EP3919200A1 - Nahtloser dosenkörper und verfahren zur herstellung eines nahtlosen dosenkörpers - Google Patents

Nahtloser dosenkörper und verfahren zur herstellung eines nahtlosen dosenkörpers Download PDF

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Publication number
EP3919200A1
EP3919200A1 EP20749070.7A EP20749070A EP3919200A1 EP 3919200 A1 EP3919200 A1 EP 3919200A1 EP 20749070 A EP20749070 A EP 20749070A EP 3919200 A1 EP3919200 A1 EP 3919200A1
Authority
EP
European Patent Office
Prior art keywords
section
seamless
sheet thickness
outer circumferential
tubular body
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
EP20749070.7A
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English (en)
French (fr)
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EP3919200A4 (de
Inventor
Tomomi Kobayashi
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
Toyo Seikan Group Holdings Ltd
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Toyo Seikan Group Holdings Ltd
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from JP2019014857A external-priority patent/JP6835109B2/ja
Priority claimed from JP2019190496A external-priority patent/JP6760460B1/ja
Application filed by Toyo Seikan Group Holdings Ltd filed Critical Toyo Seikan Group Holdings Ltd
Publication of EP3919200A1 publication Critical patent/EP3919200A1/de
Publication of EP3919200A4 publication Critical patent/EP3919200A4/de
Pending legal-status Critical Current

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Classifications

    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D1/00—Containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material, by deep-drawing operations performed on sheet material
    • B65D1/12—Cans, casks, barrels, or drums
    • B65D1/14—Cans, casks, barrels, or drums characterised by shape
    • B65D1/16—Cans, casks, barrels, or drums characterised by shape of curved cross-section, e.g. cylindrical
    • B65D1/165—Cylindrical cans
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D22/00—Shaping without cutting, by stamping, spinning, or deep-drawing
    • B21D22/20—Deep-drawing
    • B21D22/30—Deep-drawing to finish articles formed by deep-drawing
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B21—MECHANICAL METAL-WORKING WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D—WORKING OR PROCESSING OF SHEET METAL OR METAL TUBES, RODS OR PROFILES WITHOUT ESSENTIALLY REMOVING MATERIAL; PUNCHING METAL
    • B21D51/00—Making hollow objects
    • B21D51/16—Making hollow objects characterised by the use of the objects
    • B21D51/26—Making hollow objects characterised by the use of the objects cans or tins; Closing same in a permanent manner
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B65—CONVEYING; PACKING; STORING; HANDLING THIN OR FILAMENTARY MATERIAL
    • B65D—CONTAINERS FOR STORAGE OR TRANSPORT OF ARTICLES OR MATERIALS, e.g. BAGS, BARRELS, BOTTLES, BOXES, CANS, CARTONS, CRATES, DRUMS, JARS, TANKS, HOPPERS, FORWARDING CONTAINERS; ACCESSORIES, CLOSURES, OR FITTINGS THEREFOR; PACKAGING ELEMENTS; PACKAGES
    • B65D1/00—Containers having bodies formed in one piece, e.g. by casting metallic material, by moulding plastics, by blowing vitreous material, by throwing ceramic material, by moulding pulped fibrous material, by deep-drawing operations performed on sheet material
    • B65D1/40—Details of walls
    • B65D1/42—Reinforcing or strengthening parts or members
    • B65D1/46—Local reinforcements, e.g. adjacent closures

Definitions

  • the present invention relates to a seamless can body and a method of manufacturing a seamless can body.
  • a seamless can body in which a can body section is molded by drawing and ironing has been known.
  • Such a seamless can body has the can body section thinned by ironing and is thus excellent in lightness in weight.
  • a processing method for forcibly performing the thinning, such as ironing it is difficult to adopt a processing method for forcibly performing the thinning, such as ironing, so that the sheet thickness of the can body bottom section is not largely varied from the raw material thickness.
  • PTL 1 and PTL 2 disclose what is called bottom reforming performed for the purpose of preventing a phenomenon (buckling) in which a dome section at the can bottom is inverted and which is generated when the internal pressure of the can exceeds a pressure resisting strength.
  • PTL 1 and PTL 2 disclose bottom reforming in which an inner circumferential wall of a grounding section of the can bottom that is located inside in a radial direction orthogonal to the can axis is pressed to thereby mold a recess.
  • the bottom reforming step presses an inner circumferential wall at the can bottom by use of a molding roller or the like, to mold a recess.
  • a molding roller or the like When pressing by use of the molding roller or the like is conducted, as described in PTL 3, there have been problems that blacking is liable to occur at the pressed part and that agglutination of a metallic material to the molding roller or the like is liable to occur.
  • the present inventor has disclosed a technology for enhancing pressure resistance of the seamless can body.
  • pressure resistance is enhanced, however, the sheet thickness distribution of each part of the can body (particularly the can bottom section) is not optimized sufficiently. Therefore, the technology does not sufficiently satisfy the demand for weight reduction of the can body.
  • PTL 5 discloses a two-piece can body characterized in that the sheet thickness of a grounding section at the can bottom is larger than the sheet thickness of the raw material that is yet to be processed.
  • a device used in the technology is complicated, and thus, there is a problem that it is difficult to realize such a two-piece can body on an industrial level or that equipment cost is raised.
  • the present inventor repeated extensive and intensive investigations in consideration of the problems exemplified above.
  • the present invention has been made which makes possible to provide, by a simple manufacturing device, a seamless can body and a method of manufacturing the seamless can body in which the sheet thickness of the raw sheet (blank) is reduced, and at the same time, pressure resistance of the can bottom is enhanced to restrain buckling, and the problems with blacking and cleaning are also solved.
  • a seamless can body having a tubular body section and a can bottom section.
  • the can bottom section includes an outer circumferential bottom section extending from a lower end of the tubular body section such as to decrease in diameter toward the inside, and an annular grounding section located further inside than the outer circumferential bottom section.
  • t1 is a sheet thickness of the outer circumferential bottom section
  • t2 is a sheet thickness of the annular grounding section
  • a seamless can body includes a tubular body section and a can bottom section including at least an outer circumferential bottom section extending from a lower end of the tubular body section through a boundary part such as to decrease in diameter toward the inside.
  • a sheet thickness of the lower end of the tubular body section is substantially equal to a sheet thickness of an intermediate part of the tubular body section in an axial direction.
