Measuring and testing – With fluid pressure – Leakage
Reexamination Certificate
1999-12-17
2001-10-30
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
C073S045400, C073S052000
Reexamination Certificate
active
06308556
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to product testing, and more particularly to a method and apparatus for determining whether a sealed product contains holes that permit an unacceptable amount of gas flow into or out of the sealed product.
BACKGROUND OF THE INVENTION
Many products are produced in an air-tight manner for environmental, health, freshness, operational and/or other reasons. To meet the need for air-tight products, test equipment have been developed to test certain types of products for leaks. For example, U.S. Pat. No. 5,861,546 ('546 Patent) to Sagi et al., the disclosure of which is hereby incorporated by reference, discloses a leak detection apparatus that is suitable for detecting leaks in a product having an opening to which a leak sensor and a vacuum system may be coupled in order to form a closed test system. Once coupled to the opening of the product, the vacuum system exerts a low vacuum on the product thus resulting in gas flow from the product through the leak sensor to the vacuum system. Assuming that the product does not have a gross leak, the pressure within the product and the pressure maintained by the vacuum system will eventually equalize and enter a steady state condition. Once equalization occurs, the leak sensor determines the steady state mass flow rate for the gas flow between the product and the vacuum system which is indicative of the level of leakage occurring in the closed test system. Assuming all leakage in the closed test system is attributable to the product under test, a detected mass flow rate of zero would indicate the product contains no leaks, a small mass flow rate would indicate the product contains a small leak, and a larger mass flow rate would indicate the product contains a larger leak. The leak sensor then determines a test result based upon the mass flow rate and predetermined tolerances.
One disadvantage of the leak detection system of the '546 Patent is that the product to be tested is generally required to include some sort of opening to which the leak sensor and the vacuum system may be coupled in order to form the closed test system. While certain products such as automotive engines and heat exchangers include openings to which the leak sensor and the vacuum system may be coupled, many other products do not include such an opening. For example, many medical products are distributed and stored in sealed, air-tight packages in order to maintain freshness, maintain sterility, and/or prevent harm to the surrounding environment. These packaged medical products by design do not include openings. Accordingly, these packaged medical products cannot be tested by the leak detection system of the '546 Patent in a non-destructive manner.
A need, therefore, exists for a method and apparatus that are suitable for testing sealed products (i.e. products that contain no openings) for leaks.
SUMMARY OF THE INVENTION
The present invention addresses the above-identified need, as well as others, with a method and apparatus of testing a sealed product for leaks. In accordance with one embodiment of the present invention, there is provided a method of nondestructive testing a sealed product for leaks. The method includes the steps of placing the sealed product into a test chamber, and sealing the test chamber after the placing step to obtain a sealed test chamber at an initial internal pressure. Another step of the method includes maintaining in a pressure system, a substantially constant internal pressure that is different than the initial internal pressure of the sealed test chamber. Yet another step of the method includes permitting gas flow between the sealed test chamber and the pressure system during the test period thereby causing the sealed test chamber to approach the substantially constant internal pressure of the pressure system. The method also includes the step of obtaining a value representative of a total mass of the gas flow between the sealed test chamber and the pressure system during the test period. Moreover, the method includes the step of determining, based upon the value obtained for the total mass of the gas flow, whether the sealed product leaked an unacceptable amount during the test period.
Pursuant to another embodiment of the present invention, there is provided a leak detection system for nondestructive testing a sealed product for leaks. The leak detection system includes a test chamber, a pressure system that is operable to maintain a substantially constant pressure during a test period, and a leak sensor coupled to the test chamber via a first conduit and the pressure system via a second conduit. The test chamber of the leak detection system includes a receptacle dimensioned to receive the sealed product. Moreover, the test chamber includes a cover dimensioned to operably seal the receptacle at an initial internal pressure when placed into position with the receptacle. The leak sensor of the leak detection system is operable to permit gas flow between the test chamber and the pressure system via the first conduit and the second conduit. The leak sensor is also operable to obtain a value representative of total mass of the gas flow between the sealed test chamber and the pressure system during the test period. Furthermore, the leak detection system is operable to determine, based upon the value obtained for the total mass of the gas flow, whether the sealed product leaked an unacceptable amount during the test period.
Pursuant to a further embodiment of the present invention, there is provided a leak sensor for use with a pressure system operable to maintain a substantially constant pressure during a test period and a sealed test chamber containing a sealed product. The leak sensor includes a body, a differential pressure sensor, a temperature sensor, a static pressure sensor, and a microcontroller. The body of the leak sensor includes a first end portion that is operable to be coupled to the test chamber via a first conduit and a second end portion that is operable to be coupled to the pressure system via a second conduit. Moreover, the body of the leak sensor includes a laminar flow gap between the first end portion and the second end portion that causes gas flowing through the body to exhibit substantially laminar flow characteristics during the test period.
The differential pressure sensor of the leak sensor is connected to a first point and a second point of the laminar flow gap. Furthermore, the differential pressure sensor is operable to generate a differential pressure signal that is representative of the differential pressure between the first point and the second point of the laminar flow gap. The temperature sensor of the leak sensor is operable to generate a temperature signal representative of temperature of the gas flow through the laminar flow gap, and the static pressure sensor of the leak sensor is operable to generate a static pressure signal representative of static pressure developed by the gas flow through the laminar flow gap.
The microcontroller of the leak sensor is connected to the differential pressure sensor, the temperature sensor, and the static pressure sensor. The microcontroller is operable to calculate the value representative of the total mass of the gas flow between the sealed test chamber and the pressure system during the test period based upon the differential pressure signal, the temperature signal, and the static pressure signal. Moreover, the microcontroller is further operable to determine, based upon the value obtained for the total mass of the gas flow, whether the sealed product leaked an unacceptable amount during the test period.
It is an object of the present invention to provide an improved method and apparatus for testing a sealed product for leaks.
It is also an object of the present invention to provide a new and useful method and apparatus for testing a sealed product for leaks.
It is another object of the present invention to provide a method and apparatus that test a sealed product in a non-destructive manner
Ghosh Ranajit Rana
Sagi Nehemiah Hemi
Zhang Guosen Ronald
ATC, Inc.
Bose McKinney & Evans LLP
Poutzer Jay L.
Williams Hezron
LandOfFree
Method and apparatus of nondestructive testing a sealed... does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Method and apparatus of nondestructive testing a sealed..., we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Method and apparatus of nondestructive testing a sealed... will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-2617451