JPS637862B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention relates to a method for manufacturing a thin-walled metal pressure-resistant container suitable for containing a pressurized liquid such as beer, and particularly having a medium capacity of about 1 to 3. Conventionally, aluminum or stainless steel metal containers and glass bottle containers have been used to store and transport pressurized liquids such as beer, but among these containers, aluminum containers do not impair the taste of the contents. It is well known that in recent years it has been manufactured in large quantities as one-way (disposable) beer containers, etc., as it is excellent in terms of lightness, cooling performance, and ease of handling. be. However, this type of one-way container needs to be manufactured as cheaply as possible and in large quantities, so if a special processing method is used, such as a regular DI can with a capacity of 350 ml or less, for example, one-way containers with a capacity of 1 to 3
Even for medium-capacity containers, it is necessary to use manufacturing methods that are as inexpensive and efficient as possible. However, since such containers are generally compared based on weight or price per unit capacity, it is important to consider methods of integrally molding them from a single member, such as the impact method or casting method. However, these methods have drawbacks such as increased man-hours and increased plate thickness (i.e., product weight), and as a result, they are disadvantageous when applied to medium-capacity one-way containers such as those mentioned above, and inevitably There is no choice but to adopt a method in which two cup-shaped pieces (cup-shaped members) formed from thin metal plates (particularly thin aluminum plates) are joined at their respective open ends. The joining method is adhesive bonding, which allows for thinner plate thickness than welding, which takes a lot of man-hours, or seaming, which generally has a limit on the minimum plate thickness due to the strength of the joint. It is desirable to adopt this method. However, when bonding two such thin cup-shaped pieces together, there are several problems that must be solved. One of them is that the joint must have sufficient resistance to internal pressure and external pressure including impact force, and the joint must be a circumferential joint between open ends. This means that the bonding area generally becomes larger, and in this respect, it is necessary to select a method that shortens the bonding cycle as much as possible. Another is to avoid forming a protrusion such as a flange at the joint in order to avoid increased costs due to excessive use of packaging materials such as cardboard. The most important problem is that this type of one-way container usually has a fairly narrow inner diameter of the entrance and exit of the contents, about 20 to 40 mm, considering its intended use. It is difficult to apply sufficient adhesive pressure from the inner and outer surfaces. The present invention is a method of manufacturing a pressure-resistant container by fitting and bonding the open ends of first and second cup-shaped pieces made of thin metal, and which solves some of the above-mentioned problems. The feature is that a small-diameter stepped portion is formed at the open end of the second cup-shaped member, a hot melt adhesive is supplied to the outer peripheral surface of the stepped portion, and the open end of the first cup-shaped member is connected to the second cup-shaped member. The small-diameter stepped portion of the second cup-shaped member is fitted from the outside, heated so that the temperature of the stepped portion of the second cup-shaped member is higher than the temperature of the fitted portion of the first cup-shaped member, and then The purpose is to quickly cool the first cup-shaped member. The present invention will be described below based on embodiments shown in the accompanying drawings. FIG. 1 is a partially vertical front view of a thin-walled metal pressure-resistant container for draft beer having a capacity of about 2, for example, a thin-walled aluminum pressure-resistant container according to the present invention, and 1 and 1' are epoxy resin containers with a thickness of 3 to 4 μm on both sides. The first and second cup-shaped members (pieces) are made by compression molding thin aluminum plates with a thickness of 0.25 mm coated with a lubricating film such as resin into cup shapes with an inner diameter of 120 mm and depths of 80 mm and 120 mm.
The first piece 1 is integrally formed with a liquid inlet/outlet 2 with a height of 20 mm, and the open end of the second piece 1' has a hole with a diameter smaller than that of the body 1'a, for example, a width If l ₁ is 10 mm, the body 1' is equal to the plate thickness t (0.25 mm).
