Metal can manufacturing method and metal can

Abstract

To provide a metal can manufacturing method capable of forming a prescribed uneven shape in a trunk while ensuring load bearing during manufacturing and shock resistance after content filling for machining of a linear groove, and a metal can.SOLUTION: This metal can manufacturing method comprises: a cylinder formation process of forming a bottomed cylinder; a necking process of forming an opening having an opening diameter smaller than the inner diameter of the trunk by executing necking machining above the trunk of the bottomed cylinder; and a groove machining process of executing groove machining over the entire periphery of the trunk using an outer roll and an inner roll after the necking process. The groove machining process includes a step of holding the trunk between the outer roll and the inner roll, pushing the trunk in the inner diameter direction through rotation of the outer roll and the inner roll in synchronization, and forming a linear groove in the trunk, a step of forming a contour in the trunk by the linear groove, and a step of forming a contour by overlapping the formation start position of the linear groove and the formation end position of the linear groove in the trunk.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a method for manufacturing a metal can and a metal can. [Background technology]

[0002] In recent years, metal cans have been manufactured with an uneven shape formed on the body of the can body. By forming an uneven shape on the body in this way, advantages such as improved impact resistance and axial load resistance strength of the can body, and increased visibility when the metal can is displayed as a product, have been achieved. In the manufacture of such metal cans, one method for forming an uneven shape on the body of a can body is, for example, to form an uneven shape on the body using an outer roll (external roll) arranged on the outside of the body and an inner roll (internal roll) arranged on the inside of the body (see Patent Documents 1 and 2). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 2705684 [Patent Document 2] Patent No. 4837593 Summary of the Invention [Problem to be solved by the invention]

[0004] While metal cans with the aforementioned textured body are expected to have improved impact resistance and axial load resistance, the textured shape is limited to a functional one. Furthermore, if linear grooves are used as the textured shape, the load resistance of the body of the can body becomes uneven in the circumferential direction, which can lead to the problem of the body being prone to buckling during the manufacturing process. On the other hand, if the body plate thickness is made relatively thick to ensure load resistance during manufacturing and external impact resistance after filling, material costs increase. Improvements to these issues are needed. [Means for solving the problem]

[0005] According to the present invention, there is provided a method for manufacturing metal cans, comprising: a cylinder forming step of forming a bottomed cylinder from a plate metal material; a necking step of necking the bottomed cylinder above the body portion to form an opening having a diameter smaller than the inside diameter of the body portion; and a groove processing step of processing grooves around the entire circumferential direction of the body portion using an outer roll and an inner roll after the necking step, wherein the groove processing step comprises: a step of sandwiching the body portion between the outer roll and the inner roll and rotating the outer roll and the inner roll synchronously to press the body portion in the inner diameter direction to form linear grooves in the body portion; a step of forming a contour in the body portion by the linear grooves; and a step of overlapping a position in the body portion where the linear groove formation start position and the linear groove formation end position are to be formed to form the contour.

[0006] The present invention also provides a metal can in which necking is performed above a body portion of a bottomed cylindrical body formed from a plate metal material, thereby forming an opening having an opening diameter smaller than the inside diameter of the body portion, and after the necking, groove processing is performed around the entire circumferential direction of the body portion using an outer roll and an inner roll, wherein the groove processing involves sandwiching the body portion between the outer roll and the inner roll, and rotating the outer roll and the inner roll synchronously to press the body portion in the inward radial direction, thereby forming linear grooves in the body portion, and between the linear grooves there is a curved portion that is convex in the outer radial direction, and the linear grooves form a contour in the body portion, and the contour is formed by overlapping the position in the body portion where the linear groove formation start position and the position in the body portion where the linear groove formation end position are formed, and there is no break at the joint of the contour. [Effects of the Invention]

[0007] According to the present invention, there is provided a method for manufacturing a metal can that, when processing linear grooves, allows for the formation of a predetermined uneven shape in the body portion while ensuring load-bearing capacity during manufacturing and resistance to external impact after filling with contents. Furthermore, according to the present invention, there is provided a metal can that has desired performance and a highly decorative appearance in the body portion. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a front view showing an example of a metal can according to an embodiment of the present invention. [Figure 2] FIG. 1 is a side view illustrating an example of a metal can according to an embodiment of the present invention. [Figure 3] FIG. 2 is a development view showing an example of the outer peripheral surface of the body of the metal can according to the present embodiment. [Figure 4] 1 is a flowchart illustrating an example of a method for manufacturing a metal can according to the present embodiment. [Figure 5] FIG. 2 is an explanatory view of a groove processing step, and is a schematic side view showing an outer roll, an inner roll, and a bottomed cylinder. [Figure 6] FIG. 2 is a partial schematic end view illustrating the positional relationship between the outer roll and the inner roll during groove processing. [Figure 7] 10 is an explanatory diagram for explaining an example of the relationship between the inner peripheral length of the body of the bottomed cylinder and the outer peripheral length of the unit portion of the inner roll. FIG. [Figure 8] 10 is an explanatory diagram for explaining another example of the relationship between the inner peripheral length of the body of the bottomed cylinder and the outer peripheral length of the unit portion of the inner roll. FIG. DETAILED DESCRIPTION OF THE INVENTION

[0009] Hereinafter, an embodiment of the present invention (the present embodiment) will be described with reference to the drawings. In the following description, the same reference numerals in different drawings indicate parts with the same function, and duplicated explanations in each drawing will be omitted as appropriate. The present embodiment illustrates an example of a manufacturing method for manufacturing metal cans and metal cans manufactured thereby.

