CAN LID SHELL, MANUFACTURING METHOD FOR SAME, AND FORMING DEVICE

Abstract

A can lid shell 10 includes a panel section 11 having a circular peripheral edge, a countersink section 12 formed and recessed along the peripheral edge of the panel section 11, a chuck wall section 13 rising from an edge of the countersink section 12, and a flange section 14 protruding from an upper end of the chuck wall section 13. The countersink section 12 includes a first curved surface portion 123C that is convex toward an internal space SP1. The chuck wall section 13 includes a second curved surface portion 131 that is connected to the first curved surface portion 123C and that is concave toward the internal space SP1. Furthermore, the second curved surface portion 131 and the first curved surface portion 123C are formed to be thicker as both are directed from an edge p8 on the flange section 14 side to an edge p6 on the panel section 11 side.

Claims

1. A can lid shell comprising: a panel section having a circular peripheral edge; a countersink section formed and recessed along the peripheral edge of the panel section; a chuck wall section rising from an edge of the countersink section; and a flange section protruding from an upper end of the chuck wall section, wherein an internal space set inside the panel section, the countersink section, and the chuck wall section is provided, the countersink section includes a first curved surface portion that is convex toward the internal space, the chuck wall section includes a second curved surface portion that is connected to the first curved surface portion and that is concave from the internal space, and thicknesses of the second curved surface portion and the first curved surface portion increase from an edge on the flange section side toward an edge on the panel section side.

2. The can lid shell according to claim 1, wherein the countersink section includes a third curved surface portion formed in such a manner that the first curved surface portion is disposed between the second curved surface portion and the third curved surface portion, the third curved surface portion is connected to the first curved surface portion, and is convex toward the internal space, and furthermore, a thickness of the third curved surface portion increases as the third curved surface portion is directed from the edge on the panel section side to an edge connected to the first curved surface portion.

3. The can lid shell according to claim 2, further comprising: a plurality of thin portions recessed and formed from the second curved surface portion to the third curved surface portion, and provided to be separated in a circumferential direction of the can lid shell on a front surface or a back surface of the can lid shell; and a thick portion that is provided between the can lid shell and the thin portion and that is thicker than the thin portion, wherein in the plurality of thin portions and a plurality of the thick portions, dimensions along a radius of the can lid shell in a plan view or in a bottom view of the can lid shell are longer than dimensions along a direction orthogonal to a direction of the radius.

4. A forming device comprising: a lower die; and an upper die, wherein the forming device forms a can lid shell by pinching a circular blank between the lower die and the upper die, the lower die includes a die core ring, and a panel punch disposed inside the die core ring, the upper die includes a tubular upper piston, a tubular inner sleeve disposed inside the upper piston, and a die center disposed inside the inner sleeve, an outer portion of a tip portion of the die core ring and a tip portion of the upper piston are disposed to face each other, an inner portion of the tip portion of the die core ring and a tip portion of the inner sleeve are disposed to face each other, the panel punch and the die center are disposed to face each other, the inner portion of the tip portion of the die core ring includes a first lower die curved surface portion that is concave toward the inner sleeve, and a second lower die curved surface portion that is connected to the first lower die curved surface portion, that is disposed to be further shifted to a central axis side, and that is convex toward the inner sleeve, the tip portion of the inner sleeve includes a first upper die curved surface portion that is convex toward the first lower die curved surface portion, a second upper die curved surface portion that is connected to the first upper die curved surface portion, that is disposed to be further shifted to the central axis side, and that is convex toward the first lower die curved surface portion in an arc shape whose curvature radius is different from a curvature radius of the first upper die curved surface portion, and a third upper die curved surface portion that is connected to the second upper die curved surface portion, that is disposed to be further shifted to the central axis side, and that is concave toward the second lower die curved surface portion, and a mold clearance formed between the first lower die curved surface portion and the second lower die curved surface portion of the die core ring and the second upper die curved surface portion and the third upper die curved surface portion of the inner sleeve is an interval equal to or larger than a plate thickness of the circular blank, and is further widened as the mold clearance is directed to the central axis.

5. A forming device comprising: a lower die; and an upper die, wherein the forming device forms a can lid shell by pinching a circular blank between the lower die and the upper die, the lower die includes a die core ring, and a panel punch disposed inside the die core ring, the upper die includes a tubular upper piston, a tubular inner sleeve disposed inside the upper piston, and a die center disposed inside the inner sleeve, the die core ring includes a tubular fixing portion provided to be fixed to the lower die, a movable portion provided inside the fixing portion, and a biasing member configured to be expandable and contractible along a central axis, supporting the movable portion from below, and biasing the movable portion, a tip portion of the fixing portion of the die core ring and a tip portion of the upper piston are disposed to face each other, a tip portion of the movable portion of the die core ring and a tip portion of the inner sleeve are disposed to face each other, the panel punch and the die center are disposed to face each other, the tip portion of the movable portion includes a lower die curved surface portion that is convex toward the inner sleeve, the tip portion of the inner sleeve includes an upper die curved surface portion that is concave toward the lower die curved surface portion, a mold clearance formed between the lower die curved surface portion of the movable portion and the upper die curved surface portion of the inner sleeve is an interval equal to or larger than a plate thickness of the circular blank, and is further widened as the mold clearance is closer to the central axis, and the movable portion retreats toward the biasing member by being pushed against an intermediate formed body when deep drawing is performed on the circular blank.

6. The forming device according to claim 5, wherein the lower die further includes a tubular lower piston surrounding a portion of an outer peripheral surface of the die core ring, the fixing portion includes a through-hole penetrating from the inside of the fixing portion to an outside of the fixing portion, and a block disposed in the through-hole, the block has an outer inclined surface protruding to the outside of the fixing portion and an inner inclined surface protruding to the inside of the fixing portion, the lower piston has an inner inclined surface that abuts on the outer inclined surface of the block, the movable portion has an outer inclined surface that abuts on the inner inclined surface of the block, and when the lower piston is lowered by being pushed against the upper die, the inner inclined surface of the lower piston abuts on the outer inclined surface of the block, and in a state where the outer inclined surface of the retreated movable portion abuts on the inner inclined surface of the block, the lower piston is further lowered to move the movable portion toward the inner sleeve.

7. A manufacturing method for a can lid shell in which a can lid shell is formed by pinching a circular blank between a lower die and an upper die, the method comprising: a deep drawing step of forming the circular blank in a first formed body having a tray shape; and a reverse step of moving a flat portion at a bottom of the first formed body pinched between a panel punch and a die center, upward to form a countersink section recessed around the flat portion, wherein in the deep drawing step, a first inflection portion including a concave surface and a convex surface is formed between the flat portion of the first formed body and a flange section by deforming a portion of the circular blank with a tip portion of a die core ring and a tip portion of an inner sleeve, and in the reverse step, in a state where a space between the tip portion of the die core ring and the tip portion of the inner sleeve is formed as a mold clearance widened as the mold clearance is closer to a central axis, a portion of the first formed body protruding from between the panel punch and the die center is pushed into a gap which is not filled with the first inflection portion in the mold clearance, and a second inflection portion in which the first inflection portion is thickened is formed.

8. The manufacturing method for a can lid shell according to claim 7, wherein the die core ring includes a movable portion forming a portion facing the tip portion of the inner sleeve in the tip portion of the die core ring, and a biasing member configured to be expandable and contractible along the central axis and supporting the movable portion from below to hold the movable portion at a position where the mold clearance is formed, and in the deep drawing step, an intermediate formed body pushes the movable portion, and the movable portion retreats toward the biasing member.

Description

BRIEF DESCRIPTION OF DRAWINGS

[0034] FIG. 1A is a plan view illustrating a can lid shell according to a first embodiment of the present invention.

[0035] FIG. 1B is a view illustrating a cross section of the can lid shell taken along line S1-S1 in FIG. 1A.

[0036] FIG. 2 is an enlarged view of a cut end surface of a location surrounded by a circle of a one-dot chain line in FIG. 1B.

[0037] FIG. 3 is an enlarged cross-sectional view of an inflection portion of the can lid shell according to the first embodiment of the present invention.

[0038] FIG. 4 is a view illustrating a cross section of a forming device for forming the can lid shell according to the first embodiment of the present invention.

[0039] FIG. 5 is an enlarged cross-sectional view of a portion of a lower die and an upper die of the forming device in FIG. 4.

[0040] FIG. 6 is an enlarged view of a location surrounded by a circle of a one-dot chain line in FIG. 5.

[0041] FIG. 7 is a view illustrating a manufacturing method for the can lid shell according to the first embodiment of the present invention.

[0042] FIGS. 8A and 8B are views for describing a blanking step in the manufacturing method for the can lid shell according to the first embodiment of the present invention.

[0043] FIGS. 9A and 9B are views for describing a deep drawing step in the manufacturing method for the can lid shell according to the first embodiment of the present invention.

[0044] FIGS. 10A and 10B are views for describing a reverse step in the manufacturing method for the can lid shell according to the first embodiment of the present invention.

[0045] FIG. 11 is a view illustrating a cross section of a first formed body.

[0046] FIG. 12 is a view for describing the manufacturing method for the can lid shell according to the first embodiment of the present invention.

[0047] FIG. 13 is a view for describing the manufacturing method for the can lid shell according to the first embodiment of the present invention.

[0048] FIG. 14A is a plan view illustrating a can lid shell according to a second embodiment of the present invention.

[0049] FIG. 14B is a view illustrating a cross section of the can lid shell taken along line S2-S2 in FIG. 14A.

[0050] FIG. 15 is an enlarged view of a location surrounded by a circle of a one-dot chain line in FIG. 14A.

[0051] FIG. 16 is a view illustrating a cross section of the shell taken along line S3-S3 in FIG. 15.

[0052] FIG. 17 is an enlarged view of a location surrounded by a one-dot chain line in FIG. 14B.

[0053] FIG. 18 is an enlarged view illustrating a modification example of a concave portion and a convex portion of the can lid shell according to the second embodiment of the present invention.

[0054] FIG. 19 is an enlarged view illustrating a modification example of the concave portion and the convex portion of the can lid shell according to the second embodiment of the present invention.

[0055] FIG. 20 is an enlarged view illustrating a modification example of the concave portion and the convex portion of the can lid shell according to the second embodiment of the present invention.

[0056] FIG. 21 is a view for describing a reforming step according to the second embodiment of the present invention.

[0057] FIG. 22 is an enlarged view of a location surrounded by a one-dot chain line in FIG. 21.

[0058] FIG. 23 is a view illustrating a cross section of a forming device according to a first modification example of the present invention.

[0059] FIG. 24 is a view illustrating a cross section of a die core ring.

[0060] FIG. 25 is an enlarged view of a portion of a cross section of a movable portion and an upper piston facing portion.

[0061] FIG. 26 is an enlarged view of a portion of a cross section of a forming device according to the first modification example of the present invention.

[0062] FIGS. 27A, 27B, 27C and 27D are views for describing a manufacturing method for a shell by using the forming device according to the first modification example of the present invention.

[0063] FIG. 28 is a view for describing the manufacturing method for the shell by using the forming device according to the first modification example of the present invention.

[0064] FIG. 29 is a view illustrating a cross section of a forming device according to a second modification example of the present invention.

[0065] FIG. 30 is a view illustrating cross sections of a die core ring, a lower piston, a movable portion, a block, and a spring.

[0066] FIG. 31 is an enlarged view of a cross section of the block.

[0067] FIG. 32 is an enlarged cross-sectional view of an extending portion of the lower piston.

[0068] FIG. 33 is an enlarged view of a cross section of a movable portion.

[0069] FIGS. 34A, 34B, 34C, 34D and 34E are views for describing a manufacturing method for a shell by using a forming device according to a second modification example of the present invention.

[0070] FIG. 35 is a view illustrating a cross section of a can lid shell in the related art.

[0071] FIG. 36 is a view illustrating a cross section of a can lid having a reduced weight.

[0072] FIG. 37 is a view illustrating a cross section of the can lid when buckling occurs.

DESCRIPTION OF EMBODIMENTS

[0073] A can lid shell 10 according to a first embodiment of the present invention will be described with reference to the drawings.

[0074] As illustrated in FIGS. 1A and 1B, the can lid shell 10 includes a panel section 11 in which an outline in a plan view is formed in a circular shape, a countersink section 12 formed and recessed along a peripheral edge of the panel section 11, a chuck wall section 13 rising from an edge of the countersink section 12 and defining an internal space SP1 together with the panel section 11 and the countersink section 12, and a flange section 14 protruding from an upper end (end portion on a side in a radius outer direction Do) of the chuck wall section 13. As illustrated in FIG. 1B, the internal space SP1 is a space on the panel section 11 inside the chuck wall section 13.

