Method and apparatus for manufacturing rectangular cans

Abstract

To provide a square can manufacturing method and a square can manufacturing device that can improve form accuracy of a square can while suppressing increase in manufacturing burden.SOLUTION: A square can manufacturing method includes a form correction process in which a form of an intermediate molded product 60D is corrected. In the form correction process, each planned long side wall part is pushed toward a short side direction outer side by a form correction punch 52 inserted in the intermediate molded product 60D thereby increasing a short side direction interval between the planned long side wall parts, and a planned bottom wall part is pinched between the form correction punch 52 and a bottom wall pressing component 53 located on an outside surface side of the planned bottom wall part thereby flattening the planned bottom wall part.SELECTED DRAWING: Figure 3

Description

Technical Field

[0001] The present invention relates to a method for manufacturing a square can and a square can manufacturing apparatus for forming a square can, and particularly to a method for manufacturing a square can and a square can manufacturing apparatus for a square can used as a case for a lithium ion battery.

Background Art

[0002] Conventionally, as a method for manufacturing a metal square can having a bottom wall and a square cylindrical portion, it is known to manufacture a square can by subjecting a blank to multiple drawing processes or drawing and ironing processes (for example, see Patent Document 1). Also, in the ironing process that is carried out as the final step of such a drawing process or drawing and ironing process, considering the shape of the outer dimensions, inner dimensions, etc. of the square cylindrical portion of the final molded product, a punch having a punch processing outer peripheral surface formed in a substantially rectangular cross-sectional shape, and a die having a die processing through hole formed in a substantially rectangular cross-sectional shape are also known to be used.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] However, when forming a rectangular cylindrical portion 165 including long side walls 166 and short side walls 167 by drawing and ironing, as shown in Figure 10, the drawing process is more pronounced near the R-shaped corner walls 168 of the rectangular cylindrical portion 165, while the ironing process is more pronounced near the long side walls 166 (especially the central part in the long side direction). As a result, there is a difference in material flow between these areas, and a complex internal stress state occurs near the boundary between the corner walls 168, where the drawing process is more pronounced, and the long side walls 166, where the ironing process is more pronounced. Consequently, a so-called canning phenomenon can occur, as shown in Figure 10, where the central part in the long side direction of each long side wall 166 is concave inward in the short side direction.

[0005] This canning phenomenon becomes more pronounced when the flattening ratio (ratio of the length to the length) of the rectangular cylindrical portion 165 is high. Furthermore, in products (rectangular cans) where the flange portion formed on the tip side of the rectangular cylindrical portion 165 during the molding process is ultimately cut off, the deformation due to the canning phenomenon becomes larger because the flange portion, which plays a role in suppressing the aforementioned strain deformation, is removed.

[0006] On the other hand, during the process of forming a rectangular can using the drawing or ironing processes described above, bulging outwards (downwards) may occur on the bottom wall. Depending on the intended use of the rectangular can, such as when using it for lithium-ion battery cases that require high dimensional accuracy, this outward bulging of the bottom wall may not be acceptable.

[0007] Therefore, the present invention aims to solve these problems and provide a method and apparatus for manufacturing square cans that can improve the shape accuracy of square cans while suppressing an increase in manufacturing burden. [Means for solving the problem]

[0008] The present invention provides a method for manufacturing a rectangular can, comprising a rectangular cylindrical portion having a bottom wall, a pair of long side walls, and a pair of short side walls, wherein the method includes a shape correction step for correcting the shape of an intermediate molded product, and in the shape correction step, the long side wall pressing portion of a shape correction punch inserted into the intermediate molded product pushes each of the planned long side wall portions of the intermediate molded product outward in the short side direction, thereby widening the short side spacing between the planned long side wall portions, and flattens the planned bottom wall portion by sandwiching it between the bottom wall pressing portion of the shape correction punch inserted into the intermediate molded product and a bottom wall pressing member positioned on the outer surface side of the planned bottom wall portion of the intermediate molded product, thereby solving the above problem. The rectangular can manufacturing apparatus of the present invention is a rectangular can manufacturing apparatus that manufactures a rectangular can having a bottom wall and a rectangular cylindrical portion having a pair of long side walls and a pair of short side walls, wherein the rectangular can manufacturing apparatus includes a shape correction unit for correcting the shape of an intermediate molded product, and the shape correction unit is configured to widen the short-side spacing between the planned long side walls by pressing each planned long side wall portion of the intermediate molded product outward in the short-side direction with the long side wall pressing portion of the shape correction punch inserted into the intermediate molded product, and to flatten the planned bottom wall portion by sandwiching it with the bottom wall pressing portion of the shape correction punch inserted into the intermediate molded product and the bottom wall pressing member arranged on the outer surface side of the planned bottom wall portion of the intermediate molded product, thereby solving the above problem. [Effects of the Invention]

[0009] According to the present invention, in a shape correction process for correcting the shape of an intermediate molded product, the long side wall pressing portion of a shape correction punch inserted into the intermediate molded product pushes each planned long side wall portion of the intermediate molded product outward in the short side direction, thereby widening the short side spacing between the planned long side wall portions. At the same time, the planned bottom wall portion is sandwiched between the bottom wall pressing portion of the shape correction punch inserted into the intermediate molded product and a bottom wall pressing member positioned on the outer surface side of the planned bottom wall portion of the intermediate molded product, thereby flattening (bringing it closer to a flat state). As a result, it is possible to correct the shape of the rectangular cylindrical portion and the shape of the bottom wall in a single step of inserting the shape correction punch into the intermediate molded product and then sandwiching the planned bottom wall portion between the shape correction punch and the bottom wall pressing member. Therefore, it is possible to improve the shape accuracy of the rectangular can while suppressing an increase in manufacturing burden.