[0010] [Metal can] The metal can 1 according to this embodiment shown in Fig. 1 is a beverage can for storing a beverage inside, and is formed by subjecting a bottomed cylindrical metal body to various processes. The metal can 1 has a flange 2, a neck 3 connected to the lower end of the flange 2, a body 4 connected to the lower end of the neck 3, and a bottom 5 connected to the lower end of the body 4. The metal can 1 also has an opening 6 formed at the location where the flange 2 is formed. The neck 3 gradually narrows in diameter toward its upper end. After a beverage is stored inside the metal can 1, a can lid (not shown) is fastened around the flange 2 to form a beverage can as a finished product.

[0011] In the description of this embodiment, the flange portion, neck portion, body portion, bottom portion, and opening portion of the bottomed cylindrical body will be described as a flange portion 2, a neck portion 3, a body portion 4, a bottom portion 5, and an opening portion 6, respectively, in the same manner as the metal can 1.

[0012] 1 and 2, an uneven groove design 7 is formed on the outer peripheral surface 41 of the body 4 of the metal can 1 over the entire circumferential direction. The groove design 7 is formed by groove processing performed on the body 4 of a bottomed cylindrical body 100 shown in FIGS. 5(a) and 5(b) using an outer roll 101 and an inner roll 102, and is a design in which contours 9 formed by linear grooves 8 that protrude in the inner diameter direction (inward in the radial direction) of the body 4 are connected. Note that in this body 4, between the linear grooves 8, there is a curved surface portion 11 that protrudes in the outer diameter direction (outward in the radial direction) of the body 4.

[0013] In the example described here, the groove machining design 7 has two consecutive unit parts a1 made up of constituent units equal to the outer peripheral length of the inner roll 102 (FIGS. 5(a) and (b)) in the circumferential direction of the body part 4. That is, the groove machining design 7 is composed of a unit part a1 in the range from machining position p1 to machining position p6, which will be described later in FIG. 3, and a unit part a1 in the range from machining position p6 to machining position p11.

[0014] The area of ​​one unit part a1 of the groove machining design 7 shown in Fig. 3 is an area covering half the circumference of the outer peripheral surface 41, which corresponds to an interior angle of 180° of the body part 4. The groove machining design 7 is formed by two of these unit parts a1 being continuously connected in the circumferential direction. In other words, the groove machining design 7, which is made up of two unit parts a1, is formed in an area covering the entire circumference of the outer peripheral surface 41, which corresponds to an interior angle of 360° of the body part 4 (i.e., over the entire circumference of the body part 4).

[0015] Alternatively, the groove machining design 7 may have three or more unit portions a1 arranged consecutively in the circumferential direction. Alternatively, the unit portions a1 may be formed by equally dividing the outer circumferential length of the inner roll 102.

[0016] The groove processing design 7 has a highly decorative uneven shape in its unit part a1, in which multiple contours 9 are continuously connected. For example, as shown in FIG. 3 , the unit part a1 has, as contours 9, vertically elongated elliptical contours 9a and 9b. In the example of FIG. 3 , contour 9a is longer in the circumferential direction than contour 9b, but the elliptical shapes of contours 9a and 9b and their vertical and circumferential sizes are not limited to those shown here. The groove processing design 7 shown in the example of FIG. 3 is composed of unit parts a1 having such continuous elliptical contours 9. The metal can 1 has a highly decorative uneven shape due to this groove processing design 7 over the entire circumferential direction of the body part 4.

[0017] In the groove machining design 7 shown in the example of Fig. 3, adjacent elliptical contours 9 are connected to each other so that their linear grooves 8 partially overlap. For example, as shown in Fig. 3, a contour 9a formed in the range from machining position p4 to machining position p5 (described later) and a contour 9a formed in the range from machining position p5 to machining position p7 are connected to each other so that their linear grooves 8 overlap at machining position p5.

[0018] The contour 9 is not limited to the elliptical example shown in Fig. 3. The linear groove 8 may be a straight line, a curved line, or a combination thereof, and the contour 9 of the unit part a1 may be a combination of any contour shapes. For example, at least one of the contours 9 shown in Fig. 3 may be changed to, for example, a contour shape consisting of other curves (such as a circle), various polygons, or a contour shape consisting of straight lines and various curves.

