JPH0824980B2 - Manufacturing method of metal lid with easy opening and forming tool - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION Industrial Field of the Invention The present invention is used for sealing containers such as beer cans, juice cans, fish cans, etc., and tears and opens a score defining an opening by pulling a tab. The present invention relates to a manufacturing method and a forming tool for a metal lid of a type that easily opens.

(Prior Art) The score that defines the opening of a conventional metal lid that is easy to open is that a metal lid blank is placed on a flat anvil as a whole, and a score forming blade die with an inverted trapezoidal cross section is used as a blank. It was formed by press fitting. FIG. 6 shows a cross-sectional view of a conventional lid 1 which is easy to open near the score 2. The ratio of the thickness of the remaining score thickness portion 3 to the original plate thickness is usually about 0.15 to 0.40. .

Since the score 2 is formed to have a considerable depth as described above while compressing and flowing the metal of the part that should become the score 2 in the direction of the arrow A, the vicinity of the score 2, especially the remaining thickness part 3
The crystal grains of No. 6 expand due to the remarkable plastic deformation, and in these portions, as shown in FIGS. 7 and 8, the fibrous structure 4 (No. 6) in which the original crystal grain boundaries disappeared. Figure) is well developed.

When tearing and opening the score with a tab (not shown), the nose (tip) of the tab is pushed down first, and a force perpendicular to the wall thickness is applied to the remaining thickness part 3 of the score to be initially broken. F is added to break the remaining thickness portion 3 to make a cut, and then the tab is pulled up to open.

As described above, in the lid 1 having the score 2 in which the fibrous tissue 4 is developed in the remaining thickness portion 3 and which is easy to open, the fibrous tissue 4 is significantly increased in strength by work hardening. In addition, since the development direction of the fibrous tissue 4 is substantially perpendicular to the direction of the force F, a large force is required for initial fracture, and it is difficult for the weak person such as an old person or a child to open the mouth. there were.

An inner surface protective film 5 is formed on the inner surface of the metal lid that is easily opened to prevent metal corrosion due to the contents, and an outer surface protective film 6 such as a printed film is formed on the outer surface (sixth).
Figure). Such protective films 5 and 6 have already been formed at the stage of the metal lid blank.

In the case of the conventional method for manufacturing the lid 1 which is easy to open, as described above, the metal in the vicinity of the score 2, particularly the metal in the residual thickness portion 3 is significantly deformed under a relatively large working force, and accordingly, the score 2 is increased.
In particular, the portion 5a of the inner surface protective film 5 below the remaining thickness portion 3 (Fig. 6)
However, the damage is remarkable, such as thinning as shown.
Therefore, the conventional easy-to-open lid has a part 5a after score formation.
Therefore, it was necessary to form a repair protective film in the vicinity thereof and prevent the inner surface corrosion.

Furthermore, in the case of the conventional metal lid 1 which is easy to open, a relatively large processing force is required for score formation, and since the frictional force between the score forming blade die and the metal is large, the blade die is easily worn, and therefore, the forming tool There was a problem that the life was relatively short.

As a method for solving these problems, Japanese Patent Laid-Open No. 62-8484
No. 1 publication proposes a method for manufacturing an easy-open lid, which comprises a first step of imprinting a score on a convex surface of bending deformation while imparting bending deformation, and a second step of correcting the bent portion to a flat plate. There is. However, this method has problems that the remaining thickness cannot be thinned and that the manufacturing cost is high because two steps are required to form the score.

(Problems to be Solved by the Invention) The present invention provides a method of manufacturing a metal lid and a forming tool which are easy to rupture, particularly initial rupture, and have an opening score formed in one step. To aim.

(Means for Solving the Problems) In the method for manufacturing a metal lid which is easy to open according to the present invention, the vicinity is a protrusion, and the protrusion height of the protrusion is smaller than the plate thickness. A method of manufacturing a metal lid, having a trapezoidal cross-section, an elevation angle α of a slope having a protrusion whose opening angle β of each side of a score forming blade die described later is equal to or greater than the flat top of the protrusion. When the metal lid blank is placed on the top and the score die having the score forming blade die arranged at a position facing the top is pushed down to the anvil side on the outside of the portion of the metal lid blank to be the protrusion. Begin pressing the score forming blade into the metal lid blank at substantially the same time, until the lower and upper surfaces of the portion of the metal lid blank adjacent the top portion contact the beveled surface of the protrusion and the score die, respectively. Go and open And forming a use score.