[0010] Furthermore, in the deep drawing or ironing process for forming rectangular cans, it is conceivable to suppress outward bulging of the bottom wall by sandwiching the planned bottom wall portion of the intermediate molded product between a punch and a member installed on the outside of the planned bottom wall portion. However, with such a configuration, the punch stroke must be designed to be large in the deep drawing or ironing process, and the member installed on the outside of the planned bottom wall portion must also be structured to move in accordance with the movement of the punch, which leads to increased equipment costs and a decrease in manufacturing speed. In contrast, the present invention does not require such a structure, thus avoiding increased equipment costs and a decrease in manufacturing speed. [Brief explanation of the drawing]

[0011] [Figure 1] An explanatory diagram showing a rectangular can, which is the final molded product of the rectangular can manufacturing method according to one embodiment of the present invention. [Figure 2] An explanatory diagram showing each step in the manufacturing process of rectangular cans. [Figure 3] An explanatory diagram showing each step in the manufacturing process of rectangular cans. [Figure 4] An explanatory diagram showing the squeezing and cutting unit. [Figure 5] An explanatory diagram showing the process during the drawing and ironing process. [Figure 6]An explanatory diagram showing a state where a punch is inserted into the die - machined through - hole of the draw and ironing unit in a no - load state and a modified example. [Figure 7] An explanatory diagram showing the die and punch during draw and ironing. [Figure 8] An explanatory diagram showing the shape correction unit. [Figure 9] An explanatory diagram showing the shape correction unit. [Figure 10] An explanatory diagram explaining the canning phenomenon.

Embodiments for Carrying Out the Invention

[0012] Hereinafter, a rectangular can manufacturing method and a rectangular can manufacturing apparatus 10 according to an embodiment of the present invention will be described based on the drawings. [Rectangular can 60 (final molded product)]

[0013] First, the rectangular can 60, which is the final molded product manufactured by the rectangular can manufacturing method and the rectangular can manufacturing apparatus 10, is made of a metal such as aluminum. In this embodiment, it is used as the case of a lithium - ion battery. As shown in FIG. 1, it includes a flat (or substantially flat) bottom wall 6 on and a rectangular cylindrical portion 65.

[0014] As shown in FIG. 1, the bottom wall 61 is formed in a substantially rectangular (or rectangular) shape having a pair of bottom long - side portions 62 and a pair of bottom short - side portions 63 at its outer edge. The bottom long - side portion 62 is a portion that extends linearly (or substantially linearly) along the long - side direction. The bottom short - side portion 63 is a portion that extends linearly (or substantially linearly) along the short - side direction so as to form a 90° angle with the bottom long - side portion 62. Between the bottom long - side portion 62 and the bottom short - side portion 63, a bottom curved corner portion 64 that is convexly curved on the outer peripheral side and smoothly connects the bottom long - side portion 62 and the bottom short - side portion 63 is formed. In this embodiment, each bottom curved corner portion 64 is formed by curving with the same single R (single radius of curvature).

[0015] As shown in FIG. 1, the rectangular cylindrical portion 65 has a pair of long side walls 66 arranged to face each other in the short side direction and a pair of short side walls 67 arranged to face each other in the long side direction. As shown in FIG. 1, each long side wall 66 is a flat plate-shaped (or substantially flat plate-shaped) portion formed so as to rise upward from the bottom long side portion 62, and the pair of long side walls 66 are formed parallel to each other. As shown in FIG. 1, each short side wall 67 is a flat plate-shaped (or substantially flat plate-shaped) portion formed so as to rise upward from the bottom short side portion 63 so as to form a 90° angle with the long side wall 66, and the pair of short side walls 67 are formed parallel to each other. Between the long side wall 66 and the short side wall 67, an R-shaped corner wall 68 is formed that curves convexly on the outer peripheral side, is formed so as to rise upward from the bottom curved corner portion 64, and smoothly connects the long side wall 66 and the short side wall 67. In the present embodiment, each corner wall 68 is formed by curving with the same single R (single radius of curvature). [Method for manufacturing a rectangular can]

[0016] The method for manufacturing a rectangular can manufactures a rectangular can 60. As shown in FIGS. 2 and 3, it has a blank preparation step of preparing a blank 60A, a coining step of performing coining on a predetermined portion of the blank 60A, a first drawing step of performing the first drawing on the blank 60A that has undergone the coining step, a second drawing step of performing the second drawing on the cup-shaped first intermediate molded product 60B that has undergone the first drawing step, a drawing ironing step of performing drawing ironing on the second intermediate molded product 60C obtained by the second drawing step, and a shape correction step of correcting the shape of the third intermediate molded product 60D obtained by the drawing ironing step.

[0017] Hereinafter, each step of the method for manufacturing a rectangular can will be specifically described.

[0018] First, as shown in FIG. 2(a), the blank preparation step forms a blank 60A as a metal plate by performing punching on a strip plate made of metal such as aluminum.

[0019] The coining process, as shown in Figure 2(b), involves applying a press in the thickness direction to a predetermined location on the blank 60A to reduce its thickness. In this embodiment, the bottom wall portion of the blank 60A (the portion that will become the bottom wall 61 in the final molded product, the rectangular can 60) is subjected to a coining process that reduces the thickness of the sheet metal by pressing it in the thickness direction.

