JPH0356982B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a can lid used for an easy-open container, and more particularly to a detachable partial easy-open can lid with improved drop impact resistance.

(Prior art) Currently, when opening cans of beverage cans such as beer, youth, and coffee, only a portion of the can lid can be easily removed by hand without using a can opener or other can opening device. So-called tear-off type partial easy-open can lids that can be separated are widely used. Here, FIG. 12 is an external plan view of a typical conventional tear-away type partial easy-open can lid, and FIG. 13 is a drawing illustrating an enlarged plan view of the score line portion in FIG. 12.

In these figures, 1 is the can lid, 2 is the panel part,
Reference numeral 3 indicates a score line which is previously provided on the panel surface with a cross-sectional shape such as an inverted trapezoid by press working, and the portion surrounded by the score line 3 forms a tear opening 6. Furthermore, a rivet portion 4 is provided at one end of the tear opening 6 on the can lid center side, and the rivet portion 4 is formed by bulging the panel surface of the tear opening 6 in advance before scoring. A ring tab 5 is attached to 4 by caulking. The score line 3 has approximately three shape elements, namely, a small semicircular portion 3 around the rivet portion 4.
a, a mostly circular part 3b near the outer periphery of the can lid, and a straight part 3c connecting both ends of these score lines.

The convex grooves 7 formed on the outside along the score line are intended to provide rigidity to the panel, making it easier to open the can, and to prevent the can from reaching the score line if the can is accidentally dropped. The convex groove 7 consists of a straight portion 7a and an arcuate portion 7b. Further, the recessed portion 8 is provided to facilitate finger access to the ring tab 5. Note that in the conventional can lid, the grooves 7a are provided at equal intervals along the score line 3c.

If a can such as a beverage can to which such an easy-open can lid is attached is accidentally dropped, the score portion may be damaged and the contents may leak under adverse conditions such as a large drop. From a material standpoint, steel has a greater tendency to break easily than aluminum, and for this reason aluminum has traditionally been widely used as a material for easy-open can lids. However, due to the high cost of making lids and the corrosion resistance of aluminum to salt-containing foods such as tomato juice and some sports drinks, it is difficult to switch to steel by improving drop impact resistance. This has been strongly requested by related industries.

One way to improve this drop impact resistance is to make the score less likely to break even if the can is dropped by, for example, increasing the thickness of the remaining thickness of the score. The normal can opening operation of pulling up the tab and tearing off the opening piece would significantly deteriorate the opening performance of the can.
Balancing these two characteristics has been considered an extremely difficult problem.

In general, the drop impact resistance deteriorates as the weight of the can increases, and it is significantly inferior in the case of internal pressure cans packed with carbonated drinks or beer, etc., than in the case of non-internal pressure cans packed with fruit juice or the like. One of the reasons why this internal pressure can has poor drop impact resistance is thought to be that the panel portion of the can lid protrudes outward due to the internal pressure.

In response to this problem, in order to respond to the long-standing consumer trust in metal cans, related industries have introduced measures such as the above-mentioned score residual thickness, etc., in order to reduce the score damage caused by falling cans during normal handling to near zero. Strict quality control is applied from all sides. That is, although it varies depending on the weight of the can, etc., this score residual thickness is set to be approximately 50 μm or more in the case of a steel non-internal pressure can. On the other hand, in the case of internal pressure cans, in order to almost eliminate breakage of the score due to dropping of the can during normal handling, the remaining thickness of the score must be approximately 90 μm or more, and in this case, the can opening performance is reduced. It becomes a problem. Therefore, not only is steel not widely used as a material, but even aluminum is currently struggling to find a balance between can openability and drop impact resistance when the weight of the can is large.

As conventional techniques for improving such problems, there are proposals such as US Pat. No. 3,563,199 and U.S. Pat. As shown in Figures 14 and 15, the former is intended to reduce the impact when the can body falls by providing score lines 3 at the bottom of the grooves 9, while the latter is intended to reduce the impact when the can body falls. By making the remaining score thickness of the score line 3a thinner than that of the other score line parts, a balance between initial can opening force and drop impact resistance is achieved. The drop impact resistance proposed by the former is improved by the absorption of impact by the grooves 9 when the can is dropped, but conversely, this impact absorption action inhibits the concentration of stress on the score line when the can is opened. This has a negative effect on can opening performance. In addition, since the part where the score line 3 is engraved is provided at the bottom of the narrow groove 9 formed by two opposing steep slopes, when manufacturing the lid, first the groove 9 is
After processing, the score line 3 must be engraved, which also has the drawback of requiring a complicated processing process. Furthermore, in the latter case, it cannot be said that a fundamental solution to this problem has been provided, considering the relationship between the score remaining thickness and the can openability as described above.

