JPH0216993B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of inspecting a joint, and more particularly to a method of inspecting a thermally bonded joint of a container.

Recently, as shown in FIG. 1, an upper can body 2 having a spout portion 2b and a bottomed lower can body 3 have open ends 2a and 3a (3a has been reduced in diameter).
are fitted via an adhesive layer 4 (for example, made of thermoplastic plastic such as modified linear polyester) (so that elastic pressure is applied to the adhesive layer 4) to form a fitting part, that is, an overlapping part, There has been proposed a metal container 1 having a circumferential bonding portion 5 in which the overlapping portion is then subjected to high-frequency induction heating to melt or soften the adhesive layer 4 and perform thermal bonding. The upper can body 2 and the lower can body 3 are made of a metal plate (for example, an aluminum alloy thin plate, a tinned steel plate) on which an organic coating (not shown) is formed on the inner and outer surfaces (at least the surface in contact with the adhesive layer 4 is a primer coating). , stain-free steel, etc.), mainly by drawing.

In the manufacturing process of the metal container 1, a thermoplastic tape is usually thermally bonded along the outer circumferential surface _3a1 of the open end 3a, which has been reduced in diameter, leaving a protruding part, and then the protruding part is folded back and the end face 3
A ₂ and the inner circumferential surface 3a ₃ (see FIG. 2a) are thermally bonded to protect the end surface 3a ₂ where the metal is exposed. However, as shown in Fig. 2a, due to the outwardly protruding burrs 3a, ₄ , etc., the plastic tape (i.e., the adhesive layer 4) is locally broken during the folding process, and a part of the end surface 3a, ₂ is broken. is exposed, resulting in a defective joint, and at the same time a metal contact may occur between the burr _3a4 and the inner surface of the outer open end 2a.

Or, as shown in Figure 2b, due to poor alignment between the upper can body 2 and the lower can body 3 during the fitting operation,
The adhesive layer and paint film on the outer periphery of the open end 3a are scraped off by the inner end corner 2a ₁ of the outer open end 2a, resulting in a defective joint, and as a result, the open ends 2a and 3a are scraped off. Metallic contact may occur between them.

Alternatively, as shown in FIG. 2c, the lower can body 3 is pushed too far into the upper can body 2 during the fitting operation, resulting in an insufficient height of the container, resulting in an inner edge of the open end 2a. The corner 2a ₁ may come into metal contact with the outer surface of the tapered portion 3a ₅ of the open end 3a.
The above-mentioned phenomenon of insufficient height also occurs when the diameter-reduced portion is insufficient in height due to a mistake during diameter-reducing processing.
If the height of the container is insufficient, sufficient axial load cannot be applied when the cap is plugged into the spout 2b, which tends to result in poor sealing.

The present invention has been made in view of the above technical problems, and the present invention inspects the presence or absence of defective joints as described above during the thermal bonding process.

That is, the present invention provides a first container member having metal.
A method for inspecting a joint formed by overlapping an end portion and a second end portion with a thermoplastic layer interposed therebetween to form an overlapping portion, and thermally bonding the overlapping portion, the method comprising: High-frequency induction is applied such that an induced current is locally induced along the length of the overlapping section, and the directions of the induced currents flowing through the first end and second end of the overlapping section are opposite to each other. A heating coil is placed to face the container member, and while the overlapping portion and the heating coil are moved relative to each other, the heating coil is energized to perform thermal bonding along the entire length of the overlapping portion,
A method for inspecting a joint part of a container, characterized by detecting the temperature of the joint part along the entire length during or immediately after the heat bonding, and determining the range of temperature fluctuation in the length direction of the joint part. This is what we provide.

A preferred first aspect of the container member is a metal container 1
These are an upper can body 2 and a lower can body 3 (see Fig. 1). In this case, the first end is the open end 2a of the upper can body 2, and the second end is the open end 3a of the lower can body 3.

A second preferred embodiment of the container member is a metal can body molded body 21', in which the first end and the second end are opposing opposite side ends 25a' (the first
(See Figure 0).

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

In FIGS. 3 and 4, parts having the same reference numerals as those in FIG. 1 indicate similar parts. 3 and 4 show a fitting part 5' of a container assembly 1' in which an upper can body 2 and a lower can body 3 are fitted together via an adhesive layer 4, and a fitting part 5' is formed. This shows a state in which thermal bonding is performed by induction heating by a high frequency induction heating coil (hereinafter referred to as heating coil) 6. Multiple turns (3 turns in the diagram)
The heating coil 6 has an upper horizontal portion 6a relatively close to the open end portion 2a of the upper can body 2, and the upper horizontal portion 6a is relatively close to the open end portion 2a of the upper can body 2.
, the lower horizontal part 6b is relatively close to the open end 3a of the lower can body 3 (the distance between the upper horizontal part 6a and the open end 2a, and the distance between the lower horizontal part 6b and the open end 3a). They are provided so as to face the body wall portion 3c so that the intervals are substantially equal).

Moreover, the central angle δ of the vertical portions 6c and 6d of the heating coil 6 with respect to the axis of the container assembly 1' is approximately 40 to 180.
It is formed in an arcuate shape when viewed from above, and concentrically with the container assembly 1', so as to be parallel to each other (see FIG. 8). . Although not shown, it is desirable to attach a magnetic core such as a ferrite core to the heating coil 6 in order to increase current efficiency. The heating coil 6 is connected to a high frequency oscillator (not shown).

When heating the fitting part 5' to perform thermal bonding,
While the container assembly 1' is being rotated about its axis, the heating coil 6 is energized. At this time, if the fitting part 5' is sound with no metal-to-metal contact, an induced current 7 flows through the open end 2a near the part of the body wall 2c of the upper can 2 that faces the heating coil 6. ,
In the vicinity of the portion of the body wall 3c of the lower can 3 that faces the heating coil 6, an induced current 8 passing through the open end 3a is generated.
flows. The strengths of induced currents 7 and 8 are substantially equal. Since the directions of the current flowing through the upper horizontal portion 6a and the lower horizontal portion 6b of the heating coil 6 are opposite, the portion of the induced current 7 at the open end 2a,
The direction of each current in the portion of the induced current 8 at the open end 3a is opposite.

As described above, when the fitting portion 5' and therefore the joint portion 5 are healthy, the heating temperature along the circumferential direction is relatively uniform. Figure 5 shows an example of this, and shows an aluminum alloy thin plate (JIS
3004H 19) Container assembly 1' with an outer diameter of 122 mm
While rotating (rotating) the heating coil 6 (height of the fitting part 5' 5 mm) at a rotational speed of 1400 rpm, the heating coil 6 of the type shown in FIG. Distance x between fitting parts 5' (Fig. 8) 3
mm, using ferrite core), 300kHz,
An example is shown in which the surface temperature of the fitting part 5', that is, the joint part 5, was measured using an infrared radiation thermometer installed at a fixed position when 4 kW of high-frequency power was applied for 1 second. On the horizontal time axis, 1 cm corresponds to 40 msec,
The time required for one rotation of the fitting portion 5' is approximately 43 msec. Time t ₁ is the point at which energization is stopped. According to this, 1 of the fitting portion 5' during and immediately after heating.
It can be seen that the temperature fluctuation width ΔT ₁ during rotation is about 15°C.

FIG. 6 shows when the metal-to-metal contact portion 9 is present in a part of the fitting portion 5' and the metal-to-metal contact portion 9 is at a position facing the heating coil 6 (not shown in FIG. 6). Flows of induced currents 7 and 8 are shown. In other words, induced currents 7 and 8 flowing in opposite directions
leaves the metal-to-metal contact 9 and detours to avoid collision at the metal-to-metal contact 9. Therefore, the heating temperature in the vicinity of the metal-to-metal contact portion 9 is lower than that in the normal portion, and therefore the range of fluctuation in the heating temperature along the circumferential direction at the fitting portion 5' or the joint portion 5 during or after heating becomes large. .

FIG. 7 shows the case where the metal-to-metal contact portion 9 exists at one location in the fitting portion 5', and the surface temperature of the fitting portion 5', and therefore the joint portion 5, during rotation is measured in the same manner as in FIG. In this example, the fluctuation range ΔT ₂ during one rotation is about 75° C., which is much larger than the case shown in FIG. Note that time t ₁ indicates the point in time when energization is stopped.

Although the fitting portion 5' is normal, metal-to-metal contact may occur when the adhesive layer melts or softens during heating. In this case, the metal-to-metal contact part will shoot, causing an excessive current to flow through the part, causing a local temperature rise, creating bubbles in the adhesive layer and burning the paint, resulting in a defective joint. Become. In this case as well, the range of temperature fluctuation during one rotation of the fitting portion 5' increases.

Therefore, by determining whether the fluctuation range of the heating temperature during one rotation during heating or immediately after heating of the fitting part 5' and hence the joining part 5 is within a predetermined tolerance range, defective joints can be detected. can be detected.