  • the can bottom section further includes an inside end section 202c located further inside than the annular grounding section, and in a case where t3 is a sheet thickness of the inside end section, the relation of t3 > t1 is satisfied.
  • a sheet thickness gradually increases from the outer circumferential bottom section to the inside end section such that t3 > t2 is satisfied.
  • the can bottom section further includes a rising section 202d rising upward from the inside end section, and in a case where t4 is a sheet thickness of an upper end of the rising section, the relation of t4 > t1 is satisfied.
  • the can bottom section further includes a can dome section that is connected to the rising section and bulges to protrude upward, and a sheet thickness gradually increases from the can dome section to the inside end section such that t3 > t4 > t5 is satisfied in a case where t5 is a sheet thickness of a center of the can dome section.
  • (8) it is preferable that a ring groove in which a connection section between the rising section and the dome section protrudes toward the outside with respect to a can body axis is formed.
  • a sheet thickness of the boundary part is substantially equal to the sheet thickness of the intermediate part.
  • a method of manufacturing a seamless can body having a tubular body section and a can bottom section includes a first molding step of molding a raw metal material into a cup body including the tubular body section, a cup outer circumferential bottom section extending from a lower end of the tubular body section such as to decrease in diameter, an inclined section extending upward toward the inside from the cup outer circumferential bottom section, and a cup dome section bulging upward from an end portion of the inclined section at a first height; and a second molding step of applying a pressing force to the cup dome section toward an outside of a can by using an upper molding member while the cup outer circumferential bottom section of the cup body is brought into contact with a lower molding member, to press down the cup dome section such as to have a second height lower than the first height, and to apply compressive stresses in a meridian direction and a circumferential direction, and then pressing the inclined section into the lower molding member while a
  • the inclined section is pressed into the lower molding member, to thereby form an annular grounding section 202b located further inside than an outer circumferential bottom section, an inside end section 202c located further inside than the annular grounding section, and a rising section 202d rising upward from the inside end section and connected to a can dome section, and a ring groove in which a connection section (outermost end 201e) between the rising section 202d and the can dome section 201d protrudes toward the outside with respect to a can body axis is formed such that the inside diameter (dx) of the connection section becomes greater than the inside diameter (dy) of the inside end section 202c.
  • a method of manufacturing a seamless can body includes a first molding step of molding a raw metal material into a cup body having a tubular body section thinned by ironing, an outer circumferential bottom section extending from a lower end of the tubular body section, and a bulging section bulging from the outer circumferential bottom section toward an opening at a first height; and a second molding step of pressing down the bulging section such as to have a second height lower than the first height.
  • the lower end of the tubular body section is drawn to form the outer circumferential bottom section extending from the lower end of the tubular body section through a boundary part such as to decrease in diameter toward the inside, such that a sheet thickness of the lower end of the tubular body section becomes substantially equal to a sheet thickness of an intermediate part of the tubular body section in an axial direction.
  • a can bottom higher in pressure resistance than the can bottom obtained by conventional bottom reforming can be obtained even in the case where the sheet thickness of the raw sheet (blank) is reduced. Therefore, a seamless can body can be manufactured by use of a raw sheet (blank) thinner than that used in the prior art, and the amount of metallic material to be used can be reduced, which is advantageous on a cost basis. Further, weight reduction in the seamless can body leads to reductions in recycle cost, transportation cost, and the like.
  • a seamless can body of the present invention it is possible to enhance the pressure resistance of the can bottom and restrain buckling by a simple manufacturing device even in the case where the sheet thickness of the raw sheet (blank) is reduced. At the same time, the problem with blacking as encountered in bottom reforming can be solved. Further, since the conventional bottom reforming step and the step of cleaning the lubricant after the bottom reforming are not needed, there are large merits on a cost basis and an environmental basis.
  • a seamless can body and a method of manufacturing the seamless can body according to the present invention will specifically be described below with referring to the drawings, as needed. Note that the following embodiments illustrate an example of the present invention to explain the details thereof and do not limit the present invention intentionally.
  • a seamless can body 1A is a seamless can body having a tubular body section 10 and a can bottom section 20.
  • the can bottom section 20 preferably includes a can bottom central part 201 which does not make contact with a horizontal surface when the seamless can body is mounted on the horizontal surface, and a foot part 202 located on the outside of the can bottom central part 201.
  • the can bottom central part 201 of the seamless can body 1A may have a horizontal shape or may have a dome shape bulging toward the inner surface side of the can (bulging such as to protrude upward) as depicted in FIG. 1(a) .
  • the foot part 202 of the can bottom section 20 is defined as a part extending from a lower end 10e of the tubular body section 10 and then extending along a can body axis RA direction up to an outermost end 201e of the can bottom central part 201.
  • the outermost end 201e of the can bottom central part 201 is a part where, in the case where the can bottom central part 201 is in the dome shape, the diameter of the dome is maximum.
  • the foot part 202 has an annular grounding section 202b which is located in the lowest part in a Z axis direction. Specifically, it can be said that the annular grounding section 202b is a part that makes contact with a horizontal surface in the case where the seamless can body 1A according to the present embodiment is mounted on the horizontal surface.
  • a part ranging from the lower end 10e of the tubular body section 10 to the annular grounding section 202b is defined as an outer circumferential bottom section 202a.
  • the foot part 202 includes the outer circumferential bottom section 202a extending from the lower end 10e of the tubular body section 10 such as to decrease in diameter toward the inside and the annular grounding section 202b located further inside than the outer circumferential bottom section 202a.
  • the outer circumferential bottom section 202a of the seamless can body 1A has a ring shape and is located to the lower end 10e of the tubular body section 10 further outside than the annular grounding section 202b.
  • the width, area, and the like of the ring of the outer circumferential bottom section 202a are not particularly limited, and known shapes are applicable to the inclination angle and curved state of the ring.
  • the outer circumferential bottom section 202a may be rectilinear in section, may be in an arcuate shape curved toward the inside of the can body, or may be in an arcuate shape curved toward the outside.
  • the outer circumferential bottom section 202a may have a part curved toward the inside and the remaining part curved toward the outside, and these parts may be connected consecutively.
  • the outer circumferential bottom section 202a has an inflection point IP in its sectional view, from the viewpoint that the seamless can body 1A can easily be mounted on a lid of a can of the same kind.
