JP2000062776A - Method for manufacturing easy-open can lid with excellent openability - Google Patents

Abstract

(57) [Summary] [Problem] To manufacture an easy open can lid excellent in can openability by stably reducing the can opening force. A can lid panel formed of a metal plate having a plate thickness t ₀ (mm), a work hardening index n in a region of 40 to 90% of uniform elongation, and a tensile strength TS (kgf / mm ² ), One of the molds is a curved mold with a tip radius of more than 0.025 to 1.0 mm, and the other mold is formed by pressing using a flat mold to form an opening groove,
The metal plate thickness of the thinnest part of the can lid panel satisfies the formulas (1) and (2), the offset distance of the tab fastening position from the center of the can lid, and the length between the tab fastening center and the finger hook holding part Defines the angle between the center line before the tab rotation and the center line at the opening position,
When the tab is rotated to a position where the can is opened, a slope-shaped projection is formed for lifting the tab above the height of the tightening portion. 5.0 <P ≦ 7.0 (1) P = t × TS × ｛exp (n) / (n ⁿ )｝ × [2 / √3 × | ln ｛1 +
(tt ₀ ) / t ₀ ｝ |] ⁿ (2)

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for producing an easy-open can lid used for a can lid of a beverage can or a food can, in which an opening formed in the can lid of a can body is broken to open the can. It is about.

[0002]

2. Description of the Related Art As a can lid for a can containing various beverages and foods, an easy-open can that is opened by breaking the opening formed in the can lid by pulling up a tab attached to the can lid with a fingertip or the like. The lid is widely used. Easy open can lids are roughly classified into partial open type can lids mainly used for beverage can lids and full open type can lids mainly used for food cans.

Partial open type can lids are roughly classified into pull-top tab type can lids and Steion tab type can lids. FIG. 5 is a schematic plan view showing an example of a pull-top tab type can lid. The opening of the pull-top tab type can lid shown in FIG. 5 is performed as follows. That is, the tab 3 attached by the rivet mechanism 8 to the center of the central panel portion 7 of the can lid 1 made of a metal plate such as steel or aluminum alloy is pulled up with a fingertip or the like to open the opening groove 2 in the central panel portion 7. The breaking opening 5 in which the
The working end of pushes down. As a result, the opening groove 2 is broken, and by further pulling the tab 3, the broken opening piece is completely separated from the can lid 1.

FIG. 6 is a schematic plan view showing an example of a canion tab type can lid. The opening of the Steion tab type can lid shown in FIG. 6 is performed as follows. That is, the tab 3 attached by the rivet mechanism 8 to the center of the central panel portion 7 of the can lid 1 made of a metal plate such as steel or aluminum alloy is pulled up with a fingertip or the like to open the opening groove 2 in the central panel portion 7. By the action of the lever, the working end of the tab 3 pushes down the breaking opening 5 in which is cut. As a result, the opening groove 2 is broken, and further, the breaking is advanced by pulling up the raised end of the tab 3, and a part of the broken opening piece generated at that time is connected to the can lid 1 inside the can. Push into.

Further, the full-open type can lid has a groove for opening formed along the outer peripheral edge of the can lid, and the tab attached to the panel portion near the outer peripheral edge of the can lid can be pulled up with a fingertip or the like. Allows the opening piece to be separated from the can lid, as in the pull-top tab type.

Conventionally, as shown in FIG. 7, the formation of the opening groove in such an easy-open can lid has been performed by a processing tool 10 having a cutting edge-shaped projection having a predetermined opening contour.
Is performed by pressing with a high load such that a groove for opening having a depth of 1/2 or more of the thickness of the lid plate 11 is formed from the surface side of the can lid using a press. Thus, the groove 9 having a V-shaped cross section was formed.

[0007]

A considerable amount of force is required to pull up the tab for opening the conventional easy open can lid described above, and opening the can is not easy for a child or an elderly person.

As a measure against the above-mentioned problem in forming a groove for opening by pressing a machining tool having a cutting edge-shaped projection, for example, Japanese Patent Publication No. 55-10454.
Japanese Patent Publication No. 3-71500 and Japanese Patent Publication No. 3-71501 have been proposed, but none of the above proposals has sufficiently reduced the tab pulling force.

