TWI888590B - Can lid, can and can lid manufacturing method - Google Patents

Abstract

The subject of the present invention is to improve the pressure resistance while meeting the requirement of further reducing the thickness of the plate by conducting a strict study on the plate thickness. The can lid of the present invention is a can lid having a center plate portion, a plate wall portion, a clamping wall radial portion, a clamping wall portion and a curling portion, wherein when the plate thickness of the center plate portion is set to t1 and the plate thickness of the lower end of the plate wall portion is set to t2, t2>t1.

Description

Can lid, can and can lid manufacturing method

The present invention relates to a can cover and a manufacturing method thereof.

When a metal can filled with beverages is a two-piece can, the contents are sealed by rolling a can lid on the open end of the bottomed cylindrical can body. This can lid is usually a can lid with a left-on pull ring type opening pull ring. After the can body is filled with the contents, the can lid is rolled on the open end of the can body, so it is usually separated from the can body and supplied to the filling place of the contents in a stacked state.

The can cap has a center plate portion on which a pull ring for opening is mounted, and an annular groove portion protruding from the outer edge of the inner tool (sealing roller head) of the crimping machine is inserted on the periphery of the center plate portion. In addition, the can cap has a curling portion on the outer periphery of the annular groove portion for curling and sealing the opening end of the can body (for example, see the following patent document 1).

Moreover, as a structure of this can lid, a plate wall portion is formed as the groove inner wall portion of the annular groove portion, a clamping wall radial portion is formed in the portion from the groove inner wall portion to the groove outer wall portion of the annular groove portion, and a clamping wall portion is formed in the portion from the groove outer wall portion to the curling portion. [Prior technical literature] [Patent literature]

[Patent Document 1] Japanese Patent Publication No. 2019-112143 [Patent Document 2] Japanese Patent Publication No. 3-275443

[The problem the invention is trying to solve]

In order to save material resources and reduce weight, it is required to reduce the plate thickness as much as possible. However, if the plate thickness is reduced, there will be problems with the strength when the pressure inside the tank increases (pressure resistance).

As for the can lid, if the pressure inside the can increases, a force is generated to press the center plate upward. Therefore, when the pressure inside the can increases abnormally, the annular groove portion may protrude upward in the opposite direction, causing the annular groove portion and the center plate portion to protrude upward in an angled state, which is called buckling. In particular, when the contents are carbonated drinks, etc., buckling is likely to occur if the temperature inside the can increases abnormally due to the surrounding environment, etc.

On the other hand, various measures have been studied for the structure of the can lid for improving the pressure resistance strength, such as the prior art shown in the above-mentioned Patent Document 1. However, the measures, like the above-mentioned prior art, only focus on the shape design such as providing the first curved portion and the second curved portion in the clamping wall portion and defining the relationship between the curvature radius of the first curved portion and the curvature radius of the second curved portion, and no strict study has been conducted on the plate thickness.

This invention is proposed to deal with this problem. The subject is to obtain a can lid with high pressure resistance while meeting the requirement of further reducing the thickness of the plate by conducting a strict study on the plate thickness. [Technical means to solve the problem]

In order to solve this problem, the can lid of the present invention has the following structure. A can lid characterized by having a center plate portion, a plate wall portion, a clamping wall radial portion, a clamping wall portion and a curling portion, when the plate thickness of the aforementioned center plate portion is set to t1 and the plate thickness of the lower end of the aforementioned plate wall portion is set to t2, t2＞t1. [Effect of the invention]

A can cover having such a feature can satisfy the requirement of further reducing the plate thickness while having high pressure resistance, thereby achieving improvement in the pressure resistance of the can cover.

In the following description, the same symbols in different figures represent parts with the same functions, and repeated descriptions in each figure are appropriately omitted.

As shown in Fig. 1, the can lid 1 of the embodiment of the present invention comprises a center plate portion 1A, a plate wall portion 1B, a clamping wall radial portion 1C, a clamping wall portion 1D and a curling portion 1E. The center plate portion 1A is a slightly flat portion in the center of the can lid 1, and when it is a retention pull ring type, a notch or an opening pull ring is provided.

