Electricity: measuring and testing – For insulation fault of noncircuit elements
Reexamination Certificate
2002-05-31
2004-09-21
Le, N. (Department: 2858)
Electricity: measuring and testing
For insulation fault of noncircuit elements
Reexamination Certificate
active
06794885
ABSTRACT:
TECHNICAL FIELD
The present invention relates to a method and a device for detecting pinholes on hermetically sealed packages, which wrap, with an electric insulating film, conductive contents, e.g, medical consumable products such as blood products and normal saline solutions, as well as foods, etc.
BACKGROUND ART
Hermetically sealed packages are used in a variety of products today to maintain the sterilized condition of the contents of these products. These products include a number of products, for example, a variety of medical consumable products such as blood for transfusion and blood products, as well as food products such as retort foods.
It is extremely important to inspect these hermetically sealed packages for pinholes. A pinhole in the package of a medical consumable product causes contamination or decomposition of the contents. A pinhole in the package of a food product causes the contents to contact the atmosphere, leading to decomposition or decay of the contents.
In a conventional method for detecting pinholes, for example, that described in Japanese (Examined) Patent Application Publication S50-6998 (1975), a subject, which is a packaged item, is placed between a pair of electrodes. When a voltage is applied to these electrodes while substantially differentiating the electrostatic capacity formed between one electrode and the subject and the electrostatic capacity formed between the other electrode and the subject, a spark is produced between one electrode and the subject, causing an electric current. The existence of a pinhole can be detected when the electric current is detected.
In the above method, in which the existence of a pinhole is detected by detecting the electric current caused by the spark, the existence of a pinhole is actually detected by the variation in the strength of the detected current (whether it becomes stronger or weaker).
In this case, when a voltage is applied to the two electrodes that hold a hermetically sealed package between them, either a leakage current or a charging current always flows regardless of the existence of a pinhole. Such a current becomes stronger as the voltage becomes higher. The current is also affected by the climate, for example, the humidity and temperature of the periphery of the subject, which form the atmosphere at the time of the inspection. The leakage current, for example, becomes stronger when it rains or when the humidity is high. Fine floating dust also affects the electric current at the detector. When checking the existence of a pinhole by the magnitude of the electric current running in a short period of time, the detector sometimes concludes that there is a pinhole even if there is no pinhole. In this method, malfunctions are inevitable.
Moreover, when a high voltage is applied to the two electrodes holding a hermetically sealed package between them, an electric potential difference concentrates on the weak portion of the electric insulating film of the hermetically sealed package, providing a cause for pinholes. As a result, there will be more pinholes, adversely affecting the subject.
In order to solve these problems, the applicant invented a method (Japanese Pat. No. 2908751, etc.) in which a hermetically sealed package is installed on a supporting electrode that is grounded, a high direct current voltage is applied between the supporting electrode and yet another electrode that contacts or approaches the test portion of the hermetically sealed package in close proximity, and the electrode that contacts the test portion is grounded while the ground of the supporting electrode is disengaged or kept engaged, thereby detecting a discharge current from the test portion to inspect the hermetically sealed package for pinholes.
According to this method, the existence of a pinhole on a hermetically sealed package can be checked efficiently, but the method still requires a series of inspection procedure. In a further exploration for an easier procedure, the applicant developed a technology that does not require the supporting electrode that contacts the side surface of the hermetically sealed package (Japanese Patent Application H10-211868 (1998), Japanese Patent Application H11-16597 (1999)).
In this method, an electrode is placed so as to contact or approach the test portion of the hermetically sealed package in close proximity, and a high voltage is applied between the test portion of the hermetically sealed package and the supporting electrode that supports the hermetically sealed package. In the previously mentioned method in which the existence of a pinhole is detected by detecting the current generated by a spark, a high voltage is applied between the electrodes that hold the hermetically sealed package. In either method, while it is possible to check whether or not there are pinholes on the surface of the test portion of the hermetically sealed package that the supporting electrode contacts, it is impossible to check whether or not there are pinholes on the two, relatively wide, opposing surfaces of the hermetically sealed package in simultaneous inspections of the both surfaces.
During the course of further explorations and experiments for a better method of inspection that replaces the above method, the applicant discovered that when a high voltage is applied to a hermetically sealed package having relatively flat surfaces through its two opposing surfaces, it is possible to check whether or not there are pinholes on at least one of the relatively flat opposing surfaces of the hermetically sealed package in simultaneous inspections from the both surfaces. This discovery has led to the present invention.
The present invention is extremely effective when it is applied to hermetically sealed packages having flat surfaces, in particular, those containing such contents as medical consumable products including blood products, e.g., blood for transfusion, plasma, etc., as well as foods, etc., including retort foods. The present invention can also be applied to packages that do not have flat surfaces, for example, those having circular arc surfaces, as long as the conductive elements of the present invention can contact relatively wide areas of the exterior circular arc surfaces.
DISCLOSURE OF INVENTION
According to the inspection method of the present invention, while a hermetically sealed package
3
, which wraps, with an electric insulating film
2
, conductive contents
1
, e.g., blood for transfusion, blood products, etc., is conveyed, a conductive element
5
arranged on one side of the package's path A and at least one of the two longitudinally arranged conductive elements
6
,
6
arranged on the other side are made to simultaneously contact the opposing surfaces of the contents
1
—existing portion of the hermetically sealed package
3
. In this condition, a high voltage is applied to the hermetically sealed package
3
to detect a change in the electric current at the portion where the conductive element
5
contacts or the portion where at least one of the two conductive elements
6
,
6
contacts, thereby detecting a pinhole on the hermetically sealed package
3
.
Using this method, the conductive element
5
arranged on one side of the path A and at least one of the two longitudinally arranged conductive elements
6
,
6
arranged on the other side contact the portions of the opposing surfaces of the contents
1
—existing portion of the hermetically sealed package
3
. In this condition, a high voltage is applied to the hermetically sealed package
3
to detect a change in the electric current at the portion where the conductive element
5
contacts or the portion where at least one of the two conductive elements
6
,
6
contacts, thereby checking the existence of a pinhole on at least one of the portions on the opposing surfaces of the contents
1
—existing portion of the hermetically sealed package
3
in simultaneous inspections of both surfaces.
According to the inspection device of the present invention, two conveyors
4
,
4
for conveying the hermetically sealed package
3
,
He Amy
Joven Denki Kabushiki Kaisha
Koda & Androlia
Le N.
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