Further, Japanese Patent Publication No. 3-5890, Japanese Patent Application Laid-Open No. 62-235053, Japanese Patent Application Laid-Open No. 2-179329 and the like combine tab reduction by combining thickness reduction processing and processing from the inner surface side of the can lid. Although a method of reducing the pulling force has been proposed, even the above-described method has not yet sufficiently reduced the tab pulling force.

Japanese Utility Model Publication No. 63-40439 discloses a finger for widening the gap between the center panel portion of the can lid and the finger hooking and gripping portion of the tab in order to facilitate insertion of the finger and gripping of the finger hooking and gripping portion. It has been proposed to form an insertion recess in the central panel section below the finger grip of the tab, and
In Japanese Utility Model Laid-Open No. 5-40133, the tab is moved from an unopenable position in which the central axis of the tab deviates from the central axis of the breaking opening to an openable position where the central axis of the tab and the central axis of the breaking opening coincide. Rivet the tab to the extent possible, and while the tab is moving from the non-openable position to the openable position, the tapered protrusion on the central panel located between the rivet and the finger gripping part of the tab, It has been proposed that the finger hooking portion of the tab is lifted to facilitate insertion of a finger into the gap between the central panel portion of the can lid and the finger hooking portion of the tab and finger hooking on the finger hooking portion.

According to the above-mentioned can lid, since the finger insertion concave portion or the tapered projection is formed in the central panel portion, the central panel portion of the can lid is compared with the can lid in which the finger insertion concave portion or the tapered projection is not formed. It is easy to insert a finger into the gap between the tab and the finger-holding / holding portion and to hook the finger-holding / holding portion. However, the tabs need to be riveted in the center of the central panel to fit the tabs within the wrap and to allow space for a finger to be inserted between the tab end and the wrap. Therefore, the length L between the center of the tab fastening and the tab holding part for the tab finger is d (inner diameter of the can lid) / 2-5 m
Since it is limited to m or less and the pulling force at the time of can opening does not change, the can opening force has not yet been reduced.

Therefore, an object of the present invention is to solve the above-mentioned problems, to stably reduce the can opening power, and to allow even children and the elderly to easily open cans. It is to provide a method of manufacturing a lid.

[0013]

DISCLOSURE OF THE INVENTION The inventors of the present invention have conducted earnest research to solve the above-mentioned problems and develop a method for manufacturing an easy-open can lid which has excellent can openability and does not cause impact damage. Overlaid.

Conventionally, breakage of the opening groove at the time of opening the can is
It is considered to be caused by shear deformation, and the shape of the opening groove was designed based on such an idea. However, as a result of the study by the present inventors, it has been clarified that the fracture of the opening groove is not caused by the shear deformation but is mainly caused by the tensile deformation. Therefore, in order to reduce the opening force, the opening can be reduced. It was found that it is effective to reduce the thickness and strength of the thinnest part of the working groove.

Based on the above findings, the inventors of the present invention previously disclosed in Japanese Patent Application No. 9-360778 that the thickness of the thinnest portion of the can lid panel opening groove is within a specified range in relation to the tensile strength of the metal sheet. The patent application was filed for a method for producing an easy-open can lid that has excellent can openability and does not cause impact damage by prescribing.

In order to effectively utilize the lever action, the inventors of the present invention make the tab longer than before and increase the distance between the finger gripping portion (force point) and the fulcrum of the tab. I considered that.

The conventional tab is fixed to the center of the can lid panel, and the length of the tab is limited by the diameter of the can lid panel in order to cause the tab in the panel. Therefore, the inventors of the present invention attached the tab by shifting the tab fastening from the center of the can lid panel, and when the tab was rotated to the openable position, formed a tapered projection that lifts the finger-holding portion. By setting the finger-holding and sandwiching portion at the openable position to a position that is higher on the outer circumference of the can lid and higher than the peripheral edge of the can lid, it is possible to attach a tab that is longer than before and to utilize the leverage more effectively. In addition, the opening load can be reduced, and the finger can be easily hooked, and the patent application was previously filed by Japanese Patent Application No. 7-28214.

