JP7060349B2 - How to make a bottle can - Google Patents

Description

The present invention relates to a method for manufacturing a bottle can in which a metal cap is attached to an opening and a content such as a beverage is filled.

As a container filled with contents such as beverages, a container in which a metal cap is attached to the opening of a bottle-shaped can (bottle can) and sealed is known. A bottle can is generally formed in a bottomed cylindrical shape having a body (wall) and a bottom (bottom), and has a shoulder and a diameter-reduced portion that gradually shrinks in diameter toward the opening side of the body (bottom). A neck portion) is provided, and a mouth portion is provided at the upper end of the reduced diameter portion. Such a bottle can has a bottomed cylindrical shape having a body and a bottom by subjecting a metal plate (aluminum alloy plate) to a cupping step (squeezing step) and a DI step (squeezing and ironing). The shoulder portion and the diameter-reduced portion are formed by subjecting the body of the bottomed cylindrical can to the diameter-reducing process.

As a diameter reduction process for forming a reduced diameter portion, for example, as described in Patent Document 1 or Patent Document 2, a reduced diameter portion is formed by sequentially deforming the body portion of a can using a plurality of molding dies. A molding method has been proposed in which a smooth shape (smooth neck) having a tapered surface is formed without forming a stepped shape. In these diameter reduction processes, a relative movement along the axial direction of the can is generated between the bottomed cylindrical can and each molding die, and the molding surface of each molding die is repeatedly applied to the outer surface of the body of the can. By pressing against the body, the opening side of the body is gradually reduced in diameter to form the reduced diameter part.

Japanese Unexamined Patent Publication No. 7-185707 Special Table No. 3-502551 Gazette

In this type of bottle can, if an attempt is made to form a reduced diameter portion above the shoulder portion, which is the starting position of the reduced diameter, in a wide region (a long region along the can axis direction), the number of times of molding in this reduced diameter portion is large. There is a possibility that the previously formed shoulder may be deformed due to such reasons. In particular, when the shoulder portion is formed into a curved surface that is convex from the body to the outside and a curved surface that is concave is continuously formed between the shoulder portion and the reduced diameter portion, the can shaft received by processing the reduced diameter portion. Due to the load in the direction, the vicinity of the connection point between the concave curved surface and the convex curved surface rises, causing the inconvenience of not forming a smooth curved surface. When an attempt is made to form a reduced diameter portion in a wide region (a long region along the can axis direction), the number of moldings increases by the amount of the increased region, so that the phenomenon that the connection point between the concave curved surface and the convex curved surface rises becomes remarkable.

The present invention has been made in view of such circumstances, and provides a method for manufacturing a bottle can capable of finishing the outer surface from the shoulder portion to the reduced diameter portion into a smoothly continuous rounded outer surface. The purpose is to do.

In the method for manufacturing a bottle can of the present invention, the annular molding surface of the mold is pressed against the open end of the bottomed cylindrical cylinder and moved relative to the can axis, so that the upper end of the cylindrical body has a radius. A shoulder portion having a curved convex surface that is reduced inward in the direction and convex outward, and a curved portion having a curved concave surface that is concave when viewed from the outside by reducing the diameter of the upper end of the shoulder portion, and the variation. It is a method of manufacturing a bottle can having a reduced diameter portion that is gradually reduced in diameter toward the opening end above the curved portion, and processing of the curved portion from the shoulder portion is performed by a preforming step and a reforming step. It has a reduced diameter portion forming step for forming the reduced diameter portion between the preforming step and the reforming step, and in the preforming step , the curved convex surface is formed at the upper end of the body portion. A convex surface portion that is convex outward with a small radius of curvature and a conical tapered surface portion that is continuous at the upper end of the convex surface portion are formed, and in the reforming step, the region from the convex surface portion to the tapered surface portion is remolded. To form the curved convex surface .

As described above, since the curved convex surface of the shoulder portion and the curved concave surface of the inflection portion have a continuous shape, if the shoulder portion and the inflection portion are formed before the diameter reduction portion is formed, the diameter reduction portion forming step is performed. Occasionally, when pressed in the can axis direction, a phenomenon occurs in which the vicinity of the connection point between the curved convex surface of the shoulder portion and the curved concave surface of the inflection portion protrudes outward. In the present invention, the shoulder portion is divided into a preforming step and a reforming step. First, a reduced diameter portion is formed after preforming, and then a reforming step is performed to form the shoulder portion and the curved portion. Therefore, it is possible to suppress the phenomenon that the vicinity of the connection point between the shoulder portion and the curved portion protrudes. Then, the curved convex surface and the curved concave surface are smoothly continuous, and the outer shape can be rounded from the shoulder portion to the inflection portion.

