JPS60127438A - Method and apparatus for leakage inspection of sealed container - Google Patents

Abstract

PURPOSE:To perform the leak inspection of an individual container, which is accommodated in a carton case and the like, intactly, by measuring the displacement of the lid of the container by a non-contact type displacement gage. CONSTITUTION:In a carton case 310, containers 301-1-301-n filled with beverage are accommodated. The case 310 is provided in a vacuum tank 303. Non-contact type, eddy-current displacement gages 305-1-305-n are provided in correspondence with lid surfaces 302-1-302-n of the containers. The displacement of the lid surface of each container, when the pressure in the vacuum tank 303 is reduced, is measured. Based on the magnitude of the rate of change in said displacement, the leakage of the container is inspected. Thus the leak inspection of the individual container, which is accommodated in the carton case and the like can be carried out intactly.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention provides fruit juice in a container made of a composite material such as paper, plastic, aluminum foil, etc. laminated.

Pinholes or poor sealing in sealed containers filled with food or drinks such as coffee and heat-sealed with a lid made of aluminum foil or a flexible material laminated with aluminum foil and plastic film at the mouth. The present invention relates to a method and apparatus for inspecting leakage based on the present invention. In particular, it relates to a method and an apparatus for inspecting a container in its initial state, such as a carton case, for leakage caused by minute pinholes or defective seals, which can be detected after several days or weeks have elapsed. .

[Prior art]

Sealed containers made of composite materials laminated with paper, plastic, aluminum foil, etc. have become widely used in recent years.
Inspection for leaks due to pinholes or poor seals can be performed by detecting the amount of immersion deformation of the body immediately after filling and sealing the container, if the pinholes are large and the leakage is large. This has already been disclosed by the applicant.

However, some leaks include minute pinholes and the like, and can be detected several days to several weeks after the container is filled with food or drink and sealed. In such cases, containers filled with food and beverages, etc. are often stored in carton cases, so in order to efficiently test for leakage, leave the containers stored in the carton case and This must be done without opening the carton case lid.

Therefore, an inspection method that utilizes the deformation of the lid due to leakage is usually considered.

Conventionally, leakage tests that occur due to pinholes in metal cans or glass bottles (containers with lids made of tin or aluminum plates with a thickness of about 1,2+ml to 3 sails) have been carried out by mechanical impact on the lid surface. The most common method is the percussion method, which takes advantage of the correlation between the free vibrations generated by this and the internal pressure of the container. The lid has almost no elasticity and does not vibrate freely even when subjected to impact.
It was impossible to apply the percussion method.

In fact, as a separate conventional leakage testing method, there is one that gradually deforms an elastic or flexible lid surface in response to the internal pressure of the container, and uses this curved deformation of the lid surface to test for leaks. . However, for containers with flexible bodies made of laminated materials such as paper and plastic, if the lid surface sinks in when the pressure inside the container begins to decrease, the body easily deforms after that, making it difficult to expand the interior of the container. Unable to reduce pressure.

Therefore, the difference between the internal and external pressures of the container was extremely small, and there was no detectable difference in the degree of curvature of the lid surface depending on the presence or absence of leakage, making inspection impossible.

[Purpose of the invention]

The present invention is a sealed container whose body is made of a composite material laminated with paper, plastic, aluminum foil, etc., and whose lid is made of a flexible material based on aluminum foil. This is to check for leaks.
In particular, to provide a method and device for leakage testing of sealed containers that are pressurized so that leakage testing of individual containers stored in a single carton case can be reliably performed while the carton case remains closed during shipping. With the goal.

[Structure of the invention]

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

Usually, beverages are filled into containers at a high temperature of about 90° C. to 95° C., sealed, and then cooled to room temperature. Therefore, due to the difference in coefficient of thermal expansion between the beverage and the container, the inside of the container is under reduced pressure. In this case, if you apply crushing force to the body wall of the container with your hands or fingers, the pressure inside the container will increase, but if the container is defective and has pinholes, air will be sucked into the container. Because the pressure difference between the inside and outside of the container is close to zero, the pressure inside the container becomes higher than the atmospheric pressure outside the container even with a very small amount of crushing. Therefore, the lid surface of the container can be protruded by applying only a slight force. On the other hand, since a normal container without pinholes etc. maintains a reduced pressure state, the lid surface cannot be made to protrude unless the body wall surface of the container is crushed with a large force.

The protrusion of the lid surface, that is, the change of the lid surface from a concave shape to a convex shape, occurs instantaneously, and the reverse change from a convex shape to a concave shape also occurs instantaneously. This phenomenon is called a flip. The crushing force on the wall of the body of the container when the lid is flipped is extremely small. Therefore, if you apply external X pressure to the container and detect that the lid has flipped,
It can be seen that the applied pressure at that time and the pressure inside the container are approximately equal.

