JPH0218974B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a metal container having a seam formed by thermal bonding. The present invention relates to a method for manufacturing a metal container, which comprises efficiently heating and forming a seam by thermal bonding.

High-frequency induction heating is a heating means that is widely used for heating metal materials, and is also a heating means that is widely used for manufacturing metal containers such as adhesive cans that have seams formed by thermal bonding. However, the high-frequency magnetic field from the high-frequency induction heating coil is blocked by the metal material, so in conventional technology, the resin adhesive applied to the edge of the container material is melted by high-frequency induction heating prior to stacking. There is a method of overlapping both ends of the container material through a resin adhesive layer, and finally bumping the overlapping part while cooling to form a seam. A method is adopted in which the outside is heated by high-frequency induction, and both ends are thermally bonded by heat transfer from the outside.

However, although the former method can be conveniently applied when thermal bonding is performed by pressing both ends in the overlapping direction, such as in lap side seam cans where the seam extends straight in the axial direction, , an upper body and a lower body each consisting of a cup-shaped molded body formed by drawing or drawing-ironing a metal material are fitted at their circumferential open ends via an adhesive to form a container. In this case, it is difficult to apply because the axial pressing force at the time of fitting causes the molten adhesive layer to protrude outside the joint or cause damage to the open end.

In addition, in the latter method, the high-frequency magnetic field is blocked at the inner end of the seam and the outer end.
It is heated only by thermal conduction, and the adhesive layer interposed between the two ends has significantly poorer thermal conductivity than metal, so it takes a significantly longer time for heat bonding, and the bonding A temperature gradient is inevitably formed where the outer edge is hot and the inner edge is cold, resulting in the defect that uniform heating becomes difficult. In particular, when the metal material is a ferromagnetic material such as steel, the inner end portion is difficult to heat.

Therefore, an object of the present invention is to simultaneously heat both edges of a container material that are engaged through an adhesive resin layer from the outer edge and the inner edge by high-frequency induction heating. This is to provide a possible method.

Another object of the present invention is a method for producing a metal container having a thermally bonded seam, by which the thermal adhesive located between the engaged ends to form the seam can be heated by high-frequency induction within an extremely short time. is to provide.

Still another object of the present invention is to provide a method in which both ends of a material with an adhesive layer interposed therebetween can be heated to an arbitrary temperature.

Still another object of the present invention is to provide an upper body and a lower body each consisting of a seamless cup-shaped molded body made of metal.
The object of the present invention is to provide a method in which the circumferential open ends of the metal parts are fitted together via an adhesive layer, and the adhesive layer can be efficiently heated by high-frequency induction heating from the outside of the fitting part.

According to the present invention, in a method for manufacturing a container that includes joining both ends of a container material containing metal through a seam formed by thermally bonding resin, the both ends are engaged through a layer of thermally adhesive resin, and The part that should be a joint where both ends are electrically insulated locally is made so that the material connected to one end and the material connected to the other end face coil parts in which the current direction is opposite, and the joint is connected to the joint. A method for manufacturing a metal container, characterized in that the desired portion is located approximately at the center of both coil portions, and electricity is supplied to a high-frequency induction heating coil to induce eddy current passing through each of the two end portions to heat both end portions. is provided.

As already pointed out, the present invention has an upper body and a lower body each made of a seamless cup-shaped molded body made of metal, and the circumferential open ends of the upper body and the lower body are fitted together via an adhesive layer, This adhesive layer is efficiently heated from the outside of the fitting part by high-frequency induction heating, and is particularly useful for producing a bottle-shaped metal container with a circumferential side seam. Therefore, the present invention will be explained below using this container as an example, but the present invention is of course not limited to this case.

In FIG. 1 showing an example of a metal bottle according to the present invention, this bottle includes a lower body 1 made of a seamless cup-shaped molded body made of metal such as a tin-plated steel plate,
Upper body 2 consisting of a seamless cup-shaped molded body made of metal
These cup-shaped molded bodies are made up of
The open end portions 3 and 4 are overlapped and joined to form a circumferential side seam 5, thereby integrating the shape of the container.

In this embodiment, the lower body 1 is a cup consisting of a tall thin side wall 6 formed by highly drawn and ironed metal material and a thick bottom 7 that has not been substantially ironed; On the other hand, upper body 2
This is a cup consisting of a tall thin side wall portion 8 and an upper wall 9 formed by the same molding as the lower body. The height of the side wall portion 8 of the upper body 2 is within a range that is equal to or slightly larger than the width of the joint 5. The upper wall 9 of the upper body 2 has an upwardly convex tapered surface, and a spout 10 for filling or taking out the contents is formed in the center thereof.

