Opening tab and can lid

Abstract

This design accommodates the thinning of the can-opening tab while preventing tearing at the slot ends during opening, thereby improving the ease of opening the can. [Solution] The tab body has a flat fixing portion that has rivet holes and is fixed in contact with the can lid body, a nose portion provided at one end on the center line along the length of the tab body to push down the opening piece of the can lid body to open it, and a lifting portion provided on the opposite side of the center line from the nose portion, with the rivet holes in between. The fixing portion is partitioned by a slot portion formed radially outside the rivet holes, the slot portion is formed to enclose more than half of the circumference of the rivet holes on the opposite side from the nose portion, and both ends are formed closer to the nose portion than a line perpendicular to the center line, and at least both ends have a burring portion formed which is bent downward, and the length from the upper surface of the bent portion in the burring portion is 2.65 times or more and 2.85 times or less the plate thickness of the fixing portion.

Description

Technical Field

[0001] The present invention relates to an opening tab of the stay-on tab type that is fixed on a can lid body and opens a drinking mouth by pushing down a part of the can lid body while being attached to the can lid body, and a can lid to which the opening tab is attached.

Background Art

[0002] As an opening tab (hereinafter, may be simply referred to as a tab) provided on a can lid of a beverage can, a stay-on tab type that can open a drinking mouth while the tab is attached to the can lid body is known. The can lid equipped with this tab has the tab attached by a rivet. By pulling up one end (lifting part) of the tab, the vicinity of the rivet becomes a fulcrum, and the other end (nose part) of the tab becomes a point of action, pressing an opening piece surrounded by a score on the panel surface and immersing the opening piece into the can while breaking the score, thereby opening it. At this time, the start end and the end end of the score are separated, and the opening piece is pushed into the inside of the beverage can without leaving the can lid body to open the can.

[0003] As such a tab, for example, the one described in Patent Document 1 is known. This tab has a nose part arranged at the front end of the tab, a lift part arranged at the rear end of the tab, a rivet hole, a rivet receiving part arranged close to the nose part and attached to the nose part, and a curl part provided on the outer edge of the tab. It is described that a C-shaped slot is formed around the rivet receiving part, and the opposing ends of the slot define a fulcrum (the fulcrum when lifting the tab to open).

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

[0005] By the way, from the perspective of weight reduction, there is a demand to make the tabs thinner. However, when the tabs are made thinner, their rigidity decreases, which can cause tears to occur at the ends of the slots when the tabs are raised to open the can, making it difficult to open.

[0006] This invention has been made in view of these circumstances, and aims to improve the ease of opening cans by preventing tearing at the end of the slot during opening, while accommodating the thinning of the can-opening tab. [Means for solving the problem]

[0007] The can-opening tab of the present invention comprises a tab body that forms the outer shape, a flat plate-shaped fixing portion having a rivet hole for fixing to the rivet of the can lid body and fixed in contact with the can lid body, a nose portion provided at one end on a center line passing through the center of the rivet hole and along the length direction of the tab body for pushing down the opening piece of the can lid body to open it, and a lifting portion provided on the opposite side of the center line from the nose portion, across the rivet hole, for lifting up to push down the nose portion, The fixing portion is demarcated by a slot portion formed radially outward from the rivet hole, the slot portion is formed to enclose more than half of the circumference of the rivet hole on the side opposite to the nose portion, and both ends are formed closer to the nose portion than a line perpendicular to the center line. At least both ends of the slot portion are formed with burring portions that are bent downward, and the length of the bent portion from the upper surface of the burring portion is 2.65 times or more and 2.85 times or less the thickness of the fixing portion.

[0008] At both ends of the slot, the fixed portion is almost in contact with the can lid body, but when the can is opened, the lifting portion is pulled up, generating a force in the tearing direction. If a crack occurs in this area, the tab body will bend, making it difficult to open. In this invention, since both ends of the slot are formed by bending downwards to create burring portions, the strength against force in the tearing direction is increased, making it less prone to cracking. In this case, if the length of the burring portions at both ends of the slot is less than 2.65 times the thickness of the fixed portion, it is likely to crack because it cannot withstand the force in the tearing direction when the can is opened. If the length exceeds 2.85 times the thickness of the fixed portion, the tip of the burring portion may come into contact with and damage the can lid body, and molding will also become difficult.