The above facts will be explained based on experimental data. Note that FIG. 1 is a partial sectional view of this experimental apparatus, and FIG. 2 is experimental data.

Container 1011d to be tested, 50μ polyethylene on the outside of the base paper with a thickness of 3, 30μ polyethylene and 15μ aluminum foil on the inside, and 5μ thick polyethylene on the inside, and 5μ thick polyethylene on the inside.
Width: 171, laminated with 0μ polyethylene adhesive.
m, a rectangular sheet material with a height of 130 mm and a diameter of 53 mm.
The body is rolled into an approximately cylindrical shape of mm and is heat-bonded, and the thickness is 1 mm.
The lid is press-molded into a circular dish shape from a sheet made of 00μ aluminum foil, laminated with 50μ polyethylene on the inside, and coated with 5μ epoxy phenol paint on the outside. It is formed by thermally bonding 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. be.

In the experimental apparatus, an eddy current displacement meter 103 is placed opposite the upper lid surface 102 of the container 101, and the container 10 and the eddy current displacement meter 103 are housed inside a Pelger vacuum chamber 104. Ru. This vacuum chamber 104 is equipped with a pressure gauge 105 to measure the degree of vacuum inside, and a vacuum pump (not shown) is connected to an exhaust port 106. Still, the output signals of the eddy current displacement gauge 103 and the pressure gauge 105 are sent to the Y-axis and X-axis of the X-Y recorder 109 via dedicated amplifiers 107 and 108, respectively.

In this experimental equipment, the vacuum pump is operated and the exhaust port 1 is
The data shown in FIG. 2 is obtained by recording the output signals of the eddy current type displacement meter 103 and the pressure gauge 105 on the X-Y recorder 109 while gradually suctioning from 06 onwards.

In other words, the horizontal ■ axis of the graph in FIG.
05, and the vertical ω axis represents the relative value of the vertical displacement of the lid surface 102 measured by the displacement meter 103. And curve (a) is a normal container,
Curves (b) to (e) are measurement examples of various defective containers with leakage due to pinholes, etc., and the origin of each curve was moved in the Y-axis direction to prevent them from overlapping.

As can be understood from this data, in the case of a normal container, there are no voids inside the container, or even if there are, there are very few voids, so even if the pressure inside the vacuum chamber 104 is significantly reduced, the lid surface 102 will not flip. Does not occur. On the other hand, in the case of defective containers, the vacuum chamber 1
As the pressure inside the container 101 decreases, the internal pressure of the container 101 becomes relatively high, and at that moment the lid surface 102 flips.

This phenomenon should also occur in the body of the container 103, but since the lead surface is much more flexible than the body, in reality, almost no deformation occurs in the body. It can be seen that the objectives of the invention can be fully achieved based on the principles of the invention.

Therefore, the present invention stores a container having a flexible lid surface filled with contents such as a beverage inside a chamber, reduces or increases the pressure in the chamber to a predetermined pressure, and changes the displacement of the container lid surface during this time. is measured by a non-contact displacement meter installed in the chamber corresponding to the container lid surface, and the rate of change in displacement is calculated by a calculation device. A method for inspecting leakage of sealed containers characterized by determining the container as a defective container, and an apparatus for inspecting leakage of sealed containers having a flexible lid surface made of aluminum foil or the like as a base material, A chamber that stores a container that has been hot-filled with contents such as, and then cooled; a pump that reduces or increases the pressure in this chamber to a predetermined pressure; There is a non-contact displacement meter that measures the displacement of the lid surface during depressurization or pressurization, a calculation device that calculates the rate of change in lid surface displacement by calculating the signal from the displacement meter, and an output from the calculation device that detects defects. The present invention comprises a leakage inspection device for whistle-sealed containers, characterized in that it is equipped with a defective container discriminating device for discriminating containers.

[lol example]

An embodiment of the present invention will be described based on FIG.

301-+, 301-2, . . . , 301-n are containers arranged and housed in a carton case 310, and are filled with food and drinks. Generally, for containers with a diameter of about 50 mm, one case is often made up of a total of 30 containers in 5 rows and 6 columns, but various cases such as 4 rows and 5 columns or 5 rows and 5 columns are possible. 303 is a vacuum tank serving as a chamber;
In order to take the carton case 310 in and out of the predetermined position of 4, an opening and closing operation is performed by an opening and closing device (not shown). 30
5-+, 305-2, . ..., 301-n
Lid surface 302-s, 302-2, ・-, 302
−n, and each lid surface 302
-t, 302-2,...

A voltage is generated proportional to the distance to 302-n.