FIGS. 8 and 9 show an example of an inspection apparatus for carrying out the method of the present invention.

Reference numeral 10 denotes a turret, which has six equally spaced pockets 10a along its periphery for storing container assemblies 1', and continuously rotates at a constant speed in the direction of arrow P. A heating coil 6 is attached to each pocket portion 10a. Container assembly 1' is loaded into pocket 10a at loading station A. Immediately after loading, the container assembly 1' is rotated about its axis at a constant speed in the direction of arrow Q, that is, rotated on its own axis, by a drive device (not shown).

B is a heating station, in which the heating coil 6 is energized when the outermost end 1'a of the container assembly 1' reaches its starting end _B1 , and is turned off when it reaches its terminal end _B2 . It is becoming more and more popular. That is, while passing through the heating station B, the fitting part 5' of the container assembly 1' is thermally bonded to form the metal container 1 having the joint part 5.

A temperature sensor 11 (for example, an infrared radiation thermometer or a roller thermometer with an embedded thermocouple) is disposed outside the turret 10 near the end _B2 of the heating station B. In the figure, the terminal end B ₂
The metal container 1 shown by the dotted line in FIG. 1 shows the position after the metal container 1 shown by the solid line has rotated once.
That is, the outermost end 5a of the joint 5 shown by the solid line reaches the position of the outermost end 5a of the joint 5 shown by the dotted line after the metal container 1 makes one rotation (rotation) in the direction of the arrow (Q). In this manner, the metal container 1, and thus the joint portion 5, moves approximately downward in FIG. 8 by the central angle θ of the turret 10 during one revolution by the revolution in the direction of the arrow P.

The temperature sensor 11 swings from the direction shown by the solid line to the direction shown by the dotted line following the movement due to the revolution of the joint 5, and rotates between the outermost end 5a shown by the solid line and the outermost end 5a shown by the dotted line. The temperature of the joint 5 is detected along the entire length of the joint 5 as it passes through (one rotation).

By the time the following metal container 1' reaches the end B ₂ of the heating station, the temperature sensor 11 swings back in the direction shown by the solid line, and when the metal container 1' revolves from the end B ₂ by a central angle θ, the temperature sensor 11 returns to the direction shown by the dotted line. Repeat the motion of swinging in the direction indicated by (for example, at a frequency of 60 times per minute). Temperature sensor 11 is not due to vibration, but the 8th
The configuration is such that the temperature of the joint 5, which rotates (one rotation) and passes between the outermost end 5a shown by the solid line and the dotted line, is detected along its entire length by repeating movement approximately in the vertical direction in the figure. may have been done.

C is a delivery station, and among the metal containers 1 delivered from the delivery station C, those having a defective joint 5 are sent to a reject device 12 based on a reject signal 12a output from a discrimination circuit 13. Therefore, the material is discharged in the R direction, while those having a normal joint 5 are delivered in the S direction without being rejected and sent to the next process.

FIG. 9 shows the discrimination circuit 13,
11 is a temperature sensor, and 14 is a temperature monitor having a function of amplifying the output voltage of the temperature sensor 11.
Comparators 15 and 16 compare voltages corresponding to the upper limit temperature (T ₁ , e.g. 250°C) and the lower limit temperature (T ₂ , e.g. 204°C), respectively, with the voltage input from the temperature monitor 14. . 1
7 is an inverter, and when the temperature (T) measured by the temperature sensor 11 is higher than the upper limit temperature (T ₁ ),
1 signal is input to the OR gate 18 when the temperature is lower than the lower limit temperature (T ₂ ).

19 is an AND gate into which the output signal from the OR gate 18 and the signal 20 are input. signal 2
0 is an output signal from a proximity switch (not shown) provided at the terminal end _B2 of the heating station B, and indicates that the metal container 1 shown by the solid line at the terminal end _B2 in the figure reaches the position shown by the dotted line. It is ON only during the time of movement, that is, the time of one rotation.
Therefore, within the above-mentioned one rotation time, the upper limit temperature (T ₁ )
When the temperature sensor 11 detects a higher temperature or a temperature lower than the lower limit temperature (T ₂ ), a 1 signal is output from the AND gate 19, and the temperature detected by the temperature sensor 11 becomes the upper limit temperature. (T ₁ ) and the lower limit temperature (T ₂ ),
A 0 signal is output from the AND gate 19.