[0009] In the can-opening tab of the present invention, both ends of the slot portion are formed as semicircular arcs in plan view, and the burring portion is preferably formed on the arc portion with a length along the arc.

[0010] The tearing force applied when opening a can does not always occur along the center of the slot in the width direction (the center of the arc), and may shift in the width direction depending on how it is opened. In this embodiment of the present invention, since the burring portion is formed at least along the arc and for a length along the arc, the burring portion can prevent crack formation even if the tearing force is slightly shifted within the range of the arc.

[0011] The can lid of the present invention comprises an opening tab and a can lid body, wherein the rivets of the can lid body are fixed to the rivet holes of the opening tab. [Effects of the Invention]

[0012] According to the present invention, since burring portions of a predetermined length are formed at both ends of the slot portion around the fixing portion, cracks are prevented from occurring when opening the can, and the occurrence of bending of the tab body is suppressed. As a result, the can lid can be made thinner and is easier to open. [Brief explanation of the drawing]

[0013] [Figure 1] This is a plan view of a can lid having an opening tab according to an embodiment of the present invention. [Figure 2] Figure 1 shows a longitudinal cross-section passing through the center of the rivet on the can lid. [Figure 3] This is a plan view of the tab for opening cans. [Figure 4] Figure 3 shows a longitudinal cross-sectional view along the center line passing through the center of the rivet hole of the can-opening tab. [Figure 5] Figure 3 is an enlarged cross-sectional view of the curled portion along the radial direction of the rivet holes in the area indicated by B of the can-opening tab. [Figure 6] Figure 3 shows cross-sectional views of both ends of the slot section, with (a) being a cross-sectional view taken along the EE line in Figure 3 and (b) being a cross-sectional view taken along the FF line in the same figure. [Figure 7] This is a plan view of the blank after the connecting piece has been removed during the molding process of the can-opening tab. [Figure 8] This is a plan view showing the state after burring has been performed on both ends of the slot section, as shown in Figure 7. [Figure 9] This is a longitudinal cross-section of the burring process. [Figure 10] This photograph shows the degree of deformation when the can is opened using the opening tab. [Modes for carrying out the invention]

[0014] Hereinafter, embodiments of the can-opening tab and can lid according to the present invention will be described with reference to the drawings. The can lid 1 of this embodiment is a so-called stay-on tab type can lid, used for cans such as beverage cans, and as shown in Figures 1 and 2, it consists of a can lid body 10 and an opening tab 20 attached to the can lid body 10. Furthermore, the can lid 1 configured in this way is crimped onto the open end of a can body (not shown) filled with contents, thereby manufacturing a can that seals the inside of the can body. The can body, can lid body 10, and opening tab 20 are each made of aluminum alloy.

[0015] The can lid body 10 includes a substantially disc-shaped panel portion 11 and an annular countersink portion 12 provided so as to protrude downward along the outer peripheral portion of the panel portion 11. A panel boss 13 formed in a concave shape is provided in a part of the panel portion 11. On the surface of the panel boss 13, a score 15 that defines an opening piece 14, a rivet 16 to which a tab 20 is attached, and a finger hook recess 17 arranged on the opposite side of the opening piece 14 via the rivet 16 are provided.

[0016] As shown in FIGS. 3 and 4, the can-opening tab 20 has a curled portion 22 formed by bending the peripheral edge of a tab body 21 that forms the outer shape thereof to the lower surface side, and the overall rigidity is enhanced. Near the center of the tab body 21, a fixing portion 24 having a rivet hole portion 23 fixed to the rivet 16 of the can lid body 10 is provided. The fixing portion 24 is partitioned and formed by a U-shaped slot 25 and is formed in a flat plate shape as a whole. The can-opening tab 20 is attached to the can lid body 10 by inserting the rivet 16 of the can lid body 10 into the rivet hole portion 23 formed in the fixing portion 24 and crimping the head of the rivet 16 while making the lower surface of the fixing portion 24 abut against the bottom surface of the panel boss 13.

[0017] Further, the can-opening tab 20 includes a nose portion 26 provided at the tip of the tab body 21 for pushing down and opening the opening piece 14 of the can lid body 10, a pulling-up portion 27 provided at the rear end portion arranged on the opposite side of the fixing portion 24 of the tab body 21 with respect to the nose portion 26 and pulled up from the can lid body 10 to push down the nose portion 26, and a finger hook hole portion 28 provided between the pulling-up portion 27 and the fixing portion 24 of the tab body 21 and penetrating in the thickness direction.

