JP2011184053A - Can lid - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a can lid having a structure that has improved pressure resistant strength for buckling and, at the same time, is made less unlikely to crack even if buckling occurs. <P>SOLUTION: In the can lid, configured such that an annular groove 5 is formed along the peripheral edge of a center panel 2 with the inner side wall 51 of the annular groove 5 connected to the peripheral edge of the center panel 2, and the outer side wall 52 of the annular groove 5 to the basal end of a chuck wall 3, the height of the outer side wall is changed circumferentially so that the outer side wall in the direction in which the material strength is low may be higher than the outer side wall in the direction in which the material strength is high. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to a can lid used for a can container such as a carbonated beverage can, and more particularly, to a can lid having high pressure resistance and capable of preventing the occurrence of cracks when buckling occurs.

  As this type of conventional pressure-resistant can lid, a full-form end is generally used in which an annular groove is formed on the periphery of the center panel so as to protrude opposite to the rising direction of the chuck wall. The inner side wall of the annular groove is connected to the peripheral edge of the center panel, and the outer side wall of the annular groove is connected to the proximal end portion of the chuck wall.

  As a cost reduction measure for such can lids, conventionally, by reducing the center panel diameter and increasing the chuck wall angle, the gauge diameter is reduced by reducing the blank diameter and improving the pressure resistance (minimum internal pressure at which buckling occurs). The thing is known (refer patent document 1).

  However, in order to reduce the blank diameter, it is necessary to newly produce a large part of the mold for forming the can lid, so the cost reduction effect is reduced by the mold production cost.

  Therefore, in order to avoid changing the blank diameter, the chuck unit depth (here, the height dimension from the top back surface of the curl portion of the can lid to the bottom back surface of the annular groove due to the surplus material due to the reduction in the center panel diameter (here In this case, a method of increasing the pressure resistance against buckling and further reducing the gauge can be considered. The height from the bottom back of the annular groove to the connecting portion of the outer side wall with the chuck wall is called the outer side wall height. This height also determines the pressure strength against buckling and is an element related to the occurrence of cracks. Therefore, the determination of the value is important.

  From the above, if the unit depth is simply increased, the pressure resistance is improved, but the problem remains that cracking occurs when buckling occurs.

Japanese Patent No. 3809190

  As a result of diligent research, it was found that the material strength of the lid material was high in the circumferential direction with respect to the rolling direction, buckling occurred in the portion where the material strength was low, and cracks occurred.

  The present invention has been made by paying attention to the fact that the cover material has high and low material strength in the rolling direction, and the direction of the material strength is utilized for improving the pressure strength, and as its method, the material strength is low. An object of the present invention is to provide a can lid that reinforces the portion to increase the overall pressure strength, achieves the required pressure strength with a thinner material, and is less prone to cracking when buckling occurs.

  As the directionality of the material strength shown above, the direction in which the material strength is the lowest is a predetermined angle direction with respect to the rolling direction, and in the direction in which the material strength is low, the pressure resistance is weak and buckling occurs, Become.

Therefore, in the present invention, a method for increasing the pressure strength by reinforcing the direction in which the material strength is weak was sought. As this method, the height of the outer side wall in the direction of low material strength was increased, and the height of the outer side wall in the rolling direction with high material strength and the direction perpendicular to the rolling was increased.
That is, the present invention comprises a center panel, a chuck wall that rises so as to surround the center panel from the periphery of the center panel, and a curling portion for winding that extends radially outward from the tip of the chuck wall, A reinforcing annular groove is formed at the peripheral edge of the center panel, the inner side wall of the annular groove is connected to the peripheral edge of the center panel, and the outer side wall of the annular groove is connected to the base end of the chuck wall. In the can lid of the configuration,
The outer side wall height is changed in the circumferential direction so that the outer side wall height in the direction of low material strength is relatively higher than the outer side wall height in the direction of high material strength.
When the lid is made of an aluminum alloy, the direction in which the material strength is low is 45 ° with respect to the rolling direction.