Reference numeral 21 denotes a delay circuit in which a time delay is set until the metal container 1 at the terminal end _B2 reaches a position facing the reject device 12. Therefore, along the junction 5, the upper temperature limit (T ₁ ) and the lower temperature limit (T ₂ )
The metal container 1 whose temperature is detected to be outside the range is rejected by the reject device 12 based on the reject signal 12a from the discrimination circuit 13.

As shown in FIG.
5'a are overlapped with each other via an adhesive layer 24 to form a side surface overlapping part 25'.
1' in the direction of arrow M.
6, the overlapped portion 25' is heated by induction and thermally bonded to form the metal container body 2 having the side surface joint portion 25.
The present invention can also be applied to defect inspection of the joint portion 25 when manufacturing 1. In other words, the temperature sensor 3 is provided on the outlet side of the heating coil 26 facing the side surface joint 25.
1, it is sufficient to measure and determine the variation width of the heating temperature along the entire length of the side surface joint portion 25.

The material forming the metal container is a composite material containing metal foil and a thermoplastic film or sheet, and this thermoplastic film or sheet may be used as the adhesive layer.

According to the present invention, since defective joints are detected during the thermal bonding process, there is no need for a special inspection process, which simplifies the process. In the process of forming layers on container members and in the process of forming overlapping parts (for example, fitting parts), defects that have a serious impact on container performance can be detected even if these processes are not specifically inspected. This has the effect that it can be inspected all at once during the thermal bonding process (which requires complicated labor for inspection).

In addition, since the heating temperature at the joint is detected and the variation width in the length direction is determined, the inspection is simple, and all the joints of the container or container body can be continuously and automatically inspected online. It has the advantage of Furthermore, during the inspection according to the present invention, defective joints due to overheating or underheating of the entire joint (for example, due to excessive or insufficient output of the heating coil, or due to incorrectly determined spacing between the container member and the heating coil) are also detected. It has the advantage of being able to be inspected.

[Brief explanation of drawings]

FIG. 1 is a vertical sectional view of a first example of a container to which the present invention is applied, and FIGS. 2 a, b, and c are enlarged vertical sectional views of essential parts showing examples of defects in the joints of the container of FIG. 1. ,
3 is a front view showing a state in which the normal fitting portion of the container shown in FIG. 1 is subjected to high-frequency induction heating in order to implement the present invention; FIG. 4 is a longitudinal sectional view taken along the line - in FIG. 3; Figure 5 is a diagram showing an example of the temperature change over time of a normal fitted part when heated while rotating in the manner shown in Figure 3. FIG. 7 is a front view showing the induced current when the vicinity of the metal-to-metal contact part of the joint is heated. FIG. 8 is an explanatory plan view of an example of a device used to carry out the present invention, and FIG. 9 is a diagram showing an example of a temperature change over time in the device shown in FIG. FIG. 10 is a block diagram of an example of the circuit, and is an explanatory plan view showing a second example of the present invention, which shows a state in which a joint in the body of a container is inspected. 1... Metal container, 2... Upper can body (container member),
2a... Open end (first end), 3... Lower can body (container member), 3a... Open end (second end), 4... Adhesive layer (thermoplastic plastic layer) ), 5... joint part, 5'... fitting part (overlapping part), 6... high frequency induction heating coil, 7, 8...
Induced current, 11...Temperature sensor, 21'...Can body molded body (container member), 25'...Overlapping portion, 2
5'a...Side part (first and second ends), 25
... Side joint part, 26 ... High frequency induction heating coil, 31 ... Temperature sensor.

Claims (1)

[Scope of Claims] 1. A first end portion and a second end portion of a container member having a metal layer.
A method for inspecting a joint formed by overlapping the ends of the two with a thermoplastic layer interposed therebetween to form an overlapping part, and thermally bonding the overlapping part, the method comprising: The high-frequency induction heating coil is connected to the container member so that an induced current is locally induced along the container member, and the directions of the induced current flowing through the first end and the second end of the overlapping portion are opposite to each other. While moving the overlapping portion and the heating coil relatively, the heating coil is energized to perform thermal bonding along the entire length of the overlapping portion, during or immediately after the thermal bonding. A method for inspecting a joint of a container, comprising: detecting the temperature of the joint along the entire length, and determining a range of temperature fluctuation in the length direction of the joint. 2. A patent in which the first end of the container member having a metal layer is the open end of the upper metal can, and the second end of the container member having the metal layer is the open end of the lower metal can. A method for inspecting a joint portion of a container according to claim 1. 3. Inspection of a joint of a container according to claim 1, wherein the container member having a metal layer is a metal can body molded body, and the first end and the second end are opposite side ends. Method.