Method for manufacturing bottomed container, and press system

Abstract

To prevent occurrence of distortion on the bottom side of a workpiece when manufacturing a rectangular tubular container with a bottom by shaping a workpiece from a flat plate state into a rectangular tubular state having a bottom by performing a plurality of press drawing steps using a plurality of dies having elongated shaping holes.SOLUTION: A first press drawing step S1 is performed using a first die having an elongated first shaping hole 73A, and is configured as at least any one of press drawing steps other than a final step. A second press drawing step S2 is performed using a second die having an elongated second shaping hole 73B, and is configured as a press drawing step subsequent to the first press drawing step S1. The first shaping hole 73A is formed to have a greater dimension in a width direction Y perpendicular to a longitudinal direction X than the second shaping hole 73B, and is formed to be narrowed inward in the width direction Y from both edges toward a center in the longitudinal direction.SELECTED DRAWING: Figure 7

Description

[Technical field]

[0001] The present invention relates to a method for manufacturing a bottomed container, and a press system for producing a bottomed rectangular cylindrical container by performing multiple press drawing processes to shape a workpiece from a flat plate into a rectangular cylindrical shape having a bottom. [Background technology]

[0002] In press molding, a workpiece is processed using a metal mold that includes a die with a forming hole and a punch that presses the workpiece into the forming hole of the die. When forming a rectangular cylindrical bottomed container with a cross section that has a longitudinal shape and a bottom, press molding is performed to form a rectangular cylindrical bottomed container from a flat plate by performing a press drawing process multiple times using a plurality of metal molds with elongated forming holes. For example, Non-Patent Document 1 discloses a press molding method in which a rectangular cylindrical bottomed container with a substantially rectangular cross section is formed from a flat plate by performing a press drawing process multiple times using a plurality of metal molds with elongated forming holes.

[0003] As disclosed in Non-Patent Document 1, a square cylindrical bottomed container is manufactured by forming it from a flat plate by performing multiple press drawing processes using multiple dies having elongated forming holes. Note that the shape of the bottomed container formed through multiple press drawing processes may determine the final shape of the product, but there are also cases where a punching process is further performed on the bottomed container formed in the square cylindrical shape after multiple press drawing processes are completed. In the punching process performed after multiple press drawing processes are completed, a punching die is used to perform punching on the bottomed container formed in the square cylindrical shape, reducing the plate thickness of the bottomed container wall to determine the final shape of the product.

[0004] As disclosed in Non-Patent Document 1, when forming a bottomed container in the shape of a square cylinder with a substantially rectangular cross section, a die having a forming hole with no straight line portion and an elliptical shape spreading outward is used in the press drawing steps other than the final one among multiple press drawing steps. That is, in the intermediate press drawing steps other than the final press drawing step which defines the final shape of the product or defines a shape corresponding to the final shape of the product, the elongated forming hole in the die is formed into a shape which is connected in a gentle arc shape all around and spreads out like an ellipse.

[0005] When press drawing is performed using a die having a long hole-shaped forming hole, a compressive force is generated in the workpiece to be press drawn in the portions machined at both ends in the longitudinal direction, which is the direction in which the forming hole extends in the shape of a long hole. On the other hand, when the portion extending along the longitudinal direction of the long hole-shaped forming hole is formed linearly, the portion machined at the longitudinal center of the forming hole in the workpiece is in a state in which bending is performed without generating a circumferential force. In this case, the workpiece is in a state in which a compressive force acts from the portion machined at both ends in the longitudinal direction to the portion machined at the longitudinal center. That is, by generating a compressive force in the portion machined at both ends in the longitudinal direction, a compressive force is also generated at the longitudinal center in the state in which bending is performed due to the influence of the compressive force. As a result, buckling occurs in the portion machined at the longitudinal center, which makes it easier for wrinkles to occur. Therefore, as disclosed in Non-Patent Document 1, when press drawing is performed using a die having a long hole-shaped forming hole in a press drawing process other than the final one, a die having a forming hole with an elliptical shape spreading outward over the entire circumference is used. By using a die having an elliptical shape, compressive force is generated not only in the parts processed at both ends in the longitudinal direction of the workpiece to be press drawn, but also in the parts processed at the longitudinal center. Therefore, compressive force is generated over the entire circumferential direction of the workpiece, and buckling is less likely to occur in the parts processed at the longitudinal center, thereby suppressing the occurrence of wrinkles. [Prior art documents] [Non-patent literature]

[0006] [Non-Patent Document 1] Hiromi Yoshida, "The Complete Guide to Press Processing," Nikkan Kogyo Shimbun, September 2015, pp. 94-95 Summary of the Invention [Problem to be solved by the invention]

[0007] In the press drawing process using a die having a long hole-shaped forming hole, a die having an elliptical forming hole is used, so that a compressive force is generated over the entire circumference of the workpiece in the circumferential direction, and the occurrence of wrinkles due to buckling at the center side in the longitudinal direction can be suppressed. However, the amount of drawing is large at both ends in the longitudinal direction, and plastic flow of the material occurs from both ends in the longitudinal direction to the center side, so that when a circumferential compressive force is generated even in the part processed at the center side in the longitudinal direction, the volume of the material at the center side in the longitudinal direction becomes excessive. Therefore, the material at the center side in the longitudinal direction with an excess volume plastically flows toward the bottom side of the workpiece that is not restrained by the punch and die of the die. As a result, there is a problem that distortion is likely to occur at the bottom side of the central part in the longitudinal direction of the workpiece after the press drawing process. In addition, in a bottomed container, which is a workpiece formed after multiple press drawing processes, if distortion occurs on the bottom side of the central portion in the longitudinal direction, when a stamping process is performed after multiple press drawing processes, the bottomed container will have an overall distortion or dimensional abnormality. More specifically, if distortion occurs on the bottom side of the central portion in the longitudinal direction after multiple press drawing processes, when a stamping process is performed thereafter, distortion will occur not only in the bottom side portion of the bottomed container but also in the wall portion of the bottomed container, and further, dimensional abnormality will occur in the corner portions of the bottom of the bottomed container. Therefore, when a stamping process is further performed after press forming that involves multiple press drawing processes is performed, there is a problem that distortion on the bottom side of the workpiece will cause distortion in the wall portion of the bottomed container after stamping and dimensional abnormality in the corner portions of the bottom of the bottomed container.

[0008] The present invention has been made in consideration of the above-mentioned situation, and aims to provide a method for manufacturing a bottomed container, and a press system which can suppress the occurrence of distortion on the bottom side of a workpiece when manufacturing a bottomed angular cylindrical container by performing multiple press drawing processes using multiple dies having long hole-shaped forming holes to shape the workpiece from a flat state into a angular cylindrical state having a bottom. [Means for solving the problem]

[0009] (1) The method for producing a bottomed container of the present invention comprises the steps of: A method for manufacturing a bottomed container, comprising the steps of: forming a workpiece from a flat plate into a bottomed rectangular cylindrical container by performing a plurality of press drawing steps using a plurality of dies having elongated forming holes; a first press drawing process which is performed using a first die including a die having a first forming hole as the long hole-shaped forming hole, and which is configured as at least one of the press drawing processes excluding the final press drawing process among the multiple press drawing processes; A second press drawing process is performed using a second die having a second forming hole as the elongated forming hole, and is configured as a press drawing process subsequent to the first press drawing process among the multiple press drawing processes. The first molding hole is formed to have a larger dimension in a width direction, which is a direction perpendicular to a longitudinal direction, in which the first molding hole extends like a long hole, than the second molding hole over the entire length in a vertical direction, in which the first molding hole penetrates the die; The first molding hole is formed so as to narrow toward the inside in the width direction from both ends in the longitudinal direction to the center over the entire length in the up-down direction, It is characterized by:

[0010] According to the method for manufacturing a bottomed container described in (1) above, the first forming hole is formed so as to narrow from both ends in the longitudinal direction toward the center in the width direction within a range of a width dimension larger than the width dimension of the second forming hole. As a result, in the first press drawing process, a tensile force is generated in the circumferential direction of the first forming hole in the portion of the workpiece that is machined at the longitudinal center of the first forming hole. Therefore, in the workpiece, the circumferential tensile force generated in the portion of the workpiece that is machined at the longitudinal center of the first forming hole opposes the compressive force generated in the portion of the workpiece that is machined at both ends in the longitudinal direction of the first forming hole. As a result, the volume of the material machined at the longitudinal center of the first forming hole is prevented from becoming excessive, and plastic flow toward the bottom side of the workpiece is prevented. In addition, the first forming hole is formed so as to narrow toward the inside in the width direction from both ends in the longitudinal direction to the center, within a range of a width dimension larger than the width dimension of the second forming hole, over the entire length in the vertical direction. Therefore, the force acting on the workpiece at both ends and the center in the longitudinal direction of the first forming hole is adjusted throughout the entire process of the first press drawing process, and the volume of the material processed at the longitudinal center side of the first forming hole is suppressed from becoming excessive over the entire length in the vertical direction, and plastic flow toward the bottom side of the workpiece is suppressed. Then, in the second press drawing process, the workpiece in a state in which the volume is suppressed from becoming excessive at the longitudinal center side and plastic flow toward the bottom side is suppressed passes through the second forming hole, which has a smaller width dimension than the first forming hole, and is press drawn to be formed into a square tube shape or a state close to a square tube shape. Then, through the final press drawing process, the workpiece is finally formed into a square tube shape. Thus, according to the manufacturing method for bottomed containers described in (1) above, in the first press drawing process, the workpiece is press-formed while preventing excess volume at the center in the longitudinal direction and preventing plastic flow toward the bottom, and in the second press drawing process, the workpiece is pressed into a rectangular tube shape or a shape close to a rectangular tube by being drawn in the width direction. Therefore, according to the manufacturing method for bottomed containers described in (1) above, it is possible to prevent distortion from occurring on the bottom side of the central portion in the longitudinal direction of the workpiece.In the manufacturing method of the bottomed container described in (1) above, the circumferential tensile force generated in the part processed at the center in the longitudinal direction opposes the circumferential compressive force generated in the part processed at both ends in the longitudinal direction, so that buckling is less likely to occur in the part processed at the center in the longitudinal direction, and the occurrence of wrinkles can be suppressed. Note that the "width direction" is a direction perpendicular to the "longitudinal direction, which is the direction extending in the shape of an elongated hole," and is a direction perpendicular to both the "longitudinal direction" and the "up-down direction." Also, the "direction extending in the shape of an elongated hole" is synonymous with the "direction extending in the shape of an elongated hole."

[0011] As described above, according to the manufacturing method for bottomed containers described in (1) above, by performing multiple press drawing processes using multiple dies having long hole-shaped forming holes to shape the workpiece from a flat state into a rectangular tube shape having a bottom, it is possible to suppress the occurrence of distortion on the bottom side of the workpiece when manufacturing rectangular cylindrical bottomed containers.

[0012] (2) In the method for producing a bottomed container of the present invention, The first press drawing process is configured as a first press drawing process among the multiple press drawing processes. It is more preferable to do so.

[0013] In the first press drawing process in which a flat workpiece is subjected to press drawing, the compressive force generated in the portions machined at both longitudinal ends of the forming hole is also large. However, according to the manufacturing method for a bottomed container described in (2) above, in the first press drawing process, a circumferential tensile force can be generated in the portion machined at the longitudinal center of the forming hole so as to counter the circumferential compressive force generated in the portions machined at both longitudinal ends of the forming hole. Therefore, even in the first press drawing process in which distortion of the bottom side of the workpiece is likely to occur, it is possible to efficiently suppress the occurrence of distortion of the bottom side of the workpiece.

[0014] (3) In the method for producing a bottomed container of the present invention, The first molding hole is formed so as to be curved and narrowed toward the inside in the width direction from both ends in the longitudinal direction to the center, and is narrowed most toward the inside in the width direction at the center position in the longitudinal direction. It is more preferable to do so.

[0015] According to the method for manufacturing a bottomed container described in (3) above, a circumferential tensile force can be generated in the portion machined at the center in the longitudinal direction so as to more evenly oppose the circumferential compressive force generated in the portions machined at both longitudinal ends, thereby more efficiently suppressing the occurrence of distortion on the bottom side of the workpiece.