[0075] In the following description, in directions along a radius from a central axis C orthogonal to the panel section 11 around a center of the panel section 11, a direction from the central axis C toward an outside will be referred to as the radius outer direction Do, and a direction from the outside toward the central axis C will be referred to as a radius inner direction Di. In addition, a direction from the countersink section 12 side toward the chuck wall section 13 along the central axis C will be referred to as a first direction D1, and a direction from the chuck wall section 13 toward the countersink section 12 side along the central axis C, which is opposite to the first direction D1 will be referred to as a second direction D2 (refer to FIG. 2).

[0076] As front and back surfaces of the can lid shell 10, a surface of the can lid shell 10 including a location defining the internal space SP1 and one surface of the flange section 14 which is adjacent to the location is defined as a front surface SF1, and a surface on a side opposite to the front surface SF1 is defined as a back surface SF2.

[0077] FIGS. 1B and 2 illustrate a cross-sectional shape of the can lid shell 10 when cut along a virtual surface passing through the central axis C and widened in the radius outer direction Do. Hereinafter, the cross-sectional shape of the can lid shell 10 will be described.

(Panel Section 11)

[0078] The panel section 11 is formed as a flat disk, and a thickness thereof is set to be substantially uniform.

(Countersink Section 12)

[0079] The countersink section 12 includes a groove bottom portion 121 forming a deep location, a first groove wall portion 122 extending from an edge on a side in the radius inner direction Di of the groove bottom portion 121 to a peripheral edge of the panel section 11, and a second groove wall portion 123 extending from an edge on a side in the radius outer direction Do of the groove bottom portion 121 to an edge on a side in the radius inner direction Di of the chuck wall section 13.

[0080] The groove bottom portion 121 has a cross section formed as an arc of a radius r12 from a center C12 disposed in the internal space SP1, and has a curved surface which is concave from the internal space SP1 side. A deepest portion is disposed in the groove bottom portion 121, and a connection location (first connection point p1) where the groove bottom portion 121 and the first groove wall portion 122 are connected to each other is disposed to be shifted to a side in the radius inner direction Di from the deepest portion, and is disposed to be shifted in the first direction D1 from the deepest portion.

[0081] Furthermore, a connection location (second connection point p2) where the groove bottom portion 121 and the second groove wall portion 123 are connected to each other is disposed to be shifted to a side in the radius outer direction Do from the deepest portion, and is disposed to be shifted in the first direction D1 from the deepest portion. In FIG. 2, a position of each connection point is indicated by a mark.

(First Groove Wall Portion 122)

[0082] The first groove wall portion 122 includes a first inclined groove cross-sectional portion 122A in which one edge is connected to an edge on the side in the radius inner direction Di of the groove bottom portion 121 to form the first connection point p1, and furthermore, whose inclination with respect to the central axis C is formed to be constant, and a first convex type groove cross-sectional portion 122B having an arc that is formed from the other edge of the first inclined groove cross-sectional portion 122A to the peripheral edge of the panel section 11 and that is convex to the internal space SP1 side.

[0083] A connection location (third connection point p3) where the first inclined groove cross-sectional portion 122A and the first convex type groove cross-sectional portion 122B are connected to each other is disposed to be shifted in the radius inner direction Di from the first connection point p1, and is disposed to be shifted in the first direction D1 from the first connection point p1.

[0084] A connection location (fourth connection point p4) where the first convex type groove cross-sectional portion 122B and the panel section 11 are connected to each other is disposed to be shifted to the side in the radius inner direction Di from the third connection point p3, and is disposed to be shifted in the first direction D1 from the third connection point p3. The first convex type groove cross-sectional portion 122B has a curved surface whose radius from the central axis C gradually decreases (diameter is reduced) from the third connection point p3 toward the fourth connection point p4.

(Second Groove Wall Portion 123)

[0085] The second groove wall portion 123 includes a second inclined groove cross-sectional portion 123A in which one edge is connected to an edge on the side in the radius outer direction Do of the groove bottom portion 121 to form the second connection point p2, and furthermore, whose inclination with respect to the central axis C is formed to be constant, a second convex type groove cross-sectional portion 123B (corresponding to a third curved surface portion of the present invention) having an arc in which one edge is connected to the other edge of the second inclined groove cross-sectional portion 123A and that is convex to the internal space SP1 side, and a third convex type groove cross-sectional portion 123C (corresponding to a first curved surface portion of the present invention) having an arc in which one edge is connected to the other edge of the second convex type groove cross-sectional portion 123B and that is convex to the internal space SP1 side with a curvature radius different from a curvature radius of the second convex type groove cross-sectional portion 123B.

[0086] A connection location (fifth connection point p5) where the second inclined groove cross-sectional portion 123A and the second convex type groove cross-sectional portion 123B are connected to each other is disposed to be shifted in the radius outer direction Do from the second connection point p2, and is disposed to be shifted in the first direction D1 from the second connection point p2. A connection location (sixth connection point p6) where the second convex type groove cross-sectional portion 123B and the third convex type groove cross-sectional portion 123C are connected to each other is disposed to be shifted to the side in the radius outer direction Do from the fifth connection point p5, and is disposed to be shifted in the first direction D1 from the fifth connection point p5.

[0087] A connection location (seventh connection point p7) where the third convex type groove cross-sectional portion 123C and the chuck wall section 13 are connected to each other is disposed to be shifted in the radius outer direction Do from the sixth connection point p6, and is disposed to be shifted in the first direction D1 from the sixth connection point p6.

[0088] The second convex type groove cross-sectional portion 123B has a curved surface in which the radius from the central axis C gradually increases (diameter is enlarged) from the fifth connection point p5 toward the sixth connection point p6.

[0089] The third convex type groove cross-sectional portion 123C has a curved surface in which the radius from the central axis C gradually increases (diameter is enlarged) from the sixth connection point p6 toward the seventh connection point p7.

[0090] As illustrated in FIG. 3, on the front surface SF1 of the can lid shell 10, a center C56 having an arc formed by the second convex type groove cross-sectional portion 123B is disposed in an outer space SP2, a center C67 having an arc formed by the third convex type groove cross-sectional portion 123C is disposed in the outer space SP2, and the center C56 of the arc of the second convex type groove cross-sectional portion 123B is disposed to be slightly shifted to the side in the radius inner direction Di from the center C67 of the arc of the third convex type groove cross-sectional portion 123C, and is disposed to be slightly shifted in the first direction D1. In addition, a radius r56 having the arc of the second convex type groove cross-sectional portion 123B is set to be smaller than a radius r67 of the arc of the third convex type groove cross-sectional portion 123C.

[0091] In addition, on the back surface SF2 of the can lid shell 10, a portion from the fifth connection point p5 to the seventh connection point p7 via the sixth connection point p6 is formed in an arc of a constant radius r57 from the center C57.

[0092] In the third convex type groove cross-sectional portion 123C, the center C67 of the arc of the front surface SF1 is disposed to be shifted to the side in the radius inner direction Di from the center C57 of the arc of the back surface SF2, and is also disposed to be shifted in the first direction D1. In addition, the radius r57 of the arc of the back surface SF2 is set to be smaller than the radius r56 of the arc of the second convex type groove cross-sectional portion 123B and the radius r67 of the arc of the third convex type groove cross-sectional portion 123C.

(Chuck Wall Section 13)

[0093] The chuck wall section 13 includes a first concave type surrounding cross-sectional portion 131 (corresponding to a second curved surface portion of the present invention) of the arc in which one edge (side in the radius inner direction Di) is connected to an edge on the side in the radius outer direction Do of the second convex type groove cross-sectional portion 123B of the countersink section 12 to form the sixth connection point p6 and that is concave toward the internal space SP1 side, a second concave type surrounding cross-sectional portion 132 of the arc in which one edge (side in the radius inner direction Di) is connected to the other edge (side in the radius outer direction Do) of the first concave type surrounding cross-sectional portion 131 and that is concave toward the internal space SP1 side with the curvature radius different from the curvature radius of the first concave type surrounding cross-sectional portion 131, an inclined surrounding cross-sectional portion 133 in which one edge (side in the radius inner direction Di) is connected to the other edge (side in the radius outer direction Do) of the second concave type surrounding cross-sectional portion 132, and furthermore, whose inclination with respect to the central axis C is formed to be constant, and a convex type surrounding cross-sectional portion 134 of the arc in which one edge (side in the radius inner direction Di) is connected to the other edge (side in the radius outer direction Do) of the inclined surrounding cross-sectional portion 133 and that is convex toward the internal space SP1 side.

(First Concave Type Surrounding Cross-Sectional Portion 131)

[0094] A connection location (eighth connection point p8) where the first concave type surrounding cross-sectional portion 131 and the second concave type surrounding cross-sectional portion 132 are connected to each other is disposed to be shifted in the radius outer direction Do from the seventh connection point p7, and is disposed to be shifted in the first direction D1 from the seventh connection point p7. The first concave type surrounding cross-sectional portion 131 has a curved surface in which the radius from the central axis C gradually increases (diameter is enlarged) from the seventh connection point p7 toward the eighth connection point p8.

[0095] The first concave type surrounding cross-sectional portion 131 of the chuck wall section 13 and the third convex type groove cross-sectional portion 123C of the countersink section 12 have opposite bending directions of the curved surfaces. Therefore, the seventh connection point p7 forms the inflection point.

(Second Concave Type Surrounding Cross-Sectional Portion 132)

[0096] A connection location (ninth connection point p9) where the second concave type surrounding cross-sectional portion 132 and the inclined surrounding cross-sectional portion 133 are connected to each other is disposed to be shifted in the radius outer direction Do from the eighth connection point p8, and is disposed to be shifted in the first direction D1 from the eighth connection point p8. The second concave type surrounding cross-sectional portion 132 has a curved surface in which the radius from the central axis C gradually increases (diameter is enlarged) from the eighth connection point p8 toward the ninth connection point p9.

[0097] As illustrated in FIG. 3, a center C89 of the arc formed by the front surface SF1 in the second concave type surrounding cross-sectional portion 132 is disposed inside the internal space SP1, and a center C78 of the arc formed by the front surface SF1 in the first concave type surrounding cross-sectional portion 131 is disposed inside the internal space SP1. The center C89 of the arc of the front surface SF1 in the second concave type surrounding cross-sectional portion 132 is disposed to be shifted to the side in the radius inner direction Di from the center C78 of the arc of the first concave type surrounding cross-sectional portion 131, and is disposed to be shifted in the first direction D1.

[0098] In addition, a radius r89 of the arc formed by the front surface SF1 in the second concave type surrounding cross-sectional portion 132 is set to be larger than a radius r78 of the arc formed by the front surface SF1 in the first concave type surrounding cross-sectional portion 131.

[0099] On the back surface SF2 of the can lid shell 10, a portion from the seventh connection point p7 to the ninth connection point p9 via the eighth connection point p8 is formed in an arc having a constant radius r79 from the center C89.

(Inclined Surrounding Cross-Sectional Portion 133)

[0100] A connection location (tenth connection point p10) where the inclined surrounding cross-sectional portion 133 and the convex type surrounding cross-sectional portion 134 are connected to each other is disposed to be shifted in the radius outer direction Do from the ninth connection point p9, and is disposed to be shifted in the first direction D1 from the ninth connection point p9. The inclined cross-sectional portion 133 has an inclined surface in which the radius from the central axis C gradually increases (diameter is enlarged) from the ninth connection point p9 toward the tenth connection point p10 and the inclination is constant.

(Convex Type Surrounding Cross-Sectional Portion 134)

[0101] A connection location (eleventh connection point p11) where the convex type surrounding cross-sectional portion 134 and the flange section 14 are connected to each other is disposed to be shifted in the radius outer direction Do from the tenth connection point p10, and is disposed to be shifted in the first direction D1 from the tenth connection point p10. The convex type surrounding cross-sectional portion 134 has a curved surface in which the radius from the central axis C gradually increases (diameter is enlarged) from the tenth connection point p10 toward the eleventh connection point p11. The eleventh connection point p11 is a location that is farthest separated from the deepest portion in the can lid shell 10 along the first direction D1, that is, the eleventh connection point p11 forms a highest location (apex).

