Metal cup manufacturing method

Abstract

To manufacture a metallic cup which prevents wrinkle and cracks on an outer peripheral surface and has a smooth tapered body section.SOLUTION: A method of manufacturing a metallic cup by press-molding a metal plate includes a drawing-and-squeezing process of forming a bottomed cylindrical cylinder body by drawing and squeezing the metal plate, and a diameter-enlarging process of forming an intermediate cylinder body having a tapered cylinder section by gradually enlarging a diameter of a body section of the cylinder body from a bottom part side to an opening end part side by pressing a punch into the cylinder body from the opening end part side after the drawing-and-squeezing process.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal cup made of an aluminum alloy or the like. [Background technology]

[0002] Existing drinking cups are made of ceramic, glass, metal, paper, plastic, etc. Of these, metal, paper, and plastic cups are lighter than ceramic or glass cups and do not take up much space when stacked, making them easy to carry.

[0003] Patent Document 1 discloses a tapered metal cup (metal cup). This metal cup is made of aluminum and is described as being harder and more durable than a plastic cup, and also having excellent recyclability.

[0004] The method for manufacturing this metal cup is described as follows: a metal plate is punched and drawn to form a cup, and the cup is ironed to form a cylindrical vertical-wall preform (DI process); the open end is cut off to set a predetermined height, and then the open end is rounded to form a curled portion; a stepwise drawing process is then performed to form a vertically drawn cup having vertical wall sections of different heights and with a continuously decreasing diameter from the curled portion to the bottom; a die having a tapered profile is then used to expand each of the vertical wall sections to form a tapered cup with each vertical wall section forming a tapered side wall; and finally, a dome portion is formed at the bottom of the cup. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Japanese Patent Publication No. 2020-508874 Summary of the Invention [Problem to be solved by the invention]

[0006] When manufacturing a metal cup that is taller than its diameter by drawing a metal plate, if the body is tapered, wrinkles and cracks are likely to occur on the outer periphery. In Patent Document 1, the body is formed with multiple sections to form a tapered sidewall in stages, but it is desirable to form a body that is smoothly tapered from the bottom to the open end of the cup.

[0007] The present invention has been made in consideration of the above circumstances, and aims to provide a method for manufacturing a metal cup that is less likely to develop wrinkles or cracks on the outer surface and has a smooth, tapered body. [Means for solving the problem]

[0008] The present invention is a method for manufacturing a metallic cup by press-forming a metal plate, and includes a drawing and ironing process in which the metal plate is drawn and ironed to form a cylindrical body with a bottom, and an expanding process in which, after the drawing and ironing process, a punch is forced into the body from the open end side of the body to gradually expand the diameter of the body from the bottom side toward the open end side, thereby forming an intermediate cylinder having a tapered cylindrical portion.

[0009] In the manufacturing method described in Patent Document 1, after forming a cylindrical body with a bottom, the body is drawn so that the diameter gradually decreases from the open end toward the bottom, whereas in the present invention, the body is formed so that the diameter gradually increases from the bottom toward the open end. In other words, while the process described in Patent Document 1 compresses the metal material radially inward from the outer periphery, in the present invention, the metal material is expanded radially outward from the inner periphery, which makes it possible to form a smoothly tapered body portion with fewer wrinkles.

[0010] The drawing and ironing process to form the cylindrical body with a bottom can be done using the same technology as that used for existing beverage cans. In this case, existing manufacturing equipment produces a cylindrical body with a diameter of approximately 66 mm, which is easy to hold in the hand.

[0011] When the cylindrical body obtained by the drawing and ironing process using this existing equipment is formed into a metal cup using the method described in Patent Document 1, the final cup shape is small in diameter because it is a process of drawing from a cylindrical body, and a long and narrow cup is required to achieve the same volume as the existing cylindrical body. In particular, because the diameter is smallest at the bottom, there is a risk that the cup may tip over when placed on a table or the like. On the other hand, if an attempt is made to produce a cup with a larger diameter, the drawing and ironing equipment would need to be extensively modified to one capable of forming a large-diameter cylindrical body.

[0012] In the manufacturing method of the present invention, the cylinder is expanded, so the capacity can be adjusted by the height. Therefore, the same drawing and ironing process as the existing beverage can manufacturing process can be applied, and existing beverage can manufacturing equipment can be used as is, which is economical.

