JP2645897B2 - Inspection method and apparatus for sealed container - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Industrial application field The present invention is fitted with a canned container or canned beverage container formed of a metal material or a lid formed of a metal material. The present invention relates to an inspection method and an inspection device for non-destructively inspecting a bottled container.

(B) Conventional technology The natural vibration of a sealed container having an elastic wall portion when an impact is applied to the wall portion is determined by the shape of the container,
Although it is related to the material, it is also closely related to the magnitude of the internal pressure of the container and the amount of the enclosed contents.

A method of inspecting and determining the quality of a sealed container utilizing such a principle has already been filed by the present applicant (Japanese Patent Application Laid-Open No. 55-63).
731, JP-A-56-14129 and JP-A-57-13329).

In this conventional technique, an electromagnetic impact force is applied to a container wall of a sealed container, and a bounce sound from the container wall due to the impact is detected.

FIG. 2 (A) shows a waveform of a voltage applied to an electromagnetic coil for applying an electromagnetic impact to the container wall of the sealed container.
Alternatively, the shape is as shown in FIG.

The waveform of the vibration sound (the output voltage waveform of the microphone) of the container wall of the sealed container generated at this time has a shape as shown in FIG. 2 (C) or (D). Here, FIG. 2 (C) shows the waveform of the vibration sound of a non-defective vacuum-sealed container, and FIG. 2 (D) shows the waveform of the vibration sound of a defective vacuum-sealed container having a pinhole or the like. Is shown.

As can be seen from these figures, the non-defective product and the defective product have different damped vibration waveforms. In other words, good products have higher frequencies,
While the amplitude is gradually attenuated, in the case of a defective product, the frequency is low, and the amplitude is increased once and then attenuated.

Therefore, the waveform of the vibration sound of the container wall of the sealed container is analyzed,
If the frequency is detected, the quality of the inspected container can be determined.

However, as is apparent from FIGS. 2 (C) and 2 (D), various harmonics are superimposed on the damped oscillation waveform, and it is difficult to accurately judge the quality only by detecting the frequency. Was.

Further, when the center of the electromagnetic coil does not match the center of the container wall of the sealed container, or when the distance between the microphone and the container wall changes, the determination of good or bad has to be further uncertain.

By the way, when the container wall of the sealed container is forcibly vibrated by an electromagnetic coil, the vibration sound of the container wall is converted into an electric signal by a microphone, and when the frequency of the vibration sound is detected, the applied frequency is continuously or When the output voltage from the microphone is gradually increased and analyzed by fast Fourier transform at that time, a frequency spectrum as shown in FIGS. 3A and 3B can be obtained. In this figure, the horizontal axis represents frequency, and the vertical axis represents output voltage (amplitude).

Here, FIG. 3 (A) shows the frequency spectrum of a good product, and FIG. 3 (B) shows the frequency spectrum of a defective product. As is clear from this figure, in the case of a good product, the resonance frequency at the maximum amplitude is slightly higher than 1.5 KHz, and in the case of a defective product,
It can be seen that the co-frequency at the maximum amplitude is around 1 KHz.

(C) Problems to be Solved by the Invention In the conventional technology, an electromagnetic impact force is applied to the container wall of a sealed container to be inspected, and a rebound sound from the container wall due to the impact is detected, and the frequency is detected. Although the analysis was used to determine the quality of the sealed container, as described above, various high-long waves were superimposed on the damped vibration waveform, and it was difficult to determine the quality of the sealed container just by detecting the frequency. Met.

In addition, when the center of the electromagnetic coil does not coincide with the center of the container wall of the sealed container or the distance between the microphone and the container wall changes, the determination of the pass / fail has to be further uncertain.

The present invention has been made in view of the problems of the conventional technology, and has paid attention to the fact that when the container wall of a sealed container is forcibly vibrated by an electromagnetic coil, the resonance frequency at the maximum amplitude differs depending on a good product and a defective product. It is an object of the present invention to provide an inspection method and an inspection apparatus capable of reliably determining the quality in a short time.

