples of such a surface coating treatment include coating a known coating film or the like used on the inner surface side of the seamless can body 1.

Further, on the outer surface side, for the purpose of ensuring the transportability and corrosion resistance after the first molding step, the portion in the range from the bottom outer peripheral portion A to the inclined portion S of the cup body 2 is centered on the lowermost curvature portion. Organic coatings 40a and 40b (see FIG. 8) can be applied.
That is, in the present embodiment, since two or more molding processes are performed in the form of at least the first molding step and the second molding step, it is assumed that the bottom of the seamless can body is rubbed between these molding steps and during subsequent transportation. NS. On the other hand, for example, by applying the above-mentioned organic coating 40 between the first molding step and the second molding step, the organic coatings 40a and 40b are formed on the provisional peripheral ground contact portion 20a'and the peripheral ground contact portion 20b, respectively. It will be formed (see FIG. 8).

FIG. 9 shows an example of a coating device capable of applying the organic coating 40 to a portion in the range from the bottom outer peripheral portion A to the inclined portion S of the cup. As shown in the figure, when the cup body 2 is horizontally moved by the transport mechanism TM, the coating film liquid LQ (the liquid that becomes the organic coating film 40) stored in the storage container SC is applied by the coating rollers R1 and R2. It can be applied to the bottom of the cup body 2. Since a rubber material having appropriate elasticity is used for the surface of the roller R2, it can be reliably applied to a portion in the range from the bottom outer portion A of the cup to the inclined portion S.
The above-mentioned coating device is an example, and a known method such as spray coating the coating liquid LQ on the bottom of the cup body 2 with a known robot handler or the like may be applied.

In addition to the surface coating treatment step as STEP 2, between the first molding step and the second molding step, the cup body 2 is appropriately known to have a cleaning step, a printing step, and a shape into a tubular body. Neck-in (mouth drawing) processing or the like may be performed within a range that does not hinder the imparting processing or the second molding step.

According to the seamless can body 1 of the present embodiment and the manufacturing method thereof described above, it is possible to realize a seamless can body having excellent pressure resistance performance, and to achieve both weight reduction and pressure resistance strength of the can bottom at a high level. It will be possible.

Experimental example

An example of an experiment carried out based on the above method is shown below with reference to FIG. However, the present invention is not limited to the following experimental examples.
First, as a metal material (precursor 3), an aluminum alloy plate (JIS H 4000 A3104-H19) having plate thicknesses of 0.200 mm, 0.205 mm, 0.215 mm, 0.225 mm, 0.240 mm, 0.245 mm, and 0.250 mm. (Material) is prepared, and the first molding step, the surface treatment step, and the second molding step are performed, and the can diameter is 211D (outer diameter φ66.0 mm) with an internal volume of 350 mL, as in Experimental Examples 1 to 19 described later. A squeezed iron can (DI can) having different specifications of the can bottom, that is, a seamless can body 1 was manufactured.

The outer surface side of the obtained various seamless cans 1 and 2 commercially available products passing through the center line of the cans using the above-mentioned shape measuring machine (manufactured by Tokyo Precision Co., Ltd., trade name; contour record, model number 1600DH). contour was measured, transferred the obtained shape data to CAD, the outer surface area a _D, the area a _B of a virtual plane the circumferential ground portion 20b and the _contour, surrounded by the virtual plane VP and the raised bottom 30 volume V _D of the _space, and (in this example aluminum alloy) metal member forming the raised bottom 30 and calculates various parameters including the volume V _M of.

Further, a pressure resistance performance test was carried out on the seamless can body 1 thus obtained. The compressive strength was determined by sealing the opening of the can with a plate with a hole and feeding pressurized water into the can through a pipe through the hole. In the pressure resistance (buckling pressure) evaluation, the pressure resistance applicable to carbonated beverages was evaluated as "◯" when it exceeded 0.686 MPa, and as "x" when it was less than this.
From intention to save material required for can manufacturing, focusing on the metal volume V _M of the raised portion as the material usage can bottom, the well below the 615 mm ³ was evaluated as "○", more of what "×" I evaluated it.

In order to evaluate the disadvantage that the volume V _D of the raised bottom 30 decreases due to the excessive volume V _D of the container, we focused on ^{the volume V D of the raised bottom 30 and set the volume V D below 17,000 mm 3} (= 17 ml). It was evaluated as "○", and more than that was evaluated as "×". The content of the seamless can body 1 in this experimental example is assumed to be 350 ml as an example, and 17 ml is about 5% of that.
If these evaluation results "pressure resistance", "material usage", and "capacity reduction" are all "○", the overall evaluation is "○", and if there is even one evaluation of "x", the overall evaluation is " × ”.
Table 1 summarizes the specifications (measured values, calculated values) and evaluation results of the seamless can body 1 of Experimental Examples 1 to 19 and two types of commercially available products.

