JPH06127547A - Metallic lid of can - Google Patents

Abstract

PURPOSE:To prevent breakage from a score line part even if a pressure in a can is high by forming a small bead at a specific position wherein remaining score thickness is formed extremely thin so that a part to be opened can be easily opened at the time of pulling up a tab by a finger. CONSTITUTION:Small beads 28a, 28b on a tab side are provided through a center of, a rivet part 20 at positions of 30 to 40 degrees on both sides from a center line I-I dividing a center plate 14 into a tab 22 side and a score 18 side, while small beads 28c, 28d on a score are provided at positions of 35 to 45 degrees from the center line I-I, respectively. Therefore a plurality of these angled sharp-headed parts are provided at the farthest position from a score line 16, so that the sharp-headed parts may not extend to the score line part 16, preventing an excessive load from being applied to the score line 16 part. As a result, even if a pressure caused by making angles is similar to that for a conventional can, the angles are not made in the vicinity of the score line 16, so that breakage at the score line 16 part may not easily occur.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a metal lid for a can, and more particularly to a structure of a metal lid for improving the burst strength at the opening score line.

[0002]

2. Description of the Related Art At present, in metal lids of cans, particularly lids of beverage cans, a predetermined opening portion surrounded by score lines formed from the central side to the outer peripheral side of the central plate portion of the lid is formed. By pulling up the tab fixed to a part of the opening planned part or on the outside thereof, the planned opening part is pulled upward from the lid body, or the planned opening part is pushed into the can to open the opening in a part of the lid. The EOE (Easy Open End) type to be formed is widely used. Here, in the EOE type can lid, the tab is usually pulled up by a finger, and the planned opening portion is separated from the central plate portion along a score line formed around the planned opening portion. Therefore, the remaining thickness of the can lid on the score line must be thin so that the planned opening portion can be easily separated from the central plate portion by the force of the finger pulling up the tab.

When the content of the can is a carbonated beverage or the like, the internal pressure of the can becomes extremely high if the can is vibrated by transportation or left in a high temperature place for a long time.

For this reason, if the remaining score thickness is made extremely thin, the score line may burst due to the extremely high internal pressure of the can, and the contents may be ejected.

On the other hand, if the remaining score thickness is increased so as to withstand a high internal pressure of the can, there remains a problem that the planned opening portion cannot be easily separated by the force of the finger.

Therefore, various improvements have been made in the past (Japanese Patent Publication No. 52-21984, Japanese Patent Laid-Open No. 51-4).
6272, actual development 61-141147, actual development 62-1
32927, Actual Development Sho 62-3428, Actual Public Sho 50-39
311, JP-A-58-171339, JP-A-60-90
132, JP-A-64-45250, JP-A-64-452
51).

When these means are roughly classified, one means is to form a buffer portion for increasing the internal volume of the can when the internal pressure of the can is increased, and the other means is to improve the pressure resistance of the can. .

[0008]

However, even with the above-mentioned various improvements, it was observed that the score line was broken and the contents spouted when the internal pressure of the can rapidly increased.

That is, as a result of the present inventor's research on the rupture phenomenon of the can opening (score line portion), a "corner" in which a part of the central plate portion of the can lid surface protrudes outward in a pointed shape prior to the rupture. It was clarified that the "bulging" was observed, and when the pointed portion of the bulging was applied to the score line portion, an excessive load was applied, resulting in score line rupture.

Therefore, even when the buffer portion for releasing the pressure is formed so as to make the cornering less likely to occur and the lid is improved in the cornering resistance, the can of the can can be improved. There was a limit to the volume expansion allowance and pressure resistance improvement from the viewpoints of dimensions, securing the filling amount of contents, moldability, and saving of used materials. In this case, stress concentrates on the score line portion with the weakest strength in the lid, and the score line portion is bulged, leading to score line rupture.

The present invention has been made in view of the above-mentioned problems of the prior art, and an object thereof is to make an EOE type metal having a planned opening portion surrounded by a score line in a part of a central plate portion. To prevent the rupture from the score line part even if the internal pressure of the can becomes extremely high while forming the remaining thickness of the score very thin so that the planned opening part will be opened easily when pulling up the tab with your finger. It is in.

[0012]

In order to solve the above-mentioned problems, in the metal lid of the can of the present invention, a part of the central plate portion of the can lid projects outwardly in a pointed shape before the score line ruptures. A small bead portion that is likely to cause cornering is formed in advance so that the cornering phenomenon described above intentionally occurs at a specific position of the central plate portion that is distant from the score line.