(D) Means for Solving the Problems The first main invention is to forcibly vibrate the container wall of a sealed container formed of a metal material by electromagnetic means, and to reduce the vibration sound of the container wall. In a method of converting the frequency of the vibration sound into an electrical signal and detecting the frequency of the vibration sound to check the quality of the sealed container, a sinusoidal electromagnetic wave is generated by the electromagnetic means, and the frequency of the electromagnetic wave is continuously or stepwise. Change, detecting the vibration frequency at the maximum amplitude of the vibration sound of the sealed container, if the vibration frequency is in the first frequency range, determine that the sealed container is good,
If the vibration frequency is in a second frequency range lower than the first frequency range, the sealed container is determined to be defective.

The means for changing the output amplitude of the electromagnetic means in response to the applied frequency or the means for detecting the vibration sound may be provided with automatic gain control means.

A second main invention is to forcibly vibrate a container wall of a sealed container formed of a metal material by electromagnetic means, to convert a vibration sound of the container wall into an electric signal, In a method for detecting the frequency of the hermetically sealed container by detecting a frequency, a sinusoidal electromagnetic wave is generated by the electromagnetic means, and the container wall is moved to a first vibration frequency and the first vibration
When the vibration frequency of the sealed container is increased by applying the electromagnetic vibration force of the first vibration frequency, the sealed container is vibrated separately at a second vibration frequency lower than the vibration frequency of the sealed container. Is judged to be non-defective, and when the amplitude of the vibration sound becomes maximum when an electromagnetic vibration force of the second vibration frequency is applied, the sealed container is judged to be defective.

The means for changing the output amplitude of the electromagnetic means in response to the applied frequency or the means for detecting the vibration sound may be provided with automatic gain control means.

A third main invention is to forcibly vibrate a container wall of a sealed container formed of a metal material by electromagnetic means, convert a vibration sound of the container wall into an electric signal, and convert the vibration sound. In an apparatus for inspecting the quality of the sealed container by detecting a frequency, an electromagnetic coil for applying an electromagnetic vibration force to a container wall of the sealed container, and applying a sinusoidal current at a predetermined frequency to the electromagnetic coil A signal generator, means for continuously or stepwise changing the frequency of the current applied to the electromagnetic coil, a microphone for converting the vibration sound of the vessel wall into an electric signal, and a microphone for converting the electric signal converted by the microphone. Comparing means for detecting a vibration frequency at the time of the maximum amplitude and comparing the vibration frequency with a predetermined frequency, wherein the comparing means determines that the vibration frequency is present in a first frequency region. If the vibration frequency is in the second frequency range lower than the first frequency, the sealed container is not good. It outputs a signal indicating that the product is good.

Note that a power control circuit may be connected to the electromagnetic coil, or an automatic gain control circuit may be connected to the microphone.

(E) Function In the first main invention, the applied frequency of the electromagnetic means is changed continuously or stepwise to detect the vibration frequency at the maximum amplitude of the vibration sound of the sealed container, and when the vibration frequency is high. Then, it is determined that the sealed container is a non-defective product, and when the vibration frequency is low, the sealed container is determined to be a defective product.

If the means for changing the output amplitude of the electromagnetic means in response to the applied frequency or the means for detecting the vibration sound is provided with an automatic gain control means, the detection waveform can be prevented from being distorted.

In the second main invention, a case where the sealed container is vibrated at a high frequency and a case where the sealed container is vibrated at a low frequency are compared,
When the amplitude of the vibration sound is maximized when a high frequency electromagnetic vibration force is applied, the sealed container is determined to be good, and when the low frequency electromagnetic vibration force is applied, the amplitude of the vibration sound is reduced. When it reaches the maximum, it is determined that the sealed container is defective.

If the means for changing the output amplitude of the electromagnetic means in response to the applied frequency or the means for detecting the vibration sound is provided with the automatic gain control means, the detection waveform can be prevented from being saturated.

The operation of the third main invention is not substantially different from the operation of the first main invention.

(F) Embodiment FIG. 1 is a perspective view of an apparatus embodying the present invention, FIG. 4 is a block diagram of its control system, FIG. 5 is a schematic sectional view of a canned beverage container (vacuum sealed container), FIG. FIG. 6 is an equivalent circuit diagram corresponding to FIG.