(Flange Section 14)

[0102] In the flange section 14, one edge (side in the radius inner direction Di) is connected to the other edge (side in the radius outer direction Do) of the convex type surrounding cross-sectional portion 134 to form the eleventh connection point p11 (apex), and the flange section 14 protrudes in the radius outer direction Do. A tip of the flange section 14 is disposed to be shifted in the radius outer direction Do from the eleventh connection point p11, and is disposed to be shifted in the second direction D2 from the eleventh connection point p11.

[0103] As illustrated in FIG. 2, a tip side of the flange section 14 is formed in a curled shape in a curling step as a subsequent step.

[0104] In the can lid shell 10 configured in this way, a cross section formed by the chuck wall section 13 and the flange section 14 has a hook shape, and furthermore, a portion from the convex type surrounding cross-sectional portion 134 of the chuck wall section 13 to the tip of the flange section 14 has a form of a flange shape.

[0105] Hereinafter, a reinforcing structure of the can lid shell 10 will be described.

[0106] As illustrated in FIG. 3, in the can lid shell 10, the back surface SF2 from the fifth connection point p5 to the seventh connection point p7 (inflection point) via the sixth connection point p6 is formed with the arc having the constant radius r57 from the center C57. In the can lid shell 10, the front surface SF1 from the fifth connection point p5 to the sixth connection point p6 is formed with the arc having the radius r56 longer than the radius r57 from the center C56 disposed to be shifted from the center C57. The second convex type groove cross-sectional portion 123B is formed such that the thickness gradually increases from the fifth connection point p5 toward the sixth connection point p6.

[0107] In the cross-sectional view in FIG. 3, each connection point is indicated by a mark indicating a position on the front surface SF1, a mark indicating a position on the back surface SF2, and a solid line connecting both the marks.

[0108] In addition, in the can lid shell 10, the front surface SF1 from the sixth connection point p6 to the seventh connection point p7 is formed with the arc having the radius r67 longer than the radius r57 from the center C67 disposed to be shifted from the center C57 of the arc of the back surface SF2. The third convex type groove cross-sectional portion 123C is formed such that the thickness gradually decreases from the sixth connection point p6 toward the seventh connection point p7.

[0109] In the can lid shell 10, the back surface SF2 from the seventh connection point p7 to the ninth connection point p9 via the eighth connection point p8 is formed with the arc having the constant radius r79 from the center C89, the front surface SF1 from the eighth connection point p8 to the ninth connection point p9 is formed with the arc having the radius r89 that is concentric with the center C89 of the arc of the back surface SF2 and is shorter than the radius r79, and the second concave type surrounding cross-sectional portion 132 is formed with a constant thickness from the eighth connection point p8 toward the ninth connection point p9.

[0110] The seventh connection point p7 is the inflection point between the third convex type groove cross-sectional portion 123C and the first concave type surrounding cross-sectional portion 131, and is disposed on an imaginary line LX1 (illustrated by a one-dot chain line) connecting the center C89 and the center C57 in the drawing.

[0111] In the can lid shell 10, the front surface SF1 from the seventh connection point p7 to the eighth connection point p8 is formed with the radius r78 shorter than the radius r89 from the center C78 disposed to be shifted from the center C89 of the arc of the back surface. The first concave type surrounding cross-sectional portion 131 is formed such that the thickness gradually decreases from the seventh connection point p7 to the eighth connection point p8.

[0112] Specifically, as the thickness of the inflection portion of the can lid shell 10, when the thickness of the sixth connection point p6 is defined as t6, the thickness of the seventh connection point p7 is defined as t7, and the thickness of the eighth connection point p8 is defined as t8, a relationship of t8<t7<t6 is established. The thickness t6 is a dimension along an imaginary line (not illustrated) extending from the center C57, the thickness t7 is a dimension along an imaginary line LX1 extending from the center C57 and the center C89, and the thickness t8 is a dimension along an imaginary line (not illustrated) extending from the center C89.

[0113] In this way, in the can lid shell 10, the inflection point (seventh connection point p7) is disposed in the middle to form the inflection portion 17 including the third convex type groove cross-sectional portion 123C of the countersink section 12 and the first concave type surrounding cross-sectional portion 131 of the chuck wall section 13 formed in a direction having an opposite bending direction of the third convex type groove cross-sectional portion 123C. The thickness of the inflection portion 17 increases from the eighth connection point p8 toward the sixth connection point p6, and is set to have the maximum thickness in the vicinity of the sixth connection point p6.

[0114] The thickness of the inflection portion 17 is equal to or larger than the thickness of a raw plate 400 (circular blank 410) for forming the can lid shell 10, and for example, is the plate thickness of 106% or larger of the plate thickness of the raw plate 400 (circular blank 410).

[0115] Furthermore, the thickness of the can lid shell 10 increases from the fifth connection point p5 toward the sixth connection point p6. When the thickness of the fifth connection point p5 is defined as t5, and the thickness of the sixth connection point p6 is defined as t6, a relationship of t5<t6 is established. The thickness t5 and the thickness t6 are dimensions along an imaginary line (not illustrated) extending from the center C57. The thickness from the fifth connection point p5 to the sixth connection point p6 is equal to or larger than the thickness of the raw plate 400 (circular blank 410) for forming the can lid shell 10.

[0116] In this way, the thickness of the location from the fifth connection point p5 to the eighth connection point p8 is larger than the thickness of the second inclined groove cross-sectional portion 123A adjacent thereto or the second concave type surrounding cross-sectional portion 132. In addition, the thickness increases, compared to the raw plate 400 (circular blank 410). Hereinafter, a location from the fifth connection point p5 to the eighth connection point p8, which is formed to have the increased thickness including the inflection point (seventh connection point p7), will be referred to as a thickened portion 18.

[0117] In the can lid shell 10, the above-described cross-sectional structure is formed all around the central axis C, and the thickened inflection portion 17 is disposed in an annular shape in a plan view.

[0118] The can lid shell 10 is formed by performing press working on the circular blank 410 including an aluminum alloy (for example, 5,000 series alloy). For example, the thickness of each portion of the can lid shell 10 is 0.20 mm or larger and 0.26 mm or smaller.

[0119] The can lid includes the above-described can lid shell 10, a tear line for forming an opening formed in the can lid shell 10, and a tab for an opening operation.

[0120] The manufacturing method for the can lid includes a can lid shell forming step of forming the can lid shell 10 and a conversion forming step of providing the tear line, the tab, or the like for the can lid shell 10 by using a conversion press.

[0121] Hereinafter, a forming device 2 for performing a can lid shell forming step (manufacturing method for the can lid shell 10) in the manufacturing method for the can lid will be described.

(Forming Device 2)

[0122] As illustrated in FIG. 4, the forming device 2 includes a lower die 200 and an upper die 300 in a press machine (not illustrated).

[0123] The central axes of the lower die 200 and the upper die 300 are set to be coaxial with the central axis C of the can lid shell 10 to be formed, and hereinafter, the axes will be collectively referred to as the central axis C. In addition, in the following description, in the directions along the radius from the central axis C, a direction from the central axis C toward the outside will be referred to as the radius outer direction Do, and a direction from the outside toward the central axis C will be referred to as a radius inner direction Di.

[0124] Furthermore, in the directions along the central axis C, a direction from the lower die 200 toward the upper die 300 corresponds to the first direction D1 of the can lid shell 10 inside the forming device 2. Therefore, the direction from the lower die 200 toward the upper die 300 may be referred to as the first direction D1, and the direction from the upper die 300 toward the lower die 200 may be referred to as the second direction D2. In addition, in describing the forming device 2, the first direction D1 will be described as an upward direction and the second direction D2 will be described as a downward direction.

(Lower Die 200)

[0125] The lower die 200 includes a lower retainer 210, a cut edge portion 220 held by a tip portion of the lower retainer 210 on the upper die 300 side (side in the first direction D1), a die core ring 230 held inside the lower retainer 210, a panel punch piston 240 provided inside the die core ring 230, a panel punch 250 fixed to a tip portion of the panel punch piston 240, and a lower piston 260 that surrounds a portion of the die core ring 230.

[0126] The lower retainer 210 includes a base portion 211 having a hole portion 211A penetrating the center, and a tubular portion 212 fixed to an upper portion of the base portion 211 and having an inner peripheral surface having a larger inner diameter than the hole portion 211A. The tubular portion 212 includes a stepped portion 212A inside a tip portion opposite to the base end fixed to the base portion 211.

[0127] The cut edge portion 220 is formed in a ring shape, is disposed in a stepped portion 212A of the lower retainer 210, and a side of an inner peripheral surface 221 protrudes toward the central axis C from an inner peripheral surface of the tubular portion 212 of the lower retainer 210. A lower surface 222 of the cut edge portion 220 is fixed to the stepped portion 212A, and a corner portion 224 is formed by a top surface 223 opposite to the lower surface 222 and the inner peripheral surface 221.

[0128] The die core ring 230 includes a base 231 fixed to an upper surface of the base portion 211 of the lower retainer 210, and an extending portion 232 having the thickness smaller than the thickness of the base 231 along the radial direction from the central axis C and extending from the base 231 to a side opposite to the base portion 211. The die core ring 230 has a hole penetrating along the central axis C, and is disposed inside the tubular portion 212 of the lower retainer 210.

[0129] The panel punch piston 240 integrally includes a piston body portion 241 that slides on the inner peripheral surface of the die core ring 230 and an extending portion 242 extending from the piston body portion 241, and can move along the central axis C. The piston body portion 241, the die core ring 230, and the lower retainer 210 form a space SP21. Air is supplied to the space SP21 through a flow path (not illustrated) to control the panel punch piston 240.

[0130] As illustrated in FIG. 5, the panel punch 250 includes a punch flat portion 251 that cooperates with the flat portion 341 of the die center 340 to pinch a circular blank, and a punch stepped portion 252 provided along a peripheral edge of the punch flat portion 251 and having a receiving surface 252A formed to be shifted toward the panel punch piston 240 side than the punch flat portion 251. The receiving surface 252A is formed with a cross section having an arc that is concave toward the upper die 300.

[0131] The lower piston 260 is formed in an entire tubular shape by providing a piston body portion 261 that slides on an inner peripheral surface of the lower retainer 210 and an outer peripheral surface of the die core ring 230, and an extending portion 262 that has a thickness smaller than a thickness of the piston body portion 261 in a radial direction from the central axis C and extends from the piston body portion 261. In addition, the lower piston 260 can be moved along the central axis C.

[0132] The space SP22 is formed by the piston body portion 261 of the lower piston 260, the lower retainer 210, and the die core ring 230. Air is supplied to the space SP22 through a flow path (not illustrated) to control the lower piston 260.

(Upper Die 300)

[0133] The upper die 300 includes an upper retainer 310, a blank draw die 320 held by the upper retainer 310, a die center piston 330 provided inside the upper retainer 310, a die center 340 fixed to a tip portion of the die center piston 330, an inner sleeve 350 surrounding the die center 340, and an upper piston 360 surrounding the inner sleeve 350.

[0134] The upper retainer 310 integrally includes a first tubular portion 311, a second tubular portion 312 formed to have a smaller inner diameter than the first tubular portion 311, and a third tubular portion 313 formed to have a larger inner diameter than the second tubular portion 312. The inner side of the third tubular portion 313 is formed as a stepped portion 313A, and forms an opening end. A portion between an inner peripheral surface of the first tubular portion 311 and an inner peripheral surface of the second tubular portion 312 forms a stepped portion 314.

[0135] The blank draw die 320 includes a base 321 formed in a ring shape, and a tubular portion 322 having the smaller thickness than the base 321 along the radius from the central axis C and extending from the base 321. The base 321 is disposed in the stepped portion 313A of the upper retainer 310, and the inner peripheral surface side of the base 321 protrudes toward the central axis C with respect to the third tubular portion 313 of the upper retainer 310.

[0136] The die center piston 330 includes a rod-shaped portion 331 formed in a rod shape, and a protruding end portion 332 provided in an end of the rod-shaped portion 331 and protruding in a flange shape. The rod-shaped portion 331 is disposed to extend toward the lower die 200 side from an opening end below the upper retainer 310.

[0137] The die center piston 330 can move along the central axis C, and is configured such that a protruding end portion 332 abuts on the stepped portion 314 of the upper retainer 310. The protruding end portion 332 and the inside of the first tubular portion 311 form a space SP31, and the air is supplied through a flow path (not illustrated) to control the die center piston 330.

[0138] The inner sleeve 350 integrally includes a piston body portion 351 that slides on an inner peripheral surface of the upper retainer 310 and the die center piston 330, and an extending portion 352 having the thickness smaller than the thickness of the piston body portion 351 along the radial direction from the central axis C and extending from the piston body portion 351, and is formed in a tubular shape as a whole. The inner sleeve 350 can move along the central axis C.

