Seamless can body and method for manufacturing a seamless can body

Abstract

A seamless tank with excellent pressure resistance and a method for manufacturing the same are provided. The seamless tank of the present invention includes a cylindrical main body (10), a circumferential grounding portion (20b) connected to the lower end of the cylindrical main body, and a rising bottom (30) connected from the circumferential grounding portion toward the central axis. The surface area of ​​the outer surface of the rising bottom is defined as A. D The area of ​​the imaginary plane with the periphery as its outline is defined as A. B When, 1.55≥(A) D / A B The relationship is ≥1.40.

Description

Technical Field

[0001] This invention relates to seamless tanks and methods for manufacturing seamless tanks. Background Technology

[0002] Previously, so-called seamless can bodies were known, formed by thinning the can body through drawing. These seamless can bodies achieve excellent lightweight properties by thinning the can body after shallow drawing. Furthermore, various methods have been proposed for maintaining or improving pressure resistance even when the bottom of the can is thinned in these seamless can bodies.

[0003] For example, Patent Documents 1 and 2 disclose a so-called bottom improvement process implemented to prevent the phenomenon of the rounded top of the can bottom inverting (bending) when the internal pressure of the can exceeds the pressure resistance strength. Specifically, the bottom improvement process discloses forming a concave portion by pressing the inner circumferential wall of the grounding part of the can bottom, which is located radially inside the can axis.

[0004] Existing technical documents

[0005] Patent documents

[0006] Patent Document 1: Japanese Patent Application Publication No. 2018-103227

[0007] Patent Document 2: Japanese Patent Application Publication No. 2016-47541 Summary of the Invention

[0008] The problem that the invention aims to solve

[0009] That is, in the bottom improvement process described above, forming rollers or the like are usually used to press the inner circumferential wall of the bottom of the can to form a concave part.

[0010] Furthermore, recently, in order to achieve lightweight seamless tanks, there has been a growing demand for thinner sheet metal (blanks) before the drawing and thinning process. However, when the aforementioned bottom improvement process is implemented, the thickness of the metal material of the pressing part, such as the forming roller, which is in contact with the forming roller, is extended and thinned through this process, thus there is a limit to the reduction of the sheet metal (blank) thickness.

[0011] The inventors, through repeated and careful study of the problems illustrated above, have been able to provide a seamless tank with excellent pressure resistance and a method for manufacturing the same, thus completing the present invention.

[0012] Solution for solving the problem

[0013] A seamless tank body according to an embodiment of the present invention is characterized in that (1) the seamless tank body comprises: a cylindrical main body portion; a circumferential grounding portion connected to the lower end of the cylindrical main body portion; and a rising bottom portion connected from the circumferential grounding portion toward the central axis side, wherein the outer surface area of ​​the rising bottom portion is defined as A. D The area of ​​the imaginary plane with the periphery as its outline is defined as A. B When, 1.55≥(A) D / A B The relationship is ≥1.40.

[0014] Furthermore, in the seamless tank body described in (1) above, it is preferable that (2) the volume of the space enclosed by the imaginary plane and the rising bottom is defined as V. D The volume of the metal component forming the rising bottom is defined as V. M When, 26.0 ≥ (V D / V M The relationship is ≥22.0.

[0015] In addition, to solve the above-mentioned problems, a method for manufacturing a seamless can body according to an embodiment of the present invention is characterized in that (3) the method for manufacturing a seamless can body includes: a first forming step of forming a metal raw material into a cup body having a cylindrical main body, an outer peripheral bottom continuous from the lower end of the cylindrical main body, and a bulging portion bulging out from the outer peripheral bottom toward an opening at a first height; and a second forming step of pressing down the bulging portion to form a circumferential grounding portion connected from the lower end of the cylindrical main body and a rising bottom connected from the circumferential grounding portion toward a central axis side, wherein the outer surface area of ​​the rising bottom is defined as A. D The area of ​​the imaginary plane with the periphery as its outline is defined as A. B When, 1.55≥(A) D / A B The relationship is ≥1.40.

[0016] Invention Effects

[0017] According to the present invention, a seamless tank body can be obtained with a smaller amount of material by preventing buckling through a rising bottom with excellent pressure resistance. Attached Figure Description

[0018] Figure 1 This is a schematic diagram showing the overall longitudinal section of the seamless tank in the embodiment.

[0019] Figure 2 This is an enlarged view showing the bottom of the seamless tank in the embodiment.