[0020] The first drawing process, as shown in Figure 2(c), involves drawing the blank 60A that has undergone the coining process to form a cup-shaped first intermediate molded product 60B. Specifically, in the first drawing process, the blank 60A is held down from above by a blank holder 23, which functions as a wrinkle suppressor to prevent wrinkles from forming on the blank 60A. The blank 60A is then pushed (pulled in) from above by a punch 22 into a die-processing through-hole 21a formed in the die 21, thereby plastically deforming the blank 60A and forming a cup-shaped first intermediate molded product 60B.

[0021] As shown in Figure 3(d), the second drawing process involves applying a second drawing process to the first intermediate molded product 60B obtained in the first drawing process to form the second intermediate molded product 60C. Specifically, in the second drawing process, the first intermediate molded product 60B is held down from above (inside) by a blank holder 33, which functions as a wrinkle suppressor to prevent wrinkles from forming on the second intermediate molded product 60C. The first intermediate molded product 60B is then pushed (pulled in) by a punch 32 into a die-processing through-hole 31a formed in the die 31, thereby plastically deforming the first intermediate molded product 60B and forming the second intermediate molded product 60C. During this drawing process, only the punch 32 and (part of) the first intermediate molded product 60B are inserted into the die-cut through-hole 31a; the blank holder 33 is not inserted.

[0022] As shown in Figure 3(e), the drawing and ironing process involves drawing and ironing mainly on the planned cylindrical portion 65C of the second intermediate molded product 60C (the portion that will become the rectangular cylindrical portion 65 in the final molded product) in the gap between the die processing through hole 41a formed in the die 41 and the punch 42 inserted into the die processing through hole 41a, thereby forming the third intermediate molded product 60D. In addition, during the drawing and ironing process, a portion of the planned bottom wall portion 61C of the second intermediate molded product 60C (the portion that will become the bottom wall 61 in the final molded product) is also subjected to the drawing and ironing process.

[0023] Specifically, in the drawing and ironing process, as shown in Figure 5, the second intermediate molded product 60C is held down from above (inside) by a blank holder 43 which functions as a wrinkle suppressor to prevent wrinkles from forming on the third intermediate molded product 60D. The punch 42 is then moved relative to the die 41 (in this embodiment, the punch 42 and blank holder 43 are moved relative to the die 41 which is fixed in place). The punch 42 pushes (pushes) the second intermediate molded product 60C into the die-processed through-hole 41a, and the second intermediate molded product 60C is plastically deformed in the gap between the die-processed inner circumferential surface 41b of the die-processed through-hole 41a and the punched outer circumferential surface 42a of the punch 42 to form the third intermediate molded product 60D. During the drawing and ironing process described above, only the punch 42 and (part of) the second intermediate molded product 60C are inserted into the die-processed through-hole 41a, and the blank holder 43 is not inserted.

[0024] As shown in Figures 4 and 5, the die 41 used in the drawing and ironing process has a die processing through-hole 41a that is formed to penetrate in the direction of punch movement (up and down in this embodiment) during the drawing and ironing process. As shown in Figures 4 and 5, the die-machined through-hole 41a has a die-machined inner circumferential surface 41b formed as a surface parallel to the punch movement direction (vertical direction), and a tapered surface 41f formed on the front side (upper side) of the die-machined inner circumferential surface 41b in the punch movement direction (vertical direction). As shown in Figures 4 to 6, the die-machined inner circumferential surface 41b has a pair of die long-side wall machining sections 41c that machine the planned long-side wall portion 66C of the second intermediate molded product 60C (the portion that will become the long-side wall 66 in the final molded product), and a pair of die short-side wall machining sections 41d that machine the planned short-side wall portion 67C of the second intermediate molded product 60C (the portion that will become the short-side wall 67 in the final molded product). As shown in Figures 4 and 6(a), each die's long side wall processing section 41c is formed to extend linearly along the long side when viewed in the punch movement direction (up and down direction) (when the die 41 is cut in cross-section with a plane perpendicular to the punch movement direction). As shown in Figures 4 and 6(a), each die's short-side wall processing section 41d is formed to extend linearly along the short side direction when viewed in the punch movement direction (up and down direction) (when the die 41 is cut in cross-section with a plane perpendicular to the punch movement direction). Furthermore, between the die long-side wall processing section 41c and the die short-side wall processing section 41d, as shown in Figures 4 and 6(a), a curved corner section 41e is formed that is convex on the outer circumference, smoothly connecting the die long-side wall processing section 41c and the die short-side wall processing section 41d. This curved corner section 41e functions as a processing area near the planned corner wall section 68C of the second intermediate molded product 60C (the section that will become the corner wall 68 of the rectangular cylindrical section 65 in the final molded product). In this embodiment, each curved corner section 41e is formed with the same single radius of curvature (single R). As shown in Figures 4 and 5, the tapered surface 41f is formed with an inclination such that it decreases in diameter (the width in the long and short directions becomes narrower) as it moves towards the back (down) side in the punch movement direction (up and down direction).