[0019] In the metal can 1, the groove processing design 7 consisting of the contour 9 (contours 9a, 9b) formed by the linear grooves 8 is formed over the entire circumferential direction of the body 4, thereby realizing a beverage can having a highly decorative uneven shape over the entire circumferential direction of the outer peripheral surface 41 of the body 4. While having a highly decorative uneven shape over the entire circumferential direction of the body 4, such a metal can 1 has an overlapping groove processing portion (overlap portion 10) where the groove processing is performed overlappingly (twice), as shown in FIG. 2, in order to ensure load-bearing capacity during manufacturing and external impact resistance after filling.

[0020] That is, in the body 4 of the metal can 1, the formation start position of the linear grooves 8 (processing position p1 shown in FIG. 3 and described below) and the formation end position of the linear grooves 8 (processing position p12 shown in FIG. 3 and described below) overlap to form the outline 9. The uneven shape formed by the outline 9 of the linear grooves 8 formed in the body 4 of the metal can 1 and the curved portions 11 between the linear grooves 8 has such overlapping portions 10, so that each of the connecting portions E1 and E2 in the outline 9 shown in FIG. 2 has an uneven shape without a break.

[0021] According to the metal can 1 of this embodiment, the outer peripheral surface 41 of the body 4 has an uneven shape with a highly decorative groove processing design 7 over the entire circumferential direction, while also having overlapping portions 10. This makes it possible to suppress a decrease in load-bearing capacity over the entire circumferential direction of the body 4 without increasing the thickness of the body 4 (including suppressing a decrease in the uniformity of load-bearing capacity over the circumferential direction of the body). As a result, even when the thickness of the body 4 is reduced, the metal can 1 can ensure load-bearing capacity and external impact resistance over the entire circumferential direction of the body 4 while forming a highly decorative uneven shape over the entire circumferential direction of the outer peripheral surface 41 of the body 4.

[0022] 3, the groove processing design 7 having an outline 9 formed by linear grooves 8 is formed so as to align with the printing position of each image portion of the printed image formed on the outer circumferential surface 41 of the body 4. For example, as shown in FIG. 3, an outline 9b formed by linear grooves 8 is formed on the outer periphery of the printed image portion 20a so that the printed image portion 20a, which has the product name (Lemon Sour) and an illustration of a lemon against a polka dot background, is positioned on the curved surface portion 11 within the outline 9b on the front side of the metal can 1. Also, for example, an outline 9b formed by linear grooves 8 is formed on the outer periphery of the printed image portion 20b so that the printed image portion 20b, which has an illustration of a glass with contents and ice against a polka dot background, is positioned on the curved surface portion 11 within the outline 9b on the back side of the metal can 1.

[0023] Furthermore, for example, contours 9a formed by linear grooves 8 are formed on the outer periphery of the printed image portion 20c so that printed image portions 20c having only an arbitrary solid color (for example, solid lemon color or another solid color) are arranged on the curved portions 11 within each contour 9a in the range from processing position p1 to processing position p3, the range from processing position p4 to processing position p8, and the range from processing position p9 to processing position p11.

[0024] 3, for example, within the range from processing position p9 to processing position p10 described below, printed image portion 20d of product information, etc. (raw material names, etc., bar code, ingredient labeling, etc.) on metal can 1 is printed. This printed image portion 20d of product information, etc. (raw material names, etc., bar code, ingredient labeling, etc.) is printed on a solid-color printed image portion 20c printed within the range from processing position p9 to processing position p10.

[0025] For example, the area outside the contour 9 on the outer surface 41 of the body 4 may have no printed image or may have any printed image (for example, a printed image having only any solid color throughout) (not shown).

[0026] The groove processing design 7 formed on the body 4 of the metal can 1 has contours 9a and 9b consisting of linear grooves 8, and the unevenness (three-dimensional effect) is further enhanced by printed image areas 20 (printed image areas 20a to 20c) arranged on the curved surface areas 11 inside the contours 9a and 9b. This makes the metal can 1 a beverage can with even greater decorativeness.

[0027] [Metal can manufacturing process] Next, an example of a manufacturing method (manufacturing process) for the metal can 1 according to this embodiment will be described with reference to the flowchart in Fig. 4. The manufacturing process for the metal can 1 is not limited to the example described here. The manufacturing process for the metal can 1 shown in the example of Fig. 4 includes, in this order, a cylindrical body forming step (step S1), a printing step (step S2), a bottom reforming step (step S3), a necking step (step S4), a flanging step (step S5), and a groove processing step (step S6) for processing grooves over the entire circumferential direction of the body portion 4 of the bottomed cylinder 100 (Figs. 5(a) and 5(b)).