[0020] Figure 3 It is used to describe the surface area A of the outer surface of the rising bottom. D The area A of the imaginary plane of the circumferential grounding part as the outline. B The volume V of the space enclosed by the imaginary plane and the rising base. D and the volume V of the metal component forming the rising bottom. M A schematic diagram.

[0021] Figure 4 This is a flowchart illustrating the manufacturing method of the seamless tank in the implementation method.

[0022] Figure 5 This is a diagram illustrating the first forming process in a method for manufacturing a seamless tank according to an embodiment.

[0023] Figure 6 This is a diagram illustrating the second forming step in the manufacturing method of a seamless tank according to an embodiment.

[0024] Figure 7 This is a schematic diagram illustrating the compressive stress applied to the erected portion in the embodiment.

[0025] Figure 8 This is a schematic diagram illustrating the state changes of the provisional circumferential grounding portion after the first forming process and the circumferential grounding portion after the second forming process in the seamless tank body of the embodiment.

[0026] Figure 9 This is a schematic diagram illustrating an example of applying an organic coating to the bottom of a seamless can.

[0027] Figure 10 This is a schematic diagram showing the perimeter of the bottom of the can in the experimental example. Detailed Implementation

[0028] The seamless tank body and its manufacturing method of the present invention will be specifically described below with appropriate reference to the accompanying drawings. It should be noted that the following embodiments are merely examples illustrating the present invention and are not intended to limit the scope of the invention.

[0029] [First Implementation Method]

[0030] <Seamless Tank 1>

[0031] like Figure 1 As shown, the seamless tank 1 of this embodiment is a seamless tank having a cylindrical main body 10 and a tank bottom 20, and the tank bottom 20 has at least an outer peripheral bottom 20a that is continuous from the lower end of the cylindrical main body 10. It should be noted that, in the illustration, the neck flange shape is depicted as an example above the cylindrical main body 10, but a known seamless tank structure with an opening 10a can be applied above the cylindrical main body 10.

[0032] The cylindrical main body 10 forms the side of the seamless tank 1 and is formed by drawing and thinning a known metal sheet such as aluminum or steel, as described later. The cylindrical main body 10 has a width depending on the application, and for example, it has a thickness of approximately 0.07 to 0.40 mm.

[0033] In this embodiment, the lower end 10e of the cylindrical main body 10 (described later) is the lower end, and the upper end is as follows: Figure 1 The definition shown is the junction with the neck and shoulder (the part that narrows as it moves upwards along the axis).

[0034] 20 at the bottom of the can Figure 1 That would include at least an outer peripheral bottom 20a that narrows continuously from the lower end 10e of the aforementioned cylindrical main body 10 toward the inward side, and a rising bottom 30 that bulges out from the inside of the outer peripheral bottom 20a toward the opening 10a.

[0035] It should be noted that, from Figure 1 It is also clear that in this embodiment, the outer peripheral bottom 20a and the rising bottom 30 are divided by the circumferential grounding portion 20b that is grounded when the seamless tank 1 is placed on a flat surface such as a table. In other words, the circumferential grounding portion 20b can be said to be the part connected to the lower end 10e of the cylindrical main body 10, and the outer peripheral bottom 20a can be said to be the part located between the cylindrical main body 10 and the circumferential grounding portion 20b.

[0036] Thus, the seamless tank 1 has a rising bottom 30 that convexly forms upward from the circumferential grounding portion 20b. As clearly shown in the figures, the rising bottom 30 in this embodiment is formed by connecting from the circumferential grounding portion 20b toward the central axis. It should be noted that in this embodiment, the rising bottom 30 rises from the circumferential grounding portion 20b and becomes a gently dome-shaped (protruding forward) shape, but it is not limited to this shape; at least a portion of the top may also be flat.

[0037] It should be noted that, in this embodiment, there are no particular limitations on the type of metal material used for the seamless tank 1. That is, commonly known metal sheets used for seamless tanks, such as aluminum alloy sheets or steel sheets (e.g., galvanized iron sheets), can be used. Moreover, the metal sheet can also be a structure with a known film laminated on at least one side, a structure coated with an organic resin, a structure that has undergone chemical conversion treatment, etc., and the surface can be appropriately coated.

[0038] Furthermore, the seamless tank 1 of this embodiment is processed by known methods such as flange processing, necking processing, and thread processing. Moreover, after containing beer, carbonated beverages, coffee, juice, liquid food, etc. as contents, a lid or cap is installed at the opening 10a by known methods.

[0039] <Characteristics of the 30-day rising bottom structure>

[0040] Next, refer to Figure 1 and 3 The structure of the rising bottom 30 described above in this embodiment will be described in detail.