[0016] (4) The press system of the present invention is A press system for forming a rectangular cylindrical container with a bottom by performing a press drawing process multiple times using a plurality of dies having elongated forming holes to form a workpiece from a flat plate into a rectangular cylindrical shape having a bottom, a first press section that has a first die including a die having a first forming hole as the forming hole having a long hole shape, and that performs a first press drawing process using the first die, the first press drawing process being configured as at least one of the press drawing processes excluding a final press drawing process among the multiple press drawing processes; a second press section that has a second die having a second forming hole as the elongated forming hole, and that uses the second die to perform a second press drawing process that is configured as a press drawing process subsequent to the first press drawing process among the plurality of press drawing processes; The first molding hole is formed to have a larger dimension in a width direction, which is a direction perpendicular to a longitudinal direction, in which the first molding hole extends like a long hole, than the second molding hole over the entire length in a vertical direction, in which the first molding hole penetrates the die; The first molding hole is formed so as to narrow toward the inside in the width direction from both ends in the longitudinal direction to the center over the entire length in the up-down direction, It is characterized by:

[0017] According to the press system described in (4) above, the first forming hole provided in the first die of the first press section is formed so as to narrow toward the inside in the width direction from both ends in the longitudinal direction to the center, within a range of width dimensions larger than the width dimensions of the second forming hole provided in the second die of the second press section. As a result, when the first press drawing process is performed in the first press section, a tensile force is generated in the circumferential direction of the first forming hole in the portion of the workpiece that is processed at the longitudinal center of the first forming hole. Therefore, in the workpiece, the circumferential tensile force generated in the portion of the workpiece that is processed at the longitudinal center of the first forming hole opposes the compressive force generated in the portion of the workpiece that is processed at the longitudinal end of the first forming hole. As a result, the volume of the material processed at the longitudinal center of the first forming hole is prevented from becoming excessive, and plastic flow toward the bottom side of the workpiece is prevented. In addition, the first forming hole is formed so as to narrow toward the inside in the width direction from both ends in the longitudinal direction to the center, within a range of a width dimension larger than the width dimension of the second forming hole, over the entire length in the vertical direction. Therefore, the force acting on the workpiece at both ends and the center in the longitudinal direction of the first forming hole is adjusted throughout the entire process of the first press drawing process, and the volume of the material processed at the longitudinal center side of the first forming hole is suppressed from becoming excessive over the entire length in the vertical direction, and plastic flow toward the bottom side of the workpiece is suppressed. Then, when the second press drawing process is performed in the second press section, the workpiece in a state in which the volume is suppressed from becoming excessive at the longitudinal center side and the plastic flow toward the bottom side is suppressed passes through the second forming hole, which has a smaller width dimension than the first forming hole, and is pressed and drawn to be formed into a square tube shape or a state close to a square tube shape. Then, after the final press drawing process, the workpiece is finally formed into a square tube shape. In this way, according to the press system described in (4) above, in the first press drawing process performed on the workpiece in the first press section, excess volume at the center in the longitudinal direction is suppressed and plastic flow toward the bottom side is suppressed, thereby performing press forming, and in the second press drawing process performed in the second press section, the workpiece is pressed into a rectangular tube shape or a shape close to a rectangular tube shape by being squeezed in the width direction.Therefore, according to the press system described in (4) above, it is possible to suppress the occurrence of distortion on the bottom side of the central portion in the longitudinal direction of the workpiece. In addition, in the press system described in (4) above, the circumferential tensile force generated in the portion processed on the central side in the longitudinal direction opposes the circumferential compressive force generated in the portion processed on both ends in the longitudinal direction, so that buckling is less likely to occur in the portion processed on the central side in the longitudinal direction, and the occurrence of wrinkles can be suppressed. Note that the "width direction" is a direction perpendicular to the "longitudinal direction, which is the direction extending in the shape of a long hole," and is a direction perpendicular to both the "longitudinal direction" and the "up-down direction." Also, the "direction extending in the shape of a long hole" is synonymous with the "direction extending in the shape of a long hole."

[0018] As described above, according to the press system described in (4) above, by performing multiple press drawing processes using multiple dies having long hole-shaped forming holes, the workpiece is shaped from a flat plate into a rectangular tubular shape having a bottom, thereby making it possible to suppress distortion on the bottom side of the workpiece when forming a rectangular tubular bottomed container.

[0019] (5) In the press system of the present invention, The first press section performs the first press drawing process, which is configured as a first press drawing process among the multiple press drawing processes, using the first die. It is more preferable to do so.

[0020] In the first press drawing process in which a flat workpiece is subjected to press drawing, the compressive force generated in the portion machined at both ends in the longitudinal direction of the forming hole is also large. However, according to the press system described in (5) above, when the first press drawing process is performed in the first press section, a circumferential tensile force can be generated in the portion machined at the longitudinal center of the forming hole so as to oppose the circumferential compressive force generated in the portion machined at both ends in the longitudinal direction of the forming hole. Therefore, even in the first press drawing process in which distortion is likely to occur on the bottom side of the workpiece, it is possible to efficiently suppress the occurrence of distortion on the bottom side of the workpiece.

[0021] (6) In the press system of the present invention, The first molding hole is formed so as to be curved and narrowed toward the inside in the width direction from both ends in the longitudinal direction to the center, and is narrowed most toward the inside in the width direction at the center position in the longitudinal direction. It is more preferable to do so.

[0022] According to the press system described in (6) above, a circumferential tensile force can be generated in the portion machined at the center in the longitudinal direction so as to more evenly oppose the circumferential compressive force generated in the portions machined at both ends in the longitudinal direction, thereby more efficiently suppressing the occurrence of distortion on the bottom side of the workpiece. Effect of the Invention

[0023] According to the present invention, a method and press system for manufacturing a bottomed container can be provided which can suppress distortion on the bottom side of a workpiece when manufacturing a bottomed angular cylindrical container by performing multiple press drawing processes using multiple dies having long hole-shaped forming holes to shape the workpiece from a flat state into a angular cylindrical state having a bottom. [Brief description of the drawings]

[0024] [Figure 1] 1 is an example of a press system according to an embodiment of the present invention. [Diagram 2] FIG. 2 is a side cross-sectional view of a transfer press device in the press system, showing an enlarged portion of the transfer press device. [Diagram 3] 1 is a flowchart showing an example of a method for manufacturing a bottomed container according to the present embodiment, and is also a flowchart showing an example of a press drawing process performed multiple times in a press system. [Figure 4]FIG. 4 is a diagram showing an example of a first mold used in a first press drawing process in a method for manufacturing a bottomed container, and also a diagram showing an example of a first mold in a first press section of a press system, where FIG. 4(A) is a plan cross-sectional view of a punch in the first mold, FIG. 4(B) is a plan view of a die in the first mold, and FIG. 4(C) is a cross-sectional view taken along line AA in FIG. 4(B). [Diagram 5] FIG. 5 is a diagram showing an example of a second die used in a second press drawing process in a method for manufacturing a bottomed container, and also a diagram showing an example of a second die in a second press section of a press system, where FIG. 5(A) is a plan view of a punch in the second die, FIG. 5(B) is a plan view of a die in the second die, and FIG. 5(C) is a cross-sectional view taken along line BB in FIG. 5(B). [Figure 6] 1A to 1C are diagrams for explaining a method for manufacturing a bottomed container and a workpiece that is subjected to press drawing in a press system. [Figure 7] FIG. 1 is a schematic diagram showing, in comparison, the forming holes of the die used in the first press drawing process and the second press drawing process in the manufacturing method for a bottomed container, and also a schematic diagram showing, in comparison, the forming holes of the die used in the first press drawing process and the second press drawing process performed by the first press section and the second press section in the press system. [Figure 8] FIG. 2 is a diagram for explaining the forces acting on the workpiece in the first press drawing process in the manufacturing method for a bottomed container, and is also a diagram for explaining the forces acting on the workpiece in the first press drawing process performed by the first press section in the press system. [Figure 9] 9A and 9B are diagrams for explaining a conventional press drawing process, in which FIG. 9A is a plan view showing a die, FIG. 9B is a cross-sectional view showing a state in which drawing is being performed on a workpiece, and FIG. 9C is an enlarged view of part D surrounded by a dashed line in FIG. 9B. [Figure 10]10A and 10B are diagrams for explaining the first press drawing process in the manufacturing method for a bottomed container and the first press drawing process performed by the first press section of the press system, in which FIG. 10(A) is a plan view showing a die, FIG. 10(B) is a cross-sectional view showing the state in which drawing is being performed on the workpiece, and FIG. 10(C) is an enlarged view of part F surrounded by a dashed line in FIG. 10(B). [Figure 11] These are figures for explaining the external features of the manufactured bottomed containers, where Figure 11(A) is a figure for explaining the external features of a bottomed container manufactured by a conventional bottomed container manufacturing method, and Figure 11(B) is a figure for explaining the external features of a bottomed container manufactured by the bottomed container manufacturing method of this embodiment. [Figure 12] 13 is a flowchart showing a method for manufacturing a bottomed container according to a modified example, and is also a flowchart showing a plurality of press drawing steps performed in a press system according to the modified example. [Figure 13] FIG. 13A is a cross-sectional view of a punch and a plan view of a die in a die used in a first press drawing process in a method for manufacturing a bottomed container according to a modified example, and also a cross-sectional view of a die in a press system according to a modified example, where FIG. 13(A) is a cross-sectional view of a punch and a plan view of a die in a die used in a second press drawing process, and FIG. 13(C) is a cross-sectional view of a punch and a plan view of a die in a die used in a third press drawing process. [Figure 14] FIG. 1 is a schematic diagram showing, in comparison, the forming holes of a die used in multiple press drawing processes in a manufacturing method for a bottomed container according to a modified example, and is also a schematic diagram showing, in comparison, the forming holes of a die used in multiple press drawing processes performed in a press system according to a modified example. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0025] Hereinafter, the embodiment of the present invention will be described with reference to the drawings. The present invention can be widely applied to various applications as a method for manufacturing a bottomed container, which produces a bottomed container in a rectangular cylindrical shape by performing a press drawing process multiple times using a plurality of dies having elongated forming holes to form a work from a flat plate state to a rectangular cylindrical shape having a bottom. The present invention can also be widely applied to various applications as a press system for forming a bottomed container in a rectangular cylindrical shape by performing a press drawing process multiple times using a plurality of dies having elongated forming holes to form a work from a flat plate state to a rectangular cylindrical shape having a bottom. In the following description, first, a schematic configuration of the press system and the method for manufacturing a bottomed container according to the embodiment of the present invention will be described, and then, a characteristic configuration of the press system and the method for manufacturing a bottomed container according to the embodiment of the present invention will be described.

[0026] [1. Press system overview] Fig. 1 is an example of a press system 1 according to an embodiment of the present invention. Fig. 2 is a side cross-sectional view of a transfer press device 50 in the press system 1, and is an enlarged view of a portion of the transfer press device 50. For ease of explanation, the up-down direction, the left-right direction, and the front-rear direction are defined as shown in Figs. 1 and 2.

[0027] 1, the press system 1 includes a work supplying device 10 and a transfer press device 50. In this embodiment, the work supplying device 10 is disposed on the left side, and the transfer press device 50 is disposed on the right side. The work supplying device 10 supplies a work W to the transfer press device 50.

[0028] The work supplying device 10 is a device that supplies a work W (see Figs. 4 and 6(A) described later) to the transfer press device 50, and is disposed adjacent to the transfer press device 50 on the upstream side in the work transport direction. The work supplying device 10 includes a frame 12 that stands vertically and is composed of a pair of side walls 13A, 13B that face each other in the left-right direction. The frame 12 has a structure in which a ram support wall 14, a bolster support wall 16, etc. are inserted between the pair of side walls 13A, 13B. A drive unit 32 that drives a pair of rails 82A, 82B (see Fig. 2) is disposed on the left side of the work supplying device 10.

[0029] The ram support wall 14 supports the ram 20 so that it can move up and down, i.e., move up and down. The ram 20 receives power from a servo motor (not shown) through a camshaft 22, and can move up and down. The ram 20 also supports a punch (not shown). The left end of the camshaft 22 penetrates the left side wall 13A of the pair of side walls 13A, 13B arranged opposite to each other in the left-right direction and protrudes outward. The part protruding outward through the left side wall 13A is connected to the above-mentioned servo motor (not shown) via a pulley 24 and a timing belt (not shown). When the camshaft 22 is driven to rotate by the servo motor (not shown), the ram 20 reciprocates up and down. In addition, a flywheel 26 is attached to the left end of the camshaft 22 together with the pulley 24. The pulley 24, the timing belt (not shown), and the flywheel 26, as well as various other members, are covered by a side cover 28 fixed to the outer surface of the side wall 13A.

[0030] The bolster support wall 16 supports the die holder 30 via the bolster 18. The die holder 30 has a two-stage structure consisting of an upper stage and a lower stage. The upper surface of the lower stage of the die holder 30 is flush with the upper surface of a die holder 70 (described later) of the transfer press device 50. The upper stage of the die holder 30 is disposed above the upper surface of the lower stage with a gap therebetween. A die (not shown) is held in the upper stage of the die holder 30.

[0031] In the work supplying device 10, the ram 20 is moved downward to punch out sheet metal with a punch and a die (not shown) supported by the ram 20, thereby forming a flat plate-like workpiece W (see FIGS. 4 and 6(A) described below). The flat plate-like workpiece W formed by the work supplying device 10 is supplied to a transfer press device 50.

[0032] 1, the transfer press device 50 is disposed adjacent to the downstream side in the work transport direction of the work supply device 10. The work W in the form of a flat plate formed by the work supply device 10 is transported to the transfer press device 50, and the transfer press device 50 applies press drawing to the work W multiple times.

