Plate material molding method

Abstract

To provide a plate material molding method capable of increasing plate thickness of an annular projection in a wide range at a simple manufacturing step while preventing unintended deformation of a material by relative push-in.SOLUTION: A plate material molding method has: a step which molds a central projection composed of a central plate part and a side wall part on an outer peripheral side in a plate-like part of a plate material; a step for molding an outer peripheral curved part on the outer periphery of the side wall part; and a step for deforming at least the outer peripheral curved part and molding an annular projection where plate thickness is selectively increased. In the step for molding the annular projection part, a pressing force is given to the central projection in the direction opposite the projection direction while the outer peripheral curved part is supported by a support member relatively movable in a projection direction of the central projection, and at least a part of what composes the side wall part on a support surface of the support member is moved while compression stress in the projection direction of the side wall part is generated, so that the annular projection whose plate thickness selectively increases is molded.SELECTED DRAWING: Figure 3

Description

[Technical field]

[0001] The present invention relates to a method for forming a plate material to be used for, for example, a can lid, a can bottom, etc. [Background technology]

[0002] Metal can containers (metal cans) are required to have as small a thickness as possible while still maintaining pressure resistance in order to conserve material resources, reduce weight, etc. For example, in the case of can lids and can bottoms, so-called buckling can occur due to an increase in internal pressure, and so there is a strong demand for ideas to maintain the pressure resistance.

[0003] For example, in order to reduce the thickness of plate material that will become the can lid, can bottom, etc. while maintaining its pressure resistance, it is known to form an annular protrusion consisting of an inner wall portion, a curved convex portion, and a part of the outer wall portion on the outer side of the central plate portion that will become the lid surface, bottom surface, etc., and to increase the plate thickness of the curved convex portion.

[0004] For example, Patent Document 1 describes that in a can lid having a center panel portion (central plate portion), a panel wall portion (inner peripheral wall portion), a chuck wall radius portion (curved convex portion), a chuck wall portion (outer peripheral wall portion), and a curl portion, the plate thickness t2 of the lower end of the panel wall portion is made greater than the plate thickness t1 of the center panel portion (t2>t1), thereby improving the pressure resistance while reducing the plate thickness of the plate material. Patent Document 1 also describes that the plate thickness t3 of the chuck wall radius portion is made greater than the plate thickness t1 of the center panel portion (t3>t1), indicating the necessary range for improving the pressure resistance. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent Publication No. 2022-16093 Summary of the Invention [Problem to be solved by the invention]

[0006] However, when forming an annular protrusion on a plate material by a conventional method, such as the can lid manufacturing method described in Patent Document 1, if the annular protrusion is formed in a single stroke using upper and lower dies, the plate thickness of the inner peripheral side of the annular protrusion increases significantly, and it is not possible to increase the plate thickness of the annular protrusion over a wide range. In order to increase the plate thickness of the annular protrusion over a wide range using the conventional method, the central plate portion must be pressed relative to the plate portion in multiple stages, and a die of a different shape must be used each time, which makes the manufacturing process complicated.

[0007] Furthermore, by applying relative pressure to the plate material, the plate material not only increases in thickness but also tries to release stress by deformation and material flow, but with conventional methods, the plate material is prone to flow toward the outer peripheral wall, making it difficult to maintain the required shape for, for example, a can lid or bottom. In other words, the range in which relative pressure can be applied while maintaining the shape is narrow, and depending on the required performance, there are cases in which a sufficient increase in plate thickness cannot be achieved.

[0008] The present invention aims to address such circumstances, that is, to provide a method for forming a sheet material that can increase the sheet thickness of the annular protrusion over a wide range in a simple manufacturing process while preventing unintended deformation of the material due to relative pressing (pressing). [Means for solving the problem]

[0009] In order to solve such problems, the method for forming a plate material of the present invention has the following features. The method includes the steps of: forming a central protrusion consisting of a central plate portion and a side wall portion on its outer periphery in a plate-shaped portion of a plate material; forming an outer periphery curved portion on the outer periphery of the side wall portion; and deforming at least the outer periphery curved portion to form an annular protrusion having a selectively increased plate thickness, wherein in the step of forming the annular protrusion, the outer periphery curved portion is supported by a support member that is movable relatively in the protruding direction of the central protrusion, and a pressing force is applied to the central protrusion in the opposite direction to the protruding direction, thereby generating a compressive stress in the protruding direction in the side wall portion, while moving at least a portion that constituted the side wall portion on the support surface of the support member, thereby forming the annular protrusion having a selectively increased plate thickness. Effect of the Invention

[0010] According to the sheet metal forming method of the present invention having such characteristics, it is possible to increase the sheet thickness of the annular protrusion over a wide range through a simple manufacturing process while preventing unintended deformation of the material due to relative pressing (pressing). [Brief description of the drawings]

[0011] [Figure 1] FIG. 1 is a side view of a plate having an annular protrusion in schematic form. [Diagram 2] FIG. 1 is a flow diagram showing a process for forming a plate material having an annular protrusion in a schematic form. [Diagram 3] 1A to 1C are explanatory diagrams of a forming process of a plate material having an annular protrusion in a schematic form. [Figure 4] FIG. 2 is a side view of the can lid in the first embodiment. [Diagram 5] FIG. 2 is a flow chart showing a can lid forming process in the first embodiment. [Figure 6] FIG. 2 is a first explanatory view of a can lid forming process in the first embodiment. [Figure 7] FIG. 4 is a second explanatory view of the can lid forming process in the first embodiment. [Figure 8] 1 is a side cross-sectional view showing a schematic configuration of a forming device used in a can lid forming process in the first embodiment. [Figure 9] FIG. 4 is an explanatory diagram of a ring-shaped protrusion forming step (plate thickness increasing forming) step and a shape forming step of the can lid forming process in the first embodiment. [Figure 10A] FIG. 4 is a first explanatory view of an annular protrusion forming (plate thickness increasing) step in the can lid forming process in the first embodiment. [Figure 10B] FIG. 4 is a second explanatory view of the annular protrusion forming (plate thickness increasing forming) step in the can lid forming process in the first embodiment. [Figure 11A] FIG. 2 is a partial end view partially showing a side end surface of the can end preform in the first embodiment. [Figure 11B] FIG. 2 is a partial end view partially showing a side end surface of the can end preform after an annular protruding portion forming (plate thickness increasing forming) step in the first embodiment. [Figure 12] FIG. 11 is an explanatory diagram of an annular protrusion forming (plate thickness increasing) step in an example of the first embodiment. [Figure 13] FIG. 11 is a diagram showing the lip height [mm] versus the support force [kN] in an example of the first embodiment. [Figure 14A] FIG. 2 is a partial end view partially showing a side end surface of a can end preform after an annular protruding portion forming (plate thickness increasing forming) step in an example of the first embodiment. [Figure 14B] FIG. 14B is a partially enlarged view showing a part of FIG. 14A. [Figure 15] FIG. 13 is a diagram showing plate thicknesses [mm] at measurement points A to F of the annular protrusion relative to the support force [kN] during the annular protrusion molding (plate thickness increasing molding) process in an example of the first embodiment. [Figure 16] FIG. 11 is an explanatory diagram of a can bottom forming step in the second embodiment. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0012] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts having the same function, and duplicated descriptions in each drawing will be omitted as appropriate.

