JPH08240569A - Method and device for inspecting pinhole inferiority of food package sheet and food air-tight vessel - Google Patents

Abstract

PURPOSE: To efficiently and surely inspect pinhole inferiority of a food air-tight vessel made of a food package sheet of laminating structure including a conductive layer made of a metal foil. CONSTITUTION: In a pinhole inferiority inspection method of a food air-tight vessel A formed by melting a food package sheet S laminating resin layers Sb, Sc sandwiching a conductive layer Sa, a ground electrode 21 is brought into contact with the conductive layer Sa of the sheet A, voltage is applied between the ground electrode 21 and a detection electrode 23 brought into contact with or neared to the surface of the food air-tight vessel A, and presence of charge current is detected.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a food packaging sheet and a method and an apparatus for inspecting pinholes in food-sealed containers, and more particularly to a food packaging sheet having a conductive layer sandwiched between resin layers or a food packaging sheet thereof. The present invention relates to a pinhole defect inspection method and device for a food-sealed container using a sheet.

[0002]

2. Description of the Related Art Metal foil (conductive layer) such as aluminum foil as a sheet for packaging various foods such as retort foods.
There is known a food packaging sheet having a laminated structure of a resin film (resin layer) laminated with the metal foil sandwiched between them, and a highly airtight sheet formed by heat-sealing the resin layer of the food packaging sheet. Sealed food containers are known.

In such a food sealed container, a pinhole defect is inspected in order to ensure airtightness.
As a pinhole defect inspection method for food-sealed containers, a ground electrode having a large surface area is brought into contact with an electrically insulating surface of the food-sealed container to sandwich the food-sealed container, as disclosed in Japanese Patent Publication No. 50-6998. The detection electrode with a small surface area is made to face the ground electrode and brought into contact with the electrically insulating surface of the food-sealed container, a high frequency voltage is applied between the detection electrode and the ground electrode, and pinhole defects are detected by the presence or absence of discharge current. The method is known. A pinhole defect inspection device using this method is disclosed in Japanese Patent Laid-Open No. 62-70725.

This method and apparatus for inspecting pinhole defects in a food-sealed container utilizes capacitor coupling by applying a high-frequency voltage. Due to the difference in surface area between the detection electrode and the ground electrode, the ground electrode and the contents inside the container are The capacitance between the sensing electrode and the contents in the container can be ignored, and the electrical resistance due to the contents and the capacitance between the sensing electrode and the contents If there is a pinhole in the food sealed container that comes in contact with the detection electrode, the high-frequency electric voltage that causes a flashover in the discharge gap due to the capacitance section between the detection electrode and the contents The inspection principle is to apply between the electrodes and detect whether or not a discharge current flows through the voltage application circuit.

[0005]

In the above-described method for inspecting a pinhole defect in a food hermetic container, the condition that the surface area of the detection electrode is sufficiently smaller than the surface area of the ground electrode is essential due to the inspection principle. This means that if the sealed food container is made of only an electrically insulating synthetic resin material such as a tofu container, that is, a dielectric synthetic resin material, the electrode shape can satisfy the condition. However, if the food sealed container is a laminated food packaging sheet containing a conductive layer of a metal foil, such as a food sealed container for retort foods, the condition is satisfied regardless of the electrode shape. Can't meet.

Therefore, the above-described pinhole defect inspection method cannot be applied to a food sealed container having a laminated food packaging sheet containing a conductive layer made of a metal foil. The present invention has been made to solve the above-mentioned problems, and efficiently performs pinhole defect inspection of a food sealed container using a laminated food packaging sheet sandwiching a metal foil with high reliability. An object of the present invention is to provide a pinhole defect inspection method and device for a food-sealed container that can be performed and can be used for inspection of all products in a production line.

It is another object of the present invention to provide a method and an apparatus for inspecting a pinhole defect in a food packaging sheet having a laminated structure in which a metal foil is sandwiched.

