Package making – Methods – Forming a cover adjunct or application of a cover adjunct to...
Reexamination Certificate
2003-03-21
2004-11-30
Gerrity, Stephen F. (Department: 3721)
Package making
Methods
Forming a cover adjunct or application of a cover adjunct to...
C053S129100, C053S490000, C215S349000, C215S350000, C215S352000
Reexamination Certificate
active
06823651
ABSTRACT:
FIELD OF THE INVENTION
The present invention relates generally to a sealing system for a container. More specifically, the present invention relates to sealing system for a container and a closure having a lining seal. The sealing system has been found to be beneficial for use with, among others, retort containers.
BACKGROUND OF THE INVENTION
Many food products have long been delivered to customers in sealed plastic containers. In many instances sealed containers containing food products were subjected to thermal processing. For example, it is known to subject such products to a retort process to stabilize and preserve the food product by killing undesirable organisms therein. Retort was a process by which a sealed container was subjected to a system by which the internal product was heated in a pressurized environment for an extended period of time. Typically, the container and its contents were heated to a predetermined temperature, thereby increasing the internal pressure. Then the container and its contents were then maintained at the predetermined elevated temperature and pressure for a period of time sufficient to kill the undesirable organisms therein. Finally, the container and its contents were cooled and the internal pressure was decreased to ambient levels. The increased pressure and temperature experienced by the container during retort resulted in increased internal forces that adversely affected the container's seal.
It was known to use a gasket liner to seal a container that was to be subjected to a retort process. A gasket liner seal utilized a thin flexible polymer gasket held against the finish of the container under compression forces generated by the closure. The effectiveness of the gasket liner was dependent on the position of the closure with respect to the finish of the container. Differential shrinkage rates between the thermoplastic materials forming the closure and the container, combined with increased differential pressure (i.e., internal vs. external pressure), caused “back off” of the closure and the gasket liner and resulted in a less effective sealing mechanism. That is, as the closure and container experienced differential shrinkage and the pressure increased within the container, the closure was pushed away from the upper surface of the finish, lessening the compression imparted to the gasket. Failure of the sealing mechanism rendered the packaged product defective.
FIG. 1
illustrates a cross-sectional exploded view of the finish portion of a prior art container and a closure having a gasket that was used to package products to be retorted.
FIG. 1
is an example of a container having a reamed finish for interacting with a compressible gasket. The internal diameter of this finish configuration of the container was reamed to reduce the cross-sectional area of the portion of the container's finish that would contact the gasket. The reduced cross-sectional area produced an increased pressure on the gasket and caused it to sink deeper into the seal. Reamed containers were problematic for sealing retort containers. For example, reamed containers required multiple stages of processing before being made suitable for packaging products. First the containers were molded, then the molded containers were trimmed to remove excess material, the containers were then reamed to reduce the thickness of the finish, and finally the containers were cleaned to remove chips of plastic from the container that resulted from the reaming process. The ream requirement was therefore responsible for two manufacturing steps.
FIG. 2
demonstrates how a container having a reamed finish interacted with a closure having a compressible gasket. As shown, the reamed finish pushed against the compressible gasket to form a seal.
FIG. 3
shows the container and closure during a retort, or other heat intensive process. The arrows in
FIG. 3
demonstrate the forces caused by the increased internal pressure and the resulting “back-off.” As shown, the increased forces pushed outwardly along the thinned finish wall and upwardly on the closure. The internal forces caused the seal between the container and the closure to be degraded. Further, the portion of the finish that was reamed was weakened by the removal of material and the internal pressure could deform the weakened finish causing further degradation of the seal.
SUMMARY OF THE INVENTION
The present invention provides a seal system for a container and a closure having a compressible gasket. The finish of the container is configured to compress the gasket to provide an effective compression seal and reduce oxygen permeation rate of the container. The finish has a raised seal surface, such as, for example, an angled land portion, configured to dig into the compressible gasket. The compressible gasket wraps around the point of contact providing the effective compression seal. The closure system of the present invention is particularly advantageous for use with containers to be subjected to retort or other thermal processing.
It is one of the principal objectives of the present invention to provide a sealing system for a retort container.
It is another objective of the present invention to provide a container configured to engage a compressible gasket to form a compression seal.
It is a further objective of the present invention to provide a sealing system that allows for an effective compression seal to be formed along the finish of a retort container sealed using ANSI recommended torque parameters.
It is yet another objective of the present invention to provide a scaling system for a container that maintains the integrity of the seal despite closure back-off.
It is still another objective of the present invention to provide a container for retort that does not requiring a reaming process.
These and other objectives of the present invention will become apparent upon examining the drawings and figures together with the accompanying written description thereof.
REFERENCES:
patent: 111607 (1871-02-01), Bissell
patent: 2686606 (1954-08-01), Froitzheim
patent: 4425410 (1984-01-01), Farrell et al.
patent: 5341949 (1994-08-01), Hayes
patent: 5455180 (1995-10-01), Reid
patent: 5664694 (1997-09-01), Bietzer et al.
patent: 5992658 (1999-11-01), Berger
patent: 6006937 (1999-12-01), Baravaglio et al.
Physical Sample of Container.
Lamb James R.
Thierjung George A.
Gerrity Stephen F.
McDermott Will & Emery LLP
Pechiney Emballage Flexible Europe
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