[0033] The transfer press device 50 includes a frame 52 that is configured with a pair of side walls 53A, 53B that stand vertically and face each other in the left-right direction. The frame 52 has a structure in which a ram support wall, a bolster support wall 56, and the like (not shown) are inserted between the pair of side walls 53A, 53B.

[0034] A ram support wall (not shown) supports the ram 60 so that it can move up and down, i.e., can move up and down. The ram 60 receives power from a servo motor (not shown) through a camshaft 62, and is capable of moving up and down. The ram 60 also supports a number of punches 74 arranged in the left-right direction (i.e., the work transfer direction). A camshaft 62 is inserted between the pair of side walls 53A, 53B above the ram support wall (not shown). The ram 60 engages with a cam 61 of the camshaft 62.

[0035] The right end of the camshaft 62 penetrates the right side wall 53B of the pair of side walls 53A, 53B arranged opposite to each other in the left-right direction and protrudes outward. The portion penetrating the right side wall 53B and protruding outward is connected to the above-mentioned servo motor (not shown) via a pulley 64 and a timing belt (not shown).

[0036] When the camshaft 62 is rotationally driven by a servo motor (not shown), the ram 60 moves up and down. A pulley 64 and a flywheel 66 are attached to the right end of the camshaft 62. The pulley 64, a timing belt (not shown), and various members including the flywheel 66 are covered by a side cover 68 fixed to the outer surface of the side wall 53B.

[0037] The bolster support wall 56 is disposed between the lower ends of the pair of side walls 53A, 53B, and has a bolster 58 fixed to its upper surface. A plurality of dies 72 (see FIGS. 1 and 2) are fixed to the upper surface of the bolster 58 via a plurality of die holders 70 arranged along the work transfer direction. The number of the plurality of dies 72 and the plurality of punches 74 is the same, and a pair of dies 72 and punches 74 arranged vertically constitutes a die used to perform one press drawing process. In other words, each of the multiple pairs of dies 72 and punches 74 arranged vertically constitutes a die used to perform multiple press drawing processes.

[0038] 1 and 2, the transfer press device 50 includes a plurality of pairs of dies 72 and punches 74, which are a plurality of dies arranged along the work transport direction. The plurality of pairs of dies 72 and punches 74 are arranged at a constant pitch in the left-right direction. With reference to FIG. 2, each die 72 is fixed to a die holder 70. A step portion 70A is formed in the upper portion of the die holder 70. The die 72 is fixed to the step portion 70A of the die holder 70. With the die 72 fixed to the step portion 70A, the upper surface of the die holder 70 and the upper surface of the die 72 are flush with each other. The die 72 is provided with a forming hole 73 formed in an elongated hole shape in a plan view viewed in the vertical direction. The press drawing process is performed by pushing the work W into the elongated forming hole 73 in the die 72 and passing it through the punch 74. When the punch 74 pushes the workpiece W into the elongated forming hole 73 of the die 72, the workpiece W is formed into a cylindrical shape having an elongated cross-sectional shape. A knockout pin 94 is disposed below the forming hole 73 of the die 72. When the punch 74 pushes the workpiece W into the forming hole 73 of the die 72 to form it, the knockout pin 94 presses the bottom surface of the workpiece W upward, thereby restricting the downward bulging of the workpiece W. When the punch 74 rises, the workpiece W can be pushed upward from the forming hole 73 of the die 72.

[0039] The workpiece W is transported downstream in the workpiece transport direction by a transfer device 80. The workpiece W is transported downstream in the workpiece transport direction by the transfer device 80, and press drawing is performed by each of the multiple pairs of dies 72 and punches 74 arranged in the left-right direction.

[0040] 1 and 2, the transfer device 80 is arranged on the die holder 70, and includes a pair of rails 82A, 82B, multiple pairs of fingers 84A, 84B, multiple pairs of air cylinders 86A, 86B as driving sources for driving each of the multiple pairs of fingers 84A, 84B, and a drive unit 32 (see FIG. 1) that operates the pair of rails 82A, 82B in the left-right direction.

[0041] The pair of rails 82A, 82B are arranged horizontally so that the left-right direction is the longitudinal direction, and are arranged to extend across the multiple pairs of dies 72 and punches 74. The pair of rails 82A, 82B are arranged in parallel with a certain distance in the front-rear direction. A pair of fingers 84A, 84B and a pair of air cylinders 86A, 86B are placed on the pair of rails 82A, 82B at positions corresponding to each pair of dies 72 and punches 74 in the up-down direction. Therefore, when the pair of rails 82A, 82B are moved in the left-right direction by the driving unit 32 (see FIG. 1), the multiple air cylinders 86A, 86B and the multiple fingers 84A, 84B also move in the left-right direction. In this way, the workpiece W clamped by the fingers 84A, 84B can be transported downstream in the workpiece transport direction. Note that FIG. 2 shows a state in which the workpiece W is clamped by the fingers 84A, 84B.

[0042] As shown in FIG. 2, the fingers 84A and 84B are provided at the tip of the rods of the air cylinders 86A and 86B, respectively, and are configured to be opened and closed by the operation of the air cylinders 86A and 86B. The air cylinders 86A and 86B are operated symmetrically in the front-rear direction, with the front air cylinder 86A and the rear air cylinder 86B. That is, when the air cylinder 86A operates from the front to the rear direction, the air cylinder 86B operates from the rear to the front direction. At this time, the fingers 84A and 84B operate in a direction toward each other, that is, from open to closed. Also, when the air cylinder 86A operates from the rear to the front direction, the air cylinder 86B operates from the front to the rear direction. At this time, the fingers 84A and 84B operate in a direction away from each other, that is, from closed to open. By opening and closing the fingers 84A and 84B in this way, the workpiece W can be released or clamped.

[0043] The interval between the fingers 84A, 84B adjacent to each other in the work transport direction (i.e., the left-right direction) is the same constant pitch as the interval between the punch 74 (see FIG. 1) and the die 72 adjacent to each other in the left-right direction. The drive unit (see FIG. 1) repeats reciprocating motion of the pair of rails 82A, 82B in the left-right direction at a constant pitch while keeping the pair horizontal in synchronization with the lifting and lowering motion of the ram 60 (see FIG. 1). In addition, the multiple pairs of air cylinders 86A, 86B repeatedly perform opening and closing motions of the fingers 84A, 84B so that the work W is transported by the reciprocating motion of the pair of rails 82A, 82B in the left-right direction. In this way, the work W is transported by the transfer device 80 from the upstream side (i.e., the left side) in the work transport direction to the downstream side (i.e., the right side) in the work transport direction, and the press drawing is performed by each of the multiple pairs of dies 72 and punches 74 in order. As a result, the press drawing process is performed multiple times on the work W.

[0044] When the press system 1 performs a plurality of press drawing processes on the workpiece W, the number of dies 72 and punches 74 corresponding to the number of press drawing processes to be performed is used. The press system 1 illustrated in FIG. 1 illustrates a form in which eight pairs of dies 72 and punches 74 are provided. When eight press drawing processes are performed on the workpiece W, eight pairs of dies 72 and punches 74 are used. For example, when two press drawing processes are performed on the workpiece W, only two pairs of dies 72 and punches 74 are used. That is, in this case, in the press system 1, only any two pairs of dies 72 and punches 74 out of the eight pairs of dies 72 and punches 74 are attached and used, and the other six pairs of dies 72 and punches 74 are not attached to the press system 1. Similarly, for example, when the press drawing process is performed three times on the workpiece W, only three pairs of dies 72 and punches 74 are used. In this case, only three pairs of dies 72 and punches 74 out of the three pairs of dies 72 and punches 74 are attached and used in the press system 1, and the other five pairs of dies 72 and punches 74 are not attached to the press system 1. In addition, in the places in the press system 1 where the dies 72 are not attached, for example, block-shaped members without molding holes are attached.

[0045] The press system 1 of this embodiment has the above-mentioned configuration as a basic device configuration, and is provided as a press system that performs a plurality of press drawing steps using a plurality of dies having elongated forming holes to form a workpiece W from a flat state into a rectangular cylindrical state having a bottom, thereby forming a rectangular cylindrical bottomed container. Each of the plurality of dies used in the plurality of press drawing steps performed by the press system 1 is composed of a die 72 and a punch 74. The die 72 in each of the plurality of dies is provided with an elongated forming hole 73.

[0046] As the multiple press drawing steps performed by the press system 1, two press drawing steps may be performed, or three or more press drawing steps may be performed. FIG. 3 is a flowchart showing an example of the multiple press drawing steps performed by the press system 1. FIG. 3 is also a flowchart showing an example of a method for manufacturing a bottomed container according to the present embodiment, which will be described later. The flowchart shown in FIG. 3 illustrates an embodiment in which the press system 1 performs two press drawing steps as the multiple press drawing steps. As illustrated in the flowchart of FIG. 3, the press system 1 is configured to perform a first press drawing step S1 and a second press drawing step S2. In the example shown in FIG. 3, the first press drawing step constitutes the first press drawing step S1, and the second and final press drawing step constitutes the second press drawing step S2. 3, when two press drawing processes are performed as multiple press drawing processes in the press system 1, only two pairs of dies 72 and punches 74 out of the eight pairs of dies 72 and punches 74 are attached and used, and the other six pairs of dies 72 and punches 74 are not attached to the press system 1. In other words, when two press drawing processes are performed in the press system 1, the press system 1 has only two pairs of dies 72 and punches 74 lined up in the work transfer direction, and is equipped with two molds composed of the dies 72 and punches 74.

[0047] The press system 1 includes a first press section that performs a first press drawing process S1, and a second press section that performs a second press process S2.

[0048] The first press section is configured to perform a first press drawing process S1, which is configured as at least one of the press drawing processes excluding the final press drawing process among the multiple press drawing processes. As illustrated in the flowchart of FIG. 3, when two press drawing processes are performed as the multiple press drawing processes in the press system 1, the first press drawing process S1 performed in the first press section is configured as the first press drawing process excluding the final second press drawing process. And, the first press drawing process S1 performed by the first press section is configured as the first press drawing process among the multiple press drawing processes. When two press drawing processes are performed in the press system 1, the first press section is configured to include a die arranged upstream in the work transport direction of two dies having a die 72 and a punch 74. The first press section is configured to include a die on the upstream side in the workpiece conveying direction, which is composed of a pair of die 72 and punch 74, a die holder 70 and bolster 58 that support the die 72, a ram 60 that supports the punch 74, and a servo motor and camshaft 62 as a mechanism for raising and lowering the ram 60. As will be described later, the first press section has a first die 71A (see FIG. 4) including a die 72A having a first forming hole 73A as an elongated forming hole 73.

[0049] The second press section is configured to perform a second press drawing process S2 configured as a press drawing process subsequent to the first press drawing process S1 among the multiple press drawing processes. As illustrated in the flowchart of FIG. 3, when two press drawing processes are performed as multiple press drawing processes in the press system 1, the second press drawing process S2 performed in the second press section is configured as a final press drawing process that is a press drawing process subsequent to the first press drawing process S1 as the first press drawing process. When two press drawing processes are performed in the press system 1, the second press section is configured to include a die disposed downstream in the work transport direction of one of two dies having a die 72 and a punch 74. The second press section is configured to include a die downstream in the work transport direction, which is configured of a pair of a die 72 and a punch 74, a die holder 70 and a bolster 58 that support the die 72, a ram 60 that supports the punch 74, and a servo motor and a camshaft 62 as a mechanism for raising and lowering the ram 60. As will be described later, the second press section has a second mold 71B (see FIG. 5) including a die 72B having a second molding hole 73B as an elongated molding hole 73.

[0050] [2. Overview of manufacturing method for bottomed containers] Next, a method for manufacturing a bottomed container according to an embodiment of the present invention will be described. The method for manufacturing a bottomed container according to this embodiment is a method for manufacturing a bottomed container in which a work W is formed from a flat plate into a square tube having a bottom by performing a press drawing process multiple times using a plurality of dies having elongated forming holes, thereby manufacturing a square tube-shaped bottomed container. The method for manufacturing a bottomed container according to this embodiment is implemented, for example, by performing a press drawing process multiple times on the work W using a press system 1. Therefore, the method for manufacturing a bottomed container according to this embodiment is configured as a method for manufacturing a bottomed container in which a square tube-shaped bottomed container is manufactured by performing a press drawing process multiple times on the work W using a plurality of dies having elongated forming holes 73, which are configured including a die 72 and a punch 74, to form the work W from a flat plate into a square tube.

