JPS6027833A - Method and apparatus for inspecting leakage of tightly sealed container - Google Patents

Abstract

PURPOSE:To inspect the leakage of a container automatically during the filling process of beverage, by optically measuring the size of the outer surface of a flexible container, which is filled with a beverage in a hot state and tightly sealed, and computing the value. CONSTITUTION:A flexible container 101, which is filled with a beverage in a hot state and tightly sealed, is conveyed by a conveyer 102. Then laser distance meters 103a and 103b digitally measure the distance to the central part of the container 101. At the same time, the number of stepping X measured by an encoder 104 and the measured values Ya and Yb of the distance meters 103a and 103b are stored in a memory device 106. The difference Di between Ya and Yb is obtained by an adding device 107. The sum of the differences Di over the entire pulses (number of stepping) of the encoder 104 is obtained. The cross sectional area of the central part of the drum of the container 101 is compared with a preset value from a judging-level setting device 109 by a comparator 110. When the area exceeds the preset value, a defect signal is sent to excluding device. Thus the leakage of the container 101 is automatically inspected.

Description

Detailed Description of the Invention The present invention relates to a container having an elastic or flexible outer wall made of paper, plastic, metal foil such as aluminum, or a composite material thereof, filled with contents such as food or drink, and sealed. The present invention also relates to a leak testing method and apparatus for a sealed container, which tests for leakage due to a seal failure in the container or a pinhole in the material.

In recent years, bags have been made of sheet materials that have a certain degree of flexibility and shape retention, and are made of paper-based laminates using plastic film, aluminum foil, etc., as containers for filling beverages such as fruit juice or coffee. Containers shaped like boxes or cylinders are being put into practical use. However, conventional leakage inspections for these containers have been carried out by human estimation of wetness due to liquid leaking from the containers, and accurate and automatic leakage inspection has been difficult.

As an automatic inspection method for containers made of this type of sheet material, there is an automatic percussion method, which is used to detect leakage of metal cans, and the deformation of the lid surface due to the internal pressure of the container. It is also possible to use a method of determining the amount of deflection by measuring it with a proximity rangefinder.

However, the former method is only effective for metal lids where the free vibrations of the lid are attenuated over a sufficiently long period of time.
It was not possible to apply this method to materials such as plastic and paper whose free vibration damps extremely quickly. In the latter method, in addition to the lid surface, which is planned to deform in advance, the container must have a reference part that will not be deformed by the internal pressure of the container, and the shape of the deformation must always be constant with the internal pressure of the container. It could only be applied if there was a relationship between

As described above, it has been difficult to use the conventional method used for leak testing of metal cans for leak testing of containers made of paper-based sheet materials.

Usually, beverages are hot filled into containers at a high temperature of about 90° C. to 95° C., sealed, and then cooled.

The present invention utilizes the property that the volume of the contents contracts during cooling, reducing the internal pressure of the container, and easily deforming the flexible wall surface of the container due to the pressure difference. The object of the present invention is to provide a method and apparatus for automatically inspecting container leakage during a beverage filling process.

First, the principle of the present invention will be briefly explained.

When a hot beverage is filled into a container, sealed, and then cooled,
The inside of the container becomes under reduced pressure. At this time, if a defective container has a leakage point such as a pinhole or a defective seal, external air will flow into the container from that point and the pressure difference inside and outside the container will be approximately the same, so the container will hardly be deformed. . On the other hand, in a normal container with no leakage points such as pinholes or seal failures, the reduced pressure inside the container causes the flexible wall surface to bend inward, reducing its volume. Therefore, by measuring the outer circumferential shape of the container including the flexible wall surface using optical means, performing a predetermined calculation, and determining whether the measured value is larger than a certain value, the container can be measured. This is to determine whether there is a leak.

Hereinafter, the present invention will be explained based on examples.