[0041] As can be clearly seen from these figures, regarding the rising bottom 30 in the seamless tank 1 of this embodiment, the outer surface area of ​​the rising bottom 30 is defined as A. D The area of ​​the imaginary plane VP with the circumferential grounding portion 20b as its outline is defined as A. B When the bottom 30 rises, it satisfies the relationship shown in equation (1).

[0042] 1.55≥(A D / A B )≥1.40…(1)

[0043] As mentioned above, in recent years, there has also been an increase in the variety of beverages offered to the market, including carbonated beverages with increased internal pressure, such as those in cans with so-called strong carbonation. With this growing demand, it is conceivable that seamless cans for storing these strongly carbonated or carbonated beverages like beer, as well as non-carbonated beverages like fruit juices, will also require excellent pressure resistance. While increasing the plate thickness could be considered to improve the pressure resistance of seamless cans, this would increase the weight and cost of the can itself, making it impractical.

[0044] Therefore, after careful consideration, the inventors concluded that the rising bottom 30 disclosed in this embodiment exhibits excellent pressure resistance when satisfying the relationship in (1) above. That is, the above-mentioned (A) D / A B This concept parameterizes (numerically) the upward bulge of the rising bottom 30 in this embodiment. When (A) is used as the bulge degree... D / A B When the value exceeds 1.40, it can ensure a balance between the plate thickness and pressure resistance that are commonly accepted in the product market.

[0045] It should be noted that the surface area A of the outer surface of the bottom 30 is... D The area A of the imaginary plane VP BWhile it is possible to calculate using known formulas, the shape can be easily and accurately determined using, for example, a commercially available shape measuring machine. In this embodiment, a CONTOURECORD (model 1600DH) manufactured by Tokyo Seimitsu Corporation was used as such a shape measuring machine for measurement. That is, the cross-sectional shape was obtained by transferring the shape data generated by the up-and-down movement of a stylus moving in a plane passing through the central axis of the cup to a CAD system, and the surface area and volume (multiplied by separately measured plate thickness data) of the rotating body were measured with sufficient accuracy based on this.

[0046] On the other hand, when the degree of bulging (A) D / A B When the thickness is less than 1.40, the rigidity of the rising bottom cannot be guaranteed, and the plate thickness must be further increased, which will lead to adverse situations such as increased costs and waste of resources, and it is difficult to ensure the balance between the plate thickness and pressure resistance.

[0047] It should be noted that, regarding (A) as the degree of bulging... D / A B The upper limit of (A) can be set in various ways depending on the specifications of the tank required by the market, but is preferably, for example, below 1.55. This is because, when it becomes (A) D / A B When the area of ​​the material exceeds 1.55, the material area becomes excessive, which can lead to adverse situations such as increased costs or wasteful use of resources.

[0048] Furthermore, when considering transportation costs, the seamless tank 1 of this embodiment preferably exhibits excellent pressure resistance and is lightweight. Based on this viewpoint, the inventors' pursuit is that, in addition to the excellent pressure resistance described above, the rising bottom 30 disclosed in this embodiment can also achieve lightweight design when further satisfying the relationship in (2) above.

[0049] That is, the volume of the space enclosed by the imaginary plane VP and the rising bottom 30 is defined as V. D The volume of the metal component forming the rising bottom 30 is defined as V. M When the condition is met, it is preferable to satisfy the relationship shown in equation (2) below.

[0050] 26.0≥(V D / V M )≥22.0…(2)

[0051] It should be noted that, similar to the above, the volume V of the rising bottom 30 is... D Volume V of metal components MIt can also be calculated using known formulas, but it can be easily and accurately determined using a commercially available shape measuring machine. In this embodiment, the volume V was also measured using the aforementioned shape measuring machine (Tokyo Seimitsu Corporation, trade name: CONTOURECORD, model 1600DH). D and volume V M The determination.

[0052] It should be noted that the above (V) D / V M In this embodiment, it functions as a balancing indicator between pressure resistance, lightweight, and container capacity. D / V M The upper limit of ) is preferably below 26. This is because, when it becomes (V D / V M When the pressure resistance is greater than 26, compared with the improvement in pressure resistance, there will be disadvantages such as increased cost and decreased capacity.

[0053] <Manufacturing Method of Seamless Tank 1>

[0054] Next, the manufacturing method of the seamless tank 1 in this embodiment will also be appropriately referred to. Figures 4-8 Please provide an explanation.

