JPS635873B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for heating a sheet of non-magnetic metal, and more particularly to a heating method for heating a sheet of non-magnetic metal, and more particularly, for heating a notched side edge of a sheet of non-magnetic metal, for example for producing a can body with a side adhesive. The present invention relates to a method for high-frequency induction heating of parts.

In Japanese Patent Publication No. 55-39606, one of the authors of the present invention proposed a method for heating the side edges of a non-magnetic metal thin plate, such as an aluminum thin plate, relatively uniformly along the length direction. A rectangular non-magnetic metal thin plate having a shape is moved through a predetermined planar passage, and the side edge of this thin plate is heated by a high-frequency induction heating coil having a magnetic field substantially perpendicular to the plane of the passage when the thin plate is not present. When heating,
feeding the thin metal sheet intermittently through the passageway; one of the stop positions in the intermittent movement of the thin metal sheet corresponds to an installation position of the high frequency induction heating coil; and a substantially perpendicular magnetic field by the heating coil; The length along the side edge of the thin metal plate of the area where substantially exists is substantially shorter than the length of the side edge of the thin metal plate, and the front end of the side edge of the thin metal plate is the front edge of the area. and during a period in which the rear end of the side edge is substantially rearward in the traveling direction than the rear end of the region, the input voltage to the heating coil is increased. An induction heating method was proposed.

According to this method, the front and rear ends of the side edge portions do not melt due to overheating, and can be heated substantially uniformly from the front end to the rear end.

However, when heating the side edge 1a of a blank 1 made of a non-magnetic metal thin plate having a notch 2 as shown in FIG. 1, an induced current 3 as shown in FIG. 3 flows through the side edge 1a. As a result, the current density in the vicinity part 2a of the notch 2 becomes excessively large compared to other parts, so that the vicinity part 2a is overheated and the vicinity part 2a is
Problems such as burning of the organic coating film on the surface a or, in extreme cases, melting of the metal in the vicinity part 2a, are likely to occur.

It is an object of the present invention to solve the problems of the prior art described above.

To achieve the above object, the present invention performs high-frequency induction heating by intermittently moving the notched side edge of a non-magnetic metal thin plate through a predetermined planar path along a high-frequency induction heating coil. The heating coil generates a magnetic flux substantially perpendicular to the passageway when the passageway is free of the side edges, and when the side edges are stationary in the passageway. When the electromagnetic coupling between the part of the coil corresponding to the notch and the side edge is weakened, and the side edge is stopped, input power to the heating coil is reduced. The present invention provides a method for heating the side edge of a non-magnetic metal thin plate, which is characterized by heating the side edge of a non-magnetic thin metal plate.

The present invention will be described below with reference to the drawings.

Blank 1 in FIG. 1 shows an example of a non-magnetic metal thin plate to which the present invention is applied, and is made of an aluminum alloy thin plate having baked coatings (for example, epoxyphenol coatings) on both sides. There is. A V-shaped notch 2 is formed in the center of both side edges 1a and 1b of the blank 1, and a V-shaped cross section as shown in FIG. A score section 4 is formed. Further, corner cut portions 5 are formed at both ends of the side edge portions 1a and 1b. Further, a thermal adhesive tape 6 is heat-sealed to the side edges 1a and 1b.

Such a blank 1 is formed, for example, as follows.

First, in the pre-process, both edges (1
After high-frequency induction heating (for example, to 200°C to 300°C) of the side edges (portions corresponding to a and 1b), one side of the side edge (portion corresponding to 1a) (in Fig. 1) and both sides of the side edge (portion corresponding to 1b) adhesive tape 6
(for example, made of a nylon 12 film) is heat-sealed, and then slit to the length of the blank 1,
At the same time, the score section 4 is formed. Then blank 1
is carried to the can body forming machine, and the notch 2 and corner cut portion 5 are
to form blank 1.

Next, the blank 1 is rolled into a can body shape with the printed surface facing the outside, and the adhesive tape 6 on the side edges 1a, 1b is melted by a high frequency induction heating method as described later. The side edges 1a and 1b are heat-sealed via the adhesive tape 6 while applying pressure so that they overlap, and are cooled in a short time to form a can body molded body (not shown) having a side surface adhesive part. form.

By cutting this molded can body along the score portion 4, a can body (not shown) having a side adhesive portion can be manufactured. After that, flanges are formed on both open ends of the can body, and a bottom member and a lid member are double-sealed to the flanges to form a sealed can.

As described above, two can bodies can be manufactured in the same process. Note that the notch 2 and the corner cut portion 5 are formed to prevent the part corresponding to the side adhesive part of the flange part of the can body from becoming thicker than other parts, which would impair the sealing performance after double seaming. It is what was done.

FIG. 4, FIG. 5, and FIG. 6 show a high-frequency induction heating coil device 7 (hereinafter abbreviated as the coil device) used to heat the side edge 1a of the blank 1. The coil device 7 has a high-frequency induction heating coil 8 (referred to as a heating coil in this specification) and a pocket portion 9d that surrounds the heating coil 8 and is made of a high magnetic permeability material (for example, ferrite) and has a U-shaped cross section. It has a magnetic core 9.

