JP2023009470A - Manufacturing method of can - Google Patents

Abstract

To provide a manufacturing method of a can capable of reshaping a can bottom part of a primary can body by a simple constitution.SOLUTION: A manufacturing method of a can includes a primary can body formation step for forming a primary can body having a cylindrical barrel part, and such a can bottom part that a projection, an inner wall part, a dome part and an arc-shaped part are formed on the can bottom part; and a reshaping step for reshaping the can bottom part of the primary can body. In the reshaping step, in the state where a tip of the projection is supported by a support plane orthogonal to a can axis, a peripheral edge part of the dome part is pressed from inside the cylindrical barrel part, to thereby bend the arc-shaped part, and to form an upper side bent part having a small curvature radius.SELECTED DRAWING: Figure 7

Description

TECHNICAL FIELD The present invention relates to a method for manufacturing a can filled with contents such as a beverage.

2. Description of the Related Art Conventionally, cans filled with contents such as beverages have a cylindrical body and a can bottom integrally connected to one end of the cylindrical body. a circumferential ground contact portion protruding in the direction of the ring, an outer peripheral bottom portion connecting the cylindrical body and the circumferential ground contact portion, a rising portion inside the circumferential contact portion, and a bent portion at the rising portion and a connected dome portion. In recent years, with the thinning (lightening) of can sheet materials, it has been proposed to apply a reforming process to increase the strength of the bottom of the can. As an example of such a can reforming method, for example, a can manufacturing method described in Patent Document 1 is known.

In the method for manufacturing a can described in Patent Document 1, first, a drawing and ironing step is performed to form a dome portion that is recessed inward on the can axis and a dome portion that protrudes outward on the outer peripheral edge of the bottom portion of a cylindrical body portion. At the same time, an annular convex portion extending along the circumferential direction around the can axis is formed. The annular convex portion has a distal end located at the most distal end, an inner wall portion extending substantially straight connecting the distal end portion and the bent portion, and an outer wall portion connecting the distal end portion and the lower end portion of the cylindrical body. A bottom reforming step is provided in which the inner wall portion of the annular projection is subjected to bottom reforming processing to form an annular recessed portion that is recessed radially outward and extends over the entire circumference of the inner wall portion.

In the above-described bottom reforming step, while supporting the neck portion of the can before reforming (hereinafter referred to as the primary can body), the forming roller is brought into contact with the inner wall portion of the bottom portion of the can precursor, and the can axis is moved over the inner wall portion. By rolling over the entire circumference in the circumferential direction, the inner wall portion is formed with an annular concave portion extending over the entire circumference in the circumferential direction. However, when the can bottom portion of the can body is reformed by this method, the can may be shaken along with the movement of the forming rollers, resulting in unstable processing.

On the other hand, the reforming step in the can manufacturing method described in Patent Document 2 uses a cylindrical punch, a dome pressing tool, a doming die, and a hold-down ring to perform the reforming step. Specifically, while the dome portion is pressed by the dome pressing tool and the doming die, the outer wall portion of the can is held by the punch and the hold-down ring, and the can is lowered relative to the dome pressing tool and the doming die to form an annular shape. After forming the convex portion, the punch and the hold-down ring are then relatively raised to press the tip of the annular convex portion into the groove defined by the hold-down ring and the outer surface of the doming die to form a circumferential shape. A grounding portion, a peripheral bottom portion and a rising portion are formed. In other words, while restricting the dome portion, the annular convex portion is pushed downward and radially inward to form an inverse taper in which the diameter increases in the height direction at the rising portion.

By the way, in the can manufacturing method described in Patent Document 2, while the dome portion is regulated by the dome pressing tool, the outer wall portion of the can is held by the punch and the hold-down ring, and the can is placed relative to the dome pressing tool and the doming die. Since it is necessary to use a special press that moves vertically vertically, the apparatus for reforming the bottom of the can (primary can body) before reforming is special and large.

In order to solve the above-described problems, for example, a can body forming apparatus in which a cylindrical body and a can bottom are integrally formed is proposed in Patent Document 3. The can body forming apparatus described in Patent Document 3 has a concave dome portion in the center of the can bottom portion, and the leg portion shape is formed on the can body in which the annular leg portion is formed around the dome portion. A reform-molding tool is provided, the tool being inserted into the can body and comprising a pressing body for contacting the inner surface of the dome and a mold for shaping the inwardly curved ends of the lower ends of the legs.

Japanese Patent No. 6414957 JP-A-9-285832 WO2021/95309

By the way, in the apparatus described in Patent Document 3, the inner surface of the dome portion is formed in a state in which a mold having an inclined surface inclined radially inward on the outer surface side of the can bottom portion is placed facing the can bottom portion. is pressed by a pressing body, the structure for supporting the bottom side of the can becomes complicated. In addition, the can bottom is formed by pressing the periphery of the dome portion while supporting the outer peripheral surface of the leg portion on the inclined surface, deforming the dome portion along the inclined surface, and protruding part of the annular leg portion downward. Therefore, the shape of the can bottom may vary.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a method of manufacturing a can that enables reshaping of the can bottom portion of a primary can body with a simpler structure.

A method of manufacturing a can according to the present invention includes a cylindrical body and a can bottom integrally connected to one end of the cylindrical body, and an annular ring extending outward in the can axial direction at the can bottom. a dome portion formed on the can axis of the can bottom portion and recessed inward in the can axis direction; and a concave arcuate portion continuous with the outer peripheral edge of the dome portion. and a reshaping step of reshaping the can bottom portion of the primary can body, wherein in the reshaping step, the tip of the projecting portion is aligned with the can shaft. While being supported by orthogonal support planes, the peripheral portion of the dome portion is pressed from the inside of the cylindrical body portion to bend the arc portion to form an upper bent portion with a small radius of curvature.