The vacuum chamber 303 has a gasket 306 attached to its mouth that contacts the rotating section 304, and is provided with an exhaust port 307 at an appropriate location. The exhaust port 307 is connected to a vacuum pump (not shown) via a solenoid valve 308 to adjust the pressure inside the vacuum chamber 303. The solenoid valve 308 is opened by the solenoid valve control circuit 326 in synchronization with the closing of the vacuum chamber 303 . A pressure gauge 309 measures the pressure inside the vacuum chamber 303 and generates a voltage proportional to a change in pressure.

320 is a high speed switch, and each displacement meter 305-1.

305-2,..., 305-n and pressure gauge 308
The output voltage signals of are sequentially switched and sent to the analog-to-digital converter 321. 322 converts each signal digitized by the analog-to-digital converter 321 into each channel Ml.
, M2, . . . , Mn, Mp.

For each channel Ms, M2,..., Mn,
A signal as shown in FIG. 2 is stored. In this case, the number of channels is 30 containers plus one for the pressure gauge,
31 channel. Reference numeral 323 denotes an arithmetic unit that performs differential calculations, which calculates second-order differentials of the signals in channels Ml, M2, . ,
Lid surface 302-+ of 301-n, 302-2, ・
=, 302-n checks for the presence of 7 lips.

Reference numeral 324 denotes a negative pulse detection circuit which is a defective container discriminating device that discriminates whether a container is defective based on the output of the arithmetic device 323, and outputs a defective discrimination signal 324a when a negative pulse is output from the arithmetic device 323. .

325 is the defect determination signal 3 from the negative pulse detection circuit 324
24a is stored in the vacuum chamber 30 after the inspection is completed.
3 opens, a signal is sent to a defective container discharge device (not shown) to activate it. The solenoid valve control circuit 326 controls the solenoid valve 30 by a signal 324a from the negative pulse detection circuit 324.
8 is closed to introduce outside air into the vacuum chamber 303, stopping the degree of vacuum from increasing any further, and preventing contamination of surrounding containers due to leakage of contents from the defective container. Further, the solenoid valve control circuit 326 also controls the solenoid valve 3 based on the signal from the comparator 327.
08 is closed and outside air is introduced into the vacuum chamber 303. This means that if all the containers are normal, even if the internal pressure of the vacuum chamber 303 reaches 1303Hg or more, the failure determination signal 32
4a, so when the internal pressure of the vacuum chamber 303 reaches the pressure preset in the setting device 328, a signal is sent to the solenoid valve control circuit 326 to end the inspection.

Next, an inspection method using the above device will be explained.

Container 301-1.301-2 filled with food and drink and sealed
.

..., carton case 3 containing a large number of 301-n.
10 is placed at a predetermined position on the floor 304. Next, the vacuum chamber 303 is closed and each container 301-1, 301-2, -.
, 301-n c7) Lid surface 302-1.302-2
, Kawa, 302-n, the corresponding eddy current type displacement meter 305
-1, 305-2, -, and 305-n are opposed to each other. At the same time, the electromagnetic valve control circuit 326 opens the electromagnetic valve 308 to suck the inside of the vacuum chamber 303 through the exhaust port 307 . This pressure change inside the vacuum chamber 303 and the lid surfaces 302-s, 302-2, ..., 302- of each container
The displacement of n is measured using the pressure gauge 309 and each eddy current displacement gauge 305-s.
.

305-2, . . . , 305-ntlc, each of which is measured as a voltage signal. Then, each of these voltage signals is sequentially sent to an analog-to-digital converter 321 by a high-speed switch 320, where it is converted into a digital signal, and then converted into a digital signal for each channel MJ + M2r of the memory 322.
....

It is stored in Mn and Mp.

Each channel Ml, M2. . . , Mn is subjected to second-order differential calculation using the signal in the channel Mn in the calculation unit 323, and the signals stored in the channels 301-r and 301-r are
, 301-21..., lid surface 302-1 of 301-n
．． 302-2,...

Check whether there is a 3of-n flip. That is, the result of the second-order differential in the calculation device 323 causes the output of the calculation device 323 to suddenly change from a positive value to a negative value at the pressure that caused the lid surface to flip. FIG. 4 shows this state. Curve (1) in FIG.
There is a pinhole etc. at 1-x, indicating that the lid surface 302-x has been flipped. Curve C11) is a derivative of it and represents the slope of curve (().Curve (i
ii) is further differentiated, and is obtained by performing second-order differentiation on the curve (DIfC), and shows that at the pressure that causes the lid surface 302-x to flip, the output of the arithmetic unit 323 suddenly changes from a positive value to a negative value. It also shows that the output is almost zero at other pressures.

As described above, when the arithmetic unit 323 outputs a negative pulse, the negative pulse detection circuit 324 outputs the defect determination signal 32.
4a is output to the memory 325 and the solenoid valve control circuit 326. This causes the solenoid valve control circuit 326 to control the solenoid valve 308.
At the same time, when the vacuum chamber 303 is opened, the memory 3
A defective container discharging device (not shown) is activated by a signal from 25, and the carton case 310 containing the defective container is discharged to a predetermined location. Although not shown, a display device is provided to indicate which containers are defective, so that only defective containers can be taken out from the discharged carton case 310.