[0013] In the method for manufacturing a metal cup of the present invention, the expanding process may include a step forming process in which one or more punches are used to form a step in the body of the cylindrical body whose diameter on the opening end side is larger than the diameter on the bottom side of the cylindrical body, and a shaping process in which one or more punches are used to expand the step and shape it into the tapered cylindrical body.

[0014] When forming a tapered tube portion on the body of a cylindrical tube with a bottom, if the taper angle is large, cracks are likely to occur if the tube is machined using a tapered punch from the beginning. For this reason, in the present invention, a step portion is first formed in the step formation process, where the diameter of the open end is larger than the diameter of the bottom, and the step portion is then expanded to form the tapered tube portion. This makes it less likely to crack, and as a result, a smooth tapered surface can be formed.

[0015] In this case, the step forming step and the shaping step can be performed alternately a plurality of times.

[0016] Alternatively, after forming a plurality of step portions in the step forming step, the shaping step can be carried out on these step portions individually or in groups of a plurality of step portions.

[0017] In the method for manufacturing a metal cup of the present invention, the punch used in the step forming process is equipped with a stepped punch that has a guide portion having a cylindrical outer surface connected to a forming portion having a larger diameter than the guide portion, and the guide portion of the stepped punch may be inserted into the cylindrical body first, thereby fitting the guide portion into the cylindrical body while the forming portion expands the diameter of the cylindrical body.

[0018] Since the guide portion of the stepped punch is inserted into the cylindrical body first, the cylindrical body and the stepped punch are aligned, and the subsequent diameter expansion process by the forming portion can be performed with high precision, allowing a cup with high roundness to be manufactured.

[0019] In this case, a lower step is further formed near the bottom of the body of the metal cup, and the punch used in the step forming process further includes a lower step punch having a molding portion with a cylindrical outer surface, and after forming an initial step near the bottom of the body using the stepped punch, the lower step punch is fitted into the initial step and the lower part of the initial step is machined while expanding in diameter, thereby forming the lower step.

[0020] Because the lower step is formed at the bottommost part of the cylindrical body, if a stepped punch with a guide part is used to form it, there is a risk that the guide part will abut against the inner bottom surface of the cylindrical body. Therefore, an initial step is first formed using a stepped punch at a position above the position where the lower step is to be formed, and then a lower step punch is used to press the initial step position downward. Because the lower step punch can be designed without a guide part, the bottom will not be deformed even if it is brought close to the bottom to form the lower step.

[0021] In the method for manufacturing a metal cup of the present invention, it is preferable to have a curling step of folding back the open end of the intermediate cylinder to form a curled portion after the diameter expanding step. The curled portion at the open end improves mouthfeel when the cup is placed on the lips.

[0022] In this case, the step forming step may be performed in the diameter expanding step to form a straight upper cylindrical portion along the can axial direction at the open end of the intermediate cylindrical body. In the curling step, a forming tool is pressed against the open end of the intermediate cylindrical body in the can axial direction, and the straight upper cylindrical portion can bear the load, allowing the curled portion to be formed with high precision.

[0023] In other words, if the shape gradually expands from the bottom to the opening end, deformation during the curl forming process will be significant and it will be difficult to form accurately. Therefore, by forming a cylindrical portion at the opening end and increasing its deformation strength, it is possible to form the curl more accurately without deforming the curl portion during the curl forming process.

[0024] The upper cylindrical portion is preferably formed by an upper step punch, because this is the final processing step in the diameter expansion process, and if a stepped punch is used, the tapered portion formed in the previous step may be deformed by the guide portion. [Effects of the Invention]

[0025] According to the present invention, it is possible to manufacture a metal cup that is less likely to develop wrinkles or cracks on its outer circumferential surface and has a body portion with a smooth tapered surface. [Brief explanation of the drawings]