[0139] The upper piston 360 includes a piston body portion 361 that slides on an inner peripheral surface of the upper retainer 310 and the extending portion 352 of the inner sleeve 350, and an extending portion 362 having the thickness smaller than the thickness of the piston body portion 361 along the radial direction from the central axis C and extending from the piston body portion 361, and is formed in a tubular shape as a whole. The upper piston 360 can move along the central axis C.

[0140] The piston body portion 351 of the inner sleeve 350, the die center piston 330, and the upper retainer 310 form a space SP32. The piston body portion 351 of the inner sleeve 350, the upper retainer 310, and the piston body portion 361 of the upper piston 360 form a space SP33. The air is supplied to the spaces SP32 and SP33 through flow paths (not illustrated) to control the inner sleeve 350 and the upper piston 360.

[0141] In the forming device 2, as illustrated in FIG. 5, the lower piston 260 and the blank draw die 320 are configured such that a flat surface 262B of a tip portion 262A of the extending portion 262 and a flat surface 322B of a tip portion 322A of the tubular portion 322 match each other. The tip portion 322A of the tubular portion 322 of the blank draw die 320 includes a rounded portion 322D whose cross section is formed to have an arc between the flat surface 322B and the inner peripheral surface 322C.

[0142] As illustrated in FIGS. 5 and 6, the extending portion 232 of the die core ring 230 includes a tip portion 232A facing the tip portion 362A of the extending portion 362 of the upper piston 360 and the tip portion 352A of the extending portion 352 of the inner sleeve 350.

[0143] The tip portion 232A of the die core ring 230 includes a first convex surface portion 232B which is formed at a highest location and faces the tip portion 362A of the extending portion 362 of the upper piston 360, and whose cross section is formed in an arc that is convex to the tip portion 362A side, a first inclined surface portion 232C formed to be connected to an edge on the side in the radius inner direction Di of the first convex surface portion 232B, formed d with a constant inclination with respect to the central axis C, and lowered as first inclined surface portion 232C is directed in the radius inner direction Di, a concave surface portion 232D (corresponding to a first lower die curved surface portion of the present invention) which is formed to be connected to a lower end of the first inclined surface portion 232C and whose cross section is formed in an arc that is concave toward the central axis C side, a second convex surface portion 232E (corresponding to a second lower die curved surface portion of the present invention) which is formed to be connected to an edge on the side in the radius inner direction Di of the concave surface portion 232D and whose cross section is formed in an arc that is convex to the central axis C side, and a second inclined surface portion 232F formed to be connected to an edge on the side in the radius inner direction Di of the second convex surface portion 232E, formed with a constant inclination with respect to the central axis C, and lowered as the second inclined surface portion 232F is directed in the radius inner direction Di.

[0144] A connection location (second lower die connection point P22) where the concave surface portion 232D and the second convex surface portion 232E are connected to each other is disposed to be shifted in the radius inner direction Di with respect to a connection location (first lower die connection point P21) where the first inclined surface portion 232C and the concave surface portion 232D are connected to each other, and is disposed to be shifted in the second direction D2. The concave surface portion 232D has a curved surface whose radius from the central axis C gradually decreases (diameter is reduced) from the first lower die connection point P21 toward the second lower die connection point P22. In the cross-sectional view in FIG. 6, each connection point is highlighted by a mark, but is actually a smooth surface.

[0145] A connection location (third lower die connection point P23) where the second convex surface portion 232E and the second inclined surface portion 232F are connected to each other is disposed to be shifted in the radius inner direction Di with respect to the second lower die connection point P22, and is disposed to be shifted in the second direction D2. The second convex surface portion 232E has a curved surface whose radius from the central axis C gradually decreases (diameter is reduced) from the second lower die connection point P22 toward the third lower die connection point P23. The second convex surface portion 232E and the concave surface portion 232D adjacent thereto have reversed orientations of curved surfaces, and are different from each other in that one is the convex surface and the other is the concave surface. Therefore, the second lower die connection point P22 forms the inflection point.

[0146] As illustrated in FIG. 5, the tip portion 362A of the upper piston 360 includes a concave surface portion 362B facing the first convex surface portion 232B of the die core ring 230. The flange section 14 is formed by pinching a circular blank (to be described later) between the concave surface portion 362B of the tip portion 362A of the upper piston 360 and the first convex surface portion 232B of the die core ring 230.

[0147] As illustrated in FIG. 6, the tip portion 352A of the inner sleeve 350 includes a first sleeve convex surface portion 352B which has one edge connected to a lowest location (lowest point P30), extends in the radius outer direction Do from the lowest point P30, and whose cross section is formed in an arc that is convex to the tip portion 232A side of the die core ring 230, a sleeve concave surface portion 352C (corresponding to a third upper die curved surface portion of the present invention) which is formed to be connected to an edge on the side in the radius outer direction Do of the first sleeve convex surface portion 352B and whose cross section is formed in an arc that is concave to the tip portion 232A side of the die core ring 230, a second sleeve convex surface portion 352D (corresponding to the second upper die curved surface portion of the present invention) which is formed to be connected to an edge on the side in the radius outer direction Do of the sleeve concave surface portion 352C and whose cross section is formed in an arc that is convex to the tip portion 232A side of the die core ring 230, a third sleeve convex surface portion 352E (corresponding to a first upper die curved surface portion of the present invention) which is formed to be connected to an edge on the side in the radius outer direction Do of the second sleeve convex surface portion 352D and whose cross section is formed in an arc that is convex to the tip portion 232A side of the die core ring 230 with a curvature radius different from a curvature radius of the arc of the second sleeve convex surface portion 352D, and a sleeve inclined surface portion 352F formed to be connected to an edge on the side in the radius outer direction Do of the third convex surface portion 352E, formed with a constant inclination with respect to the central axis C, and enlarged in diameter as the sleeve inclined surface portion 352F is directed in the radius outer direction Do.

[0148] A connection location (first upper die connection point P31) where the first sleeve convex surface portion 352B and the sleeve concave surface portion 352C are connected to each other is disposed to be shifted in the radius outer direction Do from the lowest point P30, and is disposed to be shifted in the first direction D1. The first sleeve convex surface portion 352B has a curved surface whose radius from the central axis C gradually increases (diameter is enlarged) from the lowest point P30 toward the first upper die connection point P31.

[0149] A connection location (second upper die connection point P32) where the second sleeve convex surface portion 352D and the sleeve concave surface portion 352C are connected to each other is disposed to be shifted in the radius outer direction Do from the first upper die connection point P31, and is disposed to be shifted in the first direction D1. The sleeve concave surface portion 352C has a curved surface whose radius from the central axis C gradually increases (diameter is enlarged) from the first upper die connection point P31 toward the second upper die connection point P32. The sleeve concave surface portion 352C and the first sleeve convex surface portion 352B adjacent thereto have different orientations of the curved surfaces in that one is the concave surface and the other is the convex surface. Therefore, the first upper die connection point P31 forms the inflection point.

[0150] A connection location (third upper die connection point P33) where the third sleeve convex surface portion 352E and the second sleeve convex surface portion 352D are connected to each other is disposed to be shifted in the radius outer direction Do from the second upper die connection point P32, and is disposed to be shifted in the first direction D1. The second sleeve convex surface portion 352D has a curved surface whose radius from the central axis C gradually increases (diameter is enlarged) from the second upper die connection point P32 toward the third upper die connection point P33. The second sleeve convex surface portion 352D and the sleeve concave surface portion 352C adjacent thereto have different orientations of the curved surfaces in that one is the convex surface and the other is the concave surface. Therefore, the second upper die connection point P32 forms the inflection point.

[0151] A connection location (fourth upper die connection point P34) where the sleeve inclined surface portion 352F and the third sleeve convex surface portion 352E are connected to each other is disposed to be shifted in the radius outer direction Do from the third upper die connection point P33, and is disposed to be shifted in the first direction D1. The third sleeve convex surface portion 352E has a curved surface whose radius from the central axis C gradually increases (diameter is enlarged) from the third upper die connection point P33 toward the fourth upper die connection point P34.

[0152] In the forming device 2, press working is performed by pinching the circular blank 410 between the tip portion 232A of the die core ring 230 and the tip portion 352A of the inner sleeve 350 at a predetermined pressure. A spacer 370 having a predetermined thickness is attached to a flange section lower surface 351A (side on the second direction D2) of the piston body portion 351 of the inner sleeve 350.

[0153] When the inner sleeve 350 is lowered toward the die core ring 230 (in the second direction D2) during the deep drawing step, the spacer 370 comes into contact with the upper piston to hold a position of the tip portion 352A of the inner sleeve 350 with respect to the tip portion 232A of the die core ring 230. The mold clearance CL1 for forming the inflection portion 17 can be formed between the tip portion 232A of the die core ring 230 and the inner sleeve 350.

[0154] As illustrated in FIGS. 5, 6, 12, and 13, in the forming device 2, the tip portion 352A of the inner sleeve 350 is closest to the tip portion 232A of the die core ring 230, and the mold clearance CL1 is set between the tip portion 232A of the die core ring 230 and the tip portion 352A of the inner sleeve 350. The mold clearance CL1 is set to be larger than the thickness of the raw plate 400 from the third upper die connection point P33 of the inner sleeve 350 to the first upper die connection point P31.

[0155] When the spacer 370 is not provided, deep drawing is performed in a state where the circular blank 410 is pinched between the inner sleeve 350 and the die core ring 230 at a constant pressure. Therefore, the plate thickness of the inflection portion including the sixth connection point p6 from the eighth connection point p8 is reduced. In addition, the mold clearance in the inflection portion decreases due to the reduction in the plate thickness.

[0156] Hereinafter, the mold clearance CL1 will be described.

[0157] FIG. 6 illustrates a front surface of the tip portion 232A of the die core ring 230. The concave surface portion 232D is formed in an arc having a constant radius r212 from a center C212. The second convex surface portion 232E is formed in an arc having a constant radius r223 from a center C223.

[0158] In a state where the inner sleeve 350 is closest to the die core ring 230, the concave surface portion 232D of the tip portion 232A of the die core ring 230 faces the second sleeve convex surface portion 352D and the third sleeve convex surface portion 352E of the tip portion 352A of the inner sleeve 350.

[0159] Here, the third sleeve convex surface portion 352E is an arc formed around the same point as the center C212 of the concave surface portion 232D of the die core ring 230, and a radius r334 of the arc is shorter than the radius r212 of the concave surface portion 232D of the die core ring 230. In this manner, an interval is constant between the third sleeve convex surface portion 352E of the inner sleeve 350 and the concave surface portion 232D of the die core ring 230 in a state where both are closest to each other.

[0160] The center C323 of the arc of the second sleeve convex surface portion 352D is disposed to be shifted in the radius outer direction Do from the center C212 of the arc of the concave surface portion 232D of the die core ring 230, and is also disposed to be shifted in the second direction D2. In addition, the radius r323 of the arc of the second sleeve convex surface portion 352D is set to be shorter than the radius r212 of the arc of the concave surface portion 232D of the die core ring 230 or the radius r334 of the arc of the third sleeve convex surface portion 352E.

[0161] In a cross section, when it is assumed that a first tangent line T1 is in contact with each point disposed between the second upper die connection point P32 and the third upper die connection point P33 of the second sleeve convex surface portion 352D, and it is assumed that a second tangent line T2 is in contact with each point disposed between the third upper die connection point P33 and the fourth upper die connection point P34 of the third sleeve convex surface portion 352D, an angle 1 formed between the first tangent line T1 and a horizontal line HL is set to be smaller than an angle 2 formed between the second tangent line T2 and the horizontal line HL (1<2) (except for a tangent line in contact with the third upper die connection point P33).

[0162] In this manner, when an interval between the second sleeve convex surface portion 352D of the inner sleeve 350 and the concave surface portion 232D of the die core ring 230 is captured in a dimension along an imaginary line extending from the center C212, the interval is formed to be wider from the third upper die connection point P33 toward the second upper die connection point P32 of the inner sleeve 350.

[0163] The center C312 of the arc of the sleeve concave surface portion 352C is disposed to be shifted in the radius inner direction Di from the center C223 of the arc of the second convex surface portion 232E of the die core ring 230, and is also disposed to be shifted in the first direction D1. In addition, the radius r312 of the arc of the sleeve concave surface portion 352C is set to be longer than the radius r223 of the arc of the second convex surface portion 232E of the die core ring 230.