A tool for forming a metal lid that is easy to open according to the present invention is a molding tool for a metal lid that is easy to open and has a projection in the vicinity thereof, and a projection height of the projection is smaller than a plate thickness. A score forming blade die having an inverted trapezoidal cross section and an inclined portion extending diagonally downward provided on both sides of the base portion connected to the base portion of the score forming blade die, and substantially the bottom portion of the score forming blade die connected to the inclined portion. A score die having a pressing surface located on the same plane; and a top having a trapezoidal cross section facing the score forming blade die and having a width larger than the width of the bottom of the score forming blade die, and an inclined surface parallel to the inclined portion. And an elevation angle α of the slope is not less than an opening angle β of each side of the score forming blade die.

(Operation) In the case of the invention according to claim 1, the vicinity of the opening score 22 (hereinafter referred to as the score 22) is the protrusion 26, but since the protrusion height h of the protrusion 26 is smaller than the plate thickness t, The protrusion 26 is inconspicuous and does not need to be flat. If you flatten it,
Since reverse bending is applied, the relatively thin residual thickness portion 13 becomes brittle as will be described later, and is easily cut when flattened, which is not preferable. Therefore, the score can be formed in one step.

Projection of anvil 12 having projection 20 with trapezoidal cross section
Place the metal lid blank 13 on the flat top 20a of 20,
Then, by a score die 11 having a score forming blade die 14 arranged at a position facing the top portion 20a, a metal lid blank is obtained.
When the outer side of the portion of 13 that is to be the protrusion 26 is pushed down toward the anvil 12, the score forming blade die 14 begins to be pushed into the metal lid blank 13 at substantially the same time.

If you continue pushing down, the metal lid blank 13 will
Bending at the boundary (curvature portion 20b) between the flat top 20a and the slope 20c of 20 and on both sides of the score 22 being formed due to this bending, an extension force in the direction of arrow B as shown in FIG. A force acts to separate both sides of the score 22 from each other. Since the top portion 20a is flat, the extension force is relatively small, but the elevation angle α (FIG. 1) of the slope 20c is equal to or larger than the opening angle β of each side of the score forming blade die 14, so that the extension force is The size is large enough to assist in pushing the score forming blade die 14. Therefore, the resistance of the metal to the indentation of the score forming blade die 14 is small, and the indentation of the score forming blade die 14 progresses with a relatively small processing force and a slight plastic deformation of the metal. Therefore, the plastic deformation of the remaining thickness portion is slight, and a work-hardened fibrous structure is not formed.

The pressing is performed until the lower surface and the upper surface of the portion adjacent to the portion on the top portion 20a of the metal lid blank 13 contact the slope 20c of the protrusion 20 and the score die 11, respectively, that is, the adjacent portion is the slope 20c of the protrusion 20. Score die on 11
It is pressed by and is continued until the lowering of the score die 11 is stopped. Therefore, when the formation of the score 22 is completed, the extension force does not act, and the vicinity of the score 22 is pressed and fixed. Therefore, even if the remaining thickness portion 23 is relatively thin, there is no risk of the remaining thickness portion 23 being cut off by an impact or the like applied at the end of score formation. Therefore, it is possible to form a score having a relatively thin residual thickness (for example, when the lid blank is made of steel, the thickness is 45 μm; see the specific example).

As described above, the plastic deformation is slight, the work-hardened fibrous structure is not formed, and a relatively thin residual thickness portion can be formed. Therefore, the score is ruptured at the time of opening, particularly the initial rupture is easy. .

As described above, since the change in the structure of the remaining thickness portion 23 during the formation of the score 22 is slight, the inner surface coating film (5) after the formation of the score 22
Almost no damage. Therefore, it is not necessary to repair the inner coating film near the inner surface portion facing the score.

The invention according to claim 2 relates to a forming tool directly used for carrying out the invention according to claim 1.

The anvil 12 has a trapezoidal cross section facing the score forming blade die 14, and has a protrusion 20 having a top portion 20a having a width larger than the width of the bottom portion 14a of the score forming blade die 14 and a slope 20c. And since the elevation angle α of the slope 20c is not less than the opening angle β of each side of the score forming blade die 14, the trapezoidal cross section, the elevation angle α of the slope is not less than the opening angle β of each side of the score forming blade die 14. The metal lid blank 13 can be placed on the flat top 20a of the projection 20 of the anvil 12 having a projection 20.

The score die 11 is composed of a score forming blade die 14 having an inverted trapezoidal cross section, and inclined portions 16 provided on both sides of the base portion connected to the base portion of the score forming blade die 14, and score formation connected to the inclined portion 16. Since it has the pressing surface 19 located substantially on the same plane as the bottom portion 14a of the blade die 14, the score die 11 having the score forming blade die 14 arranged at the position facing the top portion 20a allows the metal lid. When the outer side of the portion of the blank 13 to be the protrusion 26 is pushed toward the anvil 12 side, the score forming blade die 14 can be pushed into the metal lid blank 13 at substantially the same time.