[0025] As shown in Figures 4 to 6, the punch 42 used in the drawing and ironing process has a punched outer peripheral surface 42a that is formed parallel to the punch movement direction (vertical direction) as an outer peripheral surface facing the inner surface of the die-processed through hole 41a during the drawing and ironing process. As shown in Figures 4 and 6(a), the punched outer surface 42a has a pair of punch long-side wall processing sections 42b that work in cooperation with the die long-side wall processing section 41c to process the planned long-side wall section 66C of the second intermediate molded product 60C, and a pair of punch short-side wall processing sections 42c that work in cooperation with the die short-side wall processing section 41d to process the planned short-side wall section 67C of the second intermediate molded product 60C.

[0026] As shown in Figure 6(a), each punch long-side wall processing section 42b has a processing apex 42b-1 located on the outermost side in the short-side direction of the punch long-side wall processing section 42b, and inclined sections 42b-2 formed on both sides of the processing apex 42b-1 in the long-side direction, which are inclined to move inward in the short-side direction as they move outward in the long-side direction, and has an overall shape in which the central part in the long-side direction bulges outward in the short-side direction than both ends in the long-side direction. As shown in Figure 6(a), the processed top portion 42b-1 is formed in the center (or near the center) of the long side of the punch's long side wall processed portion 42b. In this embodiment, when viewed in the direction of punch movement (up and down direction) (when the punch 42 is cut in cross-section with a plane perpendicular to the direction of punch movement), it is formed as a portion that extends linearly along the long side. Furthermore, if the processed top portion 42b-1 is formed as a linearly extending portion when viewed in cross-section, the amount of deflection that occurs in the die long side wall processed portion 41c due to the forming reaction force during the drawing process can be reduced compared to the case where the processed top portion 42b-1 is formed as a point when viewed in cross-section, as shown in the modified example in Figure 6(b). As shown in Figure 1, the inclined portion 42b-2 is formed as a linearly extending portion when viewed in the direction of punch movement (vertical direction) (when punch 42 is cut in cross-section with a plane perpendicular to the direction of punch movement).

[0027] As shown in Figure 6(a), each punch's short-side wall processing section 42c is formed to extend linearly along the short side when viewed in the punch movement direction (up and down direction) (when the punch 42 is cut in cross-section with a plane perpendicular to the punch movement direction).

[0028] Furthermore, between the punch long-side wall processing section 42b and the punch short-side wall processing section 42c, a curved corner section 42d is formed that is convex on the outer circumference, smoothly connecting the punch long-side wall processing section 42b and the punch short-side wall processing section 42c. The curved corner section 42d works in cooperation with the curved corner section 41e of the die 41 to function as a processing area near the planned corner wall section 68C of the second intermediate molded product 60C. In this embodiment, each curved corner section 42d is formed with the same single radius of curvature (single R).

[0029] During the drawing and ironing process, the second intermediate molded product 60C is pushed (pulled in) into the gap between the die's long side wall processing section 41c and the punch's long side wall processing section 42b, thereby performing an ironing process that mainly thins the thickness of the long side wall portion 66C of the second intermediate molded product 60C. Additionally, the second intermediate molded product 60C is pushed (pulled in) into the gap between the die's short side wall processing section 41d and the punch's short side wall processing section 42c, thereby performing a drawing process mainly around the corner wall portion 68C (and the short side wall portion 67C) of the second intermediate molded product 60C.

[0030] In this embodiment, when the flattening ratio (ratio of the length dimension to the length dimension) of the die-processed through-hole 41a is high, as shown in Figure 7(a), during the drawing process, the die's long-side wall processing portion 41c bends due to the forming reaction force, causing the center of the die's long-side wall processing portion 41c in the length direction to move outward in the short-side direction. As a result, as shown in Figure 6(a), the short-side distance W1 between the die's long-side wall processing portion 41c and the punch's long-side wall processing portion 42b at the center of the die's long-side wall processing portion 41c in the length direction widens compared to the state in which the punch 42 is inserted into the die-processed through-hole 41a under no load. Therefore, as shown in Figure 7(b), if the die long-side wall processing section 41c and the punch long-side wall processing section 42b are formed to extend linearly along the long side direction, and the short-side spacing W1 and W2 between the die long-side wall processing section 41c and the punch long-side wall processing section 42b is set to be constant, then the thickness of the long-side wall planned section 66C that has been subjected to drawing and ironing will be thicker in the center along the long side and will become thinner towards both ends along the long side, making it impossible to achieve a uniform thickness distribution of the long-side wall planned section 66C. In contrast, in this embodiment, as shown in Figure 6(a), the die long-side wall processing section 41c and the punch long-side wall processing section 42b are configured such that, when the punch 42 is inserted into the die processing through-hole 41a under no load (in other words, when the second intermediate molded product 60C is not interposed between the die long-side wall processing section 41c and the punch long-side wall processing section 42b, and no molding reaction force is applied to the die 41 and the punch 42), the short-side distance W1 between the long-side central part of the punch long-side wall processing section 42b and the die long-side wall processing section 41c is narrower than the short-side distance W2 between both long-side ends of the punch long-side wall processing section 42b and the die long-side wall processing section 41c. As a result, during drawing and ironing, when the die's long side wall processing portion 41c deflects due to the forming reaction force, it is possible to reduce the dimensional difference between the short-side distance W2 between the die's long side wall processing portion 41c and the punch's long side wall processing portion 42b at both ends in the long side direction and the short-side distance W1 between the die's long side wall processing portion 41c and the punch's long side wall processing portion 42b at the center in the long side direction. This makes it possible to make the thickness distribution of the planned long side wall portion 66C to be formed more uniform.