(Problems to be Solved by the Invention) As mentioned above, no essential solution for drop impact resistance that does not impair can opening performance and is easy to implement has yet to be proposed for the can lid of an easy-open can. .

The present invention solves these problems,
The objective is to simultaneously improve the drop impact resistance of easy-open can lids and reduce can opening force.

(Means for solving the problem) In order to solve the problem, the present invention provides the following can lid.

That is, the present invention comprises a hollow rivet 4 bulging near the center of the can lid panel surface 2, an endless score line 3 forming a tear opening 6 containing the rivet, and a rivet crimped to the rivet. In the detachable easy-open can lid 1 comprised of a ring tab 5, an intermediate portion connects both ends of the small semicircular score line 3a around the rivet and the semicircular score line 3b near the outer periphery of the can lid 1. Near the score line 3c, place a line connecting both tip points of the score line 3c at an angle of 15° or more with respect to the reference line of the score line 3c.
This is a tearaway type easy-open can lid with good drop impact resistance, characterized by having a plurality of grooves 7a formed at an angle of 165° or less.

In order to develop such a can lid, the present inventors conducted various investigations into the phenomenon of can body falling.

That is, one of the reasons why the object of the present invention could not be achieved using the conventional techniques was that the phenomenon of can body falling was complex and the governing factors were not clear.
The impact area on the can lid due to a fall of the can body is
The impact location differs for each fall, and therefore the impact this impact has on the score line will also differ each time. This phenomenon occurs when the easy-open can lid is placed downward at a certain height (often 1 m), which is a common measure of drop impact resistance.
This appears as a large variation in the number of falls until the score line breaks when the can body is dropped from the ground. In other words, the main reason for the variation in the number of drops that lead to breakage is considered to be that the impact location differs each time the can is dropped. Therefore, in order to fundamentally solve this problem, it is necessary to clarify the type of impact that causes the score line to break most easily.

Therefore, the present inventors investigated the impact area where the score line is likely to break, that is, the area that can be called the sore spot on the can lid.
was simply modeled and investigated using a method in which the hammer of a Sharpie impact tester was struck at a predetermined position on the can lid. As a result, breakage of the score line due to impact is likely to occur when the impact force is accompanied by bending deformation along the score line (tensile stress perpendicular to the score line). By finding out that the impact to the groove 7a meets this requirement, we have developed a completely new can lid design that improves drop impact resistance as described above.

That is, the present invention is constructed by focusing on providing the grooves 7a at an angle with respect to the score line 3c.

Hereinafter, the present invention will be explained in detail based on the drawings.
FIG. 1 is a plan view showing one embodiment of the can lid according to the present invention, and FIG. 2 is an enlarged plan view of the score line and groove portion in FIG. 1.

In these figures, 1 is a can lid, 2 is a panel portion, 3 is a score line, 4 is a rivet portion, 5 is a ring tab, 6 is a tear opening, 7 is a groove, and 8 is a recessed portion.

In the can lid configured in this way, in the present invention, the small semicircular score line 3 around the rivet is
a and a mostly circular score line 3b near the outer periphery of the can lid.
Two or more grooves 7a are provided in the vicinity of the intermediate score line 3c connecting both ends of the score line 3c, in which a line connecting both tip points of the score line 3c is inclined at an angle of 15° or more with respect to the reference line of the score line 3c. It is something. This groove 7
a is an important component of the present invention, and its purpose is to improve resistance by suppressing the occurrence of bending deformation along the score line (tensile stress perpendicular to the score line) due to the impact when the can body is dropped. The aim is to improve drop impact resistance.

Here, the reason for introducing the above-mentioned reference line to define the inclination angle θ of the groove 7a is that the score line 3c
This is because the curve may not necessarily be straight but may have a curvature. When the score line 3c is linear as shown in FIG. 2, the score line 3c may be treated as a reference line and the inclination angle θ may be determined.