In FIG. 1, reference numeral 1 denotes a canned beverage container in which drinking water such as juice is sealed, which is placed on a belt conveyor 2 and continuously conveyed.

An inspection section 3 is provided above the belt conveyor 2, and the canned beverage container 1 is transported so as to sequentially pass below the inspection section 3 as shown by an arrow in FIG.

The inspection unit 3 is surrounded by a shield housing 4, and a light source 5 and a photo sensor 6 are opposed to each other on both sides of the shield housing 4 parallel to the moving direction of the canned beverage container 1. Is provided.

As shown in FIG. 4, the inspection unit 3 includes an electromagnetic coil 8 attached to a lower end of a cylindrical plastic cylinder 7.
And a microphone 10 inserted from the upper part of the plastic cylinder 7 toward the sound collection hole 9.

The photo sensor 6 is electrically connected to the determination / timing control unit 11. In addition, the judgment
The timing control unit 11 is also electrically connected to the waveform generator 12 and the power drive 13, and the waveform generator 12 is connected to the power drive 13 and the power drive 13.
Are electrically connected to the electromagnetic coil 8. Furthermore,
The microphone 10 is also electrically connected to the determination / timing control unit 11.

On the belt conveyor 2 downstream of the inspection unit 3, the defective canned beverage container 1 is electrically connected to the determination / timing control unit 11 for removing the defective canned beverage container 1 to the side of the belt conveyor 2. The selected sorting mechanism 14 is provided. The sorting mechanism 14 is provided with an air cylinder and an electromagnetic valve. In response to a signal indicating a defective product from the determination / timing control unit 11, an excluding piece 16 fixed to the piston 15 is placed on the belt conveyor 2. To remove the defective canned beverage container 1 as described above.

Thus, the light beam emitted from the light source 5 to the photosensor 6 is blocked by the canned beverage container 1, and it is detected that the canned beverage container 1 has arrived at the lower portion of the electromagnetic coil 8, and the detection signal is used as the determination signal. When the signal is supplied to the timing control unit 11, a signal is supplied from the determination / timing control unit 11 to the waveform generator 12.

Then, from the waveform generator 12, several hundred H
A signal having a frequency from z to several KHz is continuously output and supplied to the power drive 13. When the above-described signal is supplied to the power drive 13, a voltage having the above-described frequency is applied to the electromagnetic coil 8 from the power drive 13. When the voltage is thus applied to the electromagnetic coil 8, the electromagnetic coil 8 generates a magnetic flux, and the container wall of the canned beverage container 1 facing the electromagnetic coil 8 is forcibly vibrated by the magnetic force generated at this time. Can be

As shown in FIG. 5, a schematic cross-sectional view of the canned beverage container 1 includes a disk-shaped upper container wall 1a, a lower container wall 1b, and a cylindrical peripheral container wall 1c. Container wall 1a and peripheral container wall 1c, lower container wall 1b and peripheral container wall 1c
Are wound and fixed by the winding portions 1d and 1e. In addition, a fixed amount of drinking water is
17 is enclosed, and a space 18 is formed on the top of the space.

Thus, when an AC voltage is applied to the electromagnetic coil 8 and the upper container wall 1a is electromagnetically attracted, the mass of the upper container wall 1a is m, the resistance of the tightening portion 1d is r, and the can beverage container 1 The mechanical impedance Z is given by: (Where ω is each frequency and j is an imaginary unit). An equivalent circuit expressing this relationship is shown in FIG.
FIG.

The relationship between the voltage applied to the magnetic coil 8, the magnetic flux of the magnetic coil 8, the suction force of the upper container wall 1a, and the output voltage from the microphone 10 is as shown in the waveform of FIG. That is, the frequency of the output voltage from the microphone 10 is twice the frequency of the voltage applied to the electromagnetic coil 8.

Therefore, as described above, several hundred Hz from the power drive 13
Or a voltage of a frequency of several KHz to the electromagnetic coil 8 continuously.
(See FIG. 8 (A)), the microphone
10 outputs a voltage having a waveform as shown in FIG. 8 (B).

9 (A), (B) and (C) show various kinds of good and defective canned beverage containers 1 positioned below the electromagnetic coil 8,
9 is a graph showing frequency characteristics obtained when a voltage having a frequency as shown in FIG. 8A is continuously applied to the electromagnetic coil 8.

