Plate forming method, can cover forming method and can bottom forming method

Abstract

Provided is a method for molding a plate material, in which unexpected deformation of the material due to relative advancement can be prevented, and the plate thickness of an annular protrusion can be increased in a large range including a necessary range by a simple manufacturing process. This method for molding a plate material comprises: a step for molding a specific plate part and a side wall part; a step for molding an annular bent portion connected to the side wall portion; a step for forming an annular protrusion in which the plate thickness is selectively increased by deforming at least the annular bent part; in the step of molding the annular protrusion, the annular bent portion is supported by a support member that is relatively movable in a second direction opposite to a first direction in which the molded annular protrusion protrudes, and a pressing force in the first direction is applied to the specific plate portion to generate a compressive stress in the second direction in the side wall portion. And at least a part of the plate material constituting the side wall portion is moved on the support surface of the support member, thereby forming an annular protrusion having a selectively increased plate thickness.

Description

TECHNICAL FIELD

[0001] The present application relates to a method of forming a plate material into, for example, a can lid, a can bottom, a method of forming a can lid, and a method of forming a can bottom. BACKGROUND

[0002] Metal can containers (metal cans) are required to reduce the thickness of a plate material as much as possible while maintaining the pressure resistance, for the sake of saving material resources and weight reduction. For example, a can lid or a can bottom can be subjected to so-called bending deformation due to an increase in the internal pressure of the can, and therefore, it is urgently required to take some effort to maintain the pressure resistance.

[0003] In the technology disclosed so far, in order to reduce the thickness of a plate material into, for example, a can lid, a can bottom, while maintaining the pressure resistance, an annular protrusion portion composed of an inner peripheral wall portion and a bending convex portion and a part of an outer peripheral wall portion is formed on the outer peripheral side of a central plate portion into which a lid surface, a bottom surface, and the like are formed, and the thickness of the bending convex portion thereof is increased.

[0004] For example, Patent Literature 1 describes a can lid including a center panel portion, a panel wall portion, a chuck wall radius portion, a chuck wall portion, and a curling portion, in which the thickness of the plate material is made smaller while the pressure resistance is improved by making the thickness t2 of the lower end of the panel wall portion larger than the thickness t1 of the center panel portion (t2 > t1). In addition, Patent Literature 1 describes a technique in which the thickness t3 of the chuck wall radius portion is made larger than the thickness t1 of the center panel portion (t3 > t1), and shows the necessary range for improving the pressure resistance. PRIOR ART DOCUMENTS PATENT LITERATURE

[0005] Patent Literature 1: Japanese Patent Application Laid-Open No. 2022-16093 SUMMARY PROBLEMS TO BE SOLVED BY THE INVENTION

[0006] However, in the method of manufacturing a can lid as described in Patent Literature 1, when forming an annular protrusion portion on a plate material using a conventional method, if the annular protrusion portion is formed using one stroke of an upper and lower mold, only the thickness of the plate material on the inner peripheral side of the annular protrusion portion is significantly increased, and the thickness of the plate material of the annular protrusion portion cannot be increased over a wide range. In addition, when the thickness of the plate material of the annular protrusion portion is increased over a wide range using a conventional method, the central plate portion must be relatively advanced (pushed) in multiple stages, and a mold having a different shape must be used each time, so that the manufacturing process is complicated.

[0007] In addition, by relative pushing (pushing), the sheet not only increases in thickness but also releases stress by deformation and flow of the material, but in the conventional method, the sheet material easily flows to the outer peripheral wall portion side, and it is difficult to maintain the shape required as, for example, a can lid, a can bottom, and the like. That is, the range in which relative pushing can be performed while maintaining the shape is narrow, and depending on the required performance, it is sometimes impossible to achieve sufficient increase in thickness of the sheet.

[0008] The present application aims to solve such technical problems. That is, the present application aims to provide a sheet forming method, a can lid forming method, and a can bottom forming method in which material unintended deformation caused by relative pushing is prevented, and a large range of increase in thickness of a ring-shaped protruding portion including a necessary range is achieved with a simple manufacturing process. Technical solution to solve the technical problem

[0009] The sheet forming method of the present application is characterized by comprising: a step of forming a specific sheet portion and a side wall portion; a step of forming a ring-shaped curved portion connected to the side wall portion; a step of forming a ring-shaped protruding portion in which the thickness is selectively increased by deforming at least the ring-shaped curved portion; and a step of forming the ring-shaped protruding portion in which, in the step of forming the ring-shaped protruding portion, the ring-shaped curved portion is supported by a support member that is relatively movable in a second direction opposite to a first direction in which the ring-shaped protruding portion is protruded, while a pushing force in the first direction is applied to the specific sheet portion, a compressive stress in the second direction is generated in the side wall portion, and at least a part of the sheet that constitutes the side wall portion is moved on a support surface of the support member, thereby forming the ring-shaped protruding portion in which the thickness is selectively increased.

[0010] The sheet forming method of the present application is characterized by comprising: a step of forming a central protruding portion composed of a central sheet portion and a side wall portion on the outer periphery side thereof in a sheet portion; a step of forming an outer peripheral curved portion on the outer periphery of the side wall portion; a step of forming a ring-shaped protruding portion in which the thickness is selectively increased by deforming at least the outer peripheral curved portion; and a step of forming the ring-shaped protruding portion in which, in the step of forming the ring-shaped protruding portion, the outer peripheral curved portion is supported by a support member that is relatively movable in a protruding direction of the central protruding portion, while a pushing force in the opposite direction of the protruding direction is applied to the central protruding portion, a compressive stress in the protruding direction is generated in the side wall portion, and at least a part of the sheet that constitutes the side wall portion is moved on a support surface of the support member, thereby forming the ring-shaped protruding portion in which the thickness is selectively increased. The can lid forming method of the present application is characterized by including the sheet forming method of the present application having such characteristics in a part of all steps. The can bottom forming method of the present application is characterized by including the sheet forming method of the present application having such characteristics in a part of all steps.

[0011] The plate material forming method of the present invention is characterized by including: a step of forming an outer peripheral plate portion by a side wall portion erected upward on the outer periphery side of a central plate portion while forming the central plate portion; a step of forming a ring-shaped curved portion on the inner periphery side of the side wall portion; a step of forming a ring-shaped protrusion portion that selectively increases the plate thickness by deforming at least the ring-shaped curved portion; and a step of forming the ring-shaped protrusion portion in which, while the ring-shaped curved portion is supported by a support member that is relatively movable in a second direction opposite to a first direction in which the ring-shaped protrusion portion is protruded, a pressing force in the first direction is applied to the outer peripheral plate portion, a compressive stress in the second direction is generated in the side wall portion, and at least a part of the plate material constituting the side wall portion is moved on a support surface of the support member. The can lid forming method of the present invention is characterized by including the plate material forming method of the present invention in a part of all steps. The can bottom forming method of the present invention is characterized by including the plate material forming method of the present invention in a part of all steps. Effects of the Invention

[0012] According to the present invention, it is possible to prevent an unintended deformation of a material caused by relative pushing (pressing) and to increase the plate thickness of a ring-shaped protrusion portion in a wide range including a necessary range with a simple manufacturing process. BRIEF DESCRIPTION OF DRAWINGS

[0013] [ Figure 1 ]Side view of the plate material having a ring-shaped protrusion portion in the first general mode.

[0014] [ Figure 2 ]Schematic flowchart of the forming process of the plate material having a ring-shaped protrusion portion in the first general mode.

[0015] [ Figure 3 ]Explanatory diagram of the forming process of the plate material having a ring-shaped protrusion portion in the first general mode.

[0016] [ Figure 4 ]Side view of the can lid in the first embodiment.

[0017] [ Figure 5 ]Schematic flowchart of the forming process of the can lid in the first embodiment.

[0018] [ Figure 6 ]First explanatory diagram of the forming process of the can lid in the first embodiment.

[0019] [ Figure 7 ]Second explanatory diagram of the forming process of the can lid in the first embodiment.

[0020] [ Figure 8Fig. 1 is a schematic side cross-sectional view of the general structure of a molding device used in the can lid molding process in the first embodiment.

[0021] [ Figure 9 ] Fig. 2 is a schematic view of the annular protrusion portion molding (sheet thickness increasing molding) process in the can lid molding process in the first embodiment.

[0022] [ Figure 10A ] Fig. 3 is a first schematic view of the annular protrusion portion molding (sheet thickness increasing molding) process in the can lid molding process in the first embodiment.

[0023] [ Figure 10B ] Fig. 4 is a second schematic view of the annular protrusion portion molding (sheet thickness increasing molding) process in the can lid molding process in the first embodiment.

[0024] [ Figure 11A ] Fig. 5 is a partial end view of the side end surface of the can lid preform in the first embodiment.

[0025] [ Figure 11B ] Fig. 6 is a partial end view of the side end surface of the can lid preform after the annular protrusion portion molding (sheet thickness increasing molding) process in the first embodiment.

[0026] [ Figure 12 ] Fig. 7 is a schematic view of the annular protrusion portion molding (sheet thickness increasing molding) process in the first embodiment example.

[0027] [ Figure 13 ] Fig. 8 is a schematic view of the rim height [mm] versus the relative support force [kN] in the first embodiment example.

[0028] [ Figure 14A ] Fig. 9 is a partial end view of the side end surface of the can lid preform after the annular protrusion portion molding (sheet thickness increasing molding) process in the first embodiment example.

[0029] [ Figure 14B ] Figure 14A Fig. 10 is a partial enlarged view of a portion of Fig. 9.

[0030] [ Figure 15 ] Fig. 11 is a schematic view of the sheet thickness [mm] of the measurement points A to F of the annular protrusion portion versus the relative support force [kN] at the time of the annular protrusion portion molding (sheet thickness increasing molding) process in the first embodiment example.

[0031] [ Figure 16 ] Fig. 12 is a schematic view of the can bottom molding process in the second embodiment.

[0032] [ Figure 17 ] Fig. 13 is a side view of the sheet material with an annular protrusion portion in the second embodiment.

[0033] [Figure 18 The second generalization method is shown in the schematic flowchart of the forming process of the sheet metal with annular protrusions.

[0034] [ Figure 19 The first explanatory diagram shows the forming process of the sheet metal with annular protrusions in the second generalization method.

[0035] [ Figure 20 The second explanatory diagram shows the forming process of a sheet material with annular protrusions in the second generalization method.

[0036] [ Figure 21 [Side view of the can lid in the third embodiment]

[0037] [ Figure 22 The third embodiment is a schematic flowchart of the can lid forming process.

[0038] [ Figure 23 The first explanatory diagram of the can lid forming process in the third embodiment.

[0039] [ Figure 24 The second explanatory diagram of the can lid forming process in the third embodiment.

[0040] [ Figure 25 The third illustration of the can lid forming process in the third embodiment.

[0041] [ Figure 26 [A schematic side sectional view of the forming device used in the can lid forming process in the third embodiment.]

[0042] [ Figure 27 The partial end view of the intermediate molded body used in Embodiments 1 to 5 of the third embodiment is a schematic diagram of the plate thickness [mm] measurement points a to v. (a) shows measurement points a to e and p to v. (b) is an enlarged view of the local area (the area within the box) including the wall radius shown in (a), showing measurement points f to o.

[0043] [ Figure 28 [Schematic diagram of plate thickness [mm] at each support force (counterhead hole holding force) [kgf] measured at measurement points a to v in Examples 1 to 5.]

[0044] [ Figure 29 The table below shows the values ​​of the cap diameter, shape, original plate thickness [mm], support force (counterhead hole holding force) [kgf], UD [mm], PH [mm], and pressure resistance [MPa] on the molded cans formed in Examples 6 to 8 and Comparative Example 1 in the third embodiment.

[0045] [ Figure 30[Third Embodiment] Explanation of the measurement locations of UD [mm] and PH [mm] on the molding cans formed in Examples 6 to 8 and Comparative Example 1.

[0046] [ Figure 31 The first explanatory diagram of the can lid forming process in the fourth embodiment.

[0047] [ Figure 32 The second explanatory diagram of the can lid forming process in the fourth embodiment.

[0048] [ Figure 33 The third explanatory diagram of the can lid forming process in the fourth embodiment.

[0049] [ Figure 34 The first explanatory diagram of the tank bottom forming process in the fifth embodiment.

[0050] [ Figure 35 The second explanatory diagram of the tank bottom forming process in the fifth embodiment.

[0051] [ Figure 36 [Partial end view of the intermediate molded body of the tank bottom used in the fifth embodiment, Example 9]

[0052] [ Figure 37 The partial end view of the final molded body of the tank bottom used in the fifth embodiment, Example 9, is a schematic diagram of the plate thickness [mm] measurement points w1 to w7.

[0053] [ Figure 38 The measurement results of Example 9 of the fifth implementation method are shown in the schematic table. Detailed Implementation

[0054] The embodiments of the present invention (this embodiment) will now be described with reference to the accompanying drawings. In the following description, the same symbols in each drawing represent the same functional parts, and repeated descriptions in each drawing are appropriately omitted. Furthermore, in the following description, "approximately" means "substantially". For example, "approximately circular" means not only "circular" (perfect circle), but also includes ellipses and similar shapes. [Main Methods]

[0055] The present invention provides a method for forming sheet metal in a primary manner (main manner) for forming sheet metal constituting, for example, can lids, can bottoms, etc. The method includes: forming a specific sheet metal portion and a sidewall portion connected thereto by an upper tool of the specific sheet metal portion applying pushing pressure in a first direction (downward direction); forming an annular curved portion connected to the sidewall portion; and forming an annular protrusion portion that selectively increases the sheet thickness by deforming at least the annular curved portion.

[0056] In the process of forming the annular protrusion, a support member (support tool for the annular bend) that can move relative to the annular protrusion in a second direction (upward direction) opposite to the first direction (downward direction) of the protrusion is used to support the annular bend. In this state, the upper tool of a specific plate is lowered to apply a pushing force in the first direction to the specific plate.

[0057] This generates compressive stress in the second direction in the sidewall portion, causing at least a portion of the sheet metal constituting the sidewall portion to move on the support surface of the support member (the support tool for the annular bend). Thus, in the sheet metal forming method of the main type, an annular protrusion with selectively increased sheet thickness is formed according to the portion that moves.

[0058] In this main method, the sheet metal forming process is not carried out in multiple stages and with different shaped molds each time. Instead, it can prevent accidental material deformation caused by relative pushing (pressing) with such a simple manufacturing process, while increasing the thickness of the annular protrusion over a wide range, including the necessary range. [First Summary Method]

[0059] The first generalized embodiment (first generalized method) of the present invention provides a method for forming a sheet metal, used for forming... Figure 1 The molded material 1 shown. The molded material 1 includes: a central panel portion (central plate portion) 12, which is located at approximately the center of the generally disc-shaped plate 11 and is a generally circular and generally flat surface; an annular protrusion 13 located on the outer periphery of the central panel portion (central plate portion) 12; and an outer peripheral panel portion (outer peripheral plate portion) 14 located on the outer periphery of the annular protrusion 13.

[0060] The sheet material 11 is composed of a metal-based material. There are no particular restrictions on the metal-based material; it can be a single metal material such as aluminum, aluminum alloy, or steel, or a cladding material of these metals, or a composite metal material in which surface treatment, coating, lamination, etc., have been applied to one or both sides of these metals.

[0061] A curved portion (curved end) 121 is formed on the outer edge (radially outer end) of the central panel portion (central plate portion) 12, and an inner peripheral wall portion 131 is formed extending downward in a generally straight line from the end (outer end) of the curved portion 121. A curved protrusion 132 is a curved portion, formed such that its inner peripheral end (inner end) connects to the lower end of the inner peripheral wall portion 131, and its outer peripheral end (outer end) connects to the outer peripheral wall portion 133. The outer peripheral wall portion 133 is formed to extend upward in a generally straight line from the upper outer peripheral end (outer end) of the curved protrusion 132, connecting to the curved portion (curved end) 141 of the outer peripheral panel portion (outer plate portion) 14. The annular protrusion 13 is composed of such an inner peripheral wall portion 131, a curved protrusion 132, and an outer peripheral wall portion 133.

[0062] The molding process (molding method) of the molded material 1 is as follows: Figure 2 As shown, it includes: a blank stamping process S1; a central protrusion forming process S2; an outer peripheral bending forming process S3; and an annular protrusion forming (plate thickness increase forming) process S4. In these forming processes (S1 to S4), the shape of the sheet metal 11 is as follows: Figure 3 The changes from state a1 to state a5 are shown, and the molding material 1 is in state a6.

[0063] In the blank stamping process S1, the shape varies depending on the final product (it can be, for example, elliptical, polygonal, etc.). For example, a stamping upper and lower tool (not shown) is used to stamp the sheet metal 11 into a roughly disc shape, and the sheet metal 11 is formed into a roughly disc shape. Figure 3 State a1).

[0064] In the central protrusion forming process S2, for example, a central drawing tool (not shown) used for drawing the approximately central portion of the approximately disc-shaped sheet 11 is used to fix the outer peripheral panel portion (outer peripheral panel portion) 25 of the approximately disc-shaped sheet 11, while simultaneously drawing its inner peripheral side, thereby... Figure 3 As shown in state a2, a central protrusion 22 is formed, which consists of a central panel portion (central panel portion) 23, which is equivalent to the "specific panel portion" described in the previous main mode, and a side wall portion 24 on its outer periphery.

[0065] In the peripheral bending forming process S3 and the annular protrusion forming (plate thickness increase forming) process S4, for example, the sheet metal 11 with the central protrusion 22 is formed using an upper tool U1 and a lower tool L1. The upper tool U1 includes: an annular upper outer tool U11; an upper central tool (upper tool for a specific plate portion) U12; and an annular sidewall guide tool U13 located between them. The lower tool L1 includes: an annular lower outer tool L11; a lower central tool L12; and an annular bending support tool (support member) L13 located between them.

[0066] In the peripheral bending forming process S3, for example, Figure 3 As shown in state a3, a sheet 11 with a central protrusion 22 formed by a central panel portion 23 and a side wall portion 24 is placed on the lower tool L1, and then the upper outer tool U11 is lowered. This clamps and fixes the outer peripheral panel portion (outer peripheral plate portion) 25 of the sheet 11 with the contact surfaces U11a of the upper outer tool U11 and L11a of the lower outer tool L11. This fixation of the outer peripheral panel portion (outer peripheral plate portion) 25 continues until the annular protrusion forming (sheet thickness increase forming) process S4 ends.

[0067] In this state, during the outer peripheral bending forming process S3, as follows: Figure 3As shown in states a3 and a4, the upper central tool U12 and the side wall guide tool U13 are lowered. At this time, by the descent of the upper central tool U12, its contact surface U12a and the contact surface L12a of the lower central tool L12 are clamped together by the center panel portion 23, pushing the lower central tool L12 down. Figure 3 (State a4). Furthermore, by lowering the sidewall guide tool U13, the outwardly downward-sloping sidewall portion 24 is positioned between the inner guide surface U13a of the sidewall guide tool U13 and the outer guide surface L12b of the lower central tool L12. With the sidewall guide tool U13 and the lower central tool L12 positioned around the sidewall portion 24, compressive stress applied to the sidewall portion 24 during the subsequent annular protrusion forming (plate thickness increase forming) process S4 can prevent buckling of the sidewall portion 24 due to this compressive stress.

[0068] The upper central tool U12 lowers its contact surface U12a to a height position close to the contact surface (support surface) L13a of the bending support tool (support member) L13. That is, the bending support tool (support member) L13 lowers in the protruding direction of the central protrusion 22 (upward direction), in relation to the rear-formed annular protrusion 13 (…). Figure 3 The protrusion (in state a5) can move relative to the protrusion in the second direction opposite to the first direction. The bending support tool L13 applies a supporting force to the sheet 11 on its contact surface (support surface) L13a in the direction of the protrusion (second direction). Therefore, by the descent of the upper central tool U12 and the side wall guide tool U13, an outer peripheral bend (annular bend) 26 is formed on the outer peripheral side of the side wall 24, which is a bend shape supported by the bending support tool L13 with the applied supporting force and along the shape of its contact surface L13a. In this way, a preform 11a having an outer peripheral bend (annular bend) 26 is formed from the sheet 11. Figure 3 State a4).

[0069] In the ring-shaped protrusion forming (plate thickness increase forming) process S4, for example, as Figure 3 As shown in states a4 and a5, the outer peripheral curved portion (annular curved portion) 26 of the preformed part 11a is supported by the contact surface (support surface) L13a of the bending support tool (support component) L13, while the central protrusion 22 is supported in the opposite direction (downward direction) to its protrusion direction (second direction), and the annular protrusion 13 formed later is supported. Figure 3 Apply pushing force in the first direction of the protrusion (state a5).

[0070] At this time, the upper central tool U12 descends continuously, pushing the lower central tool L12 down with its contact surface U12a. This applies a pushing force to the central panel portion (specific plate portion) 23 sandwiched between the contact surface U12a and the contact surface L12a of the lower central tool L12, advancing the central panel portion 23 downwards (in the first direction). Simultaneously, the sidewall guide tool U13 prevents the sidewall portion 24 from buckling due to compressive stress by positioning the sidewall portion 24 between its inner guide surface U13a and the contact surface L12b of the lower central tool L12. Thus, the upper central tool U12 applies a pushing force greater than the supporting force of the bending portion support tool L13 to the peripheral curved portion (annular curved portion) 26 through the sidewall portion 24.

[0071] Through the continuous descent of the central tool U12 and the sidewall guide tool U13, an annular protrusion is formed (plate thickness increase forming), deforming the outer peripheral curved portion (annular curved portion) 26, and generating compressive stress in the sidewall portion 24 in the protrusion direction (second direction). At least a portion constituting the sidewall portion 24 moves outward from the central protrusion 22 at the contact surface L13a of the curved portion support tool L13. Thus, an annular protrusion 13 with selectively increased plate thickness according to its moving portion is formed. Figure 3 State a5).

[0072] After forming the molded material 1 with the annular protrusion 13, the molded material 1 is removed from the upper tool U1 and the lower tool L1 to obtain... Figure 3 The molding material 1 is in state a6. On the molding material 1, the annular protrusion 13 increases the thickness of the plate over a wide range, including the curved protrusion 132 between the inner peripheral wall portion 131 and the outer peripheral wall portion 133. Figure 3 In the example of state a6, the outer peripheral panel (outer peripheral plate) 25 and the center panel (central plate) 23 are shown to be at approximately the same height, but this is not a limited example. The height positions of the outer peripheral panel 25 and the center panel 23 can be different as needed; for example, the height position of the outer peripheral panel 25 can be lower than the height position of the center panel 23.

[0073] Thus, in the forming method of the sheet metal 11 of the first general approach, the same device (upper and lower molds) with an upper tool U1 and a lower tool L1 is used to continuously (in one stroke) push (press) the central panel portion (specific plate portion) 23 relative to each other. That is to say, the forming method of this first general approach is not to use different molds of different shapes for the pushing in multiple stages, but in this way, the annular protrusion 13 with a large increase in plate thickness, including the necessary range, can be formed with a simple manufacturing process.

[0074] Instead of the example described herein, the same apparatus (upper and lower dies) can be used throughout the forming process of the forming material 1, from the blank stamping process S1 to the annular protrusion forming (plate thickness increase forming) process S4. Alternatively, a different apparatus (upper and lower dies) can be used from the blank stamping process S1 to the outer peripheral bending forming process S3, different from the apparatus (the apparatus with an upper tool U1 and a lower tool L1) used in the annular protrusion forming (plate thickness increase forming) process S4. In this case, a pre-formed part 11a is prepared in advance using this other apparatus, and this pre-formed part 11a is sequentially placed between the upper tool U1 and the lower tool L1.

[0075] Furthermore, in the example described in this first generalized approach, the upper central tool U12 is lowered relative to the bending support tool (support member) L13 as it approaches the bending support tool (support member) L13, but this is not a limitation. The bending support tool (support member) L13 is movable relative to the central protrusion 22 in the protrusion direction (upward direction, second direction). Therefore, instead of the example described here, the bending support tool (support member) L13 can also be raised relative to the upper central tool U12 as it approaches the upper central tool U12, thereby applying a pushing force toward the plate 11 on the contact surface (support surface) L13a in the protrusion direction (second direction).

[0076] At this time, the center panel portion 23 is sandwiched and fixed between the upper central tool U12 and the lower central tool L12. In this state, the lower outer tool L11 and the bending portion support tool (support member) L13 rise, pushing the upper outer tool U11 and the side wall portion guide tool U13 upward. As a result, an outer peripheral bending portion (annular bending portion) 26 is formed on the outer periphery of the side wall portion 24, which has a bending shape along the shape of the contact surface L13a of the bending portion support tool L13, and then an annular protrusion 13 is formed.

[0077] Next, the first and second embodiments of the present invention will be described. Descriptions of structures in the first and second embodiments that are identical to or mutually identical to the first generalized approach described above will be omitted. [First Implementation Method]

[0078] The first embodiment of the sheet metal forming method is to form it as a forming material. Figure 3 The example can lid 3 is shown in the image. The can lid 3 has: a central panel portion (central plate portion) 31; a panel wall portion (inner peripheral wall portion) 321; a retaining wall radius portion (curved protrusion) 322; a retaining wall portion composed of a first retaining wall portion (first outer peripheral wall portion) 323 and a second retaining wall portion (second outer peripheral wall portion) 33; and a curled portion 34. Here, the annular protrusion 32 is composed of the panel wall portion 321, the retaining wall radius portion 322, and the first retaining wall portion 323.

[0079] The central panel portion (central plate portion) 31 is located approximately in the center of the lid 3 and consists of a generally circular, generally flat surface. When the lid 3 is a retaining pull ring, the central panel portion 31 is provided with a pull ring for opening and scoring, etc.

[0080] A curved portion (curved end) 311 is formed on the outer edge (radially outer end) of the central panel portion 31, and a panel wall portion (inner peripheral wall portion) 321 is formed extending downward in a generally straight line from the end (outer end) of the curved portion 311. The retaining wall radius portion (curved protrusion) 322 is a curved portion, and its inner peripheral end (inner end) is formed to connect to the lower end of the panel wall portion 321, and its outer peripheral end (outer end) is connected to the first retaining wall portion (first outer peripheral wall portion) 323.

[0081] The first retaining wall portion (first outer peripheral wall portion) 323 extends upward in a generally straight line from the upper end (outer end) of the outer peripheral side of the retaining wall radius portion (bent protrusion) 322. The second retaining wall portion (second outer peripheral wall portion) 33 is shaped to extend upward in a generally straight line from the upper end (outer end) of the outer peripheral side of the first retaining wall portion 323, with its upper end connected to the curved portion of the curled portion 34.

[0082] The forming method of the can lid 3 includes, as a part of the overall process, the forming method of the sheet metal 11 described in the first generalized method above. That is, the forming method of the can lid 3 is as follows: Figure 4 As shown, it includes: blank stamping process S11; outer peripheral drawing process S12; central protrusion forming process S13; outer peripheral bending forming process S14; annular protrusion forming (plate thickness increase forming) process S15; and can lid shape forming process S16. In these forming processes (S11 to S16), as follows... Figure 5 , Figure 6 The states a11 to a18 show the shape changes of the sheet 41, forming the desired shape. Figure 7 The lid of can a19 is in state 3.

[0083] In the blank stamping process S11, for example, a stamping upper and lower tool (not shown) is used to stamp the sheet material 41 into a generally disc shape, and the sheet material 41 is formed into a generally disc shape. Figure 7 State a11).

[0084] The sheet material 41 is composed of a material mainly composed of metal. There are no particular restrictions on this metal material. It can be a single metal material such as aluminum, aluminum alloy, or steel, or a cladding material of these metals, or a composite metal material in which surface treatment, coating, lamination, etc. have been applied to one or both sides of these metals.

[0085] In the peripheral drawing process S12, for example, a peripheral drawing tool (not shown) is used to draw the peripheral portion of the generally disc-shaped sheet 41, and is fixed. Figure 6The inner circumferential plate-like portion of the outer periphery of the roughly disc-shaped sheet 41 shown in state a11 is simultaneously drawn on its outer periphery. Thus, as... Figure 6 As shown in state a12, an outer peripheral portion (side surface) 43 is formed on the outer peripheral side of the plate-shaped portion 42 of the plate 41, which extends in a direction approximately perpendicular to the plate-shaped portion 42 (downward direction).

[0086] In the central protrusion forming process S13, for example, for Figure 6 The sheet 41 in state a12 is used to draw the plate portion 42 approximately from its center using a central drawing tool (not shown). The outermost panel portion 420 of the plate portion 42, which is the outer periphery, is fixed in place, while the inner periphery is simultaneously drawn. Thus, as... Figure 6 As shown in state a13, a central protrusion 44 is formed on the inner circumferential side of the outer peripheral panel portion (outer peripheral panel portion) 421 of the sheet 41. This protrusion is composed of a central panel portion (central panel portion) 45, which corresponds to the "specific panel portion" described in the preceding main configuration, and a sidewall portion 46 on its outer periphery. The shape of the central panel portion (central panel portion) 45 is not particularly limited and can be as follows: Figure 6 The example has a central protrusion 44 in the protruding direction (with the rear-formed annular protrusion 32a). Figure 6 State a16) The first direction of the protrusion is opposite to the second direction) The gently protruding curved (dome) shape.

[0087] In the peripheral bending forming process S14 and the annular protrusion forming (plate thickness increase forming) process S15, the plate 41 with the central protrusion 44 is formed... Figure 6 (state a13), using, for example, Figure 8 The forming device M1, consisting of the upper tool U2 and the lower tool L2 shown, performs forming processing. As shown... Figure 8 and Figure 6 As shown in state a14, the upper tool U2 includes: an annular upper outer tool U21; an upper central tool (upper tool for a specific plate portion) U22; and an annular sidewall guide tool U23 located between them. The lower tool L2 includes: an annular lower outer tool L21; a lower central tool L22; and an annular curved portion support tool (support member) L23 located between them.

[0088] In addition, such as Figure 8 As shown, in the molding device M1, the upper tool U2 is equipped with buffer pins Ua1 and Ua2 connected to the cylinder, and the lower tool L2 is equipped with buffer pins La1 and La2 connected to the cylinder. In the upper tool U2, the upper central tool U22 and the side wall guide tool U23 can move in the vertical direction via the buffer pin Ua1 connected to the cylinder, and the upper outer tool U21 can move via the buffer pin Ua2 connected to the cylinder.

[0089] Additionally, in the lower tool L2, the lower central tool L22 and the bending support tool (support component) L23 are able to move vertically via the buffer pin La1 connected to the cylinder, and the lower outer tool L21 is able to move vertically via the buffer pin La2 connected to the cylinder. Alternatively, the forming device M1 can be equipped with elastic components such as spring components to replace the buffer pins Ua1, Ua2, La1, and La2 that are connected to the cylinder.

[0090] In the peripheral bending forming process S14, for example, Figure 6 As shown in state a14, the sheet 41 with the central protrusion 44 is placed on the lower tool L2, and then the upper outer tool U21 is lowered. Thus, the outer peripheral panel portion (outer peripheral plate portion) 421 of the sheet 41 is clamped and fixed by the contact surface U21a of the upper outer tool U21 and the contact surface L21a of the lower outer tool L21. This fixing of the outer peripheral panel portion (outer peripheral plate portion) 421 continues until the annular protrusion forming (sheet thickness increase forming) process S15 ends.

[0091] In this state, during the outer peripheral bending forming process S14, the upper central tool U22 and the side wall guide tool U23 are lowered. At this time, as... Figure 6 As shown in states a14 and a15, the lower central tool L22 is pushed down by the descent of the upper central tool U22, which clamps the central panel portion 45 between its contact surface U22a and contact surface L22a.

[0092] The upper central tool U22 lowers its contact surface U22a to a height position close to that of the contact surface (support surface) L23a of the bending support tool (support member) L23. That is, the bending support tool (support member) L23 can move relative to the central protrusion 44 in the protruding direction (upward direction, second direction). The bending support tool L23 applies a supporting force toward the protruding direction (second direction) to the sheet metal 41 on its contact surface (support surface) L23a. Therefore, by lowering the upper central tool U22 and the sidewall guide tool U23, an outer peripheral bend (annular bend) 47 is formed on the outer periphery of the sidewall 46, which is a bend shape supported by the bending support tool L23 with the applied supporting force and following the shape of its contact surface L23a. Thus, a preform 41a having the outer peripheral bend (annular bend) 47 is formed from the sheet metal 41. Figure 6 (State a15).

[0093] Annular protrusion forming (plate thickness increase forming) process S15 Figure 6In states a15 and a16, for example, the outer peripheral curved portion (annular curved portion) 47 of the preformed part 41a is supported by the contact surface (support surface) L23a of the bending support tool (support component) L23, while the central protrusion 44 is supported in the opposite direction to its protrusion direction (downward direction), forming the annular protrusion 32a. Figure 6 Apply pushing force to the first direction of the protrusion in state a16).

[0094] At this time, the upper central tool U22 descends continuously, pushing the lower central tool L22 down with its contact surface U22a. This applies a pushing force to the central panel portion (specific plate portion) 45 sandwiched between the contact surface U22a and the contact surface L22a of the lower central tool L22, advancing the central panel portion 45 downwards (in the first direction). Simultaneously, the sidewall guide tool U23 prevents the sidewall portion 24 from buckling due to compressive stress applied to the sidewall portion 46 by positioning the sidewall portion 46 between its inner guide surface U23a and the outer guide surface L22b of the lower central tool L22. Thus, the upper central tool U22 applies a pushing force to the peripheral curved portion (annular curved portion) 47 through the sidewall portion 46.

[0095] Through the continuous downward pressing (plate thickness increase molding) of the central tool U22 and the side wall guide tool U23, the central panel portion 45 is pushed downward, while the outer peripheral curved portion (annular curved portion) 47 is deformed. In addition, through this plate thickness increase molding, compressive stress in the protrusion direction (second direction) of the central protrusion 44 is generated in the side wall portion 46, and at least a portion constituting the side wall portion 46 moves outward of the central protrusion 44 on the contact surface L23a of the curved portion support tool L23.

[0096] Through this annular protrusion forming (plate thickness increase forming) process S15, an intermediate molded body 30 of the can lid (before can lid shape forming) is formed, which has an annular protrusion 32a with selectively increased plate thickness according to its moving portion. Figure 6 (State a16). The annular protrusion 32a increases the plate thickness over a wide area, including the wall radius (bent protrusion) 322a.

[0097] Thus, in the forming method of the sheet 41 of the first embodiment, the same device (upper and lower molds) having an upper tool U2 and a lower tool L2 is used to continuously (in one stroke) advance (push) the central panel portion 45 relative to each other. That is to say, the forming method of the first embodiment does not perform the advance in multiple stages and use molds of different shapes each time, but in this way, the annular protrusion 32a with a large increase in sheet thickness, including the necessary range, can be formed with a simple manufacturing process.

[0098] After forming the intermediate molded body 30 of the can lid (before the can lid shape is formed) with the annular protrusion 32a, the intermediate molded body 30 of the can lid is removed from the upper tool U2 and the lower tool L2.

[0099] The can lid shape forming process S16 is a process of reshaping the shape of the intermediate forming body 30 of the can lid into the shape of the can lid. The can lid shape forming process S16 has a process of forming a retaining wall part, which is composed of a first retaining wall part (first outer peripheral wall part) 323 and a second retaining wall part (second outer peripheral wall part) 33 as shown in the following state a19.

[0100] The can lid shape forming process S16 may further include at least one or two of the following processes, either in a different order or simultaneously with the above-mentioned wall forming process: the well-known process of forming a curled portion 34 on the outer periphery of the annular protrusion 32a (or the formed annular protrusion 32), which is not shown; and the process of forming the center panel portion (central panel portion) 45 into a desired shape, such as a generally flat surface.

[0101] In the can lid shape forming process S16, for example, Figure 7 As shown in state a17, the can lid forming apparatus M2, which has an upper tool U3 and a lower tool L3, is used to reshape the can lid intermediate forming body 30. The upper tool U3 includes: an upper outer tool U31; an upper central tool U32; and an annular processing tool U33 located between them. The lower tool L3 includes: an annular lower outer tool L31; and a lower central tool L32. In addition, the lower tool L3 has an annular protrusion support tool L33 located between the lower outer tool L31 and the lower central tool L32.

[0102] In the can lid forming process S16, it can be done as follows: Figure 7 As shown in state a17, a can lid intermediate forming body 30 (before can lid shape forming) is set on the lower tool L3, and then the upper outer tool U31, upper central tool U32, and processing tool U33 are lowered simultaneously, for example, to perform the can lid shape forming process S16. Alternatively, the timing of the descent of the upper outer tool U31, upper central tool U32, and processing tool U33 can be appropriately changed according to the shape of the can lid.

[0103] At this time, the annular protrusion 32a is formed into an annular protrusion 32 by the downward movement of the upper central tool U32. Figure 7In state a18), the annular protrusion 32a between the lower central tool L32 and the lower outer tool L31 is supported by the contact surface (support surface) L33a of the annular protrusion support tool L33, and the shape of the annular protrusion 32a follows the shape of the contact surface (support surface) L33a of the annular protrusion support tool L33. That is, at this time, the first retaining wall portion (first outer peripheral wall portion) 323 on the retaining wall portion is formed (please refer to state a19).

[0104] At this time, the upper outer tool U31 descends, and its contact surface U31a contacts the outer peripheral panel portion (outer peripheral plate portion) 421 on the contact surface (support surface) L31b of the lower outer tool L31, fixing the outer peripheral panel portion (outer peripheral plate portion) 421. In this state, the machining tool U33 descends, and the outer peripheral panel portion (outer peripheral plate portion) 421 is sandwiched between its contact surface U33a and the contact surface L31a, thereby forming a second retaining wall portion (second outer peripheral wall portion) 33 (please refer to state a19), which follows the shape of the lower outer tool L31 and the machining tool U33. In this way, a retaining wall portion composed of a first retaining wall portion (first outer peripheral wall portion) 323 and a second retaining wall portion (second outer peripheral wall portion) 33 on its outer periphery is formed (please refer to state a19).

[0105] Additionally, a curled portion 34 can be formed on the outer periphery of the cover at this time. At this time, a curling tool (not shown) can also be provided on the outer periphery of the lower outer tool L31 on the lower outer tool L31. As described above, with the outer peripheral panel portion (outer peripheral plate portion) 421 fixed, the machining tool U33 descends, thereby causing the outer peripheral panel portion (outer peripheral plate portion) 421, sandwiched between its contact surface U33a and contact surface L31a, to flow towards the outer periphery. In this state, the curled portion 34 is formed by the descending curling tool (not shown). Figure 7 State a18), which is the shape of the contact surface U31a of the upper outer tool U31 and the contact surface (not shown) of the curling tool (not shown).

[0106] Alternatively, the center panel portion (central plate portion) 45 can be shaped into a desired form, such as a generally flat surface. That is, the upper central tool U32 pushes the lower central tool L32 downwards through its contact surface U32a, and the center panel portion (central plate portion) 45 sandwiched between the contact surface U32a and the contact surface L32a of the lower central tool L32 is shaped into a generally flat center panel portion (central plate portion) 31. Figure 7 (State a18).

[0107] Thus, the reshaped can lid 3 is removed from the can lid forming device M2, resulting in... Figure 7The can lid 3 shown in state a19. The can lid 3 after being remolded in state a19 has the following shape: an annular protrusion 32, which is composed of a panel wall portion (inner peripheral wall portion) 321, a retaining wall radius portion (bent protrusion) 322, and a first retaining wall portion (first outer peripheral wall portion) 323, protrudes approximately perpendicularly to the extending direction of the center panel portion 31, which is shaped into a generally flat surface.

[0108] The situation described here is... Figure 7 The can lid shape forming process S16 includes both the process of forming the wall portion and the process of forming the center panel portion (central plate portion) 45 into a generally flat surface. However, these processes can also be performed in different sequences as different stages.

[0109] Here, the forming process S15 (forming the annular protrusion, increasing plate thickness) and the forming process S16 (forming the can lid shape) are further explained. (The upper tool is omitted from the drawing.) Figure 9 In this context, state b1 represents the shape of a portion of the preform 41a formed in the outer peripheral bending forming process S14. In this state b1, the center panel portion 45 is located above the uppermost position H of the outer peripheral panel portion (outer peripheral plate portion) 421, which has the highest vertical height.

[0110] In the ring-shaped protrusion forming (plate thickness increase forming) process S15, such as Figure 10A As shown, the outer peripheral panel portion (outer peripheral plate portion) 421 of the preform 41a is clamped by the upper outer tool U21 and the lower outer tool L21 to create a constrained portion K1, thus fixing the outer peripheral panel portion (outer peripheral plate portion) 421. Then, in this state, the contact surface (support surface) L23a of the bending support tool L23 applies an upward supporting force in the direction indicated by arrow Y101 to the outer peripheral bent portion (annular bent portion) 47. At this moment, the preform 41a having this outer peripheral bent portion (annular bent portion) 47 has Figure 11A The shape shown.

[0111] Then, in this state, the upper central tool U22 and the side wall guide tool U23 are lowered. At this time, as... Figure 9 As indicated by arrow Y91 in state b2, the outer peripheral curved portion (annular curved portion) 47 of the preform 41a is supported by a supporting force from below, while the central panel portion 45 of the preform 41a, as indicated by arrow Y92, is subjected to a pushing force from above. This pushing force in the vertical direction causes compressive stress to be generated in the outer peripheral curved portion (annular curved portion) 47.

[0112] Then, in the ring-shaped protrusion forming (plate thickness increase forming) process S15, the upper central tool U22 and the side wall guide tool U23 are further lowered. Through such continuous descent, as... Figure 9As shown in states b2 and b3, the downward pushing force (first direction) indicated by arrow Y92 (from the upper central tool U22) is greater than the upward supporting force (second direction) indicated by arrow Y91 (from the curved part support tool L23). As a result, the curved part support tool L23 is pushed down.

[0113] At this time, the downward pushing force from the upper central tool U22, indicated by arrow Y102, is further applied to the central panel portion 45 of the preform 41a, as shown in the image. Figure 10B As shown, the central panel portion 45 is pushed further downwards. Therefore, Figure 10A The outer peripheral curved portion (annular curved portion) 47 shown is deformed.

[0114] Then, as Figure 10B As shown, the downward pushing force indicated by arrow Y103 from the upper central tool U22 and the upward supporting force indicated by arrow Y104 from the curved support tool L23 exert force on the side wall portion 46 ( Figure 10A Compressive stress is applied to the central protrusion 44 in the protruding direction (upward direction, second direction). Thus, as this... Figure 10B As shown, the compressive stress causes a compressed portion K2 to appear, and at least a portion of the sidewall portion 46 is formed on the contact surface L23a of the bending support tool L23. Figure 10A As indicated by arrow Y105, it moves outward toward the central protrusion 44.

[0115] At this moment, it takes shape Figure 11B The molded body 30a-1 shown. The molded body 30a-1 has an annular protrusion 32a composed of a panel wall portion (inner peripheral wall portion) 321a, a retaining wall radius portion (bent protrusion) 322a, and a first retaining wall portion (first outer peripheral wall portion) 323a, and the plate thickness is increased over a large range including the retaining wall radius portion 322a.

[0116] In this way, it is formed Figure 9 The can lid intermediate molding body 30 shown in state b3 (before the can lid shape is formed). As shown in state b3, on the can lid intermediate molding body 30, the uppermost position of the center panel portion 45 is located below the uppermost position H of the outer peripheral panel portion (outer peripheral plate portion) 421.

[0117] Subsequently, in the can lid shape forming process S16, such as Figure 9As shown in state b4, downward pushing pressure, as indicated by arrows Y93 and Y94, is applied to the intermediate molded body 30 of the can lid for re-forming. Thus, as shown in state b4, the can lid 3 is obtained, which has: a molded annular protrusion 32 and a retaining wall portion; and a central panel portion (central plate portion) 31 composed of generally flat surfaces. On the can lid 3, the molded annular protrusion 32 has a significantly increased plate thickness, including the retaining wall radius portion 322.

[0118] Instead of the example described here, the same device (upper and lower molds) can be used throughout the forming process of the can lid 3, from the blank stamping process S11 to the annular protrusion forming (plate thickness increase forming) process S15. Alternatively, a different device (upper and lower molds) can be used from the blank stamping process S11 to the outer peripheral bending forming process S14, different from the device used in the annular protrusion forming (plate thickness increase forming) process S15 (the device having the aforementioned upper tool U2 and lower tool L2). In this case, a pre-formed part 41a is prepared in advance using this different device, and this pre-formed part 41a is placed between the upper tool U2 and the lower tool L2. [Example of the first embodiment]

[0119] Next, an embodiment of the first implementation method will be described. In this embodiment, as... Figure 12 As shown, the intermediate molded body 30A of the can lid was formed using the molding device M3 and a pre-formed preform (not shown). The preform was formed from a sheet of aluminum alloy (A5182P-H19, material thickness 0.235mm) with a coating film formed on both sides.

[0120] Figure 12 The forming device M3 has the same structure as the forming device M1 described above. That is, in the forming device M3, the upper tool U2A is equivalent to the upper tool U2, and the lower tool L2A is equivalent to the lower tool L2. Therefore, the upper outer tool U21A, the upper central tool U22A, and the sidewall guide tool U23A are equivalent to the upper outer tool U21, the upper central tool U22, and the sidewall guide tool U23, respectively. Furthermore, the lower outer tool L21A, the lower central tool L22A, and the bending support tool (support member) L23A are equivalent to the lower outer tool L21, the lower central tool L22, and the bending support tool (support member) L23, respectively.

[0121] The same process as the annular protrusion forming (plate thickness increase forming) step S15 described above was performed using the forming device M3. That is, as... Figure 12As shown, the upper outer tool U21A applies a downward pushing force (8.0kN) to the lower outer tool L21A as indicated by arrow Y202, thereby fixing the outer peripheral panel portion (outer peripheral plate portion) 421A which is clamped by the lower outer tool L21A and the upper outer tool U21A.

[0122] Then, in this state, the lower central tool L22A and the bending support tool (support member) L23A support force in the upward direction (second direction) indicated by arrows Y203 and Y204, simultaneously supporting the central panel portion 45A, which corresponds to the "specific plate portion" described in the previous main method, and the portion that becomes the annular protrusion 32A. At the same time, the upper central tool U22A and the side wall guide tool U23A continuously descend, continuously applying a downward pushing force in the downward direction (first direction) indicated by arrow Y201 (plate thickness increase molding). Through such plate thickness increase molding, the central panel portion 45A and the annular protrusion 32A are formed.

[0123] Thus, a can lid intermediate molded body 30A (before the can lid shape is formed) is obtained, which includes: a central panel portion 45A; an annular protrusion portion 32A, which has a retaining wall radius portion (bent protrusion) 322A on the outer periphery of the central panel portion 45A.

[0124] Figure 12 In this context, LH (Lip Height) is the vertical length [mm] of the outer peripheral panel portion (outer peripheral plate portion) 421A from the uppermost position to the outermost tip.

[0125] In this embodiment, the support force [kN] from the upward direction (second direction) indicated by arrow Y204 of the bending support tool (support component) L23A was different, and the plate thickness was increased by forming. Figure 13 Show the lip height in the middle. Figure 12 The measured values ​​of LH (mm) at various support forces (kN).

[0126] Figure 13 In the diagram, the black circles represent the lip height [mm]. For example... Figure 13 As shown, even with the increase in support force [kN], the value of lip height [mm] did not change significantly. This result means that increasing the plate thickness has no effect on the shape of the outer peripheral panel portion (outer peripheral plate portion) 421A.

[0127] Figure 14A A portion of the molded can lid of this embodiment is shown. Figure 14B Enlarged and shown Figure 14AThe annular protrusion 32A is shown, comprising a panel wall portion (inner peripheral wall portion) 321A, a retaining wall radius portion (bent protrusion portion) 322A, and a first retaining wall portion (first outer peripheral wall portion) 323A. Additionally, Figure 14B In the figure, A to F represent the measurement points of the plate thickness [mm] on the annular protrusion 32A.