  This eliminates the occurrence of buckling in the direction of lower material strength, eliminates the decrease in pressure strength due to the occurrence of buckling, and generally increases the pressure strength. Compared to the case where the outer side wall height is constant in the circumferential direction, the pressure resistance is improved, and even with the same plate thickness as before, the pressure strength increases and cracks are less likely to occur. Cost reduction.

FIG. 1 is a can lid of a comparative example of the present invention, (A) is a schematic partial cross-sectional view, (B) is a graph showing the pressure strength when the outer side wall height and unit depth are changed, and x indicates the occurrence of cracks. Show. FIG. 2 is an embodiment of the present invention, (A) is a plan view showing the rolling direction of the lid, (B) is a partially enlarged sectional view in the direction of 45 ° with respect to the rolling direction of (A), and the outer side wall height. (C) is a partially enlarged sectional view in the rolling direction of (A), the outer side wall height is hc, and (D) is a partially enlarged sectional view in the 90 ° direction with respect to the rolling direction of (A). The outer side wall height is hb. FIG. 3 is a view showing the circumferential height of the outer side wall of the present invention, (A) is a view showing the circumferential height change of the outer side wall, and (B) to (D) are (A) of FIG. It is a figure which shows the other structural example of the height change of an outer side wall. 4A-1 and 4A-2 show molding processes of a press that molds a shell, FIG. 4B shows molding processes of a press that molds a curled portion, and FIG. 4C gives changes in the height of the outer side wall. A sectional view of a ring die is shown.

First, a comparative example with the present invention will be described.
FIG. 1A shows a partial cross section of a can lid in the structure of a can lid according to a comparative example of the present invention. However, the embodiment in the present invention is basically the same as the structure of this comparative example. The can lid 1 includes a center panel 2, a chuck wall 3 that rises from the periphery of the center panel 2 to one panel surface side of the center panel 2 so as to surround the center panel 2, and a radially outer side from the tip of the chuck wall 3. And a curling portion 4 for tightening extending in the direction.

An annular groove 5 projecting in the direction opposite to the rising direction of the chuck wall 3 is formed at the peripheral edge of the center panel 2, and the inner side wall 51 of the annular groove 5 is connected to the peripheral edge of the center panel 2. The side wall 52 is connected to the proximal end portion of the chuck wall 3. The inner side wall 51 and the outer side wall 52 are connected by a bottom 53 that is curved in an arc shape. The inner side wall 51 and the outer side wall 52 are constituted by vertical walls orthogonal to the center panel 2. With the above configuration, the pressure resistance is improved by increasing the unit depth H, and the cracks that occur during buckling can be prevented by setting the outer side wall height h within a certain range. In this comparative example, the outer side wall height h is constant in the circumferential direction. Specific examples of dimensions are shown below.

  The can lid of the comparative example has a diameter of 204 made of aluminum alloy, a center panel diameter D1 of 48.5 mm, and four types of unit depth H of 7.00 mm, 7.20 mm, 7.40 mm, and 7.60 mm. With respect to the above, the pressure strength P and the presence / absence of cracks were tested with various changes in the outer side wall height h. The panel depth hp, which is the height from the bottom back surface of the annular groove 5 to the back surface of the center panel, is 2.5 mm, and the plate thickness is 0.235 mm. The test results are shown in FIG.

  As a result of the above test, when the unit depth H is increased, the pressure resistance increases, and even when the outer side wall height h is increased, the pressure resistance increases. However, when the unit depth H is increased, a crack occurs. From the above results, by setting the unit depth H to 7.2 to 7.6 mm and the outer side wall height h to 0.95 mm, it is possible to secure a pressure strength of 650 [kPa] and avoid the occurrence of cracks. I understand.

Next, features of the embodiment of the present invention that are different from the above-described comparative example will be described with reference to FIGS.
The can lid 201 of this embodiment is also made of an aluminum alloy, a center panel 202, a chuck wall 203 that rises from the periphery of the center panel 202 to one panel surface side of the center panel 202, and a chuck wall 203 And a curling portion 204 for tightening extending outward in the radial direction from the distal end portion.

