JP3279887B2 - Method for manufacturing lid with excellent openability - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for manufacturing an easy-open can lid which can easily open a part of a can lid by hand, and is used for a wide range of can lids such as beverage cans, general food cans and the like. .

[0002]

2. Description of the Related Art Conventionally, an easy-open can lid, which can easily open a part of a container lid by hand, places a lid body on a flat lower mold and presses a sharp blade having a required contour shape from the upper surface thereof. Then, by cutting the cutting edge into the lid body, a cutting guide groove having a V-shaped cross section was formed, and an opening piece shape was obtained. However, in this method, since the cutting edge is sharp, the coating film applied in advance is destroyed for anticorrosion, and in the case of a steel lid, repair painting is required thereafter, which increases the production cost. On the other hand, recently, as a measure for repair, a resin coating has been partially used instead of the conventional coating. Since the resin film has relatively excellent ductility, it does not break depending on the processing method, and there is a possibility that the opening piece can be processed. However, when the cutting guide groove having the V-shaped cross section is formed by the sharp blade described above, it is not possible to avoid the breakage of the resin film.

As an alternative to the method of pressing the sharp blade,
The JP 5 5 -70,434 discloses a method which constitutes a cutting guide groove by the composite extrusion are proposed. However, this known technique is based on the assumption that a steel plate is used, and forms a V-shaped cutting guide groove by bending the middle between the can lid and the opening. Therefore, when applied to a resin-coated steel plate, there is a problem that the resin coating is broken at an acute angle portion of the cutting guide groove.

Therefore, a part of the present inventor has disclosed in
Japanese Patent No. 0472 proposes a method of manufacturing a lid having excellent openability by limiting the shoulder radius of the upper and lower dies for forming the cutting guide groove and the remaining thickness of the cutting guide groove after processing. Further, in the detailed description of the invention of the same publication, it is mentioned that it is advantageous to open the can to perform a push-back process to reduce a step generated between the lid main body and the opening. However, simply pushing back does not only improve the openability of the can, but also often causes breakage of the resin film, and requires a push-back process suitable for the processing condition of the guide groove in the opening. It became clear that it was. In particular, it has been clarified that the relationship between the die and the punch clearance at the time of processing the opening, which is not mentioned at all in JP-A-6-170472, is important.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a lid which is free from breakage of a resin film during the above-mentioned push-back processing and has excellent can-openability.

[0006]

The gist of the present invention is that P, S
n on both sides of a steel sheet containing 0.01 to 0.2% by weight of one or both of the above-described thicknesses, a thickness of 10 to 100 μm,
% When forming a cutting piece by providing a cutting guide groove in a steel can lid having a resin coating of 0.1% or more.
A punch and a die having a shoulder radius of about 1.6 mm are used, and the can lid is pressed by the punch and the die shoulder within a range of -1.6 to 0.3 mm for the clearance between the punch and the die. After providing a concave opening piece having a cutting guide groove forming portion with a minimum remaining thickness of 100 μm or less, the concave opening piece with a step t is pushed back against the can lid body by a punch to obtain a 0.3 × t to 1.5 × t. This is a method for producing a lid having excellent openability, characterized in that the lid is extruded within the range. At the time of the push-back processing, the opening piece and the push-back punch are preferably locked by beads to prevent a gap between them. In the present invention, the steel sheet refers to an original plating sheet, tin,
It refers to those that include steel plates whose surfaces are plated with nickel, chromium, or the like.

[0007]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The point of the present invention is to reduce the remaining thickness of a cutting guide groove without breaking a thin resin film,
In addition, the thinned portion is reworked to be embrittled and shaped so that stress concentration occurs.
Thus, in the present invention, a base steel plate constituting a can lid and a film resin coated thereon are specified. First,
The steel sheet serving as the base material has one or both of P and S of 0.01.
It is a low carbon steel sheet containing up to 0.2% by weight. It is preferable that the lid is made of a material that is easily opened when the can is opened due to processing embrittlement in forming the cutting guide groove. To this end, the addition of grain boundary segregation elements is effective, and P and Sn are particularly effective. In order to make the effect of processing embrittlement apparent,
One or both of P and Sn must be at least 0.01%. On the other hand, if the amount is too large, breakage may occur during molding of the cutting guide groove, so the upper limit is made 0.2%. The base steel sheet is usually plated with tin, nickel, chromium or the like on the surface in order to provide corrosion resistance as a container lid.