[0013] [Summary form] A method for forming a plate material, which is a general embodiment (summary form) of the present invention, forms a formed material 1 shown in Fig. 1. The formed material 1 has a center panel portion (center plate portion) 12 which is a generally circular, generally flat surface located approximately at the center of a generally disk-shaped plate material 11, an annular protruding portion 13 located on the outer periphery thereof, and an outer panel portion (outer plate portion) 14 located further on the outer periphery thereof.

[0014] The plate material 11 is made of a material mainly made of metal. The material mainly made of metal is not particularly limited, and may be, for example, a single metal material such as aluminum, an aluminum alloy, or steel, or a clad material of these metals, or a composite metal material in which one or both sides of these metals are subjected to a surface treatment, painting, lamination, or the like.

[0015] A curved portion 121 is formed on the outer edge of the center panel portion 12, and an inner peripheral wall portion 131 is formed so as to extend downward in a substantially straight line from the end of the curved portion 121. The curved convex portion 132 is a curved portion formed so that its inner peripheral end is connected to the lower end of the inner peripheral wall portion 131 and its outer peripheral end is connected to the outer peripheral wall portion 133. The outer peripheral wall portion 133 is formed so as to extend upward in a substantially straight line from the upper end of the outer peripheral side of the curved convex portion 132 and to be connected to the curved portion 141 of the outer panel portion 14. The annular protrusion 13 is composed of the inner peripheral wall portion 131, the curved convex portion 132, and the outer peripheral wall portion 133.

[0016] The forming process of this formed material 1 includes a blank punching step S1, a central protruding portion forming step S2, a peripheral curved portion forming step S3, and an annular protruding portion forming (plate thickness increasing forming) step S4, as shown in Fig. 2. In these forming steps (S1 to S4), the shape of the plate material 11 is changed as shown in states a1 to a5 in Fig. 3 to form the formed material 1 in state a6.

[0017] In the blank punching process S1, the shape of the blank varies depending on the target product (for example, it may be an ellipse, a polygon, etc.), but for example, the plate material 11 to be processed is formed into an approximately disk shape using upper and lower punching tools (not shown) for punching the plate material 11 into an approximately disk shape (state a1 in Figure 3).

[0018] In the central protrusion forming process S2, for example, using upper and lower central drawing tools (not shown) for performing drawing on the approximately central portion of the approximately disk-shaped plate material 11, the outer panel portion (outer plate portion) 25 of the approximately disk-shaped plate material 11 is fixed while drawing is performed on its inner peripheral side, thereby forming a central protrusion 22 consisting of a center panel portion (central plate portion) 23 and a side wall portion 24 on its outer peripheral side, as shown in state a2 in Figure 3.

[0019] In the outer peripheral curved portion forming step S3 and the annular protruding portion forming (plate thickness increasing forming) step S4, for example, forming processing is performed on the plate material 11 on which the central protruding portion 22 has been 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 U12, and an annular side wall guide tool U13 located therebetween. The lower tool L1 includes an annular lower outer tool L11, a lower central tool L12, and an annular curved portion support tool (support member) L13 located therebetween.

[0020] In the outer periphery curved portion forming process S3, for example as shown in state a3 in Fig. 3, the plate material 11 on which the central protrusion 22 consisting of the center panel portion 23 and the side wall portion 24 has been formed is placed on the lower tool L1, and then the upper outer tool U11 is lowered. As a result, the outer panel portion (outer plate portion) 25 of the plate material 11 is sandwiched and fixed between the abutment surface U11a of the upper outer tool U11 and the abutment surface L11a of the lower outer tool L11. This fixing of the outer panel portion is continued from this point on until the annular protrusion forming (plate thickness increasing forming) process S4 is completed.

[0021] In this state, in the outer periphery curved portion forming process S3, the upper central tool U12 and the side wall guide tool U13 are lowered as shown in states a3 and a4 in FIG. 3. At this time, the lowering of the upper central tool U12 pushes down the lower central tool L12 so that the abutment surface U12a of the upper central tool U12 sandwiches the center panel portion 23 between the abutment surface L12a of the lower central tool L12 (state a4 in FIG. 3). In addition, the lowering of the side wall guide tool U13 positions the side wall portion 24, which is inclined downward and outward, between the inner guide surface U13a of the side wall guide tool U13 and the outer guide surface L12b of the lower central tool L12. By positioning the side wall guide tool U13 and the lower central tool L12 around the side wall portion 24, when a compressive stress is applied to the side wall portion 24 in the subsequent annular protrusion forming (plate thickness increasing forming) process S4, the buckling of the side wall portion 24 due to the compressive stress can be prevented.

[0022] The upper central tool U12 descends so that the height position of its contact surface U12a approaches the height position of the contact surface (support surface) L13a of the curved portion support tool (support member) L13. That is, the curved portion support tool (support member) L13 is relatively movable in the protruding direction (upward direction) of the central protruding portion 22. This curved portion support tool L13 applies a support force toward the protruding direction to the plate material 11 on its contact surface (support surface) L13a. Therefore, by the descent of the upper central tool U12 and the side wall guide tool U13, the outer periphery side of the side wall portion 24 is supported by the curved portion support tool L13 that applies this support force, and a peripheral curved portion 26 having a curved shape that follows the shape of the contact surface L13a is formed. In this way, a preform 11a having a peripheral curved portion 26 is formed from the plate material 11 (state a4 in FIG. 3).

[0023] In the annular protrusion molding (plate thickness increasing molding) process S4, for example, as shown in states a4 and a5 of Figure 3, while the outer peripheral curved portion 26 of the molded preform 11a is supported by the abutment surface (support surface) L13a of the curved portion support tool (support member) L13, a pressing force is applied to the central protrusion 22 in the direction opposite to its protruding direction.