[0055] The manufacturing method of the seamless tank 1 in this embodiment is... Figure 1 The manufacturing method of a seamless tank having a cylindrical main body 10 and a tank bottom 20 as shown, such as Figure 4 As shown, it includes at least a first forming process as step 1 and a second forming process as a subsequent step.

[0056] [First forming process]

[0057] In this embodiment, the manufacturing method of the seamless tank 1 involves forming a cup body 2 from a metal raw material (precursor 3) in the first forming process. The cup body 2 has a cylindrical main body 10, a continuous outer peripheral bottom 20a from the lower end 10e of the cylindrical main body 10, and a bulge 4 extending from the outer peripheral bottom 20a toward the opening at a first height Ho (see reference). Figure 5 At this time, a temporary circumferential grounding portion 20a′ is positioned at the lower end, which is closer to the inner side of the cylindrical main body portion 10 and at the junction with the bulge portion 4. The cup body 2 can be formed by known forming processes such as drawing / redrawing forming and drawing / thinning forming.

[0058] In other words, in this first forming process, it can also be said that the metal raw material (precursor 3) is formed into a cup body 2. The cup body 2 has a cylindrical main body 10, a provisional circumferential grounding portion 20a′ located at the lower end inside the cylindrical main body 10, and a bulge 4 with a first height Ho located inside the provisional circumferential grounding portion 20a′.

[0059] Furthermore, as shown in the figure, the bulge 4 of the cup body 2 in this embodiment is composed of an inclined portion S extending inward and upward from the outer peripheral bottom 20a and a cup-shaped top D extending inward from the end Se of the inclined portion S. Moreover, in the manufacturing method of the seamless can body in this embodiment, a known method, such as the one disclosed in Japanese Patent Application Publication No. 9-285832, can be used as the forming method of the cylindrical main body 10.

[0060] More detailed explanation Figure 5 (a)~(c) illustrate the process steps.

[0061] First, using the aforementioned metal raw material (bulk), the main body of the can is formed by a known method, thereby preparing a precursor 3 with a cup shape.

[0062] Then, the metal raw material (precursor 3) is formed into a cup body 2, which has a cylindrical main body 10, a continuously tapering outer peripheral bottom A from the lower end 10e of the cylindrical main body 10, and a bulging portion 4 extending upwards and inwards from the outer peripheral bottom A at a first height Ho. Here, the end Se of the inclined portion S can also be referred to as the connection point connecting to the cup dome D.

[0063] Figure 5 The first forming process shown can be performed as a separation process using an upper die and a lower die for the precursor body 3 that has been formed into a cylindrical main body 10 by a known stamping process, or it can be performed at the end of the stroke after the thinning process.

[0064] As a specific example, such as Figure 5 As shown, the first forming process described above is performed by a cylindrical punch 401 located inside and supporting the cup-shaped precursor 3, a clamping ring 501 cooperating with the punch 401 to support the outer periphery bottom of the precursor 3, and a punch 502.

[0065] First, the outer periphery of the precursor body 3 is held by the tapered portion 402 of the punch 401 and the tapered support portion 503 of the clamping ring 501. The two parts are driven to approach each other in such a way that the punch 401 engages with the punch 502, so that a cup body 2 with a cup-shaped dome D with Ho at the bottom can be obtained.

[0066] Here, the shape of the cup body 2 obtained through the first forming process described above will be explained. That is, the inclined portion S in the cup body 2 extends from the bottom A of the outer periphery of the cup toward the inner and upper side.

[0067] That is, such as Figure 5 As shown, the inclined part S of the cup body 2 refers to the curved part and the straight part that are held by the lowest part of the cup body 2 in the Z-axis direction and the junction (end Se) with the top of the cup D.

[0068] It should be noted that the shape of the cup dome D described above is an example. The top of the dome may also be a horizontal surface, for example, instead of a curved surface.

[0069] like Figure 5 As shown in (c), the inclined portion S can be vertical, but it is more preferably inclined at a predetermined angle θ1. That is, the angle θ1 between the inclined portion S and the Z-axis is preferably 5° to 30°, and more preferably 10° to 30° in order to facilitate the formation of a coating on the inner surface by spraying after the first forming process.

[0070] Additionally, regarding the radius of curvature R at the angle θ2 formed by the bottom A of the outer perimeter of the cup to the inclined portion S (refer to...) Figure 5 (c) In addition to a single radius of curvature, a curve connecting multiple different radii of curvature can also be set. If, for example, there is a single radius of curvature R, the thickness of the original plate (blank) is set to t0. In order to facilitate the formation of a coating on the inner surface by spraying after the first forming process, it is more preferable to set R = 5 × t0 ~ 15 × t0.

