Metal can manufacturing method

Abstract

To provide a metallic can having a polyhedral wall with a high buckling strength by changing a shape of a boundary part between the polyhedral wall and a non-processing area, a positive pressure can and a manufacturing method of the metallic can.SOLUTION: When an area where a polyhedral wall of a can truck is not formed is defined as a cylindrical non-processing area, in a metallic can in which a half panel part formed on a non-processing region side with respect to a lateral ridge line of a unit panel positioned at a boundary between the polyhedral wall and the non-processing region is an incomplete half panel part in which an inclined ridge line constituting the half panel part does not form a top part, and the other half panel part has a complete half panel part formed by the lateral ridge line and the inclined ridge line, an axial direction distance parallel to a central axis line of the can truck from a tip part of a molding area with which an inner molding tool contacts when forming the incomplete half panel part to the lateral ridge line is shorter than an axial direction distance from the lateral ridge line to the top part of the complete half panel part.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a metal can body having a polyhedron wall formed by a plurality of unit panels. can Regarding the manufacturing method. [Background technology]

[0002] A conventional metal can having this type of polyhedral wall is known, for example, as described in Patent Document 1. This metal can has a polyhedral wall composed of a number of unit panels separated by convex boundary ridges in a portion of the can body. Each unit panel is diamond-shaped, separated by diagonal ridges as boundary ridges, and has four apexes: two apexes located on a central plane passing through the central axis of the can body and two apexes located symmetrically with respect to the central plane. A valley-folded horizontal ridge line connects the apexes located symmetrically with respect to the central plane. The polyhedral wall is formed by alternately arranging unit panel rows, each row consisting of a plurality of unit panels aligned parallel to the central axis of the can body, with a half-phase offset from each other in the circumferential direction, so that a cross section passing through the horizontal ridge lines of the unit panels and perpendicular to the central axis of the can body, has a polygonal shape. The unit panel located at the boundary between the polyhedron wall and the non-processed area has an incomplete half-panel shape in which the half-panel portion on the non-processed area side of the horizontal ridge line transitions into the non-processed area without the diagonal ridge line that makes up this half-panel portion forming a peak, and the shape smoothly transitions from the polygonal shape of the polyhedron wall to the cylindrical shape of the non-processed area. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-050040 Summary of the Invention [Problem to be solved by the invention]

[0004] In the case of a metal can in which a polyhedron wall is processed in a part of the can body as in Patent Document 1, the cylindrical unprocessed area has traditionally had a higher buckling strength against an axial compressive load than the polyhedron wall. Buckling is known to occur. In recent years, there has been a demand for thinner plates to reduce the weight of containers, but it has been found that thinner plates tend to cause buckling deformation near the boundary between the polyhedron wall and the unprocessed area.Increasing the plate thickness makes it less likely for buckling to occur near the boundary, but this increases the weight of the container and increases costs. Buckling deformation occurs in the region between the incomplete half panels arranged circumferentially at the boundary with the unprocessed region. Although the incomplete half panels do not have peaks, when an axial compressive load is applied, a stress concentration area of ​​compressive stress occurs near the intersection of the extensions of the diagonal ridges, and this area acts as a pseudo-peak, deforming in a direction that protrudes outward from the can. In addition, tensile stress is generated in the region between the stress concentration areas in a direction that causes a depression inward in the can. When a depression is formed, buckling deformation progresses rapidly. As a result of intensive research, we discovered that the shape of the imperfect half-panel at the boundary where the polyhedron wall transitions to the unprocessed area makes it less likely for buckling to occur at the boundary even if the plate thickness is reduced, thereby increasing the buckling strength. The object of the present invention is to provide a metal structure having high buckling strength with polyhedron walls by changing the shape of the incomplete half panel portion at the boundary between the polyhedron walls and the non-processed area. can The object is to provide a manufacturing method. [Means for solving the problem]

[0005] In order to achieve the above object, the present invention provides a can body having a polyhedral wall formed of a number of unit panels partitioned by convex boundary ridges, Each unit panel has a diamond shape defined by the diagonal ridge line as the boundary ridge line, and has four apexes in total, including two apexes located on a central plane passing through the central axis of the can body and two apexes located at positions symmetrical with respect to the central plane, and has a valley-folded horizontal ridge line that connects the apexes located at positions symmetrical with respect to the central plane and is perpendicular to the central plane, The polyhedron wall has a plurality of unit panels arranged in rows parallel to the central axis of the can body, the unit panels being alternately arranged with a half-phase offset from each other in the circumferential direction, and has a polygonal cross section perpendicular to the axis, which crosses the horizontal ridge line of the unit panel and is perpendicular to the central axis of the can body, When the region of the can body where the polyhedron wall is not formed is defined as a cylindrical non-processing region, a half panel portion formed on the non-processing region side of the horizontal ridge line of a unit panel located at the boundary between the polyhedron wall and the non-processing region is The horizontal ridge line is the base, and the further away from the horizontal ridge line, As the distance between them narrows, A method of manufacturing a metal can in which an oblique ridge line forms an incomplete half panel portion that does not form a top, and the other half panel portions are complete half panel portions formed by the horizontal ridge line and the oblique ridge line, a region circumferentially adjacent to the incomplete half panel portion is a partial cylindrical region into which a part of the cylindrical surface shape of the non-machined region is inserted; The axial distance in the direction parallel to the central axis from the tip of the forming area with which an inner mold tool comes into contact when forming the incomplete half panel portion to the lateral ridge line is Department The axial distance from the lateral ridge to the top of the And in front The above partial cylindrical area A part of the cylindrical surface shape crosses the diagonal ridge and penetrates into the incomplete half panel portion. The method is characterized in that the molded product is formed as follows: The area adjacent to the incomplete half panel portion that forms the boundary in the circumferential direction is a partial cylindrical area in which part of the cylindrical surface shape of the non-machined area has entered. Part of a cylindrical surface However, it crosses the diagonal boundary ridge, making the shape of the incomplete half panel at the boundary an ambiguous shape. The inventors discovered that the ambiguous shape from this partial cylindrical region to the incomplete half-panel portion at the boundary changes depending on the contact state of the forming mold during the molding process, and that by reducing the degree of processing, the shape becomes closer to a cylinder, dispersing the compressive stress and increasing the buckling strength. In order to reduce the degree of processing, in the third invention, the axial distance from the lateral ridge of the forming region sandwiched between the inner and outer mold tools is shortened, which increases the influence of the cylindrical shape of the partially cylindrical region, making it closer to a cylinder in shape and increasing the buckling strength.