[0026] [Figure 1] FIG. 1 is a front view of a metal cup manufactured by a manufacturing method according to an embodiment of the present invention, with half of the metal cup taken along a vertical cross section centered on the can shaft. [Figure 2] FIG. 2 is a front view of a cylindrical body obtained in the drawing and ironing process, with half of the body being a vertical cross-sectional view centered on the can shaft. [Figure 3] FIG. 10 is a vertical cross-sectional view of a main part showing a state where processing is being performed in a lower step forming step. [Figure 4] FIG. 10 is a longitudinal cross-sectional view of a main part showing a state where processing is being performed in a step forming step. [Figure 5] 5 is a longitudinal cross-sectional view of a main part showing a state in which processing is being performed in a shaping step following the step forming step of FIG. 4. FIG. [Figure 6] 6 is a longitudinal sectional view of a main part showing a state in which processing is being performed in a step forming step following the shaping step of FIG. 5. [Figure 7] FIG. 10 is a cross-sectional view showing a state in which processing is performed with a curling tool in a curling step. DETAILED DESCRIPTION OF THE INVENTION

[0027] DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a method for manufacturing a metal cup according to the present invention will be described below with reference to the drawings.

[0028] As shown in Fig. 1, the metal cup 1 manufactured by the manufacturing method of this embodiment is formed by press-forming a metal plate made of aluminum or an aluminum alloy into a cylindrical shape with a bottom, and has a tapered body 4 in which the diameter of the open end 3 is larger than the diameter of the bottom 2, and the diameter gradually increases from the bottom 2 toward the open end 3 as a whole. A curled portion 5 is formed at the open end 3 by rolling the end, including the edge portion, radially outward. The radial center of this metal cup 1 is defined as a can axis C.

[0029] The bottom 2 has a shape that is made up of a concavely curved dome portion 6, an inner tapered wall portion 7 that is continuous with the outer periphery of the dome portion 6 and that gradually increases in diameter downward in the axial direction of the can, a rim portion 8 that is continuous with the outer periphery of the inner tapered wall portion 7 and that comes into contact with the table or the like when the metal cup 1 is placed on the table, and a tapered rising portion 9 that is continuous from the outer periphery of the rim portion 8 to the lowest end of the body portion 4.

[0030] The dome portion 6 is concave at its greatest distance from the tip of the rim portion 8 at a position on the can axis C. The rim portion 8 is formed in a ring shape around the can axis C, and is formed with a curved surface that convexly curves downward from the can axis C, and contacts the ground at its most protruding position. The outermost peripheral end of the rim portion 8 has a smaller diameter than the smallest diameter at the bottom end of the body portion 4, and this outermost peripheral end of the rim portion 8 and the bottom end of the body portion 4 are connected by a rising portion 9.

[0031] The body 4 has a straight lower cylindrical portion 11 and an upper cylindrical portion 12 formed near the bottom 2 and the open end 3, respectively, that run along the can axis C. A small lower step 13 is formed at the upper end of the lower cylindrical portion 11 that continues from the bottom 2, and a small upper step 14 is also formed at the lower end of the upper cylindrical portion 12 that continues to the curled portion 5. A tapered tubular portion 15 is formed between the upper end of the lower step 13 and the lower end of the upper step 14, with the diameter gradually increasing from bottom to top.

[0032] These dimensions are not necessarily limited, but are set, for example, as follows: Diameter of curled part (outer diameter) D1: 75mm or more and 100mm or less Diameter of the ground contact area D2: 45mm to 60mm Overall height H1: 80mm to 180mm Depth H2 of dome part 6: 1 mm or more and 15 mm or less Diameter D3 of the lower cylindrical part 11: 50 mm or more and 70 mm or less Diameter D4 of upper cylindrical part 12: 70 mm or more and 95 mm or less Height H3 from the bottom surface to the bottom end of the lower step 13: 8 mm or more and 25 mm or less Length H4 from the top end of the curled portion 5 to the top end of the upper step portion 14: 8 mm or more and 20 mm or less Angle θ of the tapered cylindrical portion 15 relative to the horizontal plane: 80° or more and 85° or less

[0033] Next, a method for manufacturing this metallic cup 1 will be described. The metallic cup 1 is manufactured through a process including a cylinder-forming process in which a metal plate is drawn and ironed to form a cylindrical cylinder 21 with a bottom, a diameter-expanding process in which, after the cylinder-forming process, a plurality of punches 40 to 43 with different outer diameters are used to press the punches 40 to 43 into the cylinder 21 from the open end 22 side, starting from the smallest outer diameter, thereby gradually expanding the diameter of the body 23 of the cylinder 21 from the bottom 2 side toward the open end 22 side to form a tapered cylinder portion 15 and form an intermediate cylinder 50, and a curling process in which a curled portion 5 is formed at the open end of the intermediate cylinder 50 formed in the diameter-expanding process. The steps will be described below in order.