[0031] Furthermore, as shown in Figure 6(a), the die 41 and punch 42 are formed such that, when the punch 42 is inserted into the die through-hole 41a without load, the short-side spacing W1 between the center of the long-side wall processing portion 42b of the punch and the long-side wall processing portion 41c of the die is narrower than the long-side spacing W3 between the short-side wall processing portion 42c of the punch and the short-side wall processing portion 41d of the die.

[0032] Furthermore, as shown in Figure 6(a), the inner circumferential surface 41b of the die and the outer circumferential surface 42a of the punch are formed to be symmetrical in both the long and short directions when viewed in the punch movement direction (up and down direction). Furthermore, during the drawing and ironing process, the punch 42 is inserted into the die through-hole 41a such that the long-side spacing W1 and W2 between the die long-side wall processing portion 41c and the punch long-side wall processing portion 42b on both sides of the punch 42 in the long-side direction is the same, and the spacing W3 between the die short-side wall processing portion 41d and the punch short-side wall processing portion 42c on both sides of the punch 42 in the short-side direction is the same.

[0033] As shown in Figure 3(f), the shape correction process involves widening the short-side spacing between a pair of planned long-side wall portions 66D (parts that will become the long-side wall 66 in the final molded product) of the third intermediate molded product 60D obtained by the drawing and ironing process (widening process), and flattening the planned bottom wall portion 61D (part that will become the bottom wall 61 in the final molded product) of the third intermediate molded product 60D (applying a flattening process to make it closer to a flat state), thereby forming the fourth intermediate molded product 60E.

[0034] In the shape correction process, as shown in Figure 9, with the shape correction punch 52 inserted into the third intermediate molded product 60D, the shape correction punch 52 is moved relative to the die 51 (in this embodiment, the shape correction punch 52 is moved relative to the die 51 which is fixed in place), and the third intermediate molded product 60D is pushed (pulled in) into the die processing through hole 51a by the shape correction punch 52, and the planned bottom wall portion 61D of the third intermediate molded product 60D is sandwiched between the shape correction punch 52 and the bottom wall pressing member 53, thereby performing the above-mentioned widening and flattening processes in one step.

[0035] The following provides a detailed explanation of each step in the shape correction process.

[0036] First, as shown in Figures 8 and 9, the widening process involves inserting a shape-correcting punch 52 into the third intermediate molded product 60D, which is supported by an outer support member 54. The short-side wall pressing portion 52b of the shape-correcting punch 52 inserted into the third intermediate molded product 60D restricts the pair of short-side wall portions 67D from approaching each other, while the long-side wall pressing portion 52c of the shape-correcting punch 52 inserted into the third intermediate molded product 60D pushes each long-side wall portion 66D (especially near the longitudinal center) outward in the short-side direction, thereby widening the short-side distance between the pair of long-side wall portions 66D (especially between the longitudinal centers of the long-side wall portions 66D) in a wedge shape. This widening process allows for the correction of the shape even when a so-called canning phenomenon occurs, as shown in Figure 10, where the central part of each long side wall 166 in the long side direction is recessed inward in the short side direction.

[0037] As shown in Figure 9, the short-side wall pressing portion 52b is positioned on the opening side of the third intermediate molded product 60D, with the shape correction punch 52 inserted into the third intermediate molded product 60D, to press from the inside the long-side portions on both sides of each long-side wall portion 66D and each short-side wall portion 67D (the portion that will become the short-side wall 67 in the final molded product). As a result, the short-side wall-side pressing portion 52b, with the shape-correcting punch 52 inserted into the third intermediate molded product 60D, prevents (restricts) the long-side portions of the pair of long-side wall-planned portions 66D from moving closer to each other, and also prevents (restricts) the pair of short-side wall-planned portions 67D from moving closer to each other. Furthermore, with the shape-correcting punch 52 inserted into the third intermediate molded product 60D, the short-side wall pressing portion 52b may be designed to widen the gap between the two long-side portions of the pair of planned long-side wall portions 66D in a wedge shape in the short-side direction, or the short-side wall pressing portion 52b may be designed to widen the gap between the pair of planned short-side wall portions 67D in a wedge shape in the long-side direction. As shown in Figure 9, the short-side wall-side pressing portion 52b has a tapered portion on the back side (downward side) in the punch movement direction (up and down direction) that slopes inward in the long-side direction as it moves towards the back, which makes it easier to insert the shape-correcting punch 52 into the third intermediate molded product 60D. Furthermore, in this embodiment, the short-side wall-side pressing portion 52b is formed separately from the punch body 52a and is made of a separate member that is fixedly attached to the punch body 52a. This makes it easy to adjust the degree of pressure applied to the long-side wall-side planned portion 66D and the short-side wall-side planned portion 67D by the short-side wall-side pressing portion 52b. However, the short-side wall-side pressing portion 52b may also be formed integrally with the punch body 52a.

[0038] As shown in Figure 9, the long-side wall pressing portion 52c is positioned on the opening side of the third intermediate molded product 60D, with the shape-correcting punch 52 inserted into the third intermediate molded product 60D, so as to press from the inside the central portion in the long-side direction of each planned long-side wall portion 66D. As a result, the long-side wall pressing portion 52c performs the function of expanding the short-side distance between the pair of planned long-side wall portions 66D. As shown in Figure 9, the long-side wall pressing portion 52c has a pressing surface in which its central part in the long-side direction bulges outward in the short-side direction compared to both ends in the long-side direction. Furthermore, as shown in Figure 9, the long side wall pressing portion 52c has a tapered portion on the back side (downward side) in the punch movement direction (up and down direction) that slopes inward in the short side direction as it moves towards the back, which makes it easier to insert the shape-correcting punch 52 into the third intermediate molded product 60D. Furthermore, in this embodiment, the long-side wall pressing portion 52c is formed separately from the punch body 52a and is made of a separate member that is fixedly attached to the punch body 52a, thereby allowing for easy adjustment of the degree of pressure applied to the long-side wall target portion 66D by the long-side wall pressing portion 52c. However, the long-side wall pressing portion 52c may also be formed integrally with the punch body 52a.