On the other hand, FIG. 3 is a plan view of a can lid illustrating an embodiment of the present invention in which the score line 3c has a curvature. A straight line connecting two points, C ₁ and D ₁ , which are the respective intersections of the perpendicular line drawn from points ₁ and B ₁ to the X-X axis, which is the line of symmetry of the tear opening 6, and the score line 3c. The inclination of the groove 7a with respect to the reference line is defined as an inclination angle θ ₁ . Therefore, when carrying out the present invention, it is necessary to improve the fall strength or to determine the points C ₁ and D ₁ at both ends of the score line portion, and then to adjust the inclination angle θ ₁ by the reverse procedure to the above.
The groove 7a may be provided so as to have an angle of 15° or more.

In addition, when a plurality of grooves are provided on each side of the panel surface 2 with respect to the X-X axis as shown in FIG. 3, for example, when another groove 7a-1 is formed further inside the groove 7a, The inclination angles, that is, θ ₁ and θ ₂ for each groove may be determined in the manner described above.

The reason why the grooves 7a are provided at an inclination angle of 15 degrees or more with respect to the reference line of the score line 3c in the present invention is based on the following experiment.

That is, the present inventors created 10 types of can lids that were the same as shown in FIG. 10 except for the grooves 7a, with different inclination angles θ of the grooves 7a with respect to the linear score line 3c in the range of 0° to 90°. . Here, the adjustment of the inclination angle θ is performed in the 13th step.
Point P on the groove 7a in the figure was set as a center point, that is, a fixed point, and the groove 7a was tilted. Next, according to the Shapey impact test method, a weight of 175g was measured at point P on the groove 7a, and the shape of the striking surface was 8.
When a hammer with mmφ is swung up at an angle of 70° (hammer length 355 mm, head height 21 cm) and falls, the relationship between the number of times the hammer falls until the adjacent score line 3c breaks and the above-mentioned inclination angle θ was determined. FIG. 4 is a drawing explaining this relationship, and the number of times the cans break and fall is expressed as an average value for every 10 cans.

From FIG. 4, it is clear that when the inclination angle θ is less than 15°, the score line is likely to break due to impact. The reason why the score line is easy to break under these conditions is that the grooves 7a restrict the deformation of the panel due to impact and promote the occurrence of bending deformation (tensile stress perpendicular to the score line) in the score line portion along the score line. This is due to a number of reasons.

That is, in the present invention, the purpose of providing the grooves 7a to be inclined at a specific angle with respect to the score line 3c is to suppress bending deformation of the score line along the score line 3c at the time of impact. Therefore, as long as this purpose is met, the number of grooves 7a may be one or more per score line 3c on one side of the opening, and the size and shape, that is, the height,
There are no particular restrictions on the width, length, etc.

Furthermore, in the present invention, the angle of inclination θ of the groove 7a with respect to the reference line is effective in the range of 15° to 90°, as shown in FIG. 4, but for the same reason, the range of 90° to 165° is also effective. It is. Examples of this range are shown in Figures 5 and 6, and in these figures, the above range is shown in Figures 2 and 3.
The angle is shown in the opposite direction from the reference line in the figure. Furthermore, FIG. 7 shows an embodiment in which a plurality of grooves 7a are arranged at an angle of inclination of 90° with respect to the score line 3c.

Note that although the grooves 7a are shown as convex grooves formed by overhanging as described above, in addition to this, concave lines formed by stamping may also be provided. FIG. 8 is a plan view of a can lid illustrating an embodiment of the present invention in such a case, and FIG. 9 is an enlarged sectional view taken along the line - in FIG. According to such a combination, the score line 3 when the protrusion 7a from the panel surface falls from the can body
In addition to preventing direct impact to c, the concave line 7a-2
This facilitates bending deformation of the grooves themselves, so that bending deformation along the score line 7a can be suppressed.

Furthermore, the grooves 7a may not only be linear as described above, but may also be curved. FIG. 10 is a plan view of a can lid illustrating an embodiment of the present invention in which the groove 7a is curved; It is expressed as the angle between the line connecting the points and the reference line (in the case of the figure, it coincides with the score line).

Furthermore, when the grooves 7a are configured with a bent shape or a shape with an extremely small curvature, the angle θ is determined for each shape element. FIG. 11 is a plan view of a can lid illustrating an embodiment of the present invention having such grooves 7a. That is, the groove 7a is configured so that the angle θ ₁ or θ ₂ between the line connecting the tip point A or B of the groove 7a and the apparent tip point F of the shape element and the reference line is a predetermined angle. It is.

