JP2001080641A - Easily openable can lid - Google Patents

Abstract

PROBLEM TO BE SOLVED: To restrain the swell of both a can lid and a tab, which is accompanied by the rise of the internal pressure in a can, by effectively absorbing excess thickness caused by the machining for forming a rivet. SOLUTION: An easily openable can lid has an opening piece 8 dividedly formed by an open-shaped score, both ends of which are spaced from each other so as to leave a connected part, at a predetermined position of a panel portion 2, which is located on the outer peripheral side farther than a position of a rivet part 10 caused to protrude accompanying coining. In this can lid, a tab whose push-down end on one side thereof is allowed to position on the opening piece 8 and whose lift end on the other side thereof is allowed to position on the panel portion 2 opposite to the opening piece with the rivet part 10 therebetween is fixed to the panel portion 2 by the rivet part 10 via a bendable tongue part 12 formed at an intermediate portion of the tab. A bead C which allows the panel portion 2 to convexly deform or concavely deform is curvedly formed outside the opening piece 8 and on the outer peripheral side of a coining region along an outer peripheral edge of the coining region.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an easy opening can lid which can be easily opened by a tab, and more particularly to a can used for a positive internal pressure can whose internal pressure after filling contents is higher than atmospheric pressure. It is about the lid.

[0002]

2. Description of the Related Art As a can lid which can be opened with a tab, a stay-ion tab (SOT) type can lid is known. This is a can lid configured to contribute to environmental protection and resource recovery, etc., by leaving a tab for opening the lid and an opening piece cut out by the tab remaining attached to the can lid even after the lid is opened. Specifically, a tab is attached to the can lid by a rivet integrally formed at the center of the upper flat portion (panel portion) of the can lid, and the tab portion of the panel portion, that is, the lower end of the tab, that is, under the depressed end. An opening piece defined by an open score line having ends separated from each other so as to leave a connection portion is formed in a portion located on the side. Therefore, by raising the rear end of the tab, that is, the lifting end, a lever action is generated by the tab to relatively push down the opening piece,
As a result, the score line is broken, the opening piece is pushed into the can, and the opening piece is connected to the panel by the connecting portion where the ends of the score line are separated from each other. .

[0003] Since the above-mentioned tab is attached to the upper surface of the can lid, it becomes a factor of protruding to the upper surface side of the can lid. At the time of handling or transporting cans after filling of contents, tabs are caught by other can lids or guides of the transport route, etc., or situations such as being pushed occur, causing breaks in the score line, Alternatively, there is a case where the direction of the tab is changed so that the opening piece cannot be opened or the tab is removed from the rivet.

When the can lid maintains the flat shape at the time of manufacture, the tab does not protrude above the upper end of the canned portion of the can lid. In a can or the like that is heat-sterilized after filling, the internal pressure increases, so that the central portion of the can lid rises, and this shape may remain as permanent deformation. In such a case, the tab also swells in accordance with the swelling of the central portion, and in the worst case, protrudes above the tightened portion on the outer periphery of the can lid, and the tabs may be transported when the can is transported or sold by a vending machine. It is likely to get stuck and cause trouble. In order to solve such an inconvenience, in the can lid described in Japanese Utility Model Application Laid-Open No. 3-123826, a convex portion that pushes up a portion of the tab on the side of the lifting end (finger portion) from the portion attached to the rivet is used. Even if the central part of the can lid rises due to an increase in internal pressure, it is formed on the panel so that the tab is pushed up to prevent the tab from tilting. As a result, the tip of the tab (pressing end) Does not protrude more than necessary.

[0005] In the can lid described in Japanese Patent Publication No. 6-43001, a part of the periphery of the base of the rivet is subjected to a metal forming process in which the rivet is inclined about 10 degrees to increase the rigidity of the part. As a result, when the internal pressure of the can becomes high, the swelling can be suppressed as compared with the conventional lid.