The container 101 in the example is made of a base paper with a thickness of 0.3 m, an outer layer of polyethylene of 50 μm, an inner layer of polyethylene of 30 μm and an aluminum foil of 15 μm, and an innermost layer of 50 μm of polyethylene.
Width: 171, laminated with 0μ polyethylene adhesive.
+mn, a rectangular sheet material with a height of 130 cm, a diameter of 53 cm
The body of the peephole is rolled into an almost cylindrical shape and heat-bonded, and the thickness is 10 mm.
It consists of a lid that is press-molded into a circular dish shape using a sheet made of 0μ aluminum foil, laminated with 50μ polyethylene on the inside, and coated with 5μ epoxy phenol paint on the outside.This lid is attached to a cylindrical body. It is formed by thermally adhering it to both ends. In addition, six folds are pre-processed at equal intervals in the longitudinal direction of the body so that when the pressure inside the container is reduced, the cross-sectional area of the body becomes almost a regular hexagon. The deformation caused by the reduced pressure inside the container appears largely in the center of the body along the above-mentioned folds, and is less likely to occur at both ends, which are hardened by thermal adhesion to the lid. Therefore, the deformation of the torso,
In other words, a decrease in the volume of the entire container can be typically detected at the center of the body.

FIG. 1 shows a first embodiment of the present invention, in which the deformation of the container is measured as a decrease in the cross-sectional area of the body, and the container is tested for leakage based on the size of this cross-sectional area.

In FIG. 1, a conveyor 102 is moved in the direction of arrow X by a drive device (not shown) to convey the container 1()1. 103a and 103b are laser distance meters,
They are disposed on both sides of the conveyor 102 in the right angle direction, facing each other at equal distances. This laser distance meter 103a
, 103b digitally measure the distance to the center of the container 101 with an accuracy of 1w+m, one as a positive value and the other as a negative value. This is an encoder that emits a pulse signal corresponding to the moving distance of the conveyor 102, and measures the moving distance of the conveyor 102 with an accuracy of 0.1 m.

Reference numeral 105 denotes an arithmetic unit consisting of a storage device 106 and an addition device 107, which inputs measured values from a pair of laser distance meters 103a and 103b for each pulse of the encoder 104, and stores them in the storage device 106. This memory device 7i
The values in 106 indicate the coordinate values of the shape and dimensions of the cut surface at the center of the body of the container 101. Reference numeral 108 denotes an X-Y plotter that plots the cross-sectional shape of the central portion of the body of the container 101 using six values stored in the storage device 106. 110 is a digital comparator,
The cross-sectional area value set in the discrimination level setting device 109 consisting of a digital switch is compared with the cross-sectional area value from the calculation device 105, and the cross-sectional area value from the calculation device 105 is larger than the cross-sectional area value of the level setting device 109. A defective determination signal is issued if the

Next, the inspection method in the first embodiment will be explained.

The container 101 is placed on a conveyor 102 in an upright position and conveyed. A pair of laser rangefinders 103a and 103b are
The zero point is calibrated in advance with a thin piece of paper placed approximately in the center of the conveyor 102, so that one rangefinder outputs a positive value and the other rangefinder outputs a negative value.

The measured values by the laser rangefinders 1038 and 103b are stored in the memory with the value of one laser rangefinder 103a being ya and the value of the other laser rangefinder 103b being yb, where the number of steps of the encoder 104 is X. 106.

That is, the container on the conveyor 102 is the laser distance meter 10
A pair of laser range finders 103a, 103 until the laser beams 3a, 103b hit the position.
The measured values of b indicate +■ and -ω, respectively, but when the front end of the container 101 moves to the position where it hits the laser beam, the laser range finders 103 a and 103 b
indicates the coordinate values ya and yb. Therefore, this value is triggered every pulse of the encoder 104 and input to the storage device 106. This input is the laser rangefinder 1
The measured values of 03a and 103b are again + and -ω
It will continue until you instruct it. In this manner, the coordinate values of the shape and dimensions of the cut surface of the center portion of the body of the container 101 are stored in the storage device 106.

FIG. 2 shows the six values in the storage device 106
Figure 2 (a) is the figure output to 08 and drawn.
In the case of a normal container with no leakage points, the center of the body is approximately regular hexagonal. FIG. 2(b) shows a defective container with a leakage point due to poor thermal adhesion of the lid, and the center of the body is almost circular.

On the other hand, the adding device 107 uses the value ya in the storage device 106 in order to calculate the cross-sectional area S of the central portion of the body of the container 101.

The sum of the differences in yb is calculated based on the formula S=Σte'(ya-Yb). Table 1 shows the cross-sectional areas of 10 normal containers and 10 defective containers determined by the adding device 107.

Table 1 Cross-sectional area of the body of normal containers and defective containers As can be seen from Table 1, in the case of normal containers, the average cross-sectional area shrank by 181♂, and this value is much larger than the dispersion of the measured values. big. Therefore, it can be seen that the cross-sectional area can be used as an index to determine the quality of the container with sufficient accuracy.

