JPH03150440A - Inspection method for hermetically sealed container - Google Patents

Abstract

PURPOSE:To easily detect a pinhole by slanting the container which contains a conductive material and has its opening part hermetically sealed with a lid, rotating the container while bringing its contents into contact with the sealed part, and applying a high frequency between the earth electrode of the container and the slide electrode of the sealed part. CONSTITUTION:The conductive contents 5 are charged in the plastic container 2, which is covered with a top film j4 to form the sealed part 6. While the container 2 is slanted to bring the contents 5 into contact with the sealed part 6, a container rotating means 22 is rotated by a motor 21 to bring the entire sealed part 6 into contact with the slide electrode 31 in order. High frequency electric power 11 generated by a high frequency voltage generating device 10 is applied between an earth electrode 20 fitted to the bottom part of the container 2 and the slide electrode 31 is applied through a resistance 12 for protection and an ammeter 13. The ammeter 13 is read to detect whether or not there is a pinhole. Consequently, the pinhole is easily and securely detected. The method is suitable for the inspection of a food container as to fruit juice, etc.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention is for inspecting sealing defects (pinholes, etc.) in the sealed portion of containers filled with conductive contents and sealed with a lid material such as a plastic film. This method can be particularly used to inspect sealed containers filled with liquid and conductive foods such as desserts and fruit juice drinks.

[Background technology]

BACKGROUND ART Conventionally, molded plastic containers that are filled with contents and sealed and packaged with a lid material such as a plastic film have been used in various fields. In particular, it can provide the physical properties required for preserving the contents, such as water vapor and gas barrier properties, and is economical and suitable for mass production.
Widely used as containers for foods such as desserts and fruit juice drinks.

If pinholes exist in such plastic containers, problems such as microbial contamination of the contents and leakage of liquid and other contents may occur, so pinhole inspections have traditionally been carried out to check for the presence of pinholes. . In particular, since pinholes often occur in the sealing area between the lid and the container, pinhole inspection in the sealing area is an important quality control item.

As a conventional technique for performing this pinhole inspection, there is a method of testing sealed packaging (Japanese Patent Publication No. 1983-6998).

This method applies a high-frequency voltage to the food hermetically packaged with an insulating packaging film, detects flash current caused by the difference in capacitive reactance between the electrode and the food, and inspects for pinholes. This is the so-called high-frequency spark method.

In addition, as a device applying this high-frequency spark method to pinhole inspection in sealed containers filled with contents, we have developed a device for detecting pinholes in sealed foods (Japanese Patent Laid-Open No. 62-707
Publication No. 25). As shown in FIG. 6, in this detection device, after a food 62 is inserted into an insulating container 61, a sealed food 65 is formed by sealing a container opening 63 with an insulating film 64. shaped electrode 66
and the ground electrode 67 is brought into contact with the bottom of the container 61, and a high frequency voltage is applied between the picture electrodes 66 and 67 by a high frequency voltage source 68, so that if there is a pinhole, a flashover will occur there. The pinhole is detected by detecting the current change due to this flash fault with a high frequency current detector 69.

[Problem to be solved by the invention]

However, in either method or device, if the food is not completely adhered to the packaging material or the container 61 is filled and the food is not adhered to the container 61 and the film 64, as shown in FIG. An air layer 71 is formed. Since this gas layer portion 71 becomes an insulating layer,
Even if there are pinholes in the film 64, there is a problem in that no flashover occurs and pinhole inspection cannot be performed.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for inspecting a sealed container that can reliably inspect for poor sealing even if the container includes an air layer inside.

[Means for Solving the Problems] A method for inspecting a sealed container of the present invention is a method for inspecting a container filled with a conductive content and having an opening sealed with a lid, the container being tilted to conduct conductivity. A high frequency voltage is applied between this sealing part and the part of the container that the conductive contents contact, and the change in the current value and/or voltage value at that time causes the conductive contents to contact the lid material. The present invention is characterized in that the sealing portion is inspected for sealing defects such as pinholes.

In addition, it is preferable to perform the inspection while rotating the container about a rotating shaft perpendicular to the bottom surface of the container.

Here, as the lid material and the container, an insulating member such as plastic or paper can be used.

Further, it is preferable that a brush-like electrode be brought into contact with the sealing portion to apply a high frequency voltage, and that a sealing defect such as a pinhole is detected by this electrode.

Furthermore, it is preferable that a ground electrode with a large contact area is brought into contact with the bottom or side surface of the container that is in contact with the conductive contents, and a high frequency voltage is applied by this ground electrode.

Further, as the conductive content, a liquid material having conductivity can be used.

[Effect]

In the present invention, the sealed container is tilted to bring the conductive contents into contact with the sealing portion between the lid and the container, and there is a gap between the sealed portion and the portion of the container where the conductive contents contact. Apply high frequency voltage. Here, if a sealing defect such as a pinhole exists in the sealed portion to which voltage is applied, an electric circuit is formed between the sealed portion and the container via the pinhole and the conductive contents. At this time, since the conductive contents are in contact with the sealed part, the electrical circuit is not insulated by the air layer, and changes in current or voltage are measured and pinholes are reliably detected. .