On the other hand, when there is no defective container in the carton case 310, when the pressure gauge 309 reaches the same pressure as the pressure set in the setting device 328, a signal is sent from the comparator 327 to the solenoid valve control circuit 326. The solenoid valve 308 is opened to automatically terminate the inspection. After the vacuum chamber 303 is opened, the carton case 31 is opened by a delivery device (not shown).
Send 0 to the next process.

In order to accurately perform the inspection of the present invention, the carton case 31
The pressure inside the vacuum chamber 303 must match the pressure inside the vacuum chamber 303. However, in a general carton case,
Since the corner seams were not entirely glued, there was sufficient air permeability in these areas, and there were no problems at relatively slow pumping speeds of 5 cm Hg/see or less. In addition, when exhausting at a speed of 8 cm Hg/w or more, it is necessary to provide an exhaust hole 311 in the carton case, but this exhaust hole 311 can be sufficiently used as a handle hole for transportation normally provided in the carton case. .

In order to carry out the differential operation of the present invention, it is sufficient that the analog-to-digital converter 321 and the memory 322 each have 8 bits. This is because the accuracy of displacement measurement is not so important in the present invention, and the method is based on the presence or absence of a flip that changes rapidly, and since the flip accounts for most of the amount of vertical displacement of the lid surface, it is not practical. There is no problem if it is 4 bits or more. In addition, the measurement resolution of the degree of vacuum is 23H.
If the maximum degree of vacuum is 40σHg, the required precision is 5 inches, and 5 bits or more is sufficient.

The second-order differential calculation was approximated by the second-order difference of the lid surface displacement values stored for each channel. In other words, the lid surface displacement value is sampled and stored at approximately equal intervals for every degree of vacuum 2 cInHg, and the value itself as a result of the differential operation has no significant meaning, and a negative value is generated in the second-order differential. This is because it is determined by

In addition, according to the present invention, it is possible not only to inspect containers for leakage, but also to detect gas generation and expansion due to deterioration of the contents. That is, a pressure pump is used instead of a vacuum pump to pressurize the inside of the chamber to immerse the lid surface of the container containing spoiled contents, and the displacement of the lid surface at this time is calculated by second-order differential calculation using a calculation device. Defectiveness can be determined by making the output signal a positive pulse. Furthermore, defectiveness can also be determined by replacing the vacuum pump with a pressure regulator, increasing the pressure in the chamber to a maximum value at first, and then gradually reducing the pressure. However, in this case, it is necessary to add memory outside the pressurized area.

〔Effect of the invention〕

As described above, according to the present invention, the displacement of the container lid surface is measured using a non-contact type displacement meter, and the leakage of the container is inspected based on the magnitude of the change rate of the displacement. The container can be inspected as it is. Therefore, when shipping products, etc., it is necessary to open the cart/case and remove the containers one by one to prevent leakage due to minute pinholes, etc., which cannot be detected until several days or weeks after filling the beverage. This makes it possible to easily perform inspections without any trouble.

[Brief explanation of the drawing]

FIG. 1 is a diagram explaining the principle of the present invention, FIG. 2 is a data diagram of an experiment based on FIG. FIG. 301-1.301-2. ..., 301-rl...
- Containers 302-1, 302-2. -..., 302-n
- Lid surface 303... vacuum chamber (chamber) 305-1, 305-2. ..., 305-11...
・Non-contact eddy current displacement meter

Claims (2)

[Claims] (1) A container with a flexible lid surface filled with contents such as a beverage is stored inside a chamber, the pressure inside the chamber is reduced or increased to a predetermined pressure, and the displacement of the container lid surface during this time is measured. A non-contact displacement meter installed in the chamber corresponds to the lid surface, and the rate of change in displacement is calculated by a calculation device. If the calculation results show that the rate of change in displacement of the lid surface is large, the container is determined to be defective. A leakage inspection method for a sealed container characterized by distinguishing it from a container. (2) In an apparatus for inspecting leakage of a sealed container having a flexible lid surface made of aluminum foil or the like as a base material, a chamber for storing a container that is hot-filled with contents such as a beverage and then cooled; A pump that reduces or increases the pressure in the chamber to a predetermined pressure, and a non-contact displacement meter that is placed inside the chamber and corresponds to the lid surface of the container and measures the displacement of the lid surface applied when the pressure is reduced or increased. A seal characterized by comprising: a calculation device that calculates a rate of change in lid surface displacement by calculating a signal from a displacement meter; and a defective container discrimination device that discriminates a defective container based on the output from the calculation device. Container leakage inspection device.