In the specific example shown in FIG. 1, the open end 3 of the lower body 1 is narrowed to a smaller diameter than the rest of the body wall by neck-in processing in the vicinity of the open end 3. The upper body open end 4 of the diameter is inserted into the upper body open end 4 of the diameter. A thermal adhesive layer 1 is provided between the outer surface of the open end portion 3 of the lower body and the inner surface of the open end portion 4 of the upper body.
1 is provided to join and fix the lower body and the upper body. From the viewpoint of corrosion resistance, it is desirable that a portion of the adhesive 11 protrudes from the seam 5 and forms a coating layer 13 for the cut edge 12 of the metal material located inside the seam.

In the metal container having the above structure, an extremely small spout 10 is formed in the upper body 2, and therefore, after the upper body 2 and the lower body 1 are fitted together, this fitting assembly is It will be understood that it is virtually impossible to insert a special heating mechanism etc. into the interior of the three-dimensional body, and therefore the fitting portion can only be heated from the outside.

According to the present invention, by arranging a high-frequency induction heating coil on the outside of this fitting part using a specific mechanism and energizing it, not only the open end 4 located on the outside but also the open end located on the inside can be heated. 3 can be heated efficiently and bonding can be performed within a very short time.

In FIG. 2 for explaining the principle of the present invention, in a portion 5a that should be a seam, both ends 3 and 4 are mechanically engaged by fitting through an adhesive layer 11a, and furthermore, these both ends The parts 3 and 4 are at least locally electrically insulated by the adhesive layer 11a.

A high frequency induction heating coil, generally designated 14, is arranged outside the portion 5a which is to become the seam in the following positional relationship. That is, the side wall portion 6 connected to the inner open end portion 3 faces the coil portion 15 through which the current flows vertically from top to bottom at a certain point in the drawing, while the side wall portion 8 connected to the outer open end portion 4 faces the coil portion 15 where the current flows vertically from top to bottom at a certain point in the drawing. The coil portion 16 faces the coil portion 16 in which the current flows vertically from the bottom to the top at the same time in the drawing, and the portion 5a to be the joint is located approximately midway between the coil portions 15 and 16. Although the coil portions 15 and 16 are only shown in cross-section in the figures, it should be understood that they form continuous loops generally perpendicular to the drawing.

In the above-mentioned positional relationship, when high-frequency current is applied to the high-frequency induction heating coil 14, the current direction in the side wall portion 6 facing the coil portion 15 is opposite to that of the coil portion, and the open end portion 3 is in the same direction. An eddy current 17 is induced that passes as follows.
Similarly, in the side wall portion 8 facing the coil portion 16, an eddy current 1 passes through the open end portion 4 in the opposite direction to the current direction in the coil portion but in the same direction.
8 is induced. These eddy currents 17 and 18 are induced to have a low current density in the region of the side walls 6 and 8, respectively, and a high current density in the region of the open ends 3 and 4, so that the Not only the end portion 4 but also the open end portion 3 located inside is heated strongly. For this purpose, the high frequency induction heating coil 14 is formed such that the current density in the coil sections 15 and 16 is sparse. In the drawing, 19 is a magnetic core made of a magnetic material such as ferrite, and both coil portions 1
5, 16 and the material side walls 6, 8 are strengthened,
This is used to increase heating efficiency.

According to the present invention, as explained above, the electromagnetic coupling between the high-frequency induction heating coil and the metal material to be heated is achieved not at the portion where both ends of the material are overlapped, but rather at the side walls separated from this overlapping portion. Part 6
and 8, both ends of the material 3,
4. Moreover, the adhesive layer is sandwiched between both the inner and outer ends 3,
4 is heated, uniform heating is possible in a short time. A short heating time has the advantage that the amount of adhesive overflowing from the molten state is reduced.

In the present invention, in order to heat the entire circumferential fitting part with the above-mentioned high frequency induction heating coil,
A method of arranging a large number of high-frequency induction heating coils so as to substantially cover the periphery of a circumferential fitting part, and performing induction heating while keeping the fitted objects of the upper and lower bodies stationary; one or more high-frequency induction heating coils A method of arranging an induction heating coil and inductively heating the fitted part of the upper and lower bodies while rotating, a method of heating by rotating and moving the fitted part along a long flat coil, or a combination thereof. Methods etc. are adopted as appropriate.

Any high frequency current used in this type of induction heating can be used as the high frequency current to be applied to the coil, and generally speaking, a high frequency of 10 KHz to 500 KHz is preferably used. The input to the heating coil varies significantly depending on the size of the container, the required temperature, and heating time, and cannot be specified unconditionally. As an example, when joining a circumferential seam container with a diameter of 110.6 mm using a polyester adhesive, an input power of 7 KW is used.
It was confirmed that the thermal bonding process was completed in an extremely short time of 0.3 seconds.

According to the present invention, the outer end and the inner end can be heated to the same temperature, or they can be heated to different temperatures.