As a result of further studies by the present inventors, it was found that the following actions and effects can be newly obtained by using the above two techniques together. In other words, by making the tab longer and making more effective use of the lever action, if the material is the same as the metal plate used as the material in the past, a sufficiently low opening load can be obtained. It is possible to increase the remaining plate thickness of the part. As a result, not only the processing accuracy is improved and the can openability can be stably reduced, but also the inevitable inclusions present in the material metal plate cause cracks in the opening groove. The frequency of occurrence can also be reduced, and the frequency of replacement due to wear of the mold can also be reduced, thereby reducing costs.

The present invention has been made on the basis of the above findings, and the invention according to claim 1 is such that an opening groove is formed on the front surface or the back surface of the can lid, and the tab is centered on the tab stop. In the manufacturing method of the easy-open can lid that is rotatably attached as the opening groove is broken and the can is opened, processing in the region where the plate thickness is t ₀ (mm) and the uniform elongation is 40% to 90% Hardness index n, tensile strength TS (kgf
/ mm ² ), the top and bottom dies of the can lid panel are made of a metal plate that is more than 0.025 mm.
The opening groove is formed by pressing using a pair of molds having a curved surface of 1.0 mm and the other mold being a flat mold, and the can lid panel is subjected to the pressing. The plate thickness t (mm) of the metal plate at the thinnest portion of processing satisfies the following formulas (1) and (2), and the position of the tab stop is the following (3) from the center of the can lid to the opening opposite side. The distance L shown in the formula is shifted, and the length L between the center of the tab stop and the finger gripping part of the tab satisfies the following formula (4), and the center line before rotation of the tab and the center line at the opening position are Angle θ satisfies the following expression (5), and when the tab is rotated to the can opening position on the can lid panel, the slope-like protrusion for raising the tab to a height higher than the winding tightening portion. Is characterized in that 5.0 <P ≦ 7.0 (1) P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln {1+ (tt ₀ ) / t ₀ } |] ⁿ・ ・ ・ ・ (2) (D−d) / 2 <a <d/2−1 ・・・・(3) d−1> L ＞ d / 2 −a ・ ・ ・ ・・ (4) −1 <cos θ <1 / (2 × a × L) × {(d / 2) ² − (L ² + a ² )} ... (5) However, a: of the tab stop center position Displacement distance from the center of the can lid L: Length between the tab fastening center and the tab finger-holding and sandwiching portion l: Length between the tab fastening center and the tab acting portion θ: At the center line and the opening position before the tab is rotated Angle d with the center line: Inner diameter of the can lid D: Outer diameter of the can lid In the invention according to claim 2, grooves for opening are formed on both sides of the can lid, and the tab can rotate around the tab stop. In the method for manufacturing an easy-open can lid which is attached to the opening groove and is opened by breaking the opening groove, the plate thickness is t ₀ (m
m), the work hardening index in the region of 40% to 90% of uniform elongation is n, and the tensile strength is TS (kgf / mm ² ). In each case, the opening groove is formed by pressing using a pair of curved molds having a tip radius of more than 0.025 mm to 1.0 mm, and the can lid panel subjected to the pressing is formed. The plate thickness t (mm) of the metal plate at the thinnest portion of processing satisfies the following formulas (1) and (2), and the position of the tab stop is the following (3) from the center of the can lid to the opening opposite side. The distance L shown in the formula is shifted, and the length L between the center of the tab stop and the finger gripping part of the tab satisfies the following formula (4), and the center line before rotation of the tab and the center line at the opening position are Angle θ satisfies the following formula (5), and when the tab is rotated to the can open position on the can lid panel, Those having features to form a slope-shaped protrusion for lifting above the height of the seam section. 5.0 <P ≦ 7.0 (1) P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln {1+ (tt ₀ ) / t ₀ } |] ⁿ・ ・ ・ ・ (2) (D−d) / 2 <a <d/2−1 ・・・・(3) d−1> L ＞ d / 2 −a ・ ・ ・ ・・ (4) −1 <cos θ <1 / (2 × a × L) × {(d / 2) ² − (L ² + a ² )} ... (5) However, a: of the tab stop center position Displacement distance from the center of the can lid L: Length between the tab fastening center and the tab finger-holding and sandwiching portion l: Length between the tab fastening center and the tab acting portion θ: At the center line and the opening position before the tab is rotated Angle with center line d: Inner diameter of can lid D: Outer diameter of can lid

[0020]

BEST MODE FOR CARRYING OUT THE INVENTION Next, a method for manufacturing an easy open can lid of the present invention will be described with reference to the drawings.

