JPH0323422B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial Application Field) 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 beverages such as beer, youth, and coffee, only a portion of the can lid can be easily opened by hand without using a can opener or other can opener. So-called tear-off type partial easy-open can lids that can be separated are widely used. Here, FIG. 8 is an external plan view of a typical conventional tear-away type partial easy-open can lid, and FIG. 9 is a drawing illustrating an enlarged plan view of the score line portion in FIG. 8.

In these figures, 1 is a can lid, 2 is a panel part, and 3 is a score line previously provided on the panel surface with a cross-sectional shape such as an inverted trapezoid by press working, and the area surrounded by the score line 3 is The cut portion 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 is formed from roughly three shape elements: a small semicircular part 3a surrounding the rivet part 4, 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. Become.

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 a circular arc portion 7b. Further, the recessed portion 8 is provided to facilitate finger access to the ring tab 5. In addition, in the conventional can lid, the grooves 7a are provided at regular 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. This tendency for the score portion to break easily is greater in steel than in aluminum, and for this reason aluminum has traditionally been widely used as a material for easy-open can lids. However, aluminum is expensive to make and has poor corrosion resistance against salt-containing foods such as tomato juice and some sports drinks.
There has been a strong demand from related industries to switch to steel due to its improved drop impact resistance.

One way to improve this drop impact resistance is to make the score less likely to be damaged 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, this drop impact resistance deteriorates as the weight of the can increases, and is significantly inferior in the case of internal pressure cans packed with carbonated beverages, beer, etc., than in non-internal pressure cans packed with fruit juice, etc. 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 traditional 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 non-internal pressure steel can. On the other hand, in the case of internal pressure cans, the remaining thickness of the score must be approximately 90 μm or more in order to almost eliminate the possibility of score breakage due to dropping of the can body during normal handling, and in this case, the can openability 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 opening performance 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 10 and 11, the former is intended to reduce the impact when the can body falls by providing a score line 3 at the bottom of the groove 9, and the latter is intended to reduce the impact when the can body falls. By making the residual 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 absorbing the impact by the grooves 9 during a fall, but
On the contrary, this impact absorption effect inhibits the concentration of stress on the score line when the can is opened, which has a negative effect on the 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 in view of the relationship between the score remaining thickness and can openability as described above.

(Problems to be Solved by the Invention) As mentioned above, an essential solution to drop impact resistance that does not impair can opening performance and is easy to implement has not yet been proposed for easy-open can lids. do not have.

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 Problems) In order to solve the problems, 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. This easy-open can lid is characterized by having a plurality of protrusions 10 dispersedly arranged on the can lid panel surface 2 close to the score line 3c.

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 area of impact on the can lid due to a fall of the can body will be different for each fall, even if the easy-open can lid is dropped downwards, and therefore the impact of this impact on the score line will be different each time. Become. This phenomenon is a common measure of drop impact resistance, and the score line breaks when the can is dropped from a certain height (often 1m) with the easy-open can lid facing downwards. This appears as a large variation in the number of falls. 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 essentially 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), and the breakage of the score line 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 obtaining the knowledge that impact to the elongated groove 7a falls under this requirement and causes deterioration of drop impact resistance, we developed a completely new can lid design that improves drop impact resistance as described above. This is what led to the development.

That is, the present invention is constructed by paying attention to the fact that the grooves 7 are not formed into an elongated integral shape as in the conventional case, but are formed into a plurality of protrusions, which are distributed and arranged in the vicinity of the score line 3c.

The present invention will be explained in detail below based on the drawings.

FIG. 1 is a plan view showing an embodiment of the can lid according to the present invention, and FIG. 2 is an enlarged sectional view taken along the line - in FIG.