That is, a flange portion provided on the outer periphery for engaging with the opening edge of the can, a central plate portion surrounded by the flange portion, and a central plate portion from the center side to the outer peripheral side are carved. Of a can having a predetermined opening portion surrounded by a score line and a tab fixed to the center of the central plate portion by a rivet portion, most of which is arranged outside the predetermined opening portion. In a metal lid, at least a pair of tabs sandwiching the tab at the edge of the central plate portion on the tab side, with a center line passing through the central portion of the rivet portion and dividing the central plate portion into a tab side and a score side. Side small beads, and at least a pair of score small beads sandwiching the planned opening portion at the edge of the center plate on the score side, and the tab small beads are located on the left and right sides of the center line. At 30 to 40 degrees, The score side small bead portions, characterized in that provided at positions of 35 degrees to 45 degrees from the center line.

[0014]

[Function] When the can contents are carbonated drinks, etc., and when the internal pressure of the can becomes extremely high due to temperature rise or vibration, stress concentrates on the tab-side small beads and score-side small beads where the strength is weakest. However, due to the pressure inside the can, it projects outwardly in a pointed shape, which is called "horning".
Occurs.

However, the tab side small bead portion passes through the center of the rivet portion, and is located at a position of 30 to 40 degrees to the left and right from the center line that divides the center plate portion into the tab side and the score side, and the score side. The small bead portion is 35 degrees to 4 degrees from the center line.
Since they are provided at the positions of 5 degrees, respectively, a plurality of cusp-shaped points of this corner are generated at the position farthest from the score line portion. Therefore, the pointed portions do not reach the score line portion. Do not overload the score line.

As a result, although the pressure that causes cornering is equal to or even lower than that of the conventional can lid, cornering does not occur in the vicinity of the score line, so that rupture in the score line is extremely unlikely to occur. It will be.

In order to guide the cornering, it is necessary to form the bead portion only at a very limited position on the lid, and when it is formed at a portion other than this, it is rather ruptured at the score line portion. It may also occur easily.

[0018]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described below with reference to the drawings.

First, the structure will be described.

FIG. 1 shows a schematic configuration diagram of a metal lid according to an embodiment of the present invention. FIG. 1 (A) is a plan view of the outer surface and FIG. 1 (B) is the same. FIG. 11 is a cross-sectional view taken along the line I-I of FIG. (A), and FIG. (C) is a plan view showing the shape of the planned opening portion and the position of the rivet portion provided on the metal lid. Note that the details of the portion circled in FIG. 1 (B) are shown in FIG. 2 (A).

In the lid 10 shown in FIG. 1, a flange portion 12 is formed on the outer periphery of the lid 10, and a central plate portion 14 is formed inside the flange portion 12 and surrounded by the flange portion 12.

A score line 16 is formed in a part of the central plate portion 14 from the substantially central portion toward the outer peripheral direction.
Due to this, the part surrounded by the part is the planned opening part 18. The tab 22 is fixed to the lid 10 by a rivet portion 20 formed so as to project from the inside to the outside of the lid 10 at a position near the outside of the planned opening portion 18 and substantially at the center position of the lid 10.

Further, the tab 22 has a planned opening portion 18 at one end.
To the upper region of the central plate portion 14, and the other end extends to the vicinity of the edge of the central plate portion 14, and the other end is provided with a finger locking portion 24 for locking a finger or the like when pulling up the tab 22 upward. Has been formed. Further, the central plate portion 14 is formed with a dent panel portion 26 having a slight step so as to frame the planned opening portion 18 and the tab 22.

Therefore, by pulling up the finger engaging portion 24, the lever action is initially performed with one end of the tab 22 on the planned opening portion 18 as a fulcrum and the rivet portion 20 as an action point.
Next, the score line 16 portion around the planned opening portion 18 is broken by a lever action using one end of the tab 22 as an action point and the rivet portion 20 as a fulcrum, and the planned opening portion 18 is pushed down to be opened (so-called. Steion tab type.)

A feature of this embodiment is that a small bead portion 28, which is a minute depression, is formed at the edge portion of the central plate portion 14 surrounded by the flange portion 12.

That is, as shown in FIG. 2A, the tab 22 is formed at the edge of the tab 22 on the finger engaging portion 24 side (hereinafter referred to as the tab side) with the line I-I passing through the center of the rivet portion 20 as a boundary. 2 tab-side small bead portions 28a and 28b are formed, and two score-side small bead portions 28c and 28d are formed at the edge of the planned opening portion 18 side (score side) with the planned opening portion 18 sandwiched therebetween. There is.