[0008]

In order to achieve the above object, a method of inspecting a pinhole defect in a food packaging sheet according to the present invention comprises contacting a ground electrode with a conductive layer exposed on an end face of the sheet, and then the ground electrode. It is characterized in that the presence or absence of a discharge current is detected by applying a voltage between the sensor electrode and the detection electrode which is in contact with or brought close to the sheet surface.

In the method for inspecting a pinhole defect of a food container according to the present invention, the ground electrode is brought into contact with the conductive layer of the sheet forming the food container, and the ground electrode and the surface of the food container are brought into contact with or close to each other. A feature is that a voltage is applied between the detecting electrode and the presence or absence of a discharge current.
The contact between the ground electrode and the conductive layer can be performed at the portion where the conductive layer is exposed at the edge of the food-sealed container. In addition, if the detection electrodes are installed on both the front and back sides of the food-sealed container, it is possible to inspect for pinhole defects on both sides of the food-sealed container at the same time.

The pinhole defect inspection apparatus for food sealed containers according to the present invention comprises a ground electrode, a detection electrode, a power source and a current detector connected to both electrodes, and the ground electrode is an edge of the food sealed container. The detection electrode is placed so that it can come into contact with the end, and the detection electrode is placed so that it can come into contact with or approach the surface of the food-sealed container, and the discharge current that flows when a voltage is applied between the ground electrode and the detection electrode by a power source is detected by current It is characterized in that a pinhole defect is detected by detecting with a container.

A pinhole defect inspection apparatus for a food-sealed container according to the present invention, which is suitable for inspecting in a manufacturing process, has a conveying means for conveying the food-sealed container and an edge portion of the food-sealed container beside the conveying means. To the ground electrode, a pair of detection electrodes arranged so as to be in contact with or accessible to both sides of the food-sealed container conveyed by the conveying means, and a power supply connected to the ground electrode and the detection electrode. An electric current detector, a container detecting means for detecting that the food sealed container conveyed by the conveying means has passed a predetermined position, and an inspection timing for setting an inspection period for each container in response to a detection signal from the container detecting means A pinhole defect is detected when the current detected by the current detector exceeds a threshold value during the inspection period set by the inspection timing setting unit. To.

A brush electrode, a roller electrode, a flat plate electrode or the like can be used as the detection electrode. The detection electrode is exposed at the side end surface of the food container and is short-circuited with the conductive layer in contact with the ground electrode. should not be done. When a brush electrode is used as the detection electrode, this short circuit can be reliably prevented by adopting a structure in which the end surface of the food-sealed container is covered near the detection electrode. Also, if the pair of detection electrodes is composed of a pair of roller electrodes having a small diameter portion and a large diameter portion at both ends thereof, the large diameter portion is made electrically insulative and the heat-sealed seal portions on both side edges of the food hermetic container under inspection are provided. You can guide by sandwiching,
Since the positional relationship between the detection electrodes and the surface of the food container is stable, the reliability of the pinhole inspection can be improved.

As the power source, any power source such as a DC power source, an AC power source and a high frequency power source can be used, but practically it is convenient to use an AC power source having a frequency of several kHz and a voltage of several kV. is there. The frequency or voltage of the power supply is
There is a pinhole defect depending on the material and film thickness of the food packaging sheet used for pinhole inspection or the laminated sheet sandwiching the metal foil used in the food sealed container, or the size of the pinhole to be detected. The value is set so that the discharge current exceeding the threshold value flows only when

[0014]

In the present invention, the ground electrode is brought into contact with the conductive layer exposed on the end face of the sheet, or the conductive layer exposed on the end face of the container, so that the conductive layer itself of the food packaging sheet or the food container is substantially removed. Function as a simple ground electrode plate. If there is no pinhole between this ground electrode and the detection electrode that is in contact with or brought close to the surface of the sheet or container, the discharge current will not flow, and if the pinhole exists, the discharge current exceeding the threshold value will flow. Since the power supply voltage and the like are set, the pinhole defect can be detected from the presence or absence of the discharge current between the ground electrode and the detection electrode.

By detecting the passage of the food hermetically-sealed container to be conveyed and setting the inspection period, the sheet conductive layer exposed at the front edge part or the rear edge part of the food hermetically-sealed container becomes a detection electrode during the conveyance. It is possible to eliminate the detection signal that may flow due to the contact and to reliably detect only the detection signal due to the pinhole defect. Further, by bringing the ground electrode into contact with the conductive layer exposed at the edge of the food-sealed container to bring the ground electrode and the conductive layer into conduction,
Pinhole defect inspection can be continuously performed without stopping the food sealed container being transported by the transport means on the production line, and pinhole defect inspection can be performed without reducing the productivity of the food sealed container. it can.

[0016]

Embodiments of the present invention will be described below in detail with reference to the accompanying drawings. 1 and 2 show an embodiment of an apparatus for carrying out the pinhole defect inspection method for a food packaging sheet according to the present invention. The inspection apparatus of the present embodiment is provided in front of the sheet winding unit 1 in the laminate manufacturing line of the food packaging sheet S, and is equipped with the food packaging sheet S.
A grounding electrode 3 that is in sliding contact with both end surfaces of the food packaging sheet, a guide roller 5 that faces the food packaging sheet S and that extends across the food packaging sheet S in the width direction, and a roller-shaped detection electrode 7. There is. A high voltage power supply 9 is connected to the detection electrode 7, and an ammeter 11 for detecting the current value of a current flowing in the middle of the wiring that electrically connects the high voltage power supply 9 and the detection electrode 7 is connected.

A controller 13 is connected to the ammeter 11. The control device 13 determines whether or not the current value detected by the ammeter 11 exceeds a predetermined threshold value, and the ammeter 11
If the current value detected by exceeds the threshold value, an operation command is output to the marker 15 at a timing corresponding to the winding speed of the food packaging sheet S. Food packaging sheet S
As shown in FIG. 3, is laminated on an electrically insulating resin surface layer Sb made of a polyethylene resin film on one surface of a conductive layer Sa made of a metal foil such as an aluminum foil, and the other of the conductive layer Sa Has a three-layer laminated structure in which a polypropylene resin film is laminated on an electrically insulating resin layer for heat-welding Sc, and conductive layers Sa are provided on both end surfaces.
The edge of is exposed.

The ground electrode 3 is brought into sliding contact with the end faces of the conductive layer Sa exposed on both end faces of the food packaging sheet S, and is brought into direct conduction with the conductive layer Sa. Thereby, the conductive layer Sa itself acts as a substantial ground electrode plate. The high voltage power supply 9 applies a high voltage of about several kV and several kHz between the ground electrode 3 and the detection electrode 7. The voltage of the power source 9 is set so that the discharge current does not flow unless the sheet S has a pinhole and the discharge current exceeding the threshold value flows when the pinhole exists. Therefore, if there is no pinhole in the food packaging sheet S that is in contact with the detection electrode 7, electric discharge does not occur between the detection electrode 7 and the conductive layer Sa due to the electric insulation effect of the resin surface layer Sb. Therefore, the current value detected by the ammeter 11 does not exceed the threshold value.

On the other hand, if there is a pinhole in the food packaging sheet S that is in contact with the detection electrode 7, the pinhole impairs the electrical insulation effect of the resin surface layer Sb, and the detection electrode 7 and the conductive layer Sa. Discharge occurs between the
Therefore, the current value detected by exceeds the threshold value. It is determined from the change in the current value that the food packaging sheet S has a pinhole, and the control device 13 outputs an operation command to the marker 15 at a predetermined timing. As a result, the marker 1 is attached to the pinhole-generating portion of the food packaging sheet S.
A mark such as ink is attached by 5.