[0034] [Cylinder formation process] The cylinder forming process includes a cup forming process (FIG. 2(a)) in which a plate made of aluminum or an aluminum alloy is punched and drawn to form a cup 25 that is shallower and has a larger diameter than the cylinder 21 to be formed in the next process, and a drawing and ironing process (FIG. 2(b)) in which the cup 25 is drawn and ironed to form a cylindrical cylinder 21 with a smaller diameter than the cup 25 and a predetermined height as shown in the figure, which has a bottom.

[0035] In this drawing and ironing process, the bottom 2 of the cylindrical body 21 is finished into the final shape of the bottom 2 of the metal cup 1, and has a dome portion 6, an inner tapered wall portion 7, a rim portion 8, and a tapered rising portion 9.

[0036] [Diameter expansion process] The diameter expansion process consists of multiple steps, and by sequentially repeating a step formation process in which a step is formed in the body 23 of the cylindrical body 21, the diameter of which is larger on the opening end 22 side than on the bottom 2 side, and a shaping process in which the step is expanded and shaped into a tapered surface, the intermediate cylindrical body 50 shown in Figure 2(c) is formed.

[0037] In this case, after a lower step forming step of forming lower step 13 at the bottom of cylindrical body 21, a first step forming step of forming a first step slightly above lower step 13, a first shaping step of shaping the first step, a second step forming step of forming a second step near the top end of the shaping surface, a second shaping step of shaping the second step, etc., after forming the first lower step, the step forming step and the shaping step are alternately performed to form one step and then shape the step into a tapered shape as a whole. For example, the step forming step and the shaping step are each performed alternately 10 to 30 times.

[0038] Finally, at the top of the cylindrical body 21, an upper step forming step is carried out to form the upper step 14, thereby completing the diameter expansion step.

[0039] The details will be explained below. In this diameter expansion process, the shape of the cylindrical body 21 gradually changes, but the cylindrical body formed at the end of the diameter expansion process is referred to as an intermediate cylindrical body 50, and the cylindrical bodies formed in the steps up to that point will be described by using the same reference numeral 21 as the cylindrical body used in the cylindrical body formation process.

[0040] (Step formation process) As shown in Figures 3 to 6, the step forming process uses multiple stepped punches 40 to 42 of different diameters, two punches 43 for the lower step, and a punch for the upper step (the figures only show three stepped punches 40 to 42 of different diameters and one punch 43 for the lower step. Although the punch for the upper step has a different diameter, its outer shape is the same as that of the punch for the lower step, so the explanation will be given with reference to the punch 43 for the lower step as necessary).

[0041] 4 and 6 (also shown by two-dot chain lines in FIGS. 3 and 5), the stepped punches 40 to 42 are formed in a stepped shape in which a guide portion 44 and a forming portion 45 having a larger diameter than the guide portion 44 are connected, and the guide portion 44 is disposed on the tip side. The guide portion 44 is inserted into the cylindrical body 21 first, but the cylindrical body 21 is not formed by this guide portion 44, but is used for centering with the cylindrical body 21.

[0042] The outer peripheral surface of the guide portion 44 of these stepped punches 40 to 42 is formed with a rounded chamfered surface 46 at the tip end, and is formed into a substantially straight cylindrical outer surface 47 from the outer peripheral end of the rounded chamfered surface 46. The maximum diameter of the guide portion 44 of each stepped punch 40 to 42 is formed slightly smaller than the inner diameter of the opening of the cylindrical body 21 before the step is formed by that stepped punch 40 to 42.

[0043] Molded portion 45 is formed into a convex curved surface so as to protrude radially outward from cylindrical outer surface 47 of guide portion 44, and is formed so that its maximum diameter is larger than the diameter of cylindrical outer surface 47 of guide portion 44. Molded portion 45 forms steps 51 to 53 (in Figures 3 to 6, steps at different molded positions are indicated by the reference numerals 51 to 53) that have a larger diameter on the open end 22 side than on the bottom 2 side of cylindrical body 21.