FIG. 1 is a sectional view of an opening groove portion formed in a can lid, showing one embodiment of the method for manufacturing an easy-open can lid according to the present invention. In this embodiment, as shown in FIG. 1, the radius (R) is more than 0.025 mm on the surface 1a side of the can lid 1 with respect to a can lid panel having a thickness t ₀ formed by using a metal plate as a raw material. A 1.0 mm curved mold and a flat mold on the back side are used. The thinnest part 2a has a plate thickness t, and the bottom section has a curved groove 2 for opening.
Are formed by press molding.

At this time, the work hardening index is n, the tensile strength is TS (kgf / mm ² ), and t is 5.0 <in the region of 40% to 90% of the uniform elongation of the metal plate forming the can lid 1. P ≦
7.0 However, P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln
It is formed so as to satisfy {1+ (tt ₀ ) / t ₀ } |] ⁿ .

FIG. 2 is a sectional view of the opening groove portion formed in the can lid, showing one embodiment of the method for manufacturing an easy-open can lid according to the present invention. In this embodiment, as shown in FIG. 2, the surface 1 of the can lid 1 is different from the can lid panel having a thickness t ₀ formed of a metal plate as a material.
On the a side and the back surface 1b side, a die having a curved surface type having a radius (R) of more than 0.025 mm to 1.0 mm is used, and the thinnest part 2a
Has a plate thickness t and the bottom cross section has a curved shape.
Are formed by press molding.

At this time, the work hardening index is n, the tensile strength is TS (kgf / mm ² ), and the t is 5.0 <in the region of 40% to 90% of the uniform elongation of the metal plate forming the can lid 1. P ≦
7.0 However, P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln
It is formed so as to satisfy {1+ (tt ₀ ) / t ₀ } |] ⁿ .

Forming the curved opening groove 2 or the opening grooves 2, 2 having the above-mentioned radius (R) on the front surface 1a or the front surface 1a and the rear surface 1b of the can lid 1, and from the conventional method described later. By attaching the long tab, the can opening force is stably reduced to the extent that even a child or an elderly person can easily open the can, and the occurrence of impact damage is prevented.

Opening groove 2 when forming the opening groove on either the front surface or the back surface of the can lid 1, or both front and back surfaces.
If the radius (R) of the mold for forming the mold is 0.025 mm or less, the machining accuracy of the mold is reduced, and the wear of the mold caused by the molding operation becomes severe, so that a stable opening groove is formed. In order to obtain it, the mold must be replaced in a short period of time, which causes a problem of being uneconomical.

On the other hand, when the radius (R) of the die exceeds 1.0 mm, the area of the thin portion of the can lid 1 becomes large, so that the breaking position of the opening becomes unstable and the opening shape deteriorates. In addition, there is a problem that "drip" in which a part of the broken portion hangs down becomes large, and it is practically difficult to form an opening groove with a width of more than 1.0 mm on the can lid panel in a limited space. Is.

The plate thickness t of the thinnest portion 2a of the opening groove 2 is
Is the work hardening index n and the tensile strength TS (kgf) in the region of 40% to 90% of the uniform elongation of the metal plate forming the can lid 1.
/ mm ² ), 5.0 <P ≦ 7.0, where P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln
It is formed so as to satisfy {1+ (tt ₀ ) / t ₀ } |] ⁿ .