[0006]

SUMMARY OF THE INVENTION
In the structure described in Japanese Patent No. 23826, the difference between the amount of protrusion at the center of the can lid and the amount of protrusion on the outer peripheral side thereof is eliminated by the convex portion, whereby the inclination of the tab when the internal pressure increases is increased. In addition, it is possible to prevent the tab tip from protruding upward due to this. However,
At the stage where the can lid is not attached to the can body, the end of the tab on the finger hook side is relatively protruded due to the flatness of the can lid and no swelling at the center of the panel. As a result, the end on the finger hook side protrudes upward, which may cause problems such as damaging the inner surface of the other can lid on which the tabs are laminated when handling the can lid. Can occur.

Further, in the structure described in Japanese Patent Publication No. 6-41301, the rigidity of the base of the rivet, that is, the central portion of the panel portion, is increased, so that the can lid when the internal pressure of the can is increased. The swelling can be suppressed. However, since the base of the rivet has been subjected to coining processing for forming the rivet and has been hardened, if the metal forming processing is further performed on that part, cracks and breaks may occur in the rivet base. In addition, the damage of the coined inner protective film is increased, so that at least the degree of metal forming is restricted, and as a result, it is possible to sufficiently prevent the bulging of the panel portion due to an increase in the internal pressure of the can. The configuration was not. Further, when the size of the opening piece defined by the score line is increased in order to increase the opening area, the area of the depression formed in the panel portion increases accordingly, but even if the area of the depression increases, the rivet becomes larger. Alternatively, do not add a rivet to the base of the rivet because it will not increase the base.
It was not enough to suppress the rise of the can lid due to the increase in the panel portion, simply by performing the metal forming process of inclining around 0 degrees to reduce the slack of the metal around the rivet base.

By the way, the rivet for attaching the tab to the can lid is formed by subjecting the panel portion to coining and projecting a part of the panel portion. For this reason, extra thickness (loose metal) is generated around the coined portion, and the amount of the extra thickness depends on the increase in the depressions due to the increase in the openings defined by the score lines. growing. At the same time, the distance from the base of the rivet to the portion where the depression is formed becomes longer than before, so that the absorption performance with respect to the excess thickness is reduced. With the increase in the excess thickness, no special consideration is given to the rise of the rivet portion and the panel portion around the rivet portion when the internal pressure is applied in the above-described conventional structure. At the time of handling or canning after filling the contents, during heating sterilization and transportation, etc., the tab gets stuck and trouble occurs, or the gap between the lower end of the tab and the upper surface of the panel increases. For this reason, there has been a problem that the score line is unexpectedly broken.

SUMMARY OF THE INVENTION The present invention has been made in view of the above technical problem. The present invention absorbs the excess thickness caused by coining to prevent the panel portion from rising due to an increase in internal pressure, and stores canned food. When the corrugated cardboard boxes are transported in pallets in multiple stages and transported, the vibrations during the transportation are applied in the axial direction of the can while biting into the carton of corrugated cardboard. An object of the present invention is to provide an easy-open can lid that can be reliably prevented from being repeatedly transmitted to a remaining portion of a wire and resulting in fatigue fracture caused by the repetitive load, that is, cracking of a score leading to leakage of contents. It is.

[0010]

In order to achieve the above object, according to the first aspect of the present invention, a rivet portion is formed at a center portion of a panel portion, the rivet portion protruding with coining. An opening piece is defined by an open-shaped score line whose both ends are separated at a predetermined position of the panel portion on the outer peripheral side of the rivet portion so that a connecting portion remains, and one of the pushing-down ends is formed on the opening piece. A tab having the other raised end positioned on the panel portion opposite to the opening piece with the rivet portion interposed between the rivet portion and the rivet portion via a bendable tongue piece portion formed at an intermediate portion thereof; In the easy opening can lid fixed to the panel portion by the outside of the opening piece and on the outer peripheral side of the coining region, a bead obtained by deforming the panel portion convexly or concavely, Serial is a can lid, characterized in that it is formed to be curved along the outer peripheral edge of the coining region.