FIG. 9 (A) is a graph when the canned beverage container 1 is a good product. As is clear from this graph, in the case of a good product, the resonance frequency (vibration frequency) at the maximum amplitude is about 2 KHz.

FIG. 9 (B) shows defective products (solid line), defective internal pressure (dotted line), and non-defective products (two-dot chain line) related to internal pressure failure caused by leakage. It is a graph in a case. As is evident from this graph, in the case of a defective product related to internal pressure failure caused by leakage, the resonance frequency at the maximum amplitude is about 1 KHz,
It can be seen that the resonance frequency at the maximum amplitude is about 1.3 KHz in the case of a defective product due to a general internal pressure defect.

Further, FIG. 9 (C) shows a defective product (dotted line) relating to the internal pressure defect caused by the leak of the canned beverage container 1, and a defective product (solid line) relating to the internal pressure defect caused by the excessive amount of the internal solution. It is a graph in a case. As is evident from this graph, the resonance frequency at the maximum amplitude is about 1 KHz for both the defective product due to the internal pressure defect caused by the leak and the defective product due to the internal pressure defect caused by too much internal solution. It turns out that it becomes.

From the above results, the resonance frequency at the maximum amplitude of a good product is 2K
It can be understood that the resonance frequency at the maximum amplitude of the defective product is between 1 KHz and 1.5 KHz around Hz.

Therefore, the resonance frequency at the maximum amplitude of the canned beverage container 1 to be inspected is detected, and when the vibration frequency is around 2 KHz, the canned beverage container 1 is determined to be non-defective and the resonance frequency is 1 KHz. If it is between 1.5 and 1.5 KHz, the canned beverage container 1 may be determined to be defective.

By detecting the resonance frequency at the maximum amplitude more finely, or by detecting so-called Q (ωL / R), it is possible to know the type of the defective form.

Therefore, in the present embodiment, a memory is built in the determination / timing control unit 11, and information in the first frequency region around 2 KHz and information in the second frequency region from 1 KHz to 1.5 KHz are stored in the memory. Have been.

Then, the above-described voltage is applied to the electromagnetic coil 8, the output voltage from the microphone 10 is compared with the information stored in the memory, and the resonance frequency of the upper container wall 1a at the maximum amplitude is 2 KHz. In the area before and after,
When it is determined that it does not exist in the range of 1 KHz to 1.5 KHz, the canned beverage container 1 is determined to be a good product.

On the other hand, the resonance frequency of the upper container
If it is determined that the can beverage container 1 exists in the region of 1.5 KHz and does not exist in the region of approximately 2 KHz, the canned beverage container 1 is determined to be defective, and the sorting mechanism 14 operates, The beverage container 1 is removed from the belt conveyor 2 as described above.

Further, an electromagnetic vibration force in a first frequency region of about 2 KHz and an electromagnetic vibration force in a second frequency region of 1 KHz to 1.5 KHz are separately applied to the upper container wall 1a, and the electromagnetic force in the first frequency region is applied. When the vibration force is applied, if the amplitude of the upper container wall 1a is maximized, the canned beverage container 1 is determined to be good, and when the electromagnetic vibration force in the second frequency range is applied, the upper container When the wall 1a amplitude becomes the maximum, it is possible to determine that the canned beverage container 1 is defective.

The first frequency range and the first frequency range vary depending on the type of the container to be inspected and the substance sealed therein, but generally, the first frequency range is 1 KHz or more.
Set to a range below 3KHz, the second frequency range is 0.5KHz
It is set in the range of 2 kHz or less.

Next, a second embodiment will be described with reference to FIGS. 10 to 12, but before that, the relationship between the output of the electromagnetic coil 8 and the power applied to the electromagnetic coil 8 will be described. Assuming that the output of the electromagnetic coil 8 is P, the applied voltage is v, and the frequency is f, the following relationship holds: P = Kv ² / f (K is a constant). As is clear from this equation, when the applied voltage v is constant, the output P increases when the frequency f is low, and decreases when the frequency f is high.