[0051] The manufacturing method of the bottomed container of this embodiment is configured to include a plurality of press drawing steps. The manufacturing method of the bottomed container of this embodiment may be configured to include two press drawing steps as the plurality of press drawing steps, or may be configured to include three or more press drawing steps. FIG. 3 is a flow chart showing an example of the manufacturing method of the bottomed container of this embodiment. In this embodiment, as shown in FIG. 3, the manufacturing method of the bottomed container of this embodiment is illustrated as including a plurality of press drawing steps and a punching step performed after the plurality of press drawing steps. The manufacturing method of the bottomed container of this embodiment shown in FIG. 3 is configured to include a first press drawing step S1 and a second press drawing step S2. The manufacturing method of the bottomed container illustrated in FIG. 3 is configured to include two press drawing steps, with the first press drawing step constituting the first press drawing step S1 and the second and final press drawing step constituting the second press drawing step S2.

[0052] As shown in FIG. 3, after the first press drawing process S1 and the second press drawing process S2 are completed, a punching process S3 may be performed. The punching process S3 is performed on the rectangular cylindrical bottomed container that is manufactured by performing multiple press drawing processes after multiple press drawing processes are completed. In the punching process S3, a punching mold is used to perform punching on the manufactured rectangular cylindrical bottomed container, which punches the plate thickness of the wall of the bottomed container to reduce the thickness and determine the final shape of the product. If the punching process S3 is not performed after multiple press drawing processes, the shape of the bottomed container manufactured through multiple press drawing processes will determine the final shape of the product.

[0053] The first drawing process step S1 is configured as at least one of the multiple drawing processes excluding the final drawing process step. Since the method for manufacturing a bottomed container shown in Fig. 3 is configured as a method for manufacturing a bottomed container by performing two drawing processes, the first drawing process step S1 is configured as the first drawing process step excluding the second drawing process step which is the final step. In the method for manufacturing a bottomed container shown in Fig. 3, the first drawing process step S1 is configured as the first drawing process step of the multiple drawing processes.

[0054] The second drawing process S2 is configured as a drawing process subsequent to the first drawing process S1 among multiple drawing processes. The method for manufacturing a bottomed container shown in FIG. 3 is configured as a method for manufacturing a bottomed container by performing two drawing processes, so the second drawing process S2 is configured as a final drawing process that is a drawing process subsequent to the first drawing process S1 as the initial drawing process. The method for manufacturing a bottomed container of this embodiment ends when the first drawing process S1 and the second drawing process S2 are performed. As shown in FIG. 3, after multiple drawing processes are completed, a punching process S3 may be performed to reduce the plate thickness of the wall of the bottomed container by punching.

[0055] [3. Characteristic configurations of the first and second press drawing processes and the first and second press sections] Next, a description will be given of the first and second press drawing steps of the manufacturing method for a bottomed container of this embodiment, and the characteristic configuration of the first and second press sections of the press system 1 of this embodiment. Fig. 4 is a diagram showing an example of a first die 71A used in the first press drawing step S1 in the manufacturing method for a bottomed container shown in Fig. 3, and also a diagram showing an example of the first die 71A in the first press section of the press system 1, Fig. 4(A) is a plan sectional view of a punch 74A of the first die 71A, Fig. 4(B) is a plan view of a die 72A of the first die 71A, and Fig. 4(C) is a sectional view taken along line AA of Fig. 4(B). Fig. 5 is a diagram showing an example of a second die 71B used in the second press drawing process S2 in the manufacturing method for a bottomed container shown in Fig. 3, and is also a diagram showing an example of the second die 71B in the second press section of the press system 1, Fig. 5(A) is a plan sectional view of a punch 74B of the second die 71B, Fig. 5(B) is a plan view of a die 72B of the second die 71B, and Fig. 5(C) is a sectional view taken along line BB in Fig. 5(B). Fig. 6 is a diagram for explaining the manufacturing method for a bottomed container of this embodiment and the workpiece W to which the press drawing process is performed in the press system 1.

[0056] 4, the first mold 71A in the first press section of the press system 1 and used in the first press drawing process S1 of the manufacturing method of the bottomed container of this embodiment is configured to include a die 72A and a punch 74A. The die 72A is provided as one of a plurality of dies 72 attached to the press system 1. The die 72A is configured as the die 72 of the first mold 71A of the first press section of the press system 1, and is configured as the die 72 used in the first press drawing process S1 of the manufacturing method of the bottomed container of this embodiment. The punch 74A is provided as one of a plurality of punches 74 attached to the press system 1. The punch 74A is configured as the punch 74 of the first mold 71A of the first press section of the press system 1, and is configured as the punch 74 used in the first press drawing process S1 of the manufacturing method of the bottomed container of this embodiment.

[0057] 4(B) and 4(C), the die 72A is provided with a first molding hole 73A as a molding hole 73 of the die 72, which is an elongated hole in a plan view in the vertical direction. The first molding hole 73A is provided so as to penetrate the die 72A in the vertical direction with a cross-sectional shape of an elongated hole. The first molding hole 73A is formed so that the dimension in the longitudinal direction X, which is the direction in which the first molding hole 73A extends in the elongated hole shape, is larger than the dimension in the width direction Y, which is the direction perpendicular to the longitudinal direction X. In FIG. 4(B), the longitudinal direction X is indicated by a double-ended arrow X, and the width direction Y is indicated by a double-ended arrow Y.

[0058] The first molding hole 73A is formed, for example, in such a way that both ends in the longitudinal direction X are each formed in a semicircular arc shape. The first molding hole 73A is formed such that the shape of the portion in the circumferential direction excluding both ends in the longitudinal direction X narrows toward the inside in the width direction Y from both ends in the longitudinal direction X to the center. That is, the first molding hole 73A is formed such that the shape of the portion in the circumferential direction excluding both ends in the longitudinal direction X gradually decreases in the dimension in the width direction Y from both ends in the longitudinal direction X to the center. The first molding hole 73A is formed such that the shape of the portion in the circumferential direction excluding both ends in the longitudinal direction X narrows toward the inside in the width direction Y from both ends in the longitudinal direction X to the center over the entire length in the up-down direction, which is the direction in which the first molding hole 73A penetrates the die 72A. The first molding hole 73 is formed so as to narrow inward in the width direction Y while smoothly curving in an arc from both ends in the longitudinal direction X to the center, and is narrowest on the inside in the width direction Y at a central position CX in the longitudinal direction X. In Fig. 4(B), the central position CX in the longitudinal direction X of the first molding hole 73A of the die 72A is indicated by a dashed line CX.

[0059] 4(A), the punch 74A is formed in a shape corresponding to the first forming hole 73A of the die 72A. That is, the outer peripheral shape of the punch 74A is formed in a shape corresponding to the first forming hole 73A of the die 72A. For this reason, the punch 74A is formed so that both ends in a direction parallel to the longitudinal direction X of the first forming hole 73A each have a semicircular cross-sectional shape. The punch 74A is formed so that the shape of the part other than both ends of the semicircular cross-sectional shape in the circumferential direction is smoothly curved and concave in an arc shape toward the inside in a direction parallel to the width direction Y of the first forming hole 73A from both ends in a direction parallel to the longitudinal direction X of the first forming hole 73A to the center.

[0060] The first press section of the press system 1 has a first die 71A including a die 72A having a first forming hole 73A as a long hole-shaped forming hole 73, and the first press drawing process S1 is performed using the first die 71A. The first press drawing process S1 in the manufacturing method for a bottomed container of this embodiment is performed using the first die 71A including the die 72A having the first forming hole 73A as a long hole-shaped forming hole 73. The first press drawing process S1 is performed using the die 72A provided with the first forming hole 73A, which is long and smoothly narrowed inward in the width direction Y toward the center side in the longitudinal direction X, and the punch 74A having a cross-sectional shape corresponding to the first forming hole 73A. In the first press drawing process S1, the workpiece W1 as the workpiece W in a plate state supplied from the workpiece supply device 10 of the press system 1 is subjected to press drawing using the die 72A and the punch 74A. In addition, in FIG. 6(A), a workpiece W1 is shown in a perspective view as the workpiece W in a flat plate state, and in FIGS. 4(B) and 4(C), the workpiece W1 is shown by a two-dot chain line.

[0061] In the first press drawing process S1 in the manufacturing method of the bottomed container of this embodiment and the first press section of the press system 1, the punch 74A presses the workpiece W1 into the first forming hole 73A of the die 72A, and the workpiece W1 is formed into a workpiece W2 having a cylindrical shape with a bottom. In FIG. 6(B), the workpiece W2 formed through the first press drawing process S1 is shown in a perspective view. The workpiece W2 has a bottom and is formed into a cylindrical shape with a cross-sectional shape corresponding to the shape of the first forming hole 73A. In FIG. 6(B), the upper end of the workpiece W2 is shown in a flat state.

[0062] 5, the second mold 71B in the second press section of the press system 1 and used in the second press drawing process S2 of the manufacturing method for a bottomed container of this embodiment includes a die 72B and a punch 74B. The die 72B is provided as one of the multiple dies 72 attached to the press system 1. The die 72B is configured as the die 72 of the second mold 71B of the second press section of the press system 1, and is configured as the die 72 used in the second press drawing process S2 of the manufacturing method for a bottomed container of this embodiment. The punch 74B is provided as one of the multiple punches 74 attached to the press system 1. The punch 74B is configured as the punch 74 of the second mold 71B of the second press section of the press system 1, and is configured as the punch 74 used in the second press drawing process S2 of the manufacturing method for a bottomed container of this embodiment.

[0063] 5(B) and 5(C), the die 72B is provided with a second molding hole 73B as the elongated molding hole 73 of the die 72. That is, the die 72B is provided with the second molding hole 73B as the molding hole 73 formed in an elongated shape in a plan view viewed in the vertical direction. The second molding hole 73B is provided so as to penetrate the die 72B in the vertical direction with an elongated cross-sectional shape. The second molding hole 73B is formed so that the dimension in the longitudinal direction X, which is the direction in which the second molding hole 73B extends in the elongated shape, is larger than the dimension in the width direction Y, which is the direction perpendicular to the longitudinal direction X. In FIG. 5(B), the longitudinal direction X is indicated by a double-ended arrow X, and the width direction Y is indicated by a double-ended arrow Y.

[0064] The second forming hole 73B is formed in a generally rectangular shape that is elongated in the longitudinal direction X. More specifically, the second forming hole 73B is formed in a rectangular shape with the four corners of the rectangle being formed into an arc shape. In this embodiment, the second press drawing process S2 constitutes the final press drawing process. Therefore, the shape of the second forming hole 73B corresponds to the cross-sectional shape of the rectangular cylindrical bottomed container that is finally manufactured through multiple press drawing processes in the manufacturing method for a bottomed container of this embodiment.

[0065] 5(A), punch 74B is formed into a shape corresponding to die 72B. That is, the outer peripheral shape of punch 74B is formed into a shape corresponding to second forming hole 73B of die 72B. Therefore, punch 74B is formed into a substantially rectangular cross-sectional shape that is elongated in a direction parallel to the longitudinal direction X of second forming hole 73B.

[0066] The second press section of the press system 1 has a second mold 71B including a die 72B having a second forming hole 73B as a long hole-shaped forming hole 73, and the second press drawing process S2 is performed using the second mold 71B. The second press drawing process S2 in the manufacturing method of the bottomed container of this embodiment is performed using a second mold 71B including a die 72B having a second forming hole 73B as a long hole-shaped forming hole 73 having a substantially rectangular shape. The second press drawing process S2 is performed using a die 72B provided with a second forming hole 73B having a substantially rectangular long hole shape and a punch 74B having a cross-sectional shape corresponding to the second forming hole 73B. In the second press drawing process S2, the cylindrical workpiece W2 formed through the first press drawing process S1 is subjected to press drawing using the die 72B and the punch 74B. In addition, in FIG. 5(B) and FIG. 5(C), the workpiece W2 is indicated by a two-dot chain line.

[0067] In the second press drawing process S2 in the manufacturing method of the bottomed container of this embodiment and the second press section of the press system 1, the punch 74B pushes the work W2 into the second forming hole 73B of the die 72B, so that the work W2 is formed into the work W3, which is a bottomed container in the shape of a square tube having a bottom. By performing the second press drawing process S2, a bottomed container in the shape of a square tube is manufactured as the work W3 in the shape of a square tube. In FIG. 6(C), a perspective view of the bottomed container in the shape of a square tube manufactured by being formed as the work W3 through the second press drawing process S2 is shown. In FIG. 6(C), the upper end of the work W3 is shown in a schematic flat state. In this embodiment, the second press drawing process S2 constitutes the final press drawing process. Therefore, the workpiece W3 formed through the second drawing process S2 is formed into the shape of a bottomed container manufactured through multiple drawing processes in the manufacturing method for a bottomed container of this embodiment, and constitutes a bottomed, rectangular tubular container having a bottom manufactured by the manufacturing method for a bottomed container of this embodiment. In the following description, the bottomed, rectangular tubular container having a bottom formed and manufactured as the workpiece W3 by carrying out the second drawing process S2 will also be referred to as the bottomed container W3.