The opening groove 2 is formed by press-molding the metal plate forming the can lid 1 using the mold having the above-mentioned shape. When the metal plate is subjected to such molding. In the thinnest portion 2a obtained by processing, work hardening occurs and the strength increases. The degree of work hardening depends on the ratio between the original plate thickness t ₀ of the metal plate and the processed plate thickness t, and the smaller t is, the stronger the strength of the thinnest portion is. If the equivalent stress of the thinnest portion 2a is σ and the equivalent strain is ε, then σ = K × ε ⁿ (6) 4 of uniform elongation of the metal plate used for the can lid 1
When the work hardening index is n and the tensile strength is TS (kgf / mm ² ) in the range of 0% to 90%, TS = K × n ⁿ / exp (n), K = TS × {exp (n) / (n ⁿ )} ... (7) The strain εts in the plate thickness direction due to the groove forming process for opening is εts = ln {1+ (tt ₀ ) / t ₀ } ... (8) For opening The strain ε corresponding to the thinnest portion of the groove is assumed to be plane strain, and ε = 2 / √3 × | ln {1+ (tt ₀ ) / t ₀ } | ... (9) Equation (6), ( From 7) and (9), the equivalent stress σ of the thinnest portion 2a is σ = TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln {1+ (tt ₀ ) / t _0} |] ⁿ ······ (10) tensile break force P at the time of breaking mainly by tensile deformation the thinnest portion 2a of the opening groove is, P = σ × t ···· ( 11) It is calculated by the following equation (2). P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln {1+ (tt ₀ ) / t ₀ } |] ⁿ ··· (2) Therefore , P can reduce the can opening force, and the effect can be stably obtained when P is 7.0 or less by using the tab attaching method described later together. If P exceeds 7.0, a large can-opening force is required, causing a problem. On the other hand, when P is 5.0 or less, the can opening force is small, but the steel plate thickness t at the thinnest part of the opening groove is as small as that of the conventional technique, so that the machining accuracy is improved and die wear is reduced. Since the effect of is not obtained sufficiently, P <5.0 should be set.

Therefore, either the front surface or the back surface of the can lid,
Alternatively, to form the opening grooves on both the front and back sides, the plate thickness is t
₀ (mm), the work hardening index in the range of 40% to 90% of uniform elongation is n, and the tensile strength is TS (kgf / mm ² ), using a metal plate as the material, and one of the upper and lower molds has a tip radius. A pair of dies with a curved surface die of more than 0.025 mm to 1.0 mm and the other die being a flat die, or a pair of upper and lower dies with a tip radius of more than 0.025 mm to 1.0 mm. The groove for opening is formed by press molding using a mold, and the plate thickness t (mm) of the thinnest processed portion of the can lid panel subjected to press molding is 5.0 <P ≦ 7.0. Where P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln
It is necessary to satisfy {1+ (tt ₀ ) / t ₀ } |] ⁿ .

Next, a method of attaching the tab will be described with reference to the drawings. FIG. 3 is a schematic plan view showing an embodiment of the easy open can lid manufactured by the method of the present invention. In FIG. 3, a is a tab stop 4
Indicates the distance between the center position of and the center of the can lid 1, and L is
The length from the center of the tab retainer 4 to the tip of the finger gripping part of the tab 3 is shown, l is the length between the center of the tab retainer 4 and the action part tip of the tab 3, and θ is the value before rotation. Shows the angle between the tab center line and the tab center line after the tab is rotated and before opening the can, d is the inner diameter of the can lid 1, and D is the can lid 1
Shows the outer diameter of.

In the present invention, the center position of the tab stop 4 is shifted from the center of the can lid 1 to the side opposite to the opening by a in formula (3) below, and (D-d) / 2 <a <d / 2-1. (3) The length L from the center of the tab fastener 4 to the tip of the finger gripping portion of the tab 3 is set within the range of the following formula (4), and is made longer than the conventional one, thereby leveraging the lever. The distance between the fulcrum and the force point in action is made longer, and thereby the generated force at the action point is made larger than in the past. d-1>L> d / 2-a ... (4) However, when tab fastening is applied to the center of the can lid 1 as in the conventional case, the entire tab is placed on the center panel. The cans cannot be stored, and the stackability, storability and transportability of the cans are significantly impaired. Therefore, in the present invention, the position of the tab retainer 4 is displaced from the center of the can lid 1 to the side opposite to the opening within the range of the above formula (3), and the tab 3 is surrounded by the tab retainer 4 as shown in the following (5 ) Is rotated by the amount of θ. −l <cos θ <1 / (2 × a × L) × {(d / 2) ² − (L ² + a ² )} ... (5) Thus, the position of the tab stop 4 is only a. By shifting and rotating the tab 3 by θ, it is possible to fit the entire tab on the central panel portion 7.