  • the seamless can body 1A further includes an inside end section 202c located further inside than the annular grounding section 202b.
  • the inside end section 202c is defined as a part of the abovementioned foot part 202 which is the closest to the can body axis RA side in a sectional view.
  • the seamless can body 1A further includes a rising section 202d extending upward (in a + direction of the Z axis) from the inside end section 202c.
  • the rising section 202d is defined as a part ranging from the inside end section 202c to the outermost end 201e in the can bottom central part 201 direction.
  • the seamless can body 1A according to the present embodiment is characterized in that the relation of "t2 > t1" is satisfied in the case where t1 is the sheet thickness of the outer circumferential bottom section 202a and t2 is the sheet thickness of the annular grounding section 202b.
  • t1 is the sheet thickness of the outer circumferential bottom section 202a
  • t2 is the sheet thickness of the annular grounding section 202b.
  • the sheet thickness (t1) of the outer circumferential bottom section 202a is the sheet thickness at an intermediate point of the length (the length along the shape) from the lower end 10e to the annular grounding section 202b.
  • the relation of "t3 > t1" is satisfied in the case where t3 is the sheet thickness of the inside end section 202c.
  • t3 is the sheet thickness of the inside end section 202c.
  • the liquid accommodated in the seamless can body is beer or a carbonated drink
  • an internal pressure is always exerted on the can bottom.
  • the internal pressure of the can exceeds the pressure resisting strength of the can bottom, and a phenomenon (buckling) in which the dome section of the can bottom is inverted is generated.
  • the pressure resisting strength of the can bottom should be increased.
  • a method of thickening the sheet thickness of the can bottom part is contemplated.
  • the present inventor made extensive and intensive investigations in order to realize a seamless can body that simultaneously satisfies the demands for weight reduction of cans and desired pressure resisting strength of the can bottom.
  • the present inventor has conceived the present invention which achieves, while setting the sheet thickness of the raw sheet (blank) to be comparable to or smaller than that in the prior art, enhancement of pressure resisting strength of the can bottom by thickening only the part of the can bottom that is liable to contribute to enhancement of pressure resisting strength.
  • the sheet thickness of the can body section which is comparable to or smaller than that in the prior art can be provided by rigorous drawing and ironing similar to those in the prior art. Therefore, it can be said that demands for weight reduction and enhancement of pressure resisting strength of the can bottom can both be satisfied at a higher dimension.
  • the foot part 202 of the can bottom section 20 is connected to the can bottom central part 201 (can dome section 201d) at the part of the outermost end 201e, from the inside end section 202c through the rising section 202d.
  • the rising section 202d may be a straight line or a curved line in section that extends in a vertical direction (+ direction of the Z axis) from the inside end section 202c.
  • the rising section 202d is connected to the can bottom central part 201 (can dome section 201d) such that an inside diameter (dx) of the abovementioned outermost end 201e is greater than an inside diameter (dy) of the inside end section 202c.
  • the shape in a sectional view is a substantially U-shape ( ⁇ or ⁇ ) .
  • a ring groove in which the outermost end 201e protrudes toward the outside with respect to the can body axis RA is preferably provided between the inside end section 202c and the can dome section 201d such as to extend toward the + direction of the Z axis.
  • the pressure resistance of the seamless can body 1A according to the present embodiment can be enhanced.
  • the outer circumferential bottom section 202a preferably has the inflection point IP in its sectional view as described above.
  • This inflection point IP may be located further in the + direction of the Z axis than the outermost end 201e as depicted in FIG. 2 , or may be located in the - direction of the Z axis.
  • t4 is the sheet thickness at a part of the outermost end 201e that connects the rising section 202d and the can bottom central part 201.
  • the seamless can body 1A according to the present embodiment further includes the can dome section 201d that is connected to the rising section 202d and bulges to protrude upward, at the can bottom section 20.
  • the shape of the can bottom central part 201 is preferably a dome shape as depicted in FIG. 1(a) .
  • t5 is the sheet thickness at the center of the can dome section 201d
  • the sheet thickness t5 satisfies the following relation. t3 > t4 > t5
  • the sheet thickness gradually increases.
  • the sheet thickness (t5) at the center of the can dome section 201d is equal to or less than the sheet thickness (tz) of the raw sheet (blank) (t5 ⁇ tz).
  • the sheet thicknesses satisfy the relation of "t3 > t2 > t1.” In other words, it is preferable that the sheet thickness gradually increases in the order of the outer circumferential bottom section 202a, the annular grounding section 202b, and the inside end section 202c.
  • the pressure resistance can be enhanced while an increase in weight of the can is suppressed, and thus, this is preferable.
  • the thicknesses of t2 and t3 may be the same as depicted in FIG. 3(b) , or the thickness of t2 may be the largest as depicted in FIG. 3(c) .
  • the sheet thickness tz of the raw sheet (blank) is only required to have a sheet thickness ordinarily adopted in the case of manufacturing a seamless can body, and a metal sheet with the thickness tz of approximately 0.15 to 0.4 mm is blanked to be used as a raw sheet (blank), but this thickness is not limitative.
  • the sheet thickness of the can bottom section 20 has the abovementioned relation.
  • the average sheet thickness of the can bottom section 20, particularly, the foot part 202 is thicker than the can bottom central part 201.
  • the thickness of the can dome section 201d is smaller than the thickness of the outer circumferential bottom section 202a. In other words, it is preferable that "t5 ⁇ t1.”
  • the buckling pressure is a numerical value indicating the pressure resistance.
  • the buckling pressure is a peak value of pressure until occurrence of the phenomenon in which the dome section protruding toward the inside of the can bottom is deformed to be inverted to the outside by the internal pressure.
  • the dome section having a substantially spherical shape starts receiving the internal pressure
  • the dome section itself is not deformed immediately, but the product of the projection area of the dome section and the internal pressure becomes a force for pushing out the dome section to the outside of the can, thereby acting on the annular grounding section 202b, the inside end section 202c, and the rising section 202d to exert a load and deform them.
  • the outer circumference of the dome section is supported by the narrow region ranging from the annular grounding section 202b to the rising section 202d.
  • a second height Hp of the can dome section 201d of the seamless can body 1A is not particularly limited and can be a height comparable to that of a known seamless can body having a dome section.
  • the kind of the raw metal material used for the seamless can body 1A is not particularly limited.