[0006] The present invention can also be configured as follows. 1. The axial distance parallel to the central axis from the tip of the forming region to the lateral ridge is set to 70% or less of the axial distance from the lateral ridge to the top of the complete half panel. In this way, the buckling strength can be increased. 2. The distance of the forming area is the distance from the horizontal ridge to the end position of the diagonal ridge. By configuring in this way, it is possible to confirm the contact area.

[0007] It can also be configured as follows. 1. The thickness of the incomplete half panel portion shall be 0.106 mm or less. Even with such a thin plate thickness, buckling can be prevented from occurring near the boundary with the non-processed portion. 2. The cross section passing through the horizontal ridge line of the unit panel and perpendicular to the central axis of the can body has 13 or more sides. In this way, when the size is 13 or more sides, the unit panel becomes smaller and the panel depth becomes smaller, which improves the buckling strength and allows for thinner and more diversified panels. 。

[0008] Another invention is: a partial axial region of a cylindrical body blank is sandwiched between an inner mold and an outer mold, a boundary ridge line of the body blank is folded outward by the inner mold, and an area surrounded by the boundary ridge line is depressed inward by the outer mold to form a plurality of unit panels and form a polyhedron wall, and the polyhedron wall and a cylindrical unprocessed region where the polyhedron wall is not processed are formed in the body blank; The unit panel has a diamond shape defined by a diagonal ridge line as the boundary ridge line, and has a total of four apexes, two apexes located on a central plane passing through the central axis of the body blank and two apexes located at positions symmetrical to the central plane, and has a horizontal valley fold ridge line that connects the apexes located at positions symmetrical to the central plane and is perpendicular to the central plane, and if the area of ​​the body blank where the polyhedron wall is not formed is a cylindrical non-processed area, the half panel portion formed on the non-processed area side of the horizontal ridge line of the unit panel located at the boundary between the polyhedron wall and the non-processed area is A pair of grooves having the horizontal ridge line as a base and the distance between them narrows as they move away from the horizontal ridge line. A method of manufacturing a metal can in which an oblique ridge line forms an incomplete half panel portion that does not form a top, and the other half panel portions are complete half panel portions formed by the horizontal ridge line and the oblique ridge line, a region circumferentially adjacent to the incomplete half panel portion is a partial cylindrical region into which a part of the cylindrical surface shape of the non-machined region is inserted; The incomplete half panel portion is formed by making the contact area of ​​the inner mold with the body blank smaller than the contact area of ​​the complete half panel portion, so that the cylindrical shape of the partial cylindrical region does not extend beyond the oblique ridge line. and penetrates into the incomplete half panel portion. The present invention is characterized in that the molded product is molded as follows. This reduces the degree of processing and reduces the influence of the cylindrical shape of the adjacent partial cylindrical area. It becomes larger and closer to a cylinder in shape, which increases the buckling strength. The present invention can also be configured as follows. 1. When forming the incomplete half panel portion, the contact area of ​​the inner mold with the body blank is set to 70% or less of the contact area of ​​the complete half panel portion. In this way, the buckling strength can be increased more reliably. [Effects of the Invention]

[0009] According to the present invention, the buckling strength can be increased by changing the shape of the incomplete half panel portion at the boundary between the polyhedron wall and the unprocessed region. [Brief explanation of the drawings]

[0010] [Figure 1]FIG. 1 shows a hexagonal metal can according to an embodiment of the present invention, where (A) is a front view and (B) is a cross-sectional view taken along line AA of (A). [Figure 2] 2A is an enlarged perspective view of the main part of the metal can of FIG. 1, and FIG. 2B is a cross-sectional view taken along the vertical line BB of FIG. [Figure 3] FIG. 3 is a conceptual diagram showing the state of machining the polyhedron wall using the inner and outer tools, as viewed from the can axial direction. [Figure 4] 4(A) is a perspective view of the main part showing the inner tool and the outer tool of FIG. 3 separated, and FIG. 4(B) is a partially sectional front view showing the state in which a body blank is being machined by the inner tool and the outer tool of FIG. [Figure 5] 5A is a plan view of the vicinity of the boundary between the forming region and the non-processing region of the inner mold tool that forms the polyhedral wall of the metal can in FIG. 2, (B) is a cross-sectional view showing the formed state of the metal can taken at the BB cross section of the inner mold tool in (A), and (C) is a cross-sectional view showing the formed state of the metal can taken at the CC cross section of (A). [Figure 6] FIG. 6(A) is a view showing a panel row of the metal can of FIG. 1, and (B) is a cross-sectional view taken along line BB in (A). [Figure 7] FIG. 7 is a diagram showing a measuring device for measuring the panel tilt angle and the panel depth. [Figure 8] FIG. 8(A) is a diagram showing the relationship between the inclination angle ratio and the number of corners of the polyhedron wall, and (B) is a diagram showing the relationship between the depth ratio and the number of corners of the polyhedron wall. [Figure 9] FIG. 9 shows a method for measuring buckling strength, where (A) is an overall view of the measuring device, and (B) is a view showing the neck reinforcing jig used when measuring buckling strength. [Figure 10] FIG. 10(A) is a diagram showing a positive pressure can in which the metal can of this embodiment is filled with a content that creates a positive internal pressure and the can lid is seamed, and FIG. 10(B) is a diagram showing a state in which the positive pressure has been released. DETAILED DESCRIPTION OF THE INVENTION