[0068] Here, the relationship between the shapes of the forming hole 73 of the die 72 in the first drawing process S1 and the second drawing process S2 will be further described. Note that the following description of the relationship between the shapes of the forming hole 73 of the die 72 is a description of the relationship between the shapes of the forming hole 73 of the die 72 in the first drawing process S1 and the second drawing process S2 in the manufacturing method for a bottomed container of this embodiment, and also serves as a description of the relationship between the shapes of the forming hole 73 of the die 72 in the first press section that performs the first drawing process S1 and the second press section that performs the second drawing process S2 in the press system 1. 7 is a diagram showing a comparison of the forming holes 73 of the die 72 used in the first press drawing process S1 and the second press drawing process S2 in the manufacturing method for a bottomed container of this embodiment, and is also a diagram showing a comparison of the forming holes 73 of the die 72 used in the first press drawing process S1 and the second press drawing process S2 performed by the first press section and the second press section in the press system 1. That is, in FIG. 7, the first forming hole 73A of the die 72A used in the first press drawing process S1 and the second forming hole 73B of the die 72B used in the second press drawing process S2 are shown in comparison, and the first forming hole 73A of the die 72A of the first press section in the press system 1 and the second forming hole 73B of the die 72B of the second press section are shown in comparison. Naturally, die 72A and die 72B are not a single die 72 but separate, different dies 72. However, in FIG. 7, die 72A and die 72B are shown in a stacked state in order to contrast first forming hole 73A and second forming hole 73B.

[0069] 7, the area of ​​the first forming hole 73A is larger than the area of ​​the second forming hole 73B over the entire circumference of the area. That is, when the die 72A and the die 72B are overlapped, the outline of the first forming hole 73A and the outline of the second forming hole 73B do not overlap in a plan view, and the second forming hole 73B is disposed inside the first forming hole 73A. Therefore, the first forming hole 73A is formed to have a larger dimension in the width direction Y perpendicular to the longitudinal direction X over the longitudinal direction X, which is the direction in which the first forming hole 73A extends like an elongated hole, than the second forming hole 73B. Furthermore, the first forming hole 73A is formed to have a larger dimension in the width direction Y over the entire length in the vertical direction, which is the direction in which the first forming hole 73A penetrates the die 72A, than the second forming hole 73B. More specifically, the second forming hole 73B has a substantially rectangular shape, and the width dimension YB of the second forming hole 73B in the width direction Y is set to a constant dimension. The width dimension YB of the second forming hole 73B is set to a constant dimension over the entire length in the up-down direction, which is the direction in which the second forming hole 73B penetrates the die 72B. On the other hand, the semicircular arc-shaped portions at both ends in the longitudinal direction X of the first forming hole 73A are formed to a size that surrounds both ends in the longitudinal direction of the second forming hole 73B on the outside over the entire length in the up-down direction. Furthermore, the first forming hole 73A is formed so that the dimension in the width direction Y gradually decreases from both ends in the longitudinal direction X to the center over the entire length in the up-down direction in the portion other than both ends in the longitudinal direction X in the circumferential direction, and has the smallest width dimension YA at the center position CX in the longitudinal direction X. The width dimension YA of the first molding hole 73A at a portion other than both ends in the longitudinal direction X that has the smallest dimension in the width direction Y is larger than the width dimension YB of the second molding hole 73B. Therefore, the first molding hole 73A is formed to have a larger dimension in the width direction Y perpendicular to the longitudinal direction X, which is the direction in which the first molding hole 73A extends like an elongated hole, over the entire length in the up-down direction than the second molding hole 73B.

[0070] (Function of the first press drawing process and the first press section) Next, a description will be given of the operation of the first drawing process S1 in the manufacturing method for a bottomed container of this embodiment and the operation of the first press unit that performs the first drawing process S1 in the press system 1. The following description of the operation is intended to describe the operation of the first drawing process S1 in the manufacturing method for a bottomed container of this embodiment, and also to describe the operation of the first press unit that performs the first drawing process S1 in the press system 1. Fig. 8 is a diagram for explaining the force acting on the workpiece W in the first drawing process S1 in the manufacturing method for a bottomed container of this embodiment, and is also intended to explain the force acting on the workpiece W in the first drawing process S1 performed by the first press unit in the press system 1. 8 typically shows the workpiece W1 in the middle of being subjected to press drawing by the die 72A and punch 74A in the first press drawing step S1 in the manufacturing method for a bottomed container of this embodiment, and typically shows the workpiece W1 in the middle of being subjected to press drawing by the die 72A and punch 74A of the first press unit in the press system 1. Also, in FIG. 8, the die 72A and punch 74A are omitted, and the first forming hole 73A is typically shown by a two-dot chain line.

[0071] Referring to FIG. 8, when the first press drawing process S1 is started, the workpiece W1 placed on the die 72A is pressed into the first forming hole 73A by the punch 74A. When the workpiece W1 is pressed into the first forming hole 73A, a compressive force is generated in the circumferential direction of the first forming hole 73A in the part of the workpiece W1 that is machined in the semicircular arc-shaped region on both ends of the longitudinal direction X of the first forming hole 73A. In FIG. 8 and FIG. 10(A) described later, the part of the workpiece W1 that is machined on both ends of the longitudinal direction X of the first forming hole 73A is indicated by a dashed line with arrows P1 at both ends, and hereinafter, this part is also referred to as the "both end side processed part P1". The both end side processed parts P1 of the workpiece W1 are in a state of shrink flange forming, so that a compressive force is generated in the circumferential direction.

[0072] On the other hand, when the workpiece W1 is pressed into the first forming hole 73A, a tensile force is generated in the circumferential direction of the first forming hole 73A in the portion of the workpiece W1 that is machined in the central region other than both ends in the longitudinal direction X of the first forming hole 73A. In FIG. 8 and FIG. 10(A) described later, the portion of the workpiece W1 that is machined in the central region other than both ends in the longitudinal direction X of the first forming hole 73A is indicated by a dashed line with arrows P2 at both ends, and hereinafter, this portion is also referred to as the "central processed portion P2." The central processed portion P2 of the workpiece W1 is in a stretch flange forming state, so that a tensile force is generated in the circumferential direction.

[0073] As described above, in the first press drawing process S1, in the workpiece W1, a compressive force is generated in the circumferential direction in the both end processed parts P1, and a tensile force is generated in the circumferential direction in the central processed part P2. Therefore, in the workpiece W1, the tensile force in the circumferential direction generated in the central processed part P2 opposes the compressive force in the both end processed parts P1. Then, in the workpiece W1, plastic flow occurs smoothly from the both end processed parts P1 side where the compressive force is generated to the central processed part P2 side where the tensile force is generated, and the workpiece W1 is pressed between the die 72A and the punch 74A, and the workpiece W1 is formed into the shape of the workpiece W2. In addition, in the first press drawing process S1, plastic flow occurs smoothly from the both end processed parts P1 side where the compressive force is generated to the central processed part P2 side where the tensile force is generated, so that the volume of the material in the central processed part P2 is prevented from becoming excessive, and plastic flow to the bottom side of the part formed into the shape of the workpiece W2 is prevented. As a result, when the workpiece W1 is formed into the workpiece W2 through the first press drawing process S1, the occurrence of distortion on the bottom side of the workpiece W2 in the central portion in the longitudinal direction X is suppressed.

[0074] Here, the effect of suppressing the occurrence of distortion of the bottom of the workpiece W2 formed through the first press drawing process S1 will be further described in comparison with the conventional press drawing process. Fig. 9 is a diagram for explaining the conventional press drawing process, in which Fig. 9(A) is a plan view showing a die 172A, Fig. 9(B) is a cross-sectional view showing a state in which the workpiece W101 is drawn to form the workpiece W102, and Fig. 9(C) is an enlarged view of part D surrounded by a dashed line in Fig. 9(B). The conventional press drawing process described with reference to Fig. 9 constitutes the first press drawing process in a conventional method for manufacturing a bottomed container, which produces a square cylindrical bottomed container by performing a plurality of press drawing processes from the workpiece W101 in a flat plate state.

[0075] Referring to FIG. 9, the conventional press drawing process is performed using a die 172A provided with a long hole-shaped forming hole 173A and a punch 174A corresponding to the die 172A. The forming hole 173A of the die 172A is formed so that the dimension in the longitudinal direction X, which is the direction in which the forming hole 173A extends like a long hole, is larger than the dimension in the width direction Y, which is the direction perpendicular to the longitudinal direction X. In FIG. 9(A), the longitudinal direction X is indicated by a double-ended arrow X, and the width direction Y is indicated by a double-ended arrow Y. The forming hole 173A of the die 172A is formed in a shape that spreads outwardly in an elliptical shape over the entire circumference. The punch 174A is formed in a shape that corresponds to the forming hole 173A of the die 172A. That is, the outer peripheral shape of the punch 174A is formed in a shape that spreads outwardly in an elliptical shape over the entire circumference, similar to the shape of the forming hole of the die 172A.

[0076] In a conventional press drawing process, a flat workpiece W101 is subjected to press drawing using a die 172A and a punch 174A. In Fig. 9(A) and Fig. 9(B), the workpiece W101 is shown by a two-dot chain line. In the conventional press drawing process, the punch 174A presses the workpiece W101 into the forming hole 173A of the die 172A, and the workpiece W101 is formed into a cylindrical workpiece W102 having a bottom (see Fig. 9(B)). When the workpiece W101 is pressed into the forming hole 173A, a circumferential compressive force is generated in the workpiece W101 over the entire circumference in the circumferential direction. That is, in the conventional press drawing process, the workpiece 101 is formed with the forming hole 173A that spreads outward in an elliptical shape around the entire circumference, so that compressive force is generated not only in the portion of the workpiece W101 that is machined at both ends of the longitudinal direction X of the forming hole 173A, but also in the portion of the workpiece W101 that is machined in the central region of the longitudinal direction X of the forming hole 173A. In FIG. 9(A), the portion of the workpiece W101 that is machined at both ends of the longitudinal direction X of the forming hole 173A is indicated by a dashed line with double-ended arrow P10, and hereinafter, this portion is also referred to as the "both end side machined portion P10". In addition, the portion of the workpiece W101 that is machined in the central region of the forming hole 173A is indicated by a dashed line with double-ended arrow P20, and hereinafter, this portion is also referred to as the "central side machined portion P20".

[0077] In the conventional press drawing process, a circumferential compressive force is generated around the entire circumference of the forming hole 173A in the workpiece W101, and a circumferential compressive force is generated in both the end side processed portion P10 and the center side processed portion P20. However, the long hole-shaped forming hole 173A that spreads outward in an elliptical shape around the entire circumference has a larger curvature at both ends in the longitudinal direction X than at the center side portion in the longitudinal direction X, so that the processing amount of the end side processed portion P10 is larger than the processing amount of the center side processed portion P20. Therefore, plastic flow occurs from the end side processed portion P10 to the center side processed portion P20, and the volume of the material of the center side processed portion P20 becomes excessive. Therefore, the material of the center side processed portion P20 with an excessive volume plastically flows toward the bottom side of the workpiece W102 that is not restrained by the die 172A and the punch 174A. As a result, as shown in Figures 9(B) and 9(C), in the conventional press drawing process, a part of the central portion in the longitudinal direction X of the bottom of the workpiece W102 that has been subjected to press drawing tends to bulge away from the punch 174A, and distortion is likely to occur in the central portion in the longitudinal direction X of the bottom of the workpiece W102.

[0078] On the other hand, in the first press drawing process S1 in the manufacturing method for a bottomed container of this embodiment and the first press drawing process S1 performed by the first press unit of the press system 1, the occurrence of distortion of the bottom of the workpiece W2 formed through the first press drawing process S1 is suppressed. Fig. 10 is a diagram for explaining the first press drawing process S1 in the manufacturing method for a bottomed container of this embodiment and the first press drawing process S1 performed by the first press unit of the press system 1, Fig. 10(A) is a plan view showing the die 72A, Fig. 10(B) is a cross-sectional view showing the state in which the workpiece W1 is drawn to form the workpiece W2, and Fig. 10(C) is an enlarged view of part F surrounded by a dashed line in Fig. 10(B).

[0079] Referring to FIG. 10, the first press drawing process S1 is performed using a die 72A having a first forming hole 73A formed in a shape narrowing toward the inside in the width direction Y from both ends in the longitudinal direction X to the center, and a punch 74A corresponding to the die 72A. In the first press drawing process S1, the workpiece W1 in a flat plate state is subjected to press drawing using the die 72A and the punch 74A. The punch 74A presses the workpiece W1 into the first forming hole 73A of the die 72A, so that the workpiece W1 is formed into a cylindrical workpiece W2 having a bottom (see FIG. 10(B)). When the workpiece W1 is pressed into the first forming hole 73A, a compressive force is generated in the circumferential direction of the first forming hole 73A in the both end side processed portion P1 of the workpiece W1. On the other hand, when the workpiece W1 is pressed into the first forming hole 73A, a tensile force is generated in the central processed portion P2 of the workpiece W1 in the circumferential direction of the first forming hole 73A.