There is a curved portion r1 at the outer edge of the center plate portion 1A, and a portion that descends in a straight line from the end of the curved portion r1 becomes the plate wall portion 1B. Furthermore, the curved portion r2 formed below the plate wall portion 1B, that is, the portion including the bottom of the annular groove portion Cs formed on the outer periphery of the center plate portion 1A, is the clamping wall radial portion 1C. Furthermore, a straight line or partially curved portion extending upward from the upper end of the outer side of the clamping wall radial portion 1C, that is, a portion from the outer wall of the aforementioned annular groove portion Cs to before the bend of the curling portion 1E, becomes the clamping wall portion 1D.

In the can lid 1 of the embodiment of the present invention, when the thickness of the center plate 1A is t1 and the thickness of the lower end of the plate wall 1B is t2, t2>t1. The thickness t1 of the center plate 1A is close to the original thickness of the workpiece before the can lid 1 is formed.

The lower end of the plate wall portion 1B is the boundary portion with the bent portion r2 of the clamping wall radial portion 1C. In the can lid 1, by adopting a new method in the forming process of the clamping wall radial portion 1C, the plate thickness t2 of the lower end of the plate wall portion 1B is set to be thicker than the plate thickness t1, and the can lid 1 with high pressure resistance strength based on the known shape design can be obtained. By setting the plate thickness t2 to be thicker than 1.01 times the plate thickness t1 (t2>1.01×t1), the can lid 1 with higher pressure resistance strength can be obtained.

In addition, regarding the can lid 1, when the plate thickness of the clamping wall radial portion 1C is set to t3, by setting the plate thickness t3 to be thicker than the plate thickness t1, preferably to be thicker than 1.01 times the plate thickness t1 (t3>1.01×t1), a can lid 1 with high pressure resistance strength can be obtained.

In addition, regarding the can lid 1, when the plate thickness of the middle portion of the clamping wall portion 1D, that is, the plate thickness at the position where the actual height of the can lid is divided into two parts as shown in FIG1 is set to t4, t1>t4 is established. According to this, by making the middle portion of the clamping wall portion 1D, which has less influence on the pressure resistance strength, thinner, the can lid 1 can be made lighter while maintaining a predetermined pressure resistance strength.

The aforementioned can lid 1 is partially thickened in thickness at the annular groove portion Cs formed on the outer periphery of the center plate portion 1A, the plate wall portion 1B, and the clamping wall radial portion 1C, thereby making the known shape design of the annular groove portion Cs and the portion from there to the curled portion 1E more reasonable and improving the pressure resistance strength.

The aforementioned can lid 1 can set the plate thickness of the annular groove portion Cs formed on the outer periphery of the center plate portion 1A, the plate wall portion 1B, and the clamping wall radial portion 1C to be thicker than the original plate thickness of the workpiece (plate thickness t1 of the center plate portion 1A), thereby being able to make the original plate thickness of the workpiece as thin as possible, thereby being able to effectively achieve material resource saving and weight reduction.

Next, the manufacturing method of the can lid 1 is described. As shown in FIG2 , the manufacturing steps of the can lid 1 include a blank stamping step S1, a peripheral portion drawing step S2, a plate portion drawing step S3, and a plate portion pressing step S4.

In these steps, through step S1 to step S3, the formed body M1 shown in Figure 3 (a) is formed, and in step S4, the lower pressing plate portion p (the processed portion processed on the center plate portion 1A) of the formed body M1 is processed to form the formed bodies M2 and M3 shown in Figures 3 (b) and 3 (c), and finally the can cover 1 shown in Figure 3 (d) is obtained.

Each step is specifically described. In each step, the upper tool U and the lower tool L shown in Figures 4 to 8 are used as processing tools. The upper tool U has an inner tool U1 and an outer tool U2, and the lower tool L has a fixed inner tool L1, a movable inner tool L2, a movable outer tool L3, and a fixed outer tool L4.

In the blank stamping step S1, as shown in FIG4(a), the workpiece M is inserted between the upper tool U and the lower tool L. As shown in FIG4(b), the upper tool U is lowered to stamp the machining surface a of the outer tool U2 and the machining surface b of the fixed outer tool L4 to form a disc-shaped forming body M01.