In the specific example shown in FIG. 3-A, the outer body 2
When the thickness t ₀ of the inner body 1 and the t _i of the inner body 1 are equal and the gaps between the heating coils 15 and 16 and both side walls are equal, the temperature rise tends to be slightly higher at the outer end 4. There is. In this case, by inserting a ferrite core or a copper plate 20 between the coil portion 16 of the heating coil 14 and the outer body 2, the temperature To of the outer end 4 and the temperature T _i of the inner end 3 can be adjusted. can be made equal. In this case, if a ferrite core is used, the heating efficiency will be higher because the power loss is lower than that of a copper plate. Also, the distance between the outer body 2 and the coil portion 16 is set to the distance between the inner body 1 and the coil portion 1.
By making the interval larger than 5, To
Heating is possible so that = T _i .

In the specific example shown in FIG. 3-B, the distance between the outer body 2 and the coil portion 16 is made larger than the distance between the inner body 1 and the coil portion 15, and the distance between the outer body 2 and the coil portion 16 is By inserting a ferrite core or a copper plate 20 between them, it is possible to heat with a temperature relationship such that T _i >To. Of course, by reversing this positional relationship, it is also possible to perform heating with a temperature relationship such that To>T _i .

In the specific example shown in FIG. 3-C, the heating coil 14
By lowering the position relative to the fitting part 5a, the eddy current induced in the outer end 4 is reduced, the temperature rise in the outer end 4 is suppressed, and T _i >To
We make sure that this relationship is established. Conversely, in FIG. 3-C, by raising the position of the coil 14 relative to the fitting part 5a, the eddy current induced in the inner end 3 is reduced, and the temperature rise in the inner end 3 is reduced. It can be suppressed.

In the present invention, any material that exhibits adhesive properties by being melted, softened, or activated by heat may be used as the adhesive layer, such as thermoplastic resin adhesives such as polyester, polyamide, and acid-modified polyolefin. Agents are advantageously used, but are of course not limited thereto.

All materials used for containers include light metals such as aluminum, tinplate, stain-free steel, and other metal-containing materials such as various surface-treated steel plates and black plates, and these materials are coated with various paints. It doesn't make any difference even if it's something. Further, this material may be a laminate of metal foil and plastic film, and if the plastic film exhibits heat-sealing properties, it is natural that it can be used as the adhesive layer.

The present invention is suitably applied to manufacturing a container having the above-mentioned circumferential seam. For example, as shown in FIG. 23b can also be advantageously used for lock seam bonding through the adhesive layer 11,
It can also be advantageously used for heat-sealing the periphery of the lid and the flange of the body using a thermal adhesive.

The invention is illustrated by the following example.

Modified vinyl paint was applied to the inner and outer surfaces of an aluminum plate (3004 material H19) with a base thickness of 0.23 mm, and the total coating amount was
After coating and baking to give a concentration of 180mg/dm ² and 80mg/dm ^{2 ,} a circular plate with a diameter of 250mm was punched out and formed using normal press processing, with an inner diameter of 110.60mm at the edge of the joint and a central part. An upper body with a spout with a diameter of 30 mm was fabricated.

On the other hand, a disk with a diameter of 250 mm was punched out from the same painted plate and formed by press working to produce a lower body with an outer diameter of 110.50 mm at the edge of the joint.

Adhesive was applied around the entire edge of the lower body to a width of about 6 mm on the outer surface and a width of about 2 mm on the inner surface as follows. That is, in Example 12, nylon 1
2 powder on the outer edge of the lower body 6 mm and the inner edge 2 mm
Electrostatic painting was performed after masking so that only the area was exposed, and then the area was heated with an infrared heater to melt the powder and form an adhesive film with a thickness of approximately 85 μm.

After the upper body produced as described above and the lower body coated with adhesive are fitted together, a heating process and a cooling process are performed in the same station to melt the adhesive at the fitted part and cool and solidify it. A metal container with a capacity of approximately 2000 ml was produced by joining the upper body and lower body. In addition, in the heating process, the member to be heated is
While rotating at 1480 rpm, heating was performed for 0.3 seconds with an input of 7 KW, and in the cooling process, at the same time as heating was completed, a compressed air nozzle was used to blow air onto the mating part for 1 second to cool it down.

In addition, the shape of the heating coil in the heating process is
3-A, 3-B, 3-C, the diameter of the conductor of the heating coils 15 and 16 is 4 mm, and the flat spiral heating is electromagnetically coupled to the upper member 2 and the lower member 1. The number of turns of the coil is 5 turns, and its width is
Wc is 25mm, and the width of the hollow part Wg is 20mm.