Next, the coating resin of the can lid has a thickness of 10 to 10
One having a thickness of 0 μm and a breaking elongation of 100% or more is used. If the thickness is less than 10 μm, the resin may be too thin during processing and may be broken. If the thickness is more than 100 μm, the resin may not be sufficiently broken at the time of opening and may not have sufficient openability. Also,
If the elongation at break is less than 100%, the steel sheet may break without being able to follow the deformation of the steel sheet during processing. The type of the resin may basically satisfy the above characteristics, and for example, a single or a mixture of polyethylene, polypropylene, polyester, polyamide, ionomer and the like can be used.

Next, a method of forming a cutting guide groove will be described. FIG. 1 shows an example of a can lid, in which a lid body 1 and an opening piece 2 are provided.
In the first process, as shown in FIG. 2, the lid main body 1 made of the resin-coated steel plate 4 and the punch die 5 having the punch shoulder radius 9 are formed. Press working is performed with a die 6 having a die shoulder radius 10. In processing, to avoid contact of the tool with an acute angle to the resin coating and to prevent stress concentration due to the processing from occurring, the radius of the shoulders 9 and 10 of the die and punch must not be too small. is necessary. On the other hand, if the radius is too large, a large force is required to reduce the thickness of the cutting guide groove forming portion 13 , and the risk of breaking the resin film due to the compressive force increases. Therefore, the radii 9, 10 of the shoulders of the die and the punch are set to 0.1 to 1.6 mm.

[0010] As a result of systematically examining a method of effectively reducing the thickness of the cutting guide groove forming portion without breaking the resin film, it has been found that processing that appropriately combines compression, tension, and shearing is effective. It turned out that there was. Such processing was achieved by limiting the clearance between the punch 5 and the die 6 to -1.6 to 0.3 mm. That is, if the thickness is less than -1.6 mm, the compressive stress necessary for reducing the thickness becomes too large. If the thickness is 0.3 mm or more, the clearance is too large to reduce the thickness due to compression, and fracture occurs due to tension.

The remaining thickness of the cutting guide groove forming portion processed under the above conditions is 100 μm or less as a minimum thickness. If the minimum remaining thickness is larger than 100 μm, it becomes impossible to open the can, so the thickness is set to 100 μm or less, preferably 60 μm or less. The lower limit of the minimum remaining thickness is appropriately selected depending on the conditions of use of the container. However, if the thickness is too small, the risk of breakage when the container is dropped increases, so the lower limit is preferably set to 20 μm. The processed opening piece 2 has a concave shape with a step t with respect to the lid main body 1 as shown in FIG.
Then, the concave opening piece 2 is then pushed back to obtain the final shape of the cutting guide groove, and stress concentration occurs in the cutting guide groove at the time of opening the can to facilitate opening of the can.

In the push-back process, as shown in FIG. 3, the opening piece 2 of the can lid is sandwiched between the mold 7 and the push-back punch 8, and the push-back punch 8 pushes back. Regarding the amount of push-back at that time, if the amount is too small, the required opening property cannot be obtained, so the amount of push-back processing is required to be 0.3 times or more of the step generated between the lid body and the opening piece by press working. is there. But,
If the amount is too large, the risk of breakage of the opening at the time of reworking increases. In addition, at the time of 1 time, a lid main body and an opening piece become the same height.

At the time of pushing back, as shown in FIG. 3, for example, a convex bead 11 is formed in advance in the opening piece, and a concave bead is provided in a position corresponding to the bead also in the pushing back punch. The bead acts as a lock when pushed back, so that the punch and the lid can be prevented from being displaced. When the opening piece obtained as described above is broken by opening the can, the broken lid body is injured when the mouth is hit, as shown in FIG. 4, since the broken surface faces the inner surface of the can. Safe without any. That is, FIG. 4 is a diagram showing a cross-sectional shape before and after the opening of the can lid opening piece, FIG. 4 (a) showing before the opening, and FIG.

[0014]

The present invention will be described in more detail with reference to examples.
You. 0.2 mm thick having a steel composition as shown in Table 1.
2-3 g / m on steel plate ^Two Electric tinplate
And then reflow the tin and then chromate
Was. These steel sheets were reheated and the resin
Lum was bonded to both sides to obtain a can lid material. Next, FIG.
2 and 3 to form a can lid as shown in FIG.
The above material was pressed using a mold. Mold at that time
Table 3 shows the conditions and processing conditions. And shape the opening piece
After completion, the QTV value and the opening force are evaluated, and the results are
The results are shown in Table 3.