  An annular groove 205 protruding in the direction opposite to the rising direction of the chuck wall 203 is formed at the peripheral edge of the center panel 202, and the inner side wall 251 of the annular groove 205 is connected to the peripheral edge of the center panel 202. The side wall 252 is connected to the proximal end portion of the chuck wall 203. The inner side wall 251 and the outer side wall 252 are connected by a bottom wall 253 that is curved in an arc shape. The inner side wall 251 and the outer side wall 252 are configured by vertical walls orthogonal to the center panel 202.

In the present embodiment, the outer side wall height is changed in the circumferential direction so that the outer side wall height in the direction of low material strength is relatively higher than the outer side wall height in the direction of high material strength. . In the case of an aluminum alloy, the direction in which the material strength is low is 45 ° with respect to the rolling direction.
In FIG. 2A, a line extending in the rolling direction R through the center O of the center panel 202 is defined as a reference line N, and an inclined line inclined 45 ° counterclockwise and clockwise with respect to the reference line N is shown. If the orthogonal line orthogonal to Q1, Q2 and the reference line N is M, the outer side wall height at the intersections A1, A2, A3, A4 with the inclined lines Q1, Q2 is ha, and at the intersections B1, B2 with the orthogonal line M Assuming that the outer side wall height is hb and the outer side wall height at the intersections C1 and C2 with the reference line N is hc, ha>hb> hc is set.
If the phase angles of the intersections C1, C2 with the reference line N of the outer side wall 252 are 0 ° and 180 °, the phase angles of the intersections A1, A2, A3, A4 of the inclined lines Q1, Q2 are 45 °, 135 °, 225 °. The phase angle of the intersection points B1 and B2 with the orthogonal line M is 90 ° and 270 °.

FIG. 3A is a graph schematically showing the change in the outer side wall height in the circumferential direction with the phase angle as the horizontal axis.
That is, the shape changes continuously so that A1, A2, A3, and A4 are the top of the mountain and B1, B2, C1, and C2 are the bottom of the valley. In this figure, the peak portions A1, A2, A3, A4 of the mountain and the bottom portions B1, B2, C1, C2 of the valley have a flat configuration that is constant by a predetermined angle, and the intermediate region has an upwardly convex shape. It has a gentle curve that changes to a concave shape on the way.
However, the top portion and the valley portion do not need to be flat, and may change so as to become the maximum value or the minimum value at one point of each phase angle position, as shown in FIG. .

Further, the outer side wall height ha in the direction of 45 ° with respect to the rolling direction should be the largest, and as shown in FIG. 3D, the outer side wall height hc in the rolling direction and the outer side wall in the direction orthogonal to the rolling direction. The height hb may be the same. That is, it is good also as a relationship of ha> hb = hc.
Although not particularly illustrated, the intermediate strength regions B1 and B2 outer side wall height hb may be lower than the outer side wall height hc of the high strength regions C1 and C2. That is, it may be a relationship of ha>hc> hb, in other words, the outer side wall heights of the four points A1, A2, A3, A4 in the 45 ° direction with respect to the weakest rolling direction need only be highest. .

The lid diameter, the unit depth H, the outer diameter of the outer side wall of the annular groove, and the radius of curvature of the radius part at the tip of the chuck wall are constant in the circumferential direction, and the chuck wall angle α is increased by the change in the outer side wall height. Change.
That is, at the points A1, A2, A3, and A4 in the rolling direction where the outer side wall height ha is high and 45 °, the chuck wall angle α is large, and at the points C1 and C2 in the rolling direction where the outer side wall height is low, the chuck is The wall angle is reduced, and the chuck wall angle α is an intermediate angle at points B1 and B2 where the outer side wall height is perpendicular to the intermediate rolling direction.
The curvature radii of the base end portion of the chuck wall 203 and the connecting portion 203a of the outer side wall need not be the same.