[0128] In this embodiment, when the plate thickness is increased during forming, the arrow Y204 corresponding to the bending support tool (support component) L23A ( Figure 12 The values ​​of the upward supporting force [kN] shown in Figure 14 were measured at measurement points A to F on the annular protrusion 32A on the molded can lid. Figure 14B The thickness of the plate is [mm]. Figure 15 The measurement results were presented in the document.

[0129] According to this embodiment, such as Figure 15 As shown, by increasing the applied support force [kN], the plate thickness [mm] can be increased by 0.235 mm over a wide range of measuring points A to F on the annular protrusion 32A compared to the original plate thickness. In this embodiment, especially when the support force is at its maximum of 8.9 kN, the plate thickness is significantly increased over a wide range of measuring points A to F compared to the original plate thickness. Furthermore, as... Figure 15 As shown, the plate thickness can be sufficiently increased at measurement points B to E within the radius (bent protrusion) 322A of the card wall. Thus, in this embodiment, a single forming process can increase the plate thickness not only on the inner circumference of the annular protrusion but also on the necessary range including the outer circumference of the annular protrusion. [Second Implementation]

[0130] The second embodiment of the sheet metal forming method involves forming the sheet metal as a forming material. Figure 16 The tank bottom 6 is shown in state a27. The forming method of the tank bottom 6 includes, as a part of the overall process, the forming method of the sheet metal 11 described in the first generalized method above.

[0131] The forming method of the can bottom 6 includes: as shown above Figure 5 The same process, that is Figure 5 The billet stamping process S11 is shown; the outer peripheral drawing process S12 is shown; the central protrusion forming process S13 is shown; the outer peripheral bending forming process S14 is shown; the annular protrusion forming (plate thickness increase forming) process S15 is shown; and the can bottom shape forming process S16 is shown. In these forming processes (S11 to S16), as follows... Figure 16 The shape of the sheet 51 is changed from state a21 to state a26, and the bottom of the tank 6 in state a27 is formed by re-molding.

[0132] In the blank stamping process S11 of the can bottom 6 forming process, for example, a stamping upper and lower tool (not shown) is used to stamp the sheet metal 51 to be processed into a generally disc shape, and the sheet metal 51 is formed into a generally disc shape. Figure 16 State a21).

[0133] In the outer peripheral drawing process S12 of the forming process of the can bottom 6, for example, an outer peripheral drawing tool (not shown) is used to draw the outer peripheral portion of the generally disc-shaped plate 51, and is fixed. Figure 16 The inner plate-shaped portion of the outer periphery of the roughly disc-shaped sheet 51 shown in state a21 is simultaneously drawn on the outer periphery. Thus, as... Figure 16 As shown in state a22, an outer peripheral portion (side surface) 53 is formed on the outer peripheral side of the plate-shaped portion 52 of the plate 51, which extends in a direction approximately perpendicular to the plate-shaped portion 52 (upward direction).

[0134] In the central protrusion forming process S13 of the forming process of the can bottom 6, for example, for Figure 16 In state a22, using a central drawing tool (not shown) for drawing approximately the central portion of the sheet portion 52, the outer panel portion (outer panel portion) 521 of the sheet portion 52 is shaped into a gently protruding annular curved bottom 522 in its approximately vertical (downward) direction and fixed. In this state, its inner circumferential side is drawn. Thus, as Figure 16 As shown in state a23, a central protrusion 54 is formed, which consists of a dome-shaped panel portion (central plate portion) 55, equivalent to the "specific plate portion" described in the preceding main mode, and a sidewall portion 56 on its outer periphery. The dome-shaped panel portion (central plate portion) 55 has a dome shape, and its protrusion direction (upward direction) in the central protrusion 54 is similar to that of the subsequently formed annular protrusion 62a. Figure 16 The state a26) is a gentle protrusion in the opposite direction of the first direction of the protrusion.

[0135] In the peripheral bending forming process S14 and the annular protrusion forming (plate thickness increase forming) process S15, for example, for the plate 51 with the central protrusion 54 formed ( Figure 16 In state a23), forming is performed using a forming device with an upper tool U4 and a lower tool L4. For example... Figure 16 As shown in state a24, the upper tool U4 includes: an annular upper outer tool U41; an upper central tool (upper tool of a specific plate portion) U42; and an annular sidewall guide tool U43 located between them. The lower tool L4 includes: an annular lower outer tool L41; and an annular curved portion support tool (support member) L42 located on its inner circumference.

[0136] In the peripheral bending forming process S14, for example, Figure 16 As shown in state a24, the sheet 51 with the central protrusion 54 is placed on the lower tool L4, and then the upper outer tool U41 is lowered. This clamps and fixes the annular curved bottom (corresponding to the outer peripheral panel portion) 522 of the sheet 51 with the contact surfaces U41a of the upper outer tool U41 and L41a of the lower outer tool L41. This fixing of the annular curved bottom 522 continues until the annular protrusion forming (sheet thickness increase forming) process S15 ends.

[0137] Simultaneously, in the outer peripheral bending forming process S14, the upper central tool U42 and the side wall guide tool U43 are lowered. At this time, as... Figure 16 As shown in state a24, due to the descent of the upper central tool U42, its contact surface U42a contacts the dome panel portion 55.

[0138] The upper central tool U42 lowers its contact surface U42a to a height position close to that of the contact surface (support surface) L42a of the bending support tool (support member) L42. That is, the bending support tool (support member) L42 can move relative to the central protrusion 54 in the protruding direction (upward direction, second direction). When the plate 51 is present on its contact surface (support surface) L42a, the bending support tool L42 applies a supporting force toward the plate 51 in the protruding direction (second direction). Therefore, by lowering the upper central tool U42 and the sidewall guide tool U43, an outer peripheral bend (annular bend) 57 is formed on the outer periphery of the sidewall 56, which is a bend shape supported by the bending support tool L42 with the applied supporting force and following the shape of its contact surface L42a. Thus, a preform 51a with an outer peripheral bend (annular bend) 57 is formed from the plate 51. Figure 16 State a25).

[0139] Annular protrusion forming (plate thickness increase forming) process S15 Figure 16 In states a25 and a26, for example, the outer peripheral curved portion (annular curved portion) 57 of the preformed part 51a is supported by the contact surface (support surface) L42a of the bending support tool (support member) L42, while a pushing force is applied to the central protrusion 54 composed of the dome panel portion 55 and the side wall portion 56 in the opposite direction to its protrusion direction (downward direction, first direction).

[0140] At this time, the upper central tool U42 pushes the dome panel portion 55 down continuously with its contact surface U42a, thereby applying a pushing force to the dome panel portion (specific plate portion) 55, causing the dome panel portion 55 to descend, and applying a pushing force to the outer peripheral curved portion (annular curved portion) 57 located between the tip contact portion U43a and the contact surface L42a.

[0141] Through the continuous downward pressing (plate thickness increase molding) of the central tool U42 and the side wall guide tool U43, the dome panel portion 55 is pushed downward, while the outer peripheral curved portion (annular curved portion) 57 is deformed. In addition, through this plate thickness increase molding, compressive stress in the protrusion direction (second direction) of the central protrusion 54 is generated in the side wall portion 56, and at least a portion constituting the side wall portion 56 moves outward of the central protrusion 54 on the contact surface L42a of the curved portion support tool L42.

[0142] Through this annular protrusion forming (plate thickness increase forming) process S15, a can bottom intermediate molded body 60 (before can bottom shape forming) is formed, having an annular protrusion 62a with selectively increased plate thickness according to its moving portion. Figure 16 (State a26). The annular protrusion 62a increases the plate thickness over a large area, including the so-called bottom radius 622a. Then, the formed intermediate molded body 60 of the can bottom (before the can bottom shape is formed) is removed from the upper tool U4 and the lower tool L4.

[0143] Thus, in the forming method of the sheet 51 of the second embodiment, the same device (upper and lower molds) having an upper tool U4 and a lower tool L4 is used to continuously (in one stroke) push (press) the dome panel portion (specific plate portion) 55 relative to each other. That is to say, the forming method of this second embodiment is not performed in multiple stages and with different shaped molds each time, but in this way, the annular protrusion 62a with increased plate thickness within the necessary range can be formed with a simple manufacturing process.

[0144] The can bottom shaping process S16 is a process of reshaping the shape of the intermediate molding body 60 of the can bottom into the shape of the can bottom as needed. This process includes shaping the annular protrusion 62 of the can bottom. After the reshaping in the can bottom shaping process S16, the can bottom 6 (not shown) is obtained from the reshaping device (not shown). Figure 16 (State a27).

[0145] The bottom-forming process S16 can be carried out using methods that are well-known in the past, such as rotary rollers and compression molding.

[0146] In addition, in the second embodiment, especially when an inner coating process is required, it is best to perform the process before the can lid shaping process S16.

[0147] The bottom 6 of the can in state a27 has: a dome-shaped panel portion (central panel portion) 61; a dome-shaped panel wall portion (inner peripheral wall portion) 621; a bottom radius portion (curved protrusion) 622; a lower part of the bell portion (first outer peripheral wall portion) 623; and a bell portion (second outer peripheral wall portion) 63. Here, the dome-shaped panel wall portion 621, the bottom radius portion 622, and the lower part of the bell portion 623 constitute the annular protrusion 62 of the bottom of the can. The annular protrusion 62 of the bottom of the can has a slightly inwardly inclined shape through remolding, and the plate thickness is increased within the necessary range, including the bottom radius portion 622.

[0148] The bottom-forming process S16 can further include, as needed, a process of forming the dome-shaped panel (central panel) 55 into a desired shape, such as a shape other than a sphere, such as a roughly ellipsoidal surface, a roughly conical surface, or a roughly flat surface. In this case, as a re-forming process... Figure 16 The process of shaping the bottom of the can 60 in state a26, the bottom shape forming process S16 may simultaneously or sequentially include: the process of shaping the shape of the annular protrusion 62 of the bottom of the can; and the process of shaping the dome panel (central panel) 55 into, for example, a generally flat surface. [Second Summary Method]

[0149] The second generalized embodiment (second generalized method) of the present invention describes a method for forming a sheet metal, such as... Figure 17 The image shows a molded profile 1E. The molded profile 1E is formed from a generally disc-shaped sheet 11E. The molded profile 1E has: a central panel portion (central plate portion) 12E, which is located approximately in the center of the sheet 11E and is a generally circular and generally flat surface; an annular protrusion 13E located on the outer periphery of the central panel portion (central plate portion) 12E; and an outer peripheral panel portion (outer peripheral plate portion) 14E located on the outer periphery of the annular protrusion 13E.

[0150] Sheet 11E is composed of a material primarily composed of metal. There are no particular restrictions on the material primarily composed of metal; it can be a single metal material such as aluminum, aluminum alloy, or steel, or a cladding material of these metals, or a composite metal material in which surface treatment, coating (including paints such as lubricants), or lamination have been applied to one or both sides of these metals.

[0151] A curved end portion 121E is formed at the radially outer end (outer edge) of the central panel portion (central plate portion) 12E, and an inner peripheral wall portion 131E is formed extending downward in a generally linear manner from the outer end (terminal end) of the curved end portion 121E. A curved protrusion 132E is a curved portion, formed such that its inner end (inner peripheral side end) connects to the lower end of the inner peripheral wall portion 131E, and its outer end (outer peripheral side end) connects to the lower end of the outer peripheral wall portion 133E. The outer peripheral wall portion 133E is formed to extend upward in a generally linear manner from the outer end (outer peripheral side upper end) of the curved protrusion 132E, connecting to a curved end portion (curved portion) 141E formed as the radially inward end of the outer peripheral panel portion (outer peripheral plate portion) 14E. The annular protrusion 13E is composed of such an inner peripheral wall portion 131E, a curved protrusion 132E, and an outer peripheral wall portion 133E.

[0152] The forming process (forming method) of the sheet material 1E of the forming material 1E is as follows: Figure 18 As shown, it includes: a blank stamping process S31; a central-outer periphery plate forming process S32; an annular bending section forming process S33; and an annular protrusion forming (plate thickness increase forming) process S34. In these forming processes (S31 to S34), the shape of the sheet metal 11E is as follows: Figure 19 and Figure 20 The changes from state m1 to state m6 are shown in the molding process. Figure 20 The state of the formed material 1E is m7.

[0153] In the blank stamping process S31, the shape varies depending on the final product (it can be, for example, elliptical, polygonal, etc.). For example, a stamping upper and lower tool (not shown) is used to stamp the sheet metal 11E into a roughly disc shape, and the sheet metal 11E is formed into a roughly disc shape. Figure 19 (state m1).

[0154] In the central-outer peripheral plate forming process S32, for example, a central drawing tool (not shown) used for drawing the approximately central portion of the approximately disc-shaped sheet 11E is used to apply a blank holder force to the outer peripheral side portion (the rear outer peripheral panel portion (outer peripheral plate portion) 21E) of the approximately disc-shaped sheet 11E, and in this state, the inner peripheral side is drawn. Thus, Figure 19 As shown in state m2, while forming the central panel portion (central plate portion) 22E, the outer peripheral panel portion (outer peripheral plate portion) 21E, which is equivalent to the "specific plate portion" described in the previous main mode, is formed by the side wall portion 23E that is erected upward on the outer periphery of the central panel portion 22E.

[0155] In the annular bending part forming process S33 and the annular protrusion forming (plate thickness increase forming) process S34, the plate 11E with the center panel part (central plate part) 22E and the outer peripheral panel part (outer peripheral plate part) 21E is formed.Figure 19 The forming process is performed using an upper tool U5 located on its upper side and a lower tool L5 located on its lower side (state m3). The upper tool U5 includes: an annular upper outer tool (upper tool for a specific plate portion) U51; an upper central tool U52; and an annular guide tool U53 located between them. The lower tool L5 includes: an annular lower outer tool L51; a lower central tool L52; and an annular support tool (support member) L53 located between them.

[0156] In the annular bending forming process S33, the sheet metal 11E, which has a central panel portion 22E and an outer peripheral panel portion 21E formed, is placed on the lower tool L5. Figure 19 (State m3). Then, the center panel portion (center panel portion) 22E of the plate 11E is clamped and fixed by the contact surface U52a of the upper center tool U52 and the contact surface L52a of the lower center tool L52. Figure 19 (State m4). The center panel portion 22E is fixed until the annular protrusion forming (plate thickness increase forming) process S34 ends.

[0157] In this state, during the ring-shaped bending part forming process S33, as follows: Figure 19 state m4 and Figure 20 As shown in state m5, the annular protrusion 13E, which is formed later, is applied by the upper outer tool U51. Figure 20 The first direction (downward direction) of the protrusion in state m6) is the pushing force. At this time, the outer peripheral plate part (outer peripheral plate part) 21E is clamped between the contact surface U51a of the upper outer tool U51 and the contact surface L51a of the lower outer tool L51, and at the same time the upper outer tool U51 pushes the lower outer tool L51 down.

[0158] U53 guide tool, for example Figure 19 state m4, Figure 20 As shown in states m5 and m6, the material can be either lowered or not lowered. In either case, the guide tool U53 and the lower outer tool L51 are located around the sidewall portion 23E. Therefore, when compressive stress is applied to the sidewall portion 23E in the subsequent annular protrusion forming (plate thickness increase forming) process S34, it is possible to prevent the sidewall portion 23E from buckling due to this compressive stress.

[0159] In the annular bend forming process S33, the upper outer tool U51 pushes down the lower outer tool L51 so that the height position of its contact surface U51a is close to the height position of the contact surface (support surface) L53a of the support tool (support member) L53. That is, the support tool L53 can move relative to the lower outer tool in a second direction (upward direction) opposite to the first direction (downward direction). The support tool L53 applies a supporting force toward the plate 11E on its contact surface (support surface) L53a in the second direction (upward direction). Therefore, by pushing down the lower outer tool L51 with the upper outer tool U51, an annular bend 24E is formed on the inner circumference of the sidewall 23E, which is a bend shape along the shape of its contact surface L53a supported by the support tool L53 to which the supporting force is applied. The plate 11E with such an annular bend 24E is used as a preform 11Ea. Figure 20 (state m5).