Further, at the time of opening the can, as shown in FIG. 4, the tab 3 is rotated from the non-openable position to the openable position around the tab retainer 4. However, by simply rotating, the tab end portion hits the winding tightening portion around the can lid during the rotation, and further rotation becomes impossible. Therefore, by forming the slope-shaped projection 6 on the central panel portion 7 and lifting the end portion of the tab 3 to a height equal to or higher than the height of the winding tightening portion, as shown in FIG. 4, the tab 3 can be opened to a position where it can be opened. It becomes possible to rotate.

In this way, when the tab 3 is rotated to the openable position, the tab-raising side end portion is located outside the outer circumference of the can lid (outer circumference of the winding tightening portion).
It will be easier to pinch your fingers.

In FIG. 3, a rivet is shown as a means for stopping the tab 3 so as to be angularly movable, but the present invention is not limited to this, and a tab fastening member having the same structure is fixed to the central panel portion by another adhering means. May be. As for the shape of the tab 3, it is desirable that the side surface of the tab be raised so that the tab 3 can be easily moved in a corner, so that the finger can be easily held.

The metal plate used in the above-mentioned can lid manufacturing method may be an aluminum alloy plate, a steel plate, or another metal plate, and can be selected according to the purpose. A tab for opening is usually attached to the easy-open can lid, but when a rivet mechanism is used as an attachment method, from the viewpoint of rivet formability, 40% to 90% of the uniform elongation of the metal plate is obtained. It is desirable that the work hardening index n in the region of% is 0.15 or more. Further, when it is necessary to ensure corrosion resistance, either or both of the front and back surfaces of the metal plate may be subjected to various plating or chemical conversion treatment, or may have a resin film formed by painting or laminating.

The manufacturing method of the can lid described above is performed by using the pull-top tab type can lid shown in FIG.
It can be applied to any of tab type can lids.

[0038]

EXAMPLES Next, the present invention will be further described by way of Examples in comparison with Comparative Examples. [Example 1] Plate thickness t ₀ : 0.20 to 0.30 mm, tensile strength TS: 30 to 56 kgf / mm ² , 40% to 90% of uniform elongation
On both surfaces of a thin steel sheet having a work hardening index n of 0.11 to 0.21 in the region of 100 to 12 by chromate treatment.
And 0 mg / m ² in an amount of metallic chromium layer, was prepared tin-free steel chromate film was formed consisting of a hydrated chromium oxide layer in an amount of 14~18mg / m ² in the upper layer of metal chromium conversion.

Thus, tin-free steel having a chromate film on both sides is used as a can lid panel, and both dies have a tip radius of more than 0.025 mm to 1.0 mm.
Curved mold or one mold has a tip radius of more than 0.025mm
Use a pair of dies with a curved surface of 1.0 mm and the other die being a flat die, and apply a lubricant to the steel plate thickness t of the thinnest part so that P is in the range of more than 5.0 to 7.0. Of the Steion tab type obtained by the manufacturing method within the scope of the present invention shown in Table 1, which is pressed with or without use and is attached with the tab 3 having the structure shown in FIG. Easy open can lid (hereinafter referred to as "invention example") No.
1-7 were prepared.

[0040]   The amount of deviation of the center position of the tab fastening from the center of the can lid (a): 5 mm   Length (L) between the tab center and the tab finger gripping part: 25 mm   Length between tab fastening center and tab working part (l): 10 mm   Inner diameter of the can lid (d): 49 mm   Outside diameter of can lid (D): 53 mm

[0041]

[Table 1]

[Example 2] Plate thickness t ₀ : 0.17 to 0.3
0 mm, tensile strength TS: 30 to 50 kgf / mm ² , work hardening index n in the range of 40% to 90% of uniform elongation n: 0.10.
On both sides of the thin steel sheet ～0.21 9 is subjected to a tin electroplating to form a tin plating layer in an amount of 0.8~2.8g / m ^2, on the tin plating layer, the chromate treatment 12 mg / m
And a ^second amount of metallic chromium layer, was prepared an electric tin plated steel sheet a chromate film has been formed consisting of a hydrated chromium oxide layer in an amount of 8-10 mg / m ² in the upper layer of metal chromium conversion.