The cross-sectional area value of the container calculated in this way is compared with the set value from the discrimination level setter 109 in the digital comparator 110. Then, when the value from the arithmetic unit 105, that is, the measured value, is larger than the set value, a container defect determination signal is output to a removal device (not shown), and the defective container is removed from the conveyor 102.

FIG. 3 shows a second embodiment of the present invention. Considering that the container is deformed into a predetermined shape, the leakage test of the container is performed based on the planned number of irregularities in the body and the degree of the irregularities. This is what we do.

In FIG. 3, 202 is a rotary table, and a drive motor 203
is rotated in one direction around the central axis 2. The container 101 is placed on the top of the rotary table 202 with the central axes 2 aligned. An encoder 204 is provided coaxially with the drive motor 203, and outputs a pulse signal obtained by dividing one rotation of the rotary table 202 into 1024 equal parts. 206
is a laser rangefinder placed opposite the center of the body of the container 101 to measure the distance to the body of the container 101.

A 205U arithmetic unit has a storage device 207 that sequentially stores the measured values of the laser distance meter 206 for each pulse of the encoder 204, and the 1024 measured values in the storage device 207 are regarded as time series data in a - period and are divided into frequency components. It is composed of a Fourier transform calculator 208 that performs calculations, and an output register 209 that holds the sixth harmonic term in the calculation result by the Fourier transform calculator 208. 211 is a digital comparator that compares the value set in the discrimination level setter 210 consisting of a digital switch and the value from the output register 209, and detects a defective 6th harmonic component whose difference is less than the set value. Emit a discrimination signal. 21
Reference numeral 2 denotes a polar coordinate plotter which graphically plots the cross-sectional shape of the center portion of the body of the container 101 using the six values stored in the storage device 207.

Next, an inspection method in the second embodiment will be explained.

The container 101 is placed in an upright position on the rotating table 202 and rotated in one direction. At this time, the laser range finder 206 uses the center axis 2 as a zero point, indicates the direction approaching the laser range finder 206 as a positive value, and sequentially measures the radius of the center of the body of the container 101. Then, this measured value is encoded by encoder 2.
The signal is triggered every pulse of 04 and input to the storage device 207. In this way, in the storage device 207, the shape of the cross section of the center of the body of the container shown in the polar coordinate system is stored in the data order at an angle θ.

The indicated value of the laser distance meter is stored as radius R.

Therefore, by outputting these values to the polar coordinate plotter 213, a cross-sectional shape of the torso similar to that shown in FIG. 2 can be obtained.

On the other hand, in the Fourier transform calculation sheet 208, once the 1024 pieces of data have been collected, frequency component calculation is performed by regarding this data as time series data with a period of -. From this calculation result, the 6th harmonic term is extracted and sent to the output register 20.
9, and one digital comparator 211 compares it with the set value of the discrimination level setter 210, and outputs a defect discrimination signal when the sixth harmonic component is less than the set value. This activates the rejecting device and rejects the defective container from the process.

As described above, the body of the container 101 becomes approximately a regular hexagon when deformed under reduced pressure, so that in a normal container, large irregularities are alternately repeated six times per rotation. On the other hand,
A defective container with a leakage point will be almost circular in shape and have extremely small irregularities. Therefore, the presence or absence of a leakage point in the container can be determined based on the amount of the sixth harmonic. Table 2 (
a) and (b) show the uneven state of the body of a normal container and a defective container. The measurement points in Table 2 are the measurement points on the side surface of the body of the container, which are taken at six equal intervals in a certain direction with one point as a reference.

Table 2 (a) Amount of unevenness of a normal container (b) Amount of unevenness of a defective container As can be seen from Table 2 (a), Φ), each unevenness is expressed by the difference ΔR from the average radius, and the unevenness of a normal container is When comparing the container and the defective container, there is a difference of about 4 times between the two, so it is possible to clearly distinguish between a normal container and a defective container. Incidentally, even in defective containers, irregularities of about 0.4 degrees occur because folds are formed to facilitate deformation into a predetermined shape.

Furthermore, each term other than the sixth harmonic of the Fourier transform calculation result has its own unique meaning, and it is possible to use this as a discrimination index. That is, for example, the zero-order term corresponds to the average value of all data and represents the torso cross-sectional area,
This makes it possible to perform the same determination as in the first embodiment. Furthermore, the first to fifth order terms indicate that unexpected deformation has occurred in the torso. In this case, the container often deforms into a triangle or square shape, but this occurs due to poor crease processing or when some abnormal external force is applied during the process, and the container is determined to be defective. be done.