[0018] As described above, the peripheral edge of the tab body 21, including the nose portion 26 and the lifting portion 27, is bent downwards to form a curled portion 22. However, in the lifting portion 27, a recess 29 is formed at the rear end of the tab body 21, in a part of the lower surface of the curled portion 22 (the central part in the width direction). Therefore, the thickness of the curled portion 22 in the area of ​​this recess 29 is thinner than the thickness at the left and right positions of the recess 29 (the thickness from the upper surface of the lifting portion 27 to the lower surface of the curled portion 22 that protrudes downwards on the tab body 21).

[0019] Furthermore, the lifting portion 27 has an outer shape perpendicular to the center line C (the center line of the tab body 21 passing through the center of the rivet hole portion 23 and the tip of the nose portion 26) along the length direction of the tab body 21 passing through the center of the rivet hole portion 23, but the outer shape of the nose portion 26 in plan view (the outer shape of the outer circumference of the curl portion) is formed in the shape of an arc with a radius of curvature Rn centered on the center of the rivet hole portion 23.

[0020] Note that the shape of the curled portion varies slightly depending on the location, so the curled portion near the nose portion 26 will be described as reference numeral 22N. When referring to the curled portion without specifying a particular location, reference numeral 22 will be used. Also, as will be described later, the curled portion on the left side of the center line C of the can-opening tab 20 may be distinguished as 22L, and the curled portion on the right side as 22R.

[0021] Further, FIG. 5 shows a longitudinal cross-section along the radial direction of the rivet hole portion 23 in a part (range shown as B1 in FIG. 3) of the curl portion 22 that is at least to the left of the center line C of the nose portion 26. As shown in this FIG. 5, the curl portion 22L in the left side portion of this nose portion 26 includes the top surface portion 31 of the tab body 21, an obliquely upward outer upper curved portion 32a that is curved to protrude outward from the top surface portion 31, and an obliquely downward outer lower curved portion 32b provided below the outer peripheral edge of the outer upper curved portion 32a, a bottom surface portion 33 that is continuous with the lower edge of the outer lower curved portion 32b and extends radially inward, an inner lower bent portion 34 that is connected to the radially inner edge of the bottom surface portion and is bent to protrude obliquely downward and rises upward, a rising wall 35 connected to the upper end of the lower bent portion 34, and an inner upper bent portion 36 that is bent to protrude obliquely upward from the upper end of the rising wall 35.

[0022] Also, the outer upper curved portion 32a and the outer lower curved portion 32b are formed by one arc or a plurality of continuous arcs from the top surface portion 31 to the bottom surface portion 33 of the tab body 21. In the example shown in FIG. 5, the radius of curvature R1a of the upper part of the outer curved portion 32 is slightly smaller than the radius of curvature R1b of the lower part, but they may have the same radius of curvature. That is, the relationship is R1a < R1b or R1a = R1b. Also, the bottom surface portion 33 following the outer lower curved portion 32b is formed with a certain width up to the inner lower bent portion 34. This bottom surface portion 33 is arranged substantially parallel to the top surface portion 31 and is in contact with the surface of the panel boss 13 of the can lid body 10.

[0023] Then, the inner lower bent portion 34 is continuous with the radially inner edge of the bottom surface portion 33. In the case of the illustrated example, this inner lower bent portion 34 is bent at an acute angle, and the rising wall 35 is on its upper edge, and the inclination angle θ3 with respect to the thickness direction of the tab body 21 extends vertically or obliquely upward at 0° or more and 30° or less, and the inner upper bent portion 36 is continuous with its upper edge. This inclination angle θ3 is preferably 5° or more and 25° or less. In the case of the illustrated example, the inclination angle θ3 is set to about 20°.