Although the detection electrode 7 is in contact with the food packaging sheet S in the above-described embodiment, the detection electrode 7 may be disposed close to the food packaging sheet S with a small air gap. it can. FIG. 4 is an explanatory diagram of a pinhole defect inspection method for a food container according to the present invention. The food-sealed container A is formed by stacking the above-mentioned food packaging sheet S with the heat-welding resin layer Sc inside and stacking the heat-sealing resin layers Sc on the inside to heat-seal the heat-sealing resin layer Sc. It is formed into a bag containing food. FIG. 5 shows a specific example of the food-sealed container A. This food-sealed container A has a quadrangular shape, and its entire peripheral portion is used as a welding margin b by heat welding. The welding margin b forms an edge portion of the food-sealed container A, and the inside thereof is a food container c having an airtight structure. Has become.

Returning to FIG. 4, the food sealed container A will be described.
The end face of the conductive layer Sa is exposed at the end face of the welding margin b, and the ground electrode 21 is in direct contact with this end face in a conductive state. As a result, the conductive layer Sa of the sheet S itself acts as a substantial ground electrode plate. The detection electrode 23 is in contact with the surface of the food container c, and a high voltage of about several kHz and several kV is applied between the ground electrode 21 and the detection electrode 23 by the high voltage power supply 25. The voltage of the power source 9 is set so that the discharge current does not flow unless the sheet S has a pinhole and the discharge current exceeding the threshold value flows when the pinhole exists. Therefore, also in this case, if there is no pinhole in the food packaging sheet S of the food storage portion c that is in contact with the detection electrode 23, the electrical insulation effect of the resin surface layer Sb causes a gap between the detection electrode 23 and the conductive layer Sa. No discharge current above the threshold will occur.

On the other hand, if the food packaging sheet S in the food container c that is in contact with the detection electrode 23 has a pinhole p, the pinhole p impairs the electrical insulating action of the resin surface layer Sb and the detection is performed. Discharge occurs between the electrode 23 and the conductive layer Sa, and the current value detected by the ammeter 27 exceeds the threshold value. It is determined from the change in the current value that the food packaging sheet S has a pinhole.

The detection electrodes 23 are preferably arranged on the upper and lower surfaces of the food container c so as to face each other, and in this case, pinhole defects on both surfaces of the food container A can be inspected at the same time. Also in the present embodiment, the detection electrode 23 may be placed close to the food container A with a small air gap without contacting it. Further, the ground electrode is formed of a needle-shaped electrode, and the ground electrode is pierced into the welding margin b that does not hinder the sealing performance of the food container c of the food sealed container A. Layer S
It can also be electrically connected to a.

FIGS. 6 to 8 show an embodiment of the pinhole defect inspection device for a food-sealed container according to the present invention. 6 is a top view of the apparatus, FIG. 7 is a side view, and FIG. 8 is a cross-sectional view taken along the line AA of FIG. 6 in which the food sealed container is located at the detection position. In this embodiment, the guide members 49 are provided on both sides of the belt conveyor device 47 that conveys the food container A. The guide member 49 is made of an electrically insulating material such as plastics and has slit-shaped guide grooves 51 for receiving the welding margins b on both sides of the food sealed container A horizontally conveyed by the belt conveyor device 47. The ground electrode 31 is fixedly arranged at the groove bottom of the guide groove 51, and the inlet of the guide groove 51 is expanded in the vertical and horizontal directions to accurately guide the welding margin b of the food sealed container A to the arrangement of the ground electrode 31. It has a tapered shape. As a result, the conductive layer S exposed on the end faces of the welding margin b on both sides of the food-sealed container A.
The end face of a surely comes into conductive contact with the ground electrode 31 which is horizontally conveyed by the belt conveyor device 47. Guide groove 5
A container sensor 53 that detects that the leading edge of the food-sealed container A has passed through the inlet 1 is provided near the inlet.