Therefore, in the first embodiment described above, when the voltage (output amplitude) applied to the electromagnetic coil 8 is constant, the output voltage from the microphone 10 is in the second frequency range (around 1 KHz in FIG. 9). ), The waveform is saturated and the waveform is saturated, and a defective product may not be accurately detected.

Therefore, when the voltage applied to the electromagnetic coil 8 is reduced, the output voltage from the microphone 10 becomes extremely low in the first frequency region (around 2 KHz in FIG. 9), and a good product is accurately detected. There are cases where it is not possible.

Therefore, in the second embodiment, a power control circuit 17 is connected to the electromagnetic coil 8 as shown in FIG. 10, and when the frequency is low as shown in FIG. 11 and FIG. The voltage is controlled to be low, and when the frequency is high, the applied voltage is controlled to be high. FIG. 11 shows a state in which the frequency changes continuously, and FIG. 12 shows a state in which the frequency changes stepwise.

With this configuration, the microphone 10
Is slightly lower in the second frequency region (around 1 KHz in FIG. 9) and the waveform does not saturate, and the output voltage from the second frequency region (around 2 KHz in FIG. 9) does not increase. In the region (a), the height is slightly higher, so that a good product and a defective product can be more accurately detected.

Note that the output voltage from the microphone 10 is
An automatic gain control circuit (AGC circuit) 18 such as a log amplifier may be connected to the microphone 10 in order to control the frequency slightly lower in the frequency region of FIG.

In the second embodiment, as shown in FIG.
A power control circuit 17 is connected to the electromagnetic coil 8, and an AGC circuit 18 is connected to the microphone 10.
It is not always necessary that 8 is provided at the same time, and depending on the use, even if only one of them is provided, it may be sufficiently practical.

(G) Effects of the Invention In the present invention, the quality of the sealed container can be determined with high accuracy because it is not affected by harmonics.

Further, accurate determination can be made even if the center of the electromagnetic coil does not coincide with the center of the container wall of the sealed container.

Further, even if the distance between the microphone and the container wall of the sealed container changes, the determination can be made without being affected by the change.

Furthermore, by detecting the so-called Q and the shape of the frequency characteristic, it is possible to identify a failure mode (leakage, deformation, excessive content, etc.) which could not be identified conventionally.

If a means for changing the output amplitude of the electromagnetic means in response to the applied frequency or an automatic gain control means is provided for the vibration sound detection means, the waveform of the vibration sound is saturated and defective products can be detected. There is no such thing that the sound pressure level is too low and a good product cannot be detected, and a defective product can be detected more accurately and efficiently.

[Brief description of the drawings]

FIG. 1 is a perspective view of an apparatus according to an embodiment of the present invention, FIG. 2 is a waveform diagram of an output voltage of a microphone, FIG. 3 is a spectrum diagram of an output voltage from an output voltage of a microphone, and FIG. FIG. 5 is a sectional view of a canned beverage container, FIG. 6 is an equivalent circuit diagram corresponding to FIG. 5, FIG. 7 is a coil applied voltage, a magnetic coil magnetic flux, and suction of an upper container wall. Waveform diagram of force and microphone output voltage, 8th
FIG. 9 is an input and output voltage waveform diagram, FIG. 9 is a frequency characteristic diagram, FIG. 10 is a block diagram of a device according to a second embodiment of the present invention,
FIG. 11 and FIG. 12 are waveform diagrams of the applied voltage in the device of the second embodiment. 1 ... canned beverage container (sealed container), 1a ... top container wall, 1b
... Upper container wall, 1c ... Peripheral container wall, 1d, 1e ... Winding unit, 2 belt conveyor, 3 ... Inspection unit, 4 ... Shield housing, 5 ... Light source, 6 ... Photosensor , 7 ... Plastic cylinder, 8 ... Electromagnetic coil, 9 ... Sound hole, 10 ...
… Microphone, 11… Judgment / timing control unit, 12 …… Waveform generator, 13 …… Power drive, 14 …… Sorting mechanism, 15 …… Piston, 16 …… Removal piece,
17: Power control circuit, 18: AGC circuit.