[0024] At this time, the upper central tool U12 continuously descends so as to press down the lower central tool L12 with its contact surface U12a. This applies a pressing force to the center panel portion 23 sandwiched between the contact surface U12a and the contact surface L12a of the lower central tool L12, and presses the center panel portion 23 downward. At the same time, the side wall portion guide tool U13 positions the side wall portion 24 between its inner guide surface U13a and the contact surface L12b of the lower central tool L12, thereby preventing the side wall portion 24 from buckling due to the compressive stress applied to the side wall portion 24. As a result, the upper central tool U12 applies a pressing force to the outer circumferential curved portion 26 via the side wall portion 24 that is greater than the supporting force of the curved portion support tool L13.

[0025] By forming the annular protrusion (thickness increasing formation) by such continuous descent of the upper central tool U12 and the side wall guide tool U13, the outer peripheral curved portion 26 is deformed, and at least a portion that constituted the side wall portion 24 on the contact surface L13a of the curved portion support tool L13 is moved outwardly of the central protrusion 22 while compressive stress in the protruding direction is generated in the side wall portion 24. As a result, the annular protrusion 13 is formed with the plate thickness selectively increased based on the moved portion (state a5 in FIG. 3).

[0026] After forming the formed material 1 having this annular protrusion 13, the formed material 1 is removed from the upper tool U1 and the lower tool L1 to obtain the formed material 1 in state a6 in Fig. 3. In the formed material 1, the annular protrusion 13 has an increased thickness over a wide area including the curved convex portion 132 between the inner circumferential wall portion 131 and the outer circumferential wall portion 133.

[0027] In this manner, in the method of forming the sheet material 11 in the outline form, the center panel portion 23 is pressed (pressed) relative to one another continuously (in one stroke) using the same device (upper and lower dies) having an upper tool U1 and a lower tool L1. In other words, this method of forming the outline form does not perform pressing in multiple stages using dies of different shapes each time, but can form the annular protrusion 13 with an increased sheet thickness over a wide range in this manner using a simple manufacturing process.

[0028] Instead of the example described here, the forming process of the formed material 1 may use the same device (upper and lower dies) from the blank punching process S1 to the annular protruding portion forming (thickness increasing) process S4. Alternatively, the forming process of the formed material 1 may use a device (upper and lower dies) different from the device (device having an upper tool U1 and a lower tool L1) used in the annular protruding portion forming (thickness increasing) process S4 from the blank punching process S1 to the outer circumferential curved portion forming process S3. In this case, the preform 11a is prepared in advance by this different device, and the preform 11a is sequentially placed between the upper tool U1 and the lower tool L1 described above.

[0029] In addition, in this schematic embodiment, an example in which the upper central tool U12 is lowered relative to the curved portion support tool (support member) L13 so as to approach the curved portion support tool (support member) L13 has been described, but the present invention is not limited to this. The curved portion support tool (support member) L13 is relatively movable in the protruding direction (upward direction) of the central protrusion 22. Therefore, instead of the example described here, the curved portion support tool (support member) L13 may be raised relative to the upper central tool U12 so as to approach the upper central tool U12, thereby applying a pressing force toward the protruding direction to the plate material 11 on the contact surface (support surface) L13a.

[0030] In this case, the center panel portion 23 is sandwiched and fixed between the upper central tool U12 and the lower central tool L12, and in this state, the lower outer tool L11 and the curved portion support tool (support member) L13 rise so as to push up the upper outer tool U11 and the side wall guide tool U13. As a result, an outer peripheral curved portion 26 having a curved shape that follows the shape of the contact surface L13a of the curved portion support tool L13 is formed on the outer periphery of the side wall portion 24, and then the annular protrusion 13 is formed.

[0031] Hereinafter, first and second embodiments, which are specific embodiments of the present invention, will be described. In the first and second embodiments, a description of the same configuration as in the above-mentioned outline embodiment or the same configuration as each other will be omitted.

[0032] [First embodiment] The method for forming a plate material in the first embodiment is for forming a can lid 3, as shown in Fig. 4, as a formed material. The can lid 3 has a center panel portion (central plate portion) 31, a panel wall portion (inner peripheral wall portion) 321, a chuck wall radius portion (curved convex portion) 322, a chuck wall portion consisting of a first chuck wall portion (first outer peripheral wall portion) 323 and a second chuck wall portion (second outer peripheral wall portion) 33, and a curl portion 34. Here, the panel wall portion 321, the chuck wall radius portion 322, and the first chuck wall portion 323 form an annular protruding portion 32.

[0033] The center panel portion (central plate portion) 31 is located approximately in the center of the can lid 3 and is composed of a substantially circular, substantially flat surface. When the can lid 3 is of a stay-on-tab type, the center panel portion 31 is provided with a tab, score, or the like for opening.

[0034] A curved portion 311 is formed on the outer edge of the center panel portion 31, and a panel wall portion (inner peripheral wall portion) 321 is formed so as to extend downward in a substantially straight line from the end of the curved portion 311. The chuck wall radius portion (curved convex portion) 322 is a curved portion formed so that its inner peripheral end is connected to the lower end of the panel wall portion 321 and its outer peripheral end is connected to a first chuck wall portion (first outer peripheral wall portion) 323.

[0035] The first chuck wall portion (first outer peripheral wall portion) 323 extends upward in a substantially linear manner from the upper end of the outer peripheral side of the chuck wall radius portion (curved convex portion) 322. The second chuck wall portion (second outer peripheral wall portion) 33 extends in a substantially linear manner from the upper end of the outer peripheral side of the first chuck wall portion 323 so as to be inclined upward and outward, and is formed so that its upper end is connected to the curved portion of the curl portion 34.

[0036] This method of forming can lids 3 includes the method of forming the sheet material 11 in the above-mentioned outline form as part of all steps. That is, as shown in Fig. 5, this method of forming can lids 3 includes a blank punching step S11, an outer periphery drawing step S12, a central protruding part forming step S13, an outer periphery curved part forming step S14, an annular protruding part forming (sheet thickness increasing forming) step S15, and a can lid shape forming step S16. In these forming steps (S11 to S16), the shape of the sheet material 41 is changed as shown in states a11 to a18 in Figs. 6 and 7 to form the can lid 3 in state a19 in Fig. 7.

[0037] In the blank punching step S11, for example, upper and lower punching tools (not shown) for punching the plate material 41 to be processed into a substantially disk shape are used to form the plate material 41 into a substantially disk shape (state a11 in FIG. 6).

[0038] The plate material 41 is made of a material mainly made of metal. The metal material is not particularly limited, but may be, for example, a single metal material such as aluminum, an aluminum alloy, or steel, or a clad material of these metals, or a composite metal material in which one or both sides of these metals are subjected to a surface treatment, painting, lamination, or the like.

[0039] In the outer periphery drawing process S12, for example, by using upper and lower outer periphery drawing tools (not shown) for drawing the outer periphery of the substantially disk-shaped plate material 41, a plate-shaped portion on the inner periphery side of the outer periphery of the substantially disk-shaped plate material 41 shown in state a11 in Fig. 6 is fixed and the outer periphery is drawn. As a result, an outer periphery (side surface) 43 extending in a direction substantially perpendicular (downward) to the plate-shaped portion 42 is formed on the outer periphery side of the plate-shaped portion 42 of the plate material 41 as shown in state a12 in Fig. 6.

[0040] In the central protrusion forming step S13, for example, for the plate material 41 in the state a12 of Fig. 6, a central drawing upper and lower tools (not shown) for drawing the approximate center of the plate-shaped portion 42 are used to draw the inner periphery of the plate-shaped portion 42 while fixing the outer panel portion (outer plate portion) 420, which is the outer peripheral portion of the plate-shaped portion 42. As a result, as shown in the state a13 of Fig. 6, a central protrusion 44 consisting of a center panel portion (center plate portion) 45 and a side wall portion 46 on the outer peripheral side is formed on the inner periphery side of the outer panel portion (outer plate portion) 421 of the plate material 41. The shape of the center panel portion (center plate portion) 45 is not particularly limited, but may have a curved (dome) shape that gently protrudes in the protruding direction of the central protrusion 44, as exemplified in Fig. 6.

[0041] In the outer peripheral curved portion forming step S14 and the annular protruding portion forming (plate thickness increasing forming) step S15, the plate material 41 with the central protruding portion 44 formed therein (state a13 in FIG. 6) is formed using a forming device M1 having an upper tool U2 and a lower tool L2 shown in FIG. 8, for example. As shown in FIG. 8 and state a14 in FIG. 6, the upper tool U2 includes an annular upper outer tool U21, an upper central tool U22, and an annular side wall guide tool U23 located therebetween. 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 therebetween.

[0042] 8, the forming device M1 has an upper tool U2 equipped with cushion pins Ua1 and Ua2 connected to an air cylinder, and a lower tool L2 equipped with cushion pins La1 and La2 connected to an air cylinder. In the upper tool U2, the upper central tool U22 and the side wall guide tool U23 can be moved up and down by the cushion pin Ua1 connected to an air cylinder, and the upper outer tool U21 can be moved up and down by the cushion pin Ua2 connected to an air cylinder.

[0043] In the lower tool L2, the lower central tool L22 and the curved portion support tool (support member) L23 can be moved up and down by cushion pins La1 connected to an air cylinder, and the lower outer tool L21 can be moved up and down by cushion pins La2 connected to an air cylinder. Note that the forming device M1 may be provided with elastic members such as spring members instead of the cushion pins Ua1, Ua2, La1, and La2 connected to such air cylinders.

[0044] In the outer peripheral curved portion forming process S14, for example as shown in state a14 in Fig. 6, the plate material 41 with the central protrusion 44 formed therein is placed on the lower tool L2, and then the upper outer tool U21 is lowered. As a result, the outer panel portion 421 of the plate material 41 is sandwiched and fixed between the abutment surface U21a of the upper outer tool U21 and the abutment surface L21a of the lower outer tool L21. This fixing of the outer panel portion 421 is continued from this point on until the annular protrusion forming (plate thickness increasing forming) process S15 is completed.

[0045] In this state, in the outer periphery curved portion forming process S14, the upper central tool U22 and the side wall guide tool U23 are lowered. At this time, as shown in states a14 and a15 in Fig. 6, the lowering of the upper central tool U22 presses down the lower central tool L22 so that the abutment surface U22a of the upper central tool U22 sandwiches the center panel portion 45 between the abutment surface L22a.

[0046] The upper central tool U22 descends so that the height position of its contact surface U22a approaches the height position of the contact surface (support surface) L23a of the curved portion support tool (support member) L23. That is, the curved portion support tool (support member) L23 is relatively movable in the protruding direction (upward direction) of the central protruding portion 44. This curved portion support tool L23 applies a support force toward the protruding direction to the plate material 41 on its contact surface (support surface) L23a. Therefore, by the descent of the upper central tool U22 and the side wall guide tool U23, the outer periphery side of the side wall portion 46 is supported by the curved portion support tool L23 that applies this support force, and a curved outer periphery curved portion 47 is formed in a curved shape that follows the shape of the contact surface L23a. In this way, a preform 41a having the outer periphery curved portion 47 is formed from the plate material 41 (state a15 in FIG. 6).

[0047] In the annular protrusion molding (plate thickness increasing process) process S15 (state a15, state a16 in Figure 6), for example, while the outer peripheral curved portion 47 of the molded preform 41a is supported by the abutment surface (support surface) L23a of the curved portion support tool (support member) L23, a pressing force is applied to the central protrusion 44 in the direction opposite to its protruding direction.

[0048] At this time, the upper central tool U22 continuously descends so as to press down the lower central tool L22 with its contact surface U22a. This applies a pressing force to the center panel portion 45 sandwiched between the contact surface U22a and the contact surface L22a of the lower central tool L22, and presses the center panel portion 45 downward. At the same time, the side wall portion guide tool U23 positions the side wall portion 46 between its inner guide surface U23a and the outer guide surface L22b of the lower central tool L22, thereby preventing the side wall portion 24 from buckling due to the compressive stress applied to the side wall portion 46. This causes the upper central tool U22 to apply a pressing force to the outer peripheral curved portion 47 via the side wall portion 46.

[0049] Such pressing (thickness increasing forming) caused by the continuous descent of the upper central tool U22 and the side wall guide tool U23 presses the center panel portion 45 downward and deforms the outer circumferential curved portion 47. This thickness increasing forming also causes compressive stress in the protruding direction of the central protrusion 44 in the side wall portion 46, while at least a portion that constituted the side wall portion 46 is moved outwardly of the central protrusion 44 on the contact surface L23a of the curved portion support tool L23.

[0050] Through such an annular protrusion forming (thickness increasing forming) step S15, an intermediate formed can lid 30 (state a16 in FIG. 6 ) is formed (before the can lid shape is formed) having an annular protrusion 32a whose thickness is selectively increased based on the moved portion. This annular protrusion 32a has an increased thickness over a wide range including the chuck wall radius portion (curved convex portion) 322a.