Small diameter stepped portion 3 with a smaller diameter than a and its tip width l ₂
A protrusion 3' of about 2 mm is formed that protrudes diagonally toward the inner surface of the container. 2 to 4 are partially enlarged vertical sectional views for explaining the process of joining the two cup-shaped pieces 1 and 1', and these figures show the first piece 1 and the second piece 1. If we explain the joining process of ′ in order,
First, as shown in Figure 2, step 3 of the second piece 1'
and the protrusion 3' supplies hot melt adhesive 4;
Next, as shown in FIG. 3, the open end of the first piece 1 is fitted into the stepped portion 3 of the second piece 1' along the surface of the adhesive, and the open end of the first piece 1 and the second piece 1' The step portion 3 of the step portion 3 is polymerized. Adhesive 4 is suitably a polyamide hot melt adhesive with a melting point of about 180℃ to 200℃, and its thickness is
In order to make the supply thickness as uniform as possible, for example, use an electrostatic coating method to coat the stepped portion 3 with powdered adhesive or preheat it to an appropriate temperature (approximately 150 to 180 degrees Celsius). This is done by applying a band-shaped film type adhesive to the protrusion 3'. In addition, in order to smoothly fit the open end of the first piece 1 into the stepped portion 3 of the second piece 1', the inner diameter of the open end of the first piece 1 is adjusted by the thickness of the adhesive as shown in Figure 2. Make it larger, but as shown in Figure 5, step 3
It is also possible to make it slightly inclined toward the inner surface of the container so as to have a tapered shape. Alternatively, the inner diameter of the open end of the first piece 1 may be slightly expanded by heating the open end of the first piece 1 using a suitable method such as a heating plate prior to the above-mentioned fitting. Next, the open end of the first piece 1 and the fitting portion of the stepped portion 3 of the second piece 1' are heated and cooled in a configuration as shown in FIG. 4 to be integrally joined. That is, in FIG. 4, 5 and 5' are the first piece 1
and first and second copper coils respectively surrounding the lower part of the step 3 of the second piece 1', these coils are surrounded by Bakelite 6, 6', cooling water is flowed inside, and connected to a current transformer and a high frequency oscillator (not shown), and 7.
7' is an air outlet for cooling. Detailing the heating and cooling process using these devices,
First, high-frequency induction heating is performed for a short time using the copper coils 5 and 5' so that the stepped portion 3 of the second piece 1' is at a higher temperature than the open end of the first piece 1, and then heated to a predetermined temperature (e.g. When a hot melt adhesive 4 with a melting point of 180 DEG C. is used, the open end of the first piece 1 is brought to a temperature of 200 to 250 DEG C., and the step 3 of the second piece 1' is brought to a temperature of 250 DEG to 300 DEG C. At this time, the stepped portion 3 expands more than the fitting portion of the first piece 1, so the hot melt adhesive 4 is melted by heat and inside the outer peripheral surface of the step portion 3 and the fitting portion of the first piece 1. It is compressed between the circumferential surfaces to provide appropriate bonding pressure. After that, the electricity supply is stopped, and then air is jetted from the air jet ports 7 and 7' to cool the heating part, and the process of adhesive bonding of the fitting part of the first piece 1 and the second piece 1' is completed. do. In the above cooling process, the air ejected from the air ejection port 7 on the upper side of FIG. 4 is directly blown onto the fitting part of the first piece 1, but the air is ejected from the air ejection port 7' on the lower side of FIG. Since air is blown onto the body 1'a near the step 3 (not directly onto the step 3), the fitted portion of the first piece 1 is cooled more quickly than the step 3 of the second piece 1'. It is possible to maintain a constant bonding pressure even when the adhesive is contracted and cooled. 4' and 4'' in FIG. 4 are the parts where the adhesive 4 has been extruded. Here, the inner diameter of the fitting part of the first cup-shaped piece 1 is D ₁ , and the inner diameter of the fitting part of the second cup-shaped piece 1' is defined as D 1 . outer diameter
D ₂ and the adhesive thickness is d, and when the fitting part of the first piece 1 is heated to t ₁ °C, the second piece 1'
Assuming that it is possible to obtain adhesive _pressure to the point where the adhesive thickness _d becomes almost 0 by _heating the _stepped portion ₃ of can be determined. t ₂ =D ₁ +D ₁ ×23.9×10 ^-6 ×t ₁ −D ₂ /D ₂ ×23.9×10 ^-6 …
…(1) However, the above formula is derived as follows. t Inner diameter of the fitting part of the first piece 1 after heating to ₁ °C
D ₁ ′ is D ₁ ′=2×π×D ₁ ×23.9×10 ^-6 ×t ₁ /2π+D ₁ (23.9×10 ^-6 is linear expansion coefficient) of second piece 1′ after heating to t ₂ ℃ Outer diameter of stepped portion 3
D ₂ ′ is D ₂ ′=2×π×D ₁ ×23.9×10 ^-6 ×t ₂ /2π+D ₂ After heating both pieces 1 and 1′, the inner peripheral surface of the mating part of the first piece 1 and the second piece Considering that the outer peripheral surfaces of 1' are almost in contact, D ₁ '=D ₂ ' Equation (1) is derived from this. The specific figures are shown in the table below.