[0164] Here, the second lower die connection point P22 and the second upper die connection point P32 as the inflection points are disposed on an imaginary line LX2 connecting the center C212 and the center C223 which are indicated by a one-dot chain line in the drawing.

[0165] When an interval between the sleeve concave surface portion 352C and the second convex surface portion 232E of the die core ring 230 is captured in a dimension along an imaginary line extending from the center C223, the interval is formed to be widened from the second upper die connection point P32 toward the first upper die connection point P31 of the inner sleeve 350.

[0166] In this way, the mold clearance CL1 is formed to be wider from the third upper die connection point P33 toward the first upper die connection point P31 of the inner sleeve 350. When a dimension of the clearance at the third upper die connection point P33 is defined as CL33, a dimension of the clearance at the second upper die connection point P32 is defined as CL32, and a dimension of the clearance at the first upper die connection point P31 is defined as CL31, a relationship of CL33<CL32<CL31 is established.

[0167] CL33 is a dimension along an imaginary line extending from the center C212 to the inside of the die core ring 230 through the third upper die connection point P33. The CL32 is a dimension along an imaginary line extending from the center C212 or the center 223 and passing through the second upper die connection point P32 and the second lower die connection point P22. CL31 is a dimension along an imaginary line passing through the first upper die connection point P31 and extending from the center 223 to the inside of the inner sleeve 350.

[0168] The mold clearance CL1 from the third upper die connection point P33 to the first upper die connection point P31 of the inner sleeve 350 is set to be larger than the thickness of the raw plate 400.

(Manufacturing Method for Can Lid Shell 10)

[0169] As illustrated in FIG. 7, the manufacturing method for the can lid shell 10 by using the forming device 2 includes a blanking step (FIGS. 8A and 8B) of punching the circular blank from the raw plate made of an aluminum alloy, a deep drawing step (FIGS. 9A and 9B) of performing deep drawing on the circular blank to form the first formed body having a shallow bottom, and a reverse step (FIGS. 10A and 10B) of moving a bottom side of the first formed body in an opposite direction to form the countersink section 12.

[0170] Each step will be described with reference to FIGS. 8A to 10B (FIGS. 8A, 8B, 9A, 9B, 10A, and 10B). FIGS. 8A to 10B illustrate a left side portion from the central axis C of the forming device 2 illustrated in FIG. 4.

(Blanking Step)

[0171] First, as illustrated in FIG. 8A, the raw plate 400 is placed on the lower die 200 in a state where the upper die 300 is disposed above the lower die 200. In the lower die 200, the cut edge portion 220 and the tip portion 262A of the lower piston 260 are disposed to be aligned in heights, and the raw plate 400 is supported by upper end portions thereof.

[0172] As illustrated in FIG. 8B, the upper die 300 is lowered, a portion of the raw plate 400 is pushed into the cut edge portion 220 by the blank draw die 320, and the circular blank 410 is punched. The punched circular blank 410 is held by pinching a peripheral edge portion between the tip portion 262A of the lower piston 260 of the lower die 200 and the tip portion 322A of the blank draw die 320 of the upper die 300.

(Deep Drawing Step)

[0173] In the deep drawing step, first, as illustrated in FIG. 9A, the upper die 300 is lowered, and the circular blank 410 is pinched between the tip portion 232A of the die core ring 230 and the tip portion 362A of the upper piston 360.

[0174] Next, as illustrated in FIG. 9B, the upper die 300 is further lowered, the tip portion 322A of the blank draw die 320 is placed between the cut edge portion 220 and the die core ring 230, the tip portion 352A of the inner sleeve 350 is brought close to the tip portion 232A of the die core ring 230 until the mold clearance CL1 is formed, and the flat portion 341 of the die center 340 is placed inside the die core ring 230.

[0175] That is, deep drawing is performed by moving the central portion of the circular blank in the second direction by pinching the central portion of the circular blank between the flat portion 341 of the die center 340 and the punch flat portion 251 of the panel punch 250. FIG. 9B illustrates the first formed body 420 formed by performing the deep drawing step in a state where the upper die 300 is located at a bottom dead center.

[0176] As illustrated in FIG. 11, the first formed body 420 includes a bottom portion (flat portion) 421 pinched between the panel punch 250 of the lower die 200 and the die center 340 of the upper die 300, a clamping portion (flange section) 422 disposed to be shifted in the first direction D1 from the bottom portion 421, disposed to be shifted in the radius outer direction Do, and pinched between the die core ring 230 and the upper piston 360, and a first inflection portion 423 disposed in the mold clearance CL1 between the tip portion 352A of the inner sleeve 350 and the tip portion 232A of the die core ring 230.

[0177] The first inflection portion 423 is configured to connect a convex surface portion 423A whose cross section is formed in a curved surface whose orientation of the curved surface is convex toward the internal space SP4 of the first formed body 420, and a concave surface portion 423B which is provided to be shifted to the clamping portion 422 side from the convex surface portion 423A and whose cross section is formed in a curved surface which is concave toward the internal space SP4. In the following description, an intermediate form to the first formed body 420 after the circular blank 410 deforms will be referred to as an intermediate formed body.

(Reverse Step)

[0178] As illustrated in FIG. 10A, the panel punch 250 of the lower die 200 and the upper die 300 are raised. In a process of raising the panel punch 250 of the lower die 200 and the upper die 300, the mold clearance CL1 between the tip portion 352A of the inner sleeve 350 and the tip portion 232A of the die core ring 230 is held.

[0179] As the panel punch 250 of the lower die 200 and the upper die 300 are raised, as illustrated in FIG. 12, a curved portion 424 having a U-shape in cross section is formed such that a portion protruding outward from the bottom portion 421 of the first formed body 420 pinched between the panel punch 250 and the die center 340 is folded to be convex downward.

[0180] As illustrated in FIG. 12, in the curved portion 424, in the mold clearance CL1 between the tip portion 352A of the inner sleeve 350 and the tip portion 232A of the die core ring 230, the first inflection portion 423 of the first formed body 420 is disposed by being pinched therebetween.

[0181] In the mold clearance CL1, a minute gap (space) CL0 that is not filled with the first inflection portion 423 of the first formed body 420 remains, for example, between the first inflection portion 423 and the sleeve concave surface portion 352C of the inner sleeve 350 or the second sleeve convex surface portion 352D. At a stage where the deep drawing step is completed, the minute gap (space) CL0 is formed.

[0182] A depth dimension h of the curved portion 424 gradually increases as the panel punch 250 is raised, and when the depth dimension h reaches a predetermined depth, as illustrated in FIGS. 10B and 13, the curved portion 424 abuts on a receiving surface 252A of a punch stepped portion 252 provided around the punch flat portion 251 of the panel punch 250. After abutting on the receiving surface 252A, the curved portion 424 is pushed against the receiving surface 252A, and moves (is raised) in the first direction D1.

[0183] In the reverse step, the curved portion 424 is pushed up by the receiving surface 252A of the panel punch 250, and as illustrated in FIG. 13, a portion of the first formed body 420 under processing is deformed to fill the minute gap (space) CL0. In this manner, the first inflection portion 423 is thickened and formed in the second inflection portion 425 (inflection portion 17).

[0184] In this way, the reverse step is completed when the panel punch 250 is moved (raised) in the first direction D1 to a predetermined position (height) until the minute gap (space) CL0 is filled with a portion of the first formed body 420. The curved portion 424 in this completion stage forms the countersink section 12, and the formed second inflection portion 425 forms the inflection portion 17.

[0185] After the reverse step is completed, the upper die 300 is raised, and the flat portion 341 of the die center 340 moves away from the bottom portion 421 of the first formed body 420 in the first direction D1.

[0186] Subsequently, the upper die 300 is further moved to a position above the lower die 200, and the completed can lid shell 10 is taken out.

[0187] For the formed can lid shell 10, in a lining step as a subsequent step, rubber for maintaining coating sealing performance is applied to the back surface SF2 of the can lid shell 10. A tear line for opening is formed and a tab for an opening operation is attached in a conversion step as a subsequent step, and the can lid is completed.

[0188] Furthermore, after the can body having a bottomed tubular shape is filled with the contained object and a gas (CO.sub.2 or N.sub.2), the can lid is attached in such a manner that the flange section (the flange section 14 and the convex type surrounding cross-sectional portion 134 of the chuck wall section 13) of the can lid shell 10 of the can lid is wound around the flange section of the can body, and a can product is completed.

[0189] In the can product using the can lid including the can lid shell 10 of the present embodiment, even when an internal pressure of the can product increases and an internal pressure acts such that a portion of the countersink section 12 of the can lid bulges outward of the can, the can product is formed by reinforcing the inflection portion 17 around the countersink section 12. Therefore, deformation of the countersink section 12 can be suppressed.

[0190] For example, even when the internal pressure acts to change an angle 23 open in a concave shape of the back surface of the second groove wall portion 123 illustrated in FIG. 1B, the thickness is formed to gradually increase from the first concave type surrounding cross-sectional portion 131 of the chuck wall section 13 toward the third convex type groove cross-sectional portion 123C and the second convex type groove cross-sectional portion 123B of the countersink section 12. Therefore, deformation can be suppressed. In this manner, buckling can be prevented.

Second Embodiment

[0191] As illustrated in FIGS. 14A and 14B, compared to the can lid shell 10 according to the first embodiment, a can lid shell 10A according to a second embodiment includes a plurality of thin portions (concave portions) 15 formed along the radial direction including the location of the inflection point on the front surface SF1 of the can lid shell 10A.

[0192] As illustrated in FIGS. 15, 16, and 17, the thin portion 15 is formed as a recessed location. In a plan view of the can lid shell 10A, the plurality of thin portions 15 are disposed at an equal angular interval around the center of the panel section 11. Furthermore, each of the thin portions 15 is formed in the same shape (rounded rectangular shape). In addition, each of the thin portions 15 is formed such that a dimension Da along the radius outer direction Do in a plan view is longer than a width dimension Db orthogonal to the dimension Da. In FIG. 15, a line along the radius outer direction Do is indicated by a two-dot chain line.

[0193] A location between the thin portions 15 forms a thick portion (convex portion) 16 formed to be thicker than the thin portion 15. Each of the thick portions 16 is formed such that a dimension along the radius outer direction Do in a plan view is longer than a width dimension orthogonal to the dimension. In other words, an interval between the respective thin portions 15 along the circumferential direction with respect to the central axis C is smaller than the dimension Da.

[0194] A one-dot chain line B11 in FIG. 15 indicates a boundary line formed by the fifth connection point p5, a one-dot chain line B12 indicates a boundary line formed by the sixth connection point p6, a one-dot chain line B13 indicates a boundary line formed by the seventh connection point p7 (inflection point), and a one-dot chain line B14 indicates a boundary line formed by the eighth connection point p8.

[0195] As illustrated in FIGS. 15 and 17, in each of the thin portions 15, one end portion 15A disposed on the center side is disposed on the fifth connection point p5 side with respect to the sixth connection point p6, and the other end portion 15B disposed on the flange section 14 side is disposed on the eighth connection point p8 with respect to the seventh connection point p7 (inflection point). For example, one end portion 15A is disposed between the fifth connection point p5 and the sixth connection point p6, and the other end portion 15B is disposed between the seventh connection point p7 and the eighth connection point p8.

[0196] In this way, the thin portion 15 is formed in the thickened portion 18, and is formed to particularly include at least a location from the seventh connection point p7 forming the inflection point to a position (sixth connection point p6) forming a maximum thickness.

[0197] In the thick portion 16 disposed between the thin portions 15, one end portion 16A disposed on the center side is disposed on the fifth connection point p5 side with respect to the sixth connection point p6, and the other end portion 16B disposed on the flange section 14 side is disposed on the eighth connection point p8 with respect to the seventh connection point p7 (inflection point). For example, one end portion 16A is disposed between the fifth connection point p5 and the sixth connection point p6, and the other end portion 16B is disposed between the seventh connection point p7 and the eighth connection point p8. That is, the thick portion 16 is formed in the thickened portion 18, and is formed to particularly include at least a location from the seventh connection point p7 forming the inflection point to a position (sixth connection point p6) forming the maximum thickness.

[0198] In this manner, in the thick portion 16, the thickness from the front surface SF1 to the back surface SF2 increases from the end portion 16B toward the sixth connection point p6, and further increases from the end portion 16A toward the sixth connection point p6. That is, the thickness of the thick portion 16 is thickest at the sixth connection point p6.

[0199] As illustrated in FIG. 16, the front surface SF1 in which the thin portion 15 and the thick portion 16 are alternately disposed in the circumferential direction of the can lid shell 10A is formed in a concave and convex shape.