In the present invention, in the reshaping process, the peripheral edge of the dome portion is pressed to bend the arc-shaped portion to form the upper bent portion with a small radius of curvature. As long as it is provided, for example, there is no need to dispose a molding die or the like for supporting the outer surface of the protrusion in the radial direction as in Patent Document 3, and the equipment used in the remolding process can be simplified. In addition, since the tip of the projecting portion is supported by the support plane, the shape after remolding is stabilized.

In a preferred embodiment of the can manufacturing method of the present invention, in the primary can body forming step, an inner wall portion extending upward from a radially inner edge of the projecting portion is formed, and the arc-shaped portion is formed on the dome portion. The outer peripheral edge and the upper end of the inner wall portion are connected to each other, and in the reshaping step, the inner wall portion is bent while the peripheral edge portion of the dome portion is pressed from the inside of the cylindrical body portion to bend the arc-shaped portion. It is preferable that the inner wall portion is inclined to form an inclined wall portion by expanding the upper portion of the inner wall portion radially outward.
In the above-described aspect, the arcuate portion is an upper bent portion with a small radius of curvature, so that the upper bent portion and the inclined wall portion increase the rigidity of that portion. The strength of the can bottom can be increased.

In a preferred embodiment of the can manufacturing method of the present invention, in the reshaping step, a pressing surface having a width extending from the peripheral edge of the dome to above the arc-shaped portion is provided on the punch for pressing the peripheral edge of the dome. is formed so that when the pressing surface presses the peripheral edge of the dome portion, the pressing position on the arcuate portion shifts radially outward sequentially from the connection end with the dome portion. and bend the arc-shaped portion.

In the above-described aspect, when pressing the peripheral portion of the dome portion, the pressing position on the arc-shaped portion is pressed and bent so as to gradually transition from the radially inner side toward the outer position. The upper ends of the connecting inner walls can be spread radially outward to ensure the formation of a stable inclined wall.

In a preferred embodiment of the can manufacturing method of the present invention, in the primary can body forming step, an outer peripheral bottom portion connecting the radially outer edge of the projecting portion and the lower end of the cylindrical body portion is formed on the can bottom portion. The protruding portion is composed of an inner arcuate portion positioned radially inwardly of the primary can body and an outer arcuate portion positioned radially outward from the apex of the protruding portion. forming a lower bent portion with a small radius of curvature continuous to the lower end of the inclined wall portion by bending the inner arcuate portion while pressing the vicinity of the vertex of the inner arcuate portion against the support plane; Preferably, the outer arcuate portion is deformed to have a larger radius of curvature to form an outer curved portion that is continuous with the lower bent portion.

In the above aspect, the rigidity of the portion is increased by the lower bent portion having a small radius of curvature and the inclined wall portion, so that the strength of the can bottom portion can be further increased. In addition, when the lower bend is formed, the outer arcuate portion is deformed to increase the radius of curvature, and the reaction when the inner arcuate portion is pressed against the support plane The portion from the outer curved portion to the outer peripheral bottom portion is pushed up in the can axial direction, and as a result, the height of the can may increase.

As a preferred aspect of the can manufacturing method of the present invention, the reshaping step may be performed using the punch disposed within the cylindrical body and a cradle having the support plane.
In the above aspect, the reshaping process can be performed while the primary can body is sandwiched between the punch and the cradle.

In a preferred embodiment of the can manufacturing method of the present invention, the outer diameter of the cylindrical body portion of the primary can body is 66.1 mm or more and 66.3 mm or less, and the tangential line on the inner surface of the outer peripheral edge of the dome portion is The angle with respect to a plane orthogonal to the can axis is 27° or more and 29° or less, and the radial width of a portion of the pressing surface disposed radially inward of the primary can body from the inner wall portion is 2.0 mm or more. 3.0 mm or less, and the inclination angle of the pressing surface with respect to the plane is 20° or more and the angle of the tangential line with respect to the plane is less than or equal to 20°.

If the radial width of the portion of the pressing surface located radially inward of the primary can body from the inner wall portion is less than 2.0 mm, when the peripheral portion of the dome portion is pressed, the arcuate portion and the inner wall portion are properly aligned. If the thickness exceeds 3.0 mm, the area for pressing the dome portion increases, requiring an excessive pressing force. In addition, when the angle of the tangent to the plane of the inner surface of the outer peripheral edge of the dome portion is 27° or more and 29° or less, and when the inclination angle of the pressing surface to the plane is less than 20° or exceeds the angle of the tangent to the plane, the pressing surface Since the deviation between the inclination angle with respect to the plane and the inclination angle with respect to the plane of the tangential line of the outer peripheral edge of the dome part with respect to the plane becomes large, it is difficult to appropriately deform the arc-shaped part and the inner wall part.

As a preferred aspect of the method for manufacturing a can according to the present invention, in the reshaping step, the pressing surface is pressed against the peripheral edge of the dome portion and pushed in by 1.0 mm or more and 3.0 mm or less.
If the pressing amount of the pressing surface is less than 1.0 mm, the pressing amount is too small to properly reshape the can bottom, and the strength of the can bottom may not be increased. If it exceeds 0.0 mm, the can bottom may deform excessively and the strength of the can bottom may rather decrease. Considering the influence on other processes during actual production (conveyability, can holding and inspection properties in an inspection machine), the pushing amount is more preferably 1.0 mm or more and 2.0 mm or less.

ADVANTAGE OF THE INVENTION According to this invention, the can bottom part of a primary can can be reshaped by simple structure.

Fig. 2 is a front view of the right half of the can bottom portion of the can of one embodiment of the present invention, taken as a cross section passing through the can axis. It is a figure which expands and shows the can bottom part shown in FIG. FIG. 4 is a cross-sectional view showing an enlarged part of a can bottom portion of a primary can formed by further performing a drawing and ironing process on the cup in the drawing and ironing process in the can manufacturing method of the present embodiment. FIG. 4 is a cross-sectional view of a punch for reshaping the can bottom portion of the primary can body of the first embodiment. FIG. 5 is a cross-sectional view showing a state in which the punch shown in FIG. 4 is arranged inside the cylindrical body of the primary can body; 5 is a cross-sectional view showing how the punch shown in FIG. 4 crushes the can bottom of the primary can body. FIG. 7 is an enlarged view of a part of the can bottom shown in FIG. 6; FIG. FIG. 8 is an enlarged view showing a state in which a pressing surface of a punch is in contact with the peripheral portion of the dome portion shown in FIG. 7; FIG. 5 is a diagram showing the angle of the inclined wall portion with respect to the straight line along the can axis when the punch shown in FIG. 5 is a graph showing the maximum pressure resistance when the amount of pressing with which the punch presses the peripheral edge portion and the arcuate portion of the dome portion is varied in the embodiment of the present invention. In the embodiment of the present invention, when the pressing amount of the punch that presses the peripheral edge portion and the arc-shaped portion of the dome portion is changed, the protrusion deformation amount ( It is a graph showing growth amount).

An embodiment of the can manufacturing method according to the present invention will be described below with reference to the drawings.

Although the overall shape of the can body 100 of this embodiment is omitted in FIG. 1, it is a so-called two-piece can. A flange is formed on the outside of the can. After the can body 100 is filled with a content such as a beverage through the opening on the flange side, the lid member is rolled up to seal the opening to form a can.

FIG. 1 shows the can bottom portion 11 of the can body 100 in an enlarged manner, and the right half of the can body 100 shows a cross section passing through the can axis C. As shown in FIG. The can body 100 is made of a thin sheet metal such as aluminum or an aluminum alloy, and as shown in FIG. and a can bottom 11 integrally connected to one end of the cylindrical body 12 .

As shown in FIG. 1, the cylindrical body portion 12 and the can bottom portion 11 are arranged coaxially with each other. Of the directions along the can axis C (can axial direction), the direction from the opening to the can bottom 11 side is the can axial direction outward (downward), and the direction from the can bottom 11 to the opening side is the can axial direction inward. (upward), and in the following description, the vertical direction is defined in the same manner as the direction shown in FIG. A direction orthogonal to the can axis C is called a radial direction. Of the radial directions, the direction approaching the can axis C is radially inward (radially inward), and the direction away from the can axis C is radial outward (radial direction). radially outward). The direction of rotation around the can axis C is defined as the circumferential direction.

In this embodiment, the can bottom portion 11 of the can body 100 connects the cylindrical trunk portion 11 and the circumferential ground portion 114 to the annular ground portion 114 that annularly protrudes outward (downward) in the can axial direction. The outer peripheral bottom portion 117 is connected to the circumferential ground portion 114, extends upward from the end portion of the circumferential ground portion 114, and slopes upward in a direction away from the can axis C. It has a wall portion 113 and a dome portion 111 connected to the inclined wall portion 113 via an upper bent portion 112 . Circular grounding portion 114 is positioned radially inward from vertex 114A of circumferential grounding portion 114, and is continuous with lower curved portion 115 continuing to the lower end portion of inclined wall portion 113, and continuous with lower curved portion 115, It consists of an outer curved portion 116 that continues to the outer peripheral bottom portion 117 .

The dome portion 111 is positioned on the can axis C and has a shape recessed upward (inside the cylindrical body portion 12). The upper bent portion 112 is an arcuate portion that is recessed radially outward of the can body 100 , and the lower end portion is connected to the inclined wall portion 113 . The inclined wall portion 113 extends from the lower end of the upper curved portion 112 while being inclined toward the can axis C as it goes downward. there is The lower bent portion 115 has an arcuate shape projecting inward in the radial direction of the can body 100 , and its lower end is connected to the outer curved portion 116 . The outer curved portion 116 has an arcuate shape extending convexly outward and downward in the radial direction of the can body 100 (in the example shown in FIG. 2, rightward and downward with respect to the plane of the paper), and the radially outward end is It is connected to the outer peripheral bottom portion 117 . Circumferential contact portion 114 consisting of lower bent portion 115 and outer curved portion 116 protrudes most downward in the axial direction of the can and has an annular shape extending along the circumferential direction. When placed on the placement surface in a state of being turned sideways, the connecting portion between the lower bent portion 115 and the outer curved portion 116 contacts the placement surface. The outer peripheral bottom portion 117 has an arcuate shape extending radially inward from the radially outer end portion of the outer curved portion 116 toward the lower end portion of the cylindrical body portion 12 .
In addition, a press mark 118 that is slightly bent in a direction (downward) opposite to the direction in which the dome portion 111 is recessed is formed on the peripheral portion of the dome portion 111 .

As for the dimensions of each portion of the can bottom portion 11 described above, for example, on the outer surface of the can body 100, the curvature radius R1 of the dome portion 111 is 30 mm or more and 37 mm or less, and the curvature radius R2 of the upper bent portion 112 is 1.3 mm or more and 2.0 mm. Hereinafter, the inclination angle (θ2 in FIG. 2) of the inclined wall portion 113 with respect to the can axis C is 6.0° or more and 21.0° or less, and the inner diameter between the apexes 114A of the circumferential grounding portion 114 The distance W1 of the straight line passing through the axis C is 46.8 mm or more and 47.2 m or less, the curvature radius R3 of the lower curved portion 115 is 0.7 mm or more and 1.0 mm or less, and the curvature radius R4 of the outer curved portion 116 is 1.4 mm. 1.8 mm or more, the curvature radius R5 of the outer peripheral bottom portion 116 is 8.0 mm or more and 12.0 mm or less, and the inner diameter between the portions located most radially inward in the lower bent portion 115 (the can axis C connecting the portions) distance) W2 is 44.4 mm or more and 44.6 mm or less, and the inner diameter between the most radially outwardly positioned portions of the upper bent portion 112 (the distance of a straight line passing through the can axis C connecting the portions) W3 is 44.8 mm or more and 45.6 mm or less, and the outer diameter W4 of the cylindrical body portion 12 is 66.1 mm or more and 66.3 mm or less.