[0028] (Step S1: Cylinder Forming Process) In the cylinder forming process of step S1, a bottomed cylinder (not shown) is formed from a plate-shaped metal material (not shown). Specifically, a plate-shaped metal material (not shown) such as an aluminum alloy is punched into a circle, and then a cup is formed by drawing (cupping) using a cupping press. The formed cup is then drawn and ironed, and the open end is trimmed using a trimmer (not shown). This forms a bottomed cylinder (not shown) having a body 4 and a bottom 5. The bottom 5 of the formed bottomed cylinder has a dome portion (not shown) that is recessed inward and an annular protrusion (not shown) that protrudes outward from the side opposite the recessed dome portion.

[0029] (Step S2: Printing process) In the printing process of step S2, a printing process is performed on at least the outer peripheral surface of the body 4 of the bottomed cylinder formed in step S1. If necessary, the inner surfaces of the body 4 and bottom 5 of the bottomed cylinder that have been subjected to outer peripheral printing may be painted (inner surface painting) by spraying or the like.

[0030] (Step S3: Bottom reform process) In the bottom reforming process of step S3, a desired bottom reforming roll (not shown) is used to press the inner surface of the dome portion of the bottom 5 of the bottomed cylindrical body (not shown) that has been printed in step S2 along the can axial direction (not shown), thereby reforming the bottom 5. By this bottom reforming, the dome portion and annular convex portion of the bottom 5 of the bottomed cylindrical body are deformed to the shapes of the dome portion (not shown) and annular convex portion (not shown) of the bottom 5 of the metal can 1.

[0031] (Step S4: Necking process) In the necking process of step S4, the bottom-reformed cylinder (not shown) is necked in multiple stages above the body 4 so that the diameter gradually decreases toward the open end of the bottom-reformed cylinder. This forms a neck 3 that gradually decreases in diameter so as to connect to the upper end of the body 4, and also forms an opening 6 with an opening diameter smaller than the inner diameter of the body 4.

[0032] (Step S5: Flanging process) In the flanging process of step S5, a flanging roller (not shown) is used to perform flanging, curling the portion of the bottomed cylinder on which the neck portion 3 is formed, which is connected to the upper end of the neck portion 3 (the portion where the opening 6 is formed), toward the outside of the bottomed cylinder, thereby forming a flange portion 2 above the neck portion 3 of the bottomed cylinder.

[0033] (Step S6: Grooving process) The method for manufacturing a metal can 1 according to this embodiment includes a groove processing step (step S6) after the necking step (step S4) and flanging step (step S5) described above. In this groove processing step, an outer roll 101 and an inner roll 102 shown in Fig. 5 are used to process grooves along the entire circumferential direction of the body 4 of a bottomed cylinder (hereinafter referred to as "bottomed cylinder 100") on which a neck portion 3 and a flange portion 2 are formed.

[0034] The outer roll 101 has an outer diameter D1 that is larger than the opening diameter d6 of the opening 6 of the bottomed cylinder 100. The inner roll 102 has an outer diameter D2 that is smaller than the opening diameter d6 (FIGS. 5(a) and 5(b)). Therefore, the radius of curvature R1 of the outer peripheral surface 101a of the outer roll 101 is larger than the radius of curvature R2 of the outer peripheral surface 102a of the inner roll 102 (FIG. 7). The outer peripheral surface 101a of the outer roll 101 has protrusions 81 (FIG. 6) for forming the linear grooves 8. The outer peripheral surface 102a of the inner roll 102 has recesses 82 (FIG. 6) for forming the linear grooves 8.

[0035] In this groove processing step (step S6), an inner roll 102 having an outer diameter D2 smaller than the opening diameter d6 is inserted through the opening 6 of the bottomed cylinder 100 (FIG. 5(a)), and this inner roll 102 is placed inside the body 4 of the bottomed cylinder 100 (FIG. 5(b)). At the same time, an outer roll 101 having an outer diameter D1 larger than the opening diameter d6 is placed outside the body 4 of the bottomed cylinder 100 (FIG. 5(b)).

[0036] The barrel portion 4 of the bottomed cylinder 100 is sandwiched between the outer roll 101 and the inner roll 102, and the outer roll 101 and the inner roll 102 are rotated synchronously to press the barrel portion 4 inward (inward in the radial direction), thereby forming linear grooves 8 in the barrel portion 4. During this process, the outer roll 101 rotates (spins) about the central axis M1 in the direction of the arrow in FIG. 5(b), and the inner roll 102 rotates (spins) about the central axis M2 in the direction of the arrow in FIG. 5(b). As a result, the barrel portion 4 of the bottomed cylinder 100 rotates (spins) about the central axis M0 in the direction of the arrow in FIG. 5(b). In this way, linear grooves 8 are formed in the barrel portion 4 of the bottomed cylinder 100.

[0037] As described above, the groove processing design 7 may be formed so as to align with the printing position of the printed image portion 20 (printed image portions 20a to 20c) formed on the outer peripheral surface 41 of the barrel 4, as in the example of Fig. 3. Alternatively, the groove processing design 7 may be formed so as to be intentionally shifted relative to the printed image portion 20. Alternatively, the groove processing design 7 may be formed in a location on the outer peripheral surface 41 of the barrel 4 that does not have a printed image portion 20. In this groove processing step (step S6), for example, a specific image such as a barcode in the printed image portion 20d is detected as a positioning mark, and the groove processing design 7 is aligned based on the positioning mark before groove processing begins.