Therefore, according to the first aspect of the present invention, the excess thickness generated in the panel portion by the coining process is absorbed by the bead formed by bending along the outer peripheral edge of the coining region, so that the internal pressure of the can is reduced to the atmospheric pressure. Even when it is used as a can lid for a positive internal pressure can, which is higher, the rise of the rivet portion and the surrounding panel portion due to the internal pressure of the can portion is reduced. Therefore, as the gap between the lower surface of the lower end of the tab and the upper surface of the panel portion becomes smaller than that of the conventional lid, it is possible to prevent the score from being unexpectedly broken due to vibration during transportation of the canned product. Also, it is suppressed that the tab bulges above the can lid more than necessary,
The trouble that the tab gets stuck on the guide member or the like during the heat sterilization treatment step or the transportation of the can can be avoided.

According to a second aspect of the present invention, in addition to the first aspect, the coining area has an annular shape centered on the rivet portion, and the bead is concentric with the coining area. Is a can lid characterized by having an arc shape.

Therefore, in the invention of claim 2,
Since the absorption of the excess thickness caused by the coining process is efficiently performed with a small processing amount, the effect of suppressing the bulging of the panel portion of the can lid is further improved.

Further, according to a third aspect of the present invention, in addition to the configuration of the first or second aspect, the tongue piece of the tab is formed in a recess recessed from an upper surface of an outer peripheral portion of the tab. The bead is formed as a concave bead recessed on the lower surface side opposite to the upper surface on which the tab is attached, within a range in which the concave portion is projected on the panel portion, and the concave amount of the concave bead is set to the concave portion. A can lid characterized in that the amount satisfies a range that does not contact the surface.

Therefore, according to the third aspect of the present invention, since the depression amount of the concave portion in the tab is larger than the concave amount of the concave bead, the same type of can lids are stacked in the same thickness direction (stacked). Case), the bottom surface of the concave bead in the upper can lid is held at a position separated from the surface of the concave portion in the concave portion of the tab in the lower can lid. That is, since they do not touch each other, when the can lids are stacked,
The inner protective coating of the concave bead is prevented from being damaged.

According to a fourth aspect of the present invention, in addition to any one of the first to third aspects, the distance between each end of the bead and the score line is in a range of 0.5 mm to 2.0 mm. A can lid characterized by being set to.

According to the fourth aspect of the present invention, the bead forming is performed without affecting the score line and absorbing damage to the inner protective film of the can lid when absorbing the excess thickness caused by the coining process. Can be. That is, since bead molding is performed after score molding, if the interval between each end of the bead and the score line is less than 0.5 mm, the end of the bead is too close to the score line and the score line is broken. On the other hand, while 2.0
If it exceeds mm, it is necessary to increase the bead depression amount in order to absorb the excess thickness generated by coining,
Therefore, the inner protective film is easily damaged. Therefore, the distance between each end of the bead and the score line is 0.5 mm to 2.
It is set in the range of 0 mm.

According to a fifth aspect of the present invention, in addition to any one of the first to fourth aspects, the panel portion is concavely deformed inside the opening piece and on the outer peripheral side of the coining area. The bead is formed so as to be curved along an outer peripheral edge of the coining region.

Therefore, according to the fifth aspect of the present invention, the excess thickness on one side of the opening around the rivet accompanying the formation of the score line is absorbed by the bead concavely deformed inside the opening. Thereby, it is possible to prevent the shaft of the rivet portion from being tilted due to the excess thickness on one side of the opening. In other words, when the internal pressure of the can rises and the panel swells,
The upper surface of the tab has a small difference in lifting between the lifting end side and the pushing-down end side, and the panel portion can be raised in a state where the tab is kept substantially in a horizontal state. By reducing the gap formed between the rivets, the rivet repetition strength can be improved, and score cracks due to vibration during transportation or the like can be prevented. In addition, since the swelling of the panel portion can be further suppressed, the internal pressure of the can when the upper surface of the tab becomes the same as the upper end of the winding portion, that is, the "bulge pressure" can be improved.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Next, the present invention will be described based on specific examples. FIGS. 1 and 2 show an example of the present invention. An easy opening can lid 1 (hereinafter referred to as a can lid 1) shown here is, for example, a flat plate made of an aluminum alloy having a thickness of 0.235 mm. And a disc-shaped panel portion 2 is formed at the center thereof. As shown in FIG.
2, an outer peripheral groove 3 is formed which is recessed in the depth direction (downward in FIG. 2) from the paper surface and is surrounded by the outer peripheral wall 3a and the inner peripheral wall 3b. The chuck wall 4 extends from the outer circumferential groove 3 toward the front side (upward direction in FIG. 2) of FIG.
The flange curl portion 5 extends through the opening. on the other hand,
A portion (bottom portion of the outer peripheral groove 3) of the annular outer peripheral groove 3 that is continuous with the lower end of the outer peripheral wall 3a is formed in an arc-shaped cross section, and has a curvature radius R of 0.35 mm or more and 0.66 mm or less. The flange / curl portion 5 is wound around the opening edge of a bottomed cylindrical can body (not shown), so that the can lid 1 is fixed to the can body to form a can body.