[0051] Thus, in the method for forming the plate material 41 of the first embodiment, the center panel portion 45 is continuously (in one stroke) pressed relative to one another using the same device (upper and lower dies) having the upper tool U2 and the lower tool L2. That is, the forming method of the first embodiment does not perform this pressing in multiple stages using dies of different shapes each time, but can form the annular protrusion 32a with an increased plate thickness over a wide range in this simple manufacturing process.

[0052] After the intermediate can lid body 30 (before the can lid shape is formed) having the annular protruding portion 32a is formed in this manner, the intermediate can lid body 30 is removed from the upper tool U2 and the lower tool L2.

[0053] The can lid shape forming step S16 is a step of reforming the shape of the intermediate formed body 30 of the can lid to form it into the shape of a can lid. This can lid shape forming step S16 includes a step of forming a chuck wall portion consisting of a first chuck wall portion (first outer peripheral wall portion) 323 and a second chuck wall portion (second outer peripheral wall portion) 33 shown in a later state a19.

[0054] The can lid shape forming process S16 may further include at least one or both of a known process (not shown) of forming a curled portion 34 outer circumferentially of the annular protrusion 32a (or the annular protrusion 32 after forming) and a process of forming the center panel portion (central plate portion) 45 into a desired shape, for example, into a substantially flat surface, in any order with or simultaneously with the process of forming the above-mentioned chuck wall portion.

[0055] In the can end shape forming step S16, as shown in state a17 in Fig. 7, the shape of the intermediate formed body 30 of the can end is reformed using a can end shape forming device M2 having an upper tool U3 and a lower tool L3. The upper tool U3 has an upper outer tool U31, an upper central tool U32, and an annular processing tool U33 located therebetween. The lower tool L3 has an annular lower outer tool L31 and a lower central tool L32. The lower tool L3 also has an annular annular protrusion support tool L33 located between the lower outer tool L31 and the lower central tool L32.

[0056] In this can lid shape forming step S16, as shown in state a17 of Fig. 7, after placing the intermediate formed body 30 of the can lid (before the can lid is shaped) on the lower tool L3, the upper outer tool U31, the upper central tool U32, and the processing tool U33 may be lowered, for example, simultaneously to perform the can lid shape forming step S16. Alternatively, depending on the shape of the can lid, the timing of the descent of the upper outer tool U31, the upper central tool U32, and the processing tool U33 may be appropriately changed.

[0057] At this time, as the upper central tool U32 descends, the annular protrusion 32a is supported by the contact surface (support surface) L33a of the annular protrusion support tool L33, and the annular protrusion 32a between the lower central tool L32 and the lower outer tool L31 is formed into the annular protrusion 32 (state a18 in FIG. 7) having a shape that conforms to the contact surface (support surface) L33a of the annular protrusion support tool L33. That is, at this time, the first chuck wall portion (first outer peripheral wall portion) 323 (see state a19) of the chuck wall portion is formed.

[0058] At this time, the upper outer tool U31 descends, so that its contact surface U31a comes into contact with the outer panel portion 421 on the contact surface (support surface) L31b of the lower outer tool L31, thereby fixing the outer panel portion 421. In this state, the processing tool U33 descends, so that the outer panel portion 421 is sandwiched between the contact surface U33a and the contact surface L31a, thereby forming a second chuck wall portion (second outer peripheral wall portion) 33 (see state a19) that conforms to the shapes of the lower outer tool L31 and the processing tool U33. In this way, a chuck wall portion (see state a19) consisting of the first chuck wall portion (first outer peripheral wall portion) 323 and the second chuck wall portion (second outer peripheral wall portion) 33 on the outer periphery side of the first chuck wall portion (first outer peripheral wall portion) 323 is formed.

[0059] At this time, the curled portion 34 can also be formed on the outer periphery of the lid. In this case, the lower tool L3 may be provided with a curling tool (not shown) on the outer periphery of the lower outer tool L31. As described above, when the processing tool U33 descends with the outer panel portion 421 fixed, the outer panel portion 421 sandwiched between the abutment surface U33a and the abutment surface L31a flows toward the outer periphery. When the curling tool (not shown) descends in this state, the curled portion 34 is formed in a shape that conforms to the abutment surface U31a of the upper outer tool U31 and the abutment surface (not shown) of the curling tool (not shown) (state a18 in FIG. 7).

[0060] At this time, the center panel portion (central plate portion) 45 can also be formed into a desired shape, for example, into a substantially flat surface. That is, the upper central tool U32 descends so that its contact surface U32a presses down the lower central tool L32, thereby forming 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 into a substantially flat center panel portion (central plate portion) 31 (state a18 in FIG. 7).

[0061] The can lid 3 reformed in this way is removed from the can lid shape forming device M2 to obtain the can lid 3 shown in state a19 in Fig. 7. The reformed can lid 3 in state a19 has a shape in which the annular protruding portion 32, consisting of a panel wall portion (inner peripheral wall portion) 321, a chuck wall radius portion (curved convex portion) 322, and a first chuck wall portion (first outer peripheral wall portion) 323, protrudes approximately perpendicularly to the extension direction of the center panel portion 31, which has been shaped into a substantially flat surface.

[0062] Here, the shape forming process S16 of the can lid in FIG. 7 has been described as simultaneously including a process of forming the chuck wall portion and a process of forming the center panel portion (central plate portion) 45 into an approximately flat surface, but these processes may be included in any order as separate steps.

[0063] Here, the annular protrusion forming (thickness increasing forming) step S15 and the can lid shape forming step S16 will be further described. In Fig. 9, which is drawn without the upper tool, state b1 shows the shape of a part of the preform 41a formed in the outer peripheral curved portion forming step S14. In this state b1, the center panel portion 45 is located above the uppermost position H, which is the highest vertical height of the outer panel portion 421.

[0064] In this annular protrusion forming (thickness increasing forming) process S15, as shown in Fig. 10A, the outer panel portion 421 of the preform 41a is sandwiched between an upper outer tool U21 and a lower outer tool L21 to generate a restraint portion K1 and fix the outer panel portion 421. In this state, an upward supporting force, as shown by an arrow Y101, is applied to the outer peripheral curved portion 47 by the contact surface (support surface) L23a of the curved portion support tool L23. At this point, the preform 41a having this outer peripheral curved portion 47 has the shape shown in Fig. 11A.

[0065] In this state, the upper central tool U22 and the side wall guide tool U23 are lowered. At this time, as shown by an arrow Y91 in state b2 of Fig. 9, the outer circumferential curved portion 47 of the preform 41a is supported by a supporting force from below, and a pressing force is applied to the center panel portion 45 of the preform 41a from above, as shown by an arrow Y92. This pressing force from above and below generates a compressive stress in the outer circumferential curved portion 47.