[Table] When actually performing high frequency induction heating,
Since the heat induced at the lower part of the step 3 of the second piece 1' is conducted to the step 3 with a slight delay,
In order to make the temperature of the stepped portion 3 higher than the temperature of the open end of the first piece 1, the first and second coils 5,
It is necessary to adjust the amount of current flowing through the coil 5 by connecting the coils 5' in parallel and by inserting a resistor into the circuit on the side of the first coil 5 for the first piece. Note that when the two heating coils 5, 5' are used in parallel and close to each other, in order to maintain heating efficiency and uniformity of temperature in the circumferential direction at the mating part, the current flowing through each heating coil 5, 5 is adjusted. are in the same direction. As for the heating frequency, it is best to select a frequency of about 10 to 250 KHz (both coils have the same frequency). Then, select the connection method and heating frequency as described above, and connect the coils 5, 5' and the first and second pieces 1,
The distance between each of
20KW), the heating process itself can generally be completed within at least 5 to 10 seconds. Further, the cooling process is also forcibly cooled by air, so it can be similarly shortened. In addition, on both sides of the thin aluminum plate in advance,
Thickness 3-4μ containing extremely small amount of polyethylene etc.
By applying a lubricating coating film such as epoxy resin, this coating eliminates the need to use lubricating oil during the subsequent compression molding process, and provides effective protection against corrosive effects on the inner and outer surfaces of the container. Moreover, since it can also serve as an effective primer for adhesives, the strength and reliability of adhesive joints can be greatly improved. Furthermore, the pressure-resistant strength of the pressure-resistant container manufactured by the manufacturing method of the present invention is as high as 7 to 8 kg/cm ² , and even when the container is dropped from a height of 1 m horizontally, no leakage of the contents from the adhesive joints is observed. Nakatsuta. The advantages of the manufacturing method according to the invention are as follows. (b) The second cup-shaped piece 1
Since the stepped portion 3 of the cup-shaped piece 1' is heated to a high temperature and the hot-melt adhesive is melted and joined, the stepped portion 3 has a higher degree of expansion than the fitting portion of the first cup-shaped piece 1. grow bigger,
Therefore, it is possible to obtain a uniform and sufficient bonding pressure over the entire circumference of the joint area without using a special presser etc. to obtain adhesive pressure, especially when the entrance of the container is narrow and the presser etc. is not placed inside the container. This is useful when manufacturing containers with shapes that are difficult to insert. To explain in more detail, the most characteristic feature of the present invention is that the temperature and degree of expansion of the first cup-shaped member 1 and the temperature and degree of expansion of the second cup-shaped member 1' are The adhesive pressure is obtained by the difference in the degree of expansion. That is, when heating the fitting portion, the temperature and degree of expansion of the stepped portion 3 of the second cup-shaped member 1' on the inside are higher than the temperature and degree of expansion of the fitting portion of the first cup-shaped member 1 on the outside. make it higher,
When contracting, the outer first cup-shaped member 1
The first cup-shaped member 1
Since the container is cooled quickly from the bottom, sufficient bonding pressure can be obtained by the difference between the degree of expansion and contraction without using a special tightening device. Ideal for manufacturing containers that are not available. (b) Since both the fitting part of the first cup-shaped piece 1 and the step part 3 of the second cup-shaped piece 1' are heated,
The hot melt adhesive melts quickly,
Moreover, as explained in the above item (a), a uniform and sufficient bonding pressure can be obtained over the entire circumference of the joint portion, and the entire circumference of the joint portion can be bonded uniformly in a short time. (c) Since the first cup-shaped piece 1 fitted on the outside of the stepped portion 3 is rapidly cooled, the first cup-shaped piece 1 contracts faster than the stepped portion 3, and therefore maintains constant adhesion even during cooling. It is possible to maintain pressure and ensure strong adhesion. (d) Since it is a method of adhesively joining two press-molded cup-shaped pieces at each open end, a minimum number of thin plates can be used, and the product weight is light and the cost is also low. (e) If a high frequency induction heating method is adopted as a heating method during bonding, even though the bonding area is relatively large, only a very short heating