[0039] In this embodiment, as shown in Figure 9, the short-side wall pressing portion 52b and the long-side wall pressing portion 52c are positioned to correspond to the opening side (near the opening) of the third intermediate molded product 60D with the shape correction punch 52 inserted inside the third intermediate molded product 60D. However, the arrangement of the short-side wall pressing portion 52b and the long-side wall pressing portion 52c relative to the third intermediate molded product 60D with the shape correction punch 52 inserted inside the third intermediate molded product 60D is not limited to the above. For example, the short-side wall pressing portion 52b and the long-side wall pressing portion 52c may be positioned to correspond to the vicinity of the center in the punch movement direction (vertical direction) of the third intermediate molded product 60D with the shape correction punch 52 inserted inside the third intermediate molded product 60D. Furthermore, the number of short-side wall pressing portions 52b and long-side wall pressing portions 52c is not limited to those shown in Figures 8 and 9. For example, in addition to those shown in Figures 8 and 9, additional short-side wall pressing portions 52b and long-side wall pressing portions 52c may be provided, positioned near the center of the punch movement direction (vertical direction) of the third intermediate molded product 60D when the shape-correcting punch 52 is inserted.

[0040] As shown in Figure 9, the outer support member 54 supports the flange portion 69D of the third intermediate molded product 60D from below during the widening process, and is positioned to press from the outside both sides of the long side direction of each planned long side wall portion 66D on the opening side (near the opening) of the third intermediate molded product 60D. As a result, the outer support member 54 supports the third intermediate molded product 60D when the shape-correcting punch 52 is inserted into the third intermediate molded product 60D, and also functions to prevent (restrict) the portions on both sides of the planned long side walls 66D in the long side direction from spreading outward in the short side direction.

[0041] Depending on the embodiment, other support members may be provided to support the third intermediate molded product 60D from the outside at any position, either in place of or in addition to the outer support member 54.

[0042] The flattening process involves moving the shape correction punch 52, which is inserted into the third intermediate molded product 60D. The bottom wall pressing portion 52d of the shape correction punch 52 is used to clamp the bottom wall planned portion 61D between the bottom wall pressing portion 52d and the bottom wall pressing member 53 positioned on the outer surface side of the bottom wall planned portion 61D. The shape correction punch 52 also presses the third intermediate molded product 60D (specifically the bottom wall planned portion 61D and a portion of the cylindrical planned portion 65D near the bottom wall planned portion 61D) into the die-processing through hole 51a. By pushing (pulling) the punch 52 into place, a drawing and ironing process is applied over the entire circumferential area (region R shown in Figure 9) near the connection point (curved corner) between the planned cylindrical portion 65D and the planned bottom wall portion 61D of the third intermediate molded product 60D, in the gap between the die-processed inner circumferential surface of the die-processed through-hole 51a formed in the die 51 and the punched outer circumferential surface of the shape-correcting punch 52 inserted into the die-processed through-hole 51a, thereby flattening the planned bottom wall portion 61D.

[0043] The pressing surface of the bottom wall pressing portion 52d of the shape-correcting punch 52 and the pressing surface of the bottom wall pressing member 53, which sandwich the planned bottom wall portion 61D, are both formed in a flat shape. Although the bottom wall pressing portion 52d of the shape-correcting punch 52 is formed integrally with the punch body 52a, the bottom wall pressing portion 52d may be made from a separate component formed separately from the punch body 52a. Furthermore, the bottom wall pressing member 53 is supported by an air cylinder (not shown), and when pressed downward by the punch (third intermediate molded product 60D) during the flattening process, it moves downward together with the punch (third intermediate molded product 60D), sandwiching the bottom wall target portion 61D between itself and the shape-correcting punch 52, thereby applying appropriate pressure to the bottom wall target portion 61D. In addition, during the flattening process described above, the air cylinder (not shown) mitigates the impact when the punch (third intermediate molded product 60D) collides with the bottom wall pressing member 53.

[0044] Furthermore, in the first and second drawing processes and the drawing and ironing process described above, no equipment is used to support the outside (bottom) of the planned bottom wall portion, which corresponds to the bottom wall pressing member 53 (and air cylinder). In other words, no equipment is used to clamp the planned bottom wall portion 61D with a punch that moves downward.

[0045] In the shape correction process of this embodiment described above, after inserting the shape correction punch 52 into the third intermediate molded product 60D, the shape correction (widening) of the cylindrical portion planned portion 65D and the shape correction (flattening) of the bottom wall planned portion 61D can be performed together in a single step (single operation) by moving the shape correction punch 52 toward the die 51 and the bottom wall pressing member 53. Therefore, the shape accuracy of the square can 60 can be improved while suppressing an increase in the manufacturing burden. Furthermore, in drawing or ironing processes, it is conceivable to suppress outward bulging of the bottom wall by sandwiching the planned bottom wall portion of the intermediate molded product between a punch and a member installed on the outside of the planned bottom wall portion. However, with such a configuration, the punch stroke must be designed to be large in the drawing or ironing process, and the member installed on the outside (bottom) of the planned bottom wall portion must also be structured to move in accordance with the movement of the punch, which leads to increased equipment costs and a decrease in manufacturing speed. In contrast, the present invention does not require such a structure, the stroke amount of the bottom wall pressing member 53 can be short, and increased equipment costs and a decrease in manufacturing speed can be avoided.