[Manufacturing method of can]
In the method of manufacturing a can according to the present embodiment, an aluminum plate is punched and drawn to form a relatively large-diameter shallow cup. A drawing and ironing process for forming a bottomed cylindrical primary can body 200 shown in FIG. ), a reshaping step of reshaping the can bottom portion 21 of the primary can body 200, and an opening portion processing step of processing the opening portion of the other end portion of the cylindrical body portion 22 (processing for reducing the diameter and forming a flange on the opening portion. and a necking process).

[Drawing and ironing process]
In the drawing and ironing process corresponding to the primary can body forming process of the present invention, after the cup is formed, the drawing and ironing process is applied again, thereby forming the can bottom 21 of the primary can body 200 as shown in FIG. A dome portion 211 formed on the can axis C of the bottom portion 21 and recessed inward (upward) in the axial direction of the can, a projecting portion 214 annularly projecting outward (downward) in the axial direction of the can, and the projection. An inner wall portion 213 extending upward from the radially inner edge of the portion 213, an arcuate portion 212 connecting the upper end of the inner wall portion 213 and the outer peripheral edge of the dome portion 211, a radially outer edge of the projecting portion 214 and the cylinder. An outer peripheral bottom portion 215 connecting with one end of the body portion 22 is formed. As shown in FIG. 3, the protruding portion 214 consists of an inner arcuate portion 215 located radially inwardly of the primary can body 200 from its apex 214A, and an outer arcuate portion 216 located radially outwardly. . The angle of the tangential line S1 on the inner surface of the outer peripheral edge of the dome portion 211 with respect to the plane perpendicular to the can axis C is 27° or more and 29° or less.

As shown in FIGS. 5 and 6, the dome portion 211 of the primary can body 200 is positioned on the can axis C and is recessed upward (inside the cylindrical body portion 22). The arcuate portion 212 is an arcuate portion that extends concavely inward and downward in the radial direction of the primary can body 200 (in the example shown in FIG. 3, the lower left direction with respect to the paper surface), and the lower end is the inner wall. 213. The inner wall portion 213 is inclined toward the can axis C from the lower end to the upper end, and the upper end is connected to the lower end of the arcuate portion 212 and the lower end is connected to the radially inner edge of the inner arcuate portion 215 . It is connected. The inner arcuate portion 215 has an arcuate shape extending convexly inward and downward in the radial direction of the primary can body 200 (in the example shown in FIG. 3, the lower left direction with respect to the paper surface), and the lower end thereof is the outer arcuate portion. 216. The outer arcuate portion 216 is formed in an arcuate shape extending convexly outward and downward in the radial direction of the primary can body 200 (in the example shown in FIG. The edge is connected to the perimeter bottom 217 . The projecting portion 214 consisting of the inner arcuate portion 215 and the outer arcuate portion 216 protrudes most downward in the axial direction of the can and has an annular shape extending along the circumferential direction. contact the plane 41; The outer peripheral bottom portion 217 has an arcuate shape extending radially inwardly from the radially outer edge of the outer arcuate portion 216 toward the lower end of the cylindrical body portion 22 .

The various dimensions of each portion of the can bottom portion 21 of the primary can body 200 described above are such that, on the outer surface of the primary can body 200, the curvature radius R11 of the dome portion 211 is 28 mm or more and 37 mm or less, and the curvature radius R12 of the circular arc portion 212 is 2 mm. .1 mm or more and 2.2 mm or less, the diameter between the apexes 214A of the projecting portion 214 (the distance of the straight line passing through the can axis C connecting the apexes 214A) W11 is 47.8 mm or more and 48.1 mm or less, and the inner arc portion 215 The curvature radius R13 is 1.2 mm or more and 1.5 mm or less, the curvature radius R14 of the outer arcuate portion 216 is 2.2 mm or more and 2.5 mm or less, the curvature radius R15 of the outer peripheral bottom portion 217 is 1.5 mm or more and 1.9 mm or less, and the inner side The inner diameter (distance of a straight line passing through the can axis C connecting these portions) W12 between the most radially inward portions of the arc-shaped portion 215 is 43.4 mm or more and 45.6 mm or less, and the radius of the arc-shaped portion 212 is the largest. The inner diameter W13 between the parts located on the outer side of the direction (the distance of the straight line passing through the can axis C connecting the parts) is 43.4 mm or more and 45.6 mm or less, and the outer diameter W14 of the cylindrical body 22 is 66.1 mm or more. 66.3 mm or less.

The curvature radius R12 of the arcuate portion 212 is larger than the curvature radius R2 of the upper bent portion 112, the curvature radius R13 of the inner arcuate portion 215 is larger than the curvature radius R3 of the lower bent portion 114, and the curvature radius R13 of the inner arcuate portion 215 is larger than the curvature radius R3 of the lower bent portion 114. The radius of curvature R14 of 216 is set smaller than the radius of curvature R4 of the outer curved portion 116. As shown in FIG. In addition, the diameter W11 between the apexes 214A of the projecting portion 214 is larger than the distance W1 from the apex 114A of the circumferential ground portion 114 to the can axis C, and the inner diameter between the most radially outward portions of the circular arc portion 212. W13 is set to be smaller than the inner diameter W3 between the portions of the upper bent portion 112 that are located furthest outward in the radial direction.

[Remolding process]
In the reshaping process, the peripheral edge portion 211A of the dome portion 211 (in the example shown in FIG. 8, the arc-shaped portion 212 of the dome portion 211 and The radially inner end of the pressing surface 331 is brought into contact with a region within a certain range from the connection portion of the cylinder 22, and the peripheral edge portion 211A of the dome portion 211 is pushed outward (downward) in the can axial direction from the inside of the cylindrical body portion 22. is executed by pressing . In this reshaping step, as shown in FIGS. 5 and 6, the punch 30 is arranged in the cylindrical body portion 22 of the primary can body 200 and presses the peripheral edge portion 211A of the dome portion 211, and the support plane 41 is provided. Execution is performed using the cradle 40 .

As shown in FIG. 4, the punch 30 has a substantially cylindrical main body portion 31, and the can bottom portion 21 is pressed under the main body portion 31 (the side that abuts on the peripheral edge portion 211A of the dome portion 211). A concave portion 32 is formed so that the central portion of the dome portion 211 does not come into contact with the dome portion 211 at that time. In addition, an annular projecting portion 33 that projects downward in a cylindrical shape is formed on the outer peripheral portion of the recess 32 . A pressing surface 331 having a width extending from the peripheral edge portion 211A of the dome portion 211 to above the arc-shaped portion 212 is formed at the tip portion of the annular projecting portion 33 .

The dimensions of each part of the punch 30 are, for example, a diameter L1 of 44 mm or more and 50 mm or less, an inner diameter L2 of the recess 32 of 19.5 mm or more and 20.75 mm or less, and a width L3 of the pressing surface 331 of 4.25 mm or more and 5.5 mm or less. It is said that

The pressing surface 331 is an inclined surface that protrudes downward toward the radially outer side of the primary can body 200 . The inclination angle θ12 of the pressing surface 331 with respect to the plane perpendicular to the can axis C is set to be less than 20° or the angle of the tangent line S1 with respect to the plane perpendicular to the can axis C.
Further, the pressing surface 331 is designed so that the inner wall portion 213 is arranged near the center in the width direction when the pressing surface 331 comes into contact with the peripheral edge portion 211A of the dome portion 211 . That is, the pressing surface 331 protrudes outward in the radial direction of the primary can body 200 from the inner wall portion 213 . A radial width L4 (see FIG. 7) of a portion disposed radially inward of the primary can body 200 from the inner wall portion 213 is set to 2.25 mm or more and 2.5 mm or less.

Note that if the radial width L4 of the portion of the pressing surface 331 disposed radially inward of the primary can body 200 from the inner wall portion 213 is less than 2.25 mm, when the peripheral edge portion 211A of the dome portion 211 is pressed, There is a possibility that a large pressing mark will be formed because the arcuate portion 212 and the inner wall portion 213 cannot be properly deformed. pressure is required. Further, when the angle θ11 of the tangential line S1 on the inner surface of the outer peripheral edge of the dome portion 211 with respect to the plane perpendicular to the can axis C is 27° or more and 29° or less, the inclination angle θ12 of the pressing surface 331 with respect to the plane perpendicular to the can axis C is less than 20° or exceeds the angle of the tangent S1 with respect to the plane, the inclination angle θ12 of the pressing surface 331 with respect to the plane perpendicular to the can axis C and the inner surface of the outer peripheral edge of the dome portion 211 (connection point with the arc-shaped portion 212) , and the inclination angle θ11 with respect to the plane perpendicular to the can axis C, it is difficult to appropriately deform the arcuate portion 212 and the inner wall portion 213 . In particular, if the inclination angle θ12 is greater than the angle θ11, the pressing surface 331 presses the arcuate portion 212 before the peripheral edge portion 211A of the dome portion 211, and the inner wall portion 213 may not be properly inclined. have a nature.

With the primary can body 200 placed on the support plane 41 of the cradle 40, the punch 30 is placed inside the cylindrical body 22 as shown in FIG. is pressed downward by 1.0 mm or more and 3.0 mm or less (2.0 mm in this embodiment) in a state where the radially inner end of is in contact with the portion P of the peripheral edge portion 211A, thereby reshaping the can bottom 21. to form a can bottom 11.

Specifically, as shown in FIGS. 7 and 8, the tip of the projecting portion 214 is supported by a support plane 41 orthogonal to the can axis C, and the radially inner end of the circumferential pressing surface 331 is the peripheral edge portion. 211A, the peripheral portion 211A of the dome portion 211 is pressed in the axial direction of the can by the pressing surface 331 of the punch 30 from the inside of the cylindrical body portion 22, thereby bending the arc portion 212 and forming the inner wall portion. The inner wall portion 212 is inclined to form the inclined wall portion 113 by expanding the upper portion of the portion 213 radially outward. In this case, since the pressing surface 331 of the punch 31 has a width extending from the peripheral edge portion 211A of the dome portion 211 to above the arcuate portion 212 , the pressing position on the arcuate portion 212 is the connection with the dome portion 211 . By pressing so as to sequentially transition radially outward from the end (peripheral edge), the arc-shaped portion 212 is further bent to form an upper bent portion 112 with a small radius of curvature, while the upper portion of the inner wall portion 213 is radially pushed. It expands outward to form an inclined wall portion 113 . At this time, in the vicinity of the tip of the projecting portion 214 , the inner arcuate portion 215 is further bent while the vicinity of the vertex of the inner arcuate portion 215 is pressed against the support plane 41 , so that the radius of curvature continues to the lower end of the inclined wall portion 113 . A small lower bent portion 115 is formed, and the outer arcuate portion 216 is deformed to have a larger radius of curvature to form an outer curved portion 116 with a larger radius of curvature that is continuous with the lower bent portion 115 . As this lower bend 115 is formed, the outer arcuate portion 216 is deformed to increase the radius of curvature, as well as the reaction as the inner arcuate portion 215 is pressed against the support plane 41 . As a result, the portion from the outer curved portion 116 to the outer peripheral bottom portion 117 is pushed up in the can axial direction, and as a result, the height of the can may increase. Further, since the peripheral edge portion 211A of the dome portion 211 is pressed, the depth (bottom depth) of the dome portion 111 is smaller than the depth of the dome portion 211 of the primary can body 200, and is pressed by the pressing surface 331. Thus, a pressing mark 118 (see FIG. 2) is formed on the inner surface of the dome portion 111 (the portion P where the radially inner end of the pressing surface 331 contacts the peripheral portion 211A of the dome portion 211).

Here, the downward pressing amount of the pressing surface 331 (punch 30) is 1.0 mm or more and 2.0 mm or less. The shape of the can bottom portion and the inclination angle of the inclined wall portion 113 with respect to the can axis C at that time will be described. FIG. 9 is a diagram showing the angles of the inclined wall portions 113, 113A, and 113B with respect to the can axis C when the punch 30 shown in FIG. The inclination angle θ0 with respect to the can axis C passing through the lower end of the inner wall portion 213 of the primary can body 200 is approximately 0°.

As shown in FIG. 9, it can be seen that the greater the pushing amount of the pressing surface 331, the greater the inclination angle of the inclined wall portion with respect to the can axis C. As shown in FIG. Specifically, as an example, the inclination angle θ1 of the inclined wall portion 113A with respect to the can axis C when the pushing amount is 1.0 mm is 3.79°, and the inclination angle θ1 of the inclined wall portion 11 when the pushing amount is 2.0 mm. The inclination angle θ2 with respect to the can axis C is 19.13°, and the inclination angle θ3 with respect to the can axis C of the inclined wall portion 113B when the amount of pushing is 3.0 mm is 50.76°.
If the amount of pressing of the pressing surface 331 is less than 1.0 mm, the amount of pressing is too small to properly reshape the can bottom 21, and there is a possibility that the strength of the can bottom of the can body cannot be increased. However, if the pushing amount exceeds 3.0 mm, the can bottom 21 may be deformed excessively and the strength of the can bottom may be lowered. Also, considering the influence on other processes during actual production (conveyability, can holding and inspection properties in an inspection machine), the pushing amount is more preferably 1.0 mm or more and 2.0 mm or less.

By performing such a reshaping process, the can bottom portion 21 of the primary can body 200 is remolded into the shape of the can bottom portion 11 shown in FIG.
Then, by performing the necking step after the reshaping step, a neck portion and a flange positioned outside the can along the can axial direction from the neck portion are formed at the mouth portion of the upper end portion, The can body 100 is obtained. In the present embodiment, the reshaping process can be performed simply by pressing the peripheral edge portion 211A of the dome portion 211 from the inside of the cylindrical body portion 22 in one direction in the can axial direction. It is performed by the same mechanism as the necking process, which reduces the diameter and flanges the part.
After filling the contents such as a beverage through the opening on the flange side of the can body 100, the opening is sealed by tightening the lid member to form a can.

[Comparison with Patent Document 3]
Here, the can manufacturing method using the apparatus described in Patent Document 3 and the can manufacturing method of the present embodiment will be compared. First, in the can manufacturing method using the apparatus of Patent Document 3, a tapered portion inclined radially inward on the outer surface side of the bottom of the can, a stepped portion connected to the tapered portion, and a stepped portion below the stepped portion Since the inner surface of the dome portion is pressed by the pressing body in a state in which the forming die formed with the continuous planar portion is arranged to face the can bottom portion, the structure for supporting the can bottom portion side becomes complicated. In addition, since it is not the dome portion that the pressing body comes into contact with, but the arc-shaped portion that connects the dome portion and the leg portion, when the arc-shaped portion is pressed by the pressing body, the can axis increases from the lower end to the upper end. The radially inner portion of the leg corresponding to the inner wall portion of the present embodiment, which is inclined toward , is further inclined radially inward. For this reason, in Patent Document 3, a molding die having a complicated shape as described above is used, and when pressing with a pressing body, a part of the annular leg portion is deformed so as to protrude downward along the stepped portion. , it is assumed that the lower end of the inner portion of the leg is first inclined radially inward, but the pressing body presses the upper end of the inner portion of the leg radially inward, so the timing is shifted. And it is difficult to mold it into an accurate shape. Also, although the injection of air from below the dome portion may assist the molding, there is a limit to assisting the molding of metal materials with air. In any case, it is considered difficult to form the can bottom in a stable shape by the method of Patent Document 3.

On the other hand, in the can manufacturing method of the present embodiment, the peripheral edge portion 211A of the dome portion 211 is pressed to bend the arc-shaped portion 212, and the upper portion of the inner wall portion 213 is expanded radially outward. 212 is inclined to form an inclined wall portion 113 . That is, the inner wall portion 213, which inclines toward the can axis C from the lower end to the upper end, is prevented from further inclining in the same direction, and inclines in the opposite direction (opposite side to the can axis). Since the inclined wall portion 113 is formed by tilting, the strength of the can bottom portion 11 can be improved.

In this embodiment, the reshaping process can be performed simply by pressing the peripheral edge portion 211A of the dome portion 211 from the inside of the cylindrical body portion 22 in one direction in the can axial direction. It can be carried out by the same mechanism as the necking process, which performs diameter reduction and flanging. Therefore, there is no need to use a special press as in Patent Document 2, and the can manufacturing cost can be reduced while suppressing an increase in the size of the can manufacturing apparatus. In addition, since the inner wall portion 213 is inclined while pressing the peripheral edge portion 211A of the dome portion 211 to bend the arcuate portion 212 in the reshaping process, the support plane 41 is provided to support the tip of the protruding portion 214 during this period. For example, unlike Patent Document 3, there is no need to dispose a molding die or the like for supporting the outer surface of the projecting portion 214 on the radially outer side, and the equipment used in the remolding process can be simplified. Moreover, since the tip of the projecting portion 214 is supported by the support plane 41, the shape after remolding is stabilized.

Further, when the peripheral edge portion 211A of the dome portion 211 is pressed, the arc portion 212 is pressed and bent so that the pressing position on the arc portion 212 gradually transitions from the inner side in the radial direction toward the outer position. The upper end of the inner wall 213 connecting to 212 can be flared radially outward to ensure a stable ramped wall 113 . Since the arcuate portion 212 forms the upper bent portion 112 with a small radius of curvature, the upper bent portion 112 and the inclined wall portion 113 increase the rigidity of that portion. Even in this case, the strength of the can bottom portion 11 can be increased.