[0160] In the ring-shaped protrusion forming (plate thickness increase forming) process S34, for example, as Figure 20 As shown in states m5 and m6, the annular curved portion 24E of the preformed part 11Ea is supported by the contact surface (support surface) L53a of the support tool (support component) L53 (by a support force in the second direction (upward direction)), while a pushing force is applied to the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 21E in the first direction (downward direction).

[0161] At this time, the upper outer tool U51 continuously applies a pushing force in the first direction (downward direction) to the lower outer tool L51 by pushing it down with its contact surface U51a. That is, the upper outer tool U51 continuously applies a pushing force to the outer peripheral panel portion (outer peripheral plate portion) 21E sandwiched between the contact surface U51a and the contact surface L51a of the lower outer tool L51, advancing the outer peripheral panel portion 21E in the first direction (downward direction). Simultaneously, the guide tool U53 prevents the sidewall portion 23E from buckling due to compressive stress by positioning the sidewall portion 23E between its outer guide surface U53a and the contact surface L51b of the lower outer tool L51. Therefore, the supporting force of the support tool (support member) L53 can apply a greater pushing force to the annular curved portion 24E through the sidewall portion 23E than the upper outer tool U51.

[0162] Thus, the support tool L53 applies force to the formed annular protrusion 13E ( Figure 20The supporting force of the protrusion (m6) in the state is opposite to the first direction (downward direction) and is pushed by the upper outer tool U51. As a result, the annular bend 24E is deformed, and the side wall portion 23E is subjected to compressive stress in the second direction (upward direction), and at least a portion of the plate constituting the side wall portion 23E is moved inward to the outer peripheral panel portion (outer peripheral plate portion) 21E on the contact surface L53a of the supporting tool L53. Thus, an annular protrusion 13E with selectively increased plate thickness according to its moving portion is formed. Figure 20 (state m6).

[0163] After forming the molded material 1E with the annular protrusion 13E, the molded material 1E is removed from the upper tool U5 and the lower tool L5 to obtain... Figure 20 The formed material 1E is in state m7. On the formed material 1E, the annular protrusion 13E increases the sheet thickness over a wide range, including the necessary range for improving compressive strength on the curved protrusion 132E between the inner peripheral wall portion 131E and the outer peripheral wall portion 133E. Figure 20 In the example of state m7, the outer peripheral panel (outer peripheral plate) 21E and the center panel (central plate) 22E are shown to be at approximately the same height, but this is not a limited example. The height positions of the outer peripheral panel 21E and the center panel 22E can be different as needed; for example, the height position of the outer peripheral panel 21E can be lower than the height position of the center panel 22E.

[0164] Thus, in the forming method of the sheet metal 11E of the second generalized approach, the same device (upper and lower molds) with an upper tool U5 and a lower tool L5 is used to continuously (in one stroke) push (press) the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 21E relative to each other. That is to say, the forming method of this second generalized approach is not performed in multiple stages and with different shaped molds each time, but in this way, the annular protrusion 13E with increased sheet thickness within the necessary range to improve compressive strength can be formed with a simple manufacturing process.

[0165] Instead of the example described herein, the same apparatus (upper and lower dies) can be used throughout the forming process of the forming material 1E, from the blank stamping process S31 to the annular protrusion forming (plate thickness increase forming) process S34. Alternatively, a different apparatus (upper and lower dies) can be used for the forming process of the forming material 1E from the blank stamping process S31 to the annular bending process S33, different from the apparatus (the apparatus with the upper tool U5 and the lower tool L5) used in the annular protrusion forming (plate thickness increase forming) process S34. In this case, a preformed part 11Ea is prepared in advance using this different apparatus, and this preformed part 11Ea is sequentially placed between the upper tool U5 and the lower tool L5.

[0166] Furthermore, in the example described in this second generalized approach, the upper outer tool U51 approaches the support tool (support member) L53, and the upper outer tool U51 applies a pushing force to the plate 11E on the contact surface (support surface) L53a in the first direction (downward direction), but is not limited to this. The support tool (support member) L53 is capable of relative movement in the second direction (upward direction). Therefore, instead of the example described here, the support tool (support member) L53 can also apply a pushing force to the plate 11E on the contact surface (support surface) L53a in the second direction (upward direction) by approaching the upper outer tool U51.

[0167] At this time, the outer peripheral panel portion 21E is sandwiched and fixed between the upper outer tool U51 and the lower outer tool L51. In this state, the support tool (support member) L53 pushes the guide tool U53 up. As a result, an annular curved portion 24E is formed on the inner peripheral side of the side wall portion 23E, which has a curved shape along the shape of the contact surface L53a of the support tool L53, and then an annular protrusion 13E is formed.

[0168] Next, the third to fifth embodiments of the present invention will be described. Descriptions of structures in the third to fifth embodiments that are identical to or mutually identical to the second generalized approach described above will be omitted. [Third Implementation Method]

[0169] The third embodiment of the sheet metal forming method is to form it as a forming material. Figure 21 The example can lid 3E has the following features: a central panel portion (central plate portion) 31E; a panel wall portion (inner peripheral wall portion) 321E; a retaining wall radius portion (bent protrusion) 322E; a retaining wall portion composed of a first retaining wall portion (first outer peripheral wall portion) 323E and a second retaining wall portion (second outer peripheral wall portion) 33E; and a curled portion 34E. Here, the annular protrusion 32E is composed of the panel wall portion 321E, the retaining wall radius portion 322E, and the first retaining wall portion 323E.

[0170] The central panel (central plate) 31E is located approximately in the center of the lid 3E and consists of a generally circular, generally flat surface. When the lid 3E is a retaining pull ring, the central panel 31E is provided with a pull ring for opening and scoring, etc.

[0171] A curved end (curved portion) 311E is formed at the radially outer end (outer edge) of the central panel portion 31E, and a panel wall portion (inner peripheral wall portion) 321E is formed extending downward in a generally straight line from the outer end (terminal end) of the curved end 311E. The retaining wall radius portion (curved protrusion) 322E is a curved portion, which is formed such that its inner end (inner peripheral side end) is connected to the lower end of the panel wall portion 321E, and its outer end (outer peripheral side end) is connected to the lower end of the first retaining wall portion (first outer peripheral wall portion) 323E.

[0172] The first retaining wall portion (first outer peripheral wall portion) 323E extends upward in a generally straight line from the outer end (upper outer peripheral side) of the retaining wall radius portion (bent protrusion) 322E. The second retaining wall portion (second outer peripheral wall portion) 33E is shaped to extend upward and outward in a generally straight line from the upper end (upper outer peripheral side) of the first retaining wall portion 323E, and its upper end is connected to the curved portion of the curled portion 34E.

[0173] The forming method of the can lid 3E includes, as a part of the overall process, the forming method of the sheet metal 11E described in the second generalized method above. That is, the forming method of the can lid 3E is as follows: Figure 22 As shown, it includes: blank stamping process S41; outer peripheral drawing process S42; central-outer peripheral plate forming process S43; annular bending process S44; annular protrusion forming (plate thickness increase forming) process S45; and (can lid) shape forming process S46. In these forming processes (S41 to S46), as... Figure 23 to Figure 25 The states m11 to m18 show the shape changes of sheet 41E, forming... Figure 25 The state of the can lid 3E of m19.

[0174] In the blank stamping process S41, for example, a stamping upper and lower tool (not shown) is used to stamp the sheet metal 41E into a generally disc shape, and the sheet metal 41E is formed into a generally disc shape. Figure 23 (State m11).

[0175] Sheet 41E is composed of a material primarily composed of metal. There are no particular restrictions on this metal material; it can be a single metal material such as aluminum, aluminum alloy, or steel, or a cladding material of these metals, or a composite metal material in which surface treatment, coating (including paints such as lubricants), lamination, etc., have been applied to one or both sides of these metals.

[0176] In the peripheral drawing process S42, for example, a peripheral drawing tool (not shown) is used to draw the peripheral portion of the generally disc-shaped sheet 41E, and is fixed. Figure 23 The inner circumferential plate-like portion of the outer periphery of the roughly disc-shaped sheet material 41E shown in m11 is simultaneously drawn. Thus, as... Figure 23As shown in state m12, an outer peripheral side 43E is formed on the outer peripheral side of the plate-shaped portion 42E of the plate 41E, which hangs down through the curved corner (extending in a direction approximately perpendicular to the plate-shaped portion 42E (downward direction)).

[0177] In the central-outer perimeter plate forming process S43, for example, for Figure 23 In state m12, a central drawing tool (not shown) is used to draw the plate portion 42E approximately from its center. A blank holder force is applied to the outer periphery portion (outer plate portion) 420E of the plate portion 42E, and a drawing process is performed on its inner periphery. Thus, as... Figure 23 As shown in state m13, while forming the center panel portion (central panel portion) 45E, an outer peripheral panel portion (outer peripheral panel portion) 421E, equivalent to the "specific panel portion" described in the preceding main method, is formed by forming the side wall portion 46E erected on the outer periphery of the center panel portion 45E. The shape of the center panel portion (central panel portion) 45E can be, for example, as shown in... Figure 23 The example shown is a generally flat surface, but it is not limited to such a generally flat surface; other shapes are also possible. The shape of the central panel portion 45E can also be a curved (dome) shape (not shown), which, for example, is formed in the rear annular protrusion 32Ea ( Figure 24 The state m16) is a gentle protrusion in the first direction (downward direction) or the opposite second direction (upward direction).

[0178] In the annular bending part forming process S44 and the annular protrusion forming (plate thickness increase forming) process S45, the plate 41E with the center panel part (central plate part) 45E and the outer peripheral panel part (outer peripheral plate part) 421E is formed. Figure 23 (state m13), using, for example, Figure 26 The forming device M4, consisting of the upper tool U6 and the lower tool L6 shown, performs forming processing. As such... Figure 26 and Figure 24 As shown in state m14, the upper tool U6 includes: an annular upper outer tool (upper tool of a specific plate portion) U61; an upper central tool U62; and an annular guide tool U63 located between them. The lower tool L6 includes: an annular lower outer tool L61; a lower central tool L62; and an annular support tool (support member) L63 located between them.

[0179] In addition, such as Figure 26As shown, in the molding device M4, the upper tool U6 is equipped with buffer pins Ua11 and Ua12 connected to the cylinder, and the lower tool L6 is equipped with buffer pins La11 and La12 connected to the cylinder. In the upper tool U6, the upper central tool U62 can move vertically via the buffer pins Ua11 and Ua12 connected to the cylinder, and the guide tool U63 can move vertically via the buffer pin Ua12 connected to the cylinder.

[0180] Additionally, in the lower tool L6, the support tool (support component) L63 can move vertically via the buffer pin La11 connected to the cylinder, and the lower outer tool L61 can move vertically via the buffer pin La12 connected to the cylinder. Alternatively, the forming device M4 can be equipped with an elastic component such as a spring component or a hydraulic cylinder (e.g., a hydraulic cylinder) to replace the buffer pins Ua11, Ua12, La11, and La12 that are connected to the cylinder.

[0181] In the ring-shaped bending part forming process S44, for example, Figure 24 As shown in state m14, the sheet metal 41E, which has a central panel portion (central plate portion) 45E and an outer peripheral panel portion (outer peripheral plate portion) 421E, is clamped and formed using the upper tool U6 and the lower tool L6. At this time, the central panel portion 45E of the sheet metal 41E is clamped and fixed by the contact surfaces U62a of the upper central tool U62 and L62a of the lower central tool L62. The fixing of the central panel portion 45E continues until the ring protrusion forming (plate thickness increase forming) process S45 ends.

[0182] In this state, during the ring-shaped bending part forming process S44, as follows: Figure 24 As shown in states m14 and m15, the upper outer tool U61 applies a pushing force in the first direction (downward direction). At this time, the outer peripheral panel portion (outer peripheral plate portion) 421E is clamped between the contact surface U61a of the upper outer tool U61 and the contact surface L61a of the lower outer tool L61, while the upper outer tool U61 pushes the lower outer tool L61 down.

[0183] U63 guide tool, etc. Figure 24 As shown in states m14 to m16, the sidewall portion can be either not lowered or lowered. In either case, the guide tool U63 and the lower outer tool L61 are located around the sidewall portion 46E. Thus, when compressive stress is applied to the sidewall portion 46E in the subsequent annular protrusion forming (plate thickness increase forming) process S45, it is possible to prevent the sidewall portion 46E from buckling due to this compressive stress.

[0184] In the annular bend forming process S44, the upper outer tool U61 pushes down the lower outer tool L61 so that the height position of its contact surface U61a is close to the height position of the contact surface (support surface) L63a of the support tool (support member) L63. That is, the support tool L63 can move relative to it in the second direction (upward direction). The support tool L63 applies a supporting force to the sheet 41E on its contact surface (support surface) L63a in the direction of the second direction (upward direction). Therefore, by pushing down the lower outer tool L61 with the upper outer tool U61, an annular bend 47E is formed on the inner circumferential side of the sidewall 46E, which is a bend shape along the shape of its contact surface L63a supported by the support tool L63 to which the supporting force is applied. The sheet 41E with such an annular bend 47E is used as a preform 41Ea. Figure 24 (state m15).

[0185] In the ring-shaped protrusion forming (plate thickness increase forming) process S45, for example, as Figure 24 As shown in states m15 and m16, the annular curved portion 47E of the preformed part 41Ea is supported by the contact surface (support surface) L63a of the support tool (support component) L63 (by a support force in the second direction (upward direction)), while a pushing force is applied to the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 421E in the first direction (downward direction).

[0186] At this time, the upper outer tool U61 continuously applies a pushing force in the first direction (downward direction) by pushing the lower outer tool L61 down with its contact surface U61a. That is, the upper outer tool U61 continuously applies a pushing force to the outer peripheral panel portion (outer peripheral plate portion) 421E sandwiched between the contact surface U61a and the contact surface L61a of the lower outer tool L61, advancing the outer peripheral panel portion 421E in the first direction (downward direction). At the same time, the guide tool U63 prevents the side wall portion 46E from buckling due to the compressive stress applied to the side wall portion 46E by positioning the side wall portion 46E between its outer guide surface U63a and the contact surface L61b of the lower outer tool L61. As a result, the supporting force of the support tool (support member) L63 can apply a greater pushing force to the annular curved portion 47E through the side wall portion 46E than the upper outer tool U61.

[0187] Thus, a supporting force in the second direction (upward direction) is applied by the supporting tool L63, and the upper outer tool U61 pushes the material forward. As a result, the annular bend 47E is deformed, and a compressive stress in the second direction (upward direction) is generated in the sidewall portion 46E. At least a portion of the plate constituting the sidewall portion 46E moves inward toward the outer peripheral panel portion (outer peripheral plate portion) 421E on the contact surface L63a of the supporting tool L63.

[0188] Through this annular protrusion forming (plate thickness increase forming) process S45, an intermediate molded body 30E (before shape forming (re-forming)) of a can lid with an annular protrusion 32Ea whose plate thickness is selectively increased according to its moving portion is formed. Figure 24 (State m16). On the intermediate molded body 30E, the annular protrusion 32Ea increases the plate thickness over a wide range, including the necessary range for improving compressive strength on the card wall radius portion (bent protrusion) 322Ea.

[0189] Thus, in the forming method of the sheet 41E in the third embodiment, the same device (upper and lower molds) having an upper tool U6 and a lower tool L6 is used to continuously (in one stroke) advance (push) the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 421E relative to each other. That is to say, the forming method of this third embodiment does not perform the advance in multiple stages and each time using a mold of a different shape, but in this way, the annular protrusion 32Ea with a large increase in sheet thickness can be formed with a simple manufacturing process.

[0190] After forming the intermediate molded body 30E of the can lid (before the shape is formed) with the annular protrusion 32Ea, the intermediate molded body 30E of the can lid is removed from the upper tool U6 and the lower tool L6.

[0191] The can lid shaping process S46 is a process of reshaping the shape of the intermediate can lid forming body 30E into the can lid shape. This can lid shaping process S46 includes a process for forming a retaining wall portion, which is composed of… Figure 25 It consists of a first retaining wall portion (first outer peripheral wall portion) 323E and a second retaining wall portion (second outer peripheral wall portion) 33E as shown in state m19.