Further, the score die 11 is connected to the base of the score forming blade die 14 and has the protrusions 20 formed on both sides of the base with slopes 20c parallel to the inclined portions 16, so that the top 20a of the metal lid blank 13 is formed. The lower surface and the upper surface of the portion adjacent to the upper portion are the slope 20c of the protrusion 20 and the slope portion 1
It can be pushed in until it contacts 6).

(Example) In FIG. 1, 11 is a score die, 12 is an anvil, and 13
Is a metal lid blank. The metal lid blank 13 is formed by forming an outer surface protective film and an inner surface protective film, a tin-plated steel plate, a tein-free steel, a disc blank punched from a large metal plate such as an aluminum alloy plate, and a central panel, It is manufactured by forming a chuck wall, a curl portion (not shown), and the like.

The score die 11 is connected to the score forming blade die 14 having an inverted trapezoidal cross section, and each base portion 14c of the blade die 14 via a curvature portion 15, and forms a concave portion 17 having a triangular cross section and extends obliquely downward. ,
And a pressing surface 19 connected to the inclined portion 16 via the curved portion 18. The bottom 14a of the blade mold 14 and the pressing surface 19 are located substantially on the same plane. This is because the pressing of the blade die 14 and the bending of the blank 13 by the pressing surface 19 start at substantially the same time.

The anvil 12 includes a protrusion 20 having a trapezoidal cross section and a base surface 21. The protrusion 20 is provided with a top portion 20a having a width larger than that of the bottom portion 14a of the blade mold 14 (preferably about 3 to 8 times), and a sloped surface 20c connecting to the top portion 20a via a curved portion 20b. The score die 11 and the anvil 12 are attached such that the blade die 14 and the protrusion 20 are opposed to each other with their centers aligned.

The opening angle β of each side portion 14b of the blade die 14 is preferably about 15 to 45.
It is preferable that the elevation angle α of the slope 20c of the protrusion 20 is not less than the opening angle β and not more than about 45 degrees. Further, the slope portion 16 of the score die and the slope 20c of the anvil are substantially parallel to each other (hence the elevation angle θ of the slope portion 16 is substantially equal to α), and the distance d between the two at the end of score formation.
(FIG. 3) is preferably determined so as to be substantially equal to the plate thickness t of the lid blank 13.

Using the score forming tool 10 including the score die 11 and the anvil 12 described above, the score formation of the lid blank 13 is performed as follows.

Place the lid blank 13 on the flat top 20a of the protrusion 20 of the anvil.
After being placed horizontally on top, the score die 11 is lowered as shown in FIG. When descending, the bottom 14a of the blade and the pressing surface 1
9 almost simultaneously contacts the upper surface of the lid blank 13, and thereafter, the pressing of the blade mold 14 and the pressing and bending by the pressing surface 19 simultaneously proceed.

As shown in FIG. 3, the lower surface of the lid blank 13 is an anvil.
When contacting the inclined surface 20c of 12 and the upper surface contacts most of the inclined portion 16 of the score die, the descending of the score die 11 is stopped, and the score 22 having the remaining thickness portion 23 and the protruding portion 26 in the vicinity is The formed metal lid 25 is manufactured.

(Specific example) A lid blank with a diameter of 84.5 mm made of 0.20 mm thick DR8 tein-free steel with a 10 μm thick epoxy phenolic coating film on the outer surface and a 25 μm polyethylene terephthalate film on the inner surface. Like diameter 5
A ring score of 8.3 mm was formed.

The width of the bottom portion 14a of the blade die 14 (made of hard alloy) of the score die 11 of the used score forming tool 10 is 25 μm, the opening angle β is 25 degrees, the height to the base portion 14c is 0.17 mm, and the pressing surface 19 The distance between the end 19a on the blade 14 side and the center line of the blade was 0.45 mm, and the elevation angle θ of the inclined portion 16 was 25 degrees.

On the other hand, the width of the top 20a of the protrusion 20 of the anvil 12 is 150 μm,
The slope α of the slope 20c is 25 degrees, and the radius of curvature of the curved portion 20b is 0.2 m.
m, and the height of the protrusion 20 was 0.20 mm.

Using the above molding tool 10, score 22 (the thickness of the remaining thickness 23
The metallographic microstructure taken in the direction perpendicular to the score 22 in the vicinity of the score 22 of the metal lid 25 on which 45 μm) is formed is shown in FIGS. 4 and 5. Both of them are the structure of the same part after etching with 5% nital for 10 seconds.
FIG. 5 shows a magnification of 450.

For comparison, a metal lid 1 produced in the same manner except that a conventional forming tool having a uniformly flat anvil (the material, shape, dimensions, etc. of the score forming blade die are the same as those of the blade die 14) is used. Figure 7 shows the metallographic structure near score 2 in Figure 7 (magnification
150) and FIG. 8 (magnification 450). Both show the structure of the same part after etching with 5% nital for 10 seconds.