A brush-shaped detection electrode 33 is arranged above the belt conveyor 47 so as to be able to contact the upper surface of the food-sealed container A. Between the ground electrode 31 and the detection electrode 33, several kHz or several kHz are provided. A high frequency high voltage power supply 35 for applying a voltage of about kV is connected. The guide member 49 made of an electrically insulating material hides the edge portion of the food-sealed container A from the brush-shaped detection electrode 33, and the detection electrode 33 is connected to the ground electrode 31 via a conductive layer exposed at the edge portion. It also has the function of preventing short circuits.

A current detector 37 for detecting the current value of the current flowing therethrough and a maintenance resistor 39 of about several MΩ are connected in the middle of the wiring that electrically connects the high-frequency high-voltage power supply 35 and the detection electrode 33. The current detector 37 has a DC amplifier 39
And the DC converter 43 are connected in order, and the current detector 3
The current value detection signal output from 7 is amplified by the DC amplifier 41, converted into a signal indicating a DC current value by the DC converter 43, and input to the calculator 45.

The calculator 45 has a direct current value of the detection electrode 33.
It is determined whether or not a predetermined threshold value corresponding to the discharge current due to the discharge between the ground electrode 31 and the ground electrode 31 is exceeded, and if the DC current value exceeds the threshold value, a signal for discharging the food sealed container A as a pinhole defective product. Is output to a defective product discharge shooter control unit (not shown). The food sealed container A is conveyed by the belt conveyor device 47, and the brush-shaped detection electrode 3
3 is in sliding contact with the upper surface of the food-sealed container A, and the ground electrode 31 is
The food sealing container A is brought into sliding contact with the end surface of the conductive layer Sa exposed on the end surface of the welding margin b, and is brought into conduction with the conductive layer Sa. Thereby, the conductive layer Sa itself acts as a substantial ground electrode plate.

If there is no pinhole on the upper surface of the food-sealed container A that is in contact with the detection electrode 33, no electric discharge will occur between the detection electrode 7 and the conductive layer Sa due to the electrical insulation effect of the resin surface layer Sb. On the other hand, if there is a pinhole in the food-sealed container A that is in contact with the detection electrode 33, the pinhole impairs the electrical insulation action of the resin surface layer Sb, and the detection electrode 33 and the conductive layer Sa are separated from each other. Is discharged, and the current value detected by the current detector 37 exceeds the threshold value. In this case, the calculator 45 outputs a discharge signal to the defective product discharge shooter controller.

FIG. 9 shows a control system of the pinhole defect inspection apparatus shown in FIGS. This control system includes an inspection timing setting unit 55 that inputs a detection signal from the container sensor 53. The inspection timing setting unit 55 receives the detection signal from the container sensor 53, and is determined by the conveyance speed of the belt conveyor 47, the distance from the position of the sensor 53 to the detection electrode 33, the width of the welding margin b of the food sealed container A, and the like. The inspection period is set for each container, and only the current comparison result within this inspection period is valid.

As a result, the detection electrode 33 comes into contact with the conductive layer Sa exposed on the end face of the welding margin b at the leading edge or the trailing edge of the food hermetic container A during the transportation process of the food hermetic container A. Even if the soaring current value exceeds the threshold value, it can be avoided that the pinhole defect is determined. FIG. 10 shows an output example of the DC converter 43. The calculator 45 detects the pinhole defect by comparing the output voltage V with a predetermined voltage threshold Vs. In FIG. 10, reference numeral T
The period indicated by is the inspection period set by the inspection timing setting unit 55, and if the output voltage V of the DC converter 43 exceeds a predetermined threshold Vs within this inspection period T, it is determined to be a pinhole defect. It

Therefore, in FIG. 10, only the voltage peak indicated by the symbol Pp due to the pinhole defect is recognized as the pinhole defect, and the detection electrode 33 is the welding margin b of the front edge of the food container A. The voltage peak Pa due to contact with the conductive layer Sa exposed on the end face or the voltage peak Pb due to contact with the conductive layer Sa exposed on the end face of the welding margin b at the trailing edge is used for the determination. Excluded from comparison. Therefore, even if the voltage peaks Pa and Pb exceed the voltage threshold value Vs, the pinhole is not determined to be defective, and erroneous determination can be prevented.