[0192] In the can lid shape forming process S46, a curled portion 34E may be formed on the outer periphery of the annular protrusion 32Ea (or the formed annular protrusion 32E) in a sequence different from or simultaneously with the above-mentioned wall forming process. Figure 25 The well-known process of state m18 (not illustrated).

[0193] The center panel portion 45E of the intermediate molded body 30E may not be as shown. Figure 24 The state m16 is not a generally flat surface, but other shapes, such as a gently protruding curved (dome) shape in the second direction (upward direction) (not shown). In this case, the can lid shape forming process S46 may further include at least one or two of the following processes, either in a different order or simultaneously with the above-mentioned wall forming process: forming the center panel portion 45E into the desired shape (the process of forming, for example, a generally flat surface); the well-known process of forming the above-mentioned curled portion 34E.

[0194] In the can lid shaping process S46, for example... Figure 25 As shown in state m17, the can lid forming apparatus M5, which has an upper tool U7 and a lower tool L7, reshapes the can lid intermediate forming body 30E. The upper tool U7 has: an annular upper outer tool U71; an upper central tool U72; and an annular processing tool U73 located between them. The lower tool L7 has: an annular lower outer tool L71; a lower central tool L72; and an annular protrusion support tool L73 located between them.

[0195] In the can lid shaping process S46, it can be as follows: Figure 25 As shown in state m17, an intermediate forming body 30E for the can lid (before shaping) is set on the lower tool L7. Then, the upper outer tool U71, the upper central tool U72, and the processing tool U73 are lowered simultaneously, for example, to perform the can lid shaping process S46. Alternatively, the timing of the descent of the upper outer tool U71, the upper central tool U72, and the processing tool U73 can be appropriately changed according to the shape of the can lid.

[0196] At this point, the annular protrusion 32Ea is shaped into an annular protrusion 32E by the downward movement of the upper central tool U72. Figure 25 State m18), which is supported by the contact surface (support surface) L73a of the annular protrusion support tool L73, the annular protrusion 32Ea between the lower central tool L72 and the lower outer tool L71 is shaped along the contact end U72b of the upper central tool U72 and the contact surface (support surface) L73a of the annular protrusion support tool L73. That is to say, at this time, the first retaining wall part (first outer peripheral wall part) 323E on the retaining wall part is formed. Figure 25 (State m19).

[0197] At this time, the upper outer tool U71 descends, and its contact surface U71a contacts the outer peripheral panel portion (outer peripheral plate portion) 421E on the contact surface (support surface) L71b of the lower outer tool L71, fixing the outer peripheral panel portion 421E. In this state, the machining tool U73 descends, and the outer peripheral panel portion 421E is sandwiched between its contact surface U73a and the contact surface L71a, thereby forming the second clamping wall portion (second outer peripheral wall portion) 33E (please refer to...). Figure 25 State m19), which is the shape along the lower outer tool L71 and the machining tool U73. In this way, a retaining part is formed, consisting of a first retaining wall part (first outer peripheral wall part) 323E and a second retaining wall part (second outer peripheral wall part) 33E on its outer periphery (please refer to Figure 25 (State m19).

[0198] Additionally, at this time, a curled portion 34E can be formed on the outer periphery of the cover. At this time, the lower tool L7 can also have a curling tool (not shown) on the outer periphery of the lower outer tool L71. As described above, with the outer peripheral panel portion 421E fixed, the machining tool U73 descends, causing the outer peripheral panel portion 421E sandwiched between its contact surface U73a and contact surface L71a to flow towards the outer periphery. In this state, the curled portion 34E is formed by descending the curling tool (not shown). Figure 25 The state m18), which is the shape of the contact surface U71a of the upper outer tool U71 and the contact surface of the curling tool (not shown).

[0199] Additionally, when the shape of the center panel portion (central plate portion) 45E is other than that of other shapes (e.g., a gently protruding curved (dome) shape in the second direction (upward direction) (not shown)), it can also be shaped into a desired shape, such as a generally flat surface. At this time, the upper central tool U72 descends through its contact surface U72a, pushing down the lower central tool L72, and shaping the center panel portion (central plate portion) 45E, which is of another shape (e.g., a gently protruding curved (dome) shape in the second direction) sandwiched between the contact surface U72a and the contact surface L72a of the lower central tool L72, into a generally flat center panel portion (central plate portion) 31E. Figure 25 (state m18).

[0200] at this time, Figure 25 In the can lid shape forming process S46, the process of forming the wall part and the process of forming the center panel part (central plate part) 45E into a generally flat surface are performed simultaneously, but these processes can also be performed in different order as different stages.

[0201] Thus, the reshaped can lid 3E is removed from the can lid forming device M5, resulting in... Figure 22 The can lid 3E shown in state m19. The can lid 3E after being remolded in state m19 has the following shape: the annular protrusion 32E, which is composed of the panel wall portion (inner peripheral wall portion) 321E, the retaining wall radius portion (bent protrusion) 322E, and the first retaining wall portion (first outer peripheral wall portion) 323E, protrudes downward in a direction that is approximately perpendicular to the extension direction of the central panel portion 31E.

[0202] Instead of the example described here, the same apparatus (upper and lower molds) can be used throughout the forming process of the can lid 3E, from the blank stamping process S41 to the annular protrusion forming (plate thickness increase forming) process S45. Alternatively, a different apparatus (upper and lower molds) can be used from the blank stamping process S41 to the annular bending part forming process S44, different from the apparatus (the apparatus with the aforementioned upper tool U6 and lower tool L6) used in the annular protrusion forming (plate thickness increase forming) process S45. In this case, a pre-formed part 41Ea is prepared in advance using this different apparatus, and this pre-formed part 41Ea is placed between the upper tool U6 and the lower tool L6. [Examples of the Third Embodiment (Examples 1 to 5)]

[0203] Examples of the third embodiment (Examples 1 to 5) will be described. In Examples 1 to 5, through the blank stamping process S41 to the annular protrusion forming (plate thickness increase forming) process S45 described in the third embodiment, an intermediate molded body 40Eb before can lid shape forming (re-forming) is formed from the sheet metal. Figure 25 (a)). As a sheet material, the sheet material used is an aluminum alloy (A5182) (metal part) with an original thickness of 0.218 mm, coated on both sides with a coating including a lubricant. For example... Figure 27 As shown in (a), the intermediate molded body 40Eb has: a curved (dome) shaped central panel portion (central plate portion) 45Eb; an outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 421Eb corresponding to the aforementioned outer peripheral panel portion 421E; and an annular protrusion portion 32Eb.

[0204] In embodiments 1 to 5, in the above-mentioned annular protrusion forming (plate thickness increase forming) process S45, the annular curved portion (not shown here) is supported by the contact surface (support surface) L63a of the support tool (support member) L63 (by a support force in the upward direction (the above-mentioned second direction)), while a pushing force is applied to the outer peripheral panel portion (outer peripheral plate portion) 421Eb in the downward direction (the above-mentioned first direction). At this time, a support force in the upward direction (second direction) from the support tool L63 is applied to the plate portion (annular curved portion) on the contact surface (support surface) L63a of the support tool L63. At this time, the magnitude of this support force, i.e., the support force (counterhead hole holding force) [kgf], is different in embodiments 1 to 5. For each of these different support forces, measurement points a to v on the plate of the intermediate molded body 40Eb are measured. Figure 27 The thickness of the metal portion of (a) and (b) [mm] Figure 27 ).

[0205] During the above-mentioned ring-shaped protrusion forming (plate thickness increase forming) process S45, if Figure 28As shown, the supporting force (countersunk hole holding force) [kgf] applied by the supporting tool L63 is 200 kgf in Example 1, 400 kgf in Example 2, 600 kgf in Example 3, 800 kgf in Example 4, and 1000 kgf in Example 5. Figure 28 Curves G1 to G5 in the figure represent the measured values ​​of the metal portion thickness [mm] at measurement points a to v on the sheet after process S45 in Examples 1 (support force 200 kgf), 2 (support force 400 kgf), 3 (support force 600 kgf), 4 (support force 800 kgf), and 5 (support force 1000 kgf), respectively.

[0206] like Figure 28 The measurement results show that, in any of Examples 1 to 5, where an upward (second direction) support force (countersunk hole holding force) [kgf] was applied from the support tool L63, the thickness of the metal portion on the sheet metal could be increased by 0.218 mm over a wide range of measurement points a to v. Furthermore, from this… Figure 28 The results of Examples 1 to 5 show that as the support force [kgf] is increased, the thickness [mm] of the metal portion on the sheet can be increased.

[0207] Here, through various prior experiments and simulations, it was confirmed that the wall radius (bent protrusion) 322Eb, including the annular protrusion 32Eb, is... Figure 28 (b) The range including measurement points f to i and the range including measurement points l to n are the ranges where pressure resistance needs to be improved, especially after the lid of the can (metal can) is fitted with the shape formed (re-formed) from the intermediate molding body 40Eb. Figure 27 (b) The range between the measuring points f and i on the radius portion (bending protrusion) 322Eb shown in the diagram is the "main pressure resistance range X1", and the range between the measuring points l and n is the "main pressure resistance range X2". For example... Figure 27 The measurement results in the main pressure resistance ranges X1 and X2 show that by applying a large value of the support force (counterhead hole holding force) [kgf] in the second direction (upward direction) by the support tool L63, a sufficiently large plate thickness [mm] value can be obtained in both the main pressure resistance ranges X1 and X2 (e.g., Examples 4 and 5). [Examples of the Third Embodiment (Examples 6 to 8, Comparative Example 1)]

[0208] Next, embodiments of the third embodiment (Examples 6 to 8, Comparative Example 1) will be described. In Examples 6 to 8 and Comparative Example 1, the blank stamping process S41 to the can lid shape forming process S46 described above in the third embodiment are used to form a can lid from a sheet metal.Figure 28 The can lid shown is 3Ec. The sheet metal used is an aluminum alloy (A5182) with a base thickness of 0.218mm. Figure 30 Both sides of the (metal part) are coated with a paint including lubricant.

[0209] Furthermore, during the aforementioned annular protrusion forming (plate thickness increase forming) process S45, the supporting force (countersunk hole holding force) [kgf] applied by the supporting tool L63 was 700 kgf in Example 6, 800 kgf in Example 7, 900 kgf in Example 8, and 0 kgf in Comparative Example 1. Figure 29 ).like Figure 29 As shown, the can lids 3Ec formed in Examples 6 to 8 and Comparative Example 1 all have a lid diameter of 206 (2 inches 6 / 16), a lid shape of CDL (Container Development Ltd.), a unit depth (UD) [mm] of 6.66 mm, and a panel height (PH) [mm] of 2.54 mm.

[0210] like Figure 29 As shown by the double arrows, the unit depth (UD) [mm] is the distance in the height direction from the lower end of the outer surface of the can lid 3Ec (i.e., the lower end of the outer surface of the wall radius (bent protrusion) 322Ec of the annular protrusion 32Ec) to the upper end of the outer surface of the can lid 3Ec, and the panel height (PH) [mm] is the distance in the height direction from the lower end of the outer surface of the can lid 3Ec to the outer surface of the center panel (central panel) 31Ec.

[0211] In Examples 6 to 8 and Comparative Example 1, the molded can lid 3Ec was rolled and sealed onto the can container (metal can), and a pressure resistance test was conducted by applying water pressure internally. The results are as follows: Figure 30 As shown, the pressure resistance values ​​(pressure strength) displayed are 0.654 MPa in Example 6, 0.656 MPa in Example 7, and 0.696 MPa in Example 8, all of which meet the required performance. However, the pressure resistance value (pressure strength) of Comparative Example 1 is 0.630 MPa, which does not meet the required performance. These results demonstrate that applying a supporting force (countersunk hole holding force) [kgf] using the supporting tool L63 can improve the pressure resistance of the can lid; further increasing this supporting force results in even greater pressure resistance. [Fourth Implementation Method]

[0212] The fourth embodiment of the sheet metal forming method involves forming the sheet metal by... Figure 29 The process shown involves increasing the sheet thickness in the first stage of forming, followed by... Figure 31 The process shown involves a second stage of sheet thickness increase molding, followed by... Figure 32The process shown involves the third stage of plate thickness increase molding. Figure 33 The height Ht indicated by the dashed line always represents the same height. (The first stage involves increasing the plate thickness during molding)

[0213] Figure 31 to Figure 33 In the first stage of the sheet thickness increase forming process shown, firstly, an outer peripheral drawing tool (not shown) is used to draw the outer peripheral portion of the sheet 51E, which is stamped from a blank into a generally disc-shaped form. A blank holder force is applied to the sheet-like portion 52E on the inner peripheral side of the outer peripheral portion of this generally disc-shaped sheet 51E, and the outer peripheral portion is then drawn. Thus, as... Figure 31 As shown in state m21, an outer peripheral side portion 53E is formed on the outer peripheral side of the plate-shaped portion 52E, which hangs down through the curved corner (extending in a direction approximately perpendicular to the plate-shaped portion 52E (downward direction)).

[0214] Next, for sheet material 51E in state m21, a central drawing tool (not shown) is used to draw approximately the central portion of its sheet-like portion 52E. A blank holder force is applied to the outer periphery of the sheet-like portion 52E, and the inner periphery is drawn. Thus, as... Figure 31 As shown in state m22, the outer peripheral panel portion (outer peripheral plate portion) 521E is formed on the molded sheet 51E, and the center panel portion (central plate portion, specific plate portion) 54E is formed through the side wall portion 55E that rises upward on the inner peripheral side of the outer peripheral panel portion 521E. Here, the central protrusion 56E is formed by the center panel portion (central plate portion) 54E and the side wall portion 55e.

[0215] Next, as Figure 31 As shown in state m23, forming is performed using a forming apparatus having, for example, an upper tool U8 and a lower tool L8. The upper tool U8 includes: an annular upper outer tool U81; an upper central tool U82; and an annular guide tool U83 located between them. Figure 31 In the example shown, the guide tool U83 is integrally disposed on the outer periphery of the upper central tool U82. However, the guide tool U83 is not limited to this structure and may also be disposed separately from the upper central tool U82 on the outer periphery of the upper central tool U82. The lower tool L8 is provided with: an annular lower outer tool L81; a lower central tool L82; and an annular support tool (support member) L83 located between them. As shown in state m23, a sheet metal 51E with a central panel portion 54E and a side wall portion 55E (i.e., a central protrusion 56E) is disposed between the upper tool U8 and the lower tool L8.

[0216] Then, the outer peripheral panel portion 521E of the plate 51E is clamped and fixed using the upper outer tool U81 and the lower outer tool L81. Figure 31 to Figure 33 (State m24). This fixation continues until state m26. Thus, with the outer peripheral panel portion 521E fixed, the center panel portion 54E is clamped between the contact surface U82a of the upper central tool U82 and the contact surface L82a of the lower central tool L82, while the upper central tool U82 pushes the lower central tool L82 down (states m24, state m25). In addition, the side wall portion 55E is located between the guide tool U83 and the lower central tool L82.

[0217] The upper central tool U82 pushes the lower central tool L82 down so that the height of its contact surface U82a is close to the height of the contact surface (support surface) L83a of the support tool (support component) L83. That is, the support tool L83, in contact with the subsequently formed annular protrusion 62Ea... Figure 31 The protrusion (m26) can move relative to the second direction (upward direction) opposite to the first direction (downward direction). The support tool L83 applies a supporting force in the second direction (upward direction) to the plate 51E on its contact surface (support surface) L83a. Therefore, by pushing the lower central tool L82 down by the upper central tool U82, an annular curved portion 57E is formed on the outer periphery of the side wall portion 55E, which is a curved shape along the shape of its contact surface L83a supported by the support tool L83 to which the supporting force is applied. Figure 31 (state m25).

[0218] Then, the annular curved portion 57E is further supported by the contact surface (support surface) L83a of the support tool (support component) L83 (by a support force in the second direction (upward direction), while a pushing force is applied to the center panel portion (specific plate portion) 54E in the first direction (downward direction) opposite to the second direction.

