Measuring and testing – With fluid pressure – Leakage
Utility Patent
1997-11-26
2001-01-02
Williams, Hezron (Department: 2856)
Measuring and testing
With fluid pressure
Leakage
Utility Patent
active
06167751
ABSTRACT:
TECHNICAL FIELD
The invention relates to the analysis (e.g., detection and rate measurement) of leaks in containers having flexible ends.
BACKGROUND INFORMATION
In packaging, for example, food, beverage, or pharmaceutical products, the products often are placed in rigid containers in which one or both ends of the container are sealed with a removable flexible membrane. The integrity of the seal between the membrane and the container is critical to protecting the product in the container. In addition, a consumer must be able to open the seal by exerting a reasonable amount of force. The need for high seal strength implies that a strong seal should be used, while the need for easy access to the product in the container implies that a weak seal should be used. For those reasons, the strength of the seal must be precisely controlled.
SUMMARY
The invention provides techniques for rapidly determining the presence of minuscule leaks in containers moving on a conveyor at speeds on the order of 1,200 containers per minute. More specifically, the invention provides techniques for measuring leakage in containers having holes with dimensions on the order of 4 microns. In some implementations, the techniques rely upon the behavior of the container's flexible membrane as a result of rapid sequential applications of pressure and vacuum to a chamber surrounding the container.
In one general aspect, the invention features determining whether a container that has a flexible membrane and is moving along a conveyor has a leak. The conveyor carries the container through a first region in which a negative pressure differential between the first region and the interior of the container is established. The conveyor also carries the container through a second region in which a positive pressure differential between the second region and the interior of the container is established. A sensor is configured to detect a transition of the membrane of the container between convex and concave orientations and to produce a signal corresponding to the occurrence of the transition. The sensor is connected to a controller that receives the signal from the sensor and is configured to determine whether the container has a leak based on the transition of the membrane.
Embodiments may include one or more of the following features. For example, the container may pass through the first region prior to passing through the second region, and the sensor may detect a transition of the membrane from a concave orientation to a convex orientation in the second region. The container also may pass through the second region prior to passing through the first region, and the sensor may detect a transition of the membrane from a convex orientation to a concave orientation in the first region.
A negative pressure differential may be generated in the first region by cooling the container. In the second region, the positive pressure differential may be generated by heating the container or by passing the container through a high velocity zone to produce a low pressure zone around the container.
The controller may determine whether the container has a leak based upon a time at which the transition of the membrane occurs. A rejector may be configured to remove a container from the conveyor and the controller may be configured to send a signal to the rejector to cause removal of a container when the controller determines that the container has a leak. This detection of leaks and removal of rejected containers from the conveyor provides the considerable advantage of providing for rapid and continuous inspection of each container.
In another general aspect, a test chamber is configured to receive a container and to apply a controlled cycle of elevated pressure and reduced pressure to the container. A pressure transducer is connected to measure the pressure applied to the container and configured to produce a signal corresponding to the measured pressure. A sensor mounted to measure displacement of a portion of the container and configured to produce a signal corresponding to the measured displacement is connected to a controller. The controller is configured to receive the signals from the pressure transducer and the sensor and to analyze the signals to determine whether the container has a leak.
The test chamber may apply multiple pressure cycles to the container and the controller may measure a leak rate based on changes in a response of the container between different cycles. The controller also may be configured to control the pressure applied in the test chamber.
The test chamber may be configured to test multiple containers at the same time. To this end, a cassette loader may be configured to load containers on to cassettes, a rejector connected to receive a signal from the controller to reject a container and configured to remove the rejected container from the cassette, and a station may be configured to receive cassettes loaded with accepted containers and to remove the containers from the cassettes. The test chamber is configured to receive a cassette loaded with containers and to apply a controlled cycle of elevated pressure and reduced pressure to the containers. Multiple sensors are mounted to measure displacement of a portion of each of the containers in the test chamber and configured to produce signals corresponding to the measured displacements. The controller is connected to the sensors to receive the signals from the sensors and configured to analyze the signals to determine whether any of the containers have leaks.
Additional test chambers, in which each test chamber is configured to receive a cassette loaded with containers and to apply a controlled cycle of elevated pressure and reduced pressure to the containers, may be provided. The leak rate of each container may be measured by applying multiple pressure cycles and determining the leak rate with a controller configured to measure leak rates in the containers based on changes in responses of the containers between different cycles of increased and decreased pressure. Each container may include a flexible membrane that transitions between convex and concave orientations in response to changing pressure in the chamber. The controller may be configured to measure a leak rate based on a change in the pressure at which the transition occurs in different cycles of increased and decreased pressure.
Other features and advantages will be apparent from the following detailed description, including the drawings, and from the claims.
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Beaty John S.
Di Bella Francis A.
Fine David H.
Fraim Freeman W.
Banner & Witcoff , Ltd.
Linek Ernest V.
Politzer Jay L.
Thermedics Detection Inc.
Williams Hezron
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