In the description of the above embodiments, a container that deforms into a regular hexagon is described, but the present invention is not limited to this, and it is of course possible to perform a leakage test on a container that deforms into any arbitrary shape such as a quadrangle or a pentagon. In these cases, in the second embodiment, the main discrimination index is the fourth-order term or the fifth-order term.

Furthermore, the above-mentioned calculations can also be performed by converting the orthogonal coordinate system in the first embodiment into a polar coordinate system. Further, although the Fourier transform is performed by digital calculation, exactly the same result can be obtained by converting the data in the storage device into analog data and performing frequency analysis using a frequency filter.

As described above, according to the present invention, it is possible to quickly and reliably perform leakage inspection due to pinholes or seal failures in containers of any shape having a flexible outer wall made of paper as a base material, quickly and reliably by automatic means. I can do it. In addition, it is possible to detect abnormal deformation of containers in addition to leakage inspection.
It can be used for a wide range of inspections of this type of container.

[Brief explanation of drawings]

FIG. 1 is a perspective view of the first embodiment of the present invention, FIG. The figure shows a perspective view of a second embodiment of the invention. 101... Container 102... Moving means 103a,
103b... Laser distance meter 105... Arithmetic device 1
10... Comparison device 202... Rotating means 205...
・Arithmetic device 206...Laser distance meter 211...Comparison device Applicant Akira Kishimoto Fig. 1 102 Fig. 2 (0) (b) Fig. 3 206 , Z') ,, F 202 12 04 ''= -203 207゜人205 10 11 Procedural Amendment (December 1982-1' (Day 1, Patent Application for Indication of Case 1982-134487 No. 3, Relationship between the person making the amendment and the case Patent Applicant Office 4439% Kamaridani-cho, Kanazawa-ku, Yokohama-shi, Kanagawa Prefecture - 26th name Name: Kishimoto Sho 4, Agent Address: 107 Telephone: 586-9287 6
, Specification subject to amendment and Drawing 7, Contents of amendment Contents of amendment (1) Page 14, line 2 of the specification “Fourier transform calculation statement 2
08'' is assumed to be the ``Fourier transform calculator 208''. (2) Insert the following sentence between the second and third lines of page 17 of the specification. ``The actual data explained above is shown in the following diagrams. That is, Fig. 4a shows the developed data of the body circumference of the container in the unfilled state and the spectral pattern, and Fig. 4b and 4b show the spectral pattern. Figure 4C shows the trunk development data diagram and spectrum pattern of the normal container and the defective container in the beverage filling state. Figures 5a and 5b show the four spectral curves of the normal container in the beverage filling state.
Examples and spectra of defective containers (8 examples of turns are shown. Figure 6 shows seven examples of container deformations and spectral patterns." Fig. 4a shows the cause and spectrum pattern, Figs. 4b and 4c show the development data of the body circumference and spectral pattern of the normal container and the defective container in the beverage filling state, and Fig. 5a shows the figure. and Fig. 5b shows the spectral patterns of normal and defective containers in the beverage-filled state, and Fig. 6 shows the deformed shapes and spectral patterns of the containers. (4) Fig. 4a, Fig. 4b, and Fig. 4C. , Figure 5a, Figure 5b, and Figure 6 are added.

Claims (2)

[Claims] (1) A container with a flexible wall is hot filled with contents such as a beverage and sealed, and then the container is cooled to shrink the contents and deform the container wall. The external shape along the outer periphery of the wall is measured using a measuring device such as a laser distance meter, and this measurement result is calculated as the cross-sectional area of the container or the amount of unevenness at a predetermined number of uneven portions on the container wall, and then set in advance. A leakage inspection method for sealed containers that determines the presence or absence of leakage points in the container by comparing with a certain value. (2) In an apparatus for inspecting leaks in sealed containers with flexible walls made of paper or the like, the container is hot-filled with beverages or the like and then cooled, and the container is moved or rotated at a predetermined speed. a distance meter that measures the outer shape of the container placed on the moving or rotating means as a distance from a predetermined position; and a distance meter that measures the distance from a predetermined position. Alternatively, a calculation device that calculates the amount of unevenness in the uneven portion of the container wall surface for a predetermined number of times;
and a comparison device that compares the value from the arithmetic device with a preset value to determine the presence or absence of a leakage point in the container.