 ──────────────────────────────────────────────────続 き Continuation of the front page (56) References JP-A-50-160085 (JP, A) JP-A-53-81284 (JP, A) JP-A-54-146676 (JP, A) 130081 (JP, A) JP-A-55-63731 (JP, A) JP-A-56-14129 (JP, A) JP-A-57-13329 (JP, A)

Claims (12)

(57) [Claims] 1. A container wall of a hermetically sealed container formed of a metal material is forcibly vibrated by electromagnetic means to convert a vibration sound of the container wall into an electric signal and detect a frequency of the vibration sound. In the method of inspecting the quality of the sealed container by generating a sinusoidal electromagnetic wave by the electromagnetic means,
The frequency of the electromagnetic wave is changed continuously or stepwise, the vibration frequency at the maximum amplitude of the vibration sound of the sealed container is detected, and when the vibration frequency exists in the first frequency region, Determining that the sealed container is a non-defective product, and determining that the sealed container is a defective product when the vibration frequency is present in a second frequency range lower than the first frequency range. Inspection method for sealed containers. 2. A container wall of a sealed container formed of a metal material is forcibly vibrated by electromagnetic means to convert a vibration sound of the container wall into an electric signal and detect a frequency of the vibration sound. In the method of inspecting the quality of the sealed container by generating a sinusoidal electromagnetic wave by the electromagnetic means,
The container wall is vibrated separately at a first vibration frequency and a second vibration frequency lower than the first vibration frequency, and the vibration sound of the sealed container applies an electromagnetic vibration force of the first vibration frequency. When the amplitude is maximized when the sealed container is judged to be good, the sealed container is considered to be non-defective when the amplitude is maximized when the vibration sound applies the electromagnetic vibration force of the second vibration frequency. A method for inspecting a sealed container, comprising determining that the container is defective. 3. The method according to claim 1, wherein the first vibration frequency is set in a range from 1 KHz to less than 3 KHz, and the second vibration frequency is set in a range from 0.5 KHz to less than 1 KHz.
Inspection method for the sealed container as described. 4. The method according to claim 1, wherein the output amplitude of the electromagnetic means changes in response to an applied frequency. 5. The method for inspecting a sealed container according to claim 4, wherein the output amplitude of the electromagnetic means is large in the first vibration frequency region and small in the second vibration frequency region. 6. The inspection method for a sealed container according to claim 4, wherein the output power of the electromagnetic means is substantially constant. 7. The method for inspecting a sealed container according to claim 1, wherein an automatic gain control means is provided in the vibration sound detecting means. 8. A container wall of a hermetically sealed container formed of a metal material is forcibly vibrated by an electromagnetic means, and the vibration sound of the container wall is converted into an electric signal, and the frequency of the vibration sound is detected. An apparatus for inspecting the quality of the sealed container, comprising: an electromagnetic coil for applying an electromagnetic vibration force to a container wall of the sealed container; and a signal generator for applying a sinusoidal current at a predetermined frequency to the electromagnetic coil. Means for continuously or stepwise changing the frequency of the current applied to the electromagnetic coil, a microphone for converting the vibration sound of the container wall into an electric signal, and a maximum amplitude of the electric signal converted by the microphone. And a comparing unit that detects the vibration frequency of the vibration frequency and compares the vibration frequency with a predetermined frequency. The comparison unit determines that the vibration frequency is present in a first frequency range. If the vibration frequency is in a second frequency range lower than the first frequency, the sealed container is defective. An inspection device for a sealed container, which outputs a signal to the effect that the above is true. 9. A power control circuit connected to the electromagnetic coil for controlling the output amplitude of the electromagnetic coil to be large in the first vibration frequency region and small in the second vibration frequency region. Item 9. An inspection device for a sealed container according to Item 8. 10. The inspection apparatus for a sealed container according to claim 8, wherein an automatic gain control circuit is connected to the microphone. 11. The first frequency range is set within a range of 1 KHz to 3 KHz, and the second vibration frequency is set to a range of 0.5 KHz to 2 KHz.
Claims 8 to 10 set within the range of less than
The inspection device for a sealed container according to any one of claims 1 to 7. 12. The method according to claim 8, further comprising a conveying means for continuously or intermittently conveying the sealed container, and a defective product eliminating means for eliminating a defective sealed container. The inspection device for a sealed container according to the above.