[0024] Furthermore, the inner upper bent portion 36 is bent at approximately 90°, and its tip portion 37 is directed inward towards the curled portion 22. In this case, the tip portion 37 extending from the inner upper bent portion 36 is inclined slightly downward with respect to the horizontal direction perpendicular to the thickness direction. The outer surface of the inner upper bent portion 36 is positioned with a small gap between it and the back surface of the top portion 31 of the tab body 21. This gap may be absent, and the outer surface of the inner upper bent portion 36 may be in contact with the back surface of the top portion 31. Alternatively, the tip portion 37 extending from the inner upper bent portion 36 may be inclined slightly upward with respect to the horizontal direction, in which case the tip portion 37 may be in contact with the back surface of the top portion 31.

[0025] When the radius of curvature of the outer surface of the outer upper curved portion 32a is R1a and the radius of curvature of the outer surface of the outer lower curved portion 32b is R1b, and the radii of curvature of the outer surfaces of the inner lower bend portion 34 and the inner upper bend portion 36 are R2 and R3, respectively, the dimensional relationship is R1a ≤ R1b and R1b > R2 ≥ R3. In other words, the radius of curvature R2 of the inner lower bend portion 34 and the radius of curvature R3 of the inner upper bend portion 36 are smaller than the radius of curvature R1b of the outer lower curved portion 32b. The radius of curvature R2 of the inner lower bend portion 34 and the radius of curvature R3 of the inner upper bend portion 36 may be the same dimension, but the radius of curvature R3 of the inner upper bend portion 36 may be smaller than the radius of curvature R2 of the inner lower bend portion 34. In the illustrated example, R2 > R3.

[0026] To illustrate with specific dimensions, this can-opening tab 20 is formed by processing a metal plate with a thickness of 0.26 mm to 0.30 mm, preferably 0.27 mm to 0.29 mm. The radius of curvature R1a of the outer lower curved portion 32b is 0.8 mm to 1.4 mm, the radius of curvature R2 of the inner lower bend portion 34 is 0.2 mm to 0.5 mm, and the radius of curvature R3 of the inner upper bend portion 36 is 0.3 mm or less. More preferably, R1b is 1.0 mm to 1.8 mm, R2 is 0.3 mm to 0.5 mm, and R3 is 0.2 mm or less.

[0027] Furthermore, the thickness T1 of the curled portion 22L in this area (the distance in the thickness direction of the tab from the upper surface of the top portion 31 to the lower surface of the bottom portion 33) is 1.5 mm or more and 1.6 mm or less. The width W1 of the curled portion 22L (the distance from the outermost position of the outer upper curved portion 32a or outer lower curved portion 32b along the radial direction of the rivet hole portion 23 to the innermost position of the inner lower bend portion 34) is 1.5 mm or more and 2.0 mm or less, preferably 1.6 mm or more and 1.9 mm or less. The indentation width W2 of the tip portion 37 (the distance along the radial direction from the innermost position of the inner lower bend portion 34 to the tip of the tip portion 37 along the radial direction of the rivet hole portion 23) is 0.7 mm or more and 1.2 mm or less, preferably 0.8 mm or more and 1.1 mm or less. The distances W1 and W2 have a relationship where W1 / W2 is between 0.3 and 0.6.

[0028] The angle range of the left portion of the nose portion 26 that has the shape of such a curled portion 22L is a range of 30° to 80° in a clockwise direction with the rivet hole portion 23 (center) as the center line that passes through the center of the rivet hole portion 23 along the length direction of the tab body 21 (the center line of the tab body 21 that passes through the center of the rivet hole portion 23 and the tip of the nose portion 26), with the center line passing through the center of the rivet hole portion 23 along the length direction of the tab body 21 being 0°, that is, a range of 30° to 80° from the center line shown as C in Figure 3, preferably a range of 40° to 70°. This is the range shown as B1 in Figure 3.

[0029] Furthermore, when the tab 20 is attached to the can lid body 10, as shown by the dashed line in Figure 1, the starting end 15a of the score 15 is positioned inside the left curl portion 22L of the nose portion 26 with respect to the center line C, while the score 15 is positioned so as to cross directly below the right curl portion 22R of the nose portion 26. For this reason, the right curl portion 22R with respect to the center line C is formed to be thinner than the left curl portion 22L so as not to come into contact with the score 15. For example, it is preferable that the T1 of the left curl portion 22L of the nose portion 26 (the area shown as B1 in Figure 3) is 1.5 mm or more and 1.6 mm or less, and the T1 of the right curl portion 22R of the nose portion 26 (the area opposite to B1 in Figure 3 across the center line C) is 1.3 mm or more and 1.4 mm or less. By making the thickness of the curled sections 22L and 22R different on the left and right sides of the nose section 26, as mentioned above, the score 15 on the right side is not made to come into contact with the score, and on the left side, the score 15 below the tab 20 can be broken sequentially from the starting end, thereby preventing accidental opening.