  • known metal sheets ordinarily used for seamless can bodies such as an aluminum alloy sheet and a surface-treated steel sheet, can be used.
  • the metal sheet may have a known film laminated thereon or may be subjected to surface-treatment such as organic resin coating or chemical conversion treatment, as required.
  • the seamless can body 1A according to the present embodiment is subjected to known necking, flange forming, or screw forming, and after beer, a carbonated drink, or the like is filled in the seamless can body 1A as a content, a lid is attached to an opening by a known method.
  • the method of manufacturing a seamless can body is a method of manufacturing the seamless can body 1A having the tubular body section 10 and the can bottom section 20 as depicted in FIG. 1(a) and is characterized by including at least a first molding step and a second molding step which will be described in detail below.
  • a method of molding the tubular body section 10 for example, a known method such as a method described in PTL 4 can be adopted.
  • a method of molding the can bottom section 20 is particularly characterized by including at least the first molding step and the second molding step described in detail below.
  • the can body section is formed by a known method to prepare a precursor 3 having a cup shape.
  • the raw metal material (precursor 3) may have a cup shape which does not have a dome and which is obtained by known drawing and ironing or the like.
  • the raw metal material (precursor 3) may have a cup shape having a dome, insofar as the first molding step and the second molding step described below can be realized.
  • the seamless can body 1A according to the present embodiment can be obtained.
  • the raw metal material (precursor 3) is molded into a cup body 2 having the tubular body section 10, a cup outer circumferential bottom section A extending from the lower end 10e of the tubular body section 10 such as to decrease in diameter, an inclined section S extending upward toward the inside from the cup outer circumferential bottom section A, and a cup dome section D bulging upward from an end portion Se of the inclined section S at a first height Ho.
  • the end portion Se of the inclined section S can be said to be a connection point with the cup dome section D.
  • the first molding step depicted in FIG. 4 can be performed on the precursor 3 including the tubular body section 10 molded by a known pressing step or the like, either as separate steps by use of an upper mold and a lower mold or a step performed at a stroke final stage subsequent to an ironing step.
  • the first molding step is carried out by using a tubular punch 401 that is located in the precursor 3 having the cup shape and that supports the precursor 3, a hold down ring 501 that supports the outer circumferential bottom section of the precursor 3 in cooperation with the punch 401, and a doming die 502.
  • the outer circumferential bottom section of the precursor 3 is held by a circumferential wall part 402 (taper section) of the punch 401 and a tapered support section 503 of the hold down ring 501, and the punch 401 and the doming die 502 are driven such as to engage with each other and are relatively moved close to each other, so that the cup body 2 having the cup dome section D at the bottom thereof at the first height Ho can be obtained.
  • a circumferential wall part 402 (taper section) of the punch 401 and a tapered support section 503 of the hold down ring 501 the punch 401 and the doming die 502 are driven such as to engage with each other and are relatively moved close to each other, so that the cup body 2 having the cup dome section D at the bottom thereof at the first height Ho can be obtained.
  • the shape of the cup body 2 obtained in the first molding step will be described. Specifically, the inclined section S of the cup body 2 extends upward toward the inside from the cup outer circumferential bottom section A.
  • the inclined section S of the cup body 2 includes a curved line part and a straight line part provided between the lowest part of the cup body 2 in the Z-axis direction and the connection point (end section Se ) with the cup dome section D.
  • the inclined section S is preferably inclined at a predetermined angle ⁇ 1 , without being perpendicular.
  • the angle ⁇ 1 formed between the inclined section S and the Z axis is 5° to 30° from the viewpoint of favorably controlling the sheet thicknesses of the respective parts in the second molding step described below.
  • the angle ⁇ 1 between the inclined section S and the Z axis is 10° to 30° since spray coating is easily performed in the case of forming a coating film on an inner surface by a spray coating method after the first molding step.
  • the first height Ho of the cup dome section D of the cup body 2 is greater than a second height Hp of a can dome section 201d of the seamless can body 1A obtained in the second molding step described later.
  • the reason for this is to apply a compressive stress to the inclined section S while the cup dome section D of the cup body 2 is pressed down in the second molding section described later.
  • the first height Ho of the cup dome section D of the cup body 2 is preliminarily set to be large to finally obtain a preferable second height Hp of the can dome section 201d of the seamless can body 1A.
  • the second molding step is carried out as follows.
  • a known cleaning step, surface-treatment step, printing step, coating step, or shaping step for the tubular body section, or necking-in (decreasing diameter) in such a range as not to hamper the second molding step may be carried out on the cup body 2, as required, between the first molding step and the second molding step.
  • an outer surface coating can be applied to the part ranging from the cup outer circumferential bottom section A to the inclined section S, with a lowest end curvature section of the cup body 2 set as a center.
  • processing is performed on the cup body 2 by using a mold different from a mold used in the abovementioned first molding step, to mold the seamless can body 1A.
  • a pressing force is applied to the cup dome section D of the cup body 2 in the outside direction of the can (-Z axis direction) by use of a dome pressing-down tool 70 as an upper molding member.
  • a pressing force may be applied in the +Z axis direction by use of the lower molding member.
  • the cup outer circumferential bottom section A of the cup body 2 is mounted on the cup outer circumferential side holder 60.
  • the dome pressing-down tool 70 is relatively lowered, and a support section 701 of the dome pressing-down tool 70 makes contact with the cup dome section D.
  • the cup outer circumferential side holder 60 has a tapered surface 601 and a groove 602. With the dome pressing-down tool 70 further pressed down after the cup outer circumferential bottom section A of the cup body 2 makes contact with the tapered surface 601, the metal of the inclined section S of the cup body 2 is guided into the groove 602 while receiving a compressive stress and is pushed into the groove 602.
  • the cup dome section D is pressed down such that the second height Hp is lower than the first height Ho.
  • the upper molding member dome pressing-down tool
  • the lower molding member cup outer circumferential side holder
  • FIG. 6 is a schematic view depicting a compressive stress applied when the inclined section S is formed at the rising section 202d in the present embodiment.
  • the compressive stress ⁇ ⁇ produced in the meridian direction by the pressing force of the dome pressing-down tool 70 and the compressive stress ⁇ ⁇ produced in the circumferential direction due to movement toward the radial-directionally inner side to follow the lower molding member are simultaneously applied to the inclined section S, and the thickness of the raw metal material of the inclined section S is increased (arrow direction ⁇ ⁇ in FIG. 6 ) .