In the preforming step, since the convex surface portion and the curved concave portion are formed in a shape separated by the conical tapered surface portion, when the axial load in the diameter reduction portion forming step is transmitted to the curved concave portion, The phenomenon that the lower end of the curved concave portion tends to protrude outward can be reliably suppressed by the tapered surface portion as a resistance. Then, in the reforming step after the diameter-reduced portion forming step, the radius of curvature of the convex portion is increased to form the curved convex portion, and at the same time, the tapered surface portion is formed to be smaller to smooth the curved convex surface and the curved concave surface. It can be finished in a continuous rounded shape. Since the reduced diameter portion is formed before the remodeling step, the shape of the curved portion is not deformed from the shoulder portion after the remodeling step.

As a preferred embodiment of the method for manufacturing a bottle can of the present invention, the radius of curvature of the outer surface of the convex surface portion is 5 mm or more and 18 mm or less, and the inclination angle of the tapered surface with respect to the can axis is 20 ° or more and 50 ° or less. The radius of curvature of the outer surface of the curved convex surface is preferably 12 mm or more and 30 mm or less.

According to the present invention, it is possible to finish the outer surface from the shoulder portion to the reduced diameter portion to have a smoothly continuous rounded outer surface.

It is a front view which made the right half of the container which used the bottle can manufactured by the manufacturing method of the bottle can which concerns on embodiment of this invention a cross section through a can shaft. Among the methods for manufacturing a bottle can according to the embodiment of the present invention, it is a schematic view showing the steps from forming a cup to forming a cylinder in order, and the right half is a front view having a vertical cross section passing through a can shaft. Is. Of the steps after FIG. 2, it is a schematic view explaining the step of forming the shoulder portion, the curved portion, and the reduced diameter portion, and the right half is a front view having a vertical cross section passing through the can shaft. FIG. 3 is an enlarged cross-sectional view of a main part of the intermediate molded body in the preforming step shown in FIG. 3A. FIG. 3B is an enlarged cross-sectional view of a main part of the intermediate molded body in the diameter reduction step shown in FIG. 3 (b). FIG. 3 is an enlarged cross-sectional view of a main part of the intermediate molded product after the reforming step shown in FIG. 3 (c). FIG. 3 is a schematic view showing the steps after FIG. 3 in order, and the right half is a front view having a vertical cross section passing through a can shaft. It is a side view of the bottle can manufacturing apparatus. It is sectional drawing which follows the AA line of FIG. It is sectional drawing which passes through the can shaft explaining the relationship between the necking die, the cylinder body and the intermediate molded body in the pre-molding process shown in FIG. 3 (a). A modification of the reforming process is described, and as in FIG. 6, it is an enlarged cross-sectional view of a main part of the intermediate molded body after the reforming process.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
(First Embodiment)
FIG. 1 is a front view of a container 301 including a bottle can 101 manufactured in the can manufacturing method according to the first embodiment of the present invention and a cap 201 attached to an open end portion 10a of the bottle can 101. It is a semi-cross-sectional view showing a cross section with the right half passing through the can shaft C. 2 to 7 are explanatory views showing each step of the manufacturing method of the bottle can 101 of the embodiment and enlarged cross-sectional views of the main parts. Of these, FIG. 2 shows the process of forming the cup 40 to form the tubular body 41, FIG. 3 shows the process of forming the shoulder portion, the curved portion, and the reduced diameter portion, and FIG. 7 shows the mouth above the reduced diameter portion. The steps from forming the portions to manufacturing the bottle can 101 are shown in order. 4 to 6 show cross sections of a main part of the intermediate molded body 42 molded in each step of FIG.

