JPH0759330B2 - Method for forming neck-in part of seamless can - 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 forming a neck-in portion at the opening end of a seamless can used for carbonated beverage cans, beer cans, etc. by a die molding method, and more particularly to The present invention relates to a method for forming a neck-in portion that is extremely thin and suitable for high-speed molding.

[0002]

2. Description of the Related Art Generally, a neck-in portion is formed on an opening end of a metal can body by a die forming method, and an outer tool mainly consisting of a guide ring and a necking die and an inner tool mainly consisting of a center core and an adapter (see FIG. 1). )
At the same time as approaching the bottom of the metal can and squeezing the opening end with a necking die so that the end face of the opening end comes into contact with the stepped portion of the adapter (see 8a in FIG. 1) or immediately before the contact. Then, the internal tool is stopped and only the external tool is continuously approached to form a neck-in portion including a neck portion (reduced diameter portion) and a shoulder portion (for example, JP-A-57-160).
527). FIG. 4 shows an example of the cam curve of the circumferential cam that engages with the cam rolls that drive the external tool and the internal tool in this case.

In FIG. 4, curves a'and b'represent cam curves for an external tool and an internal tool, respectively. As the level of each curve decreases, each tool approaches the bottom of the can. When the cam angle is about 30 degrees a'1, draw forming is started and the curve cam a'reaches the lowest level a '
The molding is completed at 2 (cam angle of about 70 degrees).

In order to reduce production costs, the thickness of the barrel wall of a seamless can has become thinner and thinner (for example, about 0.1 mm for an aluminum can and about 0.08 m for a steel can).
m), and the necking speed is getting faster (for example, about 100).
0-1500 cans / minute). Therefore, in the conventional neck-in portion forming method, there is a problem that the body wall portion is likely to buckle due to an impact axial load applied during forming. In particular, when the body wall is extremely thin as in the above example, a minute recess is likely to be formed in the body wall by a slight impact during transfer to the necking device, and this recess serves as the starting point. It is easy to induce buckling.

[0005]

DISCLOSURE OF THE INVENTION The present invention has an opening of a seamless can, in which even if the wall of the seamless can is extremely thin and the necking speed is extremely high, buckling of the wall does not easily occur. It is an object of the present invention to provide a method for forming a neck-in portion on an end portion.

[0006]

A method for forming a neck-in part of a seamless can according to the present invention is to bring a bottom part of a seamless can and a necking die close to each other, and squeeze the opening end of the seamless can with the necking die to form a neck-in part. In the method of forming a sheet, the approach is stopped or delayed for a short time at the beginning of the throttle at the opening end, and pressurized gas is introduced into the seamless can at least between the beginning of the throttle and the end of molding. Is characterized by.

[0007]

When the pressurized gas is introduced into the can to increase the pressure inside the can, a force outward in the radial direction acts on the body wall, so that buckling does not occur easily. Further, the recess also disappears at least during the molding due to the above force, so that buckling does not easily occur from this point as well. That is, as the internal pressure of the can increases, the axial load resistance strength of the barrel wall increases.

In general, the axial load applied to the body wall increases sharply during the period from the start of the throttle at the opening end until the end face collides with the center core (between the points in FIG. 3). Buckling occurs when the axial load exceeds the axial load strength of the body wall. When the opening end is sealed by a necking die, the approach is stopped or delayed for a short time at the beginning of the throttle, and when pressurized air is introduced, the internal pressure of the can rises rapidly and the axial load resistance of the barrel wall is increased. Strength increases. Therefore, even when the necking speed is extremely fast, for example, about 1000 to 1500 cans / minute, and the body wall is extremely thin, buckling can be prevented by appropriately setting the stop period or the delay period.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS In FIG. 1, 1 is a seamless can and 2 is a neck-in part 15 (see FIG.
), Which is provided with an outer tool 3 mainly composed of a guide ring 4 and a necking die 5, and an inner tool 6 mainly composed of a center core 7 and an adapter 8. The internal tool 6 is provided with a guide hole 9 that connects to a source of pressurized air (not shown). Reference numeral 10 is a chuck (schematic) for holding the bottom portion 1b of the seamless can 1, and 11 is a vacuum suction hole for connecting the bottom portion 1b to the chuck 10 by vacuum suction, which is connected to a vacuum source (not shown).