Next, the operation of the can lid of the present embodiment will be described.
Increasing the outer side wall height improves the pressure resistance against buckling, but if it exceeds a certain range, cracks occur when the can lid buckles. It has been found that cracks occur in the direction of low strength of the material in the case of the shell of the can lid before attaching the mouthpiece, in the direction of 45 ° with respect to the rolling direction.
Therefore, in the present invention, the outer side wall height hc below the counter wall in the direction in which the material strength is high (0 ° with respect to the rolling direction) is lengthened in a range in which cracks do not occur, and in the rolling direction in which the material strength is low. On the other hand, the pressure resistance is improved by making the outer side wall height ha in the direction of 45 ° longer than that.

Unless the outer side wall height ha in the direction of weak material strength is set higher than the outer side wall height hc in the direction of high material strength, buckling starts from the portions A1 to A4 where the material strength is weak and cracks occur. . That is, buckling is generated from the direction (C1, C2) in which the material strength is high.
This eliminates the occurrence of buckling in the direction of rolling at 45 ° where the material strength is low, eliminates the decrease in pressure strength caused by the occurrence of buckling, and generally increases the pressure strength. Compared to the method of making the outer side wall height constant in the circumferential direction of the comparative example, since the pressure strength is improved, even with the same plate thickness as before, the pressure strength increases and cracks are less likely to occur, so a thinner plate thickness Since it can be substituted, the cost of the material can be reduced.

As an embodiment of the present invention, a 204-diameter can lid made of an aluminum alloy is prepared, the plate thickness is 0.20 mm, the center panel diameter D1 is 45.3 mm, the unit depth H is 7.5 mm, and the material strength is low. The outer side wall height ha was 1.4 mm, and the outer side wall heights hb and hc in the direction of high material strength were 0.9 mm.
As a comparative example, the pressure strength when the outer side wall height h was constant 0.9 mm was compared.
Example: The pressure strength when ha = 1.4 mm and hb = hc = 0.9 mm is 700 KPa,
Comparative Example: The pressure strength when h = 0.9 mm is constant is 660 KPa,
An improvement in pressure strength of about 5% was recognized. Buckling is part C with high material strength
Although it occurred at 1, C2 or B1, B2, no crack was generated.

Specific dimensions are not limited to this, and the dimensional relationship of the conventional embodiment is applied, and the unit depth H is set to at least 7 mm to 7.6 mm, and the outer side wall height h of the annular groove 305 is set. Further, the outer side wall height hc having a high material strength is set within 0.95 mm, and the outer side wall height hb in the middle portion of the material strength and the outer side wall height ha having a low material strength are set to be larger than hc. Good.
Conversely, the outer side wall height ha having a low material strength may be within 0.95 mm, and the outer side wall height hc having a high material strength may be smaller than ha.
In this way, even if buckling occurs not only in the high-strength portions C1 and C2 but also in the low-strength portions A1 to A4 of the outer side wall, cracks in the low-strength portions are generated. This can prevent the outflow of the contents.

[Molding method]
As in the present embodiment, the following method can be considered as a method for forming can lids having different outer side wall heights in the circumferential direction.
1) Molding at the time of shell molding of can lid (shell molding)
2) Reform after shell formation of can lid 2-1) Molding in a separate process in shell press (curling process, etc.)
2-2) Molded separately by press for reform 2-3) Molded in conversion press However, in 2-2) and 2-3), it is necessary to match the rolling direction of the shell with the tool direction, so the plate material is rolled The method 1) or 2-1) of the shell forming stage flowing in the direction is desirable.

FIG. 4 shows a pressing molding process for molding a can lid score and a shell before rivet molding.
4 (A-1) and (A-2) show a one-stroke molding process of a press for molding a shell, and FIG. 4 (A-1) is a going process, in which most of the shell is molded. FIG. 4 (A-2) returns only the bottom part in the returning step.
That is, as shown in FIG. 4 (A-1), a punch blank 21 is used to punch out a circular blank from a metal plate 20 made of an aluminum alloy, and the blank is squeezed with a ring die 22 and a core punch 23, and a seaming panel corresponding portion 24, An end wall preform 28 having a chuck wall corresponding portion 25, a vertical outer side wall corresponding portion 26 and a center panel corresponding portion 27 is formed. Further, as shown in FIG. 4 (A-2), the central panel corresponding part 27 is raised between the core punch 23 and the cylindrical core die 32, and the vertical inner side wall 13a, bottom wall part 13b and outer side wall 13c are raised. An annular groove 13 having

  The conveyance direction of the aluminum plate used as the material is the winding direction of the aluminum coil, and this conveyance direction is the rolling direction. Therefore, the direction of the ring die may be determined with respect to this conveyance direction.

