Plastic Closure Disk Retention for High-Temperature Seals
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Solution Overview
Problem
High-temperature applications, such as pasteurization, hot fill, and retort processes, cause elevated internal pressure in containers, leading to closure distortion and seal disruption between the closure and container neck finish, especially in plastic closures used for beverages, food, and pharmaceuticals.
Innovation Solution
A plastic closure design featuring a shell with a central opening and skirt, a disk with angularly spaced fingers and external beads that engage a conical ledge, ensuring the disk remains retained during shell removal, and a resilient liner for enhanced sealing, preventing the beads from snapping through the opening.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If a plastic closure is used for high-temperature applications, then the closure can be subjected to elevated internal pressure and high temperatures, but the closure distorts or domes and the seal between the closure and container neck finish is interrupted
Solution Approach 1:
The closure is segmented into distinct functional components: a shell for structural support, a disk for sealing, and a liner for enhanced sealing. This segmentation allows each component to perform its specific function optimally under high-temperature conditions without compromising overall seal integrity.
Solution Approach 2:
The liner is pre-installed on the disk before assembly, creating a preliminary sealing barrier that maintains seal integrity even when the closure is subjected to elevated internal pressure and temperature during high-temperature applications.
2Ease of operation
If the closure shell is removed from the container neck finish, then the closure can be opened, but the disk may be left retained on the neck finish causing seal disruption
Solution Approach 1:
The retention mechanism is inverted: instead of the disk being retained by the shell during normal operation, the shell is designed to be removed while the disk remains retained on the neck finish through engagement with the container threads. This inversion ensures the sealing surface remains in place for potential re-closure.
Solution Approach 2:
The container neck finish threads act as an intermediary retention mechanism, engaging with the shell to hold the disk in place during normal operation, and continuing to retain the disk even after shell removal, preventing seal disruption.
3Strength
If the beads on the fingers engage the central opening to retain the disk, then the disk is secured within the shell, but the beads may snap through the central opening during shell removal
Solution Approach 1:
The bead geometry is optimized with specific dimensional parameters: the bead diameter is sized to provide sufficient frictional engagement with the central opening edges to retain the disk during normal operation, but small enough to allow controlled removal of the shell without snapping through, balancing retention strength with ease of removal.
Data Source
AI summary
A plastic closure includes a plastic closure shell having a base wall with a central opening and a skirt for securing the closure to a container neck finish. A plastic disk includes angularly spaced fingers extending into the central opening of the shell base wall and external beads on the fingers for engaging an inner periphery of the central opening to retain the disk within the shell. The beads have flat undersurfaces and the inner periphery of the central opening has a ledge with a conical surface engaged by the beads. Any doming that occurs in the disk and/or the closure shell base wall increases the surface contact between the finger beads and the opposing surface of the ledge so that removal of the shell from a container neck finish will simultaneously lift and remove the disk from the neck finish without having the beads snap through the central opening in the shell so that the shell is removed while the disk is retained on the neck finish.