JPS63101728A - Pinhole presence inspector for sealed packed body - Google Patents

Abstract

PURPOSE:To secure accurate inspection regardless of the state of wetting, fouling and the like of a sealed packed body, by arranging first and second detectors different in current varying with the presence of a pinhole in series in a detection path provided with a detection electrode. CONSTITUTION:Detectors 5 and 6 are composed of filters or the like and the first detector 5 is so set as to draw a current component with less change regardless of the presence of a pinhole. The second detector 6 is so set as to take out an electric current component with greater change in the presence of a pinhole. Then, for example, a sealed packed body made for bean curd is arranged between electrodes 2 and 3. When a pinhole exists in the packing of the bean curd 4, a difference is generated between electrical signals of electrodes of the first and second detectors 5 and 6 to be outputted as detection signal with a differential circuit 7.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a hermetically sealed package for inspecting the presence or absence of pinholes and seal defects in a package in which an object to be inspected is hermetically packaged with an electrically insulating material such as plastic or glass. The present invention relates to a device for inspecting the presence or absence of pinholes in the body.

As an inspection device of the above type, a voltage is applied between a pair of electrodes 12 and 13, as shown in FIG. A method is known in which the presence or absence of a pinhole is detected by detecting the generated discharge current.

Detection devices using this method can detect pinholes in various sealed packages such as ampoules and sausages, but because the S/N ratio is low, there is a problem in that false signals are generated when external conditions are added. For example, when inspecting the top seal of a cup container containing tofu, if the container is dirty or wet, the current value will change significantly and an erroneous signal will be generated.

To solve this problem, as shown in Fig. 6, the detection electrodes 13a and 13b are divided into a plurality of parts, a current detector 15, 16 is provided for each detection electrode, and the discharge current of this detector is detected. A method using a method of extracting the difference as a detection signal has been proposed. The inspection device with this configuration has a S/N
Since the ratio is improved, even if external conditions such as the above-mentioned dirt and water wetness are added, there is no risk of generating an erroneous signal, which is advantageous.

However, in this device, it is necessary to make the capacitance of each electrode approximately equal to the contents in the sealed container, which is structurally difficult. If the detection electrodes are arranged as shown in Figure 6 and the sealed package is transported and inspected in the vertical direction of the drawing, the magnitude of the signals from the detectors 15 and 16 will be different if the position shifts in the left and right direction. It will be number 31. Furthermore, as shown in Fig. 7, if an inspection is carried out while transporting the object to be inspected in the direction in which the detection electrodes are arranged, the magnitude of the signals from the detectors 15 and 16 will be different at the exit and entrance, resulting in an erroneous signal. Become.

SUMMARY OF THE INVENTION An object of the present invention is to solve the above-mentioned conventional problems and provide a pinhole presence/absence inspection device for a sealed package that can perform a reliable inspection with a simple configuration.

The present invention solves the above problems by adding a method to the path for detecting the discharge current.
A first detector that extracts a current component whose difference is not large when a pinhole is present in the object to be inspected compared to a signal when there is no pinhole, and a second detector that extracts a current component whose difference is large. The problem was solved by arranging the detectors in series, and providing a circuit that inputs the signals of the first and second detectors and outputs the differential value of the signals as a detection signal.

15 pieces Embodiments of the present invention will be described below with reference to the accompanying drawings.

In Fig. 1, numeral 1 is the electric voltage, 2 is the high voltage electrode,
3 is a detection electrode, and a sealed package configured as tofu 4 is placed between the electrodes 2 and 3.

In this case, the tofu 4 is conveyed by a conveyor belt (not shown) in a direction perpendicular to the drawing, and at that time an inspection is performed for the presence of pinholes, but the explanation of this mechanism is not the gist of the present invention. Therefore, it will be omitted.

In the pinhole presence/absence detection device according to the present invention, a first detector 5 and a second detector 6 are installed in series in a detection path in which a detection electrode 3 is provided. In this case, the detectors 5 and 6 are composed of filters and the like, and on the other hand, for example, the first detector 5 is set to extract a current component that does not change much even when there is a pinhole. Further, the second detector 6 is set to extract a current component that changes greatly when a pinhole is present.

The detected currents of the first detector 5 and the second detector 6 are outputted to a circuit, for example, a differential circuit 7, which converts the detected currents into electrical signals and outputs the difference as a detected signal. It is configured to do so.

In the pinhole presence/absence inspection device having this configuration, if there is a pinhole in the packaging of tofu 4, when the detected current of the first detector 5 is converted into an electric signal, there is little change as shown in FIG. Further, as shown in FIG. 3, the electrical signal from the second detector 6 changes greatly due to the flow of electrical discharge due to the pinhole. When the difference between these signals is output as a detection signal by the differential circuit 7, a signal as shown in FIG. 4 is obtained.

As is clear from the graph in FIG. 4, in the present invention, the detection signal is between 0 and 300 mV in the case of a non-defective product, while the detection signal is between 1.8 and 2.2 V in the case of a pinhole, seal failure, etc. is obtained. Therefore, the S/N ratio of the present invention is quite large, 6 to 7, and reliable pinhole inspection can be performed even if the container of tofu 4 is wet with water. In addition, in the conventional inspection apparatus shown in FIG. 5, the S/N ratio is 1.5 to 2.5 as shown in FIG.
0, which shows the superiority of the present invention. Therefore, the present invention is particularly effective in inspecting sealed packages, such as tofu, which are likely to be contaminated with water during packaging.

The pinhole presence/absence inspection device according to the present invention is constructed as described above, and is capable of reliable inspection even when external conditions such as water and dirt are added to the sealed package, and moreover, it is capable of detecting areas that cannot be inspected. There is no risk of this occurring, which is extremely advantageous.

[Brief explanation of the drawing]

FIG. 1 is a circuit diagram of the present invention, FIGS. 2 and 3 are graphs of signals obtained from the first detector and the second detector, respectively, and FIG. 4 is a graph showing detection signals of the present invention. Figures S to 7th
The figure is a conventional circuit diagram, and FIG. 8 is a graph showing signals obtained by the inspection device shown in FIG. 1...Power supply 2...High voltage electrode 3...Detection electrode 4...Tofu 5...First detector
6...Second detector 7...Differential circuit Fig. 1 Fig. 3 Fig. 2 m5ec Fig. 4 Fig. 5 Fig. 7 Fig. 6

Claims (1)

[Claims] A pinhole presence/absence test in which a sealed package, which is the object to be inspected, is placed between electrodes, and a voltage is applied between the electrodes to detect the electrical discharge current of the object to be inspected to check for the presence of pinholes. In the apparatus, in the path for detecting the discharge current, a first detector extracts a current component in which a signal when there is a pinhole in the object to be inspected does not have a large difference from a signal when there is no pinhole; A circuit that arranges in series a second detector that extracts a current component with a large difference, inputs the signals of the first detector and the second detector, and outputs the difference between the detected values of the signals as a detection signal. The pinhole presence/absence inspection device is characterized in that it is provided with: