Method of manufacturing tubular product and transfer press

Abstract

To provide a technology capable of manufacturing a cylindrical product having higher shape quality than before.SOLUTION: The manufacturing method of the present disclosure is a manufacturing method in which a cylindrical product 90 is manufactured by punching a bottom wall 92 from a cylindrical intermediate formed product 91 having the non-circular bottom wall 92, wherein a punching preparation step is provided before a punching step, and in the punching preparation step, the bottom wall 92 is press-formed into a shape having an annular sheared portion 95 having inner and outer surfaces intersecting a pressing direction, and a bulging portion 94 surrounded by the annular sheared portion 95. Then, in the punching step, the annular sheared portion 95 is sheared and the bottom wall 92 is punched out.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present disclosure relates to a manufacturing method for manufacturing a cylindrical product by press working and a transfer press machine used in the manufacturing method. [Background technology]

[0002] A conventional method for manufacturing this type of cylindrical product is to press-mold a cylindrical intermediate molded product with a bottom at one end, and then punch out the bottom wall of the intermediate molded product to produce the cylindrical product (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 63-194824 (Figure 1) Summary of the Invention [Problem to be solved by the invention]

[0004] However, in conventional manufacturing methods, when the bottom wall of the intermediate molded product is non-circular, the shape quality of the end of the tubular product after the bottom wall is punched out can be poor. In response to this, this application discloses a technology that can manufacture tubular products with higher shape quality than conventional methods. [Means for solving the problem]

[0005] A first aspect of the invention of the present disclosure is a manufacturing method for producing a tubular product by punching out a non-circular bottom wall from an intermediate molded product, which is a cylindrical press-molded product having the bottom wall, the method comprising: a punching preparation process in which the bottom wall is press-molded into a shape having an annular sheared portion with inner and outer surfaces that intersect with the press direction, and a bulge portion surrounded by the annular sheared portion; and a punching process in which the annular sheared portion is sheared to punch out the bottom wall.

[0006] A second aspect of the invention of the present disclosure is a transfer press machine having a plurality of processing stages lined up in a horizontal row, in which a workpiece is moved sequentially to one side of the horizontal direction and processed at each of the processing stages, the plurality of processing stages including a plurality of processing stages for a cylindrical body forming process in which a flat plate is squeezed multiple times to form a cylindrical intermediate molded product having a non-circular bottom wall, one or more processing stages for a punching preparation process in which the bottom wall of the intermediate molded product is formed into a shape having an annular sheared portion having inner and outer surfaces that intersect with the press direction and a bulge portion surrounded by the annular sheared portion, and a processing stage for a punching process in which the annular sheared portion is sheared to punch out the bottom wall. [Effects of the Invention]

[0007] When the bottom wall of a press-formed intermediate product is noncircular, it is difficult to achieve uniform material flow between the side walls and the bottom wall during press forming, which can easily result in differences in wall thickness of the side walls. In contrast, in the first and second aspects of the present disclosure, a bulge is formed in the bottom wall before it is punched out of the intermediate product. This allows excess material on the bottom wall to be absorbed by the bulge, increasing the material flowability between the side walls and the bottom wall of the intermediate product. This results in a uniform wall thickness of the side walls of the intermediate product. Furthermore, the annular sheared portion of the bottom wall around the bulge is sheared to punch out the bottom wall and form a cylindrical product, thereby improving the uniformity of the wall thickness of the side walls of the cylindrical product compared to conventional methods. In other words, the first and second aspects of the present disclosure enable the production of cylindrical products with higher shape quality than conventional methods. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view of a transfer press according to a first embodiment. [Figure 2] Figure 2 is a perspective view of a cylindrical product. [Figure 3] FIG. 3A is a side view of the intermediate molded product before the punching preparation step, FIG. 3B is a side view of the intermediate molded product after the punching preparation step, and FIG. 3C is a side view of the cylindrical product and the punched bottom wall. [Figure 4] Figure 4 is a side cross-sectional view of the processing stage for the punching preparation process. [Figure 5] FIG. 5A is a bottom view of the intermediate molded product, and FIG. 5B is a cross-sectional plan view of the processing stage in the punching preparation step. [Figure 6] FIG. 6A is a side cross-sectional view of the processing stage for the punching process, and FIG. 6B is a side cross-sectional view of the processing stage for the punching process immediately after punching the bottom wall. [Figure 7] FIG. 7A is a side view of an intermediate molded product before a first punching preparation step in a manufacturing method according to a second embodiment, FIG. 7B is a side view of the intermediate molded product after the first punching preparation step, FIG. 7C is a side view of the intermediate molded product after the second punching preparation step, and FIG. 7D is a side view of a cylindrical product and a punched bottom wall. [Figure 8] FIG. 8 is a side cross-sectional view of a processing stage for the first punching preparation step. [Figure 9] FIG. 9 is a side cross-sectional view of a processing stage for the second punching preparation step. DETAILED DESCRIPTION OF THE INVENTION

[0009] [First embodiment] 1 to 6, a transfer press 10 for manufacturing a cylindrical product 90 according to the present disclosure and a manufacturing method for the cylindrical product 90 will be described. As shown in FIGS. 1, 4, and 6A, the transfer press 10 of this embodiment includes a plurality of processing stages S arranged in a horizontal row, each having punches 21, 22 and dies 31, 32, and a workpiece is transported to one side in the horizontal direction by a transfer device 11 and press-processed at each processing stage S. Hereinafter, the upstream end of the transfer device 11 in the transport direction (the left end in FIG. 1) will be simply referred to as the "upstream end," and the downstream end will be simply referred to as the "downstream end." A manufacturing method for a cylindrical product 90 (see FIG. 2) using this transfer press 10 will be described.

[0010] To manufacture the cylindrical product 90, in the processing stage S at the upstream end of the transfer press 10, for example, an oval blank is punched out of sheet metal and then drawn to form a cylindrical workpiece (not shown) with an oval cross section. The workpiece is then drawn multiple times in multiple processing stages S up to the second downstream end, increasing its axial length and gradually changing its cross-sectional shape into a rectangle that is smaller than the oval. After the workpiece has been press-formed up to the processing stage S two stages before the downstream end, it becomes a cylindrical press-formed product with a rectangular cross-sectional shape and a bottom at one end.