[0066] Then, in this annular protrusion forming (thickness increasing forming) process S15, the upper central tool U22 and the side wall guide tool U23 are further lowered. By such continuous lowering, as shown in state b2 and state b3 in Fig. 9, the downward pressing force (by the upper central tool U22) indicated by the arrow Y92 becomes greater than the upward supporting force (by the curved portion support tool L23) indicated by the arrow Y91. As a result, the curved portion support tool L23 is pressed down.

[0067] At this time, a downward pressing force indicated by an arrow Y102 is further applied to the center panel portion 45 of the preform 41a by the upper central tool U22, so that the center panel portion 45 is further pressed downward as shown in Fig. 10B. This causes the outer peripheral curved portion 47 shown in Fig. 10A to deform.

[0068] Then, as shown in Fig. 10B, a compressive stress is applied to the side wall 46 (Fig. 10A) in the protruding direction of the central protrusion 44 by the downward pressing force indicated by the arrow Y103 by the upper central tool U22 and the upward supporting force indicated by the arrow Y104 by the curvature portion support tool L23. As a result, as shown in Fig. 10B, at least a portion (Fig. 10A) that constituted the side wall 46 on the contact surface L23a of the curvature portion support tool L23 moves outwardly of the central protrusion 44 as indicated by the arrow Y105, while generating a compressed portion K2 due to this compressive stress.

[0069] At this point, the formed body 30a-1 shown in Fig. 11B is formed. This formed body 30a-1 has an annular protruding portion 32a consisting of a panel wall portion (inner peripheral wall portion) 321a, a chuck wall radius portion (curved convex portion) 322a, and a first chuck wall portion (first outer peripheral wall portion) 323a, and the plate thickness is increased over a wide range including the chuck wall radius portion 322a.

[0070] In this manner, the intermediate formed body 30 for the can lid is formed (before the shape of the can lid is formed) as shown in state b3 in Fig. 9. As shown in state b3, in the intermediate formed body 30 for the can lid, the uppermost position of the center panel portion 45 is located below the uppermost position H of the outer panel portion 421.

[0071] Then, in the can lid shape forming process S16, as shown in state b4 in Fig. 9, a downward pressing force indicated by arrows Y93 and Y94 is applied to the intermediate formed body 30 of the can lid to perform reforming. As a result, as shown in state b4, a can lid 3 is obtained that has a formed annular protrusion 32, a chuck wall portion, and a center panel portion (central plate portion) 31 consisting of a substantially flat surface. In the can lid 3, the formed annular protrusion 32 has an increased plate thickness within a required range including the chuck wall radius portion 322.

[0072] Instead of the example described here, the can lid 3 may be formed using the same device (upper and lower dies) from the blank punching step S11 to the annular protruding portion forming (thickness increasing) step S15. Alternatively, the can lid 3 may be formed using a device (upper and lower dies) different from the device (the device having the upper tool U2 and the lower tool L2) used in the annular protruding portion forming (thickness increasing) step S15 from the blank punching step S11 to the outer circumferential curved portion forming step S14. In this case, the preform 41a is prepared in advance by this different device, and the preform 41a is placed between the upper tool U2 and the lower tool L2.

[0073] [Example of the first embodiment] Next, an example of the first embodiment will be described. In this example, as shown in Fig. 12, a preform (not shown) previously molded was used to mold an intermediate molded body 30A for a can lid using a molding device M3. The preform was molded from a plate material made of an aluminum alloy (A5182P-H19, material plate thickness 0.235 mm) with a coating formed on both sides.

[0074] The forming device M3 in Fig. 12 has the same configuration as the forming device M1 described above. That is, in the forming device M3, the upper tool U2A corresponds to the upper tool U2 described above, and the lower tool L2A corresponds to the lower tool L2 described above. Thus, the upper outer tool U21A, the upper central tool U22A, and the side wall guide tool U23A correspond to the upper outer tool U21, the upper central tool U22, and the side wall guide tool U23 described above. In addition, the lower outer tool L21A, the lower central tool L22A, and the curved portion support tool (support member) L23A correspond to the lower outer tool L21, the lower central tool L22, and the curved portion support tool (support member) L23 described above.

[0075] Using this forming device M3, the same process as in the above-mentioned annular protrusion forming (plate thickness increasing forming) process S15 was performed. That is, as shown in Fig. 12, a downward pressing force (8.0 kN) indicated by an arrow Y202 was applied by the upper outer tool U21A to the lower outer tool L21A, and the outer panel portion 421A sandwiched between the lower outer tool L21A and the upper outer tool U21A was fixed.

[0076] In this state, the portion that will become the annular protrusion 32A together with the center panel portion 45A was supported by the lower center tool L22A and the curved portion support tool (support member) L23A with the upward supporting forces indicated by the arrows Y203 and Y204, while the lower center tool L22A and the side wall guide tool U23A were continuously lowered to continuously apply a downward pressing force indicated by the arrow Y201 (plate thickness increasing forming). By such plate thickness increasing forming, the center panel portion 45A and the annular protrusion 32A were formed.

[0077] In this manner, a can lid intermediate formed body 30A (before the can lid is shaped) was obtained, which was provided with a center panel portion 45A and an annular protruding portion 32A having a chuck wall radius portion (curved convex portion) 322A on its outer periphery.

[0078] In FIG. 12, LH (Lip Height) is the vertical length [mm] from the uppermost position to the outer tip of the outer panel portion 421A.

[0079] In this example, the plate thickness was increased by varying the upward support force [kN] indicated by the arrow Y204 by the curved portion support tool (support member) L23A. The measured values ​​of the lip height (LH in FIG. 12) [mm] for each value of the support force [kN] are shown in FIG.

[0080] In Fig. 13, the black circle plots indicate the value of lip height (Lip Height) [mm]. As shown in Fig. 13, even if the bearing capacity [kN] is increased, the value of lip height (Lip Height) [mm] does not change significantly. This result means that the plate thickness increase molding does not affect the shape of the outer panel portion 421A.

[0081] A part of a can lid formed in this embodiment is shown in Fig. 14A. Fig. 14B shows an enlarged view of annular protrusion 32A in Fig. 14A, and shows panel wall portion (inner peripheral wall portion) 321A, chuck wall radius portion (curved convex portion) 322A, and first chuck wall portion (first outer peripheral wall portion) 323A that constitute annular protrusion 32A. Also, in Fig. 14B, measurement points of the plate thickness [mm] of annular protrusion 32A are indicated by A to F.