[0044] As shown in Fig. 3, the lower step punch 43 does not have a guide portion 44 like the stepped punches 40 to 42, and is a punch in which the surface of the forming portion 48 extends to the tip, and the corners around the tip are chamfered into a convex arc shape. In Fig. 3, the lower step punch 43 is formed in a shape without a step. The upper step punch also has a different diameter, but like the lower step punch 43, it does not have a guide portion 44 like the stepped punches 40 to 42, and has a shape in which the surface of the forming portion (see symbol 48) extends to the tip.

[0045] The punch 43 for the lower step is formed to have a diameter equal to or slightly smaller than the forming portion 45 of the stepped punch 40, which has the smallest diameter among the stepped punches 40 to 42, and the punch for the upper step is formed to have a diameter equal to or slightly smaller than the maximum diameter of the shaping surface 65 of the shaping punch 61, which has the largest diameter among the shaping punches 61 used in the shaping process (the punch for the upper step is not shown in the illustration, but its shape is shown as a representative of the punch 43 for the lower step, so please refer to this).

[0046] Since the punch 43 for the lower step and the punch 44 for the upper step do not have a guide portion 44, the convex curved surface 48a of the forming portion 48 is formed to extend toward the tip, and its minimum diameter is formed to be smaller than the inner diameter of the cylinder before being formed by the punch 43 for the lower step and the punch 43 for the upper step.

[0047] (shaping process) In the shaping step, the steps 52, 53 formed in the step forming step are shaped into a smooth tapered surface. As shown in Fig. 5, the shaping punch 61 used in this shaping step has a rounded chamfered surface 62 at its front end, and a tapered surface 63 that gradually widens from the front end toward the rear continues from the rounded chamfered surface 62 to the rear, with a convex curved surface 64 with a large radius of curvature formed on the rear end surface of the tapered surface 63. The region from the middle of the tapered surface 63 to the front half of the convex curved surface 64 forms a shaping surface 65.

[0048] In this case, the shaping surface 65 is formed long in the tip direction, as shown by the symbol 65a, so that shaping can be performed from a position sufficiently farther in the tip direction than the step 52 formed in the step forming process, while the rear end 65b of the shaping surface 65 is formed long enough to shaping up to a position slightly behind the step 52, 53 formed in the step forming process.

[0049] Therefore, this shaping surface 65 is not a straight tapered surface, but a tapered surface having a convex curved surface 64 that curves so as to bulge slightly radially outward. By using such a shape, it is possible to suppress elastic recovery (springback) when a wide region including the front and rear of the step portions 52, 53 is expanded radially outward, and it is possible to reliably form the body portion 23 of the tubular body 21 into a tapered surface. Therefore, in this shaping step, it is possible to shape the wide region before and after the step portions 52, 53 formed in the step forming step into a smooth tapered shape.

[0050] In these step forming process and shaping process, first, the lower step 13 located at the lowest part of the body 4 is formed (FIG. 3, lower step forming process). This lower step 13 is formed using the stepped punch 40 with the smallest diameter and a lower step punch 43, and first a step 51 (the step at this time is referred to as an initial step) is formed near the bottom 2 using the stepped punch 40.

[0051] In this case, machining is performed at a position close to the bottom surface of the cylindrical body 21, and since machining to a position close to the bottom 2 with the stepped punch 40 would cause the guide portion 44 to collide with the previously machined bottom 2 and deform it, the stepped punch 40 is used to machine to a position that does not reach the bottom 2. The state machined with this stepped punch 40 is shown by the two-dot chain line in Figure 3.

[0052] Next, a lower step punch 43 is fitted into the cylindrical body 21, and the portion below the initial step 51 formed by the stepped punch 40 is machined while expanding its diameter so as to press downward the position of the initial step 51, thereby forming the lower step 13. This lower step punch 43 is formed to have an outer diameter that is the same as or slightly smaller than the forming portion 45 of the stepped punch 40, so it is fitted into the body portion 23 of the cylindrical body 21 whose diameter has been expanded by the step 52, and is aligned with the body portion 23. In addition, because this lower step punch 43 does not have a guide portion 44, it can be brought closer to the bottom 2 than the stepped punch 40.