The bottle can 101 is made of a thin plate metal such as aluminum or an aluminum alloy, and has a bottomed cylindrical shape having a cylindrical body portion (wall) 10 and a dome-shaped bottom portion (bottom) 20 as shown in FIG. Is formed in.
As shown in FIG. 1, the body portion 10 and the bottom portion 20 are arranged coaxially with each other, and in the present embodiment, these common axes will be referred to as a can axis C and will be described. Further, among the directions along the can axis C (direction of the can axis C), the direction from the open end 10a of the body portion 10 toward the bottom 20 side is downward, and the direction from the bottom 20 toward the open end 10a is upward. In the following description, the vertical direction shall be determined in the same manner as the direction shown in FIG. Further, the direction orthogonal to the can axis C is referred to as a radial direction, and among the radial directions, the direction approaching the can axis C is the inner side (inward) of the radial direction, and the direction away from the can axis C is the outer direction in the radial direction (the direction away from the can axis C). Outside). Further, the direction of orbiting around the can axis C is defined as the circumferential direction.

As shown in FIGS. 1 and 6, the body portion 10 has a body portion 10 formed in a cylindrical shape on the bottom portion 20 side, and the body portion 10 is reduced in diameter so as to bend inward in the radial direction at the upper end of the body portion 10 to the outside. A shoulder portion 12 having a curved convex surface 12a that is convex in the direction, a bending portion 13 having a curved concave surface 13a that is reduced in diameter so as to bend back at the upper end of the shoulder portion 12 and is concave inward, and a bending portion 13. It is provided with a diameter-reduced portion 14 whose diameter is gradually reduced toward the upper side (opening end portion 10a side) in the can axis C direction at the upper end, and a mouth portion 15 formed at the upper end of the diameter-reduced portion 14. As shown in FIG. 1, assuming that the angle (tilt angle) formed by the reduced diameter portion 14 and the can shaft C of the body portion 10 is α, the tilt angle α is provided to be, for example, 6 ° or more and 24 ° or less, and is reduced. The diameter portion 14 is formed in a shape standing in the can axis C direction. The body portion 10, the shoulder portion 12, the curved portion 13, and the diameter-reduced portion 14 each form an annular shape extending over the entire circumference of the body portion 10 in the circumferential direction.

Further, the body portion 11, the shoulder portion 12, the curved portion 13, and the reduced diameter portion 14 are smoothly connected to each other, and are smoothly connected to each other without forming a step. Specifically, in the vertical cross section shown in FIG. 1 and the vertical cross section of the main part shown in FIG. 6, the outer surface of the curved convex surface 12a of the shoulder portion 12 faces the outside (diametrical outside) and the upper side of the body portion 10. It is formed in a convex curved surface shape that is convex outward, and the lower end of the curved convex surface 12a of the shoulder portion 12 and the upper end of the body portion 10 are provided in smooth contact with each other. It is a tangent to the curved convex surface 12a of the portion 12, and is provided in a straight line downward. The outer surface of the curved concave surface 13a of the inflection portion 13 is formed in a concave curved surface shape that is concave inward toward the inside (inside in the radial direction) and downward of the body portion 10. The lower end of the curved concave surface 13a and the upper end of the curved convex surface 12a of the shoulder portion 12 are smoothly contacted with each other via a slight tapered surface 52, and the upper end of the curved convex surface 12a of the shoulder portion 12 and the curved concave surface 13a of the inflection portion 13 are provided. Is connected to the lower end of the tape so that the tapered surface 52 is a common tangent. Further, the upper end of the curved concave surface 13a of the inflection portion 13 and the lower end of the reduced diameter portion 14 are provided so as to be in smooth contact with each other, and the reduced diameter portion 14 becomes a tangent to the curved concave surface 13a of the inflection portion 13 at the connection point. There is.
The radius of curvature R1 of the curved convex surface 12a of the shoulder portion 12 (radius of curvature on the outer surface of the shoulder portion 12) is 12 mm to 30 mm, and the radius of curvature R2 of the curved concave surface 13a of the curved portion 13 (radius of curvature on the outer surface of the curved portion 13). Is 10 mm to 24 mm.

Further, the mouth portion 15 arranged at the upper portion of the body portion 10 includes a large diameter portion 31 whose diameter is once expanded at the upper end of the reduced diameter portion 14 and a small diameter portion 32 whose diameter is reduced again at the upper end of the large diameter portion 31. It has a curl portion 33 formed at the open end portion 10a at the upper end of the small diameter portion 32. As described above, the mouth portion 15 is opened to the outside by the opening end portion 10a, and the contents such as beverages are filled inside the bottle can 101 through the mouth portion 15. Further, as shown in FIG. 1, by attaching the cap 201 to the mouth portion 15, the contents filled in the inside of the bottle can 101 are sealed.