In addition, the lower bent portion 115 having a small radius of curvature and the inclined wall portion 113 increase the rigidity of these portions, thereby further increasing the strength of the can bottom portion 11 . In addition, when the lower bend 115 is formed, the outer arc 216 is deformed to increase the radius of curvature, and the reaction when the inner arc 215 is pressed against the support plane 41 also acts. As a result, the portion extending from the outer curved portion 116 to the outer peripheral bottom portion 117 is pushed up in the can axial direction, and as a result, the height of the can increases.

Further, the reshaping process can be performed while the primary can body 200 is sandwiched between the punch 30 and the cradle 40 . Therefore, for example, the can bottom 21 can be reshaped even when the primary can body 200 is not placed on a horizontal surface.
Further, the pressing surface 331 of the punch 30 has a width that protrudes radially outward of the primary can body 200 from the inner wall portion 213 and is arranged radially inward of the primary can body 200 from the inner wall portion 213 . The radial width L6 of the portion where the contact is made is 2.0 mm or more and 3.0 mm or less, and the inclination angle with respect to the plane of the pressing surface 331 is 20° or more and the angle with respect to the tangent line S1 or less. It is possible to appropriately deform the arcuate portion 212 and the inner wall portion 213 while suppressing the formation of large press marks.

Further, by setting the pushing amount of the punch 30 to 1.0 mm or more and 3.0 mm or less, it is possible to appropriately reshape the can bottom 21 . In this case, the curvature radius R2 of the upper curved portion 112 is 1.3 mm or more and 2.0 mm, the curvature radius R3 of the lower curved portion 115 is 0.7 mm or more and 1.0 mm or less, and the inclination angle of the inclined wall portion 113 with respect to the can axis C. can be 6.0° or more and 21.0° or less, thereby increasing the strength of the can bottom portion 11 .

It should be noted that the present invention is not limited to the configurations of the above-described embodiments, and various modifications can be made to the detailed configurations without departing from the scope of the present invention.
For example, in the above embodiment, the necking process is performed after the reshaping process, but the necking process may be performed simultaneously with the reshaping process. Since the reshaping process of the above embodiment can be performed only with the punch 30 and the cradle 40, the necking process and the reshaping process can be performed at the same time by using a mold that sandwiches the cylindrical body 22 from the outside of the punch 30. It becomes possible to

In the above-described embodiment, the can manufacturing method is executed by the drawing and ironing process, the reshaping process for reshaping, and the necking process. A mouth portion forming step may be performed in which the opening portion of is processed to form a threaded portion and a curled portion. That is, the can manufacturing method of the present invention can be applied not only to two-piece cans but also to bottle cans.

In the above-described embodiment, in the drawing and ironing process, the primary can body 200 having the bottom portion 21 integrally connected to one end of the cylindrical body portion 22 is formed. Alternatively, the primary can body may be formed by forming the can bottom portion after the drawing and ironing step without forming the can bottom portion in the drawing and ironing step. That is, the primary can body forming process may consist of two processes, the drawing and ironing process and the can bottom forming process.

Various dimensions of the can of the above-described embodiment have been exemplified, but they are only examples. By pressing from the inside to bend the arc-shaped portion and expand the upper portion of the inner wall portion radially outward, the inner wall portion can be inclined toward the opposite side of the can axis to form an inclined wall portion. The present invention can be applied to cans.

In the above embodiment, the inner wall portion is formed in the primary can body forming step. , and the radially outer edge of this arc may be connected. That is, cans without inner walls and sloped walls are also within the scope of the present invention.

By punching and drawing an aluminum alloy plate material, a relatively large diameter shallow cup is formed, and this cup is again drawn and ironed (DI processing) to produce the above-mentioned aluminum alloy primary can body. 38 were manufactured. The average values of the various dimensions of the can bottom portions of the 38 primary can bodies are as follows: the curvature radius R11 of the dome portion is 29.0 mm; The distance W11 to C is 23.97 mm, the radius of curvature R13 of the inner arcuate portion is 1.35 mm, the radius of curvature R14 of the outer arcuate portion is 2.35 mm, the radius of curvature R15 of the bottom of the outer circumference is 1.7 mm, the inner arc The inner diameter W12 between the most radially inwardly positioned portions of the arc-shaped portion is 22.25 mm, the inner diameter W13 between the most radially outwardly positioned portions of the circular arc portion is 22.25 mm, and the outer diameter W14 of the cylindrical body portion is 22.25 mm. was 32.9 mm. A remolding process was performed on this primary can body by the method described in the above embodiment. At this time, the downward pressing amount of the punch was changed to 1.0 mm, 1.5 mm, 2.0 mm, 2.5 mm, and 3.0 mm, respectively, and the can height, bottom depth, maximum pressure resistance (pressure resistance strength) ) and the amount of growth were confirmed. The resin punch used at this time had a diameter L1 of 50 mm, an inner diameter L2 of the recessed portion of 41 mm, and a width L3 of the pressing surface of 4.5 mm, as shown in FIG. The width L4 in the radial direction of the portion arranged on the side was set to 2.25 mm.

(Method of measuring maximum withstand voltage)
The maximum pressure resistance (pressure resistance) was measured for each two samples. Specifically, each sample was fixed to a pneumatic buckling tester (manufactured by Universal Can Manufacturing Co., Ltd.) at a position 100 mm from the ground, and the pressure inside the can was increased by air pressure at a pressure increase speed of 98 kPa/s. , the maximum pressure until the dome part inverts (buckling) is measured, and the average value (ave), maximum value (max), and minimum value (min) are obtained, and the results are shown in Table 1 and FIG. 10. In FIG. 10, the horizontal axis indicates the pushing amount (mm), and the vertical axis indicates the average value of the maximum pressure resistance (kPa).