  • the seamless can body 1A is obtained after the second molding step is conducted.
  • the seamless can body 1A obtained after the second molding step is preferably the abovementioned seamless can body 1A according to the present embodiment.
  • the seamless can body 1A obtained after the second molding step preferably has the outer circumferential bottom section 202a and the annular grounding section 202b as depicted in FIG. 1 and satisfies the relation of "t2 > t1" in the case where t1 is the sheet thickness of the outer circumferential bottom section 202a and where t2 is the sheet thickness of the annular grounding section 202b.
  • the second molding step has the following characteristics.
  • the inclined section S is formed into the annular grounding section 202b located further inside than the outer circumferential bottom section 202a, the inside end section 202c located further inside than the annular grounding section 202b, and the rising section 202d rising upward from the inside end section 202c and connected to the can dome section 201d.
  • the ring groove in which the outermost end 201e protrudes toward the outside with respect to the can body axis RA is formed such that the inside diameter (dx) of the connection point (outermost end 201e) between the rising section 202d and the can dome section 201d of the seamless can body 1A is greater than the inside diameter (dy) of the inside end section 202c.
  • the sheet thickness of the ring groove part does not become thin and tends to be thick, so that a deep groove can be reasonably formed.
  • the shape and length of an upper part of the cup outer circumferential bottom section A of the cup body 2 do not change.
  • the lowest point in the Z-axis direction of a surface where the cup outer circumferential bottom section A of the cup body 2 and the tapered surface 601 of the cup outer circumferential side holder 60 make contact is set to a point T.
  • the position of the point T does not change according to lowering of the dome pressing-down tool 70 and pressing-down of the cup dome section D. (see FIG. 5 )
  • the part of the inclined section S of the cup body 2 is formed into a part of the outer circumferential bottom section 202a, the annular grounding section 202b, the inside end section 202c, and the rising section 202d of the seamless can body 1A.
  • the whole inclined section S of the cup body 2 is finally put into the groove 602 of the cup outer circumferential side holder 60.
  • the abovementioned point T becomes the inflection point IP in the seamless can body 1A. Because of a compressive stress applied in the second molding step, the metal length is shortened as follows.
  • the metal length from the inflection point IP to the outermost end 201e in FIG. 5(f) is shortened to 0.85 to 0.99 times the metal length from the point T to the end portion Se in FIG. 5(b) .
  • the thickness of the raw metal material of the part is increased in the second molding step such that the part most increased in thickness is increased to 1.1 to 1.3 times the raw sheet thickness (t0) .
  • a drawn and ironed can (DI can) with an internal volume of 350 mL was manufactured by the following method.
  • an aluminum alloy sheet (JIS H 4000 A3104-H19 material, 0.28 mm) was prepared as a raw sheet.
  • a predetermined amount of a known cupping oil was applied to both sides of the aluminum alloy sheet, as a lubricant at the time of drawing.
  • the resultant sheet was drawn to be a drawn cup (not illustrated) with a diameter of 90 mm.
  • the drawn cup thus obtained was conveyed to a body maker (can body manufacturing machine) and was re-drawn into a shape with a diameter of 66 mm. Then, by using a coolant, the drawn cup was subjected to ironing to obtain a drawn and ironed precursor 3 with a shape of 66 mm in diameter, 130 mm in height, and 0.105 mm in side wall minimum thickness.
  • the precursor 3 obtained as above was subjected to the first molding step and the second molding step as follows.
  • the first molding step was conducted at the stroke final stage of the step subsequent to the ironing by the body maker, and a cup body 2 having a cup outer circumferential bottom section A and an inclined section S was obtained by use of the punch 401, the hold down ring 501, and the doming die 502 depicted in FIG. 4 .
  • the lengths and sheet thicknesses of the cup outer circumferential bottom section A and the inclined section S in this instance are as set forth in Table 1.
  • the sheet thicknesses t1 to t5 of the respective parts were measured. Note that the position of each of the parts at t1 to t5 is as described in the above embodiment and FIG. 2 .
  • the method of measuring the sheet thickness is as follows. Specifically, the molded seamless can body 1A was embedded in an epoxy resin and was then cut together with the epoxy resin along a longitudinal axis (Z axis) of the seamless can body 1A. After a central section was exposed by cutting and careful polishing, the thicknesses t1 to t5 of the respective parts were measured with a measuring microscope. The sheet thicknesses of the parts are set forth in Table 1.
  • the molding of the can bottom was conducted in one step according to a known can bottom molding method by use of a known can bottom molding mold. Except this, the operation of a comparative example 1 was conducted similarly to the example 1.
  • FIG. 7 a partial enlarged view of the can bottom of the seamless can body used in the comparative example 1 is depicted in FIG. 7 .
  • the seamless can body obtained in the comparative example 1 was subjected to bottom reforming. Specifically, an inner circumferential wall of the grounding section of the can bottom that was located inside in a radial direction orthogonal to the can body axis was pressed by a rotating roller, to mold a recess in an annular shape. Except this, the operation of a comparative example 2 was conducted similarly to the comparative example 1.
  • the sheet thicknesses and the like of the parts of the seamless can body thus obtained are set forth in Table 1.
  • the surface condition of the molded can body section has not been aligned in the axial direction, and high metallic luster could not be obtained particularly in the vicinity of the lower end of the can body section or at a reduced diameter part (outer circumferential bottom section) provided between the can body section and the can bottom section.
  • FIG. 14(a) schematically illustrate a partial state of a can body section and a tip end part of an ironing punch immediately after completion of ironing.
  • a cylindrical section of the punch has, near the tip end thereof, a tapered shape ranging from a point A to a point B.
  • This tapered shape is provided for ensuring gradual rising of the ironing ratio at the time of starting ironing. Therefore, the can body part corresponding to the tapered part is a region having a wedge-shaped sheet thickness distribution. Note that, as depicted in FIG.
  • this region may also be referred to as a "body wall step (BWS)."
  • BWS body wall step
  • BWR body wall radius
  • the glossiness of the ironed surface at the point B located at the lower end of the BWS is substantially comparable to the glossiness of the original raw material surface, the glossiness of the ironed surface increases toward the point A located at the upper end of the BWS, and a maximum glossiness is exhibited at and beyond the point A.