time is required, and the bonding time can be further shortened. (F) If a lubricating coating film such as epoxy resin is applied to both sides of a thin aluminum plate in advance, lubricating oil is not required during compression molding, and the aluminum plate has excellent corrosion resistance and strength, making it ideal for food containers. (g) Since the container can be manufactured without forming a protrusion such as a flange at the joint, there is no need to use excessive packaging materials such as cardboard, which reduces costs and improves the appearance. (H) Also, since the first cup-shaped member 1 and the second cup-shaped member 1' are heated separately by separate heating coils 5 and 5', an appropriate temperature difference between the two cup-shaped members is ensured during heating. can be caused to
The adhesive pressure due to the difference in the degree of expansion can be approximately accurately set to the desired appropriate pressure, and the adhesive performance is good. (li) Also, since the direction of the current flowing through both heating coils 5 and 5' is the same, the temperature uniformity in the circumferential direction at the mating part is maintained, and the adhesive pressure is uniform over the entire circumference of the joint part. is maintained. To reiterate the important advantages of the present invention, the method according to the present invention is completely different from the general shrink-fitting method in that, before assembly, the outer diameter of the small-diameter step 3 of the second cup-shaped member 1' is The inner diameter of the open end of the first cup-shaped member 1 is larger than the outer diameter of the small-diameter stepped portion 3 by the thickness of the adhesive 4, and both cup-shaped members 1 and 1' are fitted together. After that, both cup-shaped members 1, 1' are heated at different temperatures so that a temperature difference is created between the two cup-shaped members 1, 1'.
The degree of expansion of the adhesive 4 is varied, thereby applying adhesive pressure to the adhesive 4. Therefore, when the temperature returns to room temperature, both cup-shaped members 1 and 1' are completely joined by the adhesive 4, and after cooling, the mating parts are free from unreasonable compressive stress, unlike a simple shrink-fitting method. No residue remains, making it ideal for thin-walled metal pressure-resistant containers. When carrying out the present invention, the materials for both pieces 1 and 1' may be stainless steel, steel plate, etc. in addition to aluminum alloy.

[Brief explanation of the drawing]

FIG. 1 is a partially vertical front view of a thin-walled aluminum pressure container manufactured by the manufacturing method of the present invention, and FIG.
4 is a vertical cross-sectional partial view of the container showing the manufacturing process, and FIG. 5 is a vertical cross-sectional partial view of the container showing the manufacturing process of another embodiment. 1... First cup-shaped member (piece) made of thin-walled aluminum, 1'... Second cup-shaped member made of thin-walled aluminum, 3... Step portion.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a pressure container by fitting and bonding the open ends of first and second cup-shaped members made of thin metal with an adhesive, in which the second cup-shaped member 1' A small-diameter stepped portion 3 is formed at the open end of the first cup-shaped member 1, and the inner diameter of the open end of the first cup-shaped member 1 is made larger than the outer diameter of the small-diameter stepped portion 3 by the thickness of the adhesive. Hot melt adhesive 4 is applied to the outer peripheral surface of the stepped portion 3.
The open end of the first cup-shaped member 1 is fitted into the small-diameter stepped portion 3 of the second cup-shaped member 1' from the outside, and the outer periphery of the fitted portion of the first cup-shaped member 1 is spaced apart. A first coil 5 surrounds the second cup-shaped member 1', a second coil 5' surrounds the trunk of the second cup-shaped member 1' near the stepped portion 3 at an interval, and the first cup-shaped member 1 and the second cup-shaped member 1' are surrounded by a first coil 5'. For the double wall part where member 1' fits,
The small-diameter stepped portion 3 of the inner second cup-shaped member 1' is heated so that the temperature and degree of expansion thereof are higher than the temperature and degree of expansion of the fitting portion of the first cup-shaped member 1 which is located outside it. A method for manufacturing a thin-walled metal pressure-resistant container, characterized in that the first cup-shaped member 1 on the outside is rapidly cooled down so that the first cup-shaped member 1 on the outside contracts faster. 2. The method for manufacturing a thin-walled metal pressure container according to claim 1, wherein the first coil 5 and the second coil 5' are heated by induction at a high frequency of 10 kHz to 250 kHz.