[0038] On the outer peripheral surface 102a of the inner roll 102, one unit a1 of the groove processing design 7 is formed over the entire circumferential direction by recesses 82 for forming linear grooves 8 (FIG. 7). In FIG. 7, the relationship between the inner peripheral length of the body portion 4 of the bottomed cylinder 100 and the outer peripheral length of the unit a1 in the inner roll 102 is as follows. That is, as shown in FIG. 7, the outer peripheral surface 102a of the inner roll 102 has, over the entire circumferential direction, a unit a1 consisting of a constituent unit of the groove processing design 7, which is equal to the outer peripheral length of the inner roll 102, and the inner peripheral length of the body portion 4 of the bottomed cylinder 100 is twice the outer peripheral length of the unit a1 in the inner roll 102. As a result, on the body portion 4 of the bottomed cylinder 100, a concave-convex shape of the groove processing design 7 in which two unit portions a1 are connected over the entire circumferential direction is formed.

[0039] In the example of Figure 7, although not shown, the outer peripheral length of the outer roll 101 is, for example, four times the outer peripheral length of the unit part a1 in the inner roll 102, and the outer peripheral surface 101a of the outer roll 101 may be formed with a convex part 81 (to form linear grooves 8) in which four unit parts a1 are connected over the entire circumferential direction.

[0040] Note that the present invention is not limited to this example, and other examples may be used. For example, on the outer peripheral surface 102a of the inner roll 102, the unit portions a1, which are constituent units of the groove processing design 7, may be formed by equally dividing the outer peripheral length of the inner roll 102. Furthermore, the inner peripheral length of the trunk portion 4 of the bottomed cylinder 100 may be three times, four times, etc. (i.e., an integer multiple of three or more) the length of the unit portions a1 in the outer peripheral direction of the inner roll 102. In other words, when the unit portions a1 are constituent units of the groove processing design 7 on the outer peripheral surface 102a of the inner roll 102 that are equal to the outer peripheral length of the inner roll 102 or formed by equally dividing that outer peripheral length, the inner peripheral length of the trunk portion 4 of the bottomed cylinder 100 may be n times (n is an integer of 2 or more) the length of the unit portions a1 in the outer peripheral direction of the inner roll 102.

[0041] Furthermore, there is no particular limitation on the outer peripheral length of the outer roll 101 used together with such an inner roll 102. That is, it is sufficient that the outer peripheral surface 101a of the outer roll 101 is formed with convex portions 81 corresponding to the concave portions 82 of the inner roll 102 so that a desired number of unit portions a1 are formed all around the circumferential direction of the body portion 4 of the bottomed cylindrical body 100, and the outer peripheral length of the outer roll 101 is no particular limitation.

[0042] For example, in the example of FIG. 8 instead of the example of FIG. 7 , three unit portions a1 of a groove processing design 7 different from the example of FIG. 2 are formed on the outer peripheral surface 102a of the inner roll 102 over the entire circumferential direction by recesses 82 for forming linear grooves 8. In this case, the relationship between the inner peripheral length of the body portion 4 of the bottomed cylinder 100 and the outer peripheral length of the unit portions a1 in the inner roll 102 is as follows: That is, the outer peripheral surface 102a of the inner roll 102 has three unit portions a1 each consisting of a constituent unit of the groove processing design 7, which are obtained by dividing the outer peripheral length of the inner roll 102 into thirds, and the inner peripheral length of the body portion 4 of the bottomed cylinder 100 is six times the outer peripheral length of the unit portions a1 in the inner roll 102. As a result, the body portion 4 of the bottomed cylinder 100 is formed with an uneven shape of the groove processing design 7 in which six unit portions a1 are connected over the entire circumferential direction.

[0043] In the example of Figure 8, although not shown, the outer peripheral length of the outer roll 101 is, for example, four times the outer peripheral length of the unit part a1 in the inner roll 102, and the outer peripheral surface 101a of the outer roll 101 may be formed with a convex part 81 (to form linear grooves 8) in which, for example, 12 unit parts a1 are connected over the entire circumferential direction.

[0044] In this way, the method for manufacturing a metal can 1 according to this embodiment uses an inner roll 102 such that the inner peripheral length of the body portion 4 of the bottomed cylinder 100 is n times (n is an integer of 2 or more) the length of the unit portion a1 in the outer peripheral direction of the inner roll 102. That is, the outer diameter D2 of the inner roll 102 is set relative to the inner diameter d1 of the body portion 4 of the bottomed cylinder 100 so that the inner peripheral length of the body portion 4 of the bottomed cylinder 100 is n times (n is an integer of 2 or more) the length of the unit portion a1 in the inner roll 102 in the outer peripheral direction. In this case, the outer diameter D2 of the inner roll is 1 / m (m is an integer of 2 or more) of the inner diameter d1 of the body portion 4 of the bottomed cylinder 100.