[0011] The present invention will be described in detail below based on the illustrated embodiments. The dimensions, materials, shapes, and relative arrangements of the components described in this embodiment may be changed as appropriate depending on the configuration and various conditions of the device to which the invention is applied, and are not intended to limit the scope of the invention to the following embodiments. First, with reference to FIG. 1, the overall structure of a metal can according to an embodiment of the present invention will be described. This metal can 1 is a typical drawn and ironed can made of an aluminum alloy or the like, and is configured to have a cylindrical can body 21 that extends straight, a neck portion 22 with a reduced diameter at the upper end of the can body 21, and a bottom portion 23. A flange 24 is provided at the opening of the upper end of the neck portion 22, around which a can lid (not shown) is wrapped and fastened. In this embodiment, for example, the metal can is a positive pressure can with a capacity of 160 ml to 500 ml and an internal can pressure of 20 to 300 kPa at 5°C, and is assumed to be used in a can body 21 having a thickness of 0.075 to 0.135 mm, a can body diameter D of 50 to 70 mm (diameter 202 to 211 mm), and a can height H of 90 to 170 mm. The ratio of the can height H to the can body diameter D is approximately 1.3 to 2.6. The present invention is not limited to metal cans for positive pressure cans, but can also be applied to negative pressure cans, and is not limited to aluminum alloys, but can also be applied to steel cans, and is therefore widely applicable to metal cans.

[0012] The polyhedron wall 4 has an uneven shape created by a folding structure without changing the circumferential length of the can body 21, and is composed of a large number of diamond-shaped unit panels 5 partitioned by folds along boundary ridges 51. A predetermined number of unit panels 5 are arranged in a direction parallel to the can axis O, which is the central axis of the can body 21 (hereinafter simply referred to as the axial direction), to form panel rows (unit panel rows) 50, and these panel rows 50 are arranged all around the circumferential direction of the can body 21. The axial phase of the unit panels 5 of adjacent panel rows 50 is shifted by half the axial length of the unit panel 5, and the unit panels 5 are densely arranged in both the axial and circumferential directions. Adjacent panel rows 50 are offset in the axial direction by half the length of the unit panel 5, so that the unit panels 5 of panel rows 50 positioned every other in the circumferential direction are in the same phase in the axial direction, and the horizontal ridges 52 of the valley folds are connected via a common apex 53. Therefore, the cross-sectional shape of the unit panel 5 taken at a horizontal ridge line 52 in a direction perpendicular to the can axis O will be a regular polygon, as shown in Figure 1(B). In the illustrated example, a regular hexagonal cross-sectional shape is shown as a suitable example, but the number of sides is not limited to 16, and the shape may be a polygon with fewer or more sides than 16. In this example, the polyhedron wall 4 is provided in a band shape in the middle of the axial direction of the can body 21, and the unprocessed areas at the top and bottom of the polyhedron wall 4 are cylindrical straight sections 21a, 21b without any irregularities.

[0013] Figure 10 shows a positive pressure can 10 using the above metal can. Figure 10(A) shows the state where internal pressure is applied before opening, and Figure 10(B) shows the state where the internal pressure is released after opening. That is, the positively pressurized can 10 comprises a metal can 1 and a can lid 3 which fills the metal can with contents and seals it under positive pressure, and the unit panel 5 of the polyhedral wall 4 has a shape recessed inward into the can body 2 in a free state, and as shown in Figure 10(A), it deforms in a direction that reduces the recess due to the internal pressure acting on the can body 2, and when the can lid 3 is opened, it returns to its original shape as shown in Figure 10(B).

[0014] The present invention is directed to a design of the boundary between the unit panels 5 located at both axial ends of the polyhedron wall 4 and the non-processed area. The shape of the unit panels will be described below with reference to FIG. 2(A) is an enlarged perspective view of the main part of a unit panel near the boundary between the straight section and the end on the open end side of the polyhedral wall in Fig. 1, as seen from a viewpoint at an elevation angle relative to the axis-perpendicular direction, and (B) is a cross-sectional view taken along line BB in (A) and cut at a plane passing through the can axis. The area near the boundary between the straight section and the end on the bottom side of the polyhedral wall has the same structure, except that it is vertically symmetrical. First, the configuration of a complete unit panel 5 (complete unit panel) will be described using the second unit panel 5 from the end as an example, rather than the unit panel at the boundary of the straight section. Each unit panel 5 has four tops: two tops 53, 53 located on a central plane M passing through the can axis O of the can body 21, and two tops 53, 53 located symmetrically with respect to the central plane M. These four tops 53 are ideally located on a cylindrical surface centered on the can axis O, and are configured to be bent inward in the axial direction of the can body 21 in a dogleg shape by horizontal valley fold ridges 52 connecting the tops 53, 53 located symmetrically with respect to the central plane M. The diameter of an imaginary cylindrical surface passing through the four tops 53 is the maximum diameter of the can body 21. If the triangular portion located on the opening end side, separated by the horizontal ridge line 52, is called the upper half panel portion 5a, and the triangular portion located on the bottom side is called the lower half panel portion 5b, the upper half panel portion 5a and the lower half panel portion 5b are identical isosceles triangular portions with the horizontal ridge line 52 as their base and an apex 53 located on the center plane M, and will hereafter be referred to as complete half panel portions.