[0080] In the first press drawing process S1, in the workpiece W1, a compressive force is generated in the circumferential direction in the both end processed parts P1, and a tensile force is generated in the circumferential direction in the central processed part P2. Therefore, in the workpiece W1, the tensile force in the circumferential direction generated in the central processed part P2 opposes the compressive force in the both end processed parts P1. Then, in the workpiece W1, plastic flow occurs smoothly from the both end processed parts P1 side where the compressive force is generated to the central processed part P2 side where the tensile force is generated, and the workpiece W1 is pressed between the die 72A and the punch 74A, and the workpiece W1 is formed into the shape of the workpiece W2. That is, the material that has plastically flowed from the both end processed parts P1 side where the compressive force is generated to the central processed part P2 side where the tensile force is generated is used for forming the central processed part P2 without the volume becoming excessive in the central processed part P2. In this way, in the first press drawing process S1, plastic flow occurs smoothly from the both end side processed parts P1 where compressive force is applied to the center side processed part P2 where tensile force is applied, so that the volume of the material in the center side processed part P2 is prevented from becoming excessive, and plastic flow to the bottom side of the part formed into the shape of the workpiece W2 is prevented. As a result, as shown in Figures 10(B) and 10(C), in the first press drawing process S1, the central part in the longitudinal direction X of the bottom of the workpiece W2 that has been subjected to the press drawing is difficult to separate from the punch 74A, and has a shape that is substantially the same as the punch 74A or a shape that is considerably close to the shape of the punch 74A. Therefore, in the first press drawing process S1, distortion is prevented from occurring on the bottom side of the workpiece W2 in the central part in the longitudinal direction X.

[0081] As described above, according to the method for manufacturing a bottomed container of this embodiment, a square cylindrical bottomed container W3 having a bottom is manufactured by performing the first press drawing process S1 and the second press drawing process S2. Here, the external characteristics of the bottomed container W3 manufactured by the method for manufacturing a bottomed container of this embodiment will be described. FIG. 11 is a diagram for explaining the external characteristics of the manufactured bottomed container. Note that FIG. 11(A) is a diagram for explaining the external characteristics of a bottomed container W103 manufactured by a conventional method for manufacturing a bottomed container. FIG. 11(B) is a diagram for explaining the external characteristics of the bottomed container W3 manufactured by the method for manufacturing a bottomed container of this embodiment.

[0082] In the conventional method for manufacturing a bottomed container, as shown in FIG. 9, first, a flat workpiece W101 is subjected to a press drawing process using a die 172A having a forming hole 173A that is elliptical and spreads outward all around, to form a cylindrical workpiece W102 having an elliptical cross section. Then, the workpiece W102 is subjected to a press drawing process using a die (not shown) having a forming hole formed in a rectangular shape with four corners of the rectangle formed in arcs, to form a bottomed container W103 in the shape of a rectangular cylinder having a bottom, as shown in FIG. 11(A). In the bottomed container W103 manufactured by the conventional method for manufacturing a bottomed container, a thin linear pattern Q that curves toward the opening at the top end of the bottomed container W103 is generated on the side of the bottomed container W103, as shown in FIG. 11(A). Note that FIG. 11(A) shows the pattern Q generated on the side of the bottomed container W103 only diagrammatically. In the bottomed container W103, the portion of the pattern Q is not distorted, and the pattern Q on the side of the bottomed container W103 appears due to slight differences in the way light is reflected on the side of the bottomed container W103. In a conventional method for manufacturing a bottomed container, a rectangular cylindrical bottomed container W103 is formed by press drawing a cylindrical workpiece W102 having an elliptical cross-sectional shape, and when the corners of the bottom of the workpiece W102 are drawn again, the central portion in the major axis direction of the elliptical shape in the portion that widens in the minor axis direction of the elliptical shape is stretched while undergoing significant plastic flow in the vertical direction, and in the bottomed container W103, a thin linear pattern Q is generated that curves toward the opening at the top end of the bottomed container W103.

[0083] On the other hand, in the bottomed container W3 manufactured by the manufacturing method of the bottomed container of this embodiment, as shown in Fig. 11(B), a thin linear pattern R is generated on the side of the bottomed container W3, which extends while gently curving along a direction approximately parallel to the longitudinal direction X and curves slightly toward the bottom side of the bottomed container W3 in the central part of the longitudinal direction X. Note that Fig. 11(B) shows the pattern R generated on the side of the bottomed container W3 in a schematic manner. In the bottomed container W3, the part of the pattern R is not distorted, and the pattern R on the side of the bottomed container W3 appears due to a slight difference in the reflection of light on the side of the bottomed container W3. In the manufacturing method of the bottomed container of this embodiment, when the second press drawing process S2 is performed, the corner part of the bottom of the workpiece W2 moves to the side of the bottomed container W3 in the bottomed container W3 (workpiece W3) by plastic flow. Because the corner portions of the bottom of the workpiece W2 have been bent once, when they are moved to the side and stretched flat by the second press drawing process S2, they appear in a different appearance from the surrounding non-bent portions, and a pattern R appears on the side of the bottomed container W3. And because the central portion in the longitudinal direction X of the corner portions of the bottom of the workpiece W2 was formed to narrow inward in the width direction Y by the first press drawing process S1, when they are moved to the side and stretched flat by the second press drawing process S2, a thin linear pattern R appears on the side of the bottomed container W3, which extends while gently curving along a direction approximately parallel to the longitudinal direction X and curves slightly toward the bottom of the bottomed container W3 in the central portion in the longitudinal direction X, as shown in FIG. In this way, the rectangular cylindrical bottomed container W3 manufactured by carrying out the first press drawing process S1 and the second press drawing process S2 has a thin linear pattern R on its side that extends while gently curving along a direction approximately parallel to the longitudinal direction X and that curves slightly in the central part of the longitudinal direction X toward the bottom side of the bottomed container W3.

[0084] [2-3. Effects of this embodiment] According to the manufacturing method of a bottomed container and the press system 1 of this embodiment, the first forming hole 73A is formed so as to narrow from both ends in the longitudinal direction X to the center in the width direction Y within a range of the dimension in the width direction Y larger than the width dimension YB, which is the dimension in the width direction Y of the second forming hole 73B. As a result, in the first press drawing process S1, in the workpiece W1, a tensile force is generated in the circumferential direction of the first forming hole 73A in the central processed portion P2, which is a portion processed in the central side of the longitudinal direction X of the first forming hole 73A. Therefore, in the workpiece W1, the circumferential tensile force generated in the central processed portion P2 is opposed to the compressive force generated in the both end processed portions P1, which are portions processed in the longitudinal direction X of the first forming hole 73A. As a result, the volume of the material processed in the central side of the longitudinal direction X of the first forming hole 73A is prevented from becoming excessive, and plastic flow toward the bottom side of the workpiece W2 is prevented. In addition, the first forming hole 73A is formed so as to narrow from both ends in the longitudinal direction X to the center in the width direction Y in a range of the dimension in the width direction Y larger than the width dimension YB of the second forming hole 73B over the entire length in the vertical direction. Therefore, the force acting on the workpiece W1 at both ends and the center in the longitudinal direction X of the first forming hole 73A is adjusted throughout the entire process of the first press drawing process S1, and the volume of the material processed at the center in the longitudinal direction X of the first forming hole 73A is suppressed from becoming excessive over the entire length in the vertical direction, and plastic flow toward the bottom side of the workpiece W2 is suppressed. Then, in the second press drawing process S2, the workpiece W2 in a state in which the volume is suppressed from becoming excessive at the center in the longitudinal direction X and the plastic flow toward the bottom side is suppressed passes through the second forming hole 73B, which has a smaller dimension in the width direction Y than the first forming hole 73A, and is pressed and formed into a square tube shape. In this way, the workpiece W is finally formed into the workpiece W3 in a rectangular tubular state. As described above, according to the manufacturing method for a bottomed container and the press system 1 of the present embodiment, in the first press drawing process S1, the workpiece W is pressed while suppressing excess volume at the center side in the longitudinal direction X and suppressing plastic flow toward the bottom side, and in the second press drawing process, the workpiece W is pressed into a rectangular tubular state by being drawn in the width direction Y.Therefore, according to the manufacturing method for a bottomed container and the press system 1 of this embodiment, it is possible to suppress the occurrence of distortion on the bottom side of the central portion in the longitudinal direction X of the workpiece W. Furthermore, in the manufacturing method for a bottomed container and the press system 1 of this embodiment, the circumferential tensile force generated in the central processed portion P2 opposes the circumferential compressive force generated in the both end processed portions P1, so that buckling is less likely to occur in the central processed portion P2 and the occurrence of wrinkles can be suppressed. Furthermore, according to the manufacturing method for a bottomed container and the press system 1 of this embodiment, it is possible to suppress the occurrence of distortion on the bottom side of the workpiece W. Therefore, when the punching process S3 is performed, it is possible to suppress the occurrence of distortion in the wall of the bottomed container as the workpiece W after the punching process S3 is performed, and further, it is possible to suppress the occurrence of dimensional abnormalities in the corner portions of the bottom of the bottomed container.

[0085] As described above, according to the manufacturing method for a bottomed container and the press system 1 of this embodiment, by performing multiple press drawing processes using multiple dies having long hole-shaped forming holes 73, the workpiece W is shaped from a flat plate into a rectangular tube having a bottom, thereby making it possible to suppress the occurrence of distortion on the bottom side of the workpiece W when manufacturing a rectangular cylindrical bottomed container.

[0086] Furthermore, in the first press drawing process in which the workpiece W in a flat plate state is pressed and drawn, the compressive force generated in the processed portions at both ends in the longitudinal direction X of the forming hole 73 is also large. However, according to the manufacturing method for a bottomed container and the press system 1 of this embodiment, in the first press drawing process configured as the first press drawing process S1, a circumferential tensile force can be generated in the central processed portion P2 so as to oppose the circumferential compressive force generated in the both end processed portions P1. Therefore, even in the first press drawing process in which distortion of the bottom side of the workpiece W is likely to occur, the occurrence of distortion of the bottom side of the workpiece W can be efficiently suppressed.

[0087] In the manufacturing method for a bottomed container and the press system 1 of this embodiment, the first forming hole 73A is formed so as to narrow while curving inward in the width direction Y from both ends in the longitudinal direction X to the center, and to narrow most inward in the width direction Y at the center position CX in the longitudinal direction X. As a result, according to the manufacturing method for a bottomed container and the press system 1 of this embodiment, a circumferential tensile force can be generated in the center processed portion P2 so as to more evenly oppose the circumferential compressive force generated in the both end processed portions P1. This makes it possible to more efficiently suppress the occurrence of distortion on the bottom side of the workpiece W.

[0088] [3. Modifications] In the above embodiment, the manufacturing method and press system 1 for a bottomed container are described as an example in which two press drawing steps are performed as the multiple press drawing steps, with the first initial press drawing step being configured as the first press drawing step and the second final press drawing step being configured as the second press drawing step, but this is not necessarily the case. A manufacturing method and press system for a bottomed container in which three or more press drawing steps are performed as the multiple press drawing steps may be implemented. Furthermore, in a manufacturing method and press system for a bottomed container in which three or more press drawing steps are performed, a manufacturing method and press system for a bottomed container in which the first press drawing step and the second press drawing step are configured multiple times may be implemented. For example, the embodiment shown in FIG. 12 may be implemented.

[0089] FIG. 12 is a flowchart showing a method for manufacturing a bottomed container according to a modified example, and is also a flowchart showing a plurality of press drawing steps performed by a press system according to a modified example. FIG. 12 shows a modified example of a method for manufacturing a bottomed container in which a bottomed container is manufactured by forming a square cylindrical bottomed container having a bottom from a flat workpiece W by performing a plurality of press drawing steps using a plurality of dies having elongated forming holes. FIG. 12 also shows a plurality of press drawing steps performed by a modified example of a press system in which a square cylindrical bottomed container having a bottom is formed from a flat workpiece W by performing a plurality of press drawing steps using a plurality of dies having elongated forming holes. The method for manufacturing a bottomed container according to this modified example is implemented, for example, by performing a plurality of press drawing steps on the workpiece W using a press system 1, and the press system according to this modified example is configured as a press system 1 that performs a plurality of press drawing steps on the workpiece W. Therefore, the manufacturing method for bottomed containers of this modified example is configured as a manufacturing method for bottomed containers that produces rectangular cylindrical bottomed containers by performing a plurality of press drawing steps on the work W using a plurality of dies each including a die 72 and a punch 74 and each having an elongated forming hole 73 to form the work W from a flat plate into a rectangular cylindrical shape. The press system of this modified example is configured as a press system 1 that forms a rectangular cylindrical bottomed container by performing a plurality of press drawing steps on the work W using a plurality of dies each including a die 72 and a punch 74 and each having an elongated forming hole 73 to form the work W from a flat plate into a rectangular cylindrical shape having a bottom.

