Method for manufacturing bottomed container, and press system

Abstract

The present invention prevents 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.　A first press drawing step S1 is performed using a first die 71A having an elongated first shaping hole 73A, and is configured as a press drawing step that is performed at least other than the final step. A second press drawing step S2 is performed using a second die 71B 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 the center in the longitudinal direction.

Description

Method for manufacturing bottomed container and press system

[0001] The present invention relates to a method for manufacturing a bottomed container, and a press system for manufacturing 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.

[0002] In press molding, a workpiece is machined using a mold that includes a die with a forming hole and a punch that presses the workpiece into the forming hole of the die. To mold a rectangular cylindrical container with a cross section extending in the longitudinal direction and a bottom, press molding is performed to form the rectangular cylindrical container from a flat plate by performing multiple press-drawing processes using multiple molds with elongated forming holes. For example, Non-Patent Document 1 discloses a press molding method for forming a rectangular cylindrical container with a cross section that is approximately rectangular from a flat plate by performing multiple press-drawing processes using multiple molds with elongated forming holes.

[0003] As disclosed in Non-Patent Document 1, a rectangular cylindrical bottomed container is manufactured by forming it from a flat plate through multiple press-drawing processes using multiple dies with elongated forming holes. While the shape of the bottomed container formed through multiple press-drawing processes may determine the final shape of the product, the rectangular cylindrical bottomed container may also be subjected to a further ironing process after multiple press-drawing processes are completed. In the ironing process, which is performed after multiple press-drawing processes are completed, a ironing die is used to iron the rectangular cylindrical bottomed container, 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 rectangular cylinder with a substantially rectangular cross section, a die having a forming hole with no straight lines and an elliptical shape that widens outward is used in the drawing steps other than the final one of multiple drawing steps. That is, in the intermediate drawing steps other than the final drawing step that defines the final shape of the product or defines a shape that corresponds to the final shape of the product, the elongated forming hole in the die is formed into an elliptical shape that is connected in a gentle arc shape around the entire circumference.

[0005] When press-drawing is performed using a die having a long-hole-shaped forming hole, compressive forces are generated in the workpiece being drawn at both ends of the longitudinal direction, i.e., the direction in which the forming hole extends. On the other hand, if the longitudinally extending portion of the long-hole-shaped forming hole is linear, the workpiece is bent without any circumferential force being generated in the portion of the workpiece that is machined near the longitudinal center of the forming hole. In this case, compressive forces act from the portions machined at both ends of the longitudinal direction to the portions machined near the longitudinal center. In other words, compressive forces generated in the portions machined at both ends of the longitudinal direction also generate compressive forces near the longitudinal center when the workpiece is bent. As a result, buckling and wrinkles are likely to occur in the portion machined near the longitudinal center. 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 that expands outward around the entire circumference is used. By using a die having an elliptical shape, compressive force is generated not only in the portions of the workpiece that are machined at both ends in the longitudinal direction, but also in the portion machined near the center in the longitudinal direction. Therefore, compressive force is generated around the entire circumferential direction of the workpiece, making it less likely for buckling to occur in the portion machined near the center in the longitudinal direction, thereby suppressing the occurrence of wrinkles.

[0006] Hiromi Yoshida, "The Complete Guide to Press Processing," Nikkan Kogyo Shimbun, September 2015, pp. 94-95

[0007] In a press-drawing process using a die with a long-hole-shaped forming hole, a die with an elliptical forming hole is used to generate a compressive force around the entire circumferential circumference of the workpiece, thereby suppressing the occurrence of wrinkles due to buckling in the longitudinal center. However, since the amount of drawing is large at both longitudinal ends, plastic flow of material occurs from both longitudinal ends toward the center. Therefore, when circumferential compressive force is generated even in the portion being drawn in the longitudinal center, the volume of material in the longitudinal center becomes excessive. As a result, the excess volume of material in the longitudinal center plastically flows toward the bottom of the workpiece, which is not constrained by the punch and die of the die. This creates a problem of distortion being likely to occur in the bottom of the longitudinal center portion of the workpiece after press-drawing. Furthermore, if distortion occurs on the bottom side of the longitudinal central portion of a bottomed container, which is a workpiece formed after multiple press-drawing processes, when a ironing process is performed after multiple press-drawing processes, the bottomed container will suffer from overall distortion and dimensional abnormalities. More specifically, if distortion occurs on the bottom side of the longitudinal central portion after multiple press-drawing processes, when a subsequent ironing process is performed, distortion will occur not only in the bottom side of the bottomed container but also in the wall portion of the bottomed container, and dimensional abnormalities will also occur in the corners of the bottom of the bottomed container. Therefore, when a further ironing process is performed after press-forming that involves multiple press-drawing processes, the distortion on the bottom side of the workpiece will cause distortion in the wall of the bottomed container after ironing and dimensional abnormalities in the corners 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 prevent distortion from occurring on the bottom side of a workpiece when manufacturing a bottomed rectangular cylindrical container by performing multiple press drawing processes using multiple molds with long hole-shaped forming holes to shape the workpiece from a flat state into a rectangular cylindrical state with a bottom.

[0009] (1) A method for manufacturing a bottomed container of the present invention is a method for manufacturing a bottomed container in which a workpiece is formed from a flat plate into a rectangular cylindrical shape having a bottom by performing a plurality of press-drawing steps using a plurality of dies having elongated forming holes, thereby manufacturing a rectangular cylindrical bottomed container, the method comprising: a first press-drawing step performed using a first die including a die having a first forming hole as the elongated forming hole and a punch for pressing the workpiece into the first forming hole, the first press-drawing step being configured as at least one of the press-drawing steps excluding the final press-drawing step among the plurality of press-drawing steps; and a second press-drawing step performed using a second die having a second forming hole as the elongated forming hole, the second press-drawing step being configured as the press-drawing step subsequent to the first press-drawing step among the plurality of press-drawing steps. The first molding hole is formed to have a larger width dimension, which is a direction perpendicular to the longitudinal direction in which the first molding hole extends like an elongated hole, than the second molding hole over its entire length in the vertical direction, which is the direction in which the first molding hole penetrates the die; the first molding hole is formed to narrow inward in the width direction from both ends in the longitudinal direction to the center over its entire length in the vertical direction; the outer peripheral shape of the punch is formed to correspond to the first molding hole, and the cross-sectional shape of the punch is formed to curve and concave inward in the direction parallel to the width direction from both ends in the direction parallel to the longitudinal direction to the center.

[0010] According to the method for manufacturing a bottomed container described in (1) above, the first forming hole is formed so as to narrow inward in the width direction from both longitudinal ends to the center within a range of width dimensions 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 machined near the longitudinal center of the first forming hole. Therefore, the circumferential tensile force generated in the portion of the workpiece machined near the longitudinal center of the first forming hole opposes the compressive force generated in the portion of the workpiece machined near both longitudinal ends of the first forming hole. This prevents the volume of material processed near the longitudinal center of the first forming hole from becoming excessive, thereby suppressing plastic flow toward the bottom of the workpiece. The first forming hole is formed so that, over its entire vertical length, it tapers inward in the width direction from both longitudinal ends to the center, within a range of width dimensions larger than the width dimension of the second forming hole. Therefore, the force acting on the workpiece at both longitudinal ends and the center of the first forming hole is adjusted throughout the first drawing process, preventing excessive volume of material processed at the longitudinal center of the first forming hole over its entire vertical length, thereby suppressing plastic flow toward the bottom of the workpiece. Then, in the second drawing process, the workpiece, in which excessive volume at the longitudinal center is suppressed and plastic flow toward the bottom is suppressed, passes through the second forming hole, which has a width dimension smaller than the first forming hole, and is drawn into a rectangular tube shape or a shape close to a rectangular tube shape. After the final drawing process, the workpiece is finally formed into a rectangular tube shape. Thus, according to the method for manufacturing a bottomed container described in (1) above, in the first press-drawing step, the workpiece is press-formed while preventing excess volume at the longitudinal center and thereby preventing plastic flow toward the bottom, and in the second press-drawing step, the workpiece is pressed into a rectangular tubular shape or a shape close to a rectangular tubular shape by being drawn in the width direction. Therefore, according to the method for manufacturing a bottomed container described in (1) above, it is possible to prevent distortion from occurring on the bottom side of the longitudinal center portion of the workpiece.Furthermore, in the method for manufacturing a bottomed container described in (1) above, the circumferential tensile force generated in the portion processed at the center in the longitudinal direction opposes the circumferential compressive force generated in the portion processed at both ends in the longitudinal direction, so that buckling is less likely to occur in the portion 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 "vertical direction." Furthermore, 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 method for manufacturing a bottomed container described in (1) above, by performing multiple press drawing processes using multiple molds with elongated forming holes to shape the workpiece from a flat plate into a rectangular cylindrical shape with a bottom, it is possible to prevent distortion from occurring on the bottom side of the workpiece when manufacturing a rectangular cylindrical bottomed container.

[0012] (2) In the method for manufacturing a bottomed container of the present invention, it is more preferable that the first press-drawing step is configured as a first press-drawing step among the plurality of press-drawing steps.

[0013] In the initial 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 method for manufacturing a bottomed container described in (2) above, in the initial 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 initial drawing process, in which distortion of the bottom of the workpiece is likely to occur, it is possible to efficiently suppress the occurrence of distortion of the bottom of the workpiece.

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

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

[0016] (4) A press system of the present invention is a press system for forming a rectangular cylindrical bottomed container by performing a plurality of press drawing steps using a plurality of dies each having an elongated forming hole to form a workpiece from a flat state into a rectangular cylindrical state having a bottom, the press system comprising: a first press unit having a first die including a die having a first forming hole as the elongated forming hole and a punch for pressing the workpiece into the first forming hole, the first press unit using the first die to perform a first press drawing step configured as at least one of the press drawing steps excluding a final press drawing step among the plurality of press drawing steps; and a second press unit having a second die having a second forming hole as the elongated forming hole, the second press drawing step being configured as a press drawing step subsequent to the first press drawing step among the plurality of press drawing steps, using the second die. The first molding hole is formed to have a larger width dimension, which is a direction perpendicular to the longitudinal direction in which the first molding hole extends like an elongated hole, than the second molding hole over its entire length in the vertical direction, which is the direction in which the first molding hole penetrates the die; the first molding hole is formed to narrow inward in the width direction from both ends in the longitudinal direction to the center over its entire length in the vertical direction; the outer peripheral shape of the punch is formed to correspond to the first molding hole, and the cross-sectional shape of the punch is formed to curve and concave inward in the direction parallel to the width direction from both ends in the direction parallel to the longitudinal direction to the center.

[0017] According to the press system described in (4) above, the first forming hole provided in the first die of the first press unit is formed so as to narrow inward in the width direction from both longitudinal ends toward the center within a range of width dimensions larger than the width dimension of the second forming hole provided in the second die of the second press unit. As a result, when the first press drawing process is performed in the first press unit, a tensile force is generated in the circumferential direction of the first forming hole in the portion of the workpiece that is machined near the longitudinal center of the first forming hole. Therefore, the circumferential tensile force generated in the portion of the workpiece that is machined near the longitudinal center of the first forming hole opposes the compressive force generated in the portion of the workpiece that is machined near both longitudinal ends of the first forming hole. This prevents the volume of material processed near the longitudinal center of the first forming hole from becoming excessive, thereby suppressing plastic flow toward the bottom of the workpiece. The first forming hole is formed so that, over its entire vertical length, it tapers inward in the width direction from both longitudinal ends to the center, within a range of width dimensions larger than the width dimension of the second forming hole. Therefore, the force acting on the workpiece at both longitudinal ends and the center of the first forming hole is adjusted throughout the first drawing process, preventing excessive volume of material processed at the longitudinal center of the first forming hole over the entire vertical length, thereby suppressing plastic flow toward the bottom of the workpiece. Then, when the second drawing process is performed in the second press, the workpiece, in which excessive volume at the longitudinal center is suppressed and plastic flow toward the bottom is suppressed, passes through the second forming hole, which has a width dimension smaller than the first forming hole, and is drawn into a rectangular tube shape or a shape close to a rectangular tube shape. After the final drawing process, the workpiece is finally formed into a rectangular tube shape.According to the press system described in (4) above, the first press-drawing process performed on the workpiece in the first press unit prevents excess volume in the longitudinal center and suppresses plastic flow toward the bottom, resulting in press-forming. The second press-drawing process performed on the second press unit reduces the width of the workpiece to form a rectangular tube or a shape close to a rectangular tube. Therefore, the press system described in (4) above can prevent distortion from occurring near the bottom of the longitudinal center portion of the workpiece. Furthermore, the press system described in (4) above prevents buckling and wrinkles from occurring in the longitudinal center portion because the circumferential tensile force generated in the longitudinal center portion opposes the circumferential compressive force generated in the longitudinal end portions. The "width direction" refers to the direction perpendicular to the "longitudinal direction, i.e., the elongated hole-like direction" and perpendicular to both the "longitudinal direction" and the "up-down direction." Furthermore, the term "direction extending in the shape of an elongated hole" is synonymous with the term "direction extending in the shape of an elongated hole."

[0018] As described above, according to the press system described in (4) above, by performing multiple press drawing processes using multiple molds with elongated forming holes, the workpiece is shaped from a flat plate into a rectangular cylindrical shape with a bottom, thereby making it possible to prevent distortion from occurring on the bottom side of the workpiece when forming a rectangular cylindrical bottomed container.

[0019] (5) In the press system of the present invention, it is more preferable that the first press section performs the first drawing process, which is configured as a first drawing process among the plurality of drawing processes, using the first die.

[0020] In the initial 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, with the press system described in (5) above, when the initial drawing process is performed in the first press unit, 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 initial drawing process, in which distortion of the bottom side of the workpiece is likely to occur, distortion of the bottom side of the workpiece can be efficiently suppressed.

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

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

[0023] According to the present invention, a method for manufacturing a bottomed container and a press system can be provided that can suppress distortion on the bottom side of a workpiece when manufacturing a bottomed rectangular cylindrical container by performing multiple press drawing processes using multiple molds with long hole-shaped forming holes to shape the workpiece from a flat plate into a rectangular cylindrical shape with a bottom.

[0024] 4(A) is an example of a press system according to the present embodiment; FIG. 4(B) is a side cross-sectional view of a transfer press device in the press system, showing an enlarged view of a portion of the transfer press device; FIG. 4(C) is a flowchart showing an example of a method for manufacturing a bottomed container according to the present embodiment, and also a flowchart showing an example of a plurality of press drawing steps performed in the press system; FIG. 4(B) is a diagram showing an example of a first die used in a first press drawing step in the method for manufacturing a bottomed container, and also shows an example of a first die in a first press section of the press system, where FIG. 4(A) is a plan cross-sectional view of a punch in the first die, FIG. 4(B) is a plan view of a die in the first die, and FIG. 4(C) is a cross-sectional view taken along line A-A in FIG. 4(B). 5(A) is a diagram showing an example of a second die used in a second drawing step in a method for manufacturing a bottomed container, and is also a diagram showing an example of the second die in a second press unit of a press system, where Fig. 5(A) is a plan sectional 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 sectional view taken along line B-B in Fig. 5(B).

[0023] Fig. 5(B) is a diagram for explaining a workpiece to be subjected to drawing in a method for manufacturing a bottomed container and a press system.

[0024] Fig. 5(B) is a diagram showing, in comparison, forming holes in dies used in a first drawing step and a second drawing step in a method for manufacturing a bottomed container, and is also a diagram showing, in comparison, forming holes in dies used in a first drawing step and a second drawing step performed by a first press unit and a second press unit in a press system. 9A and 9B are diagrams for explaining forces acting on a workpiece in a first press drawing step in a method for manufacturing a bottomed container, and for explaining forces acting on a workpiece in a first press drawing step performed by a first press unit in a press system. These diagrams are diagrams for explaining a conventional press drawing step, in which Fig. 9A is a plan view showing a die, Fig. 9B is a cross-sectional view showing a state in which the workpiece is being drawn, and Fig. 9C is an enlarged view of part D surrounded by a dashed line in Fig. 9B.11(A) and 11(B) are diagrams for explaining a first press drawing step in a method for manufacturing a bottomed container and a first press drawing step performed by a first press unit of a press system, where Fig. 10(A) is a plan view showing a die, Fig. 10(B) is a cross-sectional view showing a state in which a workpiece has been subjected to drawing, and Fig. 10(C) is an enlarged view of portion F surrounded by a dashed line in Fig. 10(B). 11(A) and 11(B) are diagrams for explaining external features of a manufactured bottomed container, where Fig. 11(A) is a diagram for explaining external features of a bottomed container manufactured by a conventional method for manufacturing a bottomed container, and Fig. 11(B) is a diagram for explaining external features of a bottomed container manufactured by the method for manufacturing a bottomed container of this embodiment. 11(B) is a flowchart showing a method for manufacturing a bottomed container according to a modified example, and is also a flowchart showing multiple press drawing steps performed in a press system according to a modified example. 13A is a cross-sectional plan view of the punch and the die in the die used in the first drawing step, FIG. 13B is a cross-sectional plan view of the punch and the die in the die used in the second drawing step, and FIG. 13C is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13B is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13C is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13D is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13E is a cross-sectional plan view of the punch and the die in the die used in the second drawing step. 13F is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13G is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13H is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13H is a cross-sectional plan view of the punch and the die in the die used in the third drawing step. 13G ...

[0025] Hereinafter, embodiments 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 rectangular cylindrical container by performing multiple press-drawing processes using multiple dies having elongated forming holes to form a workpiece from a flat plate into a rectangular cylindrical container having a bottom. The present invention can also be widely applied to various applications as a press system for forming a rectangular cylindrical container by performing multiple press-drawing processes using multiple dies having elongated forming holes to form a workpiece from a flat plate into a rectangular cylindrical container 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 an embodiment of the present invention will be described, followed by a description of the characteristic configuration of the press system and the method for manufacturing a bottomed container according to an embodiment of the present invention.

[0026] [1. Overview of the Press System] Fig. 1 shows 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, showing an enlarged portion of the transfer press device 50. For ease of explanation, the up-down direction, left-right direction, and front-rear direction are defined as shown in Figs. 1 and 2.

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

[0028] The work supply device 10 is a device that supplies workpieces W (see Figures 4 and 6(A) described below) 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 supply 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 disposed between the pair of side walls 13A, 13B. A drive unit 32 that drives a pair of rails 82A, 82B (see Figure 2) is disposed on the left side of the work supply device 10.

[0029] The ram support wall 14 supports a ram 20 so that it can move up and down, i.e., ascend and descend. The ram 20 receives power from a servo motor (not shown) through a camshaft 22, enabling it to move up and down. The ram 20 also supports a punch (not shown). The left end of the camshaft 22 protrudes outward through the left side wall 13A of a pair of side walls 13A, 13B, which are laterally opposed to each other. The portion protruding outward through the left side wall 13A is connected to the 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. A flywheel 26 is attached to the left end of the camshaft 22, along with the pulley 24. The pulley 24, timing belt (not shown), and flywheel 26 are all 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-tiered structure consisting of an upper tier and a lower tier. The upper surface of the lower tier 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 tier of the die holder 30 is disposed above the upper surface of the lower tier with a gap therebetween. A die (not shown) is held in the upper tier of the die holder 30.

[0031] In the work supply device 10, the ram 20 is moved downward to punch out the sheet metal with a punch and die (not shown) supported by the ram 20, thereby forming a flat work W (see FIGS. 4 and 6A described below). The flat work W formed by the work supply 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 a flat plate state 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 vertically standing side walls 53A, 53B that 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 placed across 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, allowing it to move up and down. The ram 60 also supports a plurality of punches 74 arranged in the left-right direction (i.e., the workpiece conveyance direction). A camshaft 62 extends 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 each other in the left-right direction and protrudes outward. The portion that penetrates the right side wall 53B and protrudes outward is connected to the servo motor (not shown) via a pulley 64 and a timing belt (not shown).

[0036] When the camshaft 62 is driven to rotate 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 other components 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 spans 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 workpiece transfer direction. The number of dies 72 and the number of punches 74 are the same, and a pair of dies 72 and punches 74 arranged vertically constitutes a mold 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 mold used to perform multiple press-drawing processes.

[0038] 1 and 2, the transfer press device 50 includes multiple pairs of dies 72 and punches 74, which are multiple metal molds, arranged along the workpiece conveyance direction. The multiple pairs of dies 72 and punches 74 are arranged at a constant pitch in the left-right direction. Referring to FIG. 2, each die 72 is fixed to a die holder 70. A step portion 70A is formed on 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 has a forming hole 73 that is elongated in a plan view viewed in the vertical direction. Press drawing is performed by having the punch 74 push the workpiece W through the elongated forming hole 73 in the die 72. When the punch 74 presses 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 presses 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 workpiece W from expanding downward. 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 disposed 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 with the left-right direction as the longitudinal direction and extend across the multiple pairs of dies 72 and punches 74. The pair of rails 82A, 82B are arranged parallel to each other with a fixed distance in the front-rear direction. A pair of fingers 84A, 84B and a pair of air cylinders 86A, 86B are mounted on the pair of rails 82A, 82B at positions corresponding to each pair of dies 72 and punches 74 in the vertical direction. Therefore, when the pair of rails 82A, 82B are moved left-right by the drive unit 32 (see FIG. 1), the multiple air cylinders 86A, 86B and the multiple fingers 84A, 84B also move left-right. In this way, the workpiece W clamped between the fingers 84A, 84B can be transported downstream in the workpiece transport direction. Note that FIG. 2 shows the workpiece W clamped between the fingers 84A, 84B.

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

[0043] The spacing between adjacent fingers 84A, 84B in the workpiece transport direction (i.e., the left-right direction) is the same constant pitch as the spacing between adjacent punches 74 (see FIG. 1) and dies 72 in the left-right direction. The drive unit (see FIG. 1) repeatedly reciprocates the pair of rails 82A, 82B in the left-right direction at a constant pitch while maintaining a horizontal position in synchronization with the raising and lowering movement of the ram 60 (see FIG. 1). Furthermore, multiple pairs of air cylinders 86A, 86B repeatedly open and close the fingers 84A, 84B so that the workpiece W is transported by the reciprocating movement of the pair of rails 82A, 82B in the left-right direction. In this manner, the workpiece W is transported by the transfer device 80 from the upstream side (i.e., the left side) in the workpiece transport direction to the downstream side (i.e., the right side) in the workpiece transport direction, and is subjected to press drawing by each of the multiple pairs of dies 72 and punches 74 in turn. This allows the workpiece W to undergo multiple press drawing processes.

[0044] When the press system 1 performs multiple drawing processes on the workpiece W, a number of dies 72 and punches 74 corresponding to the number of drawing processes to be performed are used. Note that the press system 1 illustrated in FIG. 1 exemplifies a configuration in which eight pairs of dies 72 and punches 74 are provided. When eight drawing processes are performed on the workpiece W, eight pairs of dies 72 and punches 74 are used. For example, when two drawing processes are performed on the workpiece W, only two pairs of dies 72 and punches 74 are used. That is, in this case, only two pairs of dies 72 and punches 74 out of the eight pairs of dies 72 and punches 74 are attached to and used in the press system 1, and the other six pairs of dies 72 and punches 74 are not attached to the press system 1. Similarly, for example, when three drawing processes are performed 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. Note that in the places in the press system 1 where the dies 72 are not attached, for example, block-shaped members without forming holes are attached.

[0045] The press system 1 of this embodiment has the above-described basic device configuration and is provided as a press system that forms a rectangular cylindrical bottomed container by performing a plurality of press drawing processes 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. Each of the plurality of dies used in the plurality of press drawing processes performed by the press system 1 is composed of a die 72 and a punch 74. The die 72 of each of the plurality of dies has an elongated forming hole 73.

[0046] The multiple drawing steps performed by the press system 1 may include two drawing steps, or may include three or more drawing steps. FIG. 3 is a flowchart illustrating an example of multiple drawing steps performed by the press system 1. FIG. 3 is also a flowchart illustrating an example of a method for manufacturing a bottomed container according to this embodiment, which will be described later. The flowchart shown in FIG. 3 illustrates an example in which the press system 1 performs two drawing steps as the multiple drawing steps. As illustrated in the flowchart of FIG. 3, the press system 1 is configured to perform a first drawing step S1 and a second drawing step S2. In the example shown in FIG. 3, the first drawing step constitutes the first drawing step S1, and the second and final drawing step constitutes the second drawing step S2. 3 , when two drawing processes are performed as multiple 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 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 workpiece transfer direction, and is equipped with two molds each composed of a die 72 and a punch 74.

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

[0048] The first press unit is configured to perform a first drawing process S1, which is at least one of the multiple drawing processes excluding the final drawing process. As illustrated in the flowchart of Figure 3, when two drawing processes are performed as multiple drawing processes in the press system 1, the first drawing process S1 performed by the first press unit is the first drawing process excluding the final second drawing process. The first drawing process S1 performed by the first press unit is the first drawing process of the multiple drawing processes. When two drawing processes are performed in the press system 1, the first press unit is configured to include one of two dies having a die 72 and a punch 74, which is located upstream in the workpiece transport direction. The first press unit is configured to include a mold located upstream in the workpiece conveyance direction and 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 that serve as a mechanism for raising and lowering the ram 60. As will be described later, the first press unit has a first mold 71A (see FIG. 4) that includes a die 72A having a first forming hole 73A that serves as an elongated forming hole 73.

[0049] The second press unit is configured to perform a second drawing process S2, which is configured as the drawing process subsequent to the first drawing process S1 among the multiple drawing processes. As illustrated in the flowchart of FIG. 3 , when two drawing processes are performed as multiple drawing processes in the press system 1, the second drawing process S2 performed in the second press unit is configured as the final drawing process, which is the drawing process subsequent to the first drawing process S1 as the initial drawing process. When two drawing processes are performed in the press system 1, the second press unit is configured to include one of two dies having a die 72 and a punch 74, which is located downstream in the workpiece transport direction. The second press unit is further configured to include the die downstream in the workpiece transport direction, which is configured as 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 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 the Method for Manufacturing a Bottomed Container] Next, a description will be given of a method for manufacturing a bottomed container according to an embodiment of the present invention. The method for manufacturing a bottomed container according to this embodiment is a method for manufacturing a bottomed container in which a rectangular cylindrical bottomed container is manufactured by performing a plurality of press-drawing processes using a plurality of dies having elongated forming holes to form a workpiece W from a flat plate into a rectangular cylindrical shape having a bottom. The method for manufacturing a bottomed container according to this embodiment is implemented, for example, by performing a plurality of press-drawing processes on the workpiece 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 rectangular cylindrical bottomed container by performing a plurality of press-drawing processes on the workpiece W using a plurality of dies having elongated forming holes 73, each including a die 72 and a punch 74, to form the workpiece W from a flat plate into a rectangular cylindrical shape.

[0051] The method for manufacturing a bottomed container according to this embodiment includes multiple drawing steps. The method for manufacturing a bottomed container according to this embodiment may include two or more drawing steps as the multiple drawing steps. FIG. 3 is a flowchart illustrating an example of a method for manufacturing a bottomed container according to this embodiment. As shown in FIG. 3 , this embodiment illustrates a configuration in which the method for manufacturing a bottomed container according to this embodiment includes multiple drawing steps and a ironing step performed after the multiple drawing steps. The example method for manufacturing a bottomed container shown in FIG. 3 includes a first drawing step S1 and a second drawing step S2. The method for manufacturing a bottomed container illustrated in FIG. 3 includes two drawing steps, with the first drawing step being the first drawing step S1 and the second and final drawing step being the second drawing step S2.

[0052] As shown in FIG. 3 , after the first drawing step S1 and the second drawing step S2 are completed, a ironing step S3 may be performed. The ironing step S3 is performed on a rectangular cylindrical bottomed container manufactured by performing multiple drawing steps after multiple drawing steps have been completed. In the ironing step S3, a metal mold is used to perform ironing on the manufactured rectangular cylindrical bottomed container, reducing the plate thickness of the bottomed container wall to determine the final shape of the product. If the ironing step S3 is not performed after multiple drawing steps, the shape of the bottomed container manufactured through multiple drawing steps will determine the final shape of the product.

[0053] The first drawing step S1 is configured as at least one of the drawing steps excluding the final drawing step among multiple drawing steps. The method for manufacturing a bottomed container shown in Figure 3 is configured as a method for manufacturing a bottomed container that involves two drawing steps, so the first drawing step S1 is configured as the first drawing step excluding the second, final drawing step. In the method for manufacturing a bottomed container shown in Figure 3, the first drawing step S1 is configured as the first drawing step among multiple drawing steps.

[0054] The second drawing step S2 is configured as the drawing step subsequent to the first drawing step S1 among multiple drawing steps. The method for manufacturing a bottomed container shown in FIG. 3 is configured as a method for manufacturing a bottomed container that performs two drawing steps, so the second drawing step S2 is configured as the final drawing step, which is the drawing step subsequent to the first drawing step S1, which is the initial drawing step. The method for manufacturing a bottomed container of this embodiment ends with the first drawing step S1 and the second drawing step S2. As shown in FIG. 3 , after multiple drawing steps are completed, a ironing step S3 may be performed to reduce the thickness of the wall of the bottomed container.

[0055] [3. Characteristic Configurations of First and Second Drawing Steps and First and Second Press Units] Next, a description will be given of the characteristic configurations of the first and second drawing steps of the manufacturing method for a bottomed container according to this embodiment and the first and second press units of the press system 1 according to this embodiment. Figure 4 is a diagram showing an example of a first mold 71A used in the first drawing step S1 in the manufacturing method for a bottomed container shown in Figure 3, and also shows an example of the first mold 71A in the first press unit of the press system 1. Figure 4(A) is a plan cross-sectional view of a punch 74A of the first mold 71A, Figure 4(B) is a plan view of a die 72A of the first mold 71A, and Figure 4(C) is a cross-sectional view taken along line A-A in Figure 4(B). Fig. 5 is a diagram showing an example of a second die 71B used in the second press drawing step S2 in the method for manufacturing 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 cross-sectional plan 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 cross-sectional view taken along the line B-B in Fig. 5(B). Fig. 6 is a diagram for explaining the method for manufacturing a bottomed container of this embodiment and the workpiece W to be subjected to press drawing in the press system 1.

[0056] 4 , the first mold 71A in the first press section of the press system 1, which is used in the first press drawing step S1 of the method for manufacturing a bottomed container of this embodiment, includes 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 in the first press section of the press system 1, and is configured as the die 72 used in the first press drawing step S1 of the method for manufacturing a 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 in the first press section of the press system 1, and is configured as the punch 74 used in the first press drawing step S1 of the method for manufacturing a bottomed container of this embodiment.

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

[0058] For example, each of the first molding hole 73A has a semicircular arc shape at both ends in the longitudinal direction X. The first molding hole 73A is formed such that the shape of the circumferential portion excluding both ends in the longitudinal direction X tapers inward in the width direction Y from both ends in the longitudinal direction X toward the center. That is, the shape of the circumferential portion excluding both ends in the longitudinal direction X of the first molding hole 73A is formed such that the dimension in the width direction Y gradually decreases from both ends in the longitudinal direction X toward the center. The first molding hole 73A is formed such that the shape tapers inward in the width direction Y from both ends in the longitudinal direction X toward 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 inward in the width direction Y at a center position CX in the longitudinal direction X. In Fig. 4(B) , the center 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] 4A, the punch 74A is formed into 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 into a shape corresponding to the first forming hole 73A of the die 72A. Therefore, the punch 74A is formed so that both end portions in a direction parallel to the longitudinal direction X of the first forming hole 73A each have a semicircular cross-sectional shape. The shape of the portion of the punch 74A excluding both end portions of the semicircular cross-sectional shape in the circumferential direction is formed so that it is smoothly curved and concave in an arc shape from both end sides in a direction parallel to the longitudinal direction X of the first forming hole 73A toward the center toward the inside in a direction parallel to the width direction Y of the first forming hole 73A.

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

[0061] In the first drawing process S1 in the method for manufacturing a bottomed container of this embodiment, which is performed by the first press unit of the press system 1, the punch 74A presses the workpiece W1 into the first forming hole 73A of the die 72A, thereby forming the workpiece W1 into a workpiece W2 having a cylindrical shape and a bottom. Note that FIG. 6B shows a perspective view of the workpiece W2 formed through the first drawing process S1. 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. Note that in FIG. 6B, the upper end of the workpiece W2 is schematically shown in a flat state.

[0062] 5 , the second mold 71B in the second press unit of the press system 1, which is used in the second drawing step S2 of the bottomed container manufacturing method 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 in the second press unit of the press system 1, and is also configured as the die 72 used in the second drawing step S2 of the bottomed container manufacturing method 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 in the second press unit of the press system 1, and is also configured as the punch 74 used in the second drawing step S2 of the bottomed container manufacturing method of this embodiment.

[0063] 5(B) and 5(C), the die 72B is provided with a second molding hole 73B as a molding hole 73 having an elongated shape in a plan view in the vertical direction. The second molding hole 73B has an elongated cross-sectional shape and is provided to penetrate the die 72B in the vertical direction. The second molding hole 73B is formed so that the dimension in the longitudinal direction X, which is the direction in which the elongated hole extends, is greater 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-headed arrow X, and the width direction Y is indicated by a double-headed 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 four corners that are arc-shaped. In this embodiment, the second drawing process S2 constitutes the final 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 drawing processes in the bottomed container manufacturing method of this embodiment.

[0065] 5A, the punch 74B is formed into a shape corresponding to the die 72B. That is, the outer peripheral shape of the punch 74B is formed into a shape corresponding to the second forming hole 73B of the die 72B. Therefore, the punch 74B is formed into a substantially rectangular cross-sectional shape that is elongated in a direction parallel to the longitudinal direction X of the 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 an elongated forming hole 73, and the second drawing process S2 is performed using the second mold 71B. Furthermore, the second drawing process S2 in the bottomed container manufacturing method of this embodiment is performed using the second mold 71B including the die 72B having the second forming hole 73B as an elongated forming hole 73 having a substantially rectangular shape. The second drawing process S2 is performed using the die 72B having the second forming hole 73B having a substantially rectangular elongated hole and a punch 74B having a cross-sectional shape corresponding to the second forming hole 73B. In the second drawing process S2, the cylindrical workpiece W2 formed through the first drawing process S1 is subjected to drawing using the die 72B and punch 74B. Note that in FIGS. 5(B) and 5(C), the workpiece W2 is indicated by a two-dot chain line.

[0067] In the second drawing process S2 in the bottomed container manufacturing method of this embodiment, performed by the second press unit of the press system 1, the punch 74B presses the workpiece W2 into the second forming hole 73B of the die 72B, thereby forming the workpiece W2 into a workpiece W3, which is a rectangular cylindrical bottomed container having a bottom. By performing the second drawing process S2, a rectangular cylindrical bottomed container is manufactured by forming the rectangular cylindrical workpiece W3. FIG. 6C shows a perspective view of the rectangular cylindrical bottomed container manufactured by performing the second drawing process S2 and forming the workpiece W3. Note that in FIG. 6C, the upper end of the workpiece W3 is schematically shown in a flat state. In this embodiment, the second drawing process S2 constitutes the final drawing process. Therefore, the workpiece W3 formed through the second drawing step S2 is formed into the shape of a bottomed container manufactured through multiple drawing steps 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 manufactured by being formed as the workpiece W3 through the second drawing step 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 step S1 and the second drawing step 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 describes the relationship between the shapes of the forming hole 73 of the die 72 in the first drawing step S1 and the second drawing step S2 in the method for producing 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 unit that performs the first drawing step S1 and the second press unit that performs the second drawing step S2 in the press system 1. 7 is a diagram illustrating, in comparison, the forming holes 73 of the die 72 used in the first drawing step S1 and the second drawing step S2 in the method for producing a bottomed container according to this embodiment, and is also a diagram illustrating, in comparison, the forming holes 73 of the die 72 used in the first drawing step S1 and the second drawing step S2 performed by the first press unit and the second press unit in the press system 1. That is, in Fig. 7, the first forming hole 73A of the die 72A used in the first drawing step S1 and the second forming hole 73B of the die 72B used in the second drawing step S2 are illustrated, and the first forming hole 73A of the die 72A of the first press unit and the second forming hole 73B of the die 72B of the second press unit in the press system 1 are illustrated, in comparison. Naturally, die 72A and die 72B are not a single die 72 but separate, different dies 72. However, in Figure 7, die 72A and die 72B are shown in a stacked state in order to contrast the first forming hole 73A and the second forming hole 73B.

[0069] 7, the area of ​​the first molding hole 73A is larger than the area of ​​the second molding hole 73B over the entire periphery. That is, when the die 72A and the die 72B are stacked, the outlines of the first molding hole 73A and the second molding hole 73B do not overlap in a plan view, and the second molding hole 73B is positioned inside the first molding hole 73A. Therefore, the first molding hole 73A is formed to have a larger dimension in the width direction Y, which is perpendicular to the longitudinal direction X, over the entire length of the elongated hole in the longitudinal direction X than the second molding hole 73B. Furthermore, the first molding hole 73A is formed to have a larger dimension in the width direction Y than the second molding hole 73B over the entire length in the vertical direction, which is the direction in which the first molding hole 73A penetrates the die 72A. More specifically, the second molding hole 73B has a substantially rectangular shape, and the width dimension YB of the second molding hole 73B in the width direction Y is set to a constant dimension. The width dimension YB of the second molding 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 molding hole 73B penetrates the die 72B. Meanwhile, the semicircular arc-shaped portions of the first molding hole 73A at both ends in the longitudinal direction X are formed to a size that surrounds both longitudinal ends of the second molding hole 73B over the entire length in the up-down direction. Furthermore, the first molding 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, except for both ends in the longitudinal direction X, 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, other than both ends in the longitudinal direction X, at a portion where the dimension in the width direction Y is smallest, 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, which is perpendicular to the longitudinal direction X, that is the direction in which the first molding hole 73A extends like an elongated hole, over the entire length in the vertical direction, than the second molding hole 73B.

[0070] (Functions of First Drawing Step and First Press Unit) Next, we will explain the function of the first drawing step S1 in the method for manufacturing a bottomed container of this embodiment and the function of the first press unit that performs the first drawing step S1 in the press system 1. Note that the following explanation of the functions is an explanation of the function of the first drawing step S1 in the method for manufacturing a bottomed container of this embodiment, and also an explanation of the function of the first press unit that performs the first drawing step S1 in the press system 1. Figure 8 is a diagram for explaining the forces acting on the workpiece W in the first drawing step S1 in the method for manufacturing a bottomed container of this embodiment, and is also a diagram for explaining the forces acting on the workpiece W in the first drawing step S1 performed by the first press unit in the press system 1. 8 schematically shows the workpiece W1, which is the workpiece W in the middle of being drawn by the die 72A and the punch 74A in the first drawing step S1 in the method for manufacturing a bottomed container of this embodiment, and also schematically shows the workpiece W1, which is the workpiece W in the middle of being drawn by the die 72A and the punch 74A of the first press unit in the press system 1. In addition, in FIG. 8, the die 72A and the punch 74A are not shown, and the first forming hole 73A is schematically shown by a two-dot chain line.

[0071] Referring to FIG. 8 , when the first press drawing process S1 begins, 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 processed portions of the workpiece W1 in the semicircular arc-shaped regions on both ends of the first forming hole 73A in the longitudinal direction X. In FIG. 8 and FIG. 10(A) described below, the processed portions of the workpiece W1 on both ends of the first forming hole 73A in the longitudinal direction X are indicated by a dashed line with double-ended arrows P1, and hereinafter, these portions will also be referred to as "both end side processed portions P1." The both end side processed portions P1 of the workpiece W1 are in a state of shrink flange formation, and therefore 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 machined in the central region other than both ends of the first forming hole 73A in the longitudinal direction X. In FIG. 8 and FIG. 10(A) described below, the portion of the workpiece W1 machined in the central region other than both ends of the first forming hole 73A in the longitudinal direction X is indicated by a dashed line with a double-ended arrow P2, and hereinafter this portion will also be referred to as the "center-side processed portion P2." The center-side processed portion P2 of the workpiece W1 is in a stretch flange-formed state, so a tensile force is generated in the circumferential direction.

[0073] As described above, in the first press-drawing process S1, a compressive force is generated in the circumferential direction in the end-side processed portions P1 of the workpiece W1, and a tensile force is generated in the circumferential direction in the central processed portion P2. Therefore, in the workpiece W1, the tensile force in the circumferential direction generated in the central processed portion P2 opposes the compressive force in the end-side processed portion P1. Then, in the workpiece W1, plastic flow occurs smoothly from the end-side processed portions P1, where the compressive force is generated, to the central processed portion P2, where the tensile force is generated. 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. Furthermore, in the first press-drawing process S1, smooth plastic flow occurs from the end-side processed portions P1, where the compressive force is generated, to the central processed portion P2, where the tensile force is generated. This prevents excess material volume in the central processed portion P2, and thus prevents plastic flow toward the bottom of the portion formed into the shape of the workpiece W2. This prevents distortion from occurring on the bottom side of the workpiece W2 in the central portion in the longitudinal direction X when the workpiece W1 is formed into the workpiece W2 through the first press drawing process S1.

[0074] Here, the effect of suppressing the occurrence of distortion in the bottom of the workpiece W2 formed through the first drawing step S1 will be further explained in comparison with a conventional drawing step. Figure 9 is a diagram for explaining the conventional drawing step, in which Figure 9(A) is a plan view of a die 172A, Figure 9(B) is a cross-sectional view showing the state in which the workpiece W101 is drawn to form the workpiece W102, and Figure 9(C) is an enlarged view of the portion D surrounded by a dashed line in Figure 9(B). Note that the conventional drawing step described with reference to Figure 9 constitutes the first drawing step in a conventional method for manufacturing a bottomed container, in which a rectangular cylindrical bottomed container is formed from a flat workpiece W101 by performing multiple drawing steps.

[0075] Referring to FIG. 9 , a conventional press drawing process is performed using a die 172A having an elongated 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 elongated hole extends, is larger than the dimension in the width direction Y, which is the direction perpendicular to the longitudinal direction X. Note that in FIG. 9A , the longitudinal direction X is indicated by a double-headed arrow X, and the width direction Y is indicated by a double-headed arrow Y. The forming hole 173A of the die 172A is formed in a shape that expands outward in an elliptical shape around its entire circumference. The punch 174A is formed in a shape corresponding 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 expands outward in an elliptical shape around its entire circumference, similar to the shape of the forming hole of the die 172A.

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

[0077] In a 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 central processed portion P20. However, since the elongated forming hole 173A, which extends outward in an elliptical shape around the entire circumference, has a larger curvature at both ends in the longitudinal direction X than at the central portion in the longitudinal direction X, the amount of processing in the end-side processed portion P10 is greater than the amount of processing in the central processed portion P20. As a result, plastic flow occurs from the end-side processed portion P10 to the central processed portion P20, resulting in an excess volume of material in the central processed portion P20. As a result, the excess volume of material in the central processed portion P20 plastically flows toward the bottom of the workpiece W102, which is not constrained by the die 172A and 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 of the bottom of the workpiece W102 that has been subjected to press drawing in the longitudinal direction X tends to bulge away from the punch 174A, and distortion tends to occur in the central portion of the bottom of the workpiece W102 in the longitudinal direction X.

[0078] On the other hand, in the first drawing step S1 in the method for producing a bottomed container of this embodiment and the first drawing step S1 performed by the first press unit of the press system 1, distortion of the bottom of the workpiece W2 formed through the first drawing step S1 is suppressed. Figure 10 is a diagram for explaining the first drawing step S1 in the method for producing a bottomed container of this embodiment and the first drawing step S1 performed by the first press unit of the press system 1, in which Figure 10(A) is a plan view showing the die 72A, Figure 10(B) is a cross-sectional view showing the state in which the workpiece W1 is drawn to form the workpiece W2, and Figure 10(C) is an enlarged view of part F surrounded by a dashed line in Figure 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 tapering inward in the width direction Y from both ends in the longitudinal direction X toward the center, and a punch 74A corresponding to the die 72A. In the first press-drawing process S1, a flat workpiece W1 is subjected to a press-drawing process using the die 72A and the punch 74A. The punch 74A then presses the workpiece W1 into the first forming hole 73A of the die 72A, thereby forming the workpiece W1 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 at both end-side processed portions 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, a compressive force is generated in the circumferential direction in the end-side processed portions P1 of the workpiece W1, and a tensile force is generated in the circumferential direction in the central processed portion P2. Therefore, the tensile force in the circumferential direction generated in the central processed portion P2 of the workpiece W1 opposes the compressive force in the end-side processed portion P1. Then, in the workpiece W1, plastic flow occurs smoothly from the end-side processed portions P1, where the compressive force is generated, to the central processed portion P2, where the tensile force is generated. 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 other words, the material that plastically flows from the end-side processed portions P1, where the compressive force is generated, to the central processed portion P2, where the tensile force is generated, is used to form the central processed portion P2 without excess volume in the central processed portion P2. In this way, in the first drawing process S1, plastic flow occurs smoothly from the end-side processed portions P1, where compressive stress is applied, to the central processed portion P2, where tensile stress is applied. This prevents excessive material volume in the central processed portion P2 and suppresses plastic flow toward the bottom of the portion formed into the shape of the workpiece W2. As a result, as shown in Figures 10(B) and 10(C), in the first drawing process S1, the central portion of the bottom of the workpiece W2 in the longitudinal direction X is less likely to separate from the punch 74A and assumes a shape substantially identical to or quite close to the shape of the punch 74A. Therefore, in the first drawing process S1, distortion of the central portion of the bottom of the workpiece W2 in the longitudinal direction X is suppressed.

[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 features 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 features of the manufactured bottomed container. Note that FIG. 11(A) is a diagram for explaining the external features 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 features of the bottomed container W3 manufactured by the method for manufacturing a bottomed container of this embodiment.

[0082] In a conventional method for manufacturing a bottomed container, as shown in FIG. 9 , a flat workpiece W101 is first subjected to a press-drawing process using a die 172A having a forming hole 173A that expands outward in an elliptical shape around the entire circumference, thereby forming a cylindrical workpiece W102 having an elliptical cross-section. The workpiece W102 is then subjected to a press-drawing process using a die (not shown) having a rectangular forming hole with arc-shaped corners, thereby forming a rectangular, bottomed container W103 having a bottom, as shown in FIG. 11(A). The bottomed container W103 manufactured by the conventional method for manufacturing a bottomed container has a thin, linear pattern Q on the side of the bottomed container W103 that curves toward the opening at the top end of the bottomed container W103. Note that FIG. 11(A) shows the pattern Q on the side of the bottomed container W103 only diagrammatically. In the bottomed container W103, there is no distortion in the portion of pattern Q, and pattern Q on the side surface of the bottomed container W103 is revealed by slight differences in the reflection of light on the side surface of the bottomed container W103. In conventional methods for manufacturing bottomed containers, a rectangular cylindrical bottomed container W103 is formed by press-drawing a cylindrical workpiece W102 having an elliptical cross-section, 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 created 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 bottomed container manufacturing method of this embodiment, as shown in Fig. 11(B), a thin linear pattern R appears on the side of the bottomed container W3. The pattern R extends while gently curving along a direction approximately parallel to the longitudinal direction X and slightly curves toward the bottom of the bottomed container W3 in the central portion of the longitudinal direction X. Note that Fig. 11(B) only shows the pattern R on the side of the bottomed container W3. In the bottomed container W3, there is no distortion in the portion of the pattern R, and the pattern R on the side of the bottomed container W3 appears due to slight differences in the reflection of light on the side of the bottomed container W3. In the bottomed container manufacturing method of this embodiment, when the second press-drawing process S2 is performed, the corners of the bottom of the workpiece W2 move toward the side of the bottomed container W3 (workpiece W3) due to plastic flow. Because the corner portions of the bottom of the workpiece W2 have been bent once, when they are moved laterally and flattened in the second drawing process S2, they appear different in appearance from the surrounding unbent portions, and a pattern R appears on the side of the bottomed container W3. Furthermore, because the central portion of the corner portion of the bottom of the workpiece W2 in the longitudinal direction X was formed in the first drawing process S1 so as to narrow inward in the width direction Y, when they are moved laterally and flattened in the second drawing process S2, a thin linear pattern R appears on the side of the bottomed container W3, extending while gently curving along a direction substantially parallel to the longitudinal direction X and curving slightly toward the bottom of the bottomed container W3 in the central portion in the longitudinal direction X, as shown in Figure 11(B) . In this way, the rectangular cylindrical bottomed container W3 manufactured by performing 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 so as to approach the bottom side of the bottomed container W3.

[0084] [2-3. Effects of the Present Embodiment] According to the manufacturing method for a bottomed container and the press system 1 of the present embodiment, the first forming hole 73A is formed so as to narrow inward in the width direction Y from both ends in the longitudinal direction X toward the center, within a range of dimensions in the width direction Y that is larger than the width dimension YB of the second forming hole 73B in the width direction Y. As a result, in the first press drawing process S1, 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 of the workpiece W1 that is processed on the central side of the first forming hole 73A in the longitudinal direction X. Therefore, in the workpiece W1, the circumferential tensile force generated in the central processed portion P2 opposes a compressive force generated in the both end processed portions P1, which are portions of the first forming hole 73A that are processed on both end sides in the longitudinal direction X. This prevents the volume of material processed at the center of the first forming hole 73A in the longitudinal direction X from becoming excessive, thereby preventing plastic flow toward the bottom of the workpiece W2. Furthermore, the first forming hole 73A is formed so as to narrow inward in the width direction Y from both ends in the longitudinal direction X to the center over its entire length in the vertical direction, within a range of dimensions in the width direction Y that is larger than the width dimension YB of the second forming hole 73B. Therefore, the force acting on the workpiece W1 at both ends and the center of the first forming hole 73A in the longitudinal direction X is adjusted throughout the first drawing process S1, preventing the volume of material processed at the center of the first forming hole 73A in the longitudinal direction X from becoming excessive over its entire length in the vertical direction, thereby preventing plastic flow toward the bottom of the workpiece W2. Then, in the second press-drawing process S2, the workpiece W2, which has been prevented from becoming excessively large at the center in the longitudinal direction X and has been prevented from plastically flowing toward the bottom, passes through the second forming hole 73B, which is smaller in dimension in the width direction Y than the first forming hole 73A, and is press-drawn to be formed into a rectangular cylindrical shape. In this way, the workpiece W is finally formed into the workpiece W3 in a rectangular cylindrical shape.Thus, according to the bottomed container manufacturing method and press system 1 of this embodiment, in the first press-drawing process S1, the workpiece W is press-formed while preventing excess volume at the center in the longitudinal direction X and suppressing plastic flow toward the bottom. In the second press-drawing process, the workpiece W is pressed in the width direction Y to form a rectangular tube. Therefore, the bottomed container manufacturing method and press system 1 of this embodiment can prevent distortion from occurring at the bottom side of the central portion in the longitudinal direction X of the workpiece W. Furthermore, in the bottomed container manufacturing method and 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 end-side processed portions P1, making it difficult for buckling to occur in the central processed portion P2 and reducing the occurrence of wrinkles. Furthermore, the bottomed container manufacturing method and press system 1 of this embodiment can prevent distortion from occurring at the bottom side of the workpiece W. Therefore, when the scraping process S3 is performed, distortion of the wall of the bottomed container serving as the workpiece W after the scraping process S3 is performed can be suppressed, and dimensional abnormalities in the corners of the bottom of the bottomed container can also be suppressed.

[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 molds with long hole-shaped forming holes 73, the workpiece W is shaped from a flat plate into a rectangular cylindrical shape having a bottom, thereby making it possible to prevent distortion from occurring on the bottom side of the workpiece W when manufacturing a rectangular cylindrical bottomed container.

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

[0087] Furthermore, in the bottomed container manufacturing method and press system 1 of this embodiment, the first forming hole 73A is formed so that it curves and narrows inward in the width direction Y from both end sides in the longitudinal direction X to the center, and is narrowest inward in the width direction Y at the center position CX in the longitudinal direction X. As a result, with the bottomed container manufacturing method and press system 1 of this embodiment, a circumferential tensile force can be generated in the center processed portion P2 so as to more evenly counter the circumferential compressive force generated in the both end processed portions P1. This makes it possible to more efficiently suppress distortion on the bottom side of the workpiece W.

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

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

[0090] The method for manufacturing a bottomed container of this modified example is configured to include three drawing steps as the multiple drawing steps. The press system of this modified example is configured to perform three drawing steps as the multiple drawing steps. That is, as shown in FIG. 12 , the method for manufacturing a bottomed container of this modified example is configured to include a first drawing step S11, a second drawing step S12, and a third drawing step S13. The press system of this modified example is configured to perform the first drawing step S11, the second drawing step S12, and the third drawing step S13. The first drawing step S11 is the first drawing step. The second drawing step S12 is the drawing step performed after the first drawing step S11. The third drawing step S13 is the final drawing step performed after the second drawing step S12. 12 does not illustrate 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 bottomed container wall.

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

[0092] The second drawing process S12 is the drawing process subsequent to the first drawing process among the multiple drawing processes in the manufacturing method of a bottomed container of this modified example, and constitutes the second drawing process of the present invention. The second drawing process S12 is the drawing process subsequent to 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 second drawing process S12 is the drawing process subsequent to the first drawing process S11 as the first drawing process, and constitutes the second drawing process. Furthermore, the second drawing process S12 constitutes the second drawing process relative to the first drawing process S11, but constitutes the first drawing process relative to the third 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 from among the multiple press drawing processes, and constitutes the first press drawing process in the present invention in relation to the third press drawing process S13.

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

[0094] Figure 13 shows an example of a mold used in the drawing process in the bottomed container manufacturing method of this modified example, as well as an example of a mold in the press system of this modified example. More specifically, Figure 13(A) is a plan view of punch 74C and die 72C in mold 71C used in the first drawing process S11. Figure 13(B) is a plan view of punch 74D and die 72D in mold 71D used in the second drawing process S12. Figure 13(C) is a plan view of punch 74E and die 72E in mold 71E used in the third drawing process S13. Note that each of the dies 72C to 72E used in the first to third drawing processes S11 to S13 is provided with an elongated forming hole 73. In Figures 13(A) to (C), the longitudinal direction X, which is the direction in which the molding hole 73 extends in the form of an elongated hole, is indicated by a double-headed arrow X, and the width direction Y, which is the direction perpendicular to the longitudinal direction X, is indicated by a double-headed arrow Y.

[0095] 13A, the mold 71C used in the first drawing press 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 drawing press 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 drawing press process S11.

[0096] 13A , 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 whose dimension in the longitudinal direction X is larger than its dimension in the width direction Y and whose shape is long in a plan view. The molding hole 73C has, for example, a semicircular arc at each of its both ends in the longitudinal direction X. The molding hole 73C is formed such that the shape of the circumferential portion excluding both ends in the longitudinal direction X tapers inward in the width direction Y from both ends in the longitudinal direction X toward the center. That is, the molding hole 73C is formed such that the dimension in the width direction Y of the circumferential portion excluding both ends in the longitudinal direction X gradually decreases from both ends in the longitudinal direction X toward the center. The molding hole 73C is formed such that the shape tapers inward in the width direction Y from both ends in the longitudinal direction X toward 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 molding hole 73C is formed so as to narrow from both ends in the longitudinal direction X to the center toward the inside in the width direction Y while curving smoothly in an arc shape.

[0097] 13A, 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 end portions in a direction parallel to the longitudinal direction X of the forming hole 73C each have a semicircular cross-sectional shape. The shape of the portion of the punch 74C excluding both end portions of the semicircular cross-sectional shape in the circumferential direction is formed so that it is smoothly curved and recessed in an arc shape from both end sides in a direction parallel to the longitudinal direction X of the forming hole 73C toward the center toward the inside in a direction parallel to the width direction Y of the forming hole 73C.

[0098] The first drawing step S11 constitutes a first drawing step. 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 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 drawing process S11, a workpiece W11 in a flat plate state, which is supplied from the workpiece supply device 10 of the press system 1, is subjected to drawing using a die 72C and a punch 74C. Note that in FIG. 13(A), the flat plate state workpiece W11 is indicated by a two-dot chain line. In the first drawing process S11, the punch 74C presses the workpiece W11 into the forming hole 73C of the die 72C, thereby forming the workpiece W11 into a workpiece W12 (see FIG. 13(B)) in a cylindrical shape 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, and in Figure 13 (B) the workpiece W12 as viewed in a plan view is shown by a dotted line.

[0100] 13(B), the mold 71D used in the second drawing press 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 drawing press 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 drawing press process S12.

[0101] 13(B) , 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 the molding hole 73D, which has a dimension in the longitudinal direction X that is larger than the dimension in the width direction Y and is formed into a long-hole shape in a plan view. The molding hole 73D has, for example, both ends in the longitudinal direction X that are formed in a semicircular arc shape. The molding hole 73D is formed so that the shape of the circumferential portion excluding both ends in the longitudinal direction X narrows smoothly and in an arc shape from both ends in the longitudinal direction X toward the center toward the inside in the width direction Y. The molding hole 73D is formed so that it narrows inward in the width direction Y from both ends in the longitudinal direction X toward the center over its entire length in the up-down direction, which is the direction in which the molding hole 73D penetrates the die 72D. The forming hole 73D is also 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 drawing step 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 drawing step 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 drawing step S12, and is also 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 end portions in a direction parallel to the longitudinal direction X of the forming hole 73D each have a semicircular cross-sectional shape. The shape of the portion of the punch 74D excluding both end portions of the semicircular cross-sectional shape in the circumferential direction is formed so that it is smoothly curved and recessed in an arc shape from both end sides in a direction parallel to the longitudinal direction X of the forming hole 73D toward the center toward the inside in a direction parallel to the width direction Y of the forming hole 73D.

[0103] The second drawing process S12 constitutes a second drawing process relative to the first drawing process S11, which serves as a first drawing process. Therefore, in relation to the first drawing process S11, the forming hole 73D constitutes a second forming hole of the present invention, and the mold 71D, which has the die 72D with the forming hole 73D as the second forming hole and the punch 74D corresponding to the die 72D, constitutes a second mold of the present invention. Furthermore, the second drawing process S12 constitutes a first drawing process relative to the third drawing process S13, which serves as a second drawing process. Therefore, in relation to the third drawing process S13, the forming hole 73D constitutes a first forming hole of the present invention, and the mold 71D, which has the die 72D with the forming hole 73D as the first forming hole and the punch 74D corresponding to the die 72D, constitutes a first mold of the present invention.

[0104] The second drawing process S12 is performed using a die 71D as a second die having a forming hole 73D as a second forming hole, as compared to the first drawing process S11. Similarly, the second drawing process S12 is performed using a die 71D as a first die having a forming hole 73D as a first forming hole, as compared to the third drawing process S13. In the second drawing process S12, the cylindrical workpiece W12 formed through the first drawing process S11 is subjected to drawing using a die 72D and a punch 74D. In the second drawing process S12, the punch 74D presses the workpiece W12 into the forming hole 73D of the die 72D, thereby forming the workpiece W12 into a cylindrical workpiece W13 (see FIG. 13(C)). The workpiece W13 formed through the second press drawing process S12 has a bottom with an 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 mold 71E used in the third drawing step 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 drawing step 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 drawing step S13.

[0106] 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 whose dimension in the longitudinal direction X is larger than its dimension in the width direction Y and which is formed in a long-hole shape in a plan view. The forming hole 73E is formed in a substantially rectangular shape that is 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. Furthermore, the forming hole 73E is formed to have a smaller dimension in the width direction Y across the longitudinal direction X than the forming hole 73D of the die 72D used in the second press drawing process S12. Furthermore, the forming hole 73E is formed to have a smaller dimension in the width direction Y than the forming hole 73D across 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 step S12 is larger in dimension in the width direction Y over the longitudinal direction X and over the entire length in the vertical direction than the forming hole 73E of the die 72E used in the third drawing step S13. Note that in this modified example, the third drawing step S13 constitutes the final drawing step. Therefore, the shape of the forming hole 73E corresponds to the cross-sectional shape of the rectangular cylindrical bottomed container that is finally manufactured through multiple drawing steps in the bottomed container manufacturing method of this modified example.

[0107] 13(C), the punch 74E has an outer peripheral shape formed to correspond 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 step S13 constitutes a second drawing step in comparison with the second drawing step S12, which serves as a first drawing step. 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 drawing process S13 is performed using a die 71E as a second die having a forming hole 73E as a second forming hole, as compared to the second drawing process S12. In the third drawing process S13, the cylindrical workpiece W13 formed through the second drawing process S12 is subjected to drawing using a die 72E and a punch 74E. In the third drawing process S13, the punch 74E presses the workpiece W13 into the forming hole 73E of the die 72E, thereby forming the workpiece W13 into a rectangular cylindrical bottomed container having a bottom. By performing the third drawing process S13, a rectangular cylindrical bottomed container is produced as the rectangular cylindrical workpiece W. In this modified example, the third drawing process S13 constitutes the final 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 holes 73 of the die 72 in the first drawing step S11, the second drawing step S12, and the third drawing step S13 will be further described. Figure 14 is a diagram comparing and schematically illustrating the forming holes 73 of the die 72 used in multiple drawing steps in a method for producing a bottomed container according to a modified example, and is also a diagram comparing and schematically illustrating the forming holes 73 of the die 72 used in multiple drawing steps performed in a press system according to a modified example. More specifically, Figure 14 compares and schematically illustrates the forming holes 73C of the die 72C used in the first drawing step S11, the forming holes 73D of the die 72D used in the second drawing step S12, and the forming holes 73E of the die 72E used in the third drawing step S13. 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 compare forming holes 73C, 73D, and 73E.