[0015] Next, an incomplete unit panel 5 (incomplete unit panel) located at the boundary with the straight portion 21a will be described. Of the unit panels located at this end, the lower half panel portion 5b is a complete half panel portion with the horizontal ridge line 52 as its base and the top portion 53 as its apex, while the upper half panel portion 5a is an incomplete half panel portion with the horizontal ridge line 52 as its base but no top portion, and is provided with a linearly inclined surface X1 that slopes almost linearly from the horizontal ridge line 52 toward the axial opening end toward the outside of the can, and a curved inclined surface X2 that gradually becomes gentler from the linearly inclined surface X1 and transitions to the straight portion 21a. Also, the inverted triangular region adjacent to the upper half panel portion 5a in the circumferential direction is a partial cylindrical region Y in which part of the cylindrical surface shape of the straight portion 21a has entered, and the boundary ridge line 51 is not bent to a sufficient degree during processing. Therefore, the partial cylindrical region Y Part of a cylindrical surface crosses the boundary ridge line 51 and enters the upper half panel portion 5a, and continues to the curved inclined surface X2 so as to surround the linear inclined surface X1 having high shape rigidity near the horizontal ridge line 52. The inventors have discovered that for the ambiguous shape extending from this partial cylindrical region Y to the curved inclined surface X2, by making the panel inclination angle or panel depth of the incomplete half panel portion smaller than the panel inclination angle or panel depth of the other complete half panel portion, the axial load can be distributed geometrically and the buckling strength can be increased.

[0016] Panel tilt angle First, the panel tilt angle will be described. 2(B), the panel inclination angles θa, θb of each half panel portion 5a, 5b are the panel inclination angles θa, θb formed between each half panel portion 5a, 5b and the can axis O on a center plane M that passes through the can axis (central axis) N of the can body 21 and the midpoint m of the horizontal ridge line 52 of the unit panel 5. More specifically, the panel inclination angle is the angle between a contour line Z (central axial direction contour line) on the outer surface of the unit panel 5 cut at the center plane M that passes through the can axis O of the can body and the midpoint m of the horizontal ridge line 52 of the unit panel 5, and a reference line L1 that passes through the midpoint m on the center plane M and is parallel to the can axis O. The incomplete half panel portion is a portion that transitions to a cylindrical surface, and does not have a triangular planar shape like other complete half panel portions.Instead, the portion that rises from the horizontal ridge line 52 rises linearly, and the inclination angle gradually decreases as it transitions to the non-processed area, resulting in a curved surface configuration.In this embodiment, the angle of this linear inclined surface X1 is considered to be the panel inclination angle. In the present invention, the panel inclination angle of the incomplete half panel portion is set smaller than the panel inclination angle of the complete half panel portion. As a result, when an axial compressive load is applied, the component of the force acting in the direction of protruding outward from the can at the stress concentration point of the compressive stress generated on the extension of the diagonal ridge (boundary ridge) 51 of the incomplete half panel portion located at the boundary of the non-processed area is smaller than the force acting on the top of the polyhedron wall, and the tensile stress acting between the stress concentration points is also smaller, resulting in a structure that is less susceptible to buckling deformation than conventional structures and increasing buckling strength. If the ratio of the panel inclination angle of this incomplete half panel portion to the panel inclination angle of the complete half panel portion is defined as inclination angle ratio α [%], then the inclination angle ratio α is given by the following formula, where N is the number of corners of the polygonal shape of the cross section perpendicular to the axis, passing through the horizontal ridge line 52 of the polyhedron wall 4 and perpendicular to the can axis O (the central axis of the can body 2): α≦0.50×N+59.0 The configuration satisfies the following formula. In this way, the buckling strength near the boundary with the non-processed portion can be more reliably increased.

[0017] About Panel Depth The panel depth of the complete half panel portion of each unit panel 5 is the distance, in a direction perpendicular to the can axis O, between the top of each half panel portion of each unit panel and the midpoint m on a center plane M that passes through the can axis O of the can body 21 and the midpoint m of the horizontal ridge line 52 of the unit panel 5. In this embodiment, it is the distance, in a direction perpendicular to the can axis O, from a reference line (top outer diameter line) L2 drawn parallel to the can axis O through the top to the position of the horizontal ridge line on the center plane M, i.e., to the midpoint m of the horizontal ridge line. The panel depth of the incomplete upper half panel portion 5a1 located at the boundary with the upper straight portion 21a is the distance from the upper straight portion 21a to the midpoint m of the horizontal ridge line 52 in a direction perpendicular to the can axis O on the center plane M passing through the midpoint of the horizontal ridge line. In the present invention, the panel depth of the incomplete half panel portion is set smaller than the panel depth of the complete half panel portion. By setting it in this way, just like with the panel inclination angle, when an axial compressive load is applied, the component of the compressive stress generated by the incomplete half panel portion located at the boundary of the non-processed area, which causes the stress concentration portion of the compressive stress to protrude outward from the can, is smaller than the force acting on the top of the polyhedron wall.This also reduces the tensile stress acting between the stress concentration portions, resulting in a structure that is less susceptible to buckling deformation than conventional structures and increasing buckling strength. Let β [%] be the ratio of the panel depth of the incomplete half panel portion located at the boundary to the panel depth of the complete half panel portion, and let N be the number of corners of the polygonal shape of the axis-perpendicular cross section that passes through the horizontal ridge line of the polyhedral wall and is perpendicular to the central axis of the can body. β≦3.50×N+12.9 The configuration satisfies the following formula. In this way, the buckling strength near the boundary with the non-processed portion can be more reliably increased.

[0018] The ambiguous shape of this incomplete half panel portion, from the partial cylindrical region Y to the curved inclined surface X2, changes depending on the contact state of the forming mold during the forming process in the manufacturing method described below; by reducing the degree of forming, the shape becomes closer to a cylinder, dispersing the axial load and increasing the buckling strength. In the present invention, the axial distance (L11 in Figure 5) from the tip of the forming region W sandwiched between the inner and outer mold tools during forming of the incomplete half panel portion to the transverse ridge line 52 is set shorter than the axial distance (L10 in Figure 5) from the transverse ridge line 52 to the top 53 of the complete half panel. The forming region W is the distance to the end position of the oblique ridge line 51 that remains as a forming mark on the edge portion of the inner tool. Specifically, this distance is preferably set to 70% or less of the axial distance from the lateral ridge to the top of the complete half panel.