[0090] The manufacturing method of the bottomed container of this modification is configured to include three press drawing steps as the multiple press drawing steps. The press system of this modification is configured to perform three press drawing steps as the multiple press drawing steps. That is, as shown in FIG. 12, the manufacturing method of the bottomed container of this modification is configured to include a first press drawing step S11, a second press drawing step S12, and a third press drawing step S13. The press system of this modification is configured to perform the first press drawing step S11, the second press drawing step S12, and the third press drawing step S13. The first press drawing step S11 is the first press drawing step. The second press drawing step S12 is the press drawing step performed after the first press drawing step S11. The third press drawing step S13 is the final press drawing step performed after the second press drawing step S12. 12 does not show an example in which the ironing step is performed after the third drawing step S13 is completed, but the ironing step may be performed after the third drawing step S13 is completed. That is, after the first to third drawing steps S11 to S13 are completed, the formed rectangular cylindrical bottomed container may be subjected to an ironing step for reducing the plate thickness of the wall of the bottomed container.

[0091] The first drawing process S11 is one of the multiple drawing processes in the manufacturing method for a bottomed container of this modified example, excluding the final, third drawing process S13, and constitutes the first drawing process of the present invention. The first drawing process S11 is one of the multiple drawing processes performed in the press system of this modified example, excluding the final, third drawing process S13, and constitutes the first drawing process of the present invention.

[0092] The second press drawing process S12 is the next press drawing process of the first press drawing process among the multiple press drawing processes in the manufacturing method of the bottomed container of this modified example, and constitutes the second press drawing process of the present invention. The second press drawing process S12 is the next press drawing process of the first press drawing process among the multiple press drawing processes performed in the press system of this modified example, and constitutes the second press drawing process of the present invention. That is, the second press drawing process S12 is the next press drawing process of the first press drawing process S11 as the first press drawing process, and constitutes the second press drawing process. Also, the second press drawing process S12 constitutes the second press drawing process with respect to the first press drawing process S11, but constitutes the first press drawing process with respect to the third press drawing process S13. Specifically, the second press drawing process S12 is one of the press drawing processes excluding the final, third press drawing process S13 among the multiple press drawing processes, and constitutes the first press drawing process in the present invention relative to the third press drawing process S13.

[0093] The third drawing process S13 is the next drawing process of the first drawing process among the multiple drawing processes in the manufacturing method of the bottomed container of this modified example, and constitutes the second drawing process of the present invention. The third drawing process S13 is the next drawing process of the first drawing process among the multiple drawing processes performed in the press system of this modified example, and constitutes the second drawing process of the present invention. That is, the third drawing process S13 is the next drawing process of the second drawing process S12 as the first drawing process, and constitutes the second drawing process. The first to third drawing processes S11 to S13 will be described in more detail below.

[0094] Fig. 13 is a diagram showing an example of a die used in the press drawing process in the manufacturing method for a bottomed container of this modified example, and is also a diagram showing an example of a die in the press system of this modified example. More specifically, Fig. 13(A) is a plan view of a punch 74C and a die 72C in a die 71C used in the first press drawing process S11. Fig. 13(B) is a plan view of a punch 74D and a die 72D in a die 71D used in the second press drawing process S12. Fig. 13(C) is a plan view of a punch 74E and a die 72E in a die 71E used in the third press drawing process S13. The dies 72C to 72E used in the first to third press drawing processes S11 to S13 are each provided with an elongated forming hole 73. 13(A) to (C), the longitudinal direction X, which is the direction in which the molding hole 73 extends like an elongated hole, is indicated by an arrow X at both ends, and the width direction Y, which is the direction perpendicular to the longitudinal direction X, is indicated by an arrow Y at both ends.

[0095] 13(A), the metal mold 71C used in the first press drawing process S11 includes a die 72C and a punch 74C. The die 72C is provided as one of a plurality of dies 72 attached to the press system 1, and is configured as the die 72 used in the first press drawing process S11. The punch 74C is provided as one of a plurality of punches 74 attached to the press system 1, and is configured as the punch 74 used in the first press drawing process S11.

[0096] Referring to FIG. 13(A), the die 72C is provided with a molding hole 73C as a long hole-shaped molding hole 73 of the die 72. That is, the die 72C is provided with a molding hole 73C formed in a long hole shape in a plan view, with the dimension in the longitudinal direction X being larger than the dimension in the width direction Y. For example, the molding hole 73C is formed with both ends in the longitudinal direction X in a semicircular arc shape. The molding hole 73C is formed such that the shape of the part in the circumferential direction excluding both ends in the longitudinal direction X narrows toward the inside in the width direction Y from both ends in the longitudinal direction X to the center. That is, the molding hole 73C is formed such that the shape of the part in the circumferential direction excluding both ends in the longitudinal direction X gradually decreases in the dimension in the width direction Y from both ends in the longitudinal direction X to the center. The molding hole 73C is formed such that the shape of the part in the circumferential direction excluding both ends in the longitudinal direction X narrows toward the inside in the width direction Y from both ends in the longitudinal direction X to the center over the entire length in the up-down direction, which is the direction in which the molding hole 73C penetrates the die 72C. The forming hole 73C is formed so as to narrow while curving smoothly inward in the width direction Y from both ends in the longitudinal direction X to the center.

[0097] 13(A), the punch 74C has an outer peripheral shape formed to correspond to the forming hole 73C of the die 72C. Therefore, the punch 74C is formed so that both ends in a direction parallel to the longitudinal direction X of the forming hole 73C each have a semicircular cross-sectional shape. The punch 74C is formed so that the shape of the portion excluding both ends of the semicircular cross-sectional shape in the circumferential direction is smoothly curved and recessed in an arc shape from both ends in a direction parallel to the longitudinal direction X of the forming hole 73C to the center toward the inside in a direction parallel to the width direction Y of the forming hole 73C.

[0098] The first press drawing process S11 constitutes a first press drawing process. Therefore, the forming hole 73C constitutes a first forming hole of the present invention, and the mold 71C having the die 72C provided with the forming hole 73C as the first forming hole and the punch 74C corresponding to the die 72C constitutes a first mold of the present invention.

[0099] The first press drawing process S11 is performed using a die 71C as a first die having a forming hole 73C as a first forming hole. In the first press drawing process S11, a workpiece W11 as a flat workpiece W supplied from the workpiece supply device 10 of the press system 1 is subjected to press drawing using a die 72C and a punch 74C. In FIG. 13(A), the workpiece W11 in a flat workpiece state is shown by a two-dot chain line. In the first press drawing process S11, the punch 74C pushes the workpiece W11 into the forming hole 73C of the die 72C, so that the workpiece W11 is formed into a workpiece W12 (see FIG. 13(B)) as a cylindrical workpiece W having a bottom. The workpiece W12 formed through the first press drawing process S11 has a bottom and is formed into a cylindrically extending shape with a cross-sectional shape corresponding to the shape of the forming hole 73C. In Figure 13(B), the workpiece W12 when viewed in a plan view is shown by a dotted line.

[0100] 13(B), the metal mold 71D used in the second press drawing process S12 includes a die 72D and a punch 74D. The die 72D is provided as one of a plurality of dies 72 attached to the press system 1, and is configured as the die 72 used in the second press drawing process S12. The punch 74D is provided as one of a plurality of punches 74 attached to the press system 1, and is configured as the punch 74 used in the second press drawing process S12.

[0101] 13B, the die 72D is provided with a molding hole 73D as a long hole-shaped molding hole 73 of the die 72. That is, the die 72D is provided with a molding hole 73D whose dimension in the longitudinal direction X is larger than the dimension in the width direction Y and whose shape is formed in a long hole shape in a plan view. The molding hole 73D is formed, for example, with both ends in the longitudinal direction X each formed in a semicircular arc shape. The molding hole 73D is formed such that the shape of the part in the circumferential direction excluding both ends in the longitudinal direction X narrows while smoothly curving in an arc shape from both ends in the longitudinal direction X to the center toward the inside in the width direction Y. The molding hole 73D is formed such that the molding hole 73D narrows toward the inside in the width direction Y from both ends in the longitudinal direction X to the center over the entire length in the up-down direction, which is the direction in which the molding hole 73D penetrates the die 72D. Moreover, the forming hole 73D is formed to have a smaller dimension in the width direction Y over the longitudinal direction X than the forming hole 73C of the die 72C used in the first press drawing process S11. Furthermore, the forming hole 73D is formed to have a larger dimension in the width direction Y over the entire vertical length than the second forming hole 73B. Therefore, the forming hole 73C of the die 72C used in the first press drawing process S11 is formed to have a larger dimension in the width direction Y over the longitudinal direction X than the forming hole 73D of the die 72D used in the second press drawing process S12, and is formed to have a larger dimension in the width direction Y over the entire vertical length.

[0102] 13(B), the punch 74D has an outer peripheral shape formed to correspond to the forming hole 73D of the die 72D. Therefore, the punch 74D is formed so that both ends in a direction parallel to the longitudinal direction X of the forming hole 73D each have a semicircular cross-sectional shape. The punch 74D is formed so that the shape of the portion excluding both ends of the semicircular cross-sectional shape in the circumferential direction is smoothly curved and recessed in an arc shape from both ends in a direction parallel to the longitudinal direction X of the forming hole 73D to the center toward the inside in a direction parallel to the width direction Y of the forming hole 73D.

[0103] In addition, the second press drawing process S12 constitutes a second press drawing process with respect to the first press drawing process S11 as the first press drawing process. Therefore, in relation to the first press drawing process S11, the forming hole 73D constitutes the second forming hole of the present invention, and the die 72D in which the forming hole 73D is provided as the second forming hole and the die 71D having the punch 74D corresponding to the die 72D constitutes the second die of the present invention. In addition, the second press drawing process S12 constitutes a first press drawing process with respect to the third press drawing process S13 as the second press drawing process. Therefore, in relation to the third press drawing process S13, the forming hole 73D constitutes the first forming hole of the present invention, and the die 71D in which the forming hole 73D is provided as the first forming hole and the punch 74D corresponding to the die 72D constitutes the first die of the present invention.

[0104] The second press drawing process S12 is performed using a die 71D as a second die having a forming hole 73D as a second forming hole for the first press drawing process S11. The second press drawing process S12 is performed using a die 71D as a first die having a forming hole 73D as a first forming hole for the third press drawing process S13. In the second press drawing process S12, the cylindrical workpiece W12 formed through the first press drawing process S11 is subjected to press drawing using a die 72D and a punch 74D. In the second press drawing process S12, the punch 74D pushes the workpiece W12 into the forming hole 73D of the die 72D, so that the workpiece W12 is formed into a cylindrical workpiece W13 (see FIG. 13(C)). The workpiece W13 formed through the second press drawing process S12 has a bottom area equal to or smaller than that of the workpiece W12, and is formed into a cylindrically extending shape with a cross-sectional shape corresponding to the shape of the forming hole 73D. In Figure 13(C), the workpiece W13 as viewed in a plan view is shown by a dotted line.

[0105] 13(C), the metal mold 71E used in the third press drawing process S13 includes a die 72E and a punch 74E. The die 72E is provided as one of a plurality of dies 72 attached to the press system 1, and is configured as the die 72 used in the third press drawing process S13. The punch 74E is provided as one of a plurality of punches 74 attached to the press system 1, and is configured as the punch 74 used in the third press drawing process S13.

[0106] Referring to FIG. 13(C), the die 72E is provided with a forming hole 73E as a long hole-shaped forming hole 73 of the die 72. That is, the die 72E is provided with a forming hole 73E formed in a long hole shape in a plan view, with the dimension in the longitudinal direction X being larger than the dimension in the width direction Y. The forming hole 73E is formed in a substantially rectangular shape elongated in the longitudinal direction X. More specifically, the forming hole 73E is formed in a shape in which the four corners of the rectangle are formed in an arc shape. The forming hole 73E is formed to have a smaller dimension in the width direction Y over the longitudinal direction X than the forming hole 73D of the die 72D used in the second press drawing process S12. The forming hole 73E is formed to have a smaller dimension in the width direction Y than the forming hole 73D over the entire length in the up-down direction, which is the direction in which the forming hole 73E penetrates the die 72E. Therefore, the forming hole 73D of the die 72D used in the second drawing process S12 is formed to have a larger dimension in the width direction Y over the longitudinal direction X and over the entire vertical length than the forming hole 73E of the die 72E used in the third drawing process S13. In this modification, the third drawing process S13 constitutes the final drawing process. Therefore, the shape of the forming hole 73E corresponds to the cross-sectional shape of the rectangular cylindrical bottomed container finally manufactured through multiple drawing processes in the manufacturing method of the bottomed container of this modification.

[0107] 13(C), the punch 74E has an outer peripheral shape formed to a shape corresponding to the forming hole 73E of the die 72E. Therefore, the punch 74E is formed to have a substantially rectangular cross-sectional shape that is elongated in a direction parallel to the longitudinal direction X of the forming hole 73B.

