JPH0581333B2 - - Google Patents

Description

[Detailed description of the invention]

Industrial Application Field The present invention is applicable to the production of packaging containers for foods, cosmetics, electronic parts, etc., using resin-laminated aluminum foil, in which a resin film is laminated on at least one side of the aluminum foil, and using a punch. The present invention relates to a forming method when performing cold stretch forming. Conventional technology Conventionally, the most common wrinkle-free containers for the above-mentioned uses have been deep-drawn products using aluminum foil with a thickness of around 100 μm or synthetic resin molded products. There is. However, the former deep-drawn product not only has poor productivity, but also has the disadvantage of being expensive due to the use of thick foil. Furthermore, the latter resin molded products have the inherent disadvantage of poor barrier properties against moisture, oxygen, light, and the like. Therefore, in order to deal with these problems, recently we have been using resin-laminated aluminum foil, which is made by laminating a resin film on an aluminum foil with a thickness of about 30 to 50 μm, and continuously forming it to a predetermined depth by cold stretch forming. The method of forming containers is attracting attention. In this case, the above molding is required to make the critical molding height as high as possible. As a measure to cope with such demands, it is of course extremely important to select and improve the molding material, but on the other hand, the molding method and molding conditions also have a dominant influence on the molding height. As for the selection of the forming method, vacuum forming, which applies stress uniformly to the entire molding material, or bulge forming using air or oil, etc., are preferable if the purpose is simply to deepen the forming depth, but neither of these methods are suitable for production. It has the disadvantage of being inferior in terms of flexibility and freedom of shape selection. Therefore, as a molding method with excellent productivity, the use of stretch molding using a punch is considered to be the most promising. By the way, in order to achieve the highest possible molding height in stretch molding using a punch,
Generally, it is necessary to give the material good spreadability on the top surface of the punch, that is, the top surface that comes into contact with the molding material, and for this purpose, the top surface should be made with a surface that has as low a coefficient of friction as possible and has good sliding properties. It is said that it is advantageous to make it face up. For example, the material is made of tetrafluoroethylene resin, which has a lower coefficient of friction than when molded using a stainless steel punch, that is, so-called Teflon (product name...the same applies hereinafter).
In general, when molding is performed using a manufactured punch, a relatively higher maximum molding height can be obtained, and therefore it is easier to adapt to changes in container shape and depth, and the molding yield can also be improved. I can do it. Problems to be Solved by the Invention However, when the present inventors conducted various molding tests, they found that even if the punches were made of the same material, the shape of the top surface of the punch, especially the peripheral end, and the difference between the punch body diameter and die diameter It was found that the critical forming height differs depending on the relationship. Based on this knowledge, the inventors conducted numerous experiments and research, and found that in order to increase the forming height as much as possible, the area occupied by the flat part formed at the center of the punch top surface should be It was discovered that there is an appropriate range for the ratio and the shape of the peripheral edge of the top surface, and this invention was completed. Means for Solving the Problems As a premise, the present invention is directed to the case where a resin laminated aluminum foil, in which a resin film is laminated on at least one side of the aluminum foil, is used as a base plate and stretch molding is performed using a punch. In this case, the area of the central flat part of the top surface of the punch occupies a relatively large proportion of 49 to 81% of the area of the entire top surface, and the peripheral edge of the top surface excluding the flat part is The present invention is characterized by using a punch formed in a convex circular arc portion with a curvature corresponding to an inclination angle of 30 to 70 degrees, and whose body diameter is set to be 90% or more of the die diameter. . The resin-laminated aluminum foil used as a base plate is generally made by laminating a resin film made of vinyl chloride resin, polypropylene resin, polyethylene resin, etc. on one or both sides of aluminum foil with a thickness of about 30 to 50 μm. can be,
Stretch molding is performed by bringing the resin film surface side into contact with a punch. As shown in FIG. 2, the punch 1 used in the present invention has an arcuate portion 4b that is inclined toward the punch peripheral side wall 5 at the peripheral edge of the punch surrounding the central flat portion 3 on the top surface 2. It is. In this invention, the area of the flat portion 3 is the area of the entire top surface 2.
49 to 81% (the diameter D3 of the flat part of the top surface is 70 to 90% of the punch body diameter D1), and the arcuate portion 4b at the peripheral edge of the top surface corresponds to an inclination angle of 30 to 70°. It is necessary that the curved surface changes with curvature. Here, the area of the entire top surface refers to the area when the top surface 2 is completely flat, that is, the cross-sectional area of the punch body (diameter D1). In addition, the curvature corresponding to an inclination angle of 30 to 70 degrees refers to the inclination between the tangent C of the arc and the vertical line V at the continuous part P between the flat part 3 and the arc part 4b, as shown in FIG. It means a curvature such that the angle θ' is in the range of 30° to 70° (in relation to the horizontal line, the angle of the tangent C to the horizontal line is 60° to 20°). Area of the flat top portion 3, arcuate portion 4b at the peripheral edge of the top surface
The reason why the inclination angle θ' is defined in the above range is as follows. That is, during stretch forming, the blank first comes into contact with the flat portion 3 of the top surface of the punch. Then, as the punch 1 moves forward, the blank is stretched at the top flat portion 3. As the punch 1 moves further forward, the blank plates gradually come into contact with each other along the top arc portion 4b. When it comes into contact with the arcuate portion 4b, the blank plate is restrained by the frictional resistance of the arcuate portion, and the elongation of the flat portion is suppressed. On the other hand, when the circular arc portion 4b and the blank plate come into contact, the boundary point between the contact portion and the non-contact portion is used as a stress fulcrum, and the portion of the blank plate between the boundary point and the die is stretched. As the punch 1 moves forward and the range of contact with the arcuate portion 4b of the blank plate increases, the fulcrum of stress also moves outward along the arcuate portion 4b.