[0219] At this time, the upper central tool (the upper tool of the specific plate portion) U82 continuously applies a pushing force in the first direction (downward direction) by pushing the lower central tool L82 down with its contact surface U82a. That is, the upper central tool U82 continuously applies a pushing force to the central panel portion (central plate portion, specific plate portion) 54E sandwiched between the contact surface U82a and the contact surface L82a of the lower central tool L82, advancing the central panel portion 54E in the first direction (downward direction). At the same time, the guide tool U83 prevents the side wall portion 55E from buckling due to the compressive stress applied to the side wall portion 55E by positioning the side wall portion 55E between it and the lower central tool L82. As a result, the supporting force of the support tool (support member) L83 can apply a greater pushing force to the annular curved portion 57E than the upper central tool U82 through the side wall portion 55E.

[0220] By advancing through the upper central tool U82, the annular bend 57E is deformed, and a second-direction (upward) compressive stress is generated in the side wall portion 55E. At least a portion of the plate constituting the side wall portion 55E is moved outward from the central panel portion (specific plate portion) 54E on the contact surface L83a of the support tool L83.

[0221] Thus, a can lid intermediate molded body 60E (state m26) is formed having an annular protrusion 62Ea whose thickness is selectively increased according to its movement. On the intermediate molded body 60E, the annular protrusion 62Ea is connected to the outer peripheral panel portion (outer peripheral plate portion) 521E on its outer periphery via a side wall portion 61E. This annular protrusion 62Ea increases the plate thickness over a wide range, including the necessary range for improving pressure resistance in the retaining wall radius portion (bent protrusion).

[0222] Next, as shown in state m27, the intermediate molded body 60E of the can lid is removed from the upper tool U8 and the lower tool L8. Thus, the intermediate molded body 60E after the first stage of plate thickness increase molding is obtained (state m28). (The second stage involves increasing the plate thickness during molding)

[0223] Depend on Figure 31 In the second stage of sheet thickness increase molding shown in the process, the intermediate molded body 60E (state m29) that underwent the first stage of sheet thickness increase molding is subjected to the process. Figure 32 In state m28), similar to the third embodiment described above, a pushing force in the first direction (downward direction) is applied by the upper outer tool (the upper tool of the specific plate portion) U81. That is, the intermediate molded body 60E is positioned between the upper tool U8 and the lower tool L8 (state m30), and then the center panel portion 54E is clamped and fixed by the upper central tool U82 and the lower central tool L82 (state m31).

[0224] In this state, a pushing force is applied to the outer peripheral panel portion (specific plate portion) 521E clamped between the upper outer tool U81 and the lower outer tool L81, advancing the outer peripheral panel portion 521E in a first direction (downward direction). This deforms the annular protrusion 62Ea and generates compressive stress in the sidewall portion 61E in a second direction (upward direction), causing at least a portion of the plate constituting the sidewall portion 61E to move inward toward the outer peripheral panel portion 521E on the contact surface L83a of the support tool L83. Thus, an intermediate molded body 70E (state m32) is formed on the inner peripheral side of the outer peripheral panel portion 521E, having an annular curved portion 62Eb whose thickness is selectively further increased according to its movement. This intermediate molded body 70E has a sidewall portion 63E that rises upward on the inner peripheral side of the annular curved portion 62Eb, and a central protrusion 64E is formed from this sidewall portion 63E and the central panel portion (central plate portion) 54E.

[0225] Then, as shown in state m33, the intermediate molded body 70E is removed from the upper tool U8 and the lower tool L8. Thus, the intermediate molded body 70E after the second stage of plate thickness increase molding is obtained (state m34). (Third stage: increasing plate thickness for forming)

[0226] Depend on Figure 31 In the third stage of sheet thickness increase molding shown in the process, the intermediate molded body 70E (state m35) that underwent the second stage of sheet thickness increase molding is subjected to the process. Figure 33 In state m34), the same process as the first stage of sheet thickness increase forming described above is performed. That is, the sheet thickness increase forming process is performed. Figure 32 The intermediate molded body 70E shown in state m35, as shown in state m36, is positioned between the upper tool U8 and the lower tool L8, and as shown in state m37, the outer peripheral panel portion 521E is clamped and fixed by the upper outer tool U81 and the lower outer tool L81.

[0227] In this state, the center panel portion 54E is clamped between the upper center tool U82 and the lower center tool L82, while the upper center tool (the upper tool of the specific plate portion) U82 continuously applies a pushing force in the first direction (downward direction) to push the lower center tool L82 down (state m37, state m38).

[0228] Specifically, the contact surface L83a of the support tool L83 supports the annular curved portion 62Eb of the intermediate molded body 70E (by a supporting force in the second direction (upward direction)), while simultaneously applying a pushing force to the center panel portion (specific plate portion) 54E in a first direction (downward direction) opposite to the second direction (upward direction). At this time, the supporting force of the support tool (support member) L83 can apply a greater pushing force to the annular curved portion 62Eb through the side wall portion 63E than that of the upper central tool U82.

[0229] By advancing through the upper central tool U82, the annular bend 62Eb is deformed, and a second-direction (upward) compressive stress is generated in the side wall 63E. At least a portion of the plate constituting the side wall 63E is moved outward from the central panel 54E on the contact surface L83a of the support tool L83.

[0230] Thus, a can lid intermediate molded body 80E (state m38) is formed having an annular protrusion 82Ea whose thickness is selectively further increased according to its moving portion. On the intermediate molded body 80E, the annular protrusion 82Ea is connected to the outer peripheral panel portion 521E on its outer peripheral side via a side wall portion 81E.

[0231] Next, as shown in state m39, the intermediate molded body 80E of the can lid is removed from the upper tool U8 and the lower tool L8. This yields the intermediate molded body 80E of the can lid after the third stage of thickness-increasing molding (state m40). In state m40, the intermediate molded body 80E has its thickness further increased over a wide range, including the necessary range for improving pressure resistance on the wall radius portion (bent protrusion) 822Ea of the annular protrusion 82Ea.

[0232] Thus, according to the sheet forming method of the fourth embodiment, by processing the sheet... Figure 33 The multiple stages of plate thickness increase molding shown in the first to third stages allow for a further increase in plate thickness over a wide range, including the necessary area on the annular protrusion 82Ea. Therefore, a can lid with further improved pressure resistance can be formed from the intermediate molded body 80E formed by the plate molding method of this fourth embodiment.

[0233] The above Figure 31 to Figure 33 In the first to third stages of sheet thickness increase forming shown, the same forming apparatus with an upper tool U8 and a lower tool L8 is always used. However, it is not limited to such an example. The forming apparatus with the upper tool U8 and the lower tool L8 may have a different structure than that used in the first and third stages of sheet thickness increase forming (especially in terms of the buffer pin (not shown), cylinder, etc. (not shown)). [Fifth Implementation]

[0234] The fifth embodiment of the sheet metal forming method is to form it as a forming material. Figure 31 to Figure 33 The example tank bottom 10E in state m48. The forming method of the tank bottom 10E includes, as a part of the overall process, the forming method of the sheet metal 11E in the second generalized manner described above.

[0235] The molding method for the bottom 10E of this tank includes: as shown above Figure 35 The same process, that is Figure 22 The billet stamping process S41 is shown; the outer peripheral drawing process S42; the central-outer peripheral plate forming process S43; the annular bending forming process S44; the annular protrusion forming (plate thickness increase forming) process S45; and the (can bottom) shape forming process S46. In these forming processes (S41 to S46), as follows... Figure 22 and Figure 34 The shape of the sheet 91E is changed from state m41 to state m47, and the bottom of the tank is shaped (re-shaped) to state m48, which is the bottom of the tank 10E.

[0236] In the blank stamping process S41 of the forming process of the can bottom 10E, for example, a stamping upper and lower tool (not shown) is used to stamp the sheet metal 91E to be processed into a generally disc shape, and the sheet metal 91E is formed into a generally disc shape. Figure 35 (State m41).

[0237] In the outer peripheral drawing process S42 of the forming process of the can bottom 10E, for example, an outer peripheral drawing tool (not shown) is used to draw the outer peripheral portion of the generally disc-shaped sheet 91E. Figure 34 A blank holder force is applied to the inner plate-shaped portion of the roughly disc-shaped sheet 91E shown in state m41, and the outer periphery is then drawn. Thus, as... Figure 34 As shown in state m42, an outer peripheral side 93E is formed on the outer periphery of the plate-shaped portion 92E of the sheet 91E, which rises upward through a curved corner (extending in a direction approximately perpendicular to the plate-shaped portion 92E (upward direction)). Well-known thinning moldings may be added to the outer peripheral side 93E as needed.

[0238] In the central-outer perimeter plate forming process S43 of the forming process of the can bottom 10E, for example, for Figure 34 In state m42, a central drawing tool (not shown) is used to draw the plate portion 92E approximately to its center. A blank holder force is applied to the outer panel portion (outer panel portion) 921E of the plate portion 92E, and in this state, the inner circumferential side is drawn. Thus, as... Figure 34As shown in state m43, a central panel portion (central plate portion) 94Ea, consisting of generally flat surfaces, is formed. Simultaneously, an outer peripheral panel portion (outer peripheral plate portion) 922E, corresponding to the "specific plate portion" described in the preceding main configuration, is formed through a side wall portion 95E that rises from the outer periphery of the central panel portion 94Ea. The central panel portion 94Ea is formed into the rear dome panel portion 94E.

[0239] In the forming process of the bottom of the can 10E, the annular bending part forming process S44 and the annular protrusion forming process (plate thickness increase forming) S45, for example, for the plate 91E which has a central panel part 94Ea and an outer peripheral panel part 922E formed ( Figure 34 In state m43), a forming device with an upper tool U9 and a lower tool L9 is used for forming. Figure 34 As shown in state m44, the upper tool U9 includes: an annular upper outer tool (upper tool of a specific plate portion) U91; an upper central tool U92; and an annular guide tool U93 located between them. The lower tool L9 includes: an annular lower outer tool L91; a lower central tool L92; and an annular support tool (support member) L93 located between them. Figure 34 As shown in state m44, the sheet 91E, which has a central panel portion 94Ea and an outer peripheral panel portion 922E, is positioned between the upper tool U9 and the lower tool L9.

[0240] The center panel portion 94Ea is then clamped and fixed using the contact surfaces U92a of the upper center tool U92 and L92a of the lower center tool L92. The center panel portion 94Ea is thus clamped and fixed, forming a dome-shaped dome panel portion 94E. Figure 34 The state m45), which is in relation to the annular protrusion 102Ea formed behind it ( Figure 35 The first direction (downward direction) of the protrusion is a gentle upward protrusion in the opposite direction (upward direction). The upper central tool U92 and the lower central tool L92 are fixed to the dome panel 94E until the annular protrusion is formed (plate thickness increase forming) process S45 ends.

[0241] In this state, during the annular bending part forming process S44 of the forming process of the bottom 10E, as follows: Figure 35 As shown in states m45 and m46, the upper outer tool U91 applies a pushing force in the first direction (downward direction). At this time, the outer peripheral panel portion (outer peripheral plate portion) 922E is clamped between the contact surface U91a of the upper outer tool U91 and the contact surface L91a of the lower outer tool L91, while the upper outer tool U91 pushes the lower outer tool L91 down.

[0242] U93 guide toolFigure 35 As shown in states m45 to m47, the sidewall portion 95E can be either lowered or not lowered. In either case, the guide tool U93 and the lower outer tool L91 are located around the sidewall portion 95E. Thus, when compressive stress is applied to the sidewall portion 95E in the subsequent annular protrusion forming (plate thickness increase forming) process S45, it is possible to prevent the sidewall portion 95E from buckling due to this compressive stress.

[0243] In the annular bending section forming process S44 of the forming process of the tank bottom 10E, the upper outer tool U91 pushes the lower outer tool L91 down so that the height position of its contact surface U91a is close to the height position of the contact surface (support surface) L93a of the support tool (support member) L93. That is, the support tool L93 can move relative to it in the second direction (upward direction). The support tool L93 applies a supporting force to the plate 91E on its contact surface (support surface) L93a in the direction of the second direction (upward direction).

[0244] Therefore, by pushing the lower outer tool L91 down by the upper outer tool U91, an annular curved portion 96E is formed on the inner circumferential side of the sidewall portion 95E. This curved portion is supported by the support tool L93, which applies the supporting force, and is curved along the shape of its contact surface L93a. The sheet 91E with such an annular curved portion 96E is used as a preform 91Ea. Figure 35 (state m46).

[0245] In the annular protrusion forming (plate thickness increase forming) process S45 of the forming process of the can bottom 10E, for example, as Figure 35 As shown in states m46 and m47, the annular curved portion 96E of the preformed part 91Ea is supported by the contact surface L93a of the support tool L93 (by a support force in the second direction (upward direction)), while a pushing force is applied to the outer peripheral panel portion 922E in the first direction (downward direction).

[0246] At this time, the upper outer tool U91 continuously applies a pushing force in the first direction (downward direction) to the lower outer tool L91 by pushing it down with its contact surface U91a. That is, the upper outer tool U91 continuously applies a pushing force to the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 922E sandwiched between the contact surface U91a and the contact surface L91a of the lower outer tool L91, advancing the outer peripheral panel portion 922E in the first direction (downward direction). Simultaneously, the guide tool U93 prevents the sidewall portion 95E from buckling due to compressive stress by positioning the sidewall portion 95E between its outer guide surface U93a and the contact surface L91b of the lower outer tool L91. Therefore, the supporting force of the support tool (support member) L93 can apply a greater pushing force to the annular curved portion 96E through the sidewall portion 95E than the upper outer tool U91.

[0247] Thus, a supporting force in the second direction (upward direction) is applied by the supporting tool L93, and the upper outer tool U91 pushes the material forward. As a result, the annular bending portion 96E is deformed, and a compressive stress in the second direction (upward direction) is generated in the side wall portion 95E. At least a portion of the plate constituting the side wall portion 95E moves inward toward the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 922E on the contact surface L93a of the supporting tool L93.

[0248] Through the annular protrusion forming (plate thickness increase forming) process S45 in the forming process of the can bottom 10E, an intermediate molded body 100E with an annular protrusion 102Ea whose plate thickness is selectively increased according to its moving portion is formed. Figure 35 (State m47). On the intermediate molded body 100E, the annular protrusion 102Ea has a significantly increased plate thickness, including the necessary range for improving pressure resistance on the bottom radius portion (bent protrusion) 112Ea. Thus, after forming the intermediate molded body 100E of the can bottom (before shape forming) with the annular protrusion 102Ea, the intermediate molded body 100E of the can bottom is removed from the upper tool U9 and the lower tool L9.

[0249] Thus, in the forming method of the sheet 91E in the fifth embodiment, the same device (upper and lower molds) with an upper tool U9 and a lower tool L9 is used to continuously (in one stroke) push (press) the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) 922E relative to each other. That is to say, the forming method of this fifth embodiment is not performed in multiple stages and with different shaped molds each time, but in this way, the annular protrusion 102Ea with increased sheet thickness within the necessary range can be formed with a simple manufacturing process.

[0250] The can bottom shaping process S46 is a process that reshapes the intermediate molded body 100E of the can bottom into the shape of the can bottom as needed (bottom reshaping). This process includes shaping the annular protrusion 102E of the can bottom. After the reshaping in the can bottom shaping process S46, the can bottom 10E is obtained from the reshaping device (not shown). Figure 35 (State m48).

[0251] The bottom-forming process S46 can be performed using methods that are well-known in the past, such as rotating rollers or compression molding.

[0252] In addition, in the fifth embodiment, especially when an inner coating process is required, it is best to perform the process before the bottom-forming process S46.

[0253] Should Figure 35 The bottom 10E of the m48 can has: a dome-shaped panel portion (central panel portion) 101E; a dome-shaped panel wall portion (inner peripheral wall portion) 151E; a bottom radius portion (curved protrusion) 152E; a lower part of the bell portion (first outer peripheral wall portion) 153E; and a bell portion (second outer peripheral wall portion) 103E. Here, the dome-shaped panel wall portion 151E, the bottom radius portion 152E, and the lower part of the bell portion 153E constitute the annular protrusion 102E of the bottom of the can. The annular protrusion 102E of the bottom of the can is remolded to have a slightly inwardly inclined shape, and the plate thickness is increased over a large range, including the necessary range of the bottom radius portion 152E.