That is, even if there is an air layer inside the container, the present invention eliminates the air layer from between the sealed portion to which a high frequency voltage is applied and the conductive contents by tilting the container. Since there is no insulating layer, the electrical circuit is interrupted only by the presence or absence of the pinhole, and the pinhole is reliably detected, thereby achieving the above objective.

〔Example〕

Hereinafter, one embodiment of the present invention will be described based on the drawings.

FIG. 1 shows an inspection system 1 for pinhole inspection of plastic containers according to the present invention.

The inspection system 1 is a plastic container 2 to be inspected.
Pinhole inspection is performed by applying a high-frequency voltage to the pinhole. The plastic container 2 is made of an insulating plastic, such as polypropylene, and is formed into a cylindrical shape having dimensions as shown in FIG. 2, for example.

A flange 3 is formed at the opening of the plastic container 2, and a top film 4 laminated with an insulating plastic film such as nylon (NY) and cast polypropylene (CPP) is heat-sealed onto the flange 3. It is attached with etc. Therefore, container 2
The inside is filled with a liquid conductive content 5 and sealed with a top film 4, and this film 4 and the container 2
A sealing portion 6 is constituted by the flange 3 portion to which the flange 3 and the flange 3 are bonded.

Note that this plastic container 2 is not filled with the contents 5, and an air layer 7 of air or the like is formed in a part thereof, and at the time of inspection, it is tilted approximately vertically so that the air layer 7 is raised upward. It is said to be in a state where it is located.

On the other hand, the inspection system 1 includes a high frequency voltage generation and detection device 10, as shown in FIG. This generation/detection device 1O includes a high frequency voltage generation source 11, a safety resistor 12, and a high frequency current detector 13.

A ground electrode 20 to which a high frequency voltage is applied by a high frequency voltage generation source 11 and a detection section 30 are connected to this generation detection device 10 .

The ground electrode 20 is made of a conductive metal, preferably a zinc-copper-tin alloy or copper, and is formed to have the same shape as the bottom of the plastic container 2, and is fitted into the container 2.
It is possible to rotate the container by means of a container rotation means 22 having a container rotating means 22 having a diameter of 1.

Therefore, as the ground electrode 20 rotates, the plastic container 2 is rotated about a substantially horizontal rotation axis perpendicular to the bottom surface.

On the other hand, the detection unit 30 includes a brush-like electrode 31 made of a conductive metal, preferably copper, and having a wire diameter of 0.5 mm or less.
As shown in FIG.
has been contacted. Therefore, as the container 2 rotates, the sealing part 6 that the detection part 30 contacts moves sequentially, and the entire circumference of the sealing part 6 is inspected.

In this embodiment configured as described above, the pinhole inspection of the plastic container 2 is performed in the following procedure.

First, the container 2 is tilted in a substantially orthogonal direction, the ground electrode 20 is fitted to the bottom of the container 2, and the detection part 30 is brought into contact with the sealed part 6 that the conductive contents 5 are in contact with.

Next, a high frequency voltage is applied between the ground electrode 20 and the detection section 30 by the high frequency voltage generation source 11 of the high frequency voltage generation and detection device IO, and the container 2 is rotated once via the ground electrode 20 by the container rotating means 22.

Here, if the sealing part 6 that the detection part 30 is in contact with is completely sealed, the container 2 and the top film 4
Since it is made of insulating plastic, the detection part 30 and the conductive content 5 are not electrically connected and no electric circuit is formed, so the high frequency current detector 13 does not detect current.

On the other hand, when the detection part 30 comes into contact with the sealing part 6 having a sealing defect such as a pinhole as the container 2 rotates, the detection part 30 and the conductive contents 5 are electrically connected due to the pinhole or the like. Since they are connected to form an electric circuit, current is detected by the current detector 13.

Therefore, a sealing defect such as a pinhole in the sealing portion 6 is detected based on the presence or absence of a detection current in the current detector 13.

According to this embodiment, the following effects can be obtained.

0 In other words, even if the plastic container 2 has an air layer 7, the conductive contents 5 can be brought into contact with the sealing part 6 by tilting the container 2, and therefore a pinhole can be formed in the sealing part 6. , an insulating layer due to the gas layer 7 is not formed between the detection unit 30 and the conductive content 5, so an electric circuit is formed and the current due to the pinhole can be reliably detected.

In other words, according to this embodiment, even if there is a pinhole, there is no inconvenience that an electric circuit is not formed by the insulating layer of the air layer 7, and the detected current in the current detector 13 is affected only by the presence or absence of the pinhole. Therefore, pinholes can be detected reliably.

Further, since the container 2 is rotated by the container rotation means 22, the entire circumference of the sealed portion 6 can be inspected with the detection section 30 fixed, and the inspection work can be performed easily and in a short time.