  • FIG. 14(b) is a diagram depicting a partial state of the can body section and the tip end part of the ironing punch at the time point when the dome section is formed in the can bottom by relatively moving the doming die into the inside of the tip end of the ironing punch after completion of ironing.
  • a bottom surface part of the can bottom is drawn into the inside to become a dome section, so that a part located at the point A in FIG. 14(a) is deviated to the point A', and a part located at the point B is deviated to a point B'.
  • the moving amount (deviation amount) of each of these points is, for example, approximately 2 to 5 mm.
  • a seamless can body 1B is a seamless can body that includes a tubular body section 10 and a can bottom section 20 including at least an outer circumferential bottom section 20a extending from a lower end of the tubular body section 10 through a boundary part BP such as to decrease in diameter toward the inside.
  • a part on the upper side beyond the tubular body section 10 in FIG. 8 has a neck flange shape as an example, the structure of a known seamless can body having an opening 10a is also applicable to the part on the upper side beyond the tubular body section 10.
  • the lower end 10e of the tubular body section 10 can be defined as a part which is located substantially at the lower end of the cylindrical surface and as a lower end of a region in which curved surface printing can be performed by, for example, a known dry offset system in the case where printing is applied to the outer surface of the seamless can body.
  • the tubular body section 10 is a part constituting a side surface of the seamless can body 1B and is formed by drawing and ironing a known metal sheet of aluminum, steel, or the like which will be described later.
  • the tubular body section 10 has an appropriate thickness depending on the use and has, for example, a thickness of approximately 0.07 to 0.40 mm.
  • the tubular body section 10 is provided between the lower end 10e, which is described later, as a lower end part and the boundary with a neck shoulder (the part decreased in diameter toward the upper side in the axial direction) as an upper end part, as depicted in FIG. 8 .
  • the can bottom section 20 includes at least the outer circumferential bottom section 20a extending from the abovementioned lower end 10e of the tubular body section 10 such as to decrease in diameter toward the inside, as depicted in FIG. 8 , and a bulging section 20b bulging from the outer circumferential bottom section 20a toward the opening 10a.
  • the outer circumferential bottom section 20a and the bulging section 20b in the present embodiment are defined as different sections with an annular grounding section 20c as a boundary.
  • the annular grounding section 20c is a part that, when the seamless can body 1B is mounted on a flat surface such as a table, grounds on the surface. Therefore, the outer circumferential bottom section 20a, the annular grounding section 20c, and the bulging section 20b in the present embodiment can be said to correspond to the foot part 202 and the can bottom central part 201 in the first embodiment described above. In this instance, particularly the annular grounding section 20c in the present embodiment corresponds to the annular grounding section 202b in the first embodiment.
  • the boundary part BP in the present embodiment can be defined as a boundary with a region concerning the external appearance on the can bottom side (that is, a region which can normally be observed from the outside of the can), defined as a part extending from the lower end 10e of the tubular body section 10 to the outer circumferential bottom section 20a through inflection as depicted in FIG. 17 , and defined as a point where the angle ⁇ formed between a tangential line of the outer surface at the boundary part BP and a grounding surface P is 45°.
  • the reason why the point where the angle ⁇ is 45° is defined as the boundary part BP in the present embodiment is as follows. Specifically, at a position where the ⁇ is less than 45°, the normal line to the outer surface directs excessively downward. Then, for example, in a state in which the can to which the present invention is applied is placed normally (upright) on a showcase or the like, the reflected light is less likely to enter the visual field, and therefore, it is difficult to exhibit the excellent luster property of the can outer surface which is the gist of the present invention.
  • a part on the lower end side of the tubular body section 10 including the lower end 10e of the tubular body section 10 having undergone ironing is drawn into the side of the outer circumferential bottom section 20a, and therefore, a part of the outer circumferential bottom section 20a beyond the boundary part BP and at least in the vicinity of the boundary part BP includes a metal sheet having undergone ironing.
  • the sheet thickness t0 at at least the boundary part BP is substantially equal to the sheet thickness twc (see FIG. 8 ) at an intermediate part of the tubular body section 10.
  • the tubular body section 10 of the present embodiment has a high glossiness and can exhibit uniform image clarity from the upper end to the lower end in regard of the axial direction (Z direction in FIG. 8 ) and further up to the position of the boundary part BP, as compared to the conventional structure.
  • the ironing ratio required for the ironed tubular body section 10 to exhibit a high glossiness varies depending on the characteristics of the raw material and processing conditions; as a non-limitative example, a total ironing ratio is preferably at least equal to or more than 60%.
  • the relation of t WC ⁇ t WL ⁇ 1.09 ⁇ t WC is satisfied, and more preferably the relation of t WC ⁇ t WL ⁇ 1.05 ⁇ t WC is satisfied, in the case where t WL is the sheet thickness in the vicinity of the boundary part BP of the tubular body section 10 (for example, the lower end of the tubular body section 10) and where twc is the sheet thickness of an intermediate part of the tubular body section 10 in the axial direction (Z direction), as depicted in FIG. 8 .
  • the intermediate part of the tubular body section 10 in the axial direction in the present embodiment may not necessarily be strictly the sheet thickness at a midpoint in the axial direction and can be defined as inclusive of the vicinity of the midpoint.
  • twc is the sheet thickness at an intermediate part of the tubular body section 10 in the axial direction as depicted in FIG. 8 . If t0 is less than twc, there is a possibility that axial load strength at this part may be lowered, and if t0 is equal to or more than 1.09 times twc, the glossiness at a lower end part of the tubular body section is lowered, and thus, it becomes difficult to obtain the effects of the present invention.
  • the ironed metal sheet extends beyond the boundary part BP to reach at least a part of the outer circumferential bottom section 20a, it is desirable that the 60 degrees specular glossiness from the lower end 10e of the tubular body section 10 to the vicinity of the boundary part BP is equal to or more than 300%. If the 60 degrees specular glossiness in the vicinity of the boundary part BP is less than 300%, surface roughness, dullness, or the like is noticeable on an external appearance basis at the relevant part, and therefore, appeal as a product is lowered.
  • specular glossiness in the present embodiment is measured according to the measuring method defined in JIS Z 8741-1997.
  • the kind of the raw metal material used for the seamless can body 1B is not particularly limited.