[0254] Furthermore, depending on the requirements, the bottom shaping process S46 can further include a process of shaping the dome-shaped panel (central panel) 94E into a desired shape, such as a shape other than a sphere, such as a roughly ellipsoidal surface, a roughly conical surface, or a roughly flat surface. In this case, as a re-forming process... Figure 35 The process of shaping the bottom of the can 100E in state m47, the bottom shape forming process S46 may simultaneously or sequentially include: the process of shaping the annular protrusion 102E of the bottom of the can; and the process of shaping the dome panel (central panel) 94E into, for example, a generally flat surface. [Example of the fifth embodiment (Example 9)]

[0255] Next, an embodiment of the fifth implementation (Example 9) will be described. In Example 9, a drawn thinning can (DI can) with an internal volume of 350 mL (after bottom shaping (re-forming)) was manufactured by the method shown below. First, an aluminum alloy sheet (JIS H 4000 A3104-H19 material, 0.220 mm (original sheet thickness)) was prepared as the sheet material (substrate) to be processed. Next, a predetermined amount of well-known cutting oil was applied to both sides of the aluminum alloy sheet (sheet) as a lubricant during the drawing process.

[0256] Next, using a drawing forming machine (stamping upper and lower tools) (not shown), the aluminum alloy sheet coated with the lubricant is stamped into a disc shape with a diameter of 160mm (not shown) (equivalent to the blank stamping process S41 in the forming process of the can bottom 10E mentioned above). Then, using an outer peripheral drawing upper and lower tool (not shown), a blank holder force is applied to the inner plate-like portion of the outer peripheral portion of this disc-shaped sheet, and the outer peripheral portion is drawn. This results in a drawn cup with a diameter of 90mm (not shown).

[0257] The drawn cup (not shown) was transferred to a can manufacturing machine (can manufacturing machine) and re-drawn into a shape with a diameter of 66 mm. Then, using a coolant, it underwent the outer circumference drawing process S42, equivalent to the forming process of the can bottom 10E described above. Thus, a can with... Figure 35 The bottom of the cup is in the shape shown in state m42, and the cup body has a diameter of 66mm, a height of 130mm, and a minimum thickness of 0.105mm.

[0258] Next, the formed cup body is processed using a central pulling tool (not shown) to perform the central-outer peripheral plate forming process S43, which is equivalent to the forming process of the can bottom 10E described above. Thus, while forming the central panel portion (central plate portion) composed of flat surfaces, the first precursor of the DI can (not shown) is formed, which includes the can bottom (equivalent to the central-outer peripheral plate portion, specific plate portion) formed by forming the outer peripheral panel portion (outer peripheral plate portion, specific plate portion) through the sidewall portion erected on the outer peripheral side of this central panel portion. Figure 34 (state m43).

[0259] Next, this first precursor will be as follows: Figure 34 The state m44 is positioned between the upper tool U9 and the lower tool L9. Then, the center panel is clamped and fixed by the upper center tool U92 and the lower center tool L92, causing the center panel to deform as shown. Figure 34 The dome-shaped panel section is in state m45. In this state, as a pressing process in which the upper outer tool U91 applies pushing pressure in the first direction (downward direction), the forming process of the bottom of the can 10E, which is equivalent to the ring-shaped bending part forming process S44, and the subsequent forming process of the ring-shaped protrusion (plate thickness increase forming) process S45, are carried out.

[0260] First, in the annular bending forming process S44 of the forming process corresponding to the bottom of the can 10E mentioned above, the outer peripheral panel portion (outer peripheral plate portion) is clamped between the upper outer tool U91 and the lower outer tool L91, while the upper outer tool U91 pushes the lower outer tool L91 down. Thus, the second precursor of the DI can is formed, which includes having as...Figure 35 The tank bottom preform shown in state m46 has an annular curved section.

[0261] Next, in the annular protrusion forming (plate thickness increase forming) process S45 of the forming process corresponding to the can bottom 10E described above, the annular curved portion of the formed preform is supported by the support tool L93 (support force in the second direction (upward direction) as described above), while a pushing force is applied to the outer peripheral panel portion (specific plate portion) in the first direction (downward direction). Thus, a drawn thinning can (DI can) (before can bottom shape forming (reforming)) is formed, which includes a portion having a thickness increase of approximately 10E. Figure 35 The shape of state m47, i.e. Figure 35 The annular protrusion 512E shown is a can bottom intermediate molded body 510E. This annular protrusion 512E has: a dome panel wall portion 513E; a bottom radius portion 514E (before remolding); and a lower bell portion 515E (before remolding). Furthermore, a bell portion 516E (before remolding) is formed on the outer side of the lower bell portion 515E.

[0262] Using previous methods in this Figure 36 On the can bottom intermediate molded body 510E shown, a trimming process to align the edges to the required can height and a bottom re-forming process (equivalent to the can bottom shape forming process S46 in the molding process of the can bottom 10E mentioned above) are performed to obtain... Figure 36 The final molded part of the tank bottom (after remolding) shown is 520E.

[0263] The measurement was performed. Figure 37 The sheet thickness [mm] of the metal parts at various locations on the (re-formed) final molded body 520E. Figure 37 The measurement points w1 to w7 are shown in the diagram. The plate thickness [mm] was measured as follows: After the pre-formed (final molded body) thinned can (DI can) was embedded in epoxy resin, it was cut along the longitudinal axis (Z-axis) of the DI can, along with the epoxy resin. After cutting and carefully polishing to expose the center section, the plate thickness [mm] of the metal part at each measurement point from w1 to w7 was measured using a measuring microscope.

[0264] Other examples Figure 37 As shown in the table, in this embodiment 9, the dome panel portion 522E on the drawn thinning can (DI can) (for the final molded body) Figure 38 The height Hp of the part is 12.3 mm. Additionally, on the final molded body 520E, the diameter (d1) between the boundary portion of the dome panel 522E and the (re-molded) annular protrusion 523E at the bottom of the can is... Figure 37 The diameter (d2) of the grounding part of the annular protrusion 523E at the bottom of the tank is 47.0 mm. Figure 37The measurement is 48.0 mm. Additionally, the measurement points w1 to w7 ( Figure 37 The thickness of the metal portion of the plate [mm] is as follows: Figure 37 As shown in the table. [Pressure Resistance Test Evaluation]

[0265] The resulting (final) drawn thinned can (DI can) was evaluated for pressure resistance using the following pressure resistance test method. Figure 38 The evaluation results are presented in the table. [Pressure Resistance Test Method]

[0266] With the cup-shaped container filled with water, the open end is sealed with a stopper equipped with a water supply pipe. Next, pressurized water is pumped into the cup-shaped container through the water supply pipe. The internal pressure of the cup-shaped container rises, and at a certain moment, the dome-shaped panel instantly deforms by flipping outwards (bending deformation). Typically, this deformation occurs simultaneously with a sharp drop in the internal pressure of the can (DI can). The highest internal pressure during this period is taken as the pressure resistance value (pressure resistance) [MPa].

[0267] like Figure 38 The evaluation results in the table show that the drawn thinned can (DI can) formed in Example 9 (as the final formed body) is equivalent to a 350mL can, and its can weight (as the weight of the trimmed metal portion) is 9.9g. Figure 38 Figure 38 The evaluation results show that the thickness [mm] of the metal portion was increased over a wide range, including the necessary range for improved pressure resistance on the (reformed) annular protrusion at the bottom of the can. As a result, the DI can achieved a preferred pressure resistance (pressure value [MPa]).

[0268] Furthermore, by applying the method shown in Example 9, which yields such results, to a process as part of a series of can-making processes, it is possible to manufacture cans that are thinner than the original plate thickness while maintaining pressure resistance, in order to save material resources and reduce weight.

[0269] The embodiments of the present invention have been described in detail above with reference to the accompanying drawings. However, the specific structure is not limited to these embodiments, and design changes that do not depart from the spirit and scope of the present invention are also included in the present invention. In addition, the examples described above can be generally combined with each other as long as their purpose and structure do not have any particular contradictions or problems. Symbol Explanation

[0270] 1: Molded material, 3: Can lid, 6: Can bottom, 11, 41, 51: Sheet metal, 11a, 41a, 51a: Preformed part, 12, 23, 31, 45, 45A: Central panel, 13, 32, 32a, 32A, 62a: Annular protrusion, 14, 25, 421, 421A: Outer panel, 420, 521: Outer panel, 22, 44, 54: Central protrusion, 24, 46, 56: Side wall, 26, 47, 57: Outer curved part, 30, 30A: (Before can lid is shaped) Intermediate molded body of can lid, 30a-1: Molded body, 33: Second outer wall, 34: Curved part, 42, 52: Sheet-like part, 4 3, 53: Outer periphery (side), 60: (Before the bottom shape is formed) Middle part of the bottom, 121, 141, 311: Curved part, 131: Inner peripheral wall, 132: Curved protrusion, 133: Outer peripheral wall, 321, 321a, 321A: Panel wall (inner peripheral wall), 322, 322a, 322A: Wall-clamping radius (curved protrusion), 323, 323a, 323A: First wall-clamping part (first outer peripheral wall), 522: Annular curved bottom, 55, 61: Dome panel (central panel), 62: Annular protrusion at the bottom, 63: Bell part (second outer peripheral wall), 621: Dome panel wall (inner peripheral wall), 622, 622a: Bottom radius (curved protrusion), 623: Lower part of the bell (first outer peripheral wall).

[0271] 1E: Formed material; 11E, 41E, 51E: Sheet metal; 11Ea, 41Ea: Preformed part; 12E, 22E, 31E, 31Ec, 45E, 45Eb, 54E: Center panel portion (central plate portion); 121E, 141E, 311E: Bending end; 13E, 32E, 32Ea, 32Eb, 32Ec, 62Ea, 82Ea: Annular protrusion; 131E: Inner peripheral wall portion; 132E: Bending protrusion; 133E: Outer peripheral wall portion; 14E, 21E, 421E, 421Eb, 521E: Outer peripheral panel portion (outer peripheral plate portion); 23E, 46E, 55E, 61E, 63E, 81E: Side wall portion; 24E... 47E, 57E, 62Eb: Annular curved portion; 3E, 3Ec: Can lid; 30E, 40Eb: Can lid intermediate molded body; 321E: Panel wall portion (inner peripheral wall portion); 322E, 322Ea, 322Eb, 322Ec, 822Ea: Clamping radius portion (curved protrusion); 323E: First clamping wall portion (first outer peripheral wall portion); 33E: Second clamping wall portion (second outer peripheral wall portion); 34E: Curved portion; 42E: Plate-like portion; 420E: Outer panel portion (outer panel portion); 43E: Outer peripheral side portion; 52E: Plate-like portion; 53E: Outer peripheral side portion; 56E, 64E: Central protrusion; 10E: Can bottom; 91E: Plate; 91Ea: Pre-formed Part, 92E: Plate-shaped portion, 921E: Outer panel portion (outer plate portion), 922E: Outer peripheral panel portion (outer peripheral plate portion), 93E: Outer peripheral side portion, 94E: Dome panel portion (central plate portion), 94Ea: Center panel portion (central plate portion), 95E: Side wall portion, 96E: Annular curved portion, 100E: Middle molded part of the bottom of the can, 101E: Dome panel portion (central plate portion), 102E: Annular protrusion of the bottom of the can, 102Ea: Annular protrusion, 112Ea: Bottom radius portion (curved protrusion), 103E: Bell portion (second outer peripheral wall portion), 151E: Dome panel wall portion (inner peripheral wall portion), 152E: Bottom radius portion (curved protrusion), 153E: Bell Lower part of the bell (first outer peripheral wall), 921E: outer outer panel part (outer outer plate part), 922E: outer peripheral panel part (outer peripheral plate part), 510E: intermediate molded body (before re-forming) of the bottom of the can, 511E: dome panel part (of the intermediate molded body), 512E: annular protrusion part (of the intermediate molded body), 513E: dome panel wall part (of the intermediate molded body), 514E: bottom radius part (of the intermediate molded body), 515E: lower part of the bell (of the intermediate molded body), 516E: bell part (of the intermediate molded body), 520E: final molded body (after re-forming) of the bottom of the can, 522E: dome panel part (of the final molded body), 523E: annular protrusion part of the bottom of the can (of the final molded body).

Claims

1. A method for forming a sheet material, characterized in that, The molding method includes: The process of molding specific plate parts and sidewall parts; The process of forming the annular curved portion connected to the sidewall portion; The process of forming at least the annular protrusion that selectively increases the thickness of the plate by deforming the annular curved portion; In the process of forming the annular protrusion, The annular protrusion is formed by supporting the annular bend in a second direction that is movable relative to the first direction of the protrusion, while applying a pushing force in the first direction to the specific plate portion, thereby generating a compressive stress in the second direction in the sidewall portion and causing at least a portion of the plate constituting the sidewall portion to move on the support surface of the supporting member, thereby selectively increasing the thickness of the plate.

2. A method for forming a sheet material, characterized in that, The molding method includes: The process of forming a central protrusion consisting of a central plate portion and sidewall portions on its outer periphery in the plate-shaped portion of a sheet material; The process of forming an outer peripheral curved portion on the outer periphery of the side wall portion; The process of forming annular protrusions that selectively increase the thickness of the plate by deforming at least the outer peripheral curved portion; In the process of forming the annular protrusion, By supporting the outer peripheral curved portion with a support member that can move relatively in the protrusion direction of the central protrusion, and simultaneously applying a pushing force to the central protrusion in the opposite direction of the protrusion direction, compressive stress in the protrusion direction is generated in the side wall portion, and at least a portion constituting the side wall portion moves on the support surface of the support member, thereby forming the annular protrusion with selectively increased plate thickness.

3. The molding method as described in claim 2, characterized in that, In the process of forming the annular protrusion, at least a portion constituting the sidewall portion is moved outward from the support surface of the support member toward the central protrusion.

4. The molding method as described in claim 2 or 3, characterized in that, The plate is composed of a material that is primarily metal.

5. A method for forming a can lid, characterized in that, The molding method as described in claim 2 is included as part of the entire process.

6. The method for forming a can lid as described in claim 5, characterized in that, After the process of forming the annular protrusion, As a process of shaping into the form of a can lid, The process of forming the card wall section.

7. A method for forming the bottom of a can, characterized in that, The molding method as described in claim 2 is included as part of the entire process.

8. The method for forming the bottom of a can as described in claim 7, characterized in that, After the process of forming the annular protrusion, This is the process of shaping the bottom of the can. The process must at least have the shape of the annular protrusion at the bottom of the can.

9. A method for forming a sheet material, characterized in that, The molding method includes: The process of forming an outer peripheral plate by forming a side wall portion that rises upward from the outer periphery of the central plate while forming the central plate; The process of forming an annular curved portion on the inner circumferential side of the sidewall portion; The process of forming at least the annular protrusion that selectively increases the thickness of the plate by deforming the annular curved portion; In the process of forming the annular protrusion, The annular protrusion is formed by supporting the annular bend in a second direction that is movable relative to the first direction of the protrusion, while applying a pushing force in the first direction to the outer peripheral plate, thereby generating a compressive stress in the second direction in the sidewall portion and causing at least a portion of the plate constituting the sidewall portion to move on the support surface of the supporting member, thereby selectively increasing the thickness of the plate.

10. The molding method as described in claim 9, characterized in that, In the process of forming the annular protrusion, at least a portion of the plate constituting the sidewall portion is moved inward toward the outer peripheral plate portion on the support surface of the support member.

11. The molding method as described in claim 9, characterized in that, The plate is composed of a material that is primarily metal.

12. A method for forming a can lid, characterized in that, The molding method as described in claim 9 is included as part of the entire process.

13. The method for forming a can lid as described in claim 12, characterized in that, After the process of forming the annular protrusion, As a process of shaping into the form of a can lid, The process of forming the card wall section.

14. A method for forming the bottom of a can, characterized in that, The molding method as described in claim 9 is included as part of the entire process.

15. The method for forming the bottom of a can as described in claim 14, characterized in that, After the process of forming the annular protrusion, As a process of shaping the bottom of the can. The process must at least have the shape of the annular protrusion at the bottom of the can.

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