[0111] First, the relationship between the shapes of the forming hole 73C of the die 72C used in the first drawing step S11 and the forming hole 73D of the die 72D used in the second drawing step S12 will be described. In the relationship between the first drawing step S11 as the first drawing step and the second drawing step S12 as the second drawing step, the forming hole 73C constitutes the first forming hole, and the forming hole 73D constitutes the second forming hole. Referring to FIG. 14 , the area of ​​the forming hole 73C constituting the first forming hole is larger around the entire periphery 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 positioned inside the forming hole 73C. For this reason, 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 along the longitudinal direction X. 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 along its entire length in the up-down 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 surround, along its entire length in the up-down direction, the semicircular arc-shaped portions at both ends of the forming hole 73D in the longitudinal direction X. Furthermore, the portions of the forming hole 73C that taper inward in the width direction Y from both ends in the longitudinal direction X to the center are formed so that they surround, along their entire length in the up-down direction, the portions of the forming hole 73C that taper inward in the width direction Y from both ends in the longitudinal direction X to the center. 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 shapes of the forming hole 73D of the die 72D used in the second drawing step S12 and the forming hole 73E of the die 72E used in the third drawing step S13 will be described. In the relationship between the second drawing step S12 (the first drawing step) and the third drawing step S13 (the second drawing step), the forming hole 73D constitutes the first forming hole, and the forming hole 73E constitutes the second forming hole. Referring to FIG. 14 , the area of ​​the forming hole 73D constituting the first forming hole is larger around the entire periphery than the area of ​​the forming hole 73E constituting the second forming hole. That is, when 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 positioned inside the forming hole 73D. For this reason, the forming hole 73D constituting the first forming hole is formed to have a larger dimension in the width direction Y across 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 across the entire length in the up-down 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 of the forming hole 73E in the width direction Y is set to a constant dimension. The width dimension YE of the forming hole 73E is set to a constant dimension across the entire length in the up-down direction, which is the direction in which the forming hole 73E penetrates the die 72E. Meanwhile, the semicircular arc-shaped portions of the forming hole 73D at both ends in the longitudinal direction X are formed to be large enough to surround both longitudinal ends of the forming hole 73E from the outside across the entire length in the up-down direction. Furthermore, in the circumferential direction, excluding both ends in the longitudinal direction X, the molding hole 73D 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 vertical length, and has the smallest width dimension YD at the center position in the longitudinal direction X. The width dimension YD of the molding hole 73D at the portion 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 molding 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 of this modified example described above, the forming hole 73C of the die 72C used in the first drawing process S11 is formed so as to narrow inward in the width direction Y from both ends in the longitudinal direction X toward the center, within 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 drawing process S12. As a result, in the first drawing process S11, a tensile force is generated in the circumferential direction of the forming hole 73C in the portion of the workpiece W11 machined near the center of the forming hole 73C in the longitudinal direction X. Therefore, the tensile force generated in the portion of the workpiece W11 machined near the center of the forming hole 73C in the longitudinal direction X opposes the compressive force generated in the portion of the workpiece W11 machined near both ends of the forming hole 73C in the longitudinal direction X. This prevents the volume of material machined near the center of the forming hole 73C from becoming excessive, thereby suppressing plastic flow toward the bottom of the workpiece W12. Therefore, it is possible to prevent distortion from occurring on the bottom side of the central portion of the workpiece W12 in the longitudinal direction X.

[0114] Furthermore, in the manufacturing method and press system for a bottomed container according to this modified example, the forming hole 73D of the die 72D used in the second drawing process S12 is formed so as to narrow inward in the width direction Y from both ends in the longitudinal direction X toward the center, within 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 drawing process S13. As a result, in the second drawing process S12, a tensile force is generated in the circumferential direction of the forming hole 73D in the portion of the workpiece W12 machined near the center of the forming hole 73D in the longitudinal direction X. Therefore, the tensile force generated in the portion of the workpiece W12 machined near the center of the forming hole 73D in the longitudinal direction X opposes the compressive force generated in the portion of the workpiece W12 machined near both ends of the forming hole 73D in the longitudinal direction X. This prevents the volume of material machined near the center of the forming hole 73D from becoming excessive, thereby suppressing plastic flow toward the bottom of the workpiece W13. Therefore, it is possible to prevent distortion from occurring on the bottom side of the central portion of the workpiece W13 in the longitudinal direction X.

[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 molds with long hole-shaped forming holes 73 to shape the workpiece W from a flat plate into a rectangular cylindrical shape with a bottom, it is possible to prevent distortion from occurring on the bottom side of the workpiece W when manufacturing a rectangular cylindrical bottomed container.

[0116] The above describes 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 modifications within the scope of the claims.

[0117] For example, the first and second drawing steps described in the above-described embodiment and modified examples are not limited to methods and press systems for manufacturing bottomed containers that perform two or three drawing steps, but can also be applied to methods and press systems for manufacturing bottomed containers that perform four or more drawing steps. Furthermore, the first and second drawing steps described in the above-described embodiment and modified examples are not limited to methods for performing multiple drawing steps using a press system 1 having a transfer press device 50 with multiple dies, but can also be applied to a press system including multiple single-shot presses, each equipped with a die, that performs multiple drawing steps. In a press system including multiple single-shot presses that performs multiple drawing steps, the workpiece may be transported between the multiple presses by an operator or by a workpiece transport device.

[0118] 1 Press system 71A First die 71B Second die 72, 72A, 72B Die 73 Forming hole 73A First forming hole 73B Second forming hole W, W1, W2, W3 Workpiece S1 First press drawing process S2 Second press drawing process

Claims

1. A method for manufacturing a bottomed container, which uses a plurality of dies having elongated forming holes to perform a plurality of press drawing steps to shape a workpiece from a flat state into a bottomed angular tubular state, thereby producing a bottomed angular tubular container, the method comprising: a first press drawing step, which is performed using a first die including a die having a first forming hole as the elongated forming hole and a punch for pressing the workpiece into the first forming hole, and which is configured as at least one press drawing step of the plurality of press drawing steps excluding a final press drawing step; and a second press drawing step, which is performed using a second die having a second forming hole as the elongated forming hole, and which is configured as the press drawing step subsequent to the first press drawing step of the plurality of press drawing steps, the first forming hole being formed to have a larger dimension in the width direction, which is the direction perpendicular to the longitudinal direction in which the first forming hole extends like an elongated hole, than the second forming hole, over the entire length in the up-down direction, which is the direction in which the first forming hole penetrates the die, a first forming hole 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 vertical direction, an outer peripheral shape of the punch formed to correspond to the first forming hole, and a cross-sectional shape of the punch formed so as to curve and concave toward the inside in the direction parallel to the width direction from both ends in the direction parallel to the longitudinal direction to the center.

2. A method for manufacturing a bottomed container as described in claim 1, characterized in that the first press-drawing process is configured as the first press-drawing process of the multiple press-drawing processes.

3. A method for manufacturing a cylindrical bottomed container as described in claim 1 or claim 2, characterized in that the first molding hole is curved and narrowed toward the inside in the width direction from both ends in the longitudinal direction to the center, and is formed so as to be narrowest toward the inside in the width direction at the center position in the longitudinal direction.

4. A press system for forming a rectangular cylindrical bottomed container by performing a plurality of press drawing steps using a plurality of dies having elongated forming holes to form a work from a flat state into a rectangular cylindrical state having a bottom, the press system comprising: a first press section having a first die including a die having a first forming hole as the elongated forming hole and a punch for pressing the work into the first forming hole, the first press drawing step being configured as at least one of the plurality of press drawing steps excluding a final press drawing step among the plurality of press drawing steps, using the first die; and a second press section having a second die having a second forming hole as the elongated forming hole, the second press drawing step being configured as the press drawing step subsequent to the first press drawing step among the plurality of press drawing steps, using the second die. a press system characterized in that: the first forming hole is formed to have a larger width dimension, which is a direction perpendicular to the longitudinal direction in which the first forming hole extends like an elongated hole, than the second forming hole, over its entire length in the up-down direction, which is the direction in which the first forming hole penetrates the die; the first forming hole is formed to narrow toward the inside in the width direction from both ends in the longitudinal direction to the center, over its entire length in the up-down direction; the outer peripheral shape of the punch is formed in a shape corresponding to the first forming hole, and the cross-sectional shape of the punch is formed to be curved and concave toward the inside in the direction parallel to the width direction from both ends in the direction parallel to the longitudinal direction to the center.

5. The press system described in claim 4, characterized in that the first press section performs the first press drawing process, which is the first press drawing process of the multiple press drawing processes, using the first die.

6. A press system as described in claim 4 or 5, characterized in that the first molding hole is curved and narrowed toward the inside in the width direction from both ends in the longitudinal direction to the center, and is formed so as to be narrowest toward the inside in the width direction at the center position in the longitudinal direction.

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