[0030] Furthermore, the slot portion 25 surrounding the rivet hole portion 23 is formed in a U-shape overall, with both ends 25a formed in a semicircular arc shape. Burring portions 51 are formed on the outer circumference and both ends 25a so as to bend downward at approximately a right angle. Figure 6 shows cross-sections of the burring portions 51 at both ends 25a of the slot portion 25, where (a) is the left side with respect to the center line C and (b) is the right side with respect to the center line C. Each is a cross-section in a direction parallel to the center line C.

[0031] As described above, on the left side of the center line C, the curled portion 22L is formed in the same shape as in Figure 5, whereas the curled portion 22R on the right side is formed in a flatter shape compared to the curled portion 22L on the left side, with the top surface portion 52 and the bottom surface portion 53 arranged almost parallel to each other and connected by the outer curved portion 54. Inside, an inner curved portion 55 with a radius of curvature smaller than that of the outer curved portion 54 is formed continuously on the bottom surface, and the tip portion 56 of the inner curved portion 55 is in contact with the back surface of the top surface portion 52 in an arrangement almost parallel to it. The radius of curvature of the outer curved portion 54 may be set to one, or multiple radii of curvature may be arranged continuously. The same applies to the inner curved portion 55.

[0032] On the left side of the center line C, the surface between the curled section 22L and the burring section 51 (referred to as the connecting section 72) is formed as a gently sloping surface with a slight concave shape. On the right side, however, the area near the inner circumference of the curled section 22R is concave so as to follow the outer surface of the tip of the inner curved section 55, and the concave bend 57 extends almost horizontally or with a slight downward slope to the burring section 51. In other words, to the left of the center line C, the connecting portion 72 has a smooth surface, whereas to the right, it has a stepped shape with a concave bend 57 formed on the inner circumference of the curled portion 22R. Therefore, the inclination angle of the surface of the connecting portion 72 toward the burring portion 51 is smaller on the right side than on the left side. Furthermore, in both curled sections 22L and 22R, the tip of the connecting section 72 is formed as a flat section 72a, and a burring section 51 is formed at the tip of the flat section 72a via a bent section.

[0033] The burring portion 51 is formed such that the length Lb from the upper surface of the bent portion 51a, that is, from the upper surface of the flat portion 72a, is 2.65 times or more and 2.85 times or less the thickness of the fixing portion 24 (original thickness). If it is less than 2.65 times, when the tab 20 is pulled up while attached to the can lid body 10, there is a risk of tearing from the end of the slot portion 25, and if it exceeds 2.85 times, there is a risk of contact with the can lid body 10 when attached to the can lid body 10, and molding also becomes difficult. Preferably, it is formed to a length L of 2.70 times or more and 2.80 times or less the thickness t0 of the fixing portion 24. The thickness of the fixing portion 24 is the thickness of the material before processing into the tab 20, and as mentioned above, it is 0.26 mm or more and 0.30 mm or less, preferably 0.27 mm or more and 0.29 mm or less.

[0034] Regarding other dimensions, although not necessarily limited, the length Lt of the can-opening tab 20 along the aforementioned center line C is 24.0 mm or more and 26.0 mm or less, and the maximum width Wt of the can-opening tab 20 perpendicular to the center line C is 15.0 mm or more and 17.0 mm or less. In addition, the radius of curvature Rn of the nose portion 26 in plan view is 6.5 mm or more and 8.5 mm or less, and may be formed by multiple radii of curvature within that range.

[0035] The can-opening tab 20, constructed in this manner, is formed by sequentially performing processes such as punching holes, cutting out the outer shape, and curling while feeding a strip-shaped sheet material in the length direction, and then separating it from the sheet material. This series of processes involves repeatedly performing partial processing while transporting the sheet material between an upper and lower die. In the curling process, the peripheral edges of the tab material, which has been cut to form an outer shape, are folded back to the reverse side and rolled to create a curled shape. Then, the curled portion is formed by slightly compressing it in the thickness direction.