11 to 13 show another embodiment of the pinhole defect inspection apparatus for food sealed containers according to the present invention. 11 to 13, parts corresponding to those in FIGS. 6 to 8 are denoted by the same reference numerals as those in FIGS. 6 to 8 and their description is omitted. In this embodiment, two container conveying belt conveyor devices 57 and 5 arranged in series are used.
9 is provided, and a pair of upper and lower roller-shaped detection electrodes 33 are provided at the connecting portion between the belt conveyor devices 57 and 59. The lower detection electrode 33 is rotatably supported at a predetermined height position above the frame 61, and the upper detection electrode 33 is rotatably engaged with a vertically elongated hole 63 formed in the frame 61. However, the spring force of the spring 65 presses the lower detection electrode 33.

Each of the pair of upper and lower detection electrodes 33 has a conductive small diameter portion 33a and electrically insulating large diameter portions 33 at both ends thereof.
b, which defines a space through which the food container c of the food-sealed container A passes between the upper and lower small-diameter portions 33a.
b, the heat-sealed seal portions on both side edges of the food-sealed container A,
That is, the welding margin c is sandwiched. Belt conveyor device for container transportation 5
The guide members 49 having the ground electrodes 31 are arranged on both sides in the vicinity of the end of 7, and the ground electrodes 32 are also arranged on both sides in the vicinity of the start of the container conveying belt conveyor device 59.

In this embodiment, the welding allowances b on both sides of the food-sealed container A horizontally conveyed by the container conveyer belt conveyor device 57 are engaged with the guide grooves 51 of the guide member 49, and the welding allowances b are the guide grooves. Welding margin b while passing through 51
The end face of the conductive layer Sa of the above-mentioned makes conductive contact with the ground electrode 31 or 32, and the food sealed container A enters between the pair of upper and lower detection electrodes 33. The sealed food container A has welding margins b on both sides.
Is sandwiched between the upper and lower large-diameter portions 33b, and the food storage portion c passes between the small-diameter portions 33a, and both upper and lower surfaces thereof are in sliding contact with the upper and lower small-diameter portions 33a. As a result, the pinhole defect inspection on the upper and lower surfaces of the food-sealed container A is simultaneously performed.

[0035]

According to the present invention, a pinhole defect inspection in a laminated food packaging sheet including a conductive layer formed of a metal foil can be efficiently and reliably performed. Further, according to the present invention, the pinhole defect inspection of the food sealed container with the laminated food packaging sheet containing the conductive layer of the metal foil is efficiently performed,
Moreover, it can be performed with a high degree of certainty, and all products can be inspected on the production line.

[Brief description of drawings]

FIG. 1 is a schematic side view illustrating an example of a pinhole defect inspection method for a food packaging sheet.

FIG. 2 is a plan view of a main part of FIG.

FIG. 3 is a diagram showing a relationship between an end portion of a food packaging sheet and a ground electrode.

FIG. 4 is a schematic cross-sectional view illustrating a pinhole defect inspection method for a food container.

FIG. 5 (a) is a plan view showing an example of a food-sealed container,
(B) is the longitudinal cross-sectional view.

FIG. 6 is a schematic plan view showing an embodiment of a pinhole defect inspection device for a food container.

7 is a schematic side view of the device shown in FIG.

8 is a diagram showing a schematic cross section of the device shown in FIG. 6 and a signal detection system.

FIG. 9 is a block diagram showing a control system of a pinhole defect inspection device for a food container.

FIG. 10 is a diagram showing an example of detection signals in a pinhole defect inspection device for a food container.

FIG. 11 is a plan view showing another embodiment of the pinhole defect inspection device for a food container.

12 is a schematic side view of the apparatus shown in FIG.

FIG. 13 is a diagram showing an embodiment of a detection electrode used in a pinhole defect inspection device for a food container.