As shown in FIG. 5, the heating coil 8 has conductors 8a and 8b disposed facing each other in the vertical direction, in which the current flows in the same direction, and conductors 8a and 8b in which the direction of the current flows is opposite to that of the conductors 8a and 8b, respectively. The conductors 8c and 8d are disposed close to the conductors 8a and 8b, respectively, and facing each other in the vertical direction.

As shown in FIG. 4, the upper conductors 8a and 8c extending horizontally within the magnetic core 9 rise immediately after exiting both ends 9a ₁ and 9a ₂ of the upper wall 9a of the magnetic core 9; The lower conductors 8b and 8d extending horizontally inside the magnetic core 9 fall immediately after exiting both ends 9b ₁ and 9b ₂ of the lower wall 9b of the magnetic core 9. As shown in FIG. 6, the length l ₁ of the magnetic core 9 is equal to
To prevent overheating of a ₂ and 1a ₃ , the length l ₂ of the side edge 1a to be heated is slightly smaller (usually 6 to 10
mm) is determined. Further, recesses 10 and 11 are formed in the longitudinal center of the upper wall portion 9a and the lower wall portion 9b of the magnetic core, and extend to the side wall portion 9c. 9d does not exist.

As shown in FIG. 5b and FIG.
are upper conductors 8a, 8c and lower conductors 8b, 8d
horizontally along the height center position between
That is, it is intermittently transferred by a transfer device (not shown) so as to move along the planar path 14 (FIG. 5a).

FIG. 5a shows the magnetic flux 12 formed by the conductors 8a and 8b and the magnetic flux 13 formed by the conductors 8c and 8d when there is no blank 1 in the pocket part 9d. conductor 8a
Since the direction of the current flowing through and 8b is the same, the magnetic flux 12 is formed substantially perpendicular to the path 14 of the blank 1. Similarly, the magnetic flux 13 is also formed substantially perpendicular to the passage 14.

Note that another example of a heating coil device that forms magnetic flux substantially perpendicular to the passage 14 of the blank 1 is the heating coil device proposed in Japanese Patent Application No. 56-33926. A heating coil device is preferred.

FIG. 5b shows the magnetic flux 12' formed by the conductors 8a, 8b and the magnetic flux 13' formed by the conductors 8c, 8d when the side edge 1a of the blank 1 is in the pocket part 9d. This is what is shown.
Since the blank 1 is made of non-magnetic material, the magnetic flux 13'
without entering the side edge 1a.
It is formed through the side wall portion 9c of the magnetic core so as to go around the edge _1a1 of the magnetic core. Further, the magnetic flux 12' is divided into upper and lower parts of the side edge 1a, and conductors 8a and 8
b, respectively, through the upper wall portion 9a and lower wall portion 9b of the magnetic core.

As described above, since the magnetic fluxes 12' and 13' are formed through the magnetic core made of a high magnetic permeability material, the magnetic fluxes (not shown) formed in the portions of the conductor 8 in the recesses 10 and 11 where the pocket portion 9d is not present. ) has a higher magnetic flux density. In such cases, the temperature rise of the metal plate per unit time is generally approximately 2 times the magnetic flux density.
Since it is considered to be proportional to the power of
When the condition of a is uniform in the longitudinal direction (for example, when there is no notch 2), the recesses 10, 11
The heating temperature of the portion of the side edge portion 1a located opposite to is lower.

The side edge portion 1a of the blank 1 is induction heated by the coil device 7 described above in the following manner.

With the input power of the heating coil 8 set to 0 or relatively small, the side edge 1a of the blank is moved along the passage 14 into the pocket 9d of the coil device 7 in the direction of the arrow (FIG. 6). As shown in FIG. 6, when the notch 2 is located at the center of the recesses 10 and 11 in the longitudinal direction (of the magnetic core 9), the operation is stopped and a relatively large electric power is immediately input to the heating coil 8.

At this time, induced currents 15 and 16 as shown in FIG. 7 are induced in the side edges 1a because of the recesses 10 and 11 without being excessively concentrated in the notch vicinity 2a. That is, by appropriately determining the dimensions of the recesses 10 and 11, especially the longitudinal distance d, in relation to the base width w and height h of the notch 2, etc., it is possible to avoid overheating the notch vicinity 2a. The side edge portion 1a can be induction heated relatively uniformly along its longitudinal direction within a desired temperature range. Immediately after reaching the above desired temperature range, the input power of the heating coil 8 is reduced to 0 or relatively small as before feeding into the pocket portion 9d, and the blank 1 is moved again in the direction of the arrow, and the coil It is sent from the device 7.

When stopping, both ends 1a ₂ and 1a ₃ of the side edge 1a
are the opposite ends 9a ₁ , 9b ₁ and 9a ₂ , 9 of the magnetic core 9
b ₂ , so the side edge 1 of the magnetic flux
There is almost no wraparound to a ₂ , 1a ₃ , and blank 1
By appropriately determining the input power of the heating coil 8 when moving the side end 1 based on experiments,
The heating temperature of a ₂ and 1a ₃ can also be made approximately equal to that of the other portions of the side edge portion 1a.