Experimental Example 1 is given as a basic specification according to the molding method of the present invention, and has almost the same ground contact diameter and material plate thickness as a commercially available product having a can diameter of 211D (about 66 mm) currently on the market. Although 0.225 mm was extremely thin, the overall evaluation was "○". As described above, in Experimental Example 1, it is shown that both the performance and cost of the can bottom are extremely excellent.
Experimental Examples 2-5 are those that were changed to increase the height H _p of the raised portion 30 Experimental Example 1 described above. The first height Ho (see FIG. 5C) was appropriately increased in advance so that _{the inner diameter φd R} of the outermost end 20e and the innermost diameter φd _{e of the innermost end 20c shown in FIG. 10 did not change.} ..

Experimental Examples 6 to 8 are modified to reduce the material plate thickness as compared with Experimental Example 1.
Experimental Examples 9 to 11 are modified to increase the material plate thickness as compared with Experimental Example 1.
Experimental Examples 12 to 15 are modified to reduce _{the inner diameter φd R} of the outermost end 20e from Experimental Example 1. As the innermost diameter .phi.d _e does not change the height H _p and the inner end portion 20c raised bottom 30, and molded in advance respective first height Ho also reduced appropriately.

Experimental Example 16 is modified to increase _{the inner diameter φd R} of the outermost end 20e from Experimental Example 1. As the innermost .phi.d _e height H _p and the inner end portion 20c of the raised portion 30 does not change, even molded increased appropriately first height Ho in advance, respectively.
_{In Experimental Examples 17 and 18, the radius r D} of the dome spherical surface (see FIG. 10) is slightly increased to 40 mm _{in order to further increase the inner diameter φd R} of the outermost end 20e as compared with Experimental Example 16. As unchanged innermost .phi.d _e height H _p and the inner end portion 20c of the raised portion 30, also molded appropriately changed first height Ho in advance, respectively.

Experimental Example 19 is a modification in which the material plate thickness is reduced to 0.215 mm from Experimental Example 4.
Of the two types of commercial products currently on the market, those that contain carbon dioxide gas, have so-called reform molding by rolls on the bottom, and are relatively thin and lightweight. It was selected, measured and evaluated.
Evaluation results of the above Experimental Examples, any ones overall evaluation is "○", defined in Claim values are both present invention values and _(V D _/ V _M) of _(A D _/ A _B) It was within the range of the numerical value to be calculated. On the other hand what overall evaluation is "×" are all the values of _(A D _/ A _B) and _(V D _/ V _M) are both outside the range of numbers as defined in the claims of the present invention there were.

Had been performed in all Kan径66mm etc. Experimental examples shown in the _above, the values of _{_(A} D / A _B) and _{_(V} D / V _M) are both dimensionless number, withstand voltage characteristics, Similarity rules hold for cost evaluation regardless of the size of the can. That is, the present invention is not limited to the above-mentioned can diameter of 66 mm, and the numerical range specified by the present invention can be implemented in various can diameters, and even in such a case, the same action and effect as described above are obtained. It has an effect.

The embodiment described above is an example embodying 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 embodiment without departing from the above gist of the present invention.

The present invention can be applied to a container that requires excellent pressure resistance, and can be particularly used for a can body that can store liquids such as beverages and chemicals.

1 Seamless can body 2 Cup body 3 Precursor 4 Swelling part 10 Cylindrical body part 20 Can bottom part 60 Lower mold member (cup outer peripheral side holder)
70 Upper mold member (dome pushing tool)
D Cup dome part S Inclined part Hp Height of raised bottom 30 (second height)
Height of Ho bulge 4 (first height)

Claims

With a tubular body,
A peripheral grounding portion extending from the lower end of the tubular body portion and
Including a raised bottom portion extending from the circumferential ground contact portion toward the central axis side,
The outer surface area A D of the raised bottom, the area of the virtual plane of the circumferential ground portion to the contour A B, and when defined, respectively,
1.55 ≧ (A D / A B ) ≧ 1.40
Seamless cans that are characterized by satisfying the relationship of.
Volume of V D of the space surrounded by the virtual plane and the raised bottom, volume V M of the metal member forming the raised bottom, and when defined, respectively,
26.0 ≧ (V D / V M ) ≧ 22.0
The seamless can according to claim 1, which satisfies the above relationship.
A cup body in which a metal material has a tubular body portion, an outer peripheral bottom portion that continues from the lower end of the tubular body portion, and a bulging portion that bulges at a first height from the outer peripheral bottom portion toward the opening. The first molding process and
The bulging portion is pushed down so as to have a second height lower than the first height, and the circumferential grounding portion connected from the lower end of the tubular body portion and the circumferential grounding portion toward the central axis side. Including a second molding step of forming a continuous raised bottom,
The outer surface area A D of the raised bottom, the area of the virtual plane of the circumferential ground portion to the contour A B, and when defined, respectively,
1.55 ≧ (A D / A B ) ≧ 1.40
A method for manufacturing a seamless can body, which is characterized by satisfying the relationship between the two.