When the blank reaches its maximum contact with the arcuate portion, the elongation of the blank in the arcuate portion is almost at its maximum, and thereafter the blank is stretched in the clearance between the punch and the die. Therefore, if the area of the flat part 3 is small, the elongation of the blank in the flat part will be small, but if the inclination angle θ' of the circular arc part 4b is too large, the blank plate will not stretch as much as the flat part 4.
b is contacted early, and the elongation of the flat portion is further hindered. Therefore, in this invention, by setting the inclination angle θ' of the circular arc portion 4b to 70° or less, the time until the blank plate comes into contact with the circular arc portion 4b and prevents the blank plate from elongating in the flat portion is delayed. This ensures sufficient elongation of the blank in the flat portion. Furthermore, since the time required for the blank plate to come into contact with the circular arc portion 4b is delayed, the blank plate can be sufficiently stretched even at the circular arc portion. In other words, the area ratio of flat part 3 is 49%
In the above case, if the inclination angle θ' exceeds 70°, sufficient elongation of the blank plate cannot be obtained in either the flat portion 3 or the circular arc portion 4b, and as a result, a large molding height cannot be obtained. Moreover, if the area of the flat part 3 exceeds 81%, the elongation of the blank at the flat part of the top surface will be insufficient regardless of the inclination angle of the arc part, and the arc length of the arc part 4b will become short. , the blank plate and the arcuate portion come into contact early, and the elongation of the blank plate at the arcuate portion cannot be expected. Furthermore, if the inclination angle θ' of the circular arc portion 4b is less than 30°, the inclination of the circular arc portion 4b becomes steep, resulting in a state similar to that of a so-called straight punch without a circular arc portion, causing local stress at the top corner of the punch 1. This will cause it to break easily. Therefore, the area of the flat part 3 is 49 to 81%, and the inclination angle θ' of the circular arc part 4b is
By specifying the angle between 30 and 70 degrees, the flat part 3 of the blank plate
Also, the arc portion 4b can be greatly deformed, and a large molding height can be obtained. A particularly suitable inclination angle θ′ is
It ranges from 40 to 60°. As shown in FIGS. 1 and 4, an attempt has been made to form a tapered portion 4a at the peripheral end of the punch, but the arcuate portion 4b is more sensitive to the blank 20 than the tapered portion.
In order to obtain a larger amount of deformation, the present invention employs the circular arc portion 4b. However, if necessary, as shown in FIG. 3, it is permissible to first form an arcuate portion 4b continuous with the flat top portion 3, and then form a tapered portion 4a following the arcuate portion. Or change the inclination angle to two stages and
The circular arc portion and the second circular arc portion may be combined, or the inclination angle may be successively reduced by three or more steps. Therefore, when the arcuate portion 4b is formed in only one step as shown in FIG. 2, the height of the arcuate portion,
That is, a connecting point P between the top flat portion 3 and the circular arc portion 4b,
The vertical height h of the connection point Q between the punch circumferential side wall 5 and the circular arc portion 4b is preferably set to be equal to or greater than the depth of the final shape of the molded object, such as a container. By doing so, the blank plate of the top surface part can easily flow to the side surfaces, and the stress distribution of the side surface parts can be more averaged, so that a large amount of deformation can be obtained. In this invention, the punch body diameter D1 is specified to be 90% or more of the die diameter D2 because if it is less than 90%, the clearance between the punch 1 and the die 10 becomes large and the effect of providing the circular arc portion 4b is diminished. This is because the condition is similar to that of a straight punch, and the blank plate 20 cannot be deformed sufficiently and, furthermore, cannot be formed to a sufficient height. Here, when the punch is a square punch, the punch body diameter D1 and the die D2 refer to the vertical and horizontal body lengths of the punch and the vertical and horizontal hole dimensions of the die diameter corresponding thereto. Note that the material of the punch used in this invention is not limited in any way, but it is better to use a punch with a small friction coefficient on the top surface, such as a Teflon punch, because the top surface of the punch has a lower coefficient of friction. This is preferable in that it is possible to reduce the sliding resistance and, in turn, to obtain a higher molding height. Effects of the Invention As explained above, the resin-laminated aluminum foil stretch-molding method according to the present invention is as follows:
The area of the central flat part of the top surface of the punch occupies 49 to 81% of the area of the entire top surface, and the area of the peripheral edge of the top surface of the punch excluding the flat part is 30 to 30% in the vertical direction.
A punch that has a convex arc with a curvature corresponding to an inclination angle of 70°, and whose body diameter is set to 90% or more of the die diameter to perform stretch forming of the blank plate. Therefore, it is possible to ensure good elongation of the blank at the top surface of the punch during molding, and the blank can be sufficiently and uniformly deformed. As a result, it becomes possible to increase the molding height, which has the effect of increasing the freedom of molding and improving the molding yield. Example die: Inner diameter D233mm, corner R1mm Molding base plate: Polyester (PET) 16μm/A foil
40μm/Polyvinyl chloride film (PVC) 70μ
m laminated resin laminated aluminum foil wrinkle presser: 1.5 ton In addition to using the above die, molded blank, and wrinkle presser, the body diameter D1, the diameter D3 of the flat part of the top surface, the shape and angle of inclination of the peripheral edge of the top surface, and the taper Using a Teflon cylindrical punch with the vertical height h of the section or arc section varied as shown in Table 1 below,
Stretch molding was performed at a rate of mm/min. In addition, a slight curvature was provided at the corner part of the punch, that is, the tapered part, and each connecting part between the circular arc part and the top surface and the circumferential side wall (for sample No. 1, the connecting part between the top surface of the punch and the circumferential side wall). . Then, the maximum molded height of the obtained container was investigated.
The results are also shown in Table 1.