[0036] In this series of processes, as shown in Figure 7(a), the blank 63, which will be the unfolded outer shape of the tab, is cut off from the sheet material 61, excluding the connecting piece 62, and at this time, holes 64 and 65 that will become the rivet holes 23, slots 25 and finger holes 28 are formed. In this case, the rivet holes 23 are the final shape as they are not processed afterward, but the holes 64 and 65 that will become the slots 25 and finger holes 28 are formed slightly smaller to accommodate the processing allowance. Then, as shown in Figure 7(b), the outer circumference and both ends 25a of the hole 64 that will become the slots 25 are bent by burring.

[0037] As shown in Figure 8, in this burring process, the lower surface of the blank 63 is supported by the upper surface of the lower die 71, and the tip of the blank 63 is held in a position where it protrudes from the tip of the lower die 71 at the location of the hole 64, and the protruding portion 74 is bent downward by a punch 73 that is driven in the vertical direction. An arc-shaped corner portion 75 is formed at the tip of the lower die 71, and the protruding portion 74 of the blank 63 is bent along the curvature of this corner portion 75, and a burring portion 51 is formed downward at the tip of this bent portion 51a.

[0038] After the curled portion 22 and other parts descend, the connecting piece 62 is finally cut to separate it from the sheet material 61, completing it as a can-opening tab 20. The tab is then attached to the can lid body 10 by passing the rivet 16 of the can lid body 10 through the rivet hole 23 and crimping the rivet 16.

[0039] A beverage can is manufactured by crimping this can lid 1 onto the opening of a can body filled with beverage. In this beverage can, when the lifting portion 27 of the opening tab 20 is pulled up, the nose portion 26 presses against the opening piece 14 with the vicinity of the rivet 16 acting as a fulcrum, and the score 15 first breaks (pops) in the portion between the nose portion 26 and the rivet 16. Then, when the tab 20 is pulled further upward, the break of the score 15 progresses sequentially clockwise (tears) and the broken opening piece 14 is folded inward. By bending the opening piece 14 inward with the tab 20, the score 15 breaks to its end point.

[0040] During this can-opening operation, a force acts on the tab 20 to bend the portion between the nose portion 26 and the rivet 16. Therefore, if the strength of the tab 20 is insufficient, bending may occur at that point, hindering can-opening and potentially resulting in can-opening defects such as being unable to break the score 15 or the breaking of the score 15 stopping midway.

[0041] Furthermore, in the curled portion 22L on the left side of the nose portion 26, there is an inner lower bend portion 34, a rising wall 35, and an inner upper bend portion 36 at radially inward positions of the outer upper curved portion 32a and the outer lower curved portion 32b. Since the radii of curvature R2 and R3 of these inner lower bend portion 34 and inner upper bend portion 36 are small, and there is a rising wall 35 that extends in the vertical direction, the shape rigidity is increased, and therefore the occurrence of deflection during the can opening operation is suppressed.

[0042] These synergistic effects increase the rigidity of the left side of the tab 20, effectively preventing deflection during the can-opening operation. As a result, the series of actions of lifting the tab 20 and pushing the opening piece 14 into the can allows the score 15 to be properly broken from start to finish, preventing can-opening failures.

[0043] It should be noted that the present invention is not limited to the configuration of the above-described embodiment, and various modifications can be made to the detailed configuration without departing from the spirit of the present invention. In the curled portion 22L on the left side of the nose portion 26, the rising wall 35 has an inclination angle θ3 of 0° or more and 30° or less with respect to the thickness direction of the can opener tab 20, which is perpendicular to the radial direction of the rivet hole portion 23. In the example shown in Figure 5, it is inclined inward towards the curled portion 22 (radially outward from the rivet hole portion 23), but this also includes the case where it is inclined outward towards the curled portion 22 (radially inward from the rivet hole portion 23). [Examples]

[0044] For the tab material, a 0.280 mm thick sheet of rolled material made from JIS A5182 Al-Mg aluminum alloy was used and formed into tabs. In this case, tabs with the curled shape of this embodiment and tabs with the conventional curled shape were produced as comparative examples. Furthermore, as a standard conventional example, tabs with the conventional curled shape were also produced from a 0.32 mm thick sheet of the same JIS A5182 Al-Mg aluminum alloy. On the other hand, the can lid body was manufactured from a 0.235 mm thick rolled material made of JIS A5182 aluminum alloy, and the three types of tabs mentioned above were attached to it.