[0200] The shapes of the thin portion 15 and the thick portion 16 are not limited to the illustrated example, and may be formed in an elliptical shape in a plan view as illustrated in FIG. 18. In addition, as illustrated in FIG. 19, an extending direction of the thin portion 15 or the thick portion 16 in a plan view may intersect the radius outer direction Do at a predetermined angle 15. Furthermore, both may extend in an arc shape in a plan view as illustrated in FIG. 20. In addition, in each drawing, an example of the extending direction of the thin portion 15 or the thick portion 16 and the radius outer direction Do is indicated by a two-dot chain line.

(Reforming Step)

[0201] The can lid shell 10A of the second embodiment can be manufactured by adding a reforming step to the can lid shell 10 of the first embodiment.

[0202] As illustrated in FIG. 21, a reforming device 40 for performing the reforming step includes a reforming die 41, a reforming punch 42, and a conveying unit 43 that conveys the can lid shell 10 between the reforming die 41 and the reforming punch 42. The reforming die 41 and the reforming punch 42 are provided in a press machine (not illustrated).

[0203] In the reforming step, as illustrated in a left half portion in FIG. 21, the can lid shell 10 is conveyed to a position above the reforming die 41 in a state of being supported by a belt 43A while the flange section (flange section 14 or the like) of the can lid shell 10 is hung on an edge of a hole 43B of the belt 43A of the conveying unit 43. After the can lid shell 10 is conveyed, as illustrated in a right half portion in FIG. 21, the reforming punch 42 is lowered, and the thickened portion 18 of the can lid shell 10A is pinched between the reforming punch 42 and the reforming die 41, thereby processing the thickened portion 18.

[0204] As illustrated in FIG. 22, a plurality of protruding projection portions 42B are formed on an abutting surface 42A of the reforming punch 42 which abuts on the thickened portion 18 of the can lid shell 10A. The projection portion 42B is pushed from the front surface SF1 into the thickened portion 18, and the thin portion 15 is formed. In addition, a location disposed between the thin portions 15 is formed as the thick portion 16.

[0205] When the plurality of projection portions 42B of the reforming punch 42 are pushed into the third convex type groove cross-sectional portion 123C (thickened portion 18), the back surface of the thickened portion 18 is supported by the reforming die 41, and the spring 44 that supports the reforming die 41 from below absorbs a portion of a load from the reforming punch 42.

(Operation)

[0206] In the thickened portion 18, each of the thick portions 16 is formed to extend from the fifth connection point p5 side to the eighth connection point p8 side, including at least a portion from the sixth connection point p6 to the seventh connection point p7, and deformation such as bending of the thickened portion 18 to the internal space SP1 side is prevented. In this way, mechanical strength of the thickened portion 18 (inflection portion 17) is further increased, and pressure resistance strength of the can lid shell 10A is improved.

[0207] The projection portion for forming the thin portion 15 or the thick portion 16 in the thickened portion 18 is not limited to a case where the projection portion is provided in the reforming punch 42. A recess forming the thin portion 15 may be formed on the back surface SF2 facing the outer space SP2 by using a plurality of projection portions provided on an abutting surface of the reforming die 41 which abuts on the thickened portion 18 of the can lid shell 10A. In this case as well, the same advantageous effect of improving the mechanical strength can be achieved.

(Forming Device 2A of First Modification Example)

[0208] In a forming device 2A of a first modification example illustrated in FIG. 23, compared to the forming device 2 of the first embodiment, a die core ring 500 of the lower die is different from the die core ring 230 of the first embodiment. In the tip portion of the die core ring 500 of the first modification example, an inner portion facing the tip portion of the inner sleeve 350 is configured to be movable with respect to an outer portion facing the upper piston 360. The same reference numerals will be assigned to the same configurations as those of the forming device 2 according to the first embodiment, and description thereof will be omitted.

[0209] As illustrated in FIG. 24, the die core ring 500 of the lower die includes a tubular first fixing portion (fixing portion) 510 and a second fixing portion (fixing portion) 520, a spring (biasing member) 530 held by the second fixing portion 520, and a tubular movable portion 540 which is provided inside the second fixing portion 520, of which a lower end is further supported by the spring 530, and which is provided to be movable along the central axis C.

[0210] The first fixing portion 510 includes a base end portion 511 fixed to the lower retainer 210, and a spring support portion 512 formed such that the thickness along the radial direction is smaller than the thickness of the base end portion 511 along the radial direction and extending from the base end portion 511. The base end portion 511 of the first fixing portion 510 protrudes in the radius outer direction Do from an outer peripheral surface of the spring support portion 512, and has a placement surface 511A along the radius outer direction Do. In the spring support portion 512, a concave portion 512A that accommodates a portion of the spring 530 is provided on the tip side. The concave portion 512A is open in a direction (first direction D1) opposite to the base end side.

[0211] As illustrated in FIGS. 24 and 25, the second fixing portion 520 includes a base end portion 521 placed on the placement surface 511A of the base end portion 511 of the first fixing portion 510 and fixed to the first fixing portion 510, and an upper piston facing portion 522 having a tip portion 522A is formed such that the thickness along the radial direction is smaller than the thickness of the base end portion 521 along the radial direction, extending from the base end portion 521, and facing the upper piston 360.

[0212] The upper piston facing portion 522 is formed in a tubular shape, the movable portion 540 slides on an inner peripheral surface, and the lower piston 260 slides on an outer peripheral surface. The tip portion 522A of the upper piston facing portion 522 has the same shape portion as the first convex surface portion 232B of the die core ring 230 in the forming device 2 of the first embodiment.

(Spring 530)

[0213] The spring 530 is provided coaxially with the first fixing portion 510, and expands and contracts along the axis (central axis C).

[0214] In a state where the movable portion 540 is placed, the lower portion of the spring 530 fits into the concave portion 512A of the spring support portion 512, and the remaining tip portion is disposed outside the concave portion 512A.

(Movable Portion 540)

[0215] The movable portion 540 is formed in a ring shape. The movable portion 540 includes a base end portion 541 supported by a tip portion of the spring 530, and an inner sleeve facing portion 542 having the smaller thickness than the base end portion 541 along the radial direction, extending in a tubular shape from the base end portion 541, and facing the inner sleeve 350.

[0216] The tip portion 542A of the inner sleeve facing portion 542 includes the same shape portion as the second convex surface portion 232E (corresponding to the lower die curved surface portion of the present invention) of the die core ring 230 in the forming device 2 of the first embodiment.

[0217] The movable portion 540 is moved along the central axis C in such a manner that the outer peripheral surface abuts on the inner peripheral surface of the upper piston facing portion 522 of the second fixing portion 520 and furthermore, the inner peripheral surface of the inner sleeve facing portion 542 abuts on the outer peripheral surface of the panel punch 250.

[0218] As illustrated in FIG. 25, the movable portion 540 is pushed by the spring 530. A movable-side stepped portion 543 formed on the outer side abuts on a fixing-side stepped portion 523 formed on the inner peripheral surface of the upper piston facing portion 522 of the second fixing portion 520, and the movable portion 540 is held at a position close to the tip portion 522A of the upper piston facing portion 522.

[0219] The outer side of the movable portion 540 has a first outer peripheral surface 540A adjacent to the lower end and disposed at a low position, and a second outer peripheral surface 540B disposed at a position higher than the first outer peripheral surface 540A. The radius of the first outer peripheral surface 540A is larger than the radius of the second outer peripheral surface 540B. The first outer peripheral surface 540A and the second outer peripheral surface 542A are connected to each other via the movable-side stepped surface 540C, thereby forming the movable-side stepped portion 543.

[0220] In the fixing-side stepped portion 523 of the upper piston facing portion 522 of the second fixing portion 520 is configured such that a first inner peripheral surface 522B abutting on the first outer peripheral surface 540A of the movable portion 540 and a second inner peripheral surface 522C abutting on the second outer peripheral surface 540B of the movable portion 540 are connected to each other via a fixing-side stepped surface 522D.

[0221] In a state where the movable portion 540 is pushed by the spring 530, the movable-side stepped portion 543 abuts on the fixing-side stepped portion 523, and the movable portion 540 is disposed at the highest position in a movement range thereof, as illustrated in FIG. 26, the second convex surface portion 232E of the tip portion 542A of the inner sleeve facing portion 542 is disposed to be shifted in the radius inner direction Di from the first convex surface portion 232B of the tip portion 522A of the upper piston facing portion 522, and is also disposed to be shifted in the second direction D2.

[0222] In addition, in a state where the movable portion 540 is disposed at the highest position, the tip portion 542A of the inner sleeve facing portion 542 is disposed close to the tip portion 352A of the inner sleeve 350, and a mold clearance CL2 for forming the inflection portion 17 is set.

[0223] Compared to the mold clearance CL1 of the forming device 2 of the first embodiment, the mold clearance CL2 of the forming device 2A of the first modification example is set to form the third convex type groove cross-sectional portion 123C of the inflection portion 17, and is formed in a small range from the first upper die connection point p31 to the second upper die connection point p32 of the inner sleeve 350. In this range, an interval along an imaginary straight line extending from the center C223 of the arc of the second convex surface portion 232E of the movable portion 540 is widened from the second upper die connection point p32 toward the first upper die connection point p31.

[0224] An upper end of an arc formed by the second convex surface portion 232E of the tip portion 542A of the movable portion 540 is set at a position P220 above the center C223 (on a vertical line), and the arc is formed from the third lower die connection point P23 to the position P220 of the upper end through the second lower die connection point P22.

[0225] In addition, in the tip portion 542A of the movable portion 540, a location extending in the radius outer direction Do from the position P220 of the upper end of the arc formed by the second convex surface portion 232E is disposed as a surface which is not in contact with the intermediate formed body. The tip portion 522A of the upper piston facing portion 522 includes a non-contact inner peripheral surface 522E which extends in the second direction D2 from a lower end P24 on the central axis C side of the first convex surface portion 232B and which is not in contact with the intermediate formed body.

(Manufacturing Method for Can Lid Shell 10)

[0226] As in the above-described embodiment, the manufacturing method for the can lid shell 10 includes the blanking step of punching the circular blank 410 from the raw plate made of the aluminum alloy, the deep drawing step of performing deep drawing on the circular blank 410 to form the first formed body 420 having a shallow bottom, and the reverse step of moving a bottom of the first formed body 420 upward (first direction D1) to form the countersink section.

[0227] Hereinafter, the deep drawing step and the reverse step will be described.

(Deep Drawing Step)

[0228] In the deep drawing step, first, as illustrated in FIG. 27A, the tip portion 352A of the inner sleeve 350 is lowered to a position close to the tip portion 542A of the movable portion 540 of the die core ring 500, and a portion of the circular blank 410 is pushed into the upper piston facing portion 522 of the die core ring 500. Thereafter, the circular blank 410 is pinched between the panel punch 250 and the die center 340, and is moved in the second direction D2 to perform deep drawing.

[0229] In a process of progressively performing deep drawing, the spacer 370 attached to the inner sleeve 350 comes into contact with the upper piston 360. In this manner, a possibility that the inner sleeve 350 is lowered independently of the upper piston 360 is suppressed.

[0230] When a central portion of the circular blank 410 pinched between the panel punch 250 and the die center 340 is lower than a lower end of the upper piston 360, a portion of the intermediate formed body 410A protruding from between the panel punch 250 and the die center 340 pushes the movable portion 540, and the movable portion 540 retreats (is lowered) to the spring 530 side.

[0231] After the intermediate formed body 410A abuts on the movable portion 540, an interval between the tip portion 542A of the movable portion 540 and the tip portion 352A of the inner sleeve 350 is gradually widened until the upper die 300 reaches the bottom dead center by using a press machine.

[0232] FIG. 27B illustrates a state where the deep drawing is completed, the upper die 300 is located at the bottom dead center, and the first formed body 420 is formed. In this case, an interval (refer to FIG. 25) between the movable-side stepped surface 540C of the movable portion 540 and the fixing-side stepped surface 522D of the second fixing portion 520 is the maximum, and is 0.25 mm, for example.

(Reverse Step)

[0233] In the reverse step, the bottom portion 421 of the first formed body 420 pinched between the panel punch 250 and the die center 340 is moved in a direction (first direction D1) opposite to a deep drawing direction (second direction D2) by the panel punch 250 and the panel punch piston 240 of the lower die 200. As the bottom portion 421 is moved, the curved portion 424 having a U-shape in cross section is formed such that a portion of the first formed body 420 protruding from between the panel punch 250 and the die center 340 is folded to be convex downward (refer to FIGS. 12 and 13).