[Table] As can be seen from the above results, it was confirmed that it is possible to increase the molding height by implementing the present invention.

[Brief explanation of drawings]

Fig. 1 is a sectional view of the main part of the forming device before advancing the punch with a tapered part formed on the circumferential edge of the top surface, Fig. 2 is a sectional view of the main part of the punch with a circular arc part formed on the circumferential edge, Figure 3 is a cross-sectional view of the main part of a punch formed by combining an arcuate part and a tapered part at the peripheral end of the top surface.
The figure is a sectional view of a main part of a punch in which two tapered parts having different inclination angles are formed at the peripheral end of the top surface. 1... Punch, 2... Punch top surface, 3... Flat part, 4b... Arc part, θ'... Inclination angle, 10... Die, 20... Raw plate.

Claims (1)

[Claims] 1. When performing stretch molding using resin laminated aluminum foil as a base plate, in which a resin film is laminated on at least one side of the aluminum foil, the area of the central flat part on the top surface of the punch is equal to or smaller than the area of the entire top surface.
A punch in which a convex arcuate portion with a curvature corresponding to an inclination angle of 30 to 70° with respect to the vertical direction is formed on the peripheral edge of the top surface of the punch, excluding the flat portion. A cold stretch forming method for resin laminated aluminum foil, characterized in that the above forming is carried out using a punch whose body diameter is set to be 90% or more of the die diameter.