[0045] For these samples, the can lid was placed on a can opening load measuring machine, a locking device was attached to the tab's lifting section, and the locking device was pulled at a predetermined speed to investigate whether or not there was any deflection of the tab when it was raised to 90°. Furthermore, with the tab rotated 90° on the can lid body (i.e., the nose portion detached from the opening piece surrounded by the score, preventing the score from breaking), the tab was raised using a can opening load measuring device, and the load until the tab broke was also measured. Ten cans were measured, and the average value was calculated.

[0046] Figure 9(a) is a plan view of the can-opening tab of this embodiment, manufactured as described above, from the fixed portion to the nose portion, and Figure 9(b) is a plan view of a similar portion of a conventional example. Comparing Figure 9(a) and (b), the conventional can-opening tab shown in (a) is connected from the fixed portion to the curled portion by a gentle and relatively wide inclined surface. However, in the can-opening tab of this embodiment, the inner circumference of the curled portion of the nose portion is significantly embedded in the curled portion, which widens the fixed portion and reduces the dimension of the inclined surface along the radial direction of the rivet hole compared to the conventional example. As can be seen in Figure 9, the tab in the conventional example appears to have a slight deflection, but this does not cause any practical problems. In the comparative example, a large deflection occurred at the tip of the tab. The tab in the embodiment did not deflect, similar to the conventional example.

[0047] Furthermore, the load when the tab bent was 32.78 N in the conventional example, 28.53 N in the comparative example, and 31.75 N in the example. These results indicate that the embodiment, while being a lightweight tab with a thinner plate thickness, possesses excellent strength comparable to conventional examples with a thicker plate thickness, and is a tab that does not flex when opening a can.

[0048] Furthermore, in this case, the short tabs of the burring portion 51 at both ends 25a of the slot portion 25 showed cracking from both ends, as indicated by the arrows in Figure 10. Tabs of the burring portion 51 formed to the appropriate length showed no cracking and were normal. [Explanation of Symbols]

[0049] 1 Can lid 10 Can lid body 11 Panel section 12 Countersink section 13 Panel Debossing 14 Opening piece 15 score 16 rivets 20 Opening tabs 21 Tablet body 22, 22N, 22L curl section 23 Rivet hole 24 Fixing part 25 slots 25a Both ends 26 Nose section 27 Lifting section 31 Top section 32 Outer curved part 33 Bottom part 34. Inner lower curve 35. Rising wall 36. Inner upper curved section 37 Tip 41. Circular arc surface 42 1st slope 43 Second slope 44. Bending section 51 Burring section 51a Bend part 52 Top section 53 Bottom part 54 Outer curved part 55 Inner curved section 56 Tip 57 Concave bend 61 Sheet material 62 Connecting piece 63 Blank 64,65 Hole 71 Lower mold 72 Connecting part 72a Flat part 73 punches 74 Corner Section

Claims

1. The tab body that forms the outer shape has a rivet hole portion that is fixed to the rivet of the can lid body, a flat plate-shaped fixing portion that is fixed in contact with the can lid body, a nose portion provided at one end on a center line that passes through the center of the rivet hole portion and is along the length direction of the tab body to push down the opening piece of the can lid body to open it, and a lifting portion provided on the opposite side of the center line from the nose portion, sandwiching the rivet hole portion, to be pulled up in order to push down the nose portion, The fixing portion is demarcated by a slot portion formed radially outward from the rivet hole, the slot portion is formed to enclose more than half of the circumference of the rivet hole on the side opposite to the nose portion, and both ends are formed closer to the nose portion than a line perpendicular to the center line. A tab for opening cans, characterized in that at least both ends of the slot portion have burring portions formed which are bent downward, and the length of the bent portion in the burring portion from the upper surface is 2.65 times or more and 2.85 times or less the plate thickness of the fixing portion.

2. The can-opening tab according to claim 1, characterized in that both ends of the slot portion are formed into a semicircular arc portion in plan view, and the burring portion is formed at least on the arc portion with a length along the arc.

3. A can lid comprising a can-opening tab and a can lid body as described in claim 1 or 2, wherein the rivets of the can lid body are fixed to the rivet holes of the tab.

Images