Here, the bead portion 28 is formed as shown in FIG. That is, as shown in FIG. 2A, the bead portion 28 is pressed by the punch 50 to be formed into a concave shape having a depth of about 0.4 mm. In addition,
The vertical section of the punch tip has a radius R =
The bead width is about 1.5 mm because it is formed in a semicircular shape of about 0.9 mm.

Next, the operation will be described.

[Setting of convex R portion] E as in the lid 10
The OE type lid is mainly used for beverage cans, but when the contents of the beverage can are carbonated drinks, etc., the temperature inside the carbonated drink rises or the pressure in the can greatly increases when vibration is applied. Get higher Further, if the score residual thickness is increased, the score burst strength is increased, but in order to open the planned opening portion 18 by separating the score line so as to pull up the tab 22 with a finger or the like, the score residual thickness is 95 μm to 125 μm. Is preferred.

Therefore, the remaining score thickness is 95 μm to 125 μm.
m and using the conventional lid in which the small bead portion 28 is not formed, various curvatures (radius mm) of the convex R portion 29 provided around the central plate portion 14 shown in FIG. The burst strength of the score and the pressure at which the score was changed were measured.

Table 1 shows the details of the sample lids used for the experiment, and Table 2 shows the measurement results of the respective sample lids. In addition, the measurement points P, Q, and
R and S are locations shown in FIG.

[0032]

[Table 1]

[0033]

[Table 2]

As is clear from Table 2, the convex R portion 2
It is understood that when 9 is smoothed from 0.38 mm in the conventional half circumference to 0.45 mm in the half circumference and 0.70 mm in the entire circumference, the score burst strength becomes high, which is preferable, but the score burst strength is 8. It has not reached 0 kg / cm ² .

[Position setting of small bead portion] Then, the score burst strength and the cornering pressure of the lid 10 according to this embodiment in which the small bead portion 28 is formed on the sample lid shown in Table 1 were measured. .

Here, in the step of forming the small bead portion 28, the four small bead portions 28a, 28b, shown in FIG.
The formation position of 28c and 28d was variously changed, the score burst strength was measured, and the suitable formation position was examined.

First, with the I-I line passing through the center of the rivet portion shown in FIG. 1 as the center line, the tab side small beads 28a, 2 are formed.
8b and the small beads on the score side 28c and 28d were formed at the target positions. That is, the angle i ₁ formed by each line connecting the centers of the tab-side small bead portions 28a and 28b and the rivet portion 20 and the line I-I, and the score-side small bead portions 28c and 28.
An angle i ₂ formed by each line connecting d and the center of the rivet portion 20 and the line I-I is the same.

FIG. 3 shows the score burst strength and the blasting pressure depending on the changes in the angles i ₁ and i ₂ . Note that the angle 0 in FIG. 3 indicates the score burst strength and the squeezing pressure when the small bead portion is provided on the line II of FIG.

As is clear from the figure, the angles i ₁ ,
No significant effect on the improvement of the score burst strength is observed up to i ₂ of 30 degrees, but it becomes 8.0 kg / cm ² or more at 40 degrees and 45 degrees, and conversely reaches 7.5 kg / cm ² at 50 degrees. And fell.
From the above results, it is understood that the angles i ₁ and i ₂ are preferably around 40 ° to 45 °.

The squeezing pressure is slightly decreased at 40 ° and 45 °, and it is understood that the score rupture strength is improved by inducing the squeezing to a position away from the score line. .

Further, the angle i ₁ and the angle i ₂ were changed independently of each other, and the score burst strength and the squeezing pressure were measured by various combinations. The result is shown in FIG.

As is clear from the figure, the angle i ₁ is 35
It is understood that in terms of degrees, the score burst strength is the highest when the angle i ₂ is 40 degrees, which is preferable.

In Table 3, the tab-side small beat portions 28a and 28b are provided at the angle i ₁ of 35 degrees on the sample lid shown in Table 1 and the score-side small beat portions 28c and 28d are provided at the angle i.
The score rupture strength and the squeezing pressure of the lid 10 in which ₂ is formed at the 40 degree position are shown.

[0044]

[Table 3]

As is clear from Table 3, by forming the small beat portion 28, the score burst strength is about 0.
It improved by 7 to 1.0 kg / cm ² , and score burst strength of 8.0 kg / cm ² or more was obtained in Samples 1 to 3.

Next, the effect will be described.