Note that the present invention is not limited to the configurations of the above-mentioned embodiments, and the present invention includes modifications within a range that can achieve the object of the present invention.

For example, in the above embodiment, the container 2 was inspected by tilting it approximately vertically. For example, as shown in FIG. 4, by tilting the top film 4 side diagonally downward, all the sealed parts The inspection may be performed with the conductive contents 5 being in contact with the conductive contents 5. In this case, all sealed parts 6 or contents 5
Since the container 2 is in contact with the container 2, the detection section 30 can be moved and inspected without rotating the container 2.

In short, in the present invention, if the container 2 is tilted so that the conductive contents 5 are in contact with at least a portion of the sealed portion 6, and the detection portion 30 is brought into contact with the sealed portion 6 that is in contact with the contents 5, The inclination angle may be appropriately set in practice.

Further, as the container rotation means 22 for rotating the container 2,
The method is not limited to rotating the earth electrode 20 fitted to the bottom of the container 2 as in the above embodiment, but for example, the earth electrode 20 may be formed into a plate shape, and the container 2 may be connected to the earth electrode 20 from the top film 4 side. A holding jig or the like that presses and rotates may be used, and the configuration 2 is arbitrary.

Furthermore, the container 2 to be inspected is not limited to the one in the above embodiment, but for example, as shown in FIG. It can also be used for 50 tests. In particular, with this cover-like container 50, pinhole inspection is difficult because it is difficult to contact the electrode 66 with the bent sealing part 6 using the conventional method of contacting the electrode 66 from above the film 4. However, in the present invention, the detection part 3 is inserted into the sealing part 6 from the side of the container 50.
0 can be brought into contact with the electrode 31, as shown in FIG. 5, the brush shape of the electrode 31 can be appropriately selected to match the bending direction, and pinhole inspection can therefore be performed reliably.

Furthermore, in the embodiment described above, pinholes were detected by changes in the current detected by the high-frequency current detector 13, but they may also be detected by measuring voltage and detecting the changes, or by detecting both current and voltage. It may be detected by measurement, and these may be set appropriately in implementation.

3 Furthermore, in the above embodiment, a plastic container 2 and a film 4 as a lid material were used, but the container and lid material of the present invention are not limited to plastic, but may also be paper or the like, and in short, they are insulating. You can use it if you have it.

Further, the conductive content 5 is not limited to a liquid, and may be a mixture of a liquid and a solid.In short, the conductive content 5 may be any content 5 that can come into contact with the sealing portion 6 when the container 2 is tilted. Furthermore, this content 5 is not limited to foods, but can also be applied to other conductive substances.

Next, experimental results using the inspection system 1 of the present invention will be explained.

In this experiment, a polypropylene container 2 having the dimensions and shape shown in FIG. 2 and a thickness of 0.8 mm was used as the container to be inspected. The capacity of this container 2 is 65c
c, and 55 cc of 2% saline as the conductive content 5
In other words, 85% filling was performed.

The top film 4 used was a film in which nylon was laminated to a thickness of 15 μm and cast polypropylene was laminated to a thickness of 60 μm.

Further, as the high frequency voltage generation and detection device IO, a Nirakami sensor (Kiki H8E model (name: desktop pinhole instrument)) was used.
It can be varied to V, and the presence or absence of current detection is indicated by a lamp.

Table 1 shows the experimental results when a high frequency voltage of 3 KV was applied using such a container 2 in the method of the present invention shown in FIG. 1 and the conventional method shown in FIG.

As can be seen from Table 1, the method of the present invention was able to detect holes of 15μ and 50μ that could not be detected using conventional methods.

Therefore, it can be seen that the inspection by the sealed container inspection method of the present invention is effective.

〔Effect of the invention〕

According to the present invention, even if the container is a sealed container that includes an air layer inside, it is possible to reliably test for a seal failure.

[Brief explanation of the drawing]

FIG. 1 is a schematic side view showing an embodiment of the present invention, FIG. 2 is a cross-sectional view showing a plastic container, FIG. 3 is a schematic front view of the embodiment, and FIGS. 4 and 5 are each a diagram showing the invention. FIG. 6 is a schematic diagram showing a modification of the conventional example. 1... Inspection system, 2... Plastic container, 3
... flange, 4 ... top film, 5 ... conductive content, 6 ... sealing part, 7 ... air layer part, 10.
...High frequency voltage generation and detection device, 20... Earth electrode,
22... Container rotation means, 30... Detection unit, 31...
·electrode.

Claims (2)

[Claims] (1) A method for inspecting a container filled with conductive contents and having an opening sealed with a lid, the container being tilted so that the conductive contents come into contact with the lid and the sealed portion of the container. , applying a high frequency voltage between the sealing part and the part where the conductive contents of the container come into contact, and inspecting the sealing failure of the sealing part by the change in the current value and/or voltage value at that time. Features a sealed container inspection method. (2) A method for inspecting a sealed container according to claim 1, characterized in that the inspection is carried out while rotating the container around an axis perpendicular to its bottom surface.