As described above, an electric tin-plated steel sheet having a plating layer on both sides is used as a can lid panel, and for this can lid panel, both molds are curved molds having a tip radius of more than 0.025 mm to 1.0 mm, or one of them. The mold has a tip radius of more than 0.025mm ~ 1.0mm
Curved surface mold, the other mold is a flat mold, and a lubricant is used so that the steel plate thickness t of the thinnest part is in the range of more than 5.0 to 7.0. Alternatively, a pressing process is performed without use, a tab 3 similar to that of the example 1 of the structure shown in FIG. 3 is attached, and the example of the present invention obtained by a manufacturing method within the scope of the present invention, which is also shown in Table 1, is obtained. Stion tab type easy open can lid Nos. 8 to 12 were prepared.

[Comparative Example 1] Plate thickness t ₀ : 0.30 mm, tensile strength TS: 40 to 56 kgf / mm ² , uniform elongation of 40% to 90
Work hardening index n in the region of%: 0.16 to 0.18
A tin-free steel was prepared by chromating both sides of the thin steel sheet described in Example 1 in the same manner as in Example 1 described above, and thus tin-free steel having a chromate film on both sides was used as a can lid panel. On the other hand, the same die as in Example 1 was used, and the steel plate thickness t of the thinnest portion was subjected to pressing work with or without a lubricant so that P was out of the range of the present invention. Then, a tab 3 similar to that of Embodiment 1 having the structure shown in FIG. 3 is attached, and a Steion tab type easy open can lid (hereinafter, referred to as Table 1) obtained by a manufacturing method outside the scope of the present invention shown in Table 1 is used. Nos. 13 to 15 (referred to as "Comparative Examples") were prepared.

With respect to the above-described can lids of the present invention and comparative examples, the can openability was evaluated by the following, and the results are also shown in Table 1. The openability is measured by measuring the pop value (the initial force at which the opening of the can lid starts to open when the can lid tab is pulled with a certain force), and 6 commercially available aluminum alloy easy open cans are used. Maximum lid pop value (2.4k
g) The following items were marked as ○, and the others were marked as ×.

As is clear from Table 1, Comparative Examples Nos. 13 to 15 formed so that the plate thickness t of the thinnest portion of the opening groove is in the range of P exceeding 7.0 have inferior can openability. Was there. On the other hand, the invention examples Nos. 1 to 12 were all excellent in can openability. The can lids of the present invention example and the comparative example were fastened to the can body, and the can body was dropped from a height of 1 m onto the concrete floor surface in an inclined posture with the can lid facing downward. The presence or absence of impact damage when an impact force was applied to was evaluated, and no impact damage occurred in all the can lids.

[0047]

As described above, according to the present invention,
The can open force is stably reduced, and an easy-open can lid having excellent can open properties that allows even children and the elderly to open can easily is provided, which is an industrially useful effect.

[Brief description of drawings]

FIG. 1 is a cross-sectional view of an opening groove portion formed in a can lid, showing an embodiment of a can lid obtained by a manufacturing method of the present invention.

FIG. 2 is a cross-sectional view of an opening groove portion formed in a can lid, showing another embodiment of the can lid obtained by the manufacturing method of the present invention.

FIG. 3 is a schematic plan view showing one embodiment of a can lid obtained by the manufacturing method of the present invention.

FIG. 4 is a schematic plan view showing one state of the can lid obtained by the manufacturing method of the present invention after the tab rotation and immediately before opening the can.

FIG. 5 is a schematic plan view showing an example of a pull-top tab type can lid.

FIG. 6 is a schematic plan view showing an example of a Steion tab type can lid.

FIG. 7 is an explanatory diagram showing a conventional method for forming an opening groove in an easy-open can lid.