[0019] Manufacturing method Next, a method for manufacturing a metal can according to this embodiment will be described with reference to FIGS. FIG. 3 shows an example of a mold used in the manufacturing method. As shown in the figure, a partial axial region of the body blank 400 is sandwiched from the inner and outer peripheries by the inner tool 200 and the outer tool 300, and by rotating the inner tool 200 and the outer tool 300 in synchronization, the convex portions 305 provided on the periphery of the outer tool 300 are pressed into the concave portions 205 of the unit panel shape provided on the periphery of the inner tool 200, thereby successively forming the unit panels 5. In other words, the inner tool 200 presses the boundary ridge 51 of the body blank 400 outward to form a mountain. At the same time as folding, the area surrounded by the boundary ridge 51 is depressed inward by the outer molding tool 30 to form the unit panel 5. The outer die tool 300 is not a rotating body, but may be a known fan-shaped tool provided with convex portions on the peripheral surface of a circular arc, or may be a tool in which the convex portions are arranged linearly on a plane and moved linearly. FIG. 4 shows the pattern of the recesses 205 of the inner tool 200 and the pattern of the protrusions 305 of the outer tool 300. On the outer peripheral surface of the inner mold tool 200, n recesses 205 for forming unit panels and a panel row forming section 250 consisting of (n-1) recesses 205 shifted in phase by half are formed alternately in the circumferential direction, corresponding to the polyhedron wall 4. The recess 205 of the inner mold tool 200 has a bend line 252 corresponding to the horizontal ridge line 52 of the unit panel 5 as its base, and has a triangular upper half panel forming surface 205a that forms the upper half panel portion 5a, and a triangular lower half panel forming surface 205b that forms the lower half panel portion 5b, and each of the upper and lower half panel forming surfaces 205a, 205b is inclined in the direction in which the distance from the rotation axis increases from the bend line 252 that serves as the base toward the apex of the triangle. The convex portion 305 of the outer mold tool 300 is configured to sandwich the body blank 400 between itself and the concave portion 205, and to roll along with the rotation of the inner mold tool 200. It has an arc-shaped ridge line 352 for forming the horizontal ridge line 52, and is provided with an upper half panel pressing surface 352a and a lower half panel pressing surface 352b separated by this arc-shaped ridge line 352, which form parts of opposite cones that match the inclination of the upper half panel forming surface 205a and the lower half panel forming surface 205b.

[0020] Next, the molding of the boundary between the straight section, which is the non-machined region, and the polyhedron wall 4 will be described with reference to Fig. 5. Fig. 5(A) is a schematic plan view of the main part of the inner mold tool that molds the polyhedron wall near the boundary of the upper straight section, (B) is a schematic cross-sectional view of the molding state by the inner mold tool and outer mold tool at the B-B cross section position of (A), and (C) is a schematic cross-sectional view of the molding state by the inner mold tool and outer mold tool at the CC cross section position of (A). The upper half-panel (incomplete half-panel) forming surface 205a of the first recess 205(1) corresponding to the first unit panel 5(1), which is located at the boundary between the polyhedron wall 4 and the upper straight portion 21a, has a relief portion 205c whose tip is cut in the axial direction (see Figures 5(A) and 5(B)), and the axial distance L11 from the bending line 252 to the relief portion 205c in the contact area that comes into contact with the body blank 400 (in terms of the inner tool, the distance parallel to the rotation axis of the inner tool, parallel to the central axis of the body blank, and parallel to the axial direction of the can of the metal can being formed) is set to be shorter than the axial distance L10 from the bending line 252 to the top 253 of the half-panel forming surfaces 205a, 205b of the complete half panel portion. The contact area of ​​the upper half panel forming surface 205 a of the recess 205 becomes the forming area of ​​the upper half panel portion 5 a (incomplete half panel portion) of the unit panel 5 at the boundary with the straight portion 21 a of the metal can 1 . In Figure 5(A), the part marked with an x ​​is the area where both the outer tool 300 and the inner tool 200 come into contact with the body blank 400 to form it, the area of ​​the escape portion 205c marked with a dot (·) is the area where the convex upper half panel pressing surface 352a of the outer tool 300 comes into contact with it to form it, but the inner tool 200 does not come into contact with it, and the hollow inverted triangular area 210 is the area where the cylindrical portion 205d of the outer tool 300 comes into contact with it to maintain the cylindrical shape, but is not pressed and is not formed. For this molding area, the axial distance L11 from the bending line 252 to the tip of the contact area (the boundary with the relief portion 205c) is preferably 70% or less of the axial distance L10 from the bending line 252 to the top 253 of the half panel molding surfaces 205a, 205b of the complete half panel portion, and more preferably 64% or less.

[0021] Next, an evaluation test for the axial load of the metal can thus formed will be described. In the test, as in the present embodiment, a metal can manufactured by limiting the contact area of ​​the inner mold tool at the incomplete half panel portion at the boundary with the straight portion was used as an example, and a metal can manufactured by not limiting the contact area of ​​the inner mold tool was used as an example. The number of corners in the AA cross section in Figure 1 and the thickness of the incomplete half panel part (boundary) were changed. Comparative Examples 1 and 2 and Examples 1 and 2 are 13-sided aluminum cans for 350 ml beverages. The thicknesses of the incomplete half panel portions (boundaries) are 0.118 mm and 0.097 mm, respectively. Comparative Examples 3 and 4 and Examples 3 and 4 are 16-sided aluminum cans used for 350 ml beverage cans, and the thicknesses of the incomplete half panel portions (boundaries) are 0.118 mm and 0.106 mm. Comparative Examples 5 and 6 and Examples 5 and 6 are 16-sided aluminum cans used for 500 ml beverage cans, and the thicknesses of the incomplete half panel portions (boundaries) are 0.105 mm and 0.102 mm. In all of the metal cans of Comparative Examples 1 to 6, the contact area of ​​the inner molding tool 200 with the body blank 400 was formed to be 100% of the contact area of ​​the complete half panel portion. Regarding the examples, the 13-sided metal cans of Examples 1 and 2 are formed such that the contact area of ​​the inner tool 200 with the body blank 400 is 64% of the contact area of ​​the complete half panel portion. The 16-sided metal cans of Examples 3 to 6 are formed such that the contact area of ​​the inner tool 200 with the body blank 400 is 70% of the contact area of ​​the complete half panel portion.