[0082] In this example, the plate thickness [mm] of measurement points A to F (FIG. 14B) on the annular protruding portion 32A of the can lid formed as shown in FIG 14 was measured for each value of the upward supporting force [kN] indicated by the arrow Y204 (FIG. 12) by the curved portion supporting tool (supporting member) L23A during plate thickness increasing forming. The measurement results are shown in FIG 15.

[0083] According to this embodiment, as shown in FIG. 15, by increasing the support force [kN], the plate thickness [mm] could be increased from the original plate thickness of 0.235 mm in a wide range of measurement points A to F in the annular protrusion 32A. In this embodiment, the plate thickness was particularly increased compared to the original plate thickness in a wide range of measurement points A to F, especially when the support force was the largest, 8.9 kN. Also, as shown in FIG. 15, the plate thickness could be sufficiently increased at measurement points B to E within the range of the chuck wall radius portion (curved convex portion) 322A. Thus, in this embodiment, the plate thickness could be increased in a required range including not only the plate thickness on the inner periphery side of the annular protrusion but also the plate thickness on the outer periphery side of the annular protrusion by one-step plate thickness increase forming.

[0084] [Second embodiment] The method for forming a sheet material in the second embodiment is for forming a can bottom 6 shown in state a27 in Fig. 16 as a formed material. This method for forming a can bottom 6 includes the method for forming a sheet material 11 in the above-mentioned outline form as part of the entire process.

[0085] This method of forming the can bottom 6 includes the same steps as those shown in Fig. 5 above, that is, the blank punching step S11, the outer periphery drawing step S12, the central protrusion forming step S13, the outer periphery curved portion forming step S14, the annular protrusion forming (plate thickness increasing forming) step S15, and the can bottom shape forming step S16, all of which are shown in Fig. 5. In these forming steps (S11 to S16), the shape of the plate material 51 is changed as shown in states a21 to a26 in Fig. 16, and then reforming is performed to form the can bottom 6 in state a27.

[0086] In the blank punching process S11 in the process of forming the can bottom 6, for example, upper and lower punching tools (not shown) are used to punch the plate material 51 to be processed into an approximately disk shape, and the plate material 51 is formed into an approximately disk shape (state a21 in Figure 16).

[0087] In the outer periphery drawing process S12 in the process of forming the can bottom 6, for example, by using upper and lower outer periphery drawing tools (not shown) for drawing the outer periphery of the substantially disk-shaped plate material 51, the outer periphery is drawn while fixing a plate-like portion inside the outer periphery of the substantially disk-shaped plate material 51 shown in state a21 in Fig. 16. As a result, an outer periphery (side surface) 53 extending in a direction substantially perpendicular (upward) to the plate-like portion 52 is formed on the outer periphery side of the plate-like portion 52 of the plate material 51 as shown in state a22 in Fig. 16.

[0088] In the central protrusion forming step S13 in the process of forming the can bottom 6, for example, for a plate material 51 in the state a22 of Fig. 16, an upper and lower central drawing tool (not shown) is used to draw the substantially central portion of the plate-shaped portion 52, and the outer panel portion (outer plate portion) 521 of the plate-shaped portion 52 is fixed while being formed into an annular curved portion 522 that protrudes gently in the substantially vertical direction (downward), and in this state, a drawing process is performed on the inner peripheral side. As a result, as shown in the state a23 of Fig. 16, a central protrusion 54 consisting of a dome panel portion (central plate portion) 55 and a side wall portion 56 on the outer peripheral side is formed. The dome panel portion (central plate portion) 55 has a dome shape that protrudes gently in the protruding direction of the central protrusion 54.

[0089] In the outer peripheral curved portion forming step S14 and the annular protruding portion forming (plate thickness increasing forming) step S15, for example, the plate material 51 with the central protruding portion 54 formed therein (state a23 in FIG. 16) is formed using a forming device having an upper tool U4 and a lower tool L4. As shown in state a24 in FIG. 16, for example, the upper tool U4 includes an annular upper outer tool U41, an upper central tool U42, and an annular side wall guide tool U43 located therebetween. The lower tool L4 includes an annular lower outer tool L41 and an annular curved portion support tool (support member) L42 located on the inner periphery side of the annular lower outer tool L41.

[0090] In the outer peripheral curved portion forming step S14, for example, as shown in state a24 in Fig. 16, the plate material 51 with the central protrusion 54 formed therein is placed on the lower tool L4, and then the upper outer tool U41 is lowered. As a result, the annular curved portion 522 of the plate material 51 is sandwiched and fixed between the abutment surface U41a of the upper outer tool U41 and the abutment surface L41a of the lower outer tool L41. Note that the fixing of the annular curved portion 522 is continued thereafter until the annular protrusion forming (plate thickness increasing forming) step S15 is completed.

[0091] At the same time, in the outer periphery curved portion forming process S14, the upper central tool U42 and the side wall guide tool U43 are lowered. At this time, as shown in state a24 in FIG. 16, the upper central tool U42 is lowered so that its contact surface U42a contacts the dome panel portion 55.

[0092] The upper central tool U42 descends so that the height position of its contact surface U42a approaches the height position of the contact surface (support surface) L42a of the curved portion support tool (support member) L42. That is, the curved portion support tool (support member) L42 is relatively movable in the protruding direction (upward direction) of the central protruding portion 54. When the plate material 51 is positioned on the contact surface L42a, the curved portion support tool L42 applies a support force to the plate material 51 in the protruding direction. Therefore, by the descent of the upper central tool U42 and the side wall guide tool U43, the outer periphery of the side wall portion 56 is supported by the curved portion support tool L42 that applies the support force, and a curved outer periphery curved portion 57 is formed in a curved shape that follows the shape of the contact surface L42a. In this way, a preform 51a having a peripheral curved portion 57 is formed from the plate material 51 (state a25 in FIG. 16).

[0093] In the annular protrusion molding (plate thickness increasing molding) process S15 (state a25, state a26 in FIG. 16), for example, while the outer peripheral curved portion 57 of the molded preform 51a is supported by the abutment surface (support surface) L42a of the curved portion support tool (support member) L42, a pressing force is applied to the central protrusion 54 consisting of the dome panel portion 55 and the side wall portion 56 in the direction opposite to the protruding direction.

[0094] At this time, the upper central tool U42 continuously descends so as to press down the dome panel portion 55 with its abutment surface U42a, thereby applying a pressing force to the dome panel portion 55, and by lowering this dome panel portion 55, a pressing force is applied to the outer peripheral curved portion 57 located between the tip abutment portion U43a and the abutment surface L42a.