The external tool 3 and the internal tool 6 are respectively
It is configured to reciprocate horizontally (left and right in the figure) by a cam roll (not shown) that engages a circumferential cam (not shown) having the cam curves a and b shown in FIG. In FIG. 2, the decrease in level indicates that the tools 3 and 6 approach the bottom 1b of the seamless can 1, that is, the chuck 10 (hereinafter referred to as forward movement). Necking tool 2 and chuck 10 each include a turret (not shown) that rotates about a horizontal axis.
A plurality of (for example, 10) peripheral members are circumferentially provided, and the circumferential cam is provided on the fixed frame in parallel with the turret. When the seamless can 1 is gripped by the revolving chuck, the cam angle is 0 degree.

FIG. 1 shows a state in which the necking die 2 is advanced and the molding of the neck-in portion is about to start. At this time, the cam angle is 15 degrees, and as can be seen from FIG. Up to this point, the outer tool 3 and the inner tool 6 advance toward the seamless can 1 at the same speed. After that, the external tool 3 moves forward at a slightly faster speed,
The open end 1a is guided by the guide ring 4 and the tapered portion 5c of the necking die 5 and the circumferential line 5c1 (see FIG. 2).
Contact with the inner tool 6 while the seamless tool 1
Enter inside. The internal tool 6 stops at the time of b1 when the cam angle is approximately 40 degrees.

At the time point a1 when the opening angle 1a is sealed by contacting the tapered portion 5c of the necking die 5 and the cam angle is approximately 30 degrees, the pressurized air 12 passes through the guide hole 9 and enters the seamless can 1. be introduced. At the time point a2 (cam angle is approximately 45 degrees; FIG. 2,) at which the opening end 1a is slightly squeezed so as to prevent buckling of the body wall 1c and the sealing performance is secured.
Therefore, the pressure in the seamless can 1 is within a predetermined range value (usually 1
~ 4 kgf / cm ² ) at time point a3 (cam angle is approximately 6)
The external tool 3 is stopped for a short time until 0 degree). After that, the external tool 3 moves forward again, the aperture of the opening end portion 1a advances, and FIG.
As shown in, the end surface 1a1 is the peripheral surface 7 of the center core 7.
When it collides with a (when the cam angle is approximately 72 degrees and 30 minutes), the formation of the neck portion starts immediately, and as shown in FIG. 1, the portion near the end face is inverted and the end face 1a1 is the cylinder of the necking die 5. It contacts the die surface 5b (FIG. 1).

When the external tool 3 advances until it reaches the minimum level a4 of the cam curve a (cam angle is almost 100 degrees),
As shown in FIG. 1, a neck portion 14 having a predetermined height is formed, and a neck-in portion 1 having a shoulder portion 13 and a neck portion 14 is formed.
5 is formed. At this point, the introduction of the pressurized air 12 is stopped. Thereafter, while the internal tool 6 is stopped, the external tool 3 moves backward, and when the cam angle is about 140 degrees (b2), the internal tool 6 also starts moving backward, and the seamless can 1 with the neck-in portion 15 formed is necked. The outer tool 3 and the inner tool 6 are separated from the tool 2 until the cam angle reaches 180 degrees.
Returns to the position where the cam angle is 0 degrees and stops. It should be noted that the inner tool 6 may start the retreat first while the neck portion 14 is being formed by the forward movement of the outer tool 3.

Curve 17 in FIG. 3 shows the forming height (open end 1
It shows an example of the relationship between the axial height of the molded portion of a) and the axial load applied to the barrel wall portion 1c of the seamless can 1. The points ,,, and shown in the curve 17 correspond to the states ,,, and of FIG. 1, respectively. The axial load sharply increases during the period from the point where the opening end portion 1a is narrowed by the drawing surface 5a of the necking die 5 to the point, particularly in the latter period, and then decreases slightly at the point and then rises to almost the point value again. , Slightly decreases in the process of forming the neck portion 14.