[0071] Furthermore, the first height Ho of the cup top D in the cup body 2 is preferably greater than the height Hp of the rising bottom 30 in the seamless can 1 obtained through the second forming process described later. The reason for this is that in the second forming process, compressive stress is applied to the inclined portion S while the cup top D in the cup body 2 is pressed down. That is, by increasing the first height Ho of the cup top D in the cup body 2 beforehand, the preferred height Hp of the rising bottom 30 is ultimately obtained in the seamless can 1.

[0072] [Second forming process]

[0073] Next, refer to Figure 6 This section explains the second forming step in the manufacturing method of the seamless tank 1 in this embodiment.

[0074] After forming the cup body 2 having the provisional circumferential grounding portion 20a′ and the inclined portion S through the first forming process described above, the second forming process detailed below is performed.

[0075] That is, in the second forming step of the manufacturing method of the seamless tank 1 in this embodiment, the above-mentioned bulge 4 is pressed down to become a second height Hp that is lower than the first height Ho, forming a circumferential grounding portion 20b connected to the lower end 10e of the cylindrical main body portion 10 and a rising bottom 30 connected from the circumferential grounding portion 20b toward the central axis side.

[0076] In other words, in this second forming process, it can be said that the aforementioned bulge 4 is pressed down on the cup body 2, thereby forming a circumferential grounding portion 20b disposed at a different position from the provisional circumferential grounding portion 20a′ and a rising bottom 30 having a height Hp lower than the first height Ho.

[0077] The shape of the rising bottom 30 at this time, as described above, satisfies the condition of the outer surface area A. D The area A of the imaginary plane VP B The above-described formula (1) is given. Furthermore, the shape of the rising bottom 30 preferably satisfies the volume V of the space enclosed by the imaginary plane VP and the rising bottom 30. D The volume V of the metal component forming the rising bottom M The above formula (2) is specified.

[0078] More specifically, in the second forming process, the cup body 2 is processed using a mold different from the forming mold in the first forming process to form a seamless can body 1. That is, while the cup body 2 is brought into contact with the lower forming member, the upper forming member applies pressure to the cup-shaped top D of the cup body 2 in the outward direction (-Z axis direction).

[0079] Alternatively, while the cup body 2 is in contact with the lower mold forming member and the upper mold forming member, the lower mold forming member can be used to apply pressure in the +Z axis direction.

[0080] More specifically, such as Figure 6 As shown, the bottom A of the outer periphery of the cup body 2 is placed on the outer periphery support 60. The dome pressing tool 70 descends relative to the cup body 2, and the support portion 701 of the dome pressing tool 70 contacts the dome D of the cup. Here, the outer periphery support 60 has a conical surface 601 and a groove 602. After the bottom A of the outer periphery of the cup body 2 contacts the conical surface 601, the dome pressing tool 70 is pressed down further. As a result, the metal of the inclined portion S of the cup body 2 is subjected to compressive stress and is guided and pressed into the groove 602.

[0081] Furthermore, the cup dome D is pressed down to become a second height Hp, which is lower than the first height Ho. Simultaneously, using the upper mold forming member (dome pressing tool 70) and the lower mold forming member (cup outer peripheral support 60), the compressive stress in the meridional direction is... and circumferential compressive stress σ θIt acts on the inclined portion S.

[0082] It should be noted that, Figure 7 This is a schematic diagram illustrating the compressive stress imparted when the inclined portion S is formed as the upright portion 20d in this embodiment. That is, when the inclined portion S is pressed into the groove 602 of the lower die forming member, the compressive stress in the meridional direction is due to the pressing force of the dome pressing tool 70. The circumferential compressive stress σ generated by the radially inward movement of the component conforming to the lower die forming part. θ Simultaneously acting on the inclined portion S, the thickness of the metal material at the inclined portion S increases ( Figure 7 The arrow direction σ ψ ).

[0083] Thus, after the second forming process, a seamless tank body 1 is obtained.

[0084] At the end of the forming process, simply raise the dome pressing tool relative to the outside of the cup to remove the seamless can 1 from the cup outer peripheral support 60.

[0085] Here, the seamless tank 1 obtained after the second forming process is preferably the seamless tank 1 described in this embodiment.

[0086] That is, as a seamless tank obtained after the second forming process, such as Figure 1 As shown, it has an outer peripheral bottom 20a and a circumferential grounding portion 20b.

[0087] It should be noted that the second forming process preferably has the following characteristics.