[0011] Next, in the processing stage S just before the downstream end, the workpiece is subjected to press processing in preparation for punching, as described below, and in the processing stage S at the downstream end, the bottom wall of the workpiece is punched out to form a cylindrical product 90, which is then ejected from the transfer press machine 10.

[0012] Hereinafter, the work before the press processing for punching preparation is performed will be referred to as the "intermediate molded product 91," the process and processing stage S in which the press processing for punching preparation is performed on the intermediate molded product 91 will be referred to as the "punching preparation process" and the "processing stage S for the punching preparation process," and the process and processing stage S in which the bottom wall 92 is punched out from the intermediate molded product 91 will be referred to as the "punching process" and the "processing stage S for the punching process."

[0013] The shape of the blank and the cross-sectional shape of the cylindrical workpiece formed by drawing the blank are not limited to ellipse, but may be, for example, circular, oval, polygonal, etc. Furthermore, the positions of the processing stages S until a cylindrical press-formed product with a rectangular cross section is produced, and the positions of the processing stages S where the punching preparation process and the punching process are performed, are not limited to the downstream end, the downstream end, or the downstream end, but may be any positions as long as they are set according to the final shape and size of the cylindrical product 90. Furthermore, a correction process, for example, may be sandwiched between the processing stage S where a cylindrical press-formed product with a rectangular cross section is produced and the processing stage S for the punching preparation process, and between the processing stage S for the punching preparation process and the processing stage S for the punching process.

[0014] As shown in Figures 3A and 3B, which compare the intermediate molded product 91 before and after the punching preparation process, in the punching preparation process, the bottom wall 92 of the intermediate molded product 91 is formed into a two-tiered bottom shape having a bulge portion 94.

[0015] Specifically, as shown in Fig. 3B, the entire periphery of the lower end of the intermediate molded product 91 after the punching preparation step is provided with an inclined surface 93A that tapers downward. The outline of the bottom wall 92 of the intermediate molded product 91 after the punching preparation step, when viewed from below in plan view (i.e., the bottom surface shape), is a rectangle having a pair of long sides and a pair of short sides with R-chamfered corners, as shown in Fig. 5A. In contrast, the outline of the planar shape of the bulging portion 94 is a rectangle that is approximately similar to the outline of the planar shape of the bottom wall 92, and the pair of long sides are curved so as to move away from the pair of long sides of the outline of the bottom wall 92.

[0016] More specifically, as shown in Fig. 4, the bulging portion 94 has a bulging bottom wall 94B that is perpendicular to the pressing direction and bulging side walls 94A that stand upright from the four sides of the bulging bottom wall 94B. As shown in Fig. 5A, the bulging side walls 94A on one of the long sides are curved to bulge inward. As shown in Fig. 4, the inner and outer surfaces of the bulging side walls 94A are generally parallel to the pressing direction, and the entire outer surface of the bulging portion 94 is located inside the inner surfaces of the side walls 93 of the intermediate molded product 91. Furthermore, the bulging bottom wall 94B and the bulging side walls 94A may have, for example, approximately the same thickness, or the bulging bottom wall 94B may be slightly thicker.

[0017] The portion of the bottom wall 92 outside the bulging portion 94 forms an annular sheared portion 95 having inner and outer surfaces that intersect with the pressing direction. Specifically, the annular sheared portion 95 has an inner flat surface 95A and an outer flat surface 95B that are perpendicular to the pressing direction. The outer edge of the outer flat surface 95B is connected to the inclined surface 93A of the side wall 93 of the intermediate molded product 91 via a curved corner surface 95R1 with an extremely small corner radius, and the inner edge of the outer flat surface 95B is connected to the outer surface of the bulging side wall 94A via a curved corner surface 95R2 with a relatively large corner radius.

[0018] Meanwhile, the inner flat surface 95A and the inner surface of the upper part of the bulging side wall 94A are connected by an S-shaped curved surface 94S. The S-shaped curved surface 94S curves outward from the upper part of the inner surface of the bulging side wall 94A, then curves upward and intersects with the inner flat surface 95A. The inner flat surface 95A and the inner surface of the side wall 93 of the intermediate molded product 91 are connected by a corner curved surface 95R3, which has a larger corner R than the connection between the outer flat surface 95B and the outer surface of the side wall 93 of the intermediate molded product 91.

[0019] Here, the entire annular sheared portion 95 includes the corner curved surfaces 95R1 to 95R3 connected to the inner flat surface 95A or the outer flat surface 95B. More specifically, in the present disclosure, the annular sheared portion 95 is located around the bulging portion 94, and as long as it can be sheared in the processing stage S for the punching step described below, the inner and outer surfaces of the annular sheared portion 95 may be partially or entirely inclined with respect to the pressing direction. To achieve this, the angle of the portions of the inner and outer surfaces of the annular sheared portion 95 that intersect with the shearing plane with respect to the pressing direction needs to be 45 to 90 degrees.

[0020] The punch 21, die 31 and counter punch 41 of the processing stage S for the punching preparation step shown in FIG. 4 are configured as follows.

[0021] The punch 21 has a shape in which a punch extension 21Y extends from a lower surface 21B of a prismatic punch main body 21X. The planar cross-sectional shape of the punch extension 21Y is shown in Fig. 5B and is a rectangle roughly similar to the planar cross-sectional shape (not shown) of the punch main body 21X, with a pair of long sides curved to be concave. In other words, a pair of long sides of the planar cross-sectional shape of the side surface 21C of the punch extension 21Y are curved surfaces.

[0022] 4, the lower surface 21B of the punch main body 21X and the lower surface 21D of the punch extension 21Y are each flat surfaces perpendicular to the pressing direction. The lower surface 21B of the punch main body 21X and the side surface 21A, the lower surface 21B of the punch main body 21X and the side surface 21C of the punch extension 21Y, and the side surface 21C of the punch extension 21Y and the lower surface 21D are connected by corner curved surfaces 21R1, 21R2, and 21R3, respectively, and the radius of curvature of the corner curved surface 21R1 between the lower surface 21B of the punch main body 21X and the side surface 21A is smaller than the other corner curved surfaces 21R2 and 21R3.

[0023] A flat step surface 31C that faces upward and is perpendicular to the pressing direction is provided midway through the forming hole 31Z of the die 31. The forming hole 31Z above the step surface 31C is provided with an inner surface 31A that is a square tube with a flat cross section into which the intermediate formed product 91 can be fitted, and an inclined side surface 31B that narrows at its lower end.

[0024] As shown in FIG. 5B, the planar cross-sectional shape of the forming hole 31Z below the step surface 31C is a rectangle that is generally similar to the planar cross-sectional shape (not shown) of the portion above the step surface 31C, and one of the long sides is curved to bulge. That is, the portion of the forming hole 31Z below the step surface 31C has a side surface 31D that is a square tube that is generally similar to the side surface 21C of the punch extension portion 21Y. Furthermore, as shown in FIG. 4, the side surface 31D and the step surface 31C are connected by a corner curved surface 31R1.

[0025] The counter punch 41 is shaped like a rectangular pillar, and its cross-sectional shape is either the same as the cross-sectional shape of the part of the forming hole 31Z below the step surface 31C, or a rectangle with four straight sides that fits exactly inside the cross-sectional shape.

[0026] The punch 22, punch die 32 and guide die 42 of the processing stage S for the punching step shown in FIGS. 6A and 6B are configured as follows.

[0027] The guide die 42 is supported from below by the punching die 32, and has a work receiving hole 42Z into which the intermediate formed product 91 after the punching preparation step can be inserted.

[0028] The punching die 32 has a workpiece receiving hole 32Z that is smaller than the workpiece receiving hole 42Z, and the upper surface of the punching die 32 and the workpiece receiving hole 32Z are perpendicular to each other to form an edge portion 32E. The planar shape of the edge portion 32E (not shown) is a rectangle that is slightly smaller than the inner surface of the intermediate molded product 91.

[0029] The punching punch 22 is a rectangular column that is slightly smaller than the work receiving hole 32Z of the punching die 32 (more specifically, the size of the work receiving hole 32Z minus a clearance suitable for shearing), and its bottom surface and side surface are perpendicular to each other to form an edge portion 22E.

[0030] The configuration of the transfer press 10 and the method for manufacturing the cylindrical product 90 of this embodiment are as described above. Below, we will explain the problems with the shape of the intermediate molded product 91 and how, in this embodiment, the problems are solved by sending the intermediate molded product 91 to the punching process after undergoing a punching preparation process.

[0031] Before the intermediate product 91 is completed by press molding, the bottom wall 92 is pressurized multiple times, gradually extending the axial length, and in the process, the metal material constituting the intermediate product 91 flows, causing the wall thickness of the intermediate product 91 to change. If the bottom wall 92 of the intermediate product 91 is circular, the material flows evenly between the side walls 93 and the bottom wall 92 over the entire circumferential direction of the intermediate product 91, and differences in the wall thickness of the side walls 93 are unlikely to occur. However, if the bottom wall 92 is non-circular, as in the intermediate product 91 of this embodiment, the material flow is unlikely to be even, and differences in the wall thickness of the side walls 93 are likely to occur.

[0032] Furthermore, in the final stage of multiple press forming operations, the radius of curvature of the corner R between the bottom wall and side wall of the workpiece becomes smaller than in the initial stage. When the workpiece is further drawn in the final stage, the inner corner curved surface between the bottom wall and side wall of the workpiece before the drawing remains at the lower end of the side wall, and as shown in Figure 3A, an annular recess 93S, commonly called a "shock mark," may occur at the lower end of the side wall 93 of the intermediate formed product 91.

[0033] Here, if the intermediate molded product 91 is punched out to form the tubular product 90 without going through the punching preparation process as in the past, the wall thickness of the side wall 93 may vary depending on the circumferential position of the lower end of the tubular product 90, or an annular recess 93S may remain, which may cause problems with the shape quality.

[0034] In contrast, in the transfer press 10 and manufacturing method of the tubular product 90 of this embodiment, as described in detail below, the intermediate molded product 91 undergoes a punching preparation process before the bottom wall 92 is punched out, thereby eliminating the above-mentioned problems with the tubular product 90.

[0035] That is, the intermediate molded product 91 is transported by the transfer device 11 to a position above the forming hole 31Z on the processing stage S for the punching preparation step. At this time, the counter punch 41 is located at its top dead center, with its upper surface located at the upper end of the forming hole 31Z. The punch 21 then descends, sandwiching the bottom wall 92 of the intermediate molded product 91 between itself and the counter punch 41. In this state, the intermediate molded product 91 descends together with the punch 21 and counter punch 41 and is forced into the forming hole 31Z.

[0036] As a result, a corner curved surface 93R (see FIG. 3A) at the outer edge of the lower end of the intermediate formed product 91 abuts against the inclined side surface 31B of the forming hole 31Z. At this time, although not shown, a space formed by a step between the punch main body 21X and the punch extension 21Y is located inside the lower end of the side wall 93 of the intermediate formed product 91, so the lower end of the side wall 93 easily deforms to narrow. Then, the outer edge of the bottom wall 92 abuts against the step surface 31C of the forming hole 31Z.

[0037] Then, the intermediate molded product 91 can no longer move downward, and as the punch 21 continues to descend, the portion of the bottom wall 92 that is inward from the outer edge thereof is pressed by the punch extension 21Y, forming the bulge 94. At the same time, the inner surface of the side wall 93 is ironed by the corner curved surface 21R1 of the outer edge of the punch main body 21X, and the annular recess 93S (see FIG. 3A) is smoothed so as to be flat, or the material in the portion where the annular recess 93S is formed flows toward the bottom wall 92, removing the annular recess 93S. Furthermore, the material that has flowed toward the bottom wall 92 flows deep into the corner between the stepped surface 31C and the inclined side surface 31B of the forming hole 31Z, so that the outer surface of the lower end of the intermediate formed product 91 is formed into a shape corresponding to the inclined side surface 31B, stepped surface 31C, and corner curved surface 31R1 of the forming hole 31Z, and the inner surface of the lower end of the intermediate formed product 91 is formed into a shape corresponding to the corner curved surface 21R1 and lower surface 21B of the punch 21, thereby forming an annular sheared portion 95 that surrounds the bulge 94. Then, the counter punch 41 rises and ejects the intermediate formed product 91 from the forming hole 31Z, completing the forming of the intermediate formed product 91 in the punching preparation step.

[0038] In this way, the bulge portion 94 is formed simultaneously with the formation of the lower end portion of the side wall 93 of the intermediate molded product 91, allowing the material to flow smoothly and achieving a uniform thickness around the entire circumference of the lower end portion of the side wall 93. Here, when the planar cross section is rectangular, as in the intermediate molded product 91 of this embodiment, material may easily accumulate along the pair of long sides of the rectangle. In contrast, in this embodiment, the pair of long sides of the bulge portion 94 are formed into a curved shape away from the outer edge of the bottom wall 92, so that more material can be accommodated without changing the wall thickness compared to a straight shape. As a result, material flows more easily into the pair of long sides of the bulge portion 94 than into other parts, which also results in a uniform thickness around the entire circumference of the side wall 93 of the intermediate molded product 91.

[0039] The intermediate molded product 91, which has been formed in the processing stage S for the punching preparation process, is transported by the transfer device 11 to the processing stage S for the punching process. Then, the punching punch 22 descends, and the annular sheared portion 95 of the intermediate molded product 91 is sandwiched between the punching punch 22 and the punching die 32. The punching punch 22 continues to descend. As a result, the annular sheared portion 95 is sheared between the edge portion 22E of the punching punch 22 and the edge portion 32E of the punching die 32, and the bottom wall 92 is punched out of the intermediate molded product 91, forming a tubular product 90. Then, as the punching punch 22 rises, the tubular product 90 is ejected out of the work receiving hole 42Z, and then the tubular product 90 is ejected from the transfer press 10 by the transfer device 11 or another conveyor (not shown), completing the production of the tubular product 90.

[0040] As described above, in the transfer press 10 and the manufacturing method for the tubular product 90 of this embodiment, the bulge 94 is formed in the bottom wall 92 before it is punched out from the intermediate molded product 91, so that excess material on the bottom wall 92 is absorbed by the bulge 94. This increases the fluidity of the material between the side wall 93 and the bottom wall 92 of the intermediate molded product 91, thereby achieving a uniform wall thickness of the side wall 93 of the intermediate molded product 91. Furthermore, the annular sheared portion 95 around the bulge 94 of the bottom wall 92 is sheared, and the bottom wall 92 is punched out to form the tubular product 90, so the uniformity of the wall thickness of the side wall 93 of the tubular product 90 is improved compared to conventional methods. In other words, the transfer press 10 and the manufacturing method for the tubular product 90 of this embodiment can manufacture a tubular product 90 with higher shape quality compared to conventional methods.

[0041] [Second embodiment] In the transfer press machine 10 and manufacturing method of the tubular product 90 of this embodiment, the punching preparation process is performed in two stages, as shown in Figures 7A to 7D, and the transfer press machine 10 of this embodiment is equipped with a processing stage S for the first punching preparation process shown in Figure 8 and a processing stage S for the second punching preparation process shown in Figure 9.

[0042] Furthermore, the bulge portion 94 of the intermediate molded product 91 of this embodiment is drawn deeper than the bulge portion 94 of the intermediate molded product 91 of the first embodiment, and more of the material of the side wall 93 flows toward the bottom wall 92. The depth of the bulge portion 94 is selected appropriately depending on, for example, the thickness of the side wall 93 relative to the size of the cross section of the intermediate molded product 91, the hardness of the material of the intermediate molded product 91, etc. Furthermore, as in this embodiment, the bulge portion 94 can be made deeper by dividing the punching preparation step into multiple steps.

[0043] Specifically, in the first punching preparation step, as shown in the change in shape from Fig. 7A to Fig. 7B, a bulging portion 94 and an annular inclined portion 97 that gradually narrows from the side wall 93 toward the bulging portion 94 are formed in the bottom wall 92 of the intermediate molded product 91. The inclination angle of the annular inclined portion 97 is 25° to 35° with respect to the pressing direction. In addition, the annular inclined portion 97 and the bulging portion 94 are at approximately the same height in the axial direction of the intermediate molded product 91.

[0044] In the second punching preparation step, as shown in the change in shape from Figure 7B to Figure 7C and the change in shape from Figure 8 to Figure 9, a part of the annular inclined portion 97 becomes part of the bulge portion 94, extending the bulge portion 94 upward, and the remaining part of the annular inclined portion 97 forms the annular sheared portion 95.

[0045] 9, the inner and outer surfaces of the annular sheared portion 95 do not have, for example, the inner flat surface 95A and the outer flat surface 95B described in the first embodiment, but are formed only by corner curved surfaces 95R1 to 95R3. The entire inner corner curved surface 95R3 of the annular sheared portion 95 is arranged to overlap part of the outer corner curved surface 95R2 in the vertical direction.

[0046] The punch 21U, die 33, guide die 43 and counter punch 41 of the processing stage S for the first punching preparation step shown in FIG. 8 are configured as follows.

[0047] The guide die 43 has a workpiece receiving hole 43Z extending vertically therethrough, into which the intermediate formed product 91 is fitted. The die 33 has a forming hole 33Z formed coaxially with the workpiece receiving hole 43Z. The forming hole 33Z consists of a conical portion 33F and a straight portion 33G below it. The conical portion 33F is a generally quadrangular pyramid tapering downward, and the inclination angle θ of its four inclined surfaces relative to the pressing direction is, for example, 25° to 35° (preferably 30°). Adjacent inclined surfaces are connected via curved corners. Furthermore, the upper end opening of the conical portion 33F is slightly wider than the lower end opening of the workpiece receiving hole 43Z.

[0048] The cross-sectional shape of the straight portion 33G is a rectangle that is approximately similar to the workpiece receiving hole 43Z, and all four inner surfaces of the straight portion 33G are flat surfaces that are approximately parallel to the pressing direction. In addition, the conical portion 33F and the straight portion 33G are connected by a corner curved surface 33R1.

[0049] The punch 21U differs from the punch 21 of the first embodiment only in that the distance between a pair of long sides of the rectangular cross-sectional shape of the punch extension 21Y is slightly larger and that all of the side surfaces of the punch extension 21Y are flat, but otherwise it is the same as the punch 21 of the first embodiment. That is, in the first punching preparation processing stage S, the distance between the four side surfaces of the punch extension 21Y and the four side surfaces of the opposing straight portion 33G at the portions corresponding to a pair of long sides of the rectangular cross-sectional shape is narrower than in the punching preparation stage S of the first embodiment, so that a portion of the bulging side wall 94A of the bulging portion 94 is ironed, as will be described later.

[0050] The counter punch 41 has a rectangular column shape that fits perfectly into the straight portion 33G.

[0051] The punch 21V, die 31V and counter punch 41 of the processing stage S for the second punching preparation step shown in FIG. 9 are configured as follows.

[0052] The die 31V has substantially the same shape as the die 31 of the first embodiment, except that the step surface 31C of the forming hole 31Z is narrow and all four side surfaces 31D below the step surface 31C are flat. In addition, the planar cross-sectional shape of the portion of the die 31V having the side surfaces 31D is substantially the same as the planar shape of the straight portion 33G of the processing stage S for the first punching preparation step.

[0053] The punch 21V has substantially the same shape as the punch 21U of the processing stage S for the first punching preparation step.

[0054] The counter punch 41 has a square pillar shape that fits exactly inside the side surface 31D of the forming hole 31Z.

[0055] The configuration of the transfer press 10 of this embodiment and the method for manufacturing the cylindrical product 90 are as described above. The effects of this embodiment will now be described.

[0056] When the intermediate molded product 91 is pushed by the punch 21U on the processing stage S for the first punching preparation step shown in FIG. 8 into the workpiece receiving hole 43Z and the molding hole 33Z, the corner curved surface 93R (see FIG. 7A) at the outer edge of the lower end of the intermediate molded product 91 abuts against the conical portion 33F of the molding hole 33Z. The punch 21U continues to descend from there, forming an annular inclined portion 97 from a portion of the bottom wall 92. Then, even after the lower end of the bottom wall 92 reaches the upper end of the straight portion 33G, the punch 21U continues to descend, forming a bulge 94. At this time, a portion of the annular inclined portion 97 is drawn into the straight portion 33G to form the bulge 94, and the side wall 93 of the intermediate molded product 91 is drawn in and becomes part of the annular inclined portion 97. This drawing of the side wall 93 moves the annular recess 93S described in the first embodiment toward the bottom wall 92. At this time, portions of the bulging side wall 94A of the bulging portion 94 that correspond to a pair of long sides of the rectangular cross section are squeezed, and the material of these portions flows upward from the bulging portion 94. As a result, the wall thickness of the pair of long sides of the rectangular cross section of the bulging portion 94 becomes thinner than the wall thickness of the pair of short sides.

[0057] After the first punching preparation step, the intermediate molded product 91 is transported by the transfer device 11 to the processing stage S for the second punching preparation step. When the intermediate molded product 91 is pressed into the forming hole 31Z in the processing stage S for the second punching preparation step, the annular inclined portion 97 comes into contact with the corner curved surface 31R1 of the die 31V. As the punch 21V continues to descend from there, the lower portion of the annular inclined portion 97 is raised so as to be parallel to the pressing direction, thereby extending the bulge portion 94 upward.

[0058] Simultaneously with the upward extension of the bulging portion 94, the upper portion of the annular inclined portion 97 is pressed against the corner curved surface 21R1 of the punch body 21X and then against the corner curved surface 31R1 of the die 31V, thereby forming the annular sheared portion 95.

[0059] After the second punching preparation step, the intermediate molded product 91 is subjected to the punching step processing stage S, in the same manner as in the first embodiment, where the annular sheared portion 95 is sheared and the bottom wall 92 is punched out, thereby forming a cylindrical product 90.

[0060] As in the first embodiment, the transfer press 10 and manufacturing method for the tubular product 90 of this embodiment also form a bulge 94 on the bottom wall 92 before punching out the intermediate product 91. This increases the fluidity of the material between the side wall 93 and the bottom wall 92 of the intermediate product 91, thereby achieving a uniform wall thickness of the side wall 93 of the intermediate product 91. This allows for the manufacturing of a tubular product 90 with higher shape quality than conventional methods. Furthermore, if the bulge 94 is shallow, the wall thickness may not be sufficiently uniform. However, by dividing the punching preparation process into multiple steps as in this embodiment, the bulge 94 can be formed deeper, thereby achieving a sufficiently uniform wall thickness. Furthermore, if the bulge 94 is deep, a portion of the material on the side wall 93 may flow excessively toward the bottom wall 92. Specifically, if the bulge 94 is shallow, excess material may be present on the pair of long sides, whereas if the bulge 94 is deep, excessive material may flow out. In contrast, in the present embodiment, excessive meat leakage can be suppressed by squeezing a portion of the bulging side wall 94A of the bulging portion 94, which also makes it possible to sufficiently uniformize the wall thickness and improves the shape quality of the tubular product 90. [Other embodiments]

[0061] In the first and second embodiments, the bottom wall 92 of the intermediate molded product 91 is rectangular, but it may be any non-circular shape, such as a square, a polygon other than a rectangle, an ellipse, an oval, or an irregular shape without a name.

[0062] In the first and second embodiments, the planar cross-sectional shape of the side wall 93 of the intermediate molded product 91 is uniform in the vertical direction, but the shape or size of the planar cross-section may vary depending on the vertical position of the side wall 93. For example, the lower end of the side wall 93 may be non-circular like the bottom wall 92, but may have a shape that gradually changes to a circular shape as it moves away from the lower end, or may have a step part in the middle, so that the part below the step has the same planar cross-sectional shape as the bottom wall 92 and the part above the step has a planar cross-sectional shape different from that of the lower part.

[0063] In the first embodiment, only two of the four faces of the bulging side wall 94A of the bulging portion 94, corresponding to a pair of long sides, were curved, but all of the multiple faces of the bulging side wall 94A may be curved away from the outer edge depending on the amount of excess material in the side wall 93.

[0064] In the second embodiment, only two of the four surfaces of the bulging side wall 94A of the bulging portion 94, corresponding to a pair of long sides, were squeezed to allow the meat to flow upward, but depending on the level of meat shortage in the side wall 93, all of the multiple surfaces of the bulging side wall 94A may be squeezed to allow the meat to flow upward.

[0065] In the second embodiment, the bulging side wall 94A is squeezed only in the first punching preparation step out of the first and second punching preparation steps, but the bulging side wall 94A may be squeezed only in the second punching preparation step or in both the first and second punching preparation steps.

[0066] In the second embodiment, the punching preparation step is carried out in two separate steps, but it may be carried out in three or more separate steps.

[0067] In the first and second embodiments, the inclined surface 93A is formed at the lower end of the side wall 93 of the intermediate molded product 91, but the inclined surface 93A does not have to be formed.

[0068] <Additional Notes> The following describes the features extracted from the above-described embodiments, while indicating their effects, etc., as necessary. For ease of understanding, corresponding configurations in the above-described embodiments are indicated in parentheses, etc., as appropriate, but these features are not limited to the specific configurations indicated in parentheses, etc.

[0069] [Feature 1] In this manufacturing method for producing a tubular product (90) by punching out a non-circular bottom wall (92) from an intermediate product (91), which is a tubular press-molded product having the bottom wall (92), the method includes a punching preparation step in which the bottom wall (92) is press-molded into a shape having an annular sheared portion (95) having inner and outer surfaces intersecting the pressing direction and a bulge portion (94) surrounded by the annular sheared portion (95), and a punching step in which the annular sheared portion (95) is sheared to punch out the bottom wall (92).

[0070] [Feature 2] The method for manufacturing a tubular product (90) according to Feature 1, wherein the intermediate molded product (91) is produced through a plurality of press moldings before the punching preparation step, and an annular recess (93S) is formed on the inner surface of the side wall (93) of the intermediate molded product (91) on the bottom wall (92) side during the press molding, and in the punching preparation step, the material of the portion of the side wall (93) having the annular recess (93S) is moved toward the bottom wall (92), or the material above the annular recess (93S) is moved toward the annular recess (93S).

[0071] [Feature 3] A manufacturing method for a tubular product (90) according to feature 1 or 2, wherein the planar shapes of the bottom wall (92) and the bulge portion (94) are polygons that are approximately similar to each other, and the bulge portion (94) is press-molded so that at least some of the sides of the polygon that is the planar shape of the bulge portion (94) are curved away from the side corresponding to the polygon that is the planar shape of the bottom wall (92).

[0072] [Feature 4] The method for manufacturing the tubular product (90) described in Feature 3, wherein the polygon is a quadrangle having a pair of short sides and a pair of long sides, and the bulge portion (94) is press-molded so that only the pair of long sides are curved away from the side corresponding to the bottom wall (92).

[0073] [Feature 5] 5. The method for manufacturing a cylindrical product (90) according to any one of features 1 to 4, wherein the bulging portion (94) and the annular sheared portion (95) are formed by a single press.

[0074] [Feature 6] The method for manufacturing a tubular product (90) according to any one of Features 1 to 4, wherein the punching preparation step includes: a first punching preparation step in which the bottom wall (92) is press-molded with the bulge portion (94) and an annular inclined portion (97) that gradually narrows from the side wall (93) of the intermediate molded product (91) toward the bulge portion (94); and a second punching preparation step in which the annular inclined portion (97) is press-molded so that a portion of the annular inclined portion (97) that is to become the bulge portion (94) is bent toward a side parallel to the press direction to become part of the bulge portion (94), and the remaining portion of the annular inclined portion (97) is bent toward a side perpendicular to the press direction to become the annular sheared portion (95).

[0075] [Feature 7] 7. The method for manufacturing a cylindrical product (90) according to Feature 6, wherein the angle of inclination of the annular inclined portion (97) relative to the pressing direction is 25° to 35°.

[0076] [Feature 8] The method for manufacturing a tubular product (90) according to Feature 6, wherein the planar shapes of the bottom wall (92) and the bulging portion (94) are polygons that are approximately similar to each other, and in the first or second punching preparation step, a bulging side wall (94A) corresponding to at least a part of the sides of the polygon that is the planar shape of the bulging portion (94) is ironed.

[0077] [Feature 9] A manufacturing method for a cylindrical product (90) according to any one of features 1 to 8, wherein a cylindrical body forming process in which a flat plate is drawn multiple times to form the intermediate formed product (91), the punching preparation process, and the punching process are performed in a common transfer press machine (10).

[0078] [Feature 10] A transfer press (10) having a plurality of processing stages (S) arranged in a row in the horizontal direction, in which a workpiece is sequentially moved to one side of the horizontal direction and processed at each of the processing stages (S), the plurality of processing stages (S) including: a plurality of processing stages (S) for a cylindrical body forming process in which a flat plate is drawn a plurality of times to form a cylindrical intermediate formed product (91) having a non-circular bottom wall (92); one or more processing stages (S) for a punching preparation process in which the bottom wall (92) of the intermediate formed product (91) is formed into a shape having an annular sheared portion (95) having inner and outer surfaces intersecting the pressing direction and a bulge portion (94) surrounded by the annular sheared portion (95); and a processing stage (S) for a punching process in which the annular sheared portion (95) is sheared to punch out the bottom wall (92).

[0079] [Feature 11] In the processing stages (S) for the plurality of cylindrical molding processes, the intermediate molded product (91) is squeezed until an annular recess (93S) is formed on the inner surface of the end of its side wall (93), and in the processing stages (S) for the one or more punching preparation processes, material in the portion of the side wall (93) having the annular recess (93S) flows toward the bottom wall (92), or material above the annular recess (93S) flows toward the annular recess (93S).

[0080] [Feature 12] The transfer press (10) according to feature 10 or 11, wherein in the plurality of processing stages (S), the bottom wall (92) of the intermediate molded product (91) is formed into a polygon, and in the one or more processing stages (S) for the punching preparation process, the planar shape of the bulge portion (94) is formed into a polygon that is approximately similar to the bottom wall (92) of the intermediate molded product (91) and has at least some of its sides curved away from the side of the bottom wall (92) corresponding to the polygon.

[0081] [Feature 13] The transfer press (10) described in Feature 12, wherein the polygon is a rectangle having a pair of short sides and a pair of long sides, and the bulge portion (94) is formed so that only the pair of long sides curve away from the side corresponding to the bottom wall (92). [Feature 14] The transfer press machine (10) according to any one of features 10 to 13, wherein the number of processing stages (S) for the punching preparation process is one, and the bulge portion (94) and the annular sheared portion (95) are formed in a single press.

[0082] [Feature 15] 14. The transfer press (10) according to any one of Features 10 to 13, wherein a plurality of processing stages (S) for the punching preparation process are provided, and the plurality of processing stages (S) for the punching preparation process include one or more processing stages (S) for a first preparation stage that forms, in the bottom wall (92), the bulge portion (94) and an annular inclined portion (97) that gradually narrows from the side wall (93) of the intermediate molded product (91) toward the bulge portion (94), and one or more processing stages (S) for a second preparation stage that bends a portion of the annular inclined portion (97) that will become the bulge portion (94) toward a side parallel to the pressing direction to form it as part of the bulge portion (94), and bends the remaining portion of the annular inclined portion (97) toward a side perpendicular to the pressing direction to form the annular sheared portion (95).

[0083] [Feature 16] Feature 16. The method for manufacturing a cylindrical product (90) according to Feature 15, wherein the angle of inclination of the annular inclined portion (97) relative to the pressing direction is 25° to 35°.

[0084] [Feature 17] The transfer press (10) according to feature 15 or 16, wherein the bottom wall (92) and the bulge portion (94) of the intermediate molded product (91) are formed to have polygonal planar shapes that are approximately similar to each other, and in the processing stage (S) for the first or second punching preparation step, a bulge side wall (94A) corresponding to at least some of the sides of the polygonal planar shape of the bulge portion (94) is squeezed.

[0085] The above features provide the following advantages. When the bottom wall of a press-formed intermediate product is noncircular, it is difficult to achieve uniform material flow between the side walls and the bottom wall during press forming, which can lead to differences in the wall thickness of the side walls. However, the manufacturing method and transfer press machine of Features 1 and 10 form a bulge in the bottom wall before punching out the intermediate product, allowing excess material on the bottom wall to be absorbed by the bulge. This increases material flow between the side walls and the bottom wall of the intermediate product, resulting in a uniform wall thickness of the side walls of the intermediate product. Furthermore, the annular sheared portion around the bulge in the bottom wall is sheared to punch out the bottom wall and form a cylindrical product, improving the uniformity of the wall thickness of the side walls of the cylindrical product compared to conventional methods. In other words, the first and second aspects of the present disclosure enable the production of cylindrical products with higher shape quality than conventional methods.

[0086] When a cylindrical intermediate product is formed by multiple press moldings, a ring-shaped recess (so-called a shock mark) may be formed on the inner surface of the bottom wall of the side wall of the intermediate product during the press molding process. In response to this, the formation of the bulge increases the fluidity of the material, so that the material in the portion with the ring-shaped recess flows toward the bottom wall, or the material above the ring-shaped recess flows toward the ring-shaped recess, eliminating the ring-shaped recess in the cylindrical product and improving shape quality (Features 2 and 11).

[0087] When the bottom wall of the intermediate product is polygonal, the bulge may accumulate at the center of at least some of the side walls on the bottom wall side of the intermediate product. In contrast, in Features 3 and 12, the bulge is press-formed so that the planar shape of the bulge is a polygon similar to the bottom wall, and at least some of the sides of the polygon are curved away from the outer edge of the bottom wall. This allows the bulge to curve away from the outer edge of the bottom wall in the area where the bulge tends to accumulate, facilitating the flow of the bulge at the center of the side wall of the intermediate product toward the bottom wall, thereby achieving a uniform wall thickness of the side wall of the intermediate product. Furthermore, when the polygon is a rectangle having a pair of short sides and a pair of long sides, as in Features 4 and 13, the bulge tends to accumulate at the center of the side wall corresponding to the pair of long sides. Therefore, by curving only the portion of the bulge corresponding to the pair of long sides away from the outer edge of the bottom wall, the wall thickness of the side wall of the intermediate product can be uniformed.

[0088] The bulging portion and the annular sheared portion may be formed in a single press, as in Features 5 and 14, or the bulging portion and the annular inclined portion that gradually narrows toward the bulging portion may first be press-formed on the bottom wall, and then a portion of the annular inclined portion may be bent perpendicular to the pressing direction to form the annular sheared portion, as in Features 6 and 15. In this case, as in Features 7 and 16, by setting the inclination angle of the annular inclined portion relative to the pressing direction to, for example, 25° to 35°, the meat can flow smoothly toward the bulging portion.

[0089] When the bottom wall of the intermediate product is polygonal, the material of at least some of the side walls of the intermediate product may flow too much from the center toward the bulge, resulting in thinning. In contrast, in Features 8 and 17, by squeezing at least some of the side walls of the bulge, the material flow toward the bulge is suppressed, resulting in uniform wall thickness of the side walls of the intermediate product.

[0090] According to Feature 9, by using a transfer press, it is possible to simultaneously manufacture an intermediate formed product and manufacture a cylindrical product from the intermediate formed product.

[0091] Although the present specification and drawings disclose specific examples of the technology included in the scope of the claims, the technology described in the claims is not limited to these specific examples, but also includes various modifications and variations of the specific examples, and also includes parts of the specific examples taken out alone. [Explanation of symbols]

[0092] 10 Transfer press machine 90 Cylindrical products 91 Intermediate molded products 92 Bottom wall 93 Side wall 93S Annular recess 94 Bulge 95 Annular sheared part 97 Circular ramp S processing stage θ Tilt angle

Claims

1. A manufacturing method for manufacturing a cylindrical product by punching out a non-circular bottom wall from an intermediate product that is a cylindrical press-molded product, the intermediate product comprising: a punching preparation step in which the bottom wall is press-molded into a shape having an annular sheared portion having inner and outer surfaces intersecting a pressing direction and a bulge portion surrounded by the annular sheared portion; a punching step in which the annular sheared portion is sheared to punch out the bottom wall; A manufacturing method of a cylindrical product in which the above steps are carried out.

2. The intermediate product is produced through a plurality of press moldings before the punching preparation step, and an annular recess is formed on an inner surface of the side wall of the intermediate product on the bottom wall side by the press moldings, A method for manufacturing a tubular product as described in claim 1, wherein in the punching preparation process, the material of the portion of the side wall having the annular recess is moved toward the bottom wall, or the material above the annular recess is moved toward the annular recess.

3. the bottom wall and the bulging portion have planar shapes that are substantially similar polygons; A method for manufacturing a tubular product as described in claim 1, wherein the bulge is press-molded so that at least some of the multiple sides of the polygon that is the planar shape of the bulge are curved away from the side corresponding to the polygon that is the planar shape of the bottom wall.

4. The method for manufacturing a tubular product described in claim 3, wherein the polygon is a rectangle having a pair of short sides and a pair of long sides, and the bulge portion is press-molded so that only the pair of long sides curve away from the side corresponding to the bottom wall.

5. 5. The method for manufacturing a cylindrical product according to claim 1, wherein the bulging portion and the annular sheared portion are formed by a single press operation.

6. The punching preparation step includes: a first punching preparation step in which the bulge portion and an annular inclined portion that gradually narrows from the side wall of the intermediate molded product toward the bulge portion are press-formed on the bottom wall; A method for manufacturing a tubular product as described in any one of claims 1 to 4, which includes a second punching preparation process in which the portion of the annular inclined portion that will become the bulge portion is bent parallel to the press direction to become part of the bulge portion, and the remaining portion of the annular inclined portion is bent perpendicular to the press direction to become the annular sheared portion.

7. 7. The method for manufacturing a cylindrical product according to claim 6, wherein the inclination angle of the annular inclined portion relative to the pressing direction is 25° to 35°.

8. the bottom wall and the bulging portion have planar shapes that are substantially similar polygons; 7. The method for manufacturing a cylindrical product according to claim 6, wherein in the first or second punching preparation step, a bulging side wall corresponding to at least a part of the sides of the polygonal planar shape of the bulging portion is ironed.

9. 2. A method for manufacturing a cylindrical product as described in claim 1, wherein the cylindrical forming process in which a flat plate is drawn multiple times to form the intermediate formed product, the punching preparation process, and the punching process are performed using a common transfer press.

10. A transfer press machine having a plurality of processing stages arranged in a row in a horizontal direction, in which a workpiece is sequentially moved to one side in the horizontal direction and processed at each of the processing stages, The plurality of processing stages include: a plurality of processing stages for a cylindrical body forming step in which a flat plate is drawn a plurality of times to form a cylindrical intermediate formed product having a non-circular bottom wall; one or more processing stages for a punching preparation step, which form the bottom wall of the intermediate molded product into a shape having an annular sheared portion having inner and outer surfaces intersecting with the press direction and a bulge portion surrounded by the annular sheared portion; a processing stage for a punching step that shears the annular sheared portion and punches out the bottom wall.

11. In the processing stages for the plurality of cylindrical body forming steps, the intermediate formed product is squeezed until an annular recess is formed on the inner surface of the end of the side wall thereof; A transfer press machine according to claim 10, wherein in the processing stage for the one or more punching preparation steps, material in a portion of the side wall having the annular recess is caused to flow toward the bottom wall, or material above the annular recess is caused to flow into the annular recess.

12. In the plurality of processing stages, the bottom wall of the intermediate molded product is molded into a polygonal shape, A transfer press machine as described in claim 10, wherein in the processing stage for the one or more punching preparation steps, the planar shape of the bulge portion is formed into a polygon that is approximately similar to the bottom wall of the intermediate molded product and has at least some of its sides curved away from the side of the bottom wall corresponding to the polygon.

13. 13. The transfer press according to claim 12, wherein the polygon is a rectangle having a pair of short sides and a pair of long sides, and the bulge is formed so that only the pair of long sides are curved away from the side corresponding to the bottom wall.

14. The number of processing stages for the punching preparation step is 1, 14. A transfer press according to claim 10, wherein the bulging portion and the annular sheared portion are formed in a single press operation.

15. A plurality of processing stages for the punching preparation step are provided, The processing stages for these multiple punching preparation processes include: one or more processing stages for a first preparation stage for forming the bulge portion and an annular inclined portion that gradually narrows from the side wall of the intermediate molded product toward the bulge portion on the bottom wall; and one or more processing stages for a second preparation step in which a portion of the annular inclined portion that will become the bulging portion is bent in a direction parallel to the pressing direction to form part of the bulging portion, and a remaining portion of the annular inclined portion is bent in a direction perpendicular to the pressing direction to form the annular sheared portion.

16. 16. The method for manufacturing a cylindrical product according to claim 15, wherein the inclination angle of the annular inclined portion relative to the pressing direction is 25° to 35°.

17. The bottom wall and the bulge portion of the intermediate molded product are molded so that their planar shapes are polygonal and substantially similar to each other; 16. The transfer press according to claim 15, wherein a bulging side wall corresponding to at least a part of a side of the polygonal planar shape of the bulging portion is squeezed in the processing stage for the first or second punching preparation step.

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