The bottom portion 20 of the bottle can 101 is located on the can shaft C, and has a dome portion 21 formed so as to bulge upward (inside the body portion 10) and an outer peripheral edge of the dome portion 21. A heel portion 22 for connecting the portion and the lower end portion of the body portion 10 is provided. Further, the connecting portion between the dome portion 21 and the heel portion 22 has a mounting surface such that the bottle can 101 is in an upright posture (a posture in which the open end portion 10a of the body portion 10 faces upward as shown in FIG. 1). It is a grounding portion 23 that comes into contact with the mounting surface when it is mounted on the top. The ground contact portion 23 projects downward at the bottom portion 20 and forms an annular shape extending along the circumferential direction.

To give an example of other dimensions of the bottle can 101 having such a shape, the original plate thickness of the bottle can 101 before molding is 0.250 mm to 0.500 mm. Further, in the vertical cross-sectional view of the bottle can 101 shown in FIG. 1 through the can shaft C, the outer diameter Db of the body portion 10 to be a product is 52 mm to 68 mm. The outer diameter Ds1 (contact point between the reduced diameter portion 14 and the curved portion 13) at the lower end of the reduced diameter portion 14 is, for example, within the range of 30 mm to 45 mm. However, the above dimensions are not limited to the above numerical range.

In the case of the bottle can 101 of the first embodiment shown in FIG. 1, the outer diameter Db of the body portion 11 is 66 mm, the radius of curvature R11 of the curved convex surface of the shoulder portion 12 is 20 mm, and the radius of curvature R21 of the curved concave surface of the inflection portion 13. Is 12 mm, and the inclination angle α of the reduced diameter portion 14 is 10 °.

As described above, in order to manufacture the bottle can 101 having the reduced diameter portion 14, first, an aluminum plate material such as an aluminum alloy is punched out and drawn to have a relatively large diameter as shown in FIG. 2A. After forming the shallow cup 40, the cup 40 is subjected to drawing and ironing (DI processing) again to form a bottomed cylindrical cylinder 41 having a predetermined height as shown in FIG. 2 (b). And trim the top edge. By this DI processing, the bottom portion of the tubular body 41 is formed into the shape of the bottom portion 20 as the final bottle can 101.

Then, for example, the bottle can 101 is manufactured by the bottle can manufacturing apparatus 501 shown in FIGS. 8 and 9. The bottle can manufacturing apparatus 501 will be described below. The bottle can manufacturing apparatus 501 is for processing the cylindrical body 41 formed as described above into a bottle can 101 having a final shape, and the shape of the can changes according to the progress of processing. However, in the following, when the shape of the bottomed cylindrical can is not particularly limited between the tubular body 41 and the bottle can 101, the intermediate molded body 42 will be described. Further, in the following, the body portion and the bottom portion of the intermediate molded body 42 will be described using the same reference numerals as the body portion 10 and the bottom portion 20 of the bottle can 101.

The bottle can manufacturing apparatus 501 includes a work holding portion 511 that holds a plurality of intermediate molded bodies 42 in a horizontal arrangement in the can axis C direction, and a plurality of molding tools that perform various molding processes on the intermediate molded bodies 42. It includes a tool holding unit 513 that holds 512, and a driving unit 514 that drives both holding units 511 and 513. The work holding side of the work holding portion 511 that holds the intermediate molded body 42 and the tool holding side of the tool holding portion 513 that holds the forming tool 512 are arranged so as to face each other.

The work holding portion 511 has a configuration in which a plurality of holding devices 517 for holding the intermediate molded body 42 are arranged in an annular shape along the circumferential direction on the surface of the disk 516 supported by the support shaft 515 facing the tool holding portion 513. Has been done. The disk 516 is intermittently rotated around the support shaft 515 by the drive unit 514, so that the bottom portion of the intermediate molded body 42 supplied from the supply unit 518 via the supply side star wheel 519 is set to the holding device 517 by 1. Each piece is held and conveyed in the circumferential direction of the disk 516. The intermediate molded body 42 is molded by each molding tool 512 of the tool holding portion 513 during transportation by the disk 516, and then sequentially discharged to the discharge unit 611 as a molded bottle can 101 via the discharge side star wheel 601. ..

In the tool holding portion 513, a plurality of various molding tools 512 are arranged in an annular shape along the circumferential direction on the surface of the disk 613 supported by the support shaft 612 facing the work holding portion 511, and the disk 613 is supported by the drive unit 514. It is configured to move forward and backward in the axial direction of the shaft 612. The support shaft 612 is provided coaxially with the support shaft 515 inside the support shaft 515.

The tool holding portion 513 includes a plurality of diameter reduction dies for reducing the diameter (neck-in processing) of the opening of the intermediate molded body 42, a curl portion forming tool for forming the curl portion 33, and the like. , A plurality of molding tools 512 for performing machining according to each machining step are provided. These molding tools 512 are arranged in an annular shape on the disk 613 in the order of processes so as to be arranged in the circumferential direction.

The intermittent rotation stop position of the work holding portion 511 (disk 516) centered on the axis of the support shaft 515 is such that the can shaft C of each intermediate molded body 42 with the opening facing the tool holding portion 513 is molded. It is set to match the central axis of the tool 512. Then, by the intermittent rotation of the disk 516 by the drive unit 514, each intermediate molded body 42 is rotationally moved to a position facing each molding tool 512 for the next process, and the next step of processing is performed.

That is, when the tool holding portion 513 advances and the work holding portion 511 and the tool holding portion 513 approach each other, each molding tool 512 performs processing according to each process on the intermediate molded body 42, and both holding portions 511. , 513 are separated from each other, and the work holding portion 511 is rotationally moved so that the molding tool 512 of the next step faces each intermediate molded body 42. In this way, the two holding portions 511, 513 are processed in close proximity to each other, and the operations of separating and rotating are repeated, so that the intermediate molded body 42 has a shoulder portion 12, a curved portion 13, a diameter-reduced portion 14, and a mouth. The portions 15 are sequentially formed to form the bottle can 101.

Next, the method of manufacturing the bottle can 101 using the bottle can manufacturing apparatus 501 will be described in detail in the order of processes.
A plurality of forming tools arranged in the circumferential direction of the tool holding portion 513 with respect to the upper end portion of the tubular body 41 formed to the state shown in FIG. 2 (b) by drawing and ironing (DI forming) a thin plate such as an aluminum alloy. By sequentially using the 512 and moving the molding tool 512 along the can axis C direction to perform a die-necking process, the tubular body 41 is sequentially shown in FIGS. 3 (a) to 3 (c). The diameter of the upper portion is reduced from the middle position in the height direction of the shoulder portion 12, the curved portion 13, and the upper portion of the curved portion 13 is gradually reduced in diameter to form the reduced diameter portion 14. Next, a slightly larger diameter portion 31 is formed on the reduced diameter portion 14, and then the diameter is reduced again to form a tapered small diameter portion 32 that gradually shrinks in the upward direction. A tubular small-diameter tubular portion 34 extending above the small-diameter portion 32 is formed (FIG. 7A). Finally, the small-diameter cylinder portion 34 is curled to form the curl portion 33, and as shown in FIG. 7 (b), the bottle can 101 having the mouth portion 15 is manufactured.

Of these, the molding of the region from the shoulder portion 12 to the curved portion 13 is performed separately in the preforming step and the reforming step, and after the preforming step, a reduced diameter portion forming step for forming the reduced diameter portion 14 is performed. After that, the reform process is performed.
As shown in FIGS. 3A and 4, the preforming step extends from the convex surface portion 51 which is convex outward so as to bend the upper end of the body portion 10 inward in the radial direction, and the upper end of the convex surface portion 51. A conical tapered surface portion 52, a concave surface portion 53 that is concave when viewed from the outside so as to bend back from the upper end of the tapered surface portion 52, and a cylindrical tubular portion 54 extending from the upper end of the concave surface portion 53 along the can axis direction. And are continuously formed.
In this case, the radius of curvature R11 of the outer surface of the convex surface portion 51 is set to be smaller than the radius of curvature R1 of the curved convex surface 12a of the shoulder portion 12, for example, 5 mm or more and 18 mm or less. Further, the tapered surface portion 52 is formed so that the angle β formed with the can shaft C is set to 20 ° or more and 50 ° or less and extends in the tangential direction of the upper end of the convex surface portion 51. It is appropriate that the length L of the tapered surface portion 52 is 5 mm or more and 20 mm or less. The concave surface portion 53 is connected so that the radius of curvature R21 of the outer surface thereof is set to 10 mm or more and 24 mm or less, and the lower end of the concave surface portion 53 and the tapered surface portion 52 are arranged so that the tapered surface portion 52 is arranged in the tangential direction of the concave surface portion 53. The radius. The tubular portion 54 has a straight cylindrical shape along the tangential direction of the upper end of the concave surface portion 53.

In this preforming step, as shown in FIG. 10, a die-necking die including an outer die 61 having an annular forming surface 64 and an inner die 62 arranged inside the outer die 61 is used. The outer diameter of the inner die 62 is smaller than the inner diameter of the open end of the tubular body 41 before machining, and is formed at the inner diameter after the diameter reduction. The inner peripheral surface of the outer die 61 is the open end of the tubular body 41 before machining. Insert the opening end of the cylinder 41 whose diameter has been reduced between the guide surface 63 having an inner diameter that accepts the guide surface 63, the tapered molding surface 64 for drawing to reduce the diameter of the opening, and the outer peripheral surface of the inner die 62. The small diameter surface 65 forming the gap is sequentially formed from the tip. Then, while guiding the open end of the tubular body 41 along the guide surface 63 of the outer die 61, the diameter is reduced to follow the molding surface 64 by pressing against the molding surface 64, and the opening end is reduced. It is inserted between the outer peripheral surface 62a of the inner die 62 and the small diameter surface 65 of the outer die 61 and reduced in diameter.
Since the diameter reduction ratio from the cylinder 41 to the small diameter portion is large, a plurality of sets of dies consisting of a combination of the inner die 62 and the outer die 61 are used, and the space between them is formed in a plurality of times. The figure shows the processing in the first stage, and the intermediate molded body 42 (preformed can) having the above-mentioned shape is formed by the processing a plurality of times.

Next, in the reduced diameter portion forming step, the diameter of the tubular portion 54 from the concave surface portion 53 formed in the preforming step to the opening end gradually decreases from the upper end of the concave surface portion 53 toward the opening end. A cylindrical portion 16 having a small diameter is formed from the upper end of the reduced diameter portion 14 to the opening end side of the portion 14.
In this diameter reduction portion forming step, a die-necking die having an outer die and an inner die similar to that in FIG. 10 is used, and although not shown in particular, a wide region (in the can axis C direction) above the upper end of the concave portion 53 is used. In order to form the reduced diameter portion 14 in a long region along the line), a plurality of dinecking dies having annular forming surfaces having different processing diameters are fitted in order from the side having the largest processing diameter to perform multiple diameter reduction processing. To give.

Next, in the reforming step, the region from the convex surface portion 51 formed in the preforming step to the concave surface portion 53 via the tapered surface portion 52 is remolded, and the curved convex surface 12a and the curved concave surface 13a are slightly tapered. The shoulder portion 12 and the curved portion 13 which are smoothly continuous through the shoulder portion 12 are formed. This processing is also processing by a necking die including an outer die having an annular forming surface and an inner die similar to those in FIG. 7, and the outer die 61 is formed into a premolding portion 55 (convex surface portion 51, tapered surface portion 52, concave surface portion). This is done by approaching 53) and pressing the outer surface of the premolded portion 55 with the molding surface 64. As shown by the alternate long and short dash line in FIG. 5, the forming surface 64 of the outer die 61 has a continuous shape of the concave forming surface 64a forming the curved convex surface 12a and the convex forming surface 64b forming the curved concave surface 13a. The concave surface portion 53 of the premolded portion 55 is pressed in the can axis direction by the convex molded surface 64b, and the tapered surface portion 52 is remolded from the convex surface portion 51 of the premolded portion 55 by the concave molded surface 64a of the outer die 61. As a result, a curved concave surface 13a is formed from the curved convex surface 12a of the shoulder portion 12 from the preformed portion 55 shown by the two-dot chain line in FIG. 6, as shown by the solid line. The tapered surface portion 52 formed by the preforming portion 55 has its region reduced to, for example, by half or less by this reforming step, and smoothly connects between the curved convex surface 12a and the curved concave surface 13a. In this case, the curved concave surface 13a is substantially the same as the radius of curvature of the concave surface portion 53 formed in the preforming step.

Next, if necessary, a reduced diameter portion remolding step is performed so as to reshape the surface of the reduced diameter portion 14. In this reduced diameter portion remolding step, since most of the outer shape of the reduced diameter portion 14 is formed in the previous reduced diameter portion forming step, a slight step is formed on the surface of the reduced diameter portion 14 during the plurality of machining at that time. When a portion is formed, the surface is lightly pressed to finish the reduced diameter portion 14 to a smooth surface.
Then, as shown in FIG. 7A, the large diameter portion 31, the small diameter portion 32, and the small diameter cylinder portion 34 are sequentially formed on the reduced diameter portion 14, and the small diameter cylinder portion 34 is curled to be curled. 33 is formed, and as shown in FIG. 7 (b), a bottle can 101 having a mouth portion 15 is manufactured.