[0015]

[Table 1]

[0016]

[Table 2]

[0017]

[Table 3]

The QTV value is a current value when the lid is immersed in a saline solution containing a surfactant and a voltage of 6 V is applied for 1 minute, and it is possible to evaluate the damage of the resin film by this value. If it is 1 mA or less, it can be determined that the film is not broken. The can opening force was determined by measuring the maximum force at the time of opening the stainless steel can. The mark x in Table 3 indicates that the can was not opened. Experiment No. in Table 3 1 to 19 show the influence of molding conditions. Experiment No. 20 to 23 show the influence of the resin. Experiment No. 25 to 31 show the influence of the lid material. In addition,
Negative clearance means that punch and die overlap. Experiment No. of the present invention example. 1,2,3,5,6,
8, 9, 11, 13, 15, 17, 18, 20, 21,
24, 25, 27, 29, and 30 all have a QTV value of 1 mA or less, have no coating breakage, and have a can opening force of 20 N or less, confirming that they can be easily opened manually.

On the other hand, in Experiment No., the radius of the shoulder of the die and the punch was smaller than the range of the present invention. 16, the coating is destroyed,
It showed a high QTV value. In Experiment No. in which the shoulder radius was too large. In No. 19, since a large compressive stress was applied to reduce the remaining thickness of the cutting guide groove forming portion, the coating was damaged. In Experiment No. in which the clearance was larger on the minus side than the range of the present invention. In No. 4, the compressive stress applied to the resin film was too large, and the resin was broken. In Experiment No., the clearance was too large on the plus side. 7 is the first processing
Breakage occurred before the thickness of the cutting guide groove forming portion was reduced to 100 μm or less. Furthermore, in Experiment No. where the amount of pushback was small. No. 12 did not open. Conversely, in Experiment No. in which the pushback amount was too large. In No. 14, a break occurred at the cut guide groove forming portion during the push-back processing. And cutting guide groove shape
Experiment No. in which the minimum thickness of the formed part was 100 μm or more. 1
In the case of No. 0, the tap did not open in the stain-opening method, and the can was not opened.

Next, in Experiment No. 1 in which the resin film was thick. 22
However, in the case of the stain-opening method, the tap did not open because the tap was loose. In Experiment No. in which the resin film was thinner than the range of the present invention. In No. 23, the resin was broken during the processing of the guide groove. Experiment No. Reference numeral 24 indicates that the opening piece is not displaced in the horizontal direction with respect to the punch at the time of the push-back processing by using the bead of the opening piece. In this case, the shape of the guide groove becomes uniform, so that the opening force is slightly reduced. Was completed. Regarding the steel composition of the base metal, Experiment No. 1 using a material to which P was added in a small amount was used. In the case of 26 and 28, in the former case, the tap was depressed in the stain-opening method and the can was not opened, and in the latter case, the opening force was high and there was a problem in the opening property. Experiment No. 1 using material H to which P and Sn were added in large amounts. In No. 31, fracture occurred before the thickness of the cutting guide groove forming portion was reduced to 100 μm or less in the first processing.

[0021]

According to the method of the present invention, a steel can lid having excellent openability and corrosion resistance can be obtained, and all-steel with the can body can be achieved. Occasionally it becomes monometal, and a high recycling rate can be expected as an environmentally friendly product.

[Brief description of the drawings]

FIG. 1 is a diagram showing an example of a can lid after processing;

FIG. 2 is a diagram showing an example of press working of the present invention;

FIG. 3 is a diagram showing an example of a push-back process;

FIG. 4 is a view exemplifying a cross-sectional shape before and after opening of a can lid opening piece.

[Explanation of symbols]

1 fracture radius 1 1 bead 1 2 aperture radius 1 0 die shoulder of the lid body 2 mouthpiece 3 push back the cutting guide groove 4 resin-coated steel plate 5 punch die 6 die base 7 mold B 8 Po inch 9 punch shoulder Cross section 1 3 Cutting guide groove forming section

──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-6-122438 (JP, A) JP-A-9-108756 (JP, A) JP-A-9-108757 (JP, A) JP-A-51-108 63786 (JP, A) (58) Field surveyed (Int. Cl. ⁷ , DB name) B21D 51/44 B65D 17/28

Claims (2)

(57) [Claims] 1. One or both of P and Sn are set to 0.01 to
A thickness of 10 to 100 on both sides of a steel sheet containing 0.2% by weight.
μm, a steel can lid having a resin coating with a breaking elongation of 100% or more is provided with a cutting guide groove to form an opening piece.
First, a punch and a die each having a shoulder radius of 0.1 to 1.6 mm were used, and the clearance between them was -1.6.
The can lid is pressed by the punch and die shoulders within a range of ~ 0.3 mm, and the minimum remaining thickness of the pressed portion is 10 mm.
After providing a concave opening piece having a cutting guide groove forming portion of 0 μm or less, the concave opening piece of the step t is pushed back to the can lid body within a range of 0.3 × t to 1.5 × t by a punch. A method for producing a lid with excellent openability, characterized by processing. 2. The method according to claim 1, wherein the opening piece and the push-back punch are locked with a bead during the push-back processing.