(Method for measuring growth amount at 686 KPa)
Two pieces of each sample were measured for the amount of growth. Specifically, for each sample, the top opening of the can body was airtightly sealed with the can bottom facing upward, and compressed air or the like was supplied to the inside to increase the internal pressure to 686 kPa. The bottom growth amount (projection deformation amount) at the tip of the circumferential ground contact portion is measured by two displacement meters (manufactured by Universal Can Manufacturing Co., Ltd.), and the average value (ave), maximum value (max), and minimum value (min) were obtained, and the results are shown in Table 2 and FIG. In FIG. 11, the horizontal axis indicates the pressing amount (mm), and the vertical axis indicates the average value of the growth amount (mm) at 686 KPa.

As shown in Table 1 and FIG. 10, the average pressure resistance (maximum pressure resistance) was the highest, 917.47 kPa, when the pushing amount was set to 2.0 mm. In addition, while the average value of the maximum pressure resistance of the primary can body is 790.80 kPa, all of the remolded products with a pushing amount of 1.0 mm or more and 3.0 mm or less became higher than the maximum pressure resistance of the primary can body. . Therefore, it was found that the compressive strength can be increased by performing the re-molding process.
In addition, as shown in Table 2 and FIG. 11, it was found that the growth amount at 686 KPa decreased as the pressing amount increased. In addition, while the average value of the growth amount at 686 KPa of the primary can body is 1.575 mm, all of the remolded products with a pushing amount of 1.0 mm or more and 3.0 mm or less have the growth at 686 KPa of the primary can body. less than the quantity.
From the above, it was considered that the pushing amount of the punch should preferably be 1.0 mm or more and 3.0 mm or less. Also, from the experimental results, it was thought that 2.0 mm ± 0.5 mm was preferable for this amount of pushing, but the effect on other processes during actual production (conveyance, can holding and inspection by an inspection machine) 1.0 mm or more and 2.0 mm or less is more preferable.

DESCRIPTION OF SYMBOLS 100... Can body 11... Can bottom part 111... Dome part 112... Upper bent part 113, 113A, 113B... Inclined wall part 114... Circumferential contact part 114A... Vertex 115... Lower bent part 116... Outer curved part 117... Peripheral bottom part REFERENCE SIGNS LIST 118: Press mark 12: Cylindrical body 200: Primary can body 21: Can bottom 211: Dome portion 211A: Peripheral edge 212: Arc-shaped portion 213: Inner wall portion 214: Protruding portion 214A: Vertex 215: Inner arc-shaped Part 216... Outer arcuate part 217... Outer peripheral bottom part 22... Cylindrical body part 30... Punch 31... Main body part 32... Recessed part 33... Annular projecting part 331... Pressing surface 40... Receptacle 41... Support plane

Claims (7)

a cylindrical body, a can bottom integrally connected to one end of the cylindrical body, a protruding part annularly projecting outward in the axial direction of the can from the can bottom; A primary can forming a primary can body having a dome portion formed on the can axis of the bottom portion and recessed inward in the can axis direction, and a concave arcuate portion continuing to the outer peripheral edge of the dome portion. a body formation process;
a reshaping step of reshaping the can bottom portion of the primary can body;
In the reshaping step, the peripheral portion of the dome portion is pressed from the inside of the cylindrical body portion while the tip of the projecting portion is supported by a support plane orthogonal to the can axis, thereby forming the arc portion. A method of manufacturing a can characterized by bending to form an upper bent portion with a small radius of curvature. In the primary can body forming step, an inner wall portion extending upward from a radially inner edge of the projecting portion is formed, and the arc-shaped portion is shaped to connect the outer peripheral edge of the dome portion and the upper end of the inner wall portion. ,
In the reshaping step, the peripheral portion of the dome portion is pressed from the inside of the cylindrical body portion, and the inner wall portion is expanded by expanding the upper portion of the inner wall portion radially outward while bending the arc-shaped portion. 2. The method of manufacturing a can according to claim 1, wherein the sloped wall portion is formed by slanting the . In the reshaping step, a punch for pressing the peripheral edge of the dome portion is formed with a pressing surface having a width extending from the peripheral edge of the dome portion to above the arc-shaped portion, and the pressing surface is used to press the dome portion. When pressing the peripheral edge of the arcuate portion, the arcuate portion is bent by pressing so that the pressing position on the arcuate portion sequentially transitions outward in the radial direction from the connection end with the dome portion. The manufacturing method of the can according to claim 2. In the primary can body forming step, an outer peripheral bottom portion connecting the radially outer edge of the projecting portion and the lower end of the cylindrical body portion is formed on the can bottom portion,
The projecting portion is composed of an inner arcuate portion located radially inward of the primary can body and an outer arcuate portion located radially outward from the apex thereof,
In the reshaping step, the inner arcuate portion is bent while the vicinity of the vertex of the inner arcuate portion is pressed against the support plane to form a lower bent portion with a small curvature radius that is continuous with the lower end of the inclined wall portion. 4. The method of manufacturing a can according to claim 3, wherein the outer arcuate portion is deformed so as to increase the radius of curvature of the outer arcuate portion to form the outer curved portion continuous with the lower curved portion. . 5. The method of manufacturing a can according to claim 3, wherein the reshaping step is performed using the punch disposed within the cylindrical body and a pedestal having the support plane. The outer diameter of the cylindrical body portion of the primary can body is 66.1 mm or more and 66.3 mm or less, and the angle of the tangential line on the inner surface of the outer peripheral edge of the dome portion with respect to the plane perpendicular to the can axis is 27° or more and 29°. °, the radial width of the portion of the pressing surface disposed radially inward of the primary can body from the inner wall portion is 2.0 mm or more and 3.0 mm or less, and the inclination of the pressing surface with respect to the plane 6. The method of manufacturing a can according to claim 5, wherein the angle is not less than 20[deg.] and not more than the angle of said tangent line with respect to said plane. 7. The method of manufacturing a can according to claim 6, wherein in the reshaping step, the pressing surface is pressed against the peripheral portion of the dome portion and pushed in by 1.0 mm or more and 3.0 mm or less.

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