In the peripheral drawing step S2, the upper tool U is further lowered, as shown in FIG5 (a), the outer peripheral portion of the formed body M02 is clamped by the lower surface c of the outer tool U2 and the upper surface d of the movable outer tool L3, and the outer peripheral portion of the formed body M02 is drawn based on the processing surface e of the movable inner tool L2. The upper tool U is further lowered, as shown in FIG5 (b), and the lower surface c of the outer tool U2 presses down the movable outer tool L3, thereby drawing the formed body M03 by the processing surface f of the outer tool U2 and the processing surface g of the movable inner tool L2.

In the plate portion drawing step S3, as shown in FIG6 (a), the upper tool U is further lowered, and the processing surface h of the outer tool U2 and the processing surface e of the movable inner tool L2 clamp the outer periphery of the formed body M04, and the plate portion p of the formed body M04 abuts against the upper surface of the fixed inner tool L1, thereby performing the drawing process of the plate portion p. In addition, in this state, as shown in FIG6 (b), the upper tool U is further lowered, and the outer periphery of the formed body M05 is clamped while the movable inner tool L2 is pressed down, and at the same time, the lower surface of the inner tool U1 and the upper surface of the fixed inner tool L1 clamp the plate portion p, thereby performing the drawing process of the plate portion p.

Thereafter, in the plate pressing step S4, as shown in FIG. 7 (a), the movable inner tool L2 presses the outer tool U2 while the processing surfaces e and h clamp the outer periphery of the formed body M06, as shown in FIG. 7 (b), the plate portion p of the formed body M06 is pressed downward relative to the outer periphery, thereby forming the formed body M07.

Thereafter, as shown in FIG8 (a), if the aforementioned plate portion p is further pressed downwardly relative to each other, the processed portion processed by the clamping wall radial portion 1C between the plate portion p and the outer peripheral portion of the forming body M08 is pressed into the groove portion j provided between the fixed inner tool U2 and the movable inner tool L2. In this way, the plate wall portion 1B and the clamping wall radial portion 1C are formed. Furthermore, by the relative downward pressure of the plate portion p, the curling portion 1E is formed in the outer peripheral portion clamped by the processed surface e and the processed surface h. In addition, the center plate portion 1A is formed in the plate portion p clamped by the lower surface of the inner tool U1 and the upper surface of the fixed inner tool L1. Afterwards, as shown in FIG8 (b), the upper tool U and the lower tool L are released, and the formed product of the can lid 1 is taken out. Afterwards, although not shown, the outermost peripheral portion of the formed product of the can lid 1 is rolled into a shape suitable for rolling by a known method, and a sealant is applied to the inner surface portion thereof. The plate portion is riveted, scored, and the pull ring is sewn according to the application to complete the can lid.

According to the aforementioned manufacturing steps, the plate portion p, which is the processed portion processed on the center plate portion 1A, is pressed into the groove portion j by pressing down, and the plate wall portion 1B and the clamping wall radial portion 1C are formed, so that the processing surface of the processing tool does not directly contact the plate wall portion 1B and the clamping wall radial portion 1C, and the forming process is performed. In addition, by pressing down the plate portion p, a compressive stress in a direction orthogonal to the plate thickness direction is applied to the processed portion processed on the plate wall portion 1B and the clamping wall radial portion 1C, so that plastic deformation such as an increase in plate thickness occurs.

Furthermore, as a processing tool, a die having a protrusion k1 for thinning processing provided on the fixed inner tool L10 is used as shown in FIG9. Moreover, by thinning the formed body between the inner processing surface k2 of the outer tool U2 of the upper tool U and the protrusion k1 for thinning processing, the middle part of the clamping wall part 1D can be subjected to thinning processing in the aforementioned plate drawing step S3. In this way, if a part of the clamping wall part 1D (especially the central part) is subjected to thinning processing, the plate thickness of a part of the clamping wall part 1D can be thinned. In this way, while meeting the requirements of saving material resources and weight reduction, the pressure resistance strength of the can lid 1 can be effectively improved. In addition, the aforementioned manufacturing steps are a method of performing the process from the stamping of the blank to the formed product of the can lid 1 in one stroke in one upper and lower mold, but the series of steps can also be performed in multiple stages using molds independently. In particular, the compressive stress in the direction perpendicular to the plate thickness direction based on the downward pressing of the plate p in the plate downward pressing step S4 becomes the largest in the state depicted in FIG8 (a), that is, the state where the processed part is pressed into the bottom of the groove part j. Therefore, the downward pressing is divided into multiple stages, and the plate is pressed down each time using a mold with a groove bottom, thereby enabling control to further expand the range of increasing the plate thickness.