[0088] That is, in the second forming process, the cup body 2 is pressed into the lower mold forming member (cup outer peripheral support 60) of the second forming process, thereby forming the inclined part S as a circumferential grounding part 20b located inside the outer peripheral bottom 20a, an inner end 20c located inside the circumferential grounding part 20b, and an upright part 20d that rises upward from the inner end 20c.

[0089] Furthermore, in this second forming process, an annular groove protruding outward toward the tank body axis is formed such that the inner diameter of the connection point (outermost end 20e) between the upright portion 20d and the dome 20f of the seamless tank body 1 is larger than the inner diameter of the inner end 20c. In other words, as shown in the figure, near the outermost end 20e, in the cross-sectional view, it approximately becomes... or shape.

[0090] Previously, there were improved forming methods (bottom improvement processing) that used rotating rollers and multi-die molding to form the aforementioned annular grooves. However, in the previous methods, the processed area tended to become thinner, making it difficult to form a groove that was deep enough.

[0091] In contrast, according to the method shown in this embodiment, the plate thickness of the annular groove tends to increase rather than decrease, and a deep groove can be formed naturally.

[0092] In the seamless can manufacturing method of this embodiment, the shape and length of the upper part of the bottom A of the outer periphery of the cup body 2 are not changed between the first forming step and the second forming step.

[0093] That is, when the cup body 2 is placed on the outer peripheral support 60, the lowest point in the Z-axis direction of the surface where the bottom A of the outer periphery of the cup body 2 contacts the conical surface 601 of the outer peripheral support 60 is designated as point T. The position of point T remains unchanged as the dome pressing tool 70 descends and the dome D of the cup is pressed down. (Refer to...) Figure 6 )

[0094] On the other hand, through the second forming process, the portion of the cup body 2 that serves as the inclined portion S is formed into a part of the outer peripheral bottom 20a of the seamless can body 1, a circumferential grounding portion 20b, an inner end portion 20c, and an upright portion 20d (also refer to appropriately). Figure 2 (etc.). That is, the inclined part S of the cup body 2 eventually enters the groove 602 of the outer peripheral support 60 of the cup.

[0095] It should be noted that in this second forming process, there is no significant sliding between the cup body 2 and the upper and lower molds. Therefore, no damage will occur to the metal surface of the cup body 2, and of course, no lubricant is required.

[0096] In addition, the thickness t0 of the raw plate (blank) can be any thickness that is usually used to manufacture seamless tanks. Depending on the application, a metal plate with a thickness of approximately t0 = 0.15 mm to 0.4 mm can be punched and used as the raw plate (blank), but it is not limited to the above thickness.

[0097] [Surface Coating Process]

[0098] As the base plate, when using a metal plate without an organic coating on its surface, such as Figure 4 As shown, in the manufacturing method of the seamless can body of this embodiment, it is preferable to further include an inner surface treatment step (step 2) between the first forming step and the second forming step described above, in which at least the inner surface of the can body 2 is surface coated. Examples of such surface coating treatments include known coatings such as films used on the inner surface of the seamless can body 1.

[0099] Furthermore, on the outer surface side, to ensure transferability and corrosion resistance after the first forming process, an organic coating 40a and 40b can be applied to the area from the bottom A of the outer periphery of the cup to the inclined portion S, centered on the lowest curvature portion of the cup body 2 (refer to...). Figure 8 ).

[0100] That is, in this embodiment, since the forming process involves at least two forming steps and a second forming step, wear on the bottom of the seamless can body is conceivable during the transfer between and after the forming steps. In contrast, for example, by applying the aforementioned organic coating 40 between the first and second forming steps, organic coatings 40a and 40b are formed on the provisional circumferential grounding portion 20a' and the circumferential grounding portion 20b respectively (see...). Figure 8 ).

[0101] Figure 9 This diagram illustrates an example of a coating apparatus capable of applying an organic coating 40 to a portion extending from the bottom A of the outer periphery of the cup to the inclined portion S. As shown in the figure, when the cup body 2 moves horizontally via the conveying mechanism TM, the coating liquid LQ (the liquid that forms the organic coating 40) accumulated in the receiving container SC is applied to the bottom of the cup body 2 via coating rollers R1 and R2. Because a moderately elastic rubber material is used on the surface of roller R2, reliable coating can be achieved on the portion extending from the bottom A of the outer periphery of the cup to the inclined portion S.

[0102] It should be noted that the above-mentioned coating device is an example, and known methods such as spraying the coating liquid LQ onto the bottom of the cup body 2 using a known robot processor can be applied.