Further, the panel portion 2 is formed with a recessed portion 6 which is recessed in the depth direction (downward direction in FIG. 2) from the paper surface in FIG. A score line 7 composed of a main score line 7a for breaking and an auxiliary score line 7b for non-breaking is engraved along the periphery of the recessed portion 6 with both ends separated. The portion surrounded by the score line 7 constitutes the opening piece 8. Therefore, a portion between both ends of the score line 7 that are separated from each other is a connecting portion that connects the opening piece 8 to the panel portion 2. further,
The opening piece 8 is formed with a reinforcing bead 9 protruding in the front direction (upward direction in FIG. 2) from the paper surface in FIG.

Further, a rivet 10 is formed substantially at the center of the panel portion 2 and outside the opening piece 8 and adjacent to the score line 7 so as to protrude from the panel portion 2. The tongue 12 extending from the rivet 10 is fixed to the panel 2. One end of the knob piece 11 located on the near side (upper side of the opening piece 8) of the opening piece 8 in FIG. 1 with respect to the paper surface constitutes a pushing-down end 13, and is opposite to the pushing-down end 13 across the rivet 10. The end of the knob 11 on the side is the raised end 1
4.

The outer peripheral portion of the knob piece 11 is bent downward and inward from the upper surface of the knob piece 11 by curl processing, and further bent upward from the inside, and has a curled cross section. A tongue piece 12 is located in a depth direction (downward in FIG. 2) from the upper surface of the outer peripheral portion of the knob piece 11 with respect to the plane of FIG. That is, the recessed portion recessed in the depth direction (downward direction in FIG. 2) from the paper surface in FIG. 1 so that the tongue portion 12 is located below the upper surface of the outer peripheral portion around the rivet 10 in the knob piece 11. A is formed. The knob piece 11 in this embodiment is made of an aluminum alloy and has a thickness of 0.1 mm.
It is formed from a 32 mm flat plate. And the recess A
Is approximately 1.0 mm from the upper surface of the knob piece 11 (preferably,
(0.9 mm to 1.3 mm).

The recess 6 located on the outer peripheral side of the lifting end 14 of the knob piece 11 has a depth of about 1 from the plane of the panel 2 in the direction of the paper of FIG. 1 (downward in FIG. 2). .
A finger hanging recess 15 recessed by 5 mm is provided. The finger-holding concave portion 15 is substantially elliptical, and its short axis substantially coincides with the radial direction of the panel portion 2. The length from the connecting portion between the upper end of the inner peripheral wall 3b of the outer peripheral groove 3 and the panel portion 2 in the radial direction of the panel portion 2 to the outer edge of the finger hooking concave portion 15 is about 1.7 mm (preferably 0.9 mm to 2 mm). .5 mm).