Therefore, when the body wall 1c is extremely thin, buckling is likely to occur in the latter half of the drawing process. However, as described above, the pressurized air 12 is introduced into the can during this period. Since the axial load resistance strength of the body wall portion 1c is larger than the axial load at the point, buckling is unlikely to occur.

Specific examples will be described below. The outer diameter of the body wall portion 1c is 66 mm, the average thickness is 0.089 mm, and the total height is 1.
Seamless can 1 made of 23.75 mm tin-plated steel sheet
The neck-in portion 15 was formed at a speed of 1000 cans / minute by using the necking tool 2 of the type shown in FIG. 1 driven by the cam mechanism having the cam curves a and b shown in FIG. The shoulder 13 of the neck-in portion 15 has an axial height of about 4 mm, and the neck portion 14 has an axial height of about 16 m.
m, and the outer diameter was 63.2 mm.

In this case, the cam angle at which the end face 1a1 of the opening end 1a starts contacting the necking die 5 is about 3.
The cam angle at the time of colliding with the peripheral surface 7a of the center core 7 at 0 degree was 72 degrees and 30 minutes, the moving cam angle of the cam roll during that time was 42 degrees and 30 minutes, and the time was 0.071 seconds. . The source pressure of the pressurized air source was 3 kgf / cm ² , and the pressurized air was introduced from the time shown in FIG. 1 to the end of molding. Although it is difficult to measure the can internal pressure during molding, the can internal pressure at the time of the above end face collision (at the time of Fig. 1) estimated from the amount of air used and experimental data is about 1.8 kg.
It becomes f / cm ² . Molding was performed on 100,000 cans, but the number of buckled cans was 0.

For comparison, molding was carried out in the same manner as described above except that the necking tool 2 was driven by a cam mechanism having cam curves a'and b'shown in FIG. In this case, the end face 1a1 of the opening end 1a is the necking die 5
The cam angle at the time of starting contact with is about 30 degrees, and the cam angle at the time of colliding with the peripheral surface 7a of the center core 7 is about 33 degrees.
0 minute, the moving cam angle of the cam roll during that time is 3 degrees and 30 minutes, the time is 0.0058 seconds, and the estimated can internal pressure at the time of end face collision is about 0.15 kgf / cm ² . 5
Molding was performed on ten thousand cans, but 22 cans were buckled. For comparison, the molding was carried out in the same manner as described in the paragraphs 16 and 17, except that the pressurized air was not introduced. The individual buckled.

The present invention is not limited to the above embodiment, for example, the pressurized air may be blown out before the molding by the necking die 5 is started, and the blowout is continued until after the molding is completed. Good. In addition, as long as the internal pressure of the can increases to such an extent that buckling of the barrel wall does not occur, the advancing speed of the external tool 3 during drawing is delayed as shown by the dotted line portion a _x of the cam curve a in FIG. Good. When making a multi-stage neck can such as a double neck can or a triple neck can, a seamless can with a neck-in part is formed.
The method of the present invention may be repeated once or twice with the neck-in portion as the open end.

[0020]

The method of forming the neck-in portion at the open end of the seamless can according to the present invention allows the seamless can to have a very thin neck wall even when the necking speed is extremely high. This has the effect that buckling is unlikely to occur.

[Brief description of drawings]

FIG. 1 is a longitudinal sectional view of an essential part showing a step in an embodiment of a method of the present invention.

FIG. 2 is a diagram showing an example of a cam curve of a cam mechanism that operates the necking tool of FIG.

FIG. 3 is a diagram showing an example of a relationship between a forming height and an axial load during formation of a neck-in portion.

FIG. 4 is a diagram showing an example of a cam curve of a cam mechanism that operates a necking tool in the case of a conventional method.

[Explanation of symbols]

 1 Seamless can 1a Open end 1b Bottom 5 Necking die 12 Pressurized air 15 Neck-in part

Claims (1)

[Claims] 1. A method for forming a neck-in portion by bringing a bottom of a seamless can and a necking die close to each other, and squeezing an opening end of the seamless can by the necking die to form the neck-in portion in the initial stage of the squeezing of the opening end for a short time. Is stopped or delayed, and a pressurized gas is introduced into the seamless can at least between the initial stage of the drawing and the end of molding.