FIG. 9 shows the side edge of the blank 1 which is rolled up into a can body shape with the side edge 1a and side edge 1b open using the high frequency induction heating coil device 7 having the structure as explained above. The parts 1a and 1b (thermal adhesive tape 6 has been heat-sealed in the previous step) are connected to the thermal adhesive tape 6.
The figure shows an example of heating above the melting point or softening point of can body blank 1, and 20 is a mandrel that guides can body-shaped blank 1.

The present invention is not limited to the above examples, and for example, the inner surface of the heating coil 8 in the portion corresponding to the recesses 10 and 11 is shielded with a metal plate (not shown, for example, a copper plate) having good electrical conductivity. By doing so, overheating of the notch vicinity portion 2a can be more reliably prevented.

Further, a plurality of notches 2 may be formed along the side edges. In this case, while the blank is stopped, induction heating is performed using a coil device in which a recess is formed at a position corresponding to the notch, or in which the above-mentioned shielding plate is further provided. Further, the notch may also be of any shape.

According to the present invention, the notched side edge of a non-magnetic thin metal plate can be extended in the longitudinal direction without overheating in the vicinity of the notch, that is, without causing troubles such as burning of the paint film or melting of the metal. This has the effect of being able to heat relatively uniformly along the direction.

Examples will be described below.

Example The length _l1 of the magnetic core is 62.5 mm, the distance d between the recesses 10 and 11 is 7.5 mm, the depth of the pocket portion 9d is 14 mm, the height of the side wall portion 9c is 23.5 mm, and the conductors 8a and 8 have an elliptical cross section.
The height of b, 8c, and 8d is 5.5 mm, the maximum width is 2.3 mm, the center distance between conductors 8a and 8c, and between 8b and 8d is all 6 mm, and the upper conductor 8a, 8c and the lower conductor 8
The distance between b and 8d (in the height direction) is 7 mm, conductor 8
A coil device 7 of the type shown in FIGS. 5 and 6 was prepared in which the distance from the center of the coils c and 8d to the extended surface of the inner surface of the side wall portion 9c was 6 mm.

On the other hand, the length l ₂ of the side edge 1a is 70.6 mm, the thickness is 0.23 mm,
An aluminum alloy thin plate (5052
A blank 1 made of material) is passed through a passage 14 into a coil device 7 so that the plunge depth m (Fig. 6) of the side edge portion 1a into the pocket portion 9d is 12 mm, and the blank 1 is heated at a rate of 200 coils per minute. Delivered at speed. The stopping time in the coil device 7 of blank 1 is 0.16 seconds,
When stopped, the notch 2 is positioned at the center in the longitudinal direction of the recesses 10, 11.

The frequency of the high-frequency current supplied to the heating coil 8 was 400kHz, and a vacuum tube type oscillator was used. The input power to the heating coil 8 when the blank 1 was in transition was 0, the input power when it was stopped was 5 kW, and the ON time of the high frequency current was controlled to be 0.15 seconds.

FIG. 8 shows a temperature pattern measured by the temperature-indicating paint near the side edge 1a heated as described above. In the figure, e, f, and g indicate temperature regions of 232°C, 270°C, and 300°C, respectively.

For comparison, blank 1 was prepared using the same coil device as above, except that recesses 10 and 11 were not formed.
Heating was carried out under the same conditions using
The metal in the vicinity of the portion 2a melted, making it impossible to obtain a satisfactory heated blank.

[Brief explanation of the drawing]

FIG. 1 is a plan view of an example of a non-magnetic thin metal plate to which the present invention is applied, FIG. 2 is a longitudinal sectional view taken along the line - in FIG. FIG. 4 is a perspective view of an example of a high-frequency induction heating coil device applied to the present invention, and FIG. FIGS. 5a and 5b are longitudinal cross-sectional views taken along the line - in the figure, and FIGS. is shown in Figure 4.
7 is a cross-sectional view taken along the line, FIG. 7 is a plan view of the main part showing the induced current induced in the side edge of the thin metal plate of FIG. 1 which has been induction heated by the method of the present invention, and FIG. FIG. 9 is a plan view of the main part showing an example of the temperature pattern of the side edge of the thin metal plate shown in FIG. FIG. 1... Blank (non-magnetic metal thin plate), 1a... Side edge, 2... Notch, 8... High frequency induction heating coil, 1
2, 13...Magnetic flux, 14...Planar path.

Claims (1)

[Claims] 1. A method of performing high frequency induction heating by intermittently moving the notched side edge of a non-magnetic metal thin plate through a predetermined planar path along a high frequency induction heating coil, the heating coil comprising: , forming a magnetic flux substantially perpendicular to the passageway when the side edge is absent from the passageway, and a portion of the coil corresponding to the notch when the side edge is stopped in the passageway; A non-magnetic metal characterized in that the electromagnetic coupling between the side edge portion and the side edge portion is weakened, and the input power to the heating coil is increased when the side edge portion is stopped. Method of heating the side edges of thin plates.