[0022] Measurement of panel tilt angle and panel depth In the evaluation test, the panel inclination angle and panel depth were measured as elements that characterize the shape of the incomplete half panel portion at the boundary. FIG. 6 shows the panel tilt angle and panel depth for each unit panel in one panel row. In the figure, the five unit panels 5 in the panel row 50 are numbered in ascending order, with the unit panel located at the end on the upper straight section 21a side being numbered 1, and numbered 5(1), 5(2), ... 5(5) toward the lower straight section side, and the upper half panel portion 5a and lower half panel portion 5b of each unit panel 5 are numbered 5a1, 5b1, ... 5a5, 5b5. For each unit panel 5, the two panel tilt angles of the upper half panel portion and the lower half panel portion are measured, and the respective panel tilt angles θa and θb are defined as θa1, θb1, . . . θa5, θb5. In addition, the two panel depths of the upper half panel portion and the lower half panel portion are measured, and the respective panel depths are defined as da1, db1, . . . da5, db5. The upper half panel portion 5a1 of the first unit panel 5(1) and the lower half panel portion 5b5 of the fifth unit panel 5(5) are incomplete half panel portions.

[0023] Figure 7 shows the device used to measure the panel tilt angle and panel depth. Panel tilt angle measurement A metal can 1 is placed on two V-blocks 102 placed on a measuring table 103 so that the straight portions 21a, 21b of the can body 2 are in contact with each other, and the can axis O of the can body 2 is aligned horizontally. Then, a probe 101 of a shape measuring device 100 is brought into contact with the can body and slid in the direction of the can axis O to obtain contour shape data. A Contracer CV-4100 manufactured by Mitutoyo Corporation was used as the measuring device 100. The obtained contour shape data is converted into CAD data, and the angle between each half panel and a horizontal line (parallel to the can axis) is measured on the CAD. The incomplete half panel portions 5x at both ends have linear inclined surfaces near the horizontal ridges 52, but become curved halfway through, so the inclination angle on the linear inclined surfaces is measured. Panel depth measurement As with the panel tilt angle, the contour shape data is converted into CAD data, and the vertical distance between each peak or straight section and the horizontal ridge line is measured on the CAD.

[0024] Table 1 shows the panel tilt angles and panel depths of Comparative Examples 1-6 and Examples 1-6.

[0025] [Table 1]

[0026] The panel inclination angles θa and θb of the upper half panel portion and the lower half panel portion of each unit panel 5 are determined by the thickness distribution Since there are variations depending on factors such as the quality and processing accuracy, the average panel inclination angle of each complete half panel section is taken, and the ratio of the average panel inclination angle of the incomplete half panel section to this average panel inclination angle of the complete half panel section is specified. That is, the ratio was calculated from the average value [(θa1 + θb5) / 2] of the panel inclination angle θa1 of the first upper half panel portion 5a1, which is an incomplete half panel portion, and the average value [(θb1 + θa2 + θb2 + ·· + θa5) / 8] of the panel inclination angles (θb1, θa2, θb2, ··· θa5) of the upper half panel portions and lower half panel portions (5b1, 5a2, 5b2, ··· 5a5) that make up the other complete half panel portions. This ratio is referred to as the panel inclination angle ratio α, and is expressed as a percentage. That is, the panel inclination angle ratio α is expressed by the following formula. α=[[(θa1+θb5) / 2] / [(θb1+θa2+θb2+ · · +θa5) / 8]] x 100 Similarly, the average value ((da1+db5) / 2) of the panel depth da1 of the first upper half panel portion 5a1, which is an incomplete half panel portion, and the panel depth db5 of the fifth lower half panel portion 5b5 is calculated as a ratio from the average value ((db1+da2+db2+··+da5) / 8) of the panel depths of the complete half panel portions (db1, da2, db2, ···da5). This ratio is referred to as the panel depth ratio β, and is expressed as a percentage. In other words, the panel depth ratio β is expressed by the following formula. β=[[(da1+db5) / 2] / [(db1+da2+db2+···+da5) / 8]] x 100

[0027] (Measurement results of panel tilt angle and panel depth) FIG. 8A is a graph showing the relationship between the panel tilt angle ratio α and the number of angles shown in Table 1. As is clear from the graph, Examples 1 to 6 all have lower values ​​than Comparative Examples 1 to 6, and are clearly separated. The ratio α of the panel inclination angle tends to increase as the number of corners N of the polyhedral wall 4 increases, and is thought to change proportionally between 13 and 16 corners. Therefore, a proportional distribution is made, and the area below the line passing through the maximum value at 13 corners (65.5% in Example 2) and the maximum value at 16 corners (67% in Example 4) is shown. α≦0.50×N+59.0 It is preferable to set the panel tilt angle of the incomplete half panel portion so that it falls within this region. In other words, for a 16-sided polygon, it is preferable to set the ratio to 67% or less, and for a 13-sided polygon, it is preferable to set it to 65.5% or less.For polygons larger than 14-sided, 15-sided, or 16-sided, it is preferable to set it to a ratio equal to or less than the ratio calculated by the proportional distribution formula above. The meaning of the panel inclination angle ratio α in the 13-angle and 16-angle cases is related to the contact range of the inner mold tool 200 with the body blank 400, and is the panel inclination angle ratio α at which an improvement in buckling load begins to be observed, which was experimentally determined, and can be set to, for example, around 66.7% or 70%.