[Example] As the workpiece M, a coil coating material in which an outer surface coating of 15 mg/ ^dm2 and an inner surface coating of 100 mg/ ^dm2 are applied to an Al alloy (A5182-H19) with a plate thickness of 0.26 mm is used, and a can lid 1 is formed in the aforementioned manufacturing step, and an example of measuring the plate thickness of each part is shown in the following Table 1. In addition, t5 is the plate thickness of the upper end of the plate wall portion 1B. Here, the outer diameter of the fixed inner tool L1 is φh=51.58 in Example 1, φh=52.18 in Example 2, and φh=51.58 in Example 3, and a thinning process is performed at a thinning rate of about 7% in the middle portion of the clamping wall portion 1D, and the forming is performed in the same manner as in Example 1.

[Table 1] Plate thickness t1 t2 t3 t4 t5 Compressive strength (MPa) Embodiment 1 0.260 0.290 0.271 0.275 0.280 0.752 Embodiment 2 0.260 0.302 0.279 0.285 0.291 0.766 Embodiment 3 0.260 0.307 0.282 0.256 0.301 0.777 Comparative example 0.260 0.242 - 0.258 0.240 0.691

As shown in Table 1, in Example 1, the plate thickness t2 is thicker than 1.01 times the plate thickness t1, and in Example 2, the plate thickness t2 and the plate thickness t3 are thicker than 1.01 times the plate thickness t1. Furthermore, in Example 3, the plate thickness t4 is thinned by thinning, so that the metal portion of the processed portion processed in the plate wall portion 1B and the clamping wall radial portion 1C can be filled accordingly. As a result, the plate thicknesses t2 and t3 can be further thickened by the action of the compressive stress in the direction orthogonal to the plate thickness direction based on the downward pressure of the plate portion p. By adjusting the plate thickness in this way, the pressure resistance strength can be improved compared to the comparative example performed by the conventional method in Patent Document 2.

As described above, the can lid 1 of the embodiment of the present invention can satisfy the requirement of further reducing the plate thickness and has high pressure resistance, thereby improving the pressure resistance of the can lid 1. The can lid 1 rolled on the can body can ensure high pressure resistance while reducing the weight of the metal can relative to the weight of the contents.

The embodiments of the present invention are described in detail with reference to the drawings, but the specific configuration is not limited to the embodiments. Even if there are design changes that do not deviate from the scope of the purpose of the present invention, they are also included in the present invention. In addition, as long as there are no special contradictions or problems in the purpose and configuration of the above-mentioned embodiments, the techniques of each other can be used and combined. For example, the can lid 1 with a cross-sectional shape as shown in FIG. 10 shown in patent document 1 can also be combined with the present invention.

FIG. 11 is a diagram showing the measurement position of the plate thickness in the middle portion of the clamping wall portion, FIG. 11(a) is a diagram showing the measurement position of another embodiment of FIG. 10, and FIG. 11(b) is a diagram showing the measurement position of the embodiment. In either case of FIG. 11(a) or FIG. 11(b), when the plate thickness in the middle portion of the clamping wall portion 1D of the can lid 1, that is, the plate thickness at the position where the actual height of the can lid is divided into two parts is set to t4, t1>t4 is achieved. In another embodiment, by thinning the middle portion of the clamping wall portion 1D, which has less influence on the pressure resistance strength, the can lid 1 can be made lighter while maintaining the prescribed pressure resistance strength. In addition, another embodiment of FIG. 11 (a) and another embodiment of FIG. 11 (b) respectively show a partial cross section of a portion of the can lid 1 of FIG. 10 and a portion of the can lid 1 of FIG. 1 after being rolled onto the can body. Comparing the states of FIG. 10 and FIG. 1 before rolling with the states of FIG. 11 after rolling, no change in the actual height before and after rolling of the can lid 1 is found, so the plate thickness t4 of another embodiment of FIG. 11 (a) and the embodiment of FIG. 11 (b) is approximately at the same position.