Table 1 shows the results of the metal exposure evaluation test on the inner surface side of the metal lids 25 and 1.

Further, in the case of the conventional forming tool, after making about 500,000 lids, it was necessary to replace it due to the damage of the blade mold, but the forming tool 10 of the present invention shows an abnormality even after making 1 million lids. There wasn't.

Note: * Attach each metal lid to the bottom of the electrolyzer with the lower end open so that the inner surface of the flange is in close contact with the bottom of the side wall of the electrolyzer via seal rubber, and add 1% sodium chloride to the surfactant.
An aqueous solution containing 0.02% was used as an electrolytic solution, with a stainless steel rod as the counter electrode, and at a constant voltage (+ 6.3VDC) for a fixed time (4
Second) electrolyze and measure the electrolysis current at that time. The obtained electrolytic current is called an enamellator value, and this value is proportional to the metal exposed area.

(Effects of the Invention) The method for producing a metal lid that is easy to open according to the present invention has an effect that a metal lid that is easy to open and has a score for opening that is easy to rupture, particularly initial rupture, can be produced in one step.

The method for manufacturing a metal lid that is easy to open according to the present invention allows the remaining thickness of the formed opening score to be relatively thin,
Moreover, the residual thickness portion has a slight plastic deformation, does not form a work-hardened fibrous structure, and has an advantage that the inner coating film near the inner surface portion of the residual thickness portion does not require repair.

In addition to the effects and advantages described above, the metal lid forming tool of the present invention which has an easy opening has the advantage of a long life because the score forming tool has relatively little wear.

[Brief description of drawings]

1, 2, and 3 are longitudinal cross-sectional views of a main part showing a step of forming a score using the forming tool of the present invention.
FIG. 4 shows a state immediately before score formation, FIG. 2 shows a state during score formation, and FIG. 3 shows a state immediately after score formation.
5 and 5 are metallographic micrographs near the score of the metal lid formed by the method of the present invention. FIG. 4 is a photograph with a magnification of 150, FIG. 5 is a photograph with a magnification of 450, and FIG. Fig. 7 and Fig. 8 are vertical sectional views for explaining the vicinity of the score of the lid which is formed by using the flat anvil as an opening easily, and Figs. 7 and 8 are the scores of the conventional metal lid formed by using the flat anvil as a whole. 7 is a metallurgical micrograph of FIG.
The figure is a photograph at a magnification of 450. 10 ... Molding tool, 11 ... Score die, 12 ... Anvil, 13 ... Metal lid blank, 14 ... Score forming blade die, 14a ... Bottom part, 14b ...
Side portion, 16 ... Inclined portion, 17 ... Recessed portion, 19 ... Pressed surface, 20 ... Projection portion, 20a ... Top portion, 20c ... Slope surface, 22 ... Score, 23 ... Remaining thickness portion,
25… Metal lid for easy opening, 26… Protrusion.

Claims (2)

[Claims] 1. A method of manufacturing an easily-openable metal lid having a protrusion in the vicinity thereof, the protrusion height of the protrusion being smaller than the plate thickness, wherein the metal lid has a trapezoidal cross section and an elevation angle of a slope. An anvil having a protrusion in which α is equal to or larger than the opening angle β of each side of the score forming blade die described later, a metal lid blank is placed on the flat top of the protrusion, and at a position facing the top. With a score die having a score forming blade die arranged,
A portion adjacent to the portion on the top of the metal lid blank at substantially the same time when the outer side of the portion of the metal lid blank to be the protrusion is pushed down toward the anvil side, and the score forming blade die starts to be pushed into the metal lid blank. A method of manufacturing a metal lid with an easy opening, characterized in that the above-mentioned pressing is performed until the lower surface and the upper surface of the metal plate come into contact with the slope of the protrusion and the score die, respectively, to form a score for opening. 2. A score forming blade having an inverted trapezoidal cross-section, which is an easy-to-open metal lid forming tool having an opening score whose projection height is smaller than the plate thickness, in the vicinity of which is a protruding portion. Mold and the score-forming blade die, the inclined portions provided on both sides of the base portion connected to the base portion, and the pressing surface located substantially on the same plane as the bottom portion of the score-forming blade die connected to the inclined portion And a top having a trapezoidal cross-section facing the score forming blade die and having a width larger than the width of the bottom of the score forming blade die, and an anvil having a protrusion formed with a slope parallel to the inclined portion. Included: A metal lid forming tool with easy opening, wherein an elevation angle α of the slope is equal to or larger than an opening angle β of each side of the score forming blade die.