[0028] 8(B) is a graph showing the relationship between the panel depth ratio β and the number of corners shown in Table 1. As is clear from the graph, Examples 1 to 6 all have lower values ​​than Comparative Examples 1 to 6, just like the panel inclination angle, and are clearly separated. As the number of corners N of the polyhedral wall 4 increases, the panel depth ratio β tends to increase, just like the panel inclination angle, and is thought to change proportionally between 13 and 16 corners. Therefore, a proportional distribution is made, and the area below the line passing through the maximum value at 13 corners (58.4% for Example 2) and the maximum value at 16 corners (68.9% for Example 4) is shown. β≦3.50×N+12.9 It is preferable to set the panel depth of the incomplete half panel portion so that it falls within this region. In other words, if it is 13-sided, the ratio is 58.4% or less, and if it is 16-sided, the ratio is 68.9% or less. It is preferable to set it so that it is below the square root of the square root of the periphery, and if it is larger than 14, 15 or 16 square roots, it is preferable to set it to a ratio equal to or less than the ratio calculated by the proportional distribution in the above formula. The meaning of the panel depth ratio β for the 13-angle and 16-angle corners is that, like the panel inclination angle, it is related to the contact area between the inner tool 200 and the body blank 400, and the panel depth ratio β at which an improvement in axial load begins to be observed was experimentally determined.

[0029] Next, a method for measuring the buckling strength will be described. The buckling strength was measured using an Autograph (model number: AG-2000D) manufactured by Shimadzu Corporation. First, a metal can 1 was placed on the pressure table 61 of the measuring device 6 with the flange 24 facing upward, and a neck reinforcement jig 62 was placed on the opening of the metal can 1 as shown in Figure 8(B). Next, as shown in Figure 8(A), a compressive load was applied to the neck reinforcement jig 62 placed on the metal can 1 at a compression rate of 10 mm / min using the testing device, and a graph was output with the amount of compression on the horizontal axis and the compressive load on the vertical axis. Since the compressive load decreases when buckling occurs, the maximum value on the graph was read and this value was taken as the buckling strength. At least 12 cans were measured, and the average was calculated.

[0030] (Test results) Table 2 shows the results of measuring the buckling strength of the metal cans of Comparative Examples 1 to 6 and Examples 1 to 6. In Table 1, (n) is the number of samples measured. Comparing Comparative Example 1 with Example 1, the average value of the buckling strength of Comparative Example 1 was 1165N, and the average value of the buckling strength of Example 1 was increased to 1174N. Comparing Comparative Example 2 with Example 2, the average value of the buckling strength of Comparative Example 2 was 794N, while the average value of the buckling strength of Example 2 increased to 831N. Comparing Comparative Example 3 with Example 3, the average value of the buckling strength of Comparative Example 3 was 1400N, and the average value of the buckling strength of Example 3 was 1383N. Comparing Comparative Example 4 with Example 4, the average value of the buckling strength of Comparative Example 4 was 1084N, while the average value of the buckling strength of Example 4 increased to 1129N. Comparing Comparative Example 5 with Example 5, the average value of the buckling strength of Comparative Example 5 was 1138N, and the average value of the buckling strength of Example 5 was 1238N. Comparing Comparative Example 6 with Example 6, the average value of the buckling strength of Comparative Example 6 was 977N, and the average value of the buckling strength of Example 6 was 1081N. The buckling strength is higher in all the examples except for Comparative Example 3 and Example 3. In the case of Example 3, the buckling strength is slightly reduced to 98.8%, but when measurement error is taken into account, it is judged to be almost unchanged. Example 3 has a thick plate, and when the plate thickness is thick, the buckling strength tends to depend more on the plate thickness than on the shape of the incomplete half panel portion at the boundary. The thinner the panel thickness, the greater the effect of the shape change characterized by the panel inclination angle and panel depth of the incomplete half panel portion in this embodiment. From the results in Table 2, when the panel thickness of the incomplete half panel portion at the boundary is 0.106 mm or less, the effect of increasing the buckling strength is more pronounced for both 13-sided and 16-sided panels. In addition, when comparing the 350ml, the buckling strength is higher than that of the 13-sided (Example 1, Example 2). The 16-sided square (Examples 3 and 4) is larger, but in the 16-sided square, 350m The buckling strength of the 500 ml cans (Examples 5 and 6) is smaller than that of the 100 ml cans (Examples 3 and 4). This is because the length of the 500 ml can body is longer. When comparing the same capacity, Examples 5 and 6 also have a higher buckling strength than Comparative Examples 5 and 6. Thus, the magnitude of the buckling strength itself differs depending on the capacity and dimensions of the container, but the buckling strength can be increased by selecting the panel inclination angle ratio and panel depth ratio within appropriate ranges.

