JPS6138812B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention uses a microphone or electromagnetic method to detect vibrations of a metal lid caused by applying a magnetic impact force to the lid of a sealed container having a metal lid, such as a can. Then, the vibration of the metal lid is input as an electrical signal to a bandpass filter arranged in large numbers, and from among the frequency components distributed in the electrical signal,
The present invention relates to an internal pressure inspection device for a sealed container that performs spectrum analysis, extracts fundamental frequency components and harmonic components, and performs arithmetic processing on the signals to reliably determine the quality of the sealed container.

The conventional canned internal pressure inspection method is to measure the vibration frequency from the waveform signal obtained from the vibration of the can lid during canning through a single or multiple filters, and check whether it is within a set frequency range. Generally, a method is used to determine the quality of the product. but,
Defective cans that actually occur include, for example, in the case of normal cans with a predetermined negative pressure, internal pressure leaks due to insufficient filling temperature or incomplete seaming, resulting in low negative pressure or atmospheric pressure. These include expansion cans and deformed cans whose internal pressure becomes positive for some reason. Regarding sample examples of these defective cans, the first
2 and 2 show waveform diagrams obtained by spectral analysis and measurement of the detection signal waveform during canning.

In each of these figures, the horizontal axis represents the frequency on an equal division scale, and the vertical axis represents the signal level on a logarithmic scale. In the case of a can whose internal pressure is near the lower limit of the normal value range, in Figure 1 c, the internal pressure is zero, and in Figure 2, the seal is incomplete due to poor seaming, and in both cases the internal pressure is on the positive side. The example of a can is shown in the figure a when the internal pressure is relatively low, b when the absolute value of the internal pressure is a positive pressure corresponding to a normal can, and c when the internal pressure is even higher and the can is in an expanded state close to the bursting pressure. In some cases.

In each of the above figures, when the frequency f ₁ indicating the maximum peak and the peaks following it are plotted in order and the frequencies are f ₂ , f ₃ , f ₄ from the lowest frequency, f ₁
A multiplier α of 2.4 to 3 can be found from the relationship of the frequency value of f ₄ to . In other words, the frequency component around α・f ₁ is
If the wave harmonic is f ₄ , then by looking at the ratio of the level PH of f ₄ to the level PL of fundamental frequency f ₁ , you can tell whether it is the can shown in Figure 1 or the expansion can shown in Figure 2. It can be seen from a large number of other similar data that this is a means of

Therefore, when simply measuring one frequency as in the conventional method, it is difficult to determine f ₄ because part or all of the frequency components consisting of a large number of frequencies are measured as a whole as described above. Figure 2b
The expansion canister has almost the same judgment result as the normal canister shown in FIG. 1b, and the reliability of the test is poor. In addition, in the case of conventional inspection methods, when there is a second wave frequency component _f2 that shows a large peak next to the fundamental frequency, the measurement of the fundamental frequency is also affected by the measurement timing, and the measurement results are unstable. This may also be the cause of the value being shown. This means that it is necessary to take into account the range of variation in the permissible limit of negative pressure, which reduces the reliability of the test.

Furthermore, from the spectrum analysis of a large number of cans, it has been found that the frequency of the first peak does not necessarily show a low value between the frequency of the first peak and the frequency of the second peak. Now, it can be seen that highly accurate inspection cannot be expected due to the inclusion of unstable elements.

The purpose of the present invention is to eliminate the drawbacks of the prior art as described above, and to be able to detect not only cans with no negative pressure, but also cans with a slight lack of negative pressure, and to detect bulging cans or cans caused by poor seaming. It is an object of the present invention to provide a can inspection device that can also detect cans exhibiting an abnormality in can lid surface vibration due to deformation and provides good and stable inspection performance.

The feature of the present invention is that the fundamental frequency component and the fourth frequency component effective for determination are detected from the vibration detection signal during canning of a can at a predetermined position based on the position detection signal.
In order to reliably separate and extract wave harmonic components, two bands are provided: a low frequency band in which the fundamental frequency component is distributed and a high frequency band in which the harmonic components are distributed. , and band-pass filters with different frequencies are arranged to subdivide the waves.

In this way, the effect obtained by arranging a large number of bandpass filters in two groups, low and high, is the maximum peak level of the signal obtained from the bandpass filter on the low side, or the second largest peak level. By detecting a filter that indicates , and selecting the filter that extracts a low frequency from both filters, it is possible to reliably find the fundamental frequency and detect its signal level at the same time. In addition, from among the signal outputs of many bandpass filters from the high-frequency side filter group, the fundamental frequency can be calculated and the frequency of the fourth harmonic and its signal level can be accurately detected. It is possible to set fine-grained judgment conditions that adapt to the unique frequency components and levels of cans, and it is possible to reliably inspect defective cans.

Next, an embodiment of the present invention is shown in FIGS. 3 and 4.

In FIG. 3, when the can C to be inspected is hammered by magnetic or other electrical means, the can lid surface vibrates. This vibration phenomenon is detected by a vibration detector TS using acoustic or magnetic means. This detector TS
outputs an electrical signal corresponding to the vibration of the can lid surface, amplifies it with the preamplifier PA, and sends it to the low bandpass filters FL ₁ to FL _o and the high bandpass filter
Input in parallel to FH ₁ to _{FH o} .

Each of the band pass filters can pass only vibration signals within a predetermined band, so the output signal of each filter is separated from the frequency components of the can signal and outputs each signal, and at the same time, the frequency value is determined. It will be done. The signals attenuated by these filters are amplified by level amplifiers LA ₁ to LA _o and HA ₁ to _{HA o} , and output to the pattern analysis and determination circuit D.

Next, the contents of FIG. 4 showing an example of the pattern analysis and determination circuit D will be explained.