(1) A planned opening portion 1 surrounded by a score line 16 engraved from the center side to the outer peripheral side of the central plate portion 14.
In the EOE type metal lid 10 having 8 points, the scoring phenomenon in which a part of the central plate portion 14 of the lid 10 projects outward in a pointed shape prior to the rupture of the score line 16, is intentionally scored. Since the small bead portions 28a, 28b, 28c, 28d, which are likely to cause cornering at this specific position, are formed in advance so as to occur at a specific position on the central plate portion 14 away from the tab 16, the tab 22 can be finger-tipped. Even if the pressure inside the can becomes very high due to the temperature rise and vibration of the carbonated drink in the can, the score line 16 is formed so that the remaining score thickness is extremely thin so that the planned opening 18 is easily opened when pulling up with. It is possible to prevent rupture from the part.

(2) A small bead portion 28a, which is different from the conventional lid.
28b, 28c, and 28d are simply formed, so that there is no need to add parts or drastically change the manufacturing line, and it is cost-effective compared to various conventional improvements, but is required for carbonated beverage cans and the like. It is possible to prevent the rupture from the high score line part.

The preferred embodiment of the present invention has been described above with reference to the drawings, but the specific configuration is not limited to the embodiment.

For example, although the embodiment of the can lid in which the planned opening portion is pushed into the can has been shown, it goes without saying that the present invention is also applicable to a can lid in which the planned opening portion is pulled upward from the lid.

Further, the tab-side small beads are provided at positions of 30 to 40 degrees from the center line to the left and right sides, and the score-side small beads are provided at positions of 35 to 45 degrees from the center line. If so, it is included in the present invention.

Further, in the embodiment, the example in which the tab-side small bead portion and the score-side small bead portion are provided in right and left pairs respectively, but a plurality of pairs such as two pairs and three pairs are also included.
When a plurality of pairs of small bead portions are provided, the setting position of at least one small beat portion may be included in the above angle range.

Furthermore, a structure may be provided around the small bead portion so as to promote cornering, or a structure may be provided around the small bead portion to suppress the influence of load on the score line due to cornering.

[0054]

As described above, according to the present invention, the metal lid of the EOE type can having the opening portion surrounded by the score line engraved from the central side to the outer peripheral side of the central plate portion. In the above, the horning phenomenon that a part of the central plate part of the lid that occurs prior to the rupture of the score line due to the increase in the internal pressure of the lid protrudes outward in a pointed shape is intentionally separated from the score line. Since a small bead part that easily causes cornering is formed in advance at this specific position, the score remains so that the planned opening part is easily opened when the tab is pulled up with your finger. It is possible to obtain an effect that it is possible to prevent the rupture from the score line portion even when the internal pressure of the can becomes extremely high while forming the thickness to be extremely thin.

[Brief description of drawings]

FIG. 1 is a schematic configuration diagram of a lid according to an embodiment of the present invention,
FIG. 1A is a plan view of the outer surface, and FIG.
FIG. 1A is a cross-sectional view taken along the line I-I of FIG. 1A, and FIG. 1C is a plan view showing a shape of a planned opening portion provided on a metal lid and a position of a rivet portion.

FIG. 2 is an explanatory view of a beat portion forming state in the present invention,
FIG. 2A is a detailed view of a portion surrounded by a circle in FIG. 1B, and FIG. 2B is an explanatory view of forming a small beat portion.

FIG. 3 is a view showing the lid of the embodiment in which the tab side small bead portion setting angle i ₁
And the score side small bead portion setting angle i ₂ are set to the same angle, and when the angles are changed, a comparative characteristic diagram of score burst strength and squeezing pressure is shown.

FIG. 4 is a view showing the lid of the embodiment, in which the tab side small bead portion setting angle i _{1 is} set.
FIG. 7 is a comparative characteristic diagram of the score burst strength and the squeezing pressure when the and small score side small bead portion setting angles i ₂ are changed.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 Lid 12 Flange part 14 Central plate part 16 Score line 18 Planned opening part 20 Rivet part 22 Tab 24 Finger locking part 26 Dent panel part 28 Small beat part 29 Convex R part

Claims (1)

[Claims] 1. A flange portion provided on an outer periphery for engaging with an opening edge portion of a can, a central plate portion surrounded by the flange portion, and a central plate portion extending from a central side to an outer peripheral side. And a tab that is fixed by a rivet at the approximate center of the center plate and that is mostly arranged outside the planned opening. In a metal lid, at least a pair of tabs sandwiching the tab at the edge of the central plate portion on the tab side, with a center line passing through the central portion of the rivet portion and dividing the central plate portion into a tab side and a score side. A small side bead portion is provided, and at least a pair of small score side bead portions sandwiching the planned opening portion are provided at the edge of the central plate portion on the score side, and the small tab side bead portion is provided on both left and right sides from the center line. To 3
A metal lid for a can, wherein the small bead portion on the score side is provided at a position of 0 to 40 degrees and at a position of 35 to 45 degrees from the center line, respectively.