[0234] As the panel punch 250 is raised, an internal depth dimension h along the central axis C of the curved portion 424 gradually increases. In addition, as the movable portion 540 is moved toward the tip portion 352A of the inner sleeve 350 when a load of the first formed body 420 pushing the movable portion 540 is reduced, an interval between the tip portion 542A of the movable portion 540 and the tip portion 352A of the inner sleeve 350 is gradually narrowed.

[0235] FIG. 27C illustrates a state where the movable-side stepped surface 540C abuts on the fixing-side stepped surface 522D during the reverse step, and the tip portion 542A of the movable portion 540 and the tip portion 352A of the inner sleeve 350 are closest to each other. In this state, as illustrated in an enlarged view in FIG. 28, the mold clearance CL2 for forming the inflection portion 17 is formed between the tip portion 542A of the movable portion 540 and the tip portion 352A of the inner sleeve 350.

[0236] When the mold clearance CL2 is formed, a minute gap CL0 is disposed between the sleeve concave surface portion 352C (corresponding to the upper die curved surface portion of the present invention) of the tip portion 352A of the inner sleeve 350 and the first inflection portion 423 of the first formed body 420. In addition, the spacer 370 attached to the inner sleeve 350 is in a state of being in contact with the upper piston 360 (refer to FIG. 23).

[0237] When the reverse step is further progressively performed in a state where the mold clearance CL2 is formed, the curved portion 424 is pushed up by the receiving surface 252A of the panel punch 250, and a portion of the first formed body 420 under processing is pushed into the mold clearance CL2. A portion of the first formed body 420 deforms to fill the minute gap (space) CL0. In this manner, the first inflection portion 423 is thickened and formed in the second inflection portion 425, and the reverse step is completed (FIG. 27D).

[0238] In the deep drawing step of the manufacturing method of the first modification example, the movable portion 540 is pushed down by the intermediate formed body 410A, and an interval between the inner sleeve facing portion 542 of the movable portion 540 and the inner sleeve 350 is widened. In this manner, deformation of the intermediate formed body 410A which is caused by contact with the inner sleeve facing portion 542 is reduced, and a possibility that the plate thickness is reduced when the deep drawing is performed can be suppressed.

[0239] In the can product using the can lid including the can lid shell 10 formed in this way, even when an internal pressure of the can product increases and an internal pressure acts such that a portion of the countersink section 12 of the can lid bulges outward of the can, the can product is formed by thickening the inflection portion 17 around the countersink section 12. Therefore, buckling in which a portion of the countersink section 12 deforms in an outward bulging shape can be suppressed.

(Forming Device 2B of Second Modification Example)

[0240] Compared to the forming device 2A of the first modification example, a forming device 2B of a second modification example illustrated in FIG. 29 includes a die core ring 1500, a spring (biasing member) 1530, and a lower piston 1260 instead of the die core ring 500, the spring 530, and the lower piston 260, and is configured as follows. While the deep drawing step is performed, the movable portion 1540 pushed against the intermediate formed body 410A and retreated to the first fixing portion 510 side is pushed up to the inner sleeve 350 side against pushing of the intermediate formed body 410A. The same reference numerals will be assigned to the same configurations as those of the forming devices 2 and 2A, and description thereof will be omitted.

[0241] As illustrated in FIG. 30, the die core ring 1500 includes the above-described first fixing portion 510, a block 550, a second fixing portion 1520 that supports the block, a spring 1530 set to have a smaller spring constant than the spring 530, and a movable portion 1540.

[0242] The second fixing portion 1520 includes the base end portion 521 and an upper piston facing portion 1522. The upper piston facing portion 1522 is different from the upper piston facing portion 522 of the above-described second fixing portion 520 in that the upper piston facing portion 1522 has a through-hole 525 through which the block 550 passes.

[0243] The through-hole 525 is formed by penetrating the upper piston facing portion 1522 to pass from the inside to the outside at a position lower than the fixing-side stepped surface 522D (refer to FIG. 25). A plurality of the through-holes 525 are formed around the central axis C of the second fixing portion 1520 at an equal angular interval, for example.

(Block 550)

[0244] As illustrated in FIG. 31, the block 550 includes an outer end portion 551 protruding to the lower piston 1260 side and an inner end portion 552 protruding to the movable portion 1540 side in a state of being disposed in the through-hole 525 of the upper piston facing portion 1522 of the second fixing portion 1520.

[0245] The outer end portion 551 includes an outer vertical surface 551A and an outer inclined surface 551B extending from an upper edge of the outer vertical surface 551A. In the outer inclined surface 551B, the radius (distance) from the central axis C decreases from an upper edge of the outer vertical surface 551A toward the first direction D1, and an inclination 51 with respect to the central axis C is set to be constant.

[0246] The inner end portion 552 includes an inner vertical surface 552A and an inner inclined surface 552B extending from an upper edge of the inner vertical surface 552A. In the inner inclined surface 552B, the radius (distance) from the central axis C increases from an upper edge of the inner vertical surface 552A toward the first direction D1, and an inclination 52 with respect to the central axis C is set to be constant. When angles 51 and 52 of the outer end portion 551 and the inner end portion 552 with respect to a horizontal plane thereof are compared, the angle 51 formed between the outer end portion 551 and the horizontal plane is set to be larger than the angle 52 formed between the inner end portion 552 and the horizontal plane.

(Lower Piston 1260)

[0247] The lower piston 1260 includes a piston body portion 261 and an extending portion 1262. The extending portion 1262 has a different shape of an inner peripheral surface, compared to the extending portion 262 of the lower piston 260.

[0248] As illustrated in FIG. 32, the extending portion 1262 includes a first inner peripheral surface 262C formed on the piston body 261 side, a second inner peripheral surface 262D provided on the tip portion 262A side and formed to have a smaller diameter than the first inner peripheral surface 262C, and an inner inclined surface 262E disposed between the first inner peripheral surface 262C and the second inner peripheral surface 262D.

[0249] In the inner inclined surface 262E, the radius (distance) from the central axis C decreases from an upper edge of the first inner peripheral surface 262C toward a lower edge of the second inner peripheral surface 262D, and the inclination with respect to the central axis C is set to be constant. An angle 62 of the inclination of the inner inclined surface 262E with respect to the central axis C is set to be equal to the angle 51 of the outer inclined surface 551B of the block 550. In addition, in lowering of the lower piston 1260, the outer inclined surface 551B of the block 550 is disposed on a movement locus of the inner inclined surface 262E.

[0250] The lower piston 1260 formed in this way is lowered by a predetermined distance along the central axis C. In this manner, the inner inclined surface 262E abuts on the outer inclined surface 551B of the block 550, and is further lowered. In this manner, the lower piston 1260 pushes the outer inclined surface 551B of the block 550, and the block 550 can be moved in the radius inner direction Di.

(Movable Portion 1540)

[0251] As illustrated in FIG. 33, the outer peripheral surface of the movable portion 1540 is formed to include a first outer peripheral surface 1540A rising from a peripheral edge of the lower surface, a second outer peripheral surface 540B formed to be shifted in the first direction D1 from the first outer peripheral surface 1540A, a third outer peripheral surface 540D disposed between the first outer peripheral surface 1540A and the second outer peripheral surface 540B, a movable-side stepped surface 540C disposed between the second outer peripheral surface 540B and the third outer peripheral surface 540D and forming the movable-side stepped portion 543 together with the second outer peripheral surface 540B and the third outer peripheral surface 540D, and an outer inclined surface 540E disposed between the first outer peripheral surface 1540A and the third outer peripheral surface 540D.

[0252] The radius of the first outer peripheral surface 1540A is set to be smaller than the radius of the second outer peripheral surface 540B, and the radius of the third outer peripheral surface 540D is set to be larger than the radius of the second outer peripheral surface 540B.

[0253] In the outer inclined surface 540E, the radius (distance) from the central axis C increases from an upper edge of the first outer peripheral surface 1540A toward a lower edge of the third outer peripheral surface 540D, and the inclination with respect to the central axis C is set to be constant. An angle 540 of the inclination of the third outer peripheral surface 540D with respect to the horizontal plane is set to be equal to an angle 52 of the inner inclined surface 552B of the block 550.

[0254] A dimension h31 along the central axis C from the movable-side stepped surface 540C of the movable portion 1540 to an upper edge of the outer inclined surface 540E is set to be larger than a dimension h32 (FIG. 30) along an axis from the fixing-side stepped surface 522D of the upper piston facing portion 1522 to an edge of the through-hole 525.

[0255] As illustrated in FIG. 30, in a state where the movable portion 1540 is not retreated to the spring 1530 side and the block 550 is not retreated to the through-hole 525 (state where the movable-side stepped surface 540C abuts on the fixing-side stepped surface 522D and the outer inclined surface 551B protrudes toward the lower piston 1260 while the outer inclined surface 551B is not in contact with the inner inclined surface 262E of the lower piston 1260), the outer inclined surface 540E of the movable portion 1540 and the inner inclined surface 552B of the block 550 are separated from each other, and the inner inclined surface 552B of the block 550 is disposed below the outer inclined surface 540E while a lower location of the surface protrudes from the through-hole 525 into the upper piston facing portion 1522.

[0256] A high location (outer peripheral side) of the outer inclined surface 540E of the movable portion 1540 is disposed above a low location (inner peripheral side) of the inner inclined surface 552B of the block 550.

[0257] In the deep drawing step, the movable portion 1540 is pushed against the intermediate formed body 410A, and is retreated to the spring 1530 side. However, the outer inclined surface 540E of the movable portion 1540 abuts on the inner inclined surface 552B of the block 550 to suppress the retreat of the movable portion 1540. Furthermore, in a state where the movable portion 1540 abuts on the block 550, the block 550 pushes the outer inclined surface 540E of the movable portion 1540 in the radius inner direction Di by using the inner inclined surface 552B. In this manner, the movable portion 1540 can be moved to the inner sleeve 350 side.

(Manufacturing Method for Can Lid Shell 10)

[0258] As in the above-described embodiment, the manufacturing method for the can lid shell 10 includes the blanking step of punching the circular blank 410A from the raw plate made of the aluminum alloy, the deep drawing step of performing the deep drawing on the circular blank 410 to form the first formed body 420 having a tray shape having a shallow bottom, and the reverse step of moving the flat portion of the bottom of the first formed body 420 to a mouth side disposed above to form the countersink section recessed around the flat portion.

[0259] Hereinafter, the deep drawing step and the reverse step will be described.

(Deep Drawing Step)

[0260] In the deep drawing step, first, as illustrated in FIG. 34A, the tip portion 352A of the inner sleeve 350 is lowered to a position close to the tip portion 542A of the movable portion 1540, and a portion of the circular blank 410 is pushed into the upper piston facing portion 1522 of the die core ring 1500. Thereafter, the circular blank 410 is pinched between the panel punch 250 and the die center 340, and is moved in the axial direction to perform the deep drawing.

[0261] When a central portion of the circular blank 410 pinched between the panel punch 250 and the die center 340 is lower than a lower end of the upper piston 360, a portion of the intermediate formed body 410A protruding from between the panel punch 250 and the die center 340 pushes the movable portion 1540, and the movable portion 1540 retreats (is lowered) to the spring 1530 side.

[0262] After the intermediate formed body 410A abuts on the movable portion 1540, an interval between the tip portion 542A of the movable portion 1540 and the tip portion 352A of the inner sleeve 350 gradually increases until the movable portion 1540 abuts on the block 550.

[0263] In addition, as the panel punch 250 and the die center 340 or the like are moved, the blank draw die 320 enters the inside of the lower die 200, and the lower piston 1260 is lowered by being pushed against the blank draw die 320. When the lower piston 1260 is lowered by a predetermined distance, the inner inclined surface 262E abuts on the outer inclined surface 551B of the block 550.

[0264] As illustrated in FIG. 34B, a timing at which the inner inclined surface 262E of the lower piston 1260 abuts on the outer inclined surface 551B of the block 550 and a timing at which the outer inclined surface 540E of the movable portion 1540 abuts on the inner inclined surface 552B of the block 550 are designed to be simultaneous. In a state where the movable portion 1540 abuts on the block 550 in this way, an interval between the movable-side stepped surface 540C and the fixing-side stepped surface 522D along the central axis C is 0.5 mm, for example.