[0046] Furthermore, the rectangular can manufacturing method includes, in addition to the above-mentioned steps, various other steps such as a trimming process to cut off unnecessary parts near openings such as flanges from the fourth intermediate molded product 60E obtained by the shape correction process, and a cleaning process. [Square can manufacturing apparatus 10]

[0047] Next, the rectangular can manufacturing apparatus 10 will be described below.

[0048] As shown in Figures 2 and 3, the rectangular can manufacturing apparatus 10 includes a first drawing unit 20 for performing a first drawing process, a first drawing unit 20 for performing a second drawing process, a drawing and ironing unit 40 for performing a drawing and ironing process, and a shape correction unit 50 for performing a shape correction process.

[0049] As shown in Figures 2 and 3, the first and second squeezing units 20 and 30 and the squeezing and ironing unit 40 are equipped with dies 21, 31 and 41, punches 22, 23 and 24, blank holders 23, 33 and 43, and various peripheral equipment such as drive means consisting of actuators and motors for driving each part such as the punches, and support members. Furthermore, as shown in Figure 4, the shape correction unit 50 includes a die 51, a shape correction punch 52, a bottom wall pressing member 53, an outer support member 54, and various peripheral equipment such as drive means and support members, including actuators and motors that drive each part such as the punch. The specific configuration and function of each of these parts are as described above.

[0050] Although embodiments of the present invention have been described in detail above, the present invention is not limited to the above embodiments, and various design changes can be made without departing from the present invention as described in the claims, such as arbitrarily combining the configurations of the above or below embodiments or modified examples to construct a rectangular can manufacturing method and a rectangular can manufacturing apparatus 10.

[0051] For example, in the embodiment described above, it was explained that two drawing processes (or drawing processes) are performed before the drawing process, but the number of drawing processes (or drawing processes) performed before the drawing process may be one or three or more.

[0052] Furthermore, in the above-described embodiment, the die long-side wall processing portion 41c is formed to extend linearly along the long-side direction, and the punch long-side wall processing portion 42b is formed to have an overall shape in which its center in the long-side direction bulges outward in the short-side direction compared to both ends in the long-side direction. This is described so that when the punch 42 is inserted into the die processing through hole 41a without load, the short-side distance W1 between the center of the punch long-side wall processing portion 42b in the long-side direction and the die long-side wall processing portion 41c is narrower than the short-side distance W2 between both ends of the punch long-side wall processing portion 42b in the long-side direction and the die long-side wall processing portion 41c. However, the specific configuration of the long-side wall processing sections 41c and 42b is not limited to the above, and any configuration is acceptable as long as the spacing W1 becomes narrower than the spacing W2 in the above state. For example, if the punch long-side wall processing section 42b is formed to have an overall shape in which its center in the long-side direction bulges outward in the short-side direction than both ends in the long-side direction, the die long-side wall processing section 41c may be formed in a shape other than a shape that extends linearly along the long-side direction (for example, an overall shape in which its center in the long-side direction bulges outward in the short-side direction than both ends in the long-side direction, or an overall shape in which its center in the long-side direction bulges inward in the short-side direction than both ends in the long-side direction). Furthermore, the die long-side wall processing portion 41c may be formed such that its center in the long-side direction bulges inward in the short-side direction compared to both ends in the long-side direction, thereby making the spacing W1 narrower than the spacing W2 in the above state. In this case, various shapes are possible for the punch long-side wall processing portion 42b, such as a shape that extends linearly along the long-side direction, an overall shape in which its center in the long-side direction bulges outward in the short-side direction compared to both ends in the long-side direction, or an overall shape in which its center in the long-side direction bulges inward in the short-side direction compared to both ends in the long-side direction.

[0053] Furthermore, when the punch long-side wall processing portion 42b is formed to have an overall shape in which its center in the long-side direction bulges outward in the short-side direction compared to both ends in the long-side direction, the specific form of the punch long-side wall processing portion 42b is not limited to that of the embodiment described above. For example, in the example shown in Figure 6(a), the processed top portion 42b-1 is formed as a portion that extends linearly along the long side when viewed in cross-section. However, as shown in the modified example in Figure 6(b), the processed top portion 42b-1 may be a point-like portion when viewed in cross-section. Furthermore, in the example shown in Figure 6(a), the inclined portion 42b-2 is formed as a portion that extends in a straight line when viewed in cross-section. However, as shown in the modified example in Figure 6(b), the inclined portion 42b-2 may be a portion that extends in a curve when viewed in cross-section, or the inclined portion 42b-2 may be formed as a portion that combines one or more straight lines and one or more curves when viewed in cross-section. In the modified example shown in Figure 6(b), the punch's long-side wall processing portion 42b is formed in a so-called drum shape, where the entire portion is curved outward in the short-side direction, convexly, such that its center in the long-side direction bulges outward in the short-side direction compared to both ends in the long-side direction.