  • known metal sheets ordinarily used for seamless can bodies such as an aluminum alloy sheet or a steel sheet (for example, tinplate or the like), can be used.
  • the metal sheet may have a known film laminated on the inner surface side thereof or may be subjected to surface-treatment such as organic resin coating or chemical conversion treatment, as required.
  • the seamless can body 1B has a lid attached to the opening 10a by a known method after the seamless can body 1B is subjected to, for example, known flange processing, necking, screw processing, or the like, and beer, a carbonated drink, coffee, juice, liquid food, or the like is accommodated in the seamless can body 1B.
  • the method of manufacturing the seamless can body 1B according to the present embodiment is a method of manufacturing a seamless can body having the tubular body section 10 and the can bottom section 20 depicted in FIG. 8 and is characterized by including a first molding step and a second molding step which will be described in detail below.
  • a raw metal material (precursor 3) is molded into a cup body 2 including the tubular body section 10, an inclined section S extending upward toward the inside from a boundary part BP provided at the lower end of the tubular body section 10, and a cup dome section D bulging upward from an end portion Se of the inclined section S at a first height Ho.
  • the end portion Se of the inclined section S can be said to be a connection point with the cup dome section D.
  • the first molding step of the present embodiment is performed, by use of an upper mold and a lower mold, on a precursor 3 including the tubular body section 10 thinned through ironing and molded by a known pressing step or the like.
  • the first molding step of the present embodiment can be conducted at a final end position (the vicinity of a bottom dead center) of a punch stroke of a molding machine for ironing or can be performed in a machine different from the machine used for ironing.
  • the first molding step is carried out by a tubular punch 401 that is located in the precursor 3 having a cup shape and supports the precursor 3, and a doming die 502 that supports an outer circumferential bottom section of the precursor 3 by cooperating with the punch 401.
  • a lower end of the punch 401 is recessed toward the upper side so as to correspond to the doming die 502, and a circumferential wall part 402 is formed along the circumferential direction.
  • this shape is not limitative.
  • a combined shape of a plurality of arcs and tapered surfaces as depicted in FIG. 15 or FIG. 16 may be adopted.
  • the precursor 3 when the precursor 3 is pressed such as to be interposed between the punch 401 and the doming die 502, a bottom surface of the precursor 3 bulges toward the opening by the doming die 502, and a lower end circumferential edge comes into a state of being pulled by the circumferential wall part 402.
  • the outer circumference of the precursor 3 is supported by the circumferential wall part 402 of the punch 401, and the punch 401 and the doming die 502 are driven such as to engage with each other, so that the cup body 2 having the cup dome section D with a first height Ho at the bottom thereof can be obtained.
  • a wrinkle pressing member 80 (also referred to as a hold down ring) exemplified in FIG. 16 may be disposed if necessary, and the molding may be conducted by applying a wrinkle pressing force by the circumferential wall part 402 and the wrinkle pressing member 80.
  • the first height Ho of the cup dome section is higher than the dome height in the conventional structure, and therefore, the amount by which the tubular body section 10 is drawn into the side of the outer circumferential bottom section 20a is also increased in association with the first height Ho.
  • the site originally constituting the lower end of the tubular body section 10 at the time of ironing is drawn into the side of the outer circumferential bottom section 20a beyond the boundary part BP provided between the tubular body section 10 and the outer circumferential bottom section 20a (more specifically, the point A and the point B located in the tubular body section in the example depicted in FIG. 11 are drawn into the side beyond the boundary part BP).
  • the lower end 10e of the tubular body section 10 is drawn to form a part of the outer circumferential bottom section 20a extending from the lower end 10e of the tubular body section 10 such as to decrease in diameter (substantially the part is still in the state of a curved surface in the vicinity of the boundary part BP and is referred to as a first outer circumferential bottom section 20a').
  • the inclined section S of the cup body 2 extends upward toward the inside from the first outer circumferential bottom section 20a'.
  • the inclined section S of the cup body 2 includes a curved line part and a straight line part interposed between the lower most part of the cup body 2 in the Z-axis direction and the connection point (end portion Se) with the cup dome section D.
  • the cup body 2 of the present embodiment includes the tubular body section 10 and the bulging section formed at a bottom surface of the tubular body section 10.
  • the shape of the cup dome section D is an example, and the top of the dome may have, for example, a horizontal surface shape instead of a curved surface shape.
  • the first height Ho of the cup dome section D of the cup body 2 is preferably greater than a second height Hp of the can dome section 201d in the seamless can body 1B obtained in the second molding step.
  • a compressive stress to the inclined section S while the cup dome section D of the cup body 2 is pressed down in the second molding step described later.
  • the first height Ho of the cup dome section D of the cup body 2 is preliminarily set to be large to finally obtain a favorable second height Hp of the can dome section 201d of the seamless can body 1B.
  • the bulging section bulging at the first height Ho is first formed such as to extend from the first outer circumferential bottom section 20a' in the vicinity of the boundary part BP toward the opening 10a. Then, in the second molding section described later, the bulging section is pressed down such as to have a second height lower than the first height Ho.
  • the second molding step is conducted as follows.
  • a known cleaning step, surface-treatment step, printing step, coating step, or shaping step for the tubular body section, or necking-in (squeezing) in such a range as not to hamper the second molding step may be carried out on the cup body 2, as required, between the first molding step and the second molding step.
  • an outer surface coating can be applied to the part ranging from the grounding section at the lowermost end of the cup body 2 to the inclined section S.
  • processing is performed on the cup body 2 by using a mold different from a mold used in the abovementioned first molding step, to mold the seamless can body 1B.
  • a pressing force is applied to the cup dome section D of the cup body 2 in the can outside direction (-Z axis direction) by use of the upper molding member.
  • the vicinity of the boundary part BP of the cup body 2 is mounted on a cup outer circumferential side holder 60.
  • a dome pressing-down tool 70 is relatively lowered, so that a support section 701 of the dome pressing-down tool 70 is brought into contact with the cup dome section D, as depicted in FIG. 12(b) .
  • the shape of the support section 701 is substantially coincident with the shape of the cup dome section D in FIG. 12
  • the shape may not necessarily be coincident.
  • a difference in curvature may be provided such that a high pressure is exerted on an outer circumferential part of the cup dome section D.