In the bottle can 101 manufactured in this manner, the region from the shoulder portion 12 to the inflection portion 13 has a curved convex surface 12a having a relatively large radius of curvature and a tapered surface portion 52 having a slight curved concave surface 13a from the body portion 10. It is continuous through and finished in a smooth rounded shape.
Since the tapered surface portion 52 is formed between the convex surface portion 51 and the concave surface portion 53 in the reforming process, the taper is formed even when a load is applied in the can axis C direction in the subsequent diameter reduction portion forming process. The surface portion 52 serves as a resistance, and the phenomenon that the lower end of the concave surface portion 53 rises is suppressed.
Therefore, the curved convex surface 12a and the curved concave surface 13a are smoothly continuous, and the bottle can 101 having a rounded outer shape can be finished from the shoulder portion 12 to the inflection portion 13. In this case, a part of the tapered surface portion 52 formed in the preforming step is left in the reforming step, but the entire concave surface portion 53, the tapered surface portion 54, and the convex surface portion 51 formed in the preforming step are remolded in the reforming step. Then, as shown in FIG. 11, the curved concave surface 13a and the curved convex surface 12a may be directly connected to each other, and the tapered surface portion 52 may not be provided after the reforming step. In that case, the curved concave surface 13a may be formed so that the radius of curvature is larger than that of the concave surface portion 53 formed in the preforming step.

The present invention is not limited to the configuration of the above embodiment, and various changes can be made to the detailed configuration without departing from the spirit of the present invention.
For example, as a bottle can, a bottomed cylindrical cylinder 41 is formed in advance and an open end thereof is formed, but the cylinder includes a cylinder having no bottom, and after molding the curl portion, A separately formed bottom may be wrapped around the body.

10 Body 10a Open end 12 Shoulder 12a Curved convex surface 13 Curved part 13a Curved concave surface 14 Reduced diameter part 15 Mouth part 16 Cylindrical cylinder part 20 Bottom part 21 Dome part 22 Heel part 23 Grounding part 31 Large diameter part 32 Small diameter part 33 Curl part 34 Small diameter cylinder part 40 Cup 41 Cylinder body 42 Intermediate molded body 51 Convex surface part 52 Tapered surface part 53 Concave surface part 54 Cylinder part 55 Pre-molded part 61 Outer die 62 Inner die 62a Outer peripheral surface 63 Guide surface 64 Molded surface 64a Concave molding Surface 64b Convex molding surface 65 Small diameter surface 101 Bottle can 201 Cap 301 Container 501 Bottle can manufacturing equipment

Claims (2)

By pressing the annular molding surface of the mold against the open end of the bottomed cylindrical cylinder and moving it relative to the can axis, the upper end of the cylindrical body is reduced inward in the radial direction and outward. A shoulder portion having a curved convex surface that is convex, a curved portion having a curved concave surface that is concave when viewed from the outside by reducing the diameter of the upper end of the shoulder portion, and an opening portion above the curved portion. Therefore, it is a method of manufacturing a bottle can having a gradually reduced diameter portion, and the processing of the curved portion from the shoulder portion is performed separately in a preforming step and a reforming step, and the preforming step and the reforming step are performed. It has a reduced diameter portion forming step for forming the reduced diameter portion between the steps.
In the preforming step, a convex surface portion that is convex outward with a radius of curvature smaller than the curved convex surface at the upper end of the body portion and a conical tapered surface portion that is continuous at the upper end of the convex surface portion are formed, and the reforming is performed. In the step, a method for manufacturing a bottle can, characterized in that a region from the convex surface portion to the tapered surface portion is remolded to form the curved convex surface . The radius of curvature of the outer surface of the convex surface portion is 5 mm or more and 18 mm or less, the inclination angle of the tapered surface with respect to the can axis is 20 ° or more and 50 ° or less, and the radius of curvature of the outer surface of the curved convex surface is 12 mm or more and 30 mm or less. The method for manufacturing a bottle can according to claim 1 , wherein the method is characterized by the above.

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