[Explanation of symbols]

1 can lid 2 Opening groove 3 tabs 4 tab closure 5 Breaking opening 6 protrusions 7 Central panel 8 rivet mechanism 9 V-shaped groove 10 Processing tool 11 Lid plate

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Masayoshi Kurihara             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Masahisa Fujikake             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Yoshinori Yomura             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. (72) Inventor Yutaka Mihara             1-2-1, Marunouchi, Chiyoda-ku, Tokyo             Main Steel Pipe Co., Ltd. F term (reference) 3E093 AA02 BB01 CC10

Claims (2)

[Claims] 1. An easy-open can in which an opening groove is formed on the front surface or the back surface of a can lid, and a tab is rotatably attached around a tab stop, and the opening groove is broken to open the can. In the lid manufacturing method, a metal plate having a plate thickness of t ₀ (mm), a work hardening index of n in the region of 40% to 90% of uniform elongation, and a tensile strength of TS (kgf / mm ² ) is formed. One of the upper and lower molds is a curved mold with a tip radius of more than 0.025mm to 1.0mm and the other mold is a flat mold. By forming the groove for opening, the plate thickness t (mm) of the metal plate at the thinnest processed portion of the can lid panel subjected to the pressing process satisfies the following formulas (1) and (2). , The position of the tab stop is shifted from the center of the can lid to the opposite side of the opening by a distance a shown in the following formula (3). The length L between the center of the tab stop and the finger gripping part of the tab satisfies the following formula (4), and the angle θ between the center line before the rotation of the tab and the center line at the opening position is the following (5). Satisfying the formula, and forming a slope-shaped projection on the can lid panel for lifting the tab above the height of the winding tightening portion when the tab is rotated to the can open position. , A method for manufacturing an easy-open can lid having excellent can openability. 5.0 <P ≦ 7.0 (1) P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln {1+ (tt ₀ ) / t ₀ } |] ⁿ・ ・ ・ ・ (2) (D−d) / 2 <a <d/2−1 ・・・・(3) d−1> L ＞ d / 2 −a ・ ・ ・ ・・ (4) −1 <cos θ <1 / (2 × a × L) × {(d / 2) ² − (L ² + a ² )} ... (5) However, a: of the tab stop center position Displacement distance from the center of the can lid L: Length between the tab fastening center and the tab finger-holding and sandwiching portion l: Length between the tab fastening center and the tab acting portion θ: At the center line and the opening position before the tab is rotated Angle with center line d: Inner diameter of can lid D: Outer diameter of can lid 2. An easy-open can lid in which an opening groove is formed on both sides of a can lid, and a tab is rotatably attached about a tab stop, and the opening groove is broken to open the can. In the manufacturing method, a metal plate having a plate thickness of t ₀ (mm), a work hardening index of n in a region of 40% to 90% of uniform elongation, and a tensile strength of TS (kgf / mm ² ) was formed as a material. The opening groove is formed by pressing the can lid panel using a pair of dies whose upper and lower dies are both curved dies with tip radii of more than 0.025 mm to 1.0 mm. The plate thickness t (mm) of the metal plate at the thinnest part of the processed can lid panel satisfies the following formulas (1) and (2), and the position of the tab fastening is set to the center of the can lid. From the opening to the side opposite the opening by the distance a shown in the formula (3) below, and the center of the tab stop and the finger-holding part of the tab. The length L between the two satisfies the following expression (4), the angle θ between the center line of the tab before rotation and the center line at the opening position satisfies the following expression (5), and the can lid panel In addition, when the tab is rotated to a position where it can be opened, a slope-shaped protrusion for raising the tab to a height higher than the winding tightening portion is formed. Manufacturing method. 5.0 <P ≦ 7.0 (1) P = t × TS × {exp (n) / (n ⁿ )} × [2 / √3 × | ln {1+ (tt ₀ ) / t ₀ } |] ⁿ・ ・ ・ ・ (2) (D−d) / 2 <a <d/2−1 ・・・・(3) d−1> L ＞ d / 2 −a ・ ・ ・ ・・ (4) −1 <cos θ <1 / (2 × a × L) × {(d / 2) ² − (L ² + a ² )} ... (5) However, a: of the tab stop center position Displacement distance from the center of the can lid L: Length between the tab fastening center and the tab finger-holding and sandwiching portion l: Length between the tab fastening center and the tab acting portion θ: At the center line and the opening position before the tab is rotated Angle with center line d: Inner diameter of can lid D: Outer diameter of can lid