[0103] It should be noted that, in addition to the surface coating process described in step 2 above, between the first forming process and the second forming process, the cup body 2 may also undergo appropriate and well-known cleaning processes, printing processes, shaping processes for the cylindrical main body, or necking (drawing) processes within a range that will not cause obstacles to the second forming process.

[0104] According to the seamless tank 1 and its manufacturing method described above, a seamless tank with excellent pressure resistance can be achieved, and the requirements of lightweight and pressure resistance of the tank bottom can be met simultaneously in a high-dimensional way.

[0105] Experimental Example

[0106] Reference Figure 10 The following are experimental examples implemented based on the above-described method. However, the present invention is not limited to the following experimental examples.

[0107] First, as the metal raw material (precursor 3), aluminum alloy plates (JIS H 4000 A3104-H19 material) with thicknesses of 0.200mm, 0.205mm, 0.215mm, 0.225mm, 0.240mm, 0.245mm, and 0.250mm are prepared. The first forming process, surface treatment process, and second forming process described above are then performed to manufacture a can with an internal volume of 350mL and a diameter of 211D (outer diameter). The following experimental examples 1-19 describe different bottom specifications for drawn thin-film cans (DI cans), i.e. seamless cans 1.

[0108] For the various seamless tanks 1 and two commercially available products obtained, the contour of the outer surface through which the centerline of the tank passes was measured using the aforementioned shape measuring machine (Tokyo Seimitsu Co., Ltd., trade name: CONTOURECORD, model 1600DH). The obtained shape data was transferred to CAD, and the outer surface area A, including the aforementioned outer surface area, was calculated. D The area A of the imaginary plane with the circumferential grounding portion 20b as its outline. B The volume V of the space enclosed by the imaginary plane VP and the rising bottom 30. D and the volume V of the metal component (aluminum alloy in this example) forming the rising bottom 30. M Various parameters, including those included.

[0109] In addition, a pressure resistance test was performed on the seamless tank 1 obtained in this way. Regarding the pressure resistance, the test was conducted by sealing the opening of the tank with a perforated plate and then passing a tube through the perforation to introduce pressurized water into the tank. Regarding the pressure resistance (bending pressure) evaluation, as long as it is suitable for use in carbonated beverages, pressure resistance exceeding 0.686 MPa was rated as "○", and pressure resistance below that was rated as "×".

[0110] Starting from the intention of reducing the amount of material needed for can manufacturing, the focus is on the metal volume V of the rising bottom as a measure of the material used at the bottom of the can. M It will be less than 615mm 3 V M The rating is "○", and the above V values ​​are... M The rating is "×".

[0111] To evaluate the volume V at the bottom 30 of the rise. D The disadvantage of excessively large containers leading to reduced capacity is addressed by focusing on the volume V at the bottom of the rise. D It will be less than 17000mm 3 (=17ml) of V D The rating is "○", and the above V values ​​are... DThe rating is "×". It should be noted that the contents of the seamless container 1 in this experimental example are assumed to be 350ml for one example, and 17ml is equivalent to about 5% of that.

[0112] The overall evaluation of the above evaluation results where "pressure resistance", "material usage" and "capacity reduction" are all "○" is "○". The overall evaluation of the case where there is only one "×" is "×".

[0113] Table 1 shows the specifications (measured values, calculated values) and evaluation results of the seamless tank 1 of Experimental Examples 1 to 19 and two commercially available products.

[0114] Example 1 is an example provided as a basic specification based on the forming method of the present invention. Compared with commercially available cans with a diameter of 211D (approximately 66mm), the ground diameter is roughly the same. Although the raw material plate thickness of 0.225mm is obviously thin-walled, the overall evaluation is "○". Thus, in Example 1, the performance and cost of the can bottom are extremely excellent.

[0115] Experiments 2-5 are experiments that, compared to Experiment 1 above, increased the height H of the bottom rise by 30 degrees. p Examples of changes. To avoid Figure 10 The inner diameter of the outermost end 20e shown The innermost diameter of the inner end 20c Changes were also made in advance, with appropriate increases to the first height Ho (referencing). Figure 5 (c)) take shape.

[0116] Experimental Examples 6-8 are examples of changes made to Experimental Example 1, which reduced the thickness of the raw material plate.

[0117] Experimental Examples 9-11 are examples of changes made by increasing the thickness of the raw material plate compared to Experimental Example 1.

[0118] Experimental Examples 12-15 were performed compared to Experimental Example 1, with the inner diameter of the outermost end increased by 20e. Examples of reduced changes. To avoid raising the bottom by 30 units of height H. p The innermost diameter of the inner end 20c The changes also include pre-emptively and appropriately reducing the formation of the first height Ho.