1: Can lid 1A: Center plate 1B: Plate wall 1C: Clamping wall radial part 1D: Clamping wall 1E: Curled part Cs: Annular groove r1: Bend part r2: Bend part t1: Plate thickness of center plate t2: Plate thickness of lower end of plate wall t3: Plate thickness of clamping wall radial part t4: Plate thickness of middle part of clamping wall t5: Plate thickness of upper end of plate wall U: Upper tool L: Lower tool p: Plate part

FIG1 is an explanatory diagram showing a partial cross section of a can lid. FIG2 is an explanatory diagram showing the manufacturing steps of the can lid. FIG3 is an explanatory diagram showing a formed body in the manufacturing steps (FIG3 (a) is a formed body formed by steps S1 to S3, FIG3 (b) and FIG3 (c) are formed bodies formed by step S4, and FIG3 (d) is the final can lid). FIG4 is an explanatory diagram showing a blank stamping step (FIG4 (a) is before stamping, and FIG4 (b) is after stamping). FIG5 is an explanatory diagram of a peripheral drawing step (FIG5 (a) is in the middle of drawing, and FIG5 (b) is after drawing). FIG. 6 is an explanatory diagram of the plate drawing step (FIG. 6 (a) is when the drawing starts, and FIG. 6 (b) is when the drawing is completed). FIG. 7 is an explanatory diagram of the plate pressing step (FIG. 7 (a) is when the pressing starts, and FIG. 7 (b) is when the pressing is in the middle). FIG. 8 is an explanatory diagram of the plate pressing step (FIG. 8 (a) is when the pressing is completed, and FIG. 8 (b) is when the formed product is taken out). FIG. 9 is an explanatory diagram showing an example of applying ironing processing in the plate drawing step. FIG. 10 is an explanatory diagram showing an example of another shape of the embodiment of the present invention. FIG. 11 is a diagram showing the measurement position of the plate thickness in the middle portion of the clamping wall portion (FIG. 11(a) is a diagram showing the measurement position of another embodiment of FIG. 10, and FIG. 11(b) is a diagram showing the measurement position of the embodiment).

1:Can lid

1A: Center panel

1B:Board wall part

1C: Clamp the radial part of the wall

1D: Clamp the wall

1E: Curl

Cs: Annular groove

r1: curved part

r2: curved part

t1: Thickness of the center plate

t2: Plate thickness at the lower end of the plate wall part

t3: Plate thickness of the clamping wall radial part

t4: Plate thickness of the middle part of the clamping wall

t5: Plate thickness at the upper end of the plate wall part

Claims (8)

A can lid is characterized by having a center plate portion, a plate wall portion, a clamping wall radial portion, a clamping wall portion, and a curling portion, and when the plate thickness of the center plate portion is set to t1 and the plate thickness of the lower end of the plate wall portion is set to t2, t2＞t1. For example, the can lid of claim 1, wherein when the plate thickness of the aforementioned center plate portion is set to t1 and the plate thickness of the lower end of the aforementioned plate wall portion is set to t2, t2＞1.01×t1. For example, the can lid of claim 1 or 2, wherein when the plate thickness of the radial portion of the clamping wall is set to t3, t3＞1.01×t1. The can lid of claim 1 or 2, wherein when the plate thickness of the middle portion of the clamping wall is set to t4, t1＞t4. As in claim 3, the can lid, wherein when the plate thickness of the middle portion of the clamping wall portion is set to t4, t1＞t4. A can using the can lid as claimed in any one of claims 1 to 5. A method for manufacturing a can lid, characterized in that it is a method for manufacturing a can lid as in any one of claims 1 to 5, and the clamping wall radial portion is formed by relatively pressing down the processed portion to be processed into the center plate portion. A method for manufacturing a can lid as claimed in claim 7, wherein a thinning process is applied to a portion of the clamping wall portion.