The levels are compared among the output signals of the level amplifiers LA ₁ to LA _o , which amplify the levels of the low band pass filters FL ₁ to FL _o , respectively, and the maximum peak signal PL _n and the second highest level are determined. The peak signal PL _n ′ is selected, and the respective frequencies FL _n and FL _n ′ at that time are detected.

When the maximum peak signal PL _n detected above is below the reference level PS, it is assumed that the test signal is insufficient due to the can being turned upside down, the lid is deformed, the can is completely filled, etc., and a fault signal is issued. When PS < PL _n , Proceed to next step.

The two frequencies FL _n and
Compare FL _n ′ and select the lower frequency,
This is set as the fundamental frequency _f1 , and the signal level at that time is detected as PL.

If only one peak frequency signal is detected above, this is set as the fundamental frequency f ₁ and PL.

It is compared whether f ₁ obtained above is within the range of a preset normal internal pressure frequency limit value f _s , and if it is outside the range, it is determined that the can is under-internal pressure, and a defect signal is issued.

If it is within the range, proceed to the next step.

The fourth harmonic frequency f ₄ is required to be α times the fundamental frequency f ₁ (α = 2.0 to 3.0), so calculate α・f ₁ and select the high-frequency bandpass filter FH. ₁ ~ FH _o each level amplifier HA ₁ ~ _{HA o}
The corresponding signal is selected from among the signals, and the harmonic frequency FH and the same signal level PH are detected.

If the harmonic signal level PH obtained above is smaller than the value calculated by multiplying the fundamental frequency level PL by a specific multiplication factor γ (decimal number), then it is considered a good can. PH＞γ・
If it is PL, it is determined to be an expansion canister and a fault signal is issued.

In this way, low negative pressure cans, expansion cans, etc. are detected, but even if the can body or can lid is significantly deformed, it can be detected using the same method.

Incidentally, the processing method after issuing the defective can signal, the can firing method, the can position detection method, the timing generation method, etc. are the same as in the conventional method, and the explanation thereof will be omitted.

As described above, according to the internal pressure testing device for a sealed container of the present invention, vibration of the lid of a sealed container, which is invented by applying a magnetic or other impact force to the lid of a sealed container having a metal lid, is achieved. a vibration detector for detecting a vibration detector; a plurality of bandpass filters each having a band in which adjacent frequencies of each band are connected or overlapped with each other to which the output electric signal of the detector is input; and each output signal of each of the bandpass filters. a comparison means for mutually comparing the maximum level signal and the second highest level signal detected by the comparison means;
a first selection means for selecting a filter having a lower frequency among the two filters, a second selection means for selecting a frequency and a level detected from the filter with a lower frequency as a fundamental frequency signal; a third selection means for selecting a filter of a frequency band corresponding to a value multiplied by a specific numerical value of 2 or 3; and a frequency and level detected from the filter selected by the third selection means are selected as a harmonic signal. A fourth selection means calculates and processes the fundamental frequency signal and the harmonic signal, and satisfies the following conditions: a. When the level of the maximum level signal is below the reference level; b. When the frequency of the fundamental frequency signal is outside a preset frequency range; c. A determination means for determining whether the sealed container is defective and outputting a defective signal when the ratio of the level of the harmonic signal to the level of the fundamental frequency signal is greater than a reference value is provided. Reliable detection of cans can be obtained, especially after a certain storage period has elapsed after canning production, and low negative pressure due to slow leakage of built-in cans and expansion cans can be detected without opening the top of the case during inspection at the time of shipment. Its effectiveness is demonstrated when applied to inspections.

[Brief explanation of the drawing]

Figures 1 and 2 are frequency spectrum analysis results of the vibration detection signal of the lid during canning. Figure 1 a and b are examples of normal cans, and Figure 1 c is an example of non-negative pressure cans. , FIGS. 2a, b, and c are examples of each expansion can. FIG. 3 is a block diagram of an embodiment of the internal pressure testing device for a sealed container according to the present invention, and FIG. 4 is a block diagram showing the processing procedure of the arithmetic determination circuit in the pattern analysis determination circuit in FIG. C... Can to be inspected, TS... Vibration detector, FL ₁ ~
FL _o ...Low band pass filter, FH ₁ ~FH _o ...
...High bandpass filter, LA ₁ ~ LA _o ... Level amplifier, HA ₁ ~ HA _o ... Level amplifier, D...
Pattern analysis judgment circuit.

Claims (1)

[Scope of Claims] 1. A vibration detector for detecting vibrations of a lid of a sealed container having a metal lid, which is generated by applying a magnetic or other impact force to the lid of the sealed container; a plurality of band-pass filters each having a band in which the output electric signal of the band-pass filter is inputted and adjacent frequencies of each band are connected or overlapped with each other; a comparison means for mutually comparing each output signal of each of the band-pass filters; a first selection means for selecting two filters that have detected the maximum level signal and the second highest level signal by the comparison means; and a first selection means for selecting the two filters that have detected the maximum level signal and the second highest level signal; a second selection means for selecting a frequency signal; a third selection means for selecting a filter of a frequency band corresponding to a value obtained by multiplying the frequency of the fundamental frequency signal by a specific numerical value of 2 or 3; and the third selection means. a fourth selection means for selecting the frequency and level detected from the filter selected by the filter as a harmonic signal; and calculating the fundamental frequency signal and the harmonic signal to satisfy the following condition a: the level of the maximum level signal is below the reference level. b When the frequency of the fundamental frequency signal is outside the preset frequency range c When the ratio of the level of the harmonic signal to the level of the fundamental frequency signal is greater than the reference value, the sealed container is determined to be defective. 1. A device for inspecting internal pressure of a sealed container, comprising: determining means for performing the following steps and outputting a defect signal.