[0045] This groove machining process involves machining linear grooves 8 around the entire circumference of the body 4 of the bottomed cylinder 100, and this groove machining is carried out through the linear groove forming process (step S61), the contour forming process (step S62), and the overlapping process (step S63), which will be described below.

[0046] In the linear groove forming step (step S61), the barrel portion 4 is sandwiched between the outer roll 101 and the inner roll 102, and the outer roll 101 and the inner roll 102 are rotated synchronously to start a groove processing process in which the barrel portion 4 is pressed in the inward radial direction, thereby forming linear grooves 8 in the barrel portion 4 of the bottomed cylinder 100. In the example of FIG. 3 , this pressing is performed from processing position p1 in the circumferential direction of the barrel portion 4 (the starting position for forming linear grooves 8), and groove processing proceeds along that circumferential direction (to the right in FIG. 3 ). As a result, linear grooves 8 are formed in the inward radial direction of the barrel portion 4 of the bottomed cylinder 100 from processing position p1 to processing position p2 in the circumferential direction. Note that when the groove processing reaches processing position p2, a portion of the contour 9a is formed. In addition, curved surface portions 11 that are convex in the outer radial direction of the barrel portion 4 are formed between the linear grooves 8. Note that the curved surface portions 11 are unprocessed portions.

[0047] In the method for producing a metal can 1 according to this embodiment, the inner roll 102 used in the groove processing has an outer diameter D2 smaller than the opening diameter d6. When processing the body portion 4 using an inner roll 102 having such a relatively small outer diameter D2, there is usually a risk that the body portion 4 of the bottomed cylinder 100 sandwiched between the outer roll 101 and the inner roll 102 will be easily bent outward in the radial direction (easily slip away). Therefore, in the linear groove forming step (step S61) in the method for producing a metal can 1, as shown in FIG. 6 , groove processing is performed so that the shortest distance T1 [mm] between the outer peripheral surface 101a of the outer roll 101 and the outer peripheral surface 102a of the inner roll 102 when groove processing is performed is 1.1 to 3.7 times, preferably 1.6 to 2.4 times, the thickness F1 [mm] of the body portion 4 of the bottomed cylinder 100.

[0048] By making the shortest distance T1 [mm] 3.7 times the plate thickness F1 [mm] or less, bending (escape) of the trunk portion 4 toward the outer diameter side (radially outward) can be suppressed even when using an inner roll 102 whose outer diameter D2 is smaller than the opening diameter d6, and linear grooves 8 having a clear shape can be formed that follow the shapes of the convex portions 81 of the outer roll 101 and the concave portions 82 of the inner roll 102. Furthermore, by making the shortest distance T1 [mm] 1.1 times the plate thickness F1 [mm] or more, it is possible to reduce friction caused by contact of the trunk portion 4 with at least one of the outer roll 101 and the inner roll 102 while ensuring the plate thickness F1 required for the trunk portion 4 of the bottomed cylinder 100, and to suppress poor formation of the linear grooves 8.

[0049] If the ratio of the shortest distance T1 [mm] to the plate thickness F1 [mm] is smaller than a predetermined ratio, a pressing force is applied to the curved portion 11 of the body portion 4 between the inner roll 102 and the outer roll 101 during the groove processing step, resulting in a thin plate thickness F of the linear grooves 8, which reduces the load-bearing capacity (buckling strength, etc.) during manufacturing and the external impact resistance after filling with contents. On the other hand, if the ratio of the shortest distance T1 [mm] to the plate thickness F1 [mm] is larger than a predetermined ratio, the shape of the linear grooves 8 becomes blurred, leading to a poor appearance.

[0050] In the metal can 1 (bottomed cylindrical body 100 with grooves) according to this embodiment, the horizontal cross-sectional shape of the body 4 has linear grooves 8 that protrude in the inner diameter direction (inward in the radial direction) and curved surface portions 11 that protrude in the outer diameter direction (outward in the radial direction). The body 4 has these curved surface portions 11 between the linear grooves 8. It is speculated that during the groove processing step, stress is applied to the curved surface portions 11 that tends to spread in the outer diameter direction. By ensuring a certain minimum distance T1, the pressure on the body 4 is alleviated, and material is more easily drawn into the recesses 82. As a result, the strength of the linear grooves 8 can be maintained in the metal can 1 (bottomed cylindrical body 100 with grooves), which is thought to enable a balance between mechanical strength, such as load-bearing capacity (e.g., buckling strength) during manufacturing and external impact resistance after filling, and appearance.