[0053] In addition, the position below the lower step 13 formed by this lower step punch 43 is the part where the outer surface of the cylindrical body 21 is held by the chuck portion 70 during the expanding process, including the lower step forming process, and the lower cylindrical portion 11 is left straight without being formed into a tapered shape.

[0054] Next, a stepped punch 41 having the second smallest diameter (which will be explained with reference to FIG. 4 for convenience) is used to form a first step 52 at a position slightly above the lower step 13 (not shown in FIG. 4). At this time, the guide portion 44 of the stepped punch 41 is inserted into the large diameter portion of the lower step 13, and the punch 41 is aligned with the cylindrical body 21.

[0055] After forming this first step 52, the front and rear of the first step 52 are shaped into a smooth tapered shape by a shaping punch 61 (FIG. 5). In this case, as described above, the shaping surface 65 of the shaping punch 61 is not a straight tapered surface but is formed into a curved surface that bulges slightly radially outward, so that the step 52 formed in the previous process can be sufficiently expanded from the radially inward direction, effectively erasing any traces of it, and forming a smooth tapered shape.

[0056] Then, after repeating this step forming process and shaping process a required number of times, finally, an upper step punch (not shown) is used to form the upper step 14 at a position slightly below the open end 22 of the cylindrical body 21 (upper step forming process). Like the lower step punch 43, this upper step punch is a punch that does not have a guide portion and only has a forming portion 48.

[0057] This upper step-forming punch is formed with a diameter that is the same as or slightly smaller than the shaping surface 65 of the largest diameter shaping punch 61, so it fits easily into and is centered on the open end 22 of the cylindrical body 21 formed up to that point. Then, the top of the tapered surface shaped by the shaping punch 61 is machined to form the upper step 14. Above the upper step 14 is a straight, cylindrical upper cylindrical portion 12' (see the two-dot chain line in Figure 7).

[0058] After forming this upper step 14, the upper cylindrical portion 12' is left straight, so no shaping process is carried out. However, if the upper step 14 is formed using stepped punches 41, 42, the tapered portion shaped in the previous shaping process will be deformed by the guide portion 44. Therefore, a punch without a guide portion 44 (punch for the upper step) is used to prevent deformation of the lower portion of the upper step 14.

[0059] Therefore, the tapered intermediate cylinder 51 formed by this series of diameter expansion processes has a straight lower cylindrical portion 11 near its bottom 2 that follows the can axis C, and an opening 22 is formed in the straight upper cylindrical portion 12'.

[0060] [Curling process] After the diameter expansion step, the end portion including the edge of the upper cylindrical portion 12' of the intermediate cylinder 50 is folded back radially outward and wound to form the curled portion 5. In this curling step, multiple curling tools 71 are used, as shown in FIG.

[0061] Each curling tool 71 is rotatable about an axis C1 that extends in a direction perpendicular to the can axis C, and has a forming groove 72 along its circumferential direction. Each curling tool 71 is pressed against the open end of the intermediate cylinder 50 in the direction of the can axis C while rotating around the upper cylindrical portion 12', whereby the forming groove 72 causes the end portion, including the edge of the upper cylindrical portion 12', to be folded back while expanding, thereby forming the curled portion 5.

[0062] In this curling process, the curling tool 71 presses the tapered intermediate cylinder 50 in the direction of the can axis C. However, the open end of the intermediate cylinder 50 is formed by a straight upper cylindrical portion 12' that is aligned with the can axis C. In addition, due to the work hardening effect resulting from the diameter expansion process, buckling and deformation are unlikely to occur.

[0063] The metal cup 1 manufactured in this manner has straight cylindrical portions 11, 12 of a certain length formed near the bottom 2 and the open end 3, and most of the body 4 therebetween is formed in a tapered shape that gradually increases in diameter from the bottom 2 toward the open end 3. In this manufacturing method, steps 52, 53 having a larger diameter on the open end 22 side than on the bottom 2 side of the cylindrical body 21 are formed, and then the steps 52, 53 are shaped into a tapered shape by expanding them, and this process is repeated to form the entire body 4 in a smooth tapered shape.