[0265] In the forming device 2B, after the lower piston 1260 and the movable portion 1540 abut on the block 550, the lower piston 1260 is further lowered such that the block 550 retreats to the through-hole 525, and the inner end portion 552 is caused to further protrude into the upper piston facing portion 1522. In this manner, the block 550 pushes the movable portion 1540, and the movable portion 1540 moves in a direction in which the movable portion 1540 is closer to the inner sleeve 350.

[0266] In this way, the movement of the movable portion 1540 toward the inner sleeve 350 starts during the deep drawing, and an interval between the tip portion 542A of the movable portion 1540 and the tip portion 352A of the inner sleeve 350 is gradually narrowed until the panel punch 250 and the die center 340 complete the deep drawing step.

[0267] As illustrated in FIG. 34C, in a state where the upper die 300 reaches the bottom dead center, the tip portion 542A of the movable portion 1540 is disposed at a position closest to the tip portion 352A of the inner sleeve 350. In addition, in this close state, the mold clearance CL2 for forming a deformable portion 17 is formed. In addition, the movable-side stepped surface 540C of the movable portion 1540 abuts on the fixing-side stepped surface 522D of the upper piston facing portion 1522. The spacer 370 comes into contact with the upper piston 360 to form the mold clearance CL2 with the tip portion 542A of the inner sleeve facing portion 542 (between the inner sleeve 350 and the movable portion 1540).

(Reverse Step)

[0268] In the reverse step, the bottom portion 421 of the first formed body 420 pinched between the panel punch 250 and the die center 340 is moved in a direction opposite to the deep drawing direction by the panel punch 250 and the panel punch piston 240 of the lower die 200. As illustrated in FIG. 34D, as the bottom portion 421 of the first formed body 420 is moved, the curved portion 424 having a U-shape in cross section is formed such that a portion of the first formed body 420 protruding from between the panel punch 250 and the die center 340 is folded to be convex downward.

[0269] In a state where the curved portion 424 is disposed above the receiving surface 252A of the punch stepped portion 252, as illustrated in FIG. 28, the minute gap CL0 is disposed between the sleeve concave surface portion 352C of the tip portion 352A of the inner sleeve 350 and the first inflection portion 423 of the first formed body 420.

[0270] When the lower piston 1260 is raised together with the panel punch 250 and the inner inclined surface 262E is separated from the outer inclined surface 551B of the block 550, as illustrated in FIG. 34D, the block 550 is released from a force of causing the block 550 to retreat in the radius inner direction Di from the lower piston 1260, and the block 550 returns to an original position. The die core ring 1500 is provided with a block spring (not illustrated), and the block 550 can return to a protruding position from a retreated position by using the block spring.

[0271] Furthermore, when the reverse step is progressively performed, the curved portion 424 is pushed up by the receiving surface 252A of the panel punch 250, and a portion of the first formed body 420 under processing is pushed into the mold clearance CL2. A portion of the first formed body 420 deforms to fill the minute gap (space) CL0. In this manner, the first inflection portion 423 is thickened and formed in the second inflection portion, and the reverse step is completed (FIG. 34E).

[0272] In the deep drawing step of the manufacturing method of the second modification example, a force of the spring 1530 that holds the movable portion 1540 at a position where the movable portion 1540 is closest to the inner sleeve 350 to form the mold clearance CL2 is weaker than a force of the spring 530 of the forming device 2A of the first modification example. Therefore, when the deep drawing is performed, the movable portion 1540 is pushed against the deforming intermediate formed body 410A, and is easily retreated. In this manner, in the deep drawing process, a decrease in a plate pressure which is caused by the contact between the intermediate formed body 410A and the movable portion 1540 (inner sleeve facing portion 542) can be further suppressed.

[0273] Furthermore, while the deep drawing step is progressively performed, the lower piston 1260 is lowered, the block 550 is retreated, and the movable portion 1540 is moved toward the inner sleeve 350. In this manner, a portion of the intermediate formed body 410A in which a decrease in the thickness is suppressed is pinched between the movable portion 1540 (inner sleeve facing portion 542) and the inner sleeve 350, thereby forming the first inflection portion 423.

[0274] In this way, the decrease in plate pressure which is caused by the deep drawing is suppressed before the reverse step. In this manner, it is possible to prevent occurrence of deformation or distortion of the curved portion 424 folded and formed at a starting stage of the reverse step.

[0275] The present invention is not limited to the above description and the illustrated examples, and can be implemented. The manufacturing method of the first embodiment has been described with reference to the forming device (FIG. 4). However, a main point of the present invention is to form the mold clearance CL1 between upper and lower dies which face the first curved surface portion and the second curved surface portion. As long as the mold clearance can be formed, another forming device may be used without being limited to the forming device illustrated in FIG. 4. A ratio of the dimensions of the countersink section, the chuck wall section, and the flange section along the central axis C, a ratio of the dimensions of the panel section, the countersink section, the chuck wall section, and the flange section along the direction orthogonal to the central axis C, an expanding and opening angle around the center of each arc, and the like may be changed.

[0276] In addition, with regard to a cross-sectional structure of the can lid shell, in the above description and the drawings, a case has been described where in the third convex type groove cross-sectional portion 123C (corresponding to the first curved surface portion of the present invention), the first concave type surrounding cross-sectional portion 131 (corresponding to the second curved surface portion of the present invention), the second convex type groove cross-sectional portion 123B (corresponding to the third curved surface portion of the present invention), and the like, each surface forming the front surface SF1 or the back surface SF2 is formed as the arcs (true circular arc). However, in the third convex type groove cross-sectional portion 123C (corresponding to the first curved surface portion of the present invention), the first concave type surrounding cross-sectional portion 131 (corresponding to the second curved surface portion of the present invention), the second convex type groove cross-sectional portion 123B (corresponding to the third curved surface portion of the present invention), and the like, the surfaces forming the front surface SF1 or the back surface SF2 may be formed as a surface whose cross section is curved in a bow shape instead of the true circular arc.

[0277] The third convex type groove cross-sectional portion 123C (corresponding to the first curved surface portion of the present invention), the first concave type surrounding cross-sectional portion 131 (corresponding to the second curved surface portion of the present invention), and the second convex type groove cross-sectional portion 123B (corresponding to the third curved surface portion of the present invention) which have a curved surface whose cross section is curved in the bow shape in this way can also form the inflection portion 17 and the thickened portion 18. In this way, the inflection portion 17 and the thickened portion 18 are formed by the curved surface including the arc (true circular arc) or the surface curved in the bow shape, and pressure resistance strength of the can lid shell can be improved.

Examples

[0278] A can lid shell of a beverage can having the diameter of 200 is manufactured by using a raw plate in which both surfaces of an aluminum plate (thickness: 0.208 mm) formed of an aluminum alloy (5182) are coated with a modified epoxy-based paint (total thickness of both surfaces: 0.012 mm), and the pressure resistance strength is confirmed.

[0279] The can lid shell includes the panel section, the countersink section, the chuck wall section, and the flange section. In Example, the inflection point is disposed therebetween, and the inflection portion including an arc location that is concave to the internal space side in the chuck wall section and the arc location that is convex to the internal space side in the countersink section is thickened. In Comparative Example, the inflection portion is not thickened.

[0280] The can lid shell in Example is manufactured by using the forming device of the first embodiment. In this forming device, the mold clearance CL1 is set to 0.220 mm at the third upper die connection point P33 of the tip portion 352A of the inner sleeve 350 illustrated in FIGS. 6, to 0.234 mm at the second upper die connection point P32, and to 0.250 mm at the first upper die connection point P31, and an interval between the inner sleeve 350 and the die core ring 230 is widened from the third upper die connection point P33 toward the first upper die connection point P31.

[0281] In addition, the panel punch 250 of the lower die 200 of the forming device includes the punch stepped portion 252 having a stepped shape around the punch flat portion 251 on which the raw plate abuts. When the reverse step of forming the countersink section is performed, the curved portion 424 formed in the reverse step is pushed up by the receiving surface 252A of the punch stepped portion 252. A portion of the first formed body under processing is deformed and pushed into the mold clearance CL1. In this manner, the thickened inflection portion 425 is formed.

[0282] The can lid shell of Comparative Example is manufactured by using the forming device in the related art.

[0283] 50 samples are manufactured in each of Example of the invention and Comparative Example, the pressure resistance strength [psi] of each of the samples is measured, and an average value thereof (average pressure resistance strength) is calculated. In addition, in the inflection portions of the samples, the thickness at the inflection point between the arc location that is concave to the internal space side in the chuck wall section and the arc location that is convex to the internal space side in the countersink section is measured, and an increase ratio (plate thickness of circular blank after processing/plate thickness of circular blank before processing100) [%] when the measured thickness is compared with the thickness of the circular blank before processing is calculated. A result shows 1 [psi]=6, 894.76 [Pa].

[0284] Table 1 shows the pressure resistance strength, the thickness, and a ratio of the thickness.

TABLE-US-00001 TABLE 1 Average Pressure Plate Increase Ratio Resistance Thickness after of Plate Strength [psi] Processing [mm] Thickness Example of 106.7 0.24 109% Invention Comparative 98.2 0.22 100% Example

[0285] In the can lid shell of Example of the invention, the inflection portion is formed such that the thickness is increased by approximately 9% from the raw plate, and the average pressure resistance strength is configured to be as high as 106.7 [psi].

[0286] In Comparative Example, an increment of the thickness of the inflection portion with respect to the thickness of the raw plate cannot be confirmed. Average pressure resistance strength of 98.2 [psi] corresponds to strength of the can lid in the related art.

INDUSTRIAL APPLICABILITY

[0287] It is possible to provide a can lid shell that prevents buckling, a manufacturing method for the can lid shell, and a forming device.

REFERENCE SIGNS LIST

[0288] 2, 2A: forming device [0289] 10, 10A: can lid shell [0290] 11: panel section [0291] 12: countersink section [0292] 123B: second convex type groove cross-sectional portion (third curved surface portion) [0293] 123C: third convex type groove cross-sectional portion (first curved surface portion) [0294] 13: chuck wall section [0295] 131 first concave type surrounding cross-sectional portion (second curved surface portion) [0296] 132: second concave type surrounding cross-sectional portion [0297] 133: inclined surrounding cross-sectional portion [0298] 134: convex type surrounding cross-sectional portion [0299] 14: flange section [0300] 15: thin portion (concave portion) [0301] 16: thick portion (convex portion) [0302] 17: inflection portion [0303] 18: thickened portion [0304] 40: reforming device [0305] 200: lower die [0306] 210: lower retainer [0307] 220: cut edge portion [0308] 230: die core ring [0309] 232A: tip portion [0310] 232D: concave surface portion (first lower die curved surface portion) [0311] 232E: second convex surface portion (second lower die curved surface portion) (lower die curved surface portion) [0312] 240: panel punch piston [0313] 250: panel punch [0314] 260: lower piston [0315] 300: upper die [0316] 310: upper retainer [0317] 320: blank draw die [0318] 330: die center piston [0319] 340: die center [0320] 350: inner sleeve [0321] 351: piston body portion [0322] 352A: tip portion [0323] 352B: first sleeve convex surface portion [0324] 352C: sleeve concave surface portion (third upper die curved surface portion) (upper die curved surface portion) [0325] 352D: second sleeve convex surface portion (second upper die curved surface portion) [0326] 352E: third sleeve convex surface portion (first upper die curved surface portion) [0327] 352F: sleeve inclined surface portion [0328] 360: upper piston [0329] 362A: tip portion [0330] 370: spacer [0331] 400: raw plate [0332] 410: circular blank [0333] 410A: intermediate formed body [0334] 420: first formed body [0335] 421: bottom portion (flat portion) [0336] 422: clamping portion (flange section) [0337] 423: first inflection portion [0338] 425: second inflection portion [0339] 500: die core ring [0340] 510: first fixing portion (fixing portion) [0341] 520: second fixing portion (fixing portion) [0342] 522, 1522: upper piston facing portion [0343] 522A: tip portion [0344] 523: fixing-side stepped portion [0345] 530: spring (biasing member) [0346] 540: movable portion [0347] 542: inner sleeve facing portion [0348] 542A: tip portion [0349] 550: block [0350] 551B: outer inclined surface [0351] 552B: inner inclined surface [0352] 2B: forming device [0353] 1260: lower piston [0354] 262E: inner inclined surface [0355] 1500: die core ring [0356] 1520: second fixing portion (fixing portion) [0357] 525: through-hole [0358] 1530: spring (biasing member) [0359] 1540: movable portion [0360] 540E: outer inclined surface [0361] C: central axis [0362] CL1, CL2: mold clearance [0363] SF1: front surface [0364] SF2: back surface [0365] SP1: internal space