The cooling nozzle of the outer member is provided on the opposite side of the fitting part of the container corresponding to the heating coil so as to surround the fitting part, and the cooling nozzle of the inner member is inserted through the opening of the outer member, and is connected to the outer nozzle. It is installed to cool the corresponding position.

The heating process and cooling process adopted in each example are detailed below.

Example 1 The center of the heating coil is placed two degrees from the center of the fitting part so that the temperature rises of the outer member and the inner member are equal.
The heating coil was set in a state lowered by mm (Δl = 2 mm). In the cooling process, air was blown onto the outer and inner members.

The temperature of the fitting portion at this time is shown in FIG. Curve a is the temperature of the fitting portion of the outer member and inner member, and curve b is the temperature of the adhesive.

At the end of heating, the temperature of the fitting part of the outer member and inner member at t ₁ is both 230°C, and the temperature of the adhesive is 195°C.
It was warm at ℃.

Time required for the adhesive to reach the solidifying temperature of 145℃
t ₂ was 0.5 seconds after the end of heating.

The temperatures of the outer member and inner member at the time when the adhesive solidified were the same at 115°C. Therefore,
No more pressing force than necessary is applied to the adhesive, the adhesive is not extruded from the fitting part, and no tensile stress is applied to the adhesive even if the fitting part reaches room temperature.

Example 2 The heating coil was set so that the center of the heating coil was raised by 1 mm from the center of the fitting part (Δl = +1 mm) so that the temperature of the fitting part of the outer member was higher than that of the inner member. .

At the end of heating, the temperature of the outer member at t= _t1 is 245℃,
The temperature of the inner member was 215°C and the temperature of the adhesive was 195°C.

The time required for the adhesive to reach the solidifying temperature of 145°C was 0.5 seconds after the end of heating. At this point t=
At t ₂ , the temperature of the inner member is 110°C and the temperature of the outer member is 120°C. Since the temperature of the outer member is slightly higher, the tightening force of the adhesive is weaker, but this degree of temperature difference There is no practical problem.

Example 3 The heating coil was set so that the center of the heating coil was 3 mm lower than the center of the fitting part (Δl = -3 mm) so that the temperature of the fitting part of the outer member was lower than that of the inner member. did.

The temperature of the outer member at the end of heating (t = t ₁ ) is 220
℃, the temperature of the inner part is 240℃, the temperature of the adhesive is 195℃
It was warm at ℃.

The time required for the adhesive to solidify was 0.5 seconds after the end of heating. At this time, the temperature of the outer member was 115°C, and the temperature of the inner member was 120°C. In this case, since the temperature of the outer member is slightly lower than that of the inner member, a tightening force may act on the adhesive and the molten adhesive may be extruded, but this does not pose a practical problem.

[Brief explanation of drawings]

Fig. 1 is a side cross-sectional view of a metal container having a circumferential side seam formed by thermal bonding, Fig. 2 is a side cross-sectional view of a high-frequency induction heating coil and the container for explaining the principle of the present invention, and Fig. 3-A. , FIG. 3-B and FIG. 3-C are partially enlarged side sectional views showing several examples of arrangement of high-frequency induction heating coils, and FIG. FIG. 5, which is a sectional view showing an example used for bonding, is a diagram showing a temperature-time curve during heating and cooling of each part of the seam in Example 1. Reference number 1 is the lower body, 2 is the upper body, 3 and 4 are the open ends, 5 is the seam, 5a is the fitting part, 6 and 8 are the side walls, 11 and 11a are the adhesive layers, and 14 is the high-frequency induction heating coil. , 15 and 16 are coil portions in which current directions are opposite to each other, 17 and 18 are eddy currents in which directions are opposite to each other, and 19 is a magnetic core.

Claims (1)

[Scope of Claims] 1. A method for manufacturing a container that involves joining both ends of a container material containing metal through a seam formed by thermally bonding resin, wherein both ends are engaged through a layer of thermally adhesive resin. In addition, the part that should be a joint where both ends are electrically insulated locally is made so that the material connected to one end and the material connected to the other end face coil parts in which the current direction is opposite, and the joint is formed. A metal container characterized in that the part to be heated is located approximately at the center of both coil parts, and the high-frequency induction heating coil is energized to induce an eddy current passing through each of the ends to heat both ends. Manufacturing method. 2 The high-frequency induction heating coil has a magnetic core in the center and a coil around it, and the engaged ends to be bonded face the magnetic core and are connected to one end of the material and the other end. 2. The method according to claim 1, wherein the high-frequency induction heating coil is positioned and a magnetic field is applied so that the materials connected to the end portions face coil portions having opposite current directions. 3. The above-mentioned materials are an upper body and a lower body each consisting of a seamless cup-shaped molded body made of metal, and their open ends are fitted together, and the fitted ends are connected to the high-frequency induction heating coil. The method according to claim 1, wherein the adhesion is performed by heating.