In addition, in the present invention, the groove 7a may be connected to the groove 7b in the vicinity of the mostly circular score line 3b, and the point is that the groove 7a is inclined at a specific angle with respect to the reference line of the score line 3c. It is to be established by

Hereinafter, the effects of the present invention will be explained in detail with reference to Examples.

(Example) Rockwell hardness (H _R 30-T) with plate thickness 0.26 mm
Using a tin-plated steel plate equivalent to T-5 with a rating of 66,
Figure 1, Figure 3, Figure 5, Figure 6, Figure 7, Figure 8
10 and 11, and as a comparative example, using an aluminum plate for can lids with a thickness of 0.34 mm in addition to the above-mentioned steel plate, a can lid with grooves 7a according to the present invention is shown in FIG. 12. A conventional can lid having a size 7a was made. The can diameter of these 10 types of can lids is 52 mm (commonly known as 201φ can lid), and the score residual thickness is 80 ± 2 μm (in the case of aluminum plate, the commonly used value is 135 μm ±
5 μm). In addition, the opening force of these 10 types of can lids (mid-term opening force that tears the score line 3c, etc.)
No major differences were observed. Next, using these can lids, the internal pressure of the can filled with cola was 7.5 kg.
f/cm ² , 100 cans each with a total weight of approximately 320gr were made, and these cans were dropped from a height of 1m onto a concrete floor with their lids facing downwards, and the number of falls until the score broke was calculated. The minimum value and average value among 100 cans were measured.

As a result, FIGS. 1, 3, and 5 according to the present invention
The minimum values in Figures 6, 7, 8, 10, and 11 are 2, 4, 2, 4, respectively.
5, 5, 2 and 2 times, the average value is 4.1, respectively.
They were 7.9, 3.8, 8.5, 8.2, 6.9, 4.4 and 4.3 times, but in the case of the steel can lid shown in Figure 12 for comparison, the minimum value was 1 time (that is, the score line was broken on the first drop). , the average value was 3.4 times, and in the case of aluminum can lids, the minimum value was 4 times and the average value was 6.1 times.

From the above, it is clear that the present invention has an effect of improving drop impact resistance, and it was found that even steel can exhibit performance equivalent to or better than conventional aluminum can lids.

(Effects of the Invention) As is clear from the above description, according to the present invention, drop impact resistance can be improved without impairing can opening performance. As a result, it is not only possible to use steel for can lids for internal pressure cans such as beer and cola, for which aluminum has traditionally been widely used, but also for the application of aluminum to can lids for large diameter and heavy cans. This problem can also be solved, and the industrial effect is extremely large.

[Brief explanation of drawings]

FIG. 1 is a plan view of the can lid of the present invention, FIG. 2 is an enlarged plan view of the score line and groove portion in FIG. 1, and FIG. 3 is a plan view of the can lid illustrating an embodiment of the present invention. FIG. 4 is an explanatory diagram showing the relationship between the angle θ between the groove 7a and the linear score line and the drop impact resistance, and FIGS. 5, 6, 7, 8, and 10
Fig. 11 is a plan view of a can lid illustrating another embodiment of the present invention, Fig. 9 is an enlarged sectional view taken along the - line in Fig. 8, and Fig. 12 is an example of a conventional can lid. 13 is an enlarged plan view of the score line and groove portion in FIG. 12, FIG. 14 is a perspective view of the can body with a conventional can lid attached, and FIG. 15 is an enlarged plan view of the score line and groove portion in FIG.
4 is an enlarged cross-sectional view taken along the Z-Z line in FIG. 4. FIG. 1...Can lid, 2...Panel part, 3...Score line, 4...Rivet part, 5...Ring tab, 6...
...Tear opening, 7... Groove, 8... Concave portion, 9...
...concave groove, 10...can body.

Claims (1)

[Claims] 1. A hollow rivet 4 bulging near the center of the can lid panel surface 2, an endless score line 3 forming a tear opening 6 containing the rivet, and a ring tab 5 caulked to the rivet. In the detachable easy-open can lid 1, the can lid has a small semicircular score line 3a around the rivet and a semicircular score line 3 near the outer periphery of the can lid.
In the vicinity of the score line 3c in the middle that connects both ends of the score line 3c, a groove 7a is formed with a line connecting both tip points of the score line 3c at an angle of 15° or more and 165° or less with respect to the reference line of the score line 3c. An easy-open can lid with good drop and impact resistance, characterized by having a plurality of .