  • the cup outer circumferential side holder 60 has a tapered surface 601 and a groove 602. After the boundary part BP and the first outer circumferential bottom section 20a' of the cup body 2 make contact with the tapered surface 601, the dome pressing-down tool 70 is further lowered. In such a manner, as depicted in FIG. 12(c) , the metal of the inclined section S of the cup body 2 is molded such as to follow the tapered surface 601 while receiving a compressive stress.
  • the dome pressing-down tool 70 is further pressed down, so that the remaining part (a part of the metal other than the part corresponding to the tapered surface 601) of the inclined section S of the cup body 2 is guided into the groove 602.
  • the cup dome section D is pressed down such as to have a second height Hp lower than the first height Ho.
  • a compressive stress ⁇ ⁇ in the meridian direction and a compressive stress ⁇ ⁇ in the circumferential direction are applied to the inclined section S by use of the upper molding member (dome pressing-down tool) and the lower molding member (cup outer circumferential side holder). (see FIG. 6 )
  • the metal corresponding to the tapered surface 601 of the cup body 2 constitutes the outer circumferential bottom section 20a, and the metal guided into the groove 602 constitutes the abovementioned annular grounding section 20c. Further, the part on the upper side from the annular grounding section 20c constitutes the bulging section 20b. (see FIG. 12(e) )
  • the can bottom section 20 of the seamless can body 1B is obtained through the second molding step.
  • the seamless can body 1B molded by the manufacturing method according to the present embodiment described above has the tubular body section 10 serving as the can side surface and having a substantially uniform surface condition from the upper end to the lower end in the axial direction, and can thus exhibit excellent appearance and image clarity.
  • the second embodiment described above can be said to be substantially common with the first embodiment except for the can bottom section (mainly the shape of the dome section at the can bottom). Therefore, it is needless to say that the technical thought concerning the relation of the sheet thicknesses in the present embodiment and the technical thought concerning the metallic luster at the can body section and can bottom section are also applicable to the first embodiment similarly to the second embodiment, unless contradiction is generated.
  • the seamless can body 1B molded by the manufacturing method according to the present embodiment by incorporating therein the characteristics of the abovementioned first embodiment (the inside end section 202c, the rising section 202d, the outermost end 201e, and the can dome section 201d), can further exhibit effects similar to those of the first embodiment.
  • a seamless can body capable of imparting excellent image clarity to the drawn and ironed can body section while imparting high pressure resistance and a manufacturing method of the seamless can body can be realized.
  • the characteristic that the sheet thickness t0 ⁇ the sheet thickness t1 the characteristic that t WC ⁇ t WL ⁇ 1.09 ⁇ t WC indicated in the second embodiment, the characteristic that t WC ⁇ t0 ⁇ 1.09 ⁇ t WC , and the characteristic that the 60 degrees specular glossiness from the lower end 10e of the tubular body section 10 to the vicinity of the boundary part BP is equal to or more than 300%.
  • the seamless can body according to the present invention can have both the characteristics of the first embodiment and the second embodiment mentioned above, the tubular body section 10 serving as the can side surface has a substantially uniform surface condition from the upper end to the lower end in the axial direction thereof and exhibits excellent appearance and image clarity, and simultaneously, excellent pressure resistance can be secured at the can bottom section.
  • the seamless can body 1B described in the second embodiment is advantageous over the conventional structure at least in glossiness.
  • FIG. 14(a) depicts, on an extraction basis, the structure in the vicinity of the lower end of the can body section of a seamless can body obtained immediately after ironing is performed by a conventional manufacturing method
  • FIG. 14(b) depicts, on an extraction basis, the structure in the vicinity of the lower end of the can body section obtained after doming is further performed
  • FIG. 14(c) depicts, on an extraction basis, the structure in the vicinity of the lower end of the can body section of the seamless can body 1B according to the present embodiment.
  • the present invention is not limited to this form. As described above, t WL ⁇ 1.09 ⁇ t WC may be satisfied.
  • FIG. 14(a) illustrating the conventional technique ironing is first started at the point B with an ironing ratio of 0, the ironing ratio then increases toward the point A, and the ironing ratio reaches the maximum at and beyond the point A. Therefore, regarding the glossiness of the ironed surface of the can body section, for example, the glossiness at the point B is substantially comparable to the glossiness of the original raw sheet surface, the glossiness increases toward the point A, and a maximum glossiness is exhibited at and beyond the point A.
  • FIG. 14(b) depicts that the doming die is relatively moved toward the inside of the tip end of the ironing punch after completion of ironing, resulting in a state in which the dome section is formed at the can bottom section.
  • a part of the can bottom section is drawn into the dome section, the site originally located at the point A is deviated to a point A', and the site originally located at the point B is deviated to the point B'.
  • the deviation amount of each site in the conventional technique is, for example, approximately 2 to 5 mm. Therefore, a part that is low in glossiness and poor in image clarity of print is still left at the lowermost portion of the tubular section of the can body.
  • the ironed metal sheet extends beyond the boundary part BP to reach at least a part of the outer circumferential bottom section, so that the glossiness in the vicinity of the boundary part BP is comparable to that of the can body section.
  • the can body section can have a high glossiness ranging from the upper end to the lower end in the axial direction thereof.
  • the first embodiment and the second embodiment described above are one example in which the gist of the present invention is embodied, and modifications may be made, as required, in such ranges as not to depart from the gist of the invention. Further, known structures may be added to the seamless can bodies described in the first embodiment and the second embodiment, in such ranges as not to depart from the gist of the present invention.
  • the present invention it becomes possible to enhance pressure resistance and restrain the phenomenon of buckling while the sheet thickness of the raw sheet (blank) of the seamless can body is reduced. Therefore, it becomes possible to reduce the manufacturing cost, transportation cost, and the like of the seamless can bodies. In addition, since fuel and the like necessary for the manufacture or transportation is also reduced, it is possible to realize manufacture of seamless can bodies with consideration to environment.
  • the present invention is applicable to containers required to enhance appearance and image clarity and is particularly applicable to can bodies capable of storing liquid such as drinks and drugs.

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  • Containers Having Bodies Formed In One Piece (AREA)
EP20749070.7A 2019-01-30 2020-01-13 Nahtloser dosenkörper und verfahren zur herstellung eines nahtlosen dosenkörpers Pending EP3919200A4 (de)

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JP2019014857A JP6835109B2 (ja) 2019-01-30 2019-01-30 シームレス缶体及びシームレス缶体の製造方法
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