[0051] When groove machining reaches machining position p2 in the circumferential direction of the trunk portion 4 of the bottomed cylinder 100, groove machining to form linear grooves 8 continues, and from machining position p2, contours 9 are sequentially formed by these linear grooves 8 (contour forming process (step S62)). That is, contours 9a are formed by the linear grooves 8 in the range from machining position p2 to machining position p3. Similarly, contours 9b are formed by the linear grooves 8 in the circumferential direction of the trunk portion 4 of the bottomed cylinder 100 in the range from machining position p3 to machining position p4, and contours 9a are formed by the linear grooves 8 in the range from machining position p4 to machining position p5, the range from machining position p5 to machining position p7, and the range from machining position p7 to machining position p8. Similarly, contours 9b are formed by the linear grooves 8 in the range from machining position p8 to machining position p9, and contours 9a are formed by the linear grooves 8 in the range from machining position p9 to machining position p10.

[0052] When the groove machining is performed to form linear grooves 8 from machining position p10 to machining position p11 in the circumferential direction of the body 4 of the bottomed cylinder 100, a part of the contour 9a is formed. Even if the series of groove machining processes ends when the groove machining reaches machining position p11, the groove machining design 7 made of the linear grooves 8 is formed over the entire circumferential direction of the body 4 of the bottomed cylinder 100.

[0053] However, in the manufacturing method of the metal can 1 according to this embodiment, the groove processing continues even when it reaches processing position p11, and an overlap process is performed in which a groove is again processed on the previously formed linear groove 8 in a narrow range from processing position p11 (i.e., processing position p1) to processing position p12 (overlap process (step S63)). That is, in this overlap process, the formation start position (processing position p1) of the linear groove 8 in the body portion 4 of the bottomed cylinder 100 and the formation end position (processing position p12) of the linear groove 8 are overlapped to form the outline 9a.

[0054] By this overlapping process, the narrow overlap portion 10 shown in Fig. 2 is formed. When this overlapping process (step S63) is completed, the groove processing process (step S6) is completed. This completes the series of processes in the manufacturing method of the metal can 1.

[0055] According to the method for manufacturing a metal can 1 of this embodiment, groove processing is performed after necking (and further flanging), so that a highly decorative uneven shape such as the groove processing design 7 described above can be formed over the entire circumference of the body portion 4, while still ensuring sufficient uniformity of the load-bearing capacity in the circumferential direction of the body portion 4. Therefore, according to this method for manufacturing a metal can 1, processing accuracy can be ensured in the necking (and further flanging), and formation defects such as buckling can be suppressed in the body portion 4 with the uneven shape formed therein during necking (and further during flanging and lid seaming).

[0056] In this method for manufacturing metal can 1, defects such as buckling do not occur in body 4, so that the load-bearing capacity in other manufacturing steps and the resistance to external impacts after filling with contents can be maintained, and as a result, deformation of the can body can be suppressed. Furthermore, in this method for manufacturing metal can 1, groove processing is performed after necking (and further flanging), so the method of necking is not limited, and therefore the degree of freedom in the shape of neck portion 3 can be ensured.

[0057] In the method for manufacturing a metal can 1 according to this embodiment, a constituent unit of the groove processing design 7 on the outer periphery of the inner roll 102 is a unit a1, which is equal to the outer periphery length of the inner roll 102 or is an equal division of the outer periphery length, and the outer diameter D2 of the inner roll 102 is set relative to the inner diameter d1 of the body portion 4 of the bottomed cylinder 100 so that the inner periphery length of the body portion 4 of the bottomed cylinder 100 is n times (n is an integer of 2 or more) the length of the unit portion a1 in the outer periphery direction of the inner roll 102. In this method for manufacturing a metal can 1, groove processing is performed using such an inner roll 102 and the outer roll 101 described above.

[0058] Furthermore, in this groove processing, an overlapping process is performed in which the formation start position of the linear grooves 8 in the body portion 4 of the bottomed cylinder 100 (processing position p1 in FIG. 3) and the formation end position of the linear grooves 8 (processing position p12 in FIG. 3) are overlapped to form the outline 9. As a result, this manufacturing method for the metal can 1 makes it possible to manufacture a metal can 1 having an uneven shape without any breaks at the joints (joints E1 and E2 in FIG. 2) in the outline 9 formed by the linear grooves 8 formed in the body portion 4.

[0059] The metal can 1 manufactured by the manufacturing method of this embodiment has a highly decorative appearance due to the uneven shape formed around the entire circumference of the body 4, and the uneven shape does not have any breaks (disorders in the uneven shape) at the circumferential joints, resulting in a beverage can with excellent appearance. This manufacturing method for metal can 1 maintains uniform load resistance around the circumference of the body 4 during necking (and further during flanging), because the uneven shape is not distorted at the joints of the uneven shape formed on the body 4, thereby ensuring processing precision. This manufacturing method for metal can 1 therefore prevents defects in the body 4 due to buckling, etc.

