Data processing: measuring – calibrating – or testing – Measurement system in a specific environment – Mechanical measurement system
Reexamination Certificate
2002-06-11
2004-02-17
Shah, Kamini (Department: 2863)
Data processing: measuring, calibrating, or testing
Measurement system in a specific environment
Mechanical measurement system
C073S799000, C073S049300, C324S557000
Reexamination Certificate
active
06694268
ABSTRACT:
TECHNICAL FIELD OF THE INVENTION
This invention pertains to a leakage inspection method for a sealed container in which a liquid is liquid-tightly contained for inspecting whether a defect such as a pinhole or a crack causing a leakage of the liquid exists in the container and a leakage inspection apparatus for carrying out the leakage inspection method.
BACKGROUND OF THE INVENTION
A liquid such as an injection and an eye lotion that is required to avoid contamination by bacteria and deterioration by oxidization etc. is liquid-tightly preserved in a container formed of glass or plastic materials. The container to contain this kind of liquid is not allowed to have leakage. To this end, in the manufacturing process of products such as a medicine which should be shipped in a sealing manner, it is required to inspect whether a leakage generating a defect such as a pinhole or a crack, etc exists in the container or not.
In order to inspect the leakage of the sealed container formed of an insulating material such as a glass, a plastic material or the like in which the liquid is contained, there is known a method of observing a discharge phenomenon generated when an inspection voltage of AC high voltage is applied across the container.
As electrodes are put onto two places (inspection parts) of an outer surface of the insulating container in which the electrolytic liquid is contained and the AC high voltage is applied across the electrodes as the inspection voltage, an AC current flows through an electrostatic capacitance between the electrodes and the liquid in the container and through the liquid in the container. In this case, as a crest value of the inspection voltage is set up at a proper value, if the defect which causes the leakage in the inspection part does not exist, a feeble current just flows, but if the defect such as the pinhole or the crack exist in the inspection part and the leakage arises, or if the leakage may possibly arise, an electric discharge arises in the defective portion, and the current which flows across the electrodes increases. Thus, in the case where the liquid in the container is an electrolyte, whether the defect that causes the leakage exists in the inspection part where the electrodes are put from the crest value of the current flowing through the electrodes can be detected.
In the prior art inspection method, the AC current flowing through the electrodes placed onto the container to be inspected and through the container and the contained liquid is detected by a current detection resistance inserted in series to the grounded electrode and the crest value of the thus detected AC current is compared with a threshold value to judge that the leakage causing the defect exists when the crest value of the AC current is higher than the threshold value.
In the case where the liquid in the container is a non-electrolyte having a high resistance, even though the AC high voltage as the inspection voltage is applied across the container, the electric discharge never occurs across the defective portion and a fore-discharge phenomenon is just generated. In this state, since the comparative value relation between the crest value of the current detected when the defect exists and the crest value of the current detected when the defect does not exist is unfixed and in addition thereto, since the difference between the crest value of the current detected when the defect does not exist and the crest value of the current detected when the defect exists cannot be made large, the prior art method in which the crest value of the AC current flowing when the inspection voltage is applied is compared with the threshold value cannot clearly judge the existence of the defect.
In the case where the liquid in the container is the electrolyte having the lower resistance, the existence of the defect can be detected by comparing the crest value of the detected AC current with the threshold value. However, in the case where the liquid in the container is the electrolyte, even though there is no defect in the container, the momentary discharge is generated due to conditions such as a circumference environment, an existence of containment of the surface of the container, etc. so that the pulse noise overlaps the detected current waveform, which possibly causes the misjudgment of the existence of the defect or the mistaking of a good container for an inferior container. Although it is considered that the threshold value for the judgment is made higher in order to avoid such a misjudgment, the ratio of the inferior articles relative to the good articles will undesirably get higher by using the higher threshold value.
On the other hand, if the threshold value for the judgment of the quality is set up at a lower value so that the inspection is performed for a safety, the rate in which the good articles are judged as the inferior articles gets higher, the yield of the product is reduced and the high cost is caused.
Furthermore, in the case where the high voltage is applied across the insulating container formed of a glass, a plastic material etc., the quality of the container is possibly deteriorated and therefore the inspection voltage is desirably set up at a value as low as possible.
SUMMARY OF THE INVENTION
Accordingly, it is a principal object of the invention to provide a leakage inspection method for a sealed container adapted to detect an existence of a defect such as a pinhole or a crack with a high accuracy even though a liquid is either of an electrolyte or a non-electrolyte and to provide a leakage inspection apparatus used for carrying out such a leakage inspection method.
It is another object of the invention to provide a leakage inspection method for a sealed container adapted to perform an inspection even though a voltage used for the inspection is set up at a lower value with a high accuracy and to provide a leakage inspection apparatus used for carrying out such a leakage inspection method.
The present invention relates to a leakage inspection method having as an object of an inspection an insulating container in which a liquid is sealed and comprising the steps of applying an inspection voltage of high AC voltage across the container; detecting an AC current flowing through the container and the contained liquid and judging from a detection signal of the AC current whether there exists a defect in the container causing a leakage of the liquid.
In the invention, there is provided an A/D converter for converting an instantaneous value of the detection signal of the AC current into a digital value and there is arithmetically operated a total value of the digital values corresponding to the absolute values of the instantaneous values of the AC current detected during a specific totaling period having a specific relation to the waveform of the AC current. The total value as the value to be judged (referred to as “judgment value” later) is compared with a setting value and it is judged that the defect exists in the container when the total value exceeds the setting value.
The aforementioned totaling period is required to be the specific period always having the specific relation to the waveform of the AC current. There may be selected a period which can be detected on a easily detectable zero cross or peak point, such as period of positive half cycle, a period of negative half cycle, a period of ¼ cycle from the zero cross point to the peak point, a period of ¼ cycle from the peak point to the zero cross point, and a period of n cycle (n is an integer of one or more) for the specific period.
As there is provided the A/D converter, which converts the instantaneous value of the detection signal of the AC current flowing through the container and the contained liquid and also as there is determined the totaling period of the specific period having the predetermined relation to the waveform of the AC current so that the total value of the digital values corresponding to the absolute values of the instantaneous values of the AC current detected during the totaling p
Pearne & Gordon LLP
Rieckermann (Japan) Ltd.
Shah Kamini
LandOfFree
Leakage inspection method for sealed container and apparatus... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Leakage inspection method for sealed container and apparatus..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Leakage inspection method for sealed container and apparatus... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-3345424