[0064] In this case, the metal material is pushed outward in the radial direction from the inner periphery, so wrinkles are less likely to occur. Also, because the steps 52 and 53 are formed first and then tapered, cracks are less likely to occur compared to when the material is tapered without forming the steps 52 and 53. This allows for the formation of a smoothly tapered body portion 4.

[0065] Furthermore, the bottom 2 of this metal cup 1 is the same as the bottom 2 formed in the bottomed cylindrical tubular body 21 formed in the initial stage, and the portion above this bottom 2 is expanded in diameter. Therefore, the process of forming the tubular body 21 (tubular body forming process) can be carried out using existing equipment for manufacturing beverage cans.

[0066] In addition, the opening 3 has a curled portion 5, which makes it smooth to the touch.

[0067] In the above embodiment, the step forming step and the shaping step are alternately repeated in the diameter expanding step, where one step is formed, this step is shaped into a tapered surface, and then a new step is formed above the first one and shaped into a tapered surface. However, the step forming step may be performed multiple times to form multiple steps along the can axis C, and then these steps may be shaped one by one from the bottom side. It is also possible to shape two or more steps at once.

[0068] In addition, the above embodiment can be modified as appropriate without departing from the spirit of the present invention. [Explanation of symbols]

[0069] C Can shaft 1 metal cup 2 bottom 3 Open end 4. Torso 5 Curl section 6 Dome section 7 Inner tapered wall 8 Rim 9 Rising section 11 Lower cylindrical part 12 Upper cylindrical part 13 Lower section 14 Upper step 15 Tapered cylindrical part 21 Cylinder 25 cups 41,42 Stepped punch 43 Punch for lower cross section 44 Guide section 45 Molding section 47 Cylindrical outer surface 48 Molding section 48a Convex curved surface 50 Intermediate cylinder 51 Stepped section (initial step) 52,53 Stepped section 61 Shaping punch 63 Tapered surface 64 Convex curved surface 65 Orthopedic surface 70 Chuck part 71 Curling Tool 72 Molding groove

Claims

1. A method for manufacturing a metal cup by press-forming a metal plate, comprising: a drawing and ironing process for forming a cylindrical body with a bottom by drawing and ironing a metal plate; a diameter expanding step in which, after the drawing and ironing step, a punch is pressed into the cylindrical body from the open end side to gradually expand the diameter of the body portion of the cylindrical body from the bottom side toward the open end side, thereby forming an intermediate cylindrical body having a tapered cylindrical portion; and The diameter expanding step includes: a step forming step of forming a step in a barrel portion of the cylindrical body using one or more punches, the step having a diameter on the open end side of the cylindrical body that is larger than a diameter on the bottom side of the cylindrical body; a shaping step of shaping the stepped portion into the tapered cylindrical portion while expanding the stepped portion using one or more of the punches; the punch used in the step forming step includes a stepped punch having a guide portion having a cylindrical outer surface and a forming portion having a diameter larger than that of the guide portion, the punch being continuous with the guide portion; The guide portion of the stepped punch is inserted into the cylindrical body first, thereby fitting the guide portion into the cylindrical body and expanding the diameter of the cylindrical body by the forming portion; The punch used in the step forming step further includes a lower step punch having a forming portion with a cylindrical outer surface, A method for manufacturing a metal cup, characterized in that an initial step is formed near the bottom of the body portion using the stepped punch, and then a lower step punch is fitted into the initial step and the lower part of the initial step is machined while expanding in diameter, thereby forming a lower step near the bottom of the body portion.

2. 2. The method for manufacturing a metallic cup according to claim 1, wherein in the diameter expanding step, the step forming step and the shaping step are alternately performed a plurality of times.

3. 2. The method for manufacturing a metallic cup according to claim 1, wherein after a plurality of steps are formed in the step forming step, the shaping step is carried out on these steps.

4. 4. The method for manufacturing a metallic cup according to claim 1, further comprising a curling step of folding back the open end of the intermediate cylindrical body to form a curled portion after the diameter expanding step.

5. 5. The method for manufacturing a metal cup according to claim 4, wherein the step forming step is carried out in the diameter expansion step, thereby forming an upper cylindrical portion along the can axial direction at the open end of the intermediate cylindrical body.

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