Further, a portion opposite to the opening piece 8 with respect to the rivet 10 and near the outside of a coining area (coining area) B to be coined at the time of rivet processing to be described later, A substantially C-shaped concave bead C which is recessed in the depth direction (downward direction in FIG. 2) from the paper surface in FIG. 1 and concentric with the rivet 10 is formed. This substantially C-shaped concave bead C has a depth of about 0.33 mm (preferably 0.25 mm to 0 mm) in the depth direction (downward direction in FIG. 2) from the plane of the depression 6 with respect to the plane of FIG. .45 mm). That is, the amount of depression is smaller than the amount of depression of the concave portion A. The concave bead C is formed in a range where the concave portion A is projected on the panel portion 2.

In the rivet processing, a coining area B to be coined (coining accompanied by elongation of the material) is performed.
Is determined by the thickness of the metal plate used to form the can lid 1 and the thickness and the rivet shape of the metal plate used to form the knob piece 11. In this embodiment, the center of the panel portion 2 is And the outer diameter is about 6.4 mm.
The rivet hole diameter of the knob piece 11 is about 3.8 mm.

FIG. 3 shows a state in which two can lids 1 are stacked. As shown here, when two can lids 1 are overlapped with their orientations aligned in the thickness direction, the flange / curl portions 5 of adjacent can lids 1 come into contact with each other. That is, the lower end of the flange-curled portion 5 of the upper can lid 1 contacts the upper end of the flange-curled portion 5 of the lower can lid 1. As a result, the knob 11 of the lower can lid 1 does not come into contact with the inner surface of the upper can lid 1. This state does not change even if the lifting end 14 of the knob piece 11 of the lower can lid 1 is at a position (not shown) facing the inner surface of the opening piece 8 of the upper can lid 1.

Further, the position of the finger hooking concave portion 15 which is most deeply depressed is located outside of the lifting end 14 of the knob piece 11 in the radial direction of the can lid 1. You will not be hurt. Further, the position of the substantially C-shaped concave bead C of the upper can lid 1 is located radially inward of the can lid 11 with respect to the concave portion A of the knob piece 11 of the lower can lid 1, and is substantially the same as the upper can lid 1. The depression depth of the C-shaped concave bead C is the knob piece 1 of the can lid 1 of the lower stack.
Since the depth is shallower than the depth of the recess A, the inner surface protective coating of this portion does not come into contact with the knob piece 11 and is not damaged. Therefore, even if the can lids 1 are stacked,
The inner protective film of the upper can lid 1 is not damaged by the knob piece 11. This was confirmed by the following inspection method.

First, the knob piece 1 fixed to the can lid 1
After applying a bright color dye on the surface (top surface) of 1,
The other one of the can lids 1 is stacked on top in the same direction, rotated relatively, and then the inner surface side of the stacked can lids 1 is observed.
Since the dye applied to the knob piece 11 should adhere to the inner surface of the upper layer can lid 1 which is in contact with the knob piece 11 of the lower layer can lid 1, when the can lid 1 is stacked, the knob piece 11 If there is a possibility that the inner protective film may be damaged by contact with the surface, it can be found by this inspection method. In the can lid 1 of this example, since the dye did not adhere to the inner protective film by this inspection method, it was confirmed that the inner protective film of the can lid 1 was not likely to be damaged.

The above-mentioned concave bead C is formed, for example, after the score line 7 is formed and before the tab 11 is attached, as shown in FIG. As a result, the surplus (loose metal) generated by performing the coining process on the coining region B described above is absorbed by the concave bead C formed by the partial deformation of the panel portion 2. Therefore, in the above-mentioned can lid 1, since the concave bead C is formed, when it is wound around a can body and used as a can body, swelling of the can lid 1 due to an increase in internal pressure is suppressed, and at the same time, The lifting of the tab piece (tab) 11 is suppressed. Therefore, it is possible to effectively prevent the load from repeatedly acting on the tab 11 during the can transport after the contents are filled, and the breakage or cracking of the score line 7 accompanying the load. Further, in the can lid 1 described above, by forming the concave bead C, the rigidity of the panel portion 2 is increased. In particular, since the end of the concave bead C is located near the score line 7,
Deformation due to the excess thickness of the panel portion 2 when the lid is opened by lifting the lifting end 14 of the knob piece 11 can be suppressed, and the breaking of the score line 7 can be reliably started and advanced.