[0095] Such pressing (thickness increasing forming) caused by the continuous descent of the upper central tool U42 and the side wall guide tool U43 presses the dome panel portion 55 downward and deforms the outer circumferential curved portion 57. This thickness increasing forming also causes a compressive stress in the protruding direction of the central protrusion 54 in the side wall portion 56, and moves at least a portion that constituted the side wall portion 56 on the contact surface L42a of the curved portion support tool L42 outwardly of the central protrusion 54.

[0096] By this annular protrusion forming (thickness increasing forming) process S15, an intermediate can bottom 60 (state a26 in FIG. 16) is formed (before the can bottom is shaped) having an annular protrusion 62a whose thickness is selectively increased based on the moved portion. The annular protrusion 62a has an increased thickness over a wide range including a so-called bottom radius portion 622a. Thereafter, the formed intermediate can bottom 60 (before the can bottom is shaped) is removed from the upper tool U4 and the lower tool L4.

[0097] In this way, also in the molding method of the plate material 51 of the second embodiment, the relative pressing (pressing) of the dome panel portion 55 is performed continuously (in one stroke) using the same device (upper and lower dies) having the upper tool U4 and the lower tool L4. That is, also in the molding method of the second embodiment, pressing is not performed in multiple stages using dies of different shapes each time, but the annular protrusion 62a with the plate thickness increased to the required range can be formed in this simple manufacturing process.

[0098] The can bottom shape forming step S16 is a step of reforming the shape of the intermediate can bottom formed body 60 as necessary to form it into the shape of the can bottom, and includes a step of forming the shape of the can bottom annular protrusion 62. After reforming in this can bottom shape forming step S16, the can bottom 6 is removed from the reforming device (not shown) to obtain the can bottom 6 (state a27 in FIG. 16).

[0099] The can bottom shape forming step S16 can be carried out by a conventionally known method, for example, a method using a rotating roll or a method using press forming.

[0100] In the second embodiment, when an inner surface painting step is particularly required, it is desirable to carry out the step prior to the can lid shape forming step S16.

[0101] The can bottom 6 in state a27 has a dome panel portion (central plate portion) 61, a dome panel wall portion (inner peripheral wall portion) 621, a bottom radius portion (curved convex portion) 622, a chime lower portion (first outer peripheral wall portion) 623, and a chime portion (second outer peripheral wall portion) 63. Here, the dome panel wall portion 621, the bottom radius portion 622, and the chime lower portion 623 form a can bottom annular protrusion 62. The can bottom annular protrusion 62 has a shape that is slightly inwardly inclined due to reforming, and the plate thickness has been increased within the necessary range including the bottom radius portion 622.

[0102] Incidentally, the can bottom shape forming step S16 may further include a step of forming the dome panel portion (central plate portion) 55 into a desired shape, for example, a shape other than a spherical shape, such as a substantially spheroidal surface, a substantially conical surface, a substantially flat surface, etc. In this case, the can bottom shape forming step S16 may include a step of forming the shape of the can bottom annular protrusion portion 62 and a step of forming the dome panel portion (central plate portion) 55 into, for example, a substantially flat surface, simultaneously or in any order, as a step of reforming the shape of the can bottom intermediate formed body 60 in state a26 in Fig. 16 .

[0103] Although the embodiments of the present invention have been described in detail above with reference to the drawings, the specific configuration is not limited to these embodiments, and the present invention includes design changes and the like that do not deviate from the gist of the present invention. In addition, the above-mentioned examples can be combined by utilizing each other's technologies as long as there are no particular contradictions or problems in the purpose, configuration, etc. [Explanation of symbols]

[0104] 1: forming material, 3: can lid, 6: can bottom, 11, 41, 51: plate material, 11a, 41a, 51a: preform, 12, 23, 31, 45, 45A: center panel portion (central plate portion), 13, 32, 32a, 32A, 62a: annular protruding portion, 14, 25, 420, 421, 421A, 521: outer panel portion (outer plate portion), 22, 44, 54: central protruding portion, 24, 46, 56: side wall portion, 26, 47, 57: outer peripheral curved portion, 30, 30A: intermediate formed body of can lid (before the can lid is shaped), 30a-1: formed body, 33: second chuck wall portion (second outer peripheral wall portion), 34: curl portion, 42, 52: plate-shaped portion, 43, 53: outer peripheral portion (side surface), 60: (can Intermediate formed body of can bottom (before the bottom shape is formed), 121, 141, 311: curved portion, 131: inner peripheral wall portion, 132: curved convex portion, 133: outer peripheral wall portion, 321, 321a, 321A: panel wall portion (inner peripheral wall portion), 322, 322a, 322A: chuck wall radius portion (curved convex portion), 323, 323a, 323A: first chuck wall portion (first outer peripheral wall portion), 522: annular curved portion, 55, 61: dome panel portion (center plate portion), 62: can bottom annular protrusion portion, 63: chime portion (second outer peripheral wall portion), 621: dome panel wall portion (inner peripheral wall portion), 622, 622a: bottom radius portion (curved convex portion), 623: chime lower portion (first outer peripheral wall portion)

Claims

1. a step of forming a central protrusion portion, which is composed of a central plate portion and a side wall portion on an outer periphery of the central protrusion portion, on a plate-shaped portion of the plate material; forming a curved outer periphery portion on an outer periphery of the side wall portion; and forming an annular protruding portion having an increased thickness by deforming at least the outer circumferential curved portion, In the step of forming the annular protrusion, The outer circumferential curved portion is supported by a support member movable relative to the protruding direction of the central protruding portion, and a pressing force is applied to the central protruding portion in a direction opposite to the protruding direction, thereby generating a compressive stress in the protruding direction in the side wall portion, and at least a portion constituting the side wall portion is moved on the support surface of the support member, thereby forming the annular protruding portion having a selectively increased plate thickness. A molding method comprising the steps of:

2. The molding method according to claim 1, characterized in that in the step of forming the annular protrusion, at least a portion that constituted the side wall portion on the support surface of the support member is moved toward the outside of the central protrusion.

3. 3. The method according to claim 1, wherein the plate material is made of a material mainly composed of metal.

4. 2. A method for forming a can end, comprising the method according to claim 1 as a part of an entire process.

5. After the step of forming the annular protrusion, The process of forming the can lid shape is as follows:

5. The method for forming a can end according to claim 4, further comprising a step of forming a chuck wall portion.

6. 2. A method for forming a can bottom, comprising the method according to claim 1 as a part of an entire process.

7. After the step of forming the annular protrusion, The process of forming the bottom of the can is as follows:

7. The method for forming a can bottom according to claim 6, further comprising at least a step of forming a shape of the can bottom annular protrusion.

Images