[0060] Furthermore, according to the manufacturing method of the metal can 1 of this embodiment, there is no disruption of the uneven shape at the connecting portions of the uneven shape formed on the body portion 4, which makes it possible to maintain load-bearing capacity in other manufacturing processes and external impact resistance after filling the can with contents. As a result, with this metal can 1, it is possible to suppress deformation of the can body due to disruption of the uneven shape.

[0061] Furthermore, according to the method for manufacturing the metal can 1 of this embodiment, it is not necessary to increase the thickness of the body 4 in order to ensure load-bearing capacity during manufacturing and resistance to external impact after filling with the contents, and therefore it is possible to reduce the gauge of the material.

[0062] As described above, according to the manufacturing method of the metal can 1 of this embodiment, even when the thickness of the body 4 of the bottomed cylindrical body 100 is reduced, it is possible to manufacture a metal can 1 that ensures the processing accuracy of the necking process and the degree of freedom in the neck shape, and that can form a highly decorative uneven shape on the body 4 without causing any problems in appearance, while ensuring load-bearing capacity during manufacturing and resistance to external impact after filling.

[0063] Although the present embodiment has been described in detail above with reference to the drawings, the specific configuration is not limited to the above embodiment. Furthermore, the present invention also includes design changes within the scope of the present invention. Furthermore, the above examples can be combined by utilizing each other's technologies as long as there are no particular contradictions or problems in the purpose, configuration, etc. [Explanation of symbols]

[0064] 1: metal can, 2: flange portion, 3: neck portion, 4: body portion, 5: bottom, 6: opening, 7: groove processing design, 8: linear groove, 9, 9a, 9b: contour, 10: overlap portion, 11: curved surface portion, 20a to 20d: printed image portion, 41: outer peripheral surface, 81: convex portion, 82: concave portion, 100: bottomed cylinder, 101: outer roll, 101a: outer peripheral surface, 102: inner roll, 102a: outer peripheral surface, a1: unit portion

Claims

1. a cylindrical body forming step of forming a bottomed cylindrical body from the plate-shaped metal material; a necking step of performing necking processing on a portion of the bottomed cylindrical body above a body portion to form an opening having an opening diameter smaller than an inner diameter of the body portion; a groove processing step of performing groove processing over the entire circumferential direction of the barrel portion using an outer roll and an inner roll after the necking step, The groove processing step includes: a step of sandwiching the barrel portion between the outer roll and the inner roll, and rotating the outer roll and the inner roll synchronously to press the barrel portion in an inward radial direction, thereby forming linear grooves in the barrel portion; forming a contour on the body portion by the linear groove; forming the contour by overlapping a formation start position of the linear groove and a formation end position of the linear groove in the body portion; A method for manufacturing a metal can, comprising the steps of:

2. When a constituent unit of a groove processing design, which is equal to the outer peripheral length of the inner roll or is obtained by equally dividing the outer peripheral length of the inner roll, is defined as a unit part, The inner peripheral length of the barrel portion is n times (n is an integer of 2 or more) the length of the unit portion in the outer peripheral direction of the inner roll. The method for manufacturing a metal can according to claim 1 .

3. The outer diameter of the inner roll is 1 / m (m is an integer of 2 or more) of the inner diameter of the barrel portion. The method for manufacturing a metal can according to claim 1 .

4. The radius of curvature of the outer peripheral surface of the outer roll is larger than the radius of curvature of the outer peripheral surface of the inner roll. The method for manufacturing a metal can according to claim 2 .

5. In the step of forming the linear grooves, the shortest distance [mm] between the outer peripheral surface of the outer roll and the outer peripheral surface of the inner roll when performing the groove processing is 1.1 to 3.7 times the plate thickness [mm] of the body portion. The method for manufacturing a metal can according to claim 4.

6. In the step of forming the linear grooves, the shortest distance [mm] between the outer peripheral surface of the outer roll and the outer peripheral surface of the inner roll when performing the groove processing is 1.6 to 2.4 times the plate thickness [mm] of the body portion. The method for manufacturing a metal can according to claim 4.

7. A printing step is included which prints at least on the outer peripheral surface of the body portion after the cylindrical body forming step and before the necking step. The method for manufacturing a metal can according to claim 1 .

8. A metal can in which a necking process is performed on a portion above a body of a bottomed cylindrical body formed from a plate metal material, thereby forming an opening having an opening diameter smaller than the inner diameter of the body, and after the necking process, a groove processing process is performed over the entire circumferential direction of the body using an outer roll and an inner roll, In the groove processing, the barrel portion is sandwiched between the outer roll and the inner roll, and the outer roll and the inner roll are rotated synchronously to press the barrel portion in the inward radial direction, thereby forming linear grooves in the barrel portion, and a curved surface portion that is convex in the outer radial direction is formed between the linear grooves, and a contour is formed on the barrel portion by the linear grooves, and the contour is formed by overlapping a formation start position of the linear groove in the barrel portion and a formation end position of the linear groove, and there is no break in the connecting portion of the contour. A metal can characterized by:

Images