[Explanation of symbols]

1 ... Sheet winding portion, 3 ... Ground electrode, 7 ... Detection electrode,
9 ... Power supply, 11 ... Ammeter, 13 ... Control device, 15 ... Marker, 21 ... Ground electrode, 23 ... Detection electrode, 25 ... Power supply,
27 ... Ammeter, 31, 32 ... Ground electrode, 33 ... Detection electrode, 35 ... Power supply, 37 ... Current detector, 45 ... Computational unit, 4
9 ... Guide member, 53 ... Container sensor, 55 ... Inspection timing setting section, 65 ... Spring, S ... Food packaging sheet, Sb
... resin surface layer, Sa ... conductive layer, Sc ... resin layer for heat welding,
3A ... food sealed container, b ... welding allowance, c ... food container

Claims (7)

[Claims] 1. A pinhole defect inspection method for a food packaging sheet having a resin layer laminated with a conductive layer sandwiched therebetween, wherein a ground electrode is brought into contact with a conductive layer exposed on an end face of the sheet,
A pinhole defect inspection method for a food packaging sheet, characterized in that a voltage is applied between the ground electrode and a detection electrode in contact with or brought close to the surface of the sheet to detect the presence or absence of a discharge current. 2. A method of inspecting a pinhole for a food-sealed container, which is formed by heat-welding a food-packaging sheet in which a resin layer is laminated with a conductive layer sandwiched therebetween, wherein a ground electrode is electrically conductive to the food-packaging sheet. A pinhole defect in a food-sealed container characterized by detecting the presence or absence of a discharge current by applying a voltage between the ground electrode and a detection electrode in contact with or brought close to the surface of the food-sealed container. Inspection methods. 3. The method of inspecting a pinhole for a food-sealed container according to claim 2, wherein the ground electrode is brought into contact with a conductive layer exposed at an edge of the food-sealed container. 4. The detection electrode is brought into contact with or close to both sides of the food container, respectively, and pinhole defects on both sides of the food container are simultaneously inspected.
Alternatively, the method for inspecting a pinhole for a sealed food container according to item 3. 5. A pinhole defect inspection device for a food-sealed container, which is formed by heat-sealing a food packaging sheet having a resin layer laminated with a conductive layer sandwiched between the ground electrode, the detection electrode, and the both electrodes. A power source and a current detector connected to the ground electrode, the ground electrode is disposed in contact with the edge of the food container, and the detection electrode is disposed in contact with or accessible to the surface of the food container. A food sealed container characterized by detecting a pinhole defect by detecting a discharge current flowing when a voltage is applied between the ground electrode and the detection electrode by the power supply by the current detector. Pinhole defect inspection device. 6. A pinhole defect inspection apparatus for a food-sealed container, which is formed by heat-sealing a food-packaging sheet in which a resin layer is laminated with a conductive layer interposed therebetween, and a transport means for transporting the food-sealed container. A ground electrode disposed on the side of the conveying means so as to be able to contact the edge portion of the food-sealed container, and a pair arranged so as to be in contact with or approachable to both sides of the food-sealed container conveyed by the conveying means. A detection electrode, a power supply and a current detector connected to the ground electrode and the detection electrode, container detection means for detecting that the food sealed container transported by the transport means has passed a predetermined position, An inspection timing setting unit for setting an inspection period for each container in response to a detection signal from the container detection unit, wherein the current detection is performed within the inspection period set by the inspection timing setting unit. A pinhole defect inspection device for a sealed food container, which detects a pinhole defect when a current detected by a dispenser exceeds a threshold value. 7. The pair of detection electrodes are composed of a small diameter portion and roller electrodes having large diameter portions at both ends thereof and are arranged to face each other, and the large diameter portions are electrically insulating and both side edges of the food sealed container. The pinhole defect inspection device for a food-sealed container according to claim 6, wherein the heat-sealed seal portion is guided.