[0108] The third drawing process S13 constitutes a second drawing process in comparison with the second drawing process S12 as a first drawing process. Therefore, the forming hole 73E constitutes a second forming hole of the present invention, and the mold 71E having the die 72E provided with the forming hole 73E as the second forming hole and the punch 74E corresponding to the die 72E constitutes a second mold of the present invention.

[0109] The third press drawing process S13 is performed using a die 71E as a second die having a forming hole 73E as a second forming hole for the second press drawing process S12. In the third press drawing process S13, the cylindrical workpiece W13 formed through the second press drawing process S12 is subjected to press drawing using a die 72E and a punch 74E. In the third press drawing process S13, the punch 74E pushes the workpiece W13 into the forming hole 73E of the die 72E, so that the workpiece W13 is formed into a workpiece W that is a square cylindrical bottomed container having a bottom. By performing the third press drawing process S13, a square cylindrical bottomed container formed as the square cylindrical workpiece W is manufactured. In this modified example, the third press drawing process S13 constitutes the final press drawing process. Therefore, the workpiece W formed through the third press drawing process S13 is formed into the shape of a bottomed container manufactured through multiple press drawing processes in the bottomed container manufacturing method of this modified example, and constitutes a bottomed container in the shape of a rectangular tube having a bottom, manufactured by the bottomed container manufacturing method of this modified example.

[0110] Here, the relationship between the shapes of the forming hole 73 of the die 72 in the first drawing process S11, the second drawing process S12, and the third drawing process S13 will be further described. Figure 14 is a schematic diagram showing the forming holes 73 of the die 72 used in the multiple drawing processes in the manufacturing method for a bottomed container according to the modified example, and is also a schematic diagram showing the forming holes 73 of the die 72 used in the multiple drawing processes performed in the press system according to the modified example. More specifically, Figure 14 shows the forming hole 73C of the die 72C used in the first drawing process S11, the forming hole 73D of the die 72D used in the second drawing process S12, and the forming hole 73E of the die 72E used in the third drawing process S13 in a comparative manner. Naturally, die 72C, die 72D, and die 72E are not a single die 72 but separate, different dies 72. However, in Figure 14, die 72C, die 72D, and die 72E are shown in a stacked state in order to contrast forming hole 73C, forming hole 73D, and forming hole 73E.

[0111] First, the relationship between the shape of the forming hole 73C of the die 72C used in the first press drawing process S11 and the shape of the forming hole 73D of the die 72D used in the second press drawing process S12 will be described. In the relationship between the first press drawing process S11 as the first press drawing process and the second press drawing process S12 as the second press drawing process, the forming hole 73C constitutes the first forming hole, and the forming hole 73D constitutes the second forming hole. With reference to FIG. 14, the area of ​​the forming hole 73C constituting the first forming hole is larger over the entire circumference than the area of ​​the forming hole 73D constituting the second forming hole. That is, when the die 72C and the die 72D are overlapped, the outline of the forming hole 73C and the outline of the forming hole 73D do not overlap in a plan view, and the forming hole 73D is disposed inside the forming hole 73C. Therefore, the forming hole 73C constituting the first forming hole is formed to have a larger dimension in the width direction Y over the longitudinal direction X than the forming hole 73D constituting the second forming hole. Furthermore, the forming hole 73C constituting the first forming hole is formed to have a larger dimension in the width direction Y than the forming hole 73D constituting the second forming hole over the entire length in the vertical direction, which is the direction in which the forming hole 73C penetrates the die 72C. More specifically, the forming hole 73C is formed so that the semicircular arc-shaped portions at both ends in the longitudinal direction X are large enough to surround the semicircular arc-shaped portions at both ends in the longitudinal direction X of the forming hole 73D over the entire length in the vertical direction. And, the portion of the forming hole 73C formed to narrow inward in the width direction Y from both ends in the longitudinal direction X to the center is formed to have a size that surrounds the portion of the forming hole 73D formed to narrow inward in the width direction Y from both ends in the longitudinal direction X to the center over the entire length in the vertical direction. Therefore, the molding hole 73C constituting the first molding hole is formed to have a larger dimension in the width direction Y over the entire length in the vertical direction than the molding hole 73E constituting the second molding hole.

[0112] Next, the relationship between the shape of the forming hole 73D of the die 72D used in the second press drawing process S12 and the shape of the forming hole 73E of the die 72E used in the third press drawing process S13 will be described. In the relationship between the second press drawing process S12 as the first press drawing process and the third press drawing process S13 as the second press drawing process, the forming hole 73D constitutes the first forming hole, and the forming hole 73E constitutes the second forming hole. With reference to FIG. 14, the area of ​​the forming hole 73D constituting the first forming hole is larger over the entire circumference than the area of ​​the forming hole 73E constituting the second forming hole. That is, in a state where the die 72D and the die 72E are overlapped, the outline of the forming hole 73D and the outline of the forming hole 73E do not overlap in a plan view, and the forming hole 73E is disposed inside the forming hole 73D. Therefore, the forming hole 73D constituting the first forming hole is formed to have a larger dimension in the width direction Y over the longitudinal direction X than the forming hole 73E constituting the second forming hole. Furthermore, the forming hole 73D constituting the first forming hole is formed to have a larger dimension in the width direction Y than the forming hole 73E constituting the second forming hole over the entire length in the vertical direction, which is the direction in which the forming hole 73D penetrates the die 72D. More specifically, the forming hole 73E has a substantially rectangular shape, and the width dimension YE, which is the dimension in the width direction Y of the forming hole 73E, is set to a constant dimension. The width dimension YE of the forming hole 73E is set to a constant dimension over the entire length in the vertical direction, which is the direction in which the forming hole 73E penetrates the die 72E. On the other hand, the semicircular arc-shaped portions at both ends in the longitudinal direction X of the forming hole 73D are formed to a size that surrounds both ends in the longitudinal direction of the forming hole 73E on the outside over the entire length in the vertical direction. Furthermore, in the circumferential direction, except for both ends in the longitudinal direction X, the forming hole 73D is formed such that the dimension in the width direction Y gradually decreases from both ends in the longitudinal direction X to the center over the entire vertical length, and has the smallest width dimension YD at the center position in the longitudinal direction X. The width dimension YD of the portion of the forming hole 73D with the smallest dimension in the width direction Y other than both ends in the longitudinal direction X is formed larger than the width dimension YE of the forming hole 73E over the entire vertical length.Therefore, the molding hole 73D constituting the first molding hole is formed to have a larger dimension in the width direction Y over the entire length in the vertical direction than the molding hole 73E constituting the second molding hole.

[0113] According to the manufacturing method and press system for a bottomed container according to the present modified example described above, the forming hole 73C of the die 72C used in the first press drawing process S11 is formed so as to narrow toward the inside in the width direction Y from both ends in the longitudinal direction X to the center in a range in which the dimension in the width direction Y is larger than that of the forming hole 73D of the die 72D used in the second press drawing process S12. As a result, in the first press drawing process S11, a tensile force is generated in the circumferential direction of the forming hole 73C in the part of the workpiece W11 that is machined at the center of the longitudinal direction X of the forming hole 73C. Therefore, in the workpiece W11, the tensile force generated in the part of the workpiece W11 that is machined at the center of the longitudinal direction X of the forming hole 73C opposes the compressive force generated in the part of the workpiece W11 that is machined at both ends in the longitudinal direction X of the forming hole 73C. As a result, the volume of the material machined at the center of the forming hole 73C is prevented from becoming excessive, and plastic flow toward the bottom side of the workpiece W12 is prevented. Therefore, the occurrence of distortion on the bottom side of the central portion in the longitudinal direction X of the workpiece W12 can be suppressed.

[0114] Furthermore, according to the manufacturing method and press system for a bottomed container of this modification, the forming hole 73D of the die 72D used in the second press drawing process S12 is formed so as to narrow toward the inside in the width direction Y from both ends in the longitudinal direction X to the center in a range in which the dimension in the width direction Y is larger than that of the forming hole 73E of the die 72E used in the third press drawing process S13. As a result, in the second press drawing process S12, a tensile force is generated in the circumferential direction of the forming hole 73D in the part of the workpiece W12 that is machined at the center of the longitudinal direction X of the forming hole 73D. Therefore, in the workpiece W12, the tensile force generated in the part of the workpiece W12 that is machined at the center of the longitudinal direction X of the forming hole 73D opposes the compressive force generated in the part of the workpiece W12 that is machined at both ends in the longitudinal direction X of the forming hole 73D. As a result, the volume of the material machined at the center of the forming hole 73D is prevented from becoming excessive, and plastic flow toward the bottom side of the workpiece W13 is prevented. Therefore, the occurrence of distortion on the bottom side of the central portion in the longitudinal direction X of the workpiece W13 can be suppressed.

[0115] As described above, according to the manufacturing method and press system for a bottomed container of this modified example, by performing multiple press drawing processes using multiple dies having long hole-shaped forming holes 73 to shape the workpiece W from a flat state into a square tube shape having a bottom, it is possible to suppress the occurrence of distortion on the bottom side of the workpiece W when manufacturing a square tube-shaped bottomed container.

[0116] The above describes the embodiments and modifications of the present invention, but the present invention is not limited to the above-mentioned embodiments and modifications, and can be applied in various ways within the scope of the claims.

[0117] For example, the first press drawing process and the second press drawing process described in the above embodiment and modified example are not limited to the manufacturing method and press system for bottomed containers that perform two or three press drawing processes, but can also be applied to a manufacturing method and press system for bottomed containers that perform four or more press drawing processes. Furthermore, the first press drawing process and the second press drawing process described in the above embodiment and modified example are not limited to a form in which a plurality of press drawing processes are performed in a press system 1 having a transfer press device 50 provided with a plurality of dies, but can also be applied to a form in which a plurality of press drawing processes are performed in a press system provided with a plurality of single press machines each provided with a die. In a form in which a plurality of press drawing processes are performed in a press system provided with a plurality of single press machines, the work may be transported between the plurality of press machines by an operator, or may be transported by a work transport machine. [Explanation of symbols]

[0118] 1 Press System 71A First Mold 71B Second mold 72, 72A, 72B Dies 73 Molding hole 73A First forming hole 73B Second forming hole W, W1, W2, W3 Work S1 First press drawing process S2 Second press drawing process

Claims

1. A method for manufacturing a bottomed container, comprising the steps of: forming a workpiece from a flat plate into a bottomed rectangular cylindrical container by performing a press drawing process multiple times using a plurality of dies having elongated forming holes; a first press drawing process which is performed using a first die including a die having a first forming hole as the long hole-shaped forming hole, and which is configured as at least one of the press drawing processes excluding a final press drawing process among the multiple press drawing processes; a second drawing step which is performed using a second die having a second forming hole as the elongated forming hole and which is configured as a subsequent press drawing step to the first press drawing step among the plurality of press drawing steps; The first molding hole is formed to have a larger dimension in a width direction, which is a direction perpendicular to a longitudinal direction, in which the first molding hole extends like a long hole, than the second molding hole over the entire length in a vertical direction, in which the first molding hole penetrates the die; The first molding hole is formed so as to narrow toward the inside in the width direction from both ends to the center in the longitudinal direction over the entire length in the up-down direction. A method for manufacturing a bottomed container, comprising:

2. The first press drawing process is configured as a first press drawing process among the plurality of press drawing processes. The method for manufacturing a bottomed container according to claim 1 .

3. The first molding hole is formed so as to be curved and narrowed toward the inside in the width direction from both ends in the longitudinal direction to the center, and is narrowed most toward the inside in the width direction at the center position in the longitudinal direction. The method for producing a cylindrical bottomed container according to claim 1 or 2.

4. A press system for forming a rectangular cylindrical container with a bottom by performing a press drawing process multiple times using a plurality of dies having elongated forming holes to form a workpiece from a flat plate into a rectangular cylindrical shape having a bottom, a first press section that has a first mold including a die having a first forming hole as the forming hole having a long hole shape, and that performs a first press drawing process using the first mold, the first press drawing process being configured as at least one of the press drawing processes excluding a final press drawing process among the multiple press drawing processes; a second press section that has a second die having a second forming hole as the forming hole having an elongated hole shape, and that performs a second press drawing process using the second die as a press drawing process subsequent to the first press drawing process among the plurality of press drawing processes, The first molding hole is formed to have a larger dimension in a width direction, which is a direction perpendicular to a longitudinal direction, in which the first molding hole extends like a long hole, than the second molding hole over the entire length in a vertical direction, in which the first molding hole penetrates the die; The first molding hole is formed so as to narrow toward the inside in the width direction from both ends to the center in the longitudinal direction over the entire length in the up-down direction. A press system characterized by:

5. The first press unit performs the first press drawing process, which is configured as a first press drawing process among the plurality of press drawing processes, by using the first die.

5. The press system according to claim 4.

6. The first molding hole is formed so as to be curved and narrowed toward the inside in the width direction from both ends in the longitudinal direction to the center, and is narrowed most toward the inside in the width direction at the center position in the longitudinal direction.

6. The press system according to claim 4 or 5.

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