In these figures, 1 is a can lid, 2 is a panel part, 3 is a score line, 4 is a rivet part, 5 is a ring tab, 6 is a tear opening, 7 is a convex groove, 8 is a concave part, and 10 is a protrusion. The shape thereof is a conical shape, a hemispherical shape, etc. in which the shape of the portion 10-A that rises from the panel surface is approximately circular. In the can lid configured in this manner, in the present invention, a plurality of protrusions 10 are provided in a distributed manner on the panel portion 2 near the score line 3c. This protrusion 10 is an important component of the present invention, and its main purpose is to bend the can body into bending deformation along the score line 3c (tensile stress perpendicular to the score line) due to the impact when the can body is dropped.
The objective is to improve drop impact resistance by suppressing the occurrence of. That is, when the protrusions 10 having such a shape are arranged in a distributed manner, the impact force when falling becomes tensile stress in the normal direction of the protrusions 10 and is dispersed in all directions, thereby reducing the tensile stress component perpendicular to the score line. can. On the other hand, in the conventional convex groove 7a as illustrated in FIG. 8, most of the stress components in the normal direction are stress perpendicular to the score line, which adversely affects the drop strength.

The number of protrusions 10 is not limited to one or more per score line 3c on one side of the opening, as long as the gist of the present invention as described above is met, and the size and shape, i.e., size, height, etc. There are no particular restrictions on their arrangement, for example, the spacing between the protrusions constituting the protrusion row, the spacing between the protrusions and the score line 3c, etc., but if these spacings are too large, the effect of improving the fall strength will be impaired. If it is too small, it will be difficult to form a can lid, so in practice it is desirable that the distance between the portion 10-A raised from the panel surface or between this and the score line be 1 to 5 mm.

FIG. 3 shows an embodiment in which the protrusions 10 are arranged in an inclined manner with respect to the score line 3c.

FIG. 4 shows an embodiment in which a plurality of protrusions 10 are arranged along a score line 3c having curvature at positions equidistant therefrom.

FIG. 5 shows an embodiment in which a plurality of protrusions 10 are arranged in series near a score line 3c having curvature.

FIG. 6 shows an embodiment in which the protrusions 10 are spread out and distributed in a planar manner on the panel portion 2 close to the score line 3c.

FIG. 7 shows the panel section 2 near the score line 3c.
2 shows an embodiment in which one relatively large protrusion 10 is arranged for each of the score lines 3c.

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,
Can lids having projections 10 according to the present invention shown in FIGS. 1, 3, 4, 5, 6, and 7, and can lids with a thickness of 0.34 mm in addition to the steel plate described above as a comparative example. Convex grooves 7 in Fig. 8 are made using an aluminum plate for
A conventional can lid having a. The can diameter of these eight types of can lids was 52 mm (commonly known as 201φ can lid), and the score residual thickness was 80 ± 2 μm (135 μm ± 5 μm, which is a common value in the case of aluminum plate). In addition,
No major difference was observed in the can opening force (mid-term can opening force that tears the score line 3c, etc.) of these eight types of can lids. Next, using these can lids, the internal pressure of the can filled with cola was 7.5 Kgf/cm ² , and the total weight of the can was approx.
100 cans of 320gr each were made, and these cans were dropped from a height of 1m onto a concrete floor with their lids facing down, 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 4 according to the present invention
The minimum values in Figs. However, in the case of the steel can lid shown in Figure 8 for comparison, the minimum value was 1 (that is, the score line was broken on the first drop), and the average value was 3.4 times, and in the case of the aluminum can lid, The minimum value is 4 times, the average value is
6. It was heated once.

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, where aluminum has traditionally been widely used, but also for larger-diameter cans.
The problem of applying aluminum to the lids of heavy cans can also be solved, and the industrial effect is extremely large.

[Brief explanation of the drawing]

Fig. 1 is a plan view of the can lid of the present invention, Fig. 2 is an enlarged sectional view of the score line and hemispherical protrusion groove portion in Fig. 1, and Figs. 3 to 7 are other embodiments of the present invention. 8 is a plan view illustrating a conventional can lid, FIG. 9 is an enlarged plan view of the score line and groove portion in FIG. 8, and FIG. 10 is a plan view of a conventional can lid. FIG. 11 is a perspective view of the can body with the lid attached, and is an enlarged sectional view taken along the Z-Z line in FIG. 10. 1...Can lid, 2...Panel part, 3...Score line, 4...Rivet part, 5...Ring tab, 6...
...Tear opening, 7... Convex groove, 8... Concave part, 9
... Concave groove, 10 ... Protrusion, 11 ... 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.
This easy-open can lid has good falling characteristics, characterized in that a plurality of protrusions 10 are distributed and arranged on the can lid panel surface 2 in close proximity to the score line 3c in the middle that connects both ends of the can lid.