In the above specific example, the bead C for absorbing the excess thickness due to coining is formed as a concave bead.
In the present invention, the bead C may be formed as a convex bead. Examples are shown in FIGS. As shown in these drawings, when the convex bead C is formed, the position is formed in the coining area B for rivet forming, as in the above-described specific example, and the work hardening of the coining area B is improved. Since the effect of absorbing excess material is not so much obtained only by further increase, the outer portion of the region B is used, and its shape is an arc along the outer peripheral edge of the coining region B or the rivet 10. Concentric arcs. In addition, a part may be applied to the outer peripheral edge. The distance between both ends and the score line 7 is 0.5 to 2.0 mm, preferably 1.0 to 2.0 mm.
It shall be 1.8 mm. Further, in order to avoid interference with the knob piece 11, a convex bead C is formed so as to coincide with the slit portion S formed on the outer peripheral side of the tongue piece portion 12.
By doing so, interference between the convex bead C and the knob piece 11 does not occur, so that the knob piece 11 is prevented from floating.

Further, according to the present invention, a bead C1 for absorbing excess thickness can be formed also on the opening piece 8 side. Examples thereof are shown in FIGS. 8 to 10. As shown in these figures, the concave bead C1 on the opening piece 8 side is formed outside the coining area B and at a position avoiding the score line 7. ing. The depth of the depression of the concave bead C1 is the same as the knob 1
1, the position of the concave bead C1 is within the range in which the concave portion A is projected on the panel portion 2. Therefore, even when the can lid 1 is overlaid, the concave bead C1 is formed by the knob piece 1 of the lower can lid 1.
1 is avoided, and damage to the protective coating on the inner surface of the can lid is prevented. Thus, by forming the beads C and C1 on both the opening piece 8 side and the opposite side,
The bead C and C1 absorb the surplus in the opening piece 8 due to the formation of the score line 7 in addition to the surplus of the panel part accompanying the coining process. In this case, the swelling of the panel portion 2 and the knob piece 11 due to an increase in the internal pressure is more effectively suppressed. Furthermore, in the above specific example, the present invention can be applied not only to a can lid for a positive internal pressure can but also to a can lid for a negative pressure can which is subjected to heat sterilization.

Next, test examples performed to confirm the effects of the present invention will be described below.

Test Example 1 A 204-diameter lid with a plate thickness of 0.235 mm, a score opening area of 365 mm ² , and tab plate thicknesses of 0.32 mm and 0.30 mm
The bulge pressure and the rivet repetition strength were evaluated for the two types of can lids of mm. Table 1 shows the evaluation results. The remaining thickness of the score near the rivet (near the opening start end) was as shown in Table 1. In addition, the bulge pressure was measured as the pressure at the time when the tab reached the upper end of the tightened portion by increasing the internal pressure of the can body after tightening the can lid around an empty can body. Also,
The rivet repetition strength is set so that a striped fatigue fracture surface called "striation" similar to the fracture surface caused by fatigue during transport can be seen, assuming the fatigue fracture of the score due to vibration during can shipping. It is measured with a rivet repeat strength tester. The rivet repetition strength test is performed according to the following inspection procedure. First, a commercially available cola was filled with a gas volume (GV) 3.5 using a winder, and the filled can was heated in warm water at 40 ° C. for 5 minutes.
Allow to cool to 25 ° C. Then, set the can on the rivet repetition strength tester, hold down the tab assuming that the raised end of the tab has bitten into the carton of the cardboard, and in that state, continue pushing the push-in terminal on the upper surface of the tab push-down end until the score breaks (Number of repeated strokes: 15
The number of repetitions up to the point at which cracks occurred in the score was counted.