[0054] Similarly, when the die long-side wall processing portion 41c is formed to have a processing apex (located furthest inward in the short-side direction of the die long-side wall processing portion 41c) and inclined portions (formed on both sides of the processing apex in the long-side direction and inclined to move outward in the short-side direction as it moves outward in the long-side direction), and the center in the long-side direction bulges inward in the short-side direction compared to both ends in the long-side direction, the processing apex of the die long-side wall processing portion 41c may be formed as a portion that extends linearly along the long-side direction when viewed in cross-section, or as a point-like portion when viewed in cross-section. Furthermore, the inclined portion of the die long side wall processing portion 41c may be formed as a portion that extends in a straight line when viewed in cross-section, or as a portion that extends in a curved shape when viewed in cross-section, or as a portion that is a combination of one or more straight lines and one or more curves when viewed in cross-section.

[0055] Furthermore, in the embodiments described above, the die short-side wall processing portion 41d and the punch short-side wall processing portion 42c were described as being formed to extend linearly along the long-side direction, but these processing portions may be formed in other shapes (for example, curved shapes when viewed in the direction of punch movement). Furthermore, in the embodiments described above, the die-processed inner circumferential surface 41b and the punch-processed outer circumferential surface 42a were described as being formed as surfaces parallel to the punch movement direction (vertical direction), but the specific configurations of the die-processed inner circumferential surface 41b and the punch-processed outer circumferential surface 42a are not limited thereto. [Explanation of symbols]

[0056] 10. Square can manufacturing equipment 20 ··· First aperture unit 21 ··· Dai 21a ··· Die-machined through hole 22... Punch 23... Blank holder 30 ··· Second aperture unit 31 ··· Dai 31a ··· Die-machined through hole 32... Punch 33... Blank holder 40 ··· Squeezing and squeezing unit 41 ··· Dai 41a ··· Die-machined through hole 41b ··· Die-machined inner surface 41c ··· Die Long Side Wall Processing Section 41d ··· Die short side wall processing section 41e ··· Curved corner 41f ··· Tapered surface 42... Punch 42a ··· Punched outer surface 42b ··· Punch long side wall processing section 42b-1 ··· Machining top 42b-2 ··· Inclined section 42c ··· Punch short side wall processing section 42d ··· Curved corner 43... Blank holder 50 ··· Shape correction unit 51 ··· Dai 51a ··· Die-machined through hole 52 ··· Shape correction punch 52a ··· Punch body 52b ··· Short side wall-side retaining section 52c ··· Long side wall pressing section 52d ··· Bottom wall pressing section 53 ··· Bottom wall pressing member 54 ··· Outer support member 60 ··· Square can (final molded product) 61 ··· Bottom wall 62 ... bottom long side 63 ··· Base short side 64 ... bottom curved corner 65 ··· Rectangular cylindrical part 66... ​​Long side wall 67 ··· Short side wall 68... Corner wall 60A ··· Blank 60B 1st intermediate molded product 60C...Second intermediate molded product 61C... Planned bottom wall section 65C ··· Planned cylindrical section 66C... Planned section of the long side wall 67C ··· Planned short side wall section 68C ··· Corner wall planned section 60D 3rd intermediate molded product 61D ··· Planned bottom wall section 65D ··· Planned cylindrical section 66D... Planned long wall section 67D ··· Planned short-side wall section 69D ··· Flange section 60E 4th intermediate molded product

Claims

1. A method for manufacturing a rectangular can, comprising a rectangular cylindrical section having a bottom wall, a pair of long side walls, and a pair of short side walls, The aforementioned method for manufacturing rectangular cans includes a shape correction step for correcting the shape of an intermediate molded product. A method for manufacturing a rectangular can, characterized in that, in the shape correction step, the long side wall pressing portion of a shape correction punch inserted into the intermediate molded product pushes each of the planned long side walls of the intermediate molded product outward in the short side direction, thereby widening the short side spacing between the planned long side walls, and flattening the planned bottom wall by sandwiching it between the bottom wall pressing portion of the shape correction punch inserted into the intermediate molded product and a bottom wall pressing member positioned on the outer surface side of the planned bottom wall of the intermediate molded product.

2. The method for manufacturing a rectangular can according to claim 1, characterized in that, in the shape correction step, when the planned bottom wall portion is sandwiched between the shape correction punch and the bottom wall pressing member, the intermediate molded product is pressed into the die-processed through hole formed in the die by the shape correction punch, and the intermediate molded product is subjected to drawing and ironing in the gap between the die-processed through hole and the shape correction punch.

3. The method for manufacturing a rectangular can according to claim 1 or 2, characterized in that the long side wall pressing portion is made of a member that is formed separately from the punch body and attached to the punch body.

4. The method for manufacturing a rectangular can according to any one of claims 1 to 3, characterized in that the long-side wall pressing portion has a pressing surface in the center of the long-side direction that bulges outward in the short-side direction.

5. A rectangular can manufacturing apparatus comprising a rectangular cylindrical section having a bottom wall, a pair of long side walls, and a pair of short side walls, The aforementioned rectangular can manufacturing apparatus includes a shape correction unit for correcting the shape of intermediate molded products. The shape correction unit is configured to widen the short-side spacing between the long-side wall portions of the intermediate molded product by pressing each of the long-side wall portions of the intermediate molded product outward in the short-side direction with the long-side wall pressing portion of the shape correction punch inserted into the intermediate molded product, and to flatten the bottom wall portion by sandwiching it between the bottom wall portion of the intermediate molded product and a bottom wall pressing member positioned on the outer surface side of the bottom wall portion of the intermediate molded product.

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