The ring die 22 has a ring shape, and has an inner peripheral vertical wall 221 and an inclined wall 222 that inclines in a direction of gradually increasing the diameter upward from the upper end of the inner peripheral vertical wall. 4 (C), the upper edge of the inner peripheral vertical wall 221 of the ring die 22 changes in the circumferential direction corresponding to the height change of the outer side wall height as shown in FIG. 3 (A). Let
That is, for the portion corresponding to the low strength region, the inner peripheral vertical wall height La from the bottom surface of the ring die 22 to the upper end of the inner peripheral vertical wall 221 is set to the inner periphery of the portion corresponding to the high strength portion region or the intermediate strength region. This is higher than the vertical wall height Lc. In the figure, the inner peripheral vertical wall height Lc corresponding to the high strength region is illustrated, but the inner peripheral vertical wall height corresponding to the intermediate strength region is the same. Here, the difference between La and Lc is equal to the difference between the outer side wall heights ha and hc in FIGS. 2B and 2D.

  Thus, since the inner peripheral vertical wall height changes in the circumferential direction, the angle with respect to the inclined wall 222 also changes. The content of the angle change described above is equivalent to that the angle α in FIG. 1A changes as the outer side wall height h changes.

  Next, as shown in FIG. 4B, the end portions of the chuck wall corresponding portion 25 and the seaming panel corresponding portion 24 of the end wall preform 28 are placed on the annular die 30, and then curled by the ring punch 31. The portion 17 is formed, and the can lid shell 10 is formed.

In this way, it is only necessary to replace the ring die in the current die set, and the increase in cost can be minimized.
In the present embodiment, not only an aluminum alloy but also various lid materials such as a tin-plated steel plate and a tin-free steel that have a difference in material strength with respect to the rolling direction can be applied. The direction in which the material strength is weak is set according to the material.
In each of the above embodiments, the case where the can lid is circular has been described. However, the can lid is not limited to a circular shape, and may be another shape such as an oval or a rounded quadrilateral.

DESCRIPTION OF SYMBOLS 1 Can lid 2 Center panel 3 Chuck wall 4 Curl part 5 Annular groove 51 Inner side wall part 52 Outer side wall part 53 Bottom part 21 Punch cutter 22 Ring die 221 Inner peripheral vertical wall 222 Inner peripheral inclined wall 23 Core punch 24 Seaming panel corresponding part 25 Chuck wall corresponding part 26 Outer vertical wall corresponding part 27 Center panel corresponding part 28 End wall preform 30 Annular die 31 Ring punch 32 Cylindrical core die 201 Can lid 202 Center panel 203 Chuck wall 204 Curled part 205 Annular groove 251 Inner side wall 252 Outside Side wall 253 Bottom part A1, A2, A3, A4 Part B1, 45 ° direction with respect to rolling direction, B2 Part C1, perpendicular to rolling direction, C2 Part in rolling direction H Unit depth N Reference line M Orthogonal line Q1, Q2 Inclined line O Center R Rolling direction

Claims (2)

A center panel, a chuck wall that rises from the periphery of the center panel so as to surround the center panel, and a curl portion for winding that extends radially outward from the tip of the chuck wall, and the peripheral portion of the center panel Is formed with a reinforcing annular groove, the inner side wall of the annular groove is connected to the peripheral edge of the center panel, and the outer side wall of the annular groove is connected to the base end of the chuck wall,
A can lid characterized in that the outer side wall height is changed in the circumferential direction so that the outer side wall height in the direction of low material strength is relatively higher than the outer side wall height in the direction of high material strength. The can lid according to claim 1, wherein the lid is made of an aluminum alloy, and the direction in which the material strength is low is 45 ° with respect to the rolling direction.

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