[0034]

[Table 1] (Evaluation Results) The bulge pressure of the example 1 with the concave bead was 20 KPa (about 0.20 kgf) as compared with the comparative example 1 without the concave bead.
/ Cm ² ) Was higher. The rivet repetition strength was significantly higher than the 237 times in Comparative Example 1 and was 4 times.
It reached 14 times, and it was confirmed that the rivet repeated strength was improved. That is, in the structure of the first embodiment,
When the panel surface protrudes and bulges due to an increase in the can internal pressure, the distance between the lower surface of the tab nose (pressed portion) and the panel surface is smaller than that in Comparative Example 1, so that the rivet repetition stroke amount is small and damage to the score is reduced. It is presumed that this is because it becomes less. In Example 2 with the concave bead, the bulge pressure was 20 KPa (about 0.20 kgf) as compared with Comparative Example 2 without the concave bead.
/ Cm ² ) high. Also, the rivet repetition strength greatly exceeded the 308 times of Comparative Example 2 and reached 503 times, indicating that the rivet repetition strength was improved. In Example 3 with the concave bead, the bulge pressure was 25 KPa (about 0.25 kgf) as compared with Comparative Example 3 without the concave bead.
/ Cm ² ) high. In addition, the rivet repeat strength greatly exceeded 292 times of Comparative Example 3 and reached 485 times, confirming that the rivet repeat strength was improved. In Example 4 with the concave bead, the bulge pressure was 25 KPa (about 0.25 kgf) as compared with Comparative Example 4 without the concave bead.
/ Cm ² ) high. In addition, the rivet repeat strength greatly exceeded 419 times in Comparative Example 4 and reached 660 times, confirming that the rivet repeat strength was improved.

Next, a test example of the swelling amount of the tab will be described.

[Test Example 2] Three types of lids, a lid without a C-bead, a lid with a C-bead (concave bead) formed only on the tab side, and a lid with a C-bead (concave bead) formed on both the tab side and the score side, were used. When the internal pressure was gradually increased, the change in the internal pressure of the can and the amount of swelling of the tip of the tab nose from the upper end of the tightened portion were measured. FIG. 11 shows the measurement results. In FIG. 11, a positive value indicates the amount of protrusion from the upper end of the tightening portion, and a negative value indicates the amount of decrease from the upper end of the tightening portion. In addition, the inner pressure of the can when the tip of the tab nose is on the same line as the upper end of the tightening portion, that is, when the bulge amount of the tab becomes 0, is referred to as “bulge pressure”. The test lid has a thickness of 0.
235mm lid diameter 204 diameter, concave bead shape, depth 0.3
The width was 05 mm, the width was 1.93 mm, and the radius of curvature at the bottom was 0.38 mm. Also, the concave bead tip position is about 1.0 mm from the score line.
And (Evaluation Results) The lid with the C-bead only on the tab side (line (a) in FIG. 11) is compared with the lid without the C-bead (line (c)).
The effect of the loose metal on the panel surface is small. The tip of the tab nose is 0.2 to 0.3 from the upper end of the tightened part.
mm, and this phenomenon did not change even when the internal pressure of the can increased, and thus it was confirmed that the bulge pressure was improved. This makes it possible to reduce the end plate thickness (plate thickness of the can lid). Further, the lid with the C-bead on both the tab side and the score side (line (b)) has a tendency that the tab nose tip is further lower than the can lid shown by the line (a) in FIG. It was confirmed that the pressure was further improved. The reason is that the bead is formed not only on the tab side but also on the score side, so that the rivet vertical axis is less likely to fall to the lifting end 14 of the tab. As a result, it is presumed that the distance between the lower surface of the tab nose (pressed portion) and the panel surface is smaller than the can lid shown by the line (a) in FIG.

[0036]

As described above, according to the first aspect of the present invention, since the excess thickness generated in the panel portion by the coining process accompanying the formation of the rivet is absorbed by the bead, the can lid is wound around the can body. Even when tightened to form a positive internal pressure can whose internal pressure is higher than the atmospheric pressure, swelling due to the internal pressure of the panel portion or tab can be suppressed. as a result,
It is possible to prevent defects such as cracks and breaks in the score line when transporting cans and the like.

According to the second aspect of the present invention, since the bead for absorbing the excess thickness is formed in an arc shape concentric with the coining area, the excess thickness caused by the coining is more effectively reduced. As a result, the effect of suppressing the rise of the can lid or the tab can be improved.