[0031] [Table 2]

[0032] In the above embodiment, the panel row having five unit panels and the panel row having four unit panels shifted by half a phase are used. There is a panel row having unit panels, and the panel row having five unit panels has an incomplete half panel portion at both ends, but it is also possible for the number of unit panels in the two types of panel rows to be the same, with one panel row having an incomplete half panel portion at one axial end and the other punch row having an incomplete half panel portion at the other axial end. In the above embodiment, the polyhedron wall is formed over the entire circumference, but it may be formed only partially in the circumference.Furthermore, the present invention is also applicable to a case where a plurality of polyhedron walls are arranged in the axial direction with non-machined portions between them. Furthermore, although the above embodiment has a shape having straight portions (unprocessed areas) on both the opening end side and the bottom side, the present invention can also be applied to a metal can having a straight portion (unprocessed area) only on one side of the opening end side or the bottom side. In other words, the present invention can be applied to the shape of an incomplete half panel portion located at the boundary with the unprocessed area. [Explanation of symbols]

[0033] 1 metal can 4 Polyhedral wall 5 Unit Panel 50 panel rows 51 Boundary ridge (diagonal ridge), 52 Lateral ridge, 53 Summit 5a Upper panel section, 5b Lower panel section 5a1 Upper half panel part (incomplete half panel part), 5b5 Lower panel part (incomplete half panel part) 21 can body, 21a, 21b straight portion (non-processed area) 22 neck portion, 23 bottom portion, 24 flange 100 Shape measuring device 101 contact point, 102 V-block, 103 measuring table 6. Measuring equipment 61 Pressure table, 62 Neck reinforcement jig 200 Internal tool, 205 Recess 205a Upper half panel molding surface, 205b Lower half panel molding surface 205b Half panel molding surface 250 Panel row molding, 251 Ridge line, 252 Bending line 300 External mold tool 305 convex part, 352 arc-shaped ridge 400 Body Blank L1 reference line, L2 reference line L10, L11 Axial distance M center plane, O can axis (center axis) W Molding area X1 Straight inclined surface, X2 Curved inclined surface Y partial cylindrical region Z Contour m midpoint, θa, θb Panel tilt angle

Claims

1. a polyhedron wall formed of a number of unit panels separated by convex boundary ridges in a part of the can body; Each unit panel has a diamond shape defined by the diagonal ridge lines as the boundary ridge lines, and has four apexes in total, including two apexes located on a central plane passing through the central axis of the can body and two apexes located at positions symmetrical with respect to the central plane, and has a valley-folded horizontal ridge line that connects the apexes located at positions symmetrical with respect to the central plane and is perpendicular to the central plane, The polyhedron wall has a plurality of unit panels arranged in rows parallel to the central axis of the can body, the unit panels being alternately arranged with a half-phase offset from each other in the circumferential direction, and has a polygonal cross section perpendicular to the axis, which crosses the horizontal ridge line of the unit panel and is perpendicular to the central axis of the can body, In a method for manufacturing a metal can, when an area of ​​the can body where the polyhedron wall is not formed is defined as a cylindrical unprocessed area, a half panel portion formed on the side of the horizontal ridge line of a unit panel located at the boundary between the polyhedron wall and the unprocessed area toward the unprocessed area is an incomplete half panel portion having the horizontal ridge line as a base and a pair of diagonal ridge lines whose interval narrows as the distance from the horizontal ridge line increases, and which do not form a top, and the other half panel portions are complete half panel portions formed by the horizontal ridge lines and the diagonal ridge lines, a region circumferentially adjacent to the incomplete half panel portion is a partial cylindrical region into which a part of the cylindrical surface shape of the non-machined region is inserted; A method for manufacturing a metal can, characterized in that the axial distance parallel to the central axis from the tip of the forming region with which an inner mold tool comes into contact when forming the incomplete half panel portion to the lateral ridge line is made shorter than the axial distance from the lateral ridge line to the top of the complete half panel portion, thereby forming the partial cylindrical region so that a portion of the cylindrical surface shape extends beyond the oblique ridge line and enters the incomplete half panel portion.

2. 2. The method for manufacturing a metal can according to claim 1, wherein the axial distance from the tip of the forming region to the transverse ridge line in a direction parallel to the central axis is set to 70% or less of the axial distance from the transverse ridge line to the top of the complete half panel.

3. 3. The method for manufacturing a metal can according to claim 1, wherein the distance of the forming region is the distance from a horizontal ridge line to an end position of the oblique ridge line.

4. 4. The method for manufacturing a metal can according to claim 1, wherein the thickness of the incomplete half panel portion is 0.106 mm or less.

5. 5. The method for manufacturing a metal can according to claim 1, wherein a cross section passing through a horizontal ridge line of the unit panel and perpendicular to the central axis of the can body has 13 or more sides.

6. a partial axial region of a cylindrical body blank is sandwiched between an inner mold and an outer mold, a boundary ridge line of the body blank is folded outward by the inner mold, and an area surrounded by the boundary ridge line is depressed inward by the outer mold to form a plurality of unit panels and form a polyhedron wall, and the polyhedron wall and a cylindrical unprocessed region where the polyhedron wall is not processed are formed in the body blank; the unit panels are rhombic in shape defined by the diagonal ridge lines as the boundary ridge lines, and have a total of four apexes, two apexes located on a central plane passing through the central axis of the body blank and two apexes located symmetrically with respect to the central plane, and have a horizontal valley fold ridge line connecting the apexes located symmetrically with respect to the central plane and perpendicular to the central plane, and when an area of ​​the body blank where the polyhedral wall is not formed is defined as a cylindrical unprocessed area, a half panel portion formed on the unprocessed area side of the horizontal ridge line of the unit panel located at the boundary between the polyhedral wall and the unprocessed area is an incomplete half panel portion where a pair of diagonal ridge lines having the horizontal ridge line as a base and narrowing in distance as they move away from the horizontal ridge line do not form an apex, and the other half panel portions are complete half panel portions formed by the horizontal ridge line and the diagonal ridge line, a region circumferentially adjacent to the incomplete half panel portion is a partial cylindrical region into which a part of the cylindrical surface shape of the non-machined region is inserted; a method for manufacturing a metal can, characterized in that the incomplete half panel portion is formed by making the contact area of ​​the inner mold with the body blank smaller than the contact area of ​​the complete half panel portion, so that a part of the cylindrical surface shape of the partial cylindrical region extends beyond the oblique ridge line and enters the incomplete half panel portion.

7. 7. The method for manufacturing a metal can according to claim 6, wherein the incomplete half panel portion is formed such that the contact area of ​​the inner mold with the body blank is 70% or less of the contact area of ​​the complete half panel portion.

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