[0119] Experimental Example 16 was compared to Experimental Example 1, with the inner diameter of the outermost end being 20e. Examples of added changes. To avoid raising the bottom by 30 units of height H. p The innermost diameter of the inner end 20c The changes also involve appropriately increasing the first height Ho in advance to form the ground.

[0120] Experimental Examples 17 and 18 are compared with Experimental Example 16 to determine the inner diameter of the outermost end 20e. Further changes to the radius r of the dome sphere D (Refer to Figure 10 (A slightly larger example, 40mm. This is to avoid raising the bottom height by 30mm.) p The innermost diameter of the inner end 20c The changes also involve pre-emptively and appropriately altering the shape of the first elevation Ho.

[0121] Experimental Example 19 is an example in which the thickness of the raw material plate was reduced to 0.215 mm compared to Experimental Example 4.

[0122] Two types of commercially available products were selected from those currently circulating in the market. The selected products contained carbon dioxide, had a so-called modified bottom forming based on rollers, and were relatively thin-walled and lightweight. These products were then measured and evaluated.

[0123] In the evaluation results of the above experimental examples, the examples with a comprehensive evaluation of "○" are all (A) D / A B The values ​​of ) and (V) D / V M The values ​​of all are within the range specified in the claims of this invention. On the other hand, embodiments rated as "×" are all (A) D / A B The values ​​of ) and (V) D / V M The values ​​of all of them are outside the range specified in the claims of this invention.

[0124] In the experimental examples shown above, the tests were conducted with all tank diameters being 66 mm, but (A) D / A B The values ​​of ) and (V) D / V M The values ​​of all are dimensionless, and the evaluation of pressure resistance and cost is independent of the size of the tank, thus the similarity law holds. That is, the present invention is not limited to the case of a tank diameter of 66mm as described above; the numerical range specified in the present invention can be implemented under various tank diameters, and the same effect as described above can be achieved under such conditions.

[0125] The embodiments described above are examples embodying the spirit of the present invention, and appropriate modifications can be made without departing from the spirit of the present invention. Furthermore, known structures can be added to the seamless tank shown in the embodiments without departing from the spirit of the present invention.

[0126] Industrial applicability

[0127] This invention can be applied to containers requiring excellent pressure resistance, especially to tanks for storing liquids such as beverages and medicines.

[0128] [Table 1]

[0129]

[0130] Explanation of reference numerals in the attached figures

[0131] 1 Seamless tank body

[0132] 2. Cup body

[0133] 3. Precursors

[0134] 4. Drum section

[0135] 10 cylindrical main body

[0136] Bottom of 20 cans

[0137] 60 Lower mold forming component (outer peripheral support of the cup)

[0138] 70 Upper mold forming component (dome pressing tool)

[0139] D cup round top

[0140] S-shaped inclined section

[0141] Hp rises to the bottom 30 (second height)

[0142] Ho (first height) height of the drum section 4

Claims

1. A seamless tank, characterized in that, The seamless tank includes: cylindrical main part; A circumferential grounding portion connected to the lower end of the cylindrical main body; and From the circumferential grounding portion toward the rising bottom connected to the central axis side Let A be the surface area of ​​the outer surface of the rising bottom. D The area of ​​the imaginary plane with the periphery as its outline is defined as A. B The volume of the space enclosed by the imaginary plane and the rising bottom is defined as V. D The volume of the metal component forming the rising bottom is defined as V. M When, satisfy 1.55 ≥ (A D / A B ) ≥1.40, and 25.5≥(V D / V M )≥22.0 The relationship.

2. A method for manufacturing a seamless tank, characterized in that, The method for manufacturing the seamless tank includes: A first forming process involves shaping a metal raw material into a cup body, the cup body having a cylindrical main body, a continuous outer peripheral bottom extending from the lower end of the cylindrical main body, and a bulging portion extending from the outer peripheral bottom toward an opening at a first height; and The bulge is pressed down to a second height that is lower than the first height, forming a second forming process that creates a circumferential grounding portion connected to the lower end of the cylindrical main body and a rising bottom connected from the circumferential grounding portion toward the central axis. Let A be the surface area of ​​the outer surface of the rising bottom. D The area of ​​the imaginary plane with the periphery as its outline is defined as A. B The volume of the space enclosed by the imaginary plane and the rising bottom is defined as V. D The volume of the metal component forming the rising bottom is defined as V. M When, satisfy 1.55 ≥ (A D / A B ) ≥1.40, and 25.5≥(V D / V M )≥22.0 The relationship.

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