Further, according to the third aspect of the present invention, since the depression amount of the concave portion in the tab is larger than the concave amount of the concave bead, the same kind of can lids are stacked in the same thickness direction. (When stacked), the bottom of the concave bead in the upper can lid is held at a position separated from the surface of the concave in the concave portion of the tab in the lower can lid, and as a result, they do not come into contact with each other. In the case of stacking, the inner protective coating of the concave bead can be effectively prevented from being damaged.

According to the fourth aspect of the present invention, the bead can absorb a large amount of excess space due to coining without causing breakage of the score line.

Further, according to the fifth aspect of the present invention, the excess thickness due to the formation of the score line together with the excess thickness due to the coining process can be absorbed by each bead, and the rivet portion is located on the lifting end side of the tab. As the internal pressure of the can rises after it is wound around the can body, the difference in swelling between the lifting end side and the pushing-down end side of the tab is reduced, so that it can be more effectively suppressed. become.

[Brief description of the drawings]

FIG. 1 is a front view showing an example of the present invention.

FIG. 2 is a sectional view taken along line II-II of FIG.

FIG. 3 is a cross-sectional view of a state in which two can lids of FIG. 1 are stacked with their orientations aligned in the thickness direction.

FIG. 4 is a front view showing a state in which beads are formed in the process of forming the can lid of FIG. 1;

FIG. 5 is a front view showing another example of the present invention.

6 is a sectional view taken along line VI-VI of FIG.

FIG. 7 is a cross-sectional view showing an enlarged portion of a convex bead in FIG. 6;

FIG. 8 is a front view showing still another example of the present invention.

9 is a sectional view taken along line IX-IX of FIG.

FIG. 10 is a cross-sectional view of a state in which two can lids of FIG. 9 are stacked with their orientations aligned in the thickness direction.

FIG. 11 is a diagram showing a measurement result of a bulging amount of a tab with respect to an internal pressure of a can, which was performed to confirm an effect of the present invention.

[Description of Signs] 1 ... can lid, 2 ... panel part, 5 ... flange / curl part, 6 ... dent part, 7 ... score line, 8 ... opening piece,
Reference numeral 10: rivet, 11: knob (tab), 12: tongue, 13: push-down end, 14: lifting end, A
... recess, B ... coining area (coining part), C,
C1 ... Bead.

Claims (5)

[Claims] A rivet portion is formed at the center of the panel portion so as to protrude with coining, and both ends of the rivet portion are located at predetermined positions on the outer peripheral side of the rivet portion so that a connecting portion remains. An opening piece is defined by an open-shaped score line whose parts are separated from each other, and a panel part having one depressed end positioned on the opening piece and the other raised end opposite to the opening piece with the rivet part interposed therebetween. An easily openable can lid having a tab located thereon fixed to the panel portion by the rivet portion via a bendable tongue portion formed at an intermediate portion thereof, wherein the coining process is performed outside the opening piece; A bead obtained by convexly or concavely deforming the panel portion is formed on an outer peripheral side of the region along the outer peripheral edge of the coining region. Easy-to-open can lid. 2. The coining region according to claim 1, wherein the coining region has an annular shape centered on the rivet portion, and the bead has an arc shape concentric with the coining region. Easy opening can lid. 3. The tab tongue portion of the tab is formed in a recess depressed from the upper surface of an outer peripheral portion of the tab, and the bead is positioned within a range where the recess is projected onto the panel portion. 2. The concave bead is formed as a concave bead which is depressed on the lower surface side opposite to the upper surface on which the tab is attached, and the amount of depression of the concave bead is an amount satisfying a range not contacting the concave surface. Or an easy opening can lid according to 2. 4. The method according to claim 1, wherein an interval between each end of the bead and the score line is set in a range of 0.5 mm to 2.0 mm. Easy opening can lid. 5. A bead obtained by concavely deforming the panel portion is formed inside the opening piece and on the outer peripheral side of the coining region along the outer peripheral edge of the coining region. The easy opening can lid according to any one of claims 1 to 4, characterized in that: