Thermoplastic Retort Container Seam for Shear-Resistant Sealing
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Solution Overview
Problem
Traditional retort containers made of metal are costly and lack aesthetic appeal, while alternatives using less metal struggle to maintain integrity during retort processing due to pressure and temperature challenges.
Innovation Solution
A retort container with a thermoplastic body and metal ends, where the metal ends are heat-sealed to the thermoplastic using heat-sealable materials to create a strong, shear-stress-resistant seam, allowing the container to withstand internal pressure without compromising the seam.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If traditional metal containers are used for retort processing, then seam integrity is maintained during high pressure and temperature, but cost increases and aesthetic appeal decreases
Solution Approach 1:
The invention uses a composite construction with a metal end and a thermoplastic container body. The metal end provides seam integrity and blow-off resistance, while the thermoplastic body reduces cost and improves aesthetics. The heat-sealable material creates a strong bond between the dissimilar materials, allowing the composite structure to function as a unified container that withstands retort processing.
2Ease of manufacture
If metal usage is reduced in container construction, then cost decreases and aesthetics improve, but blow-off resistance during pressurization deteriorates
Solution Approach 1:
The metal end component is retained and specifically designed with a curl and chuck wall structure that provides excellent blow-off resistance. The metal material's inherent strength compensates for the reduced metal usage in the overall container, while the heat-sealable material ensures the metal end remains securely attached to the thermoplastic body during pressurization.
Solution Approach 2:
The metal end is strategically positioned at the container opening where blow-off resistance is most critical. The curl and chuck wall structures are localized features of the metal end that specifically address the blow-off resistance requirement, while the rest of the container body uses thermoplastic for cost and aesthetic benefits.
3Strength
If heat-sealable material is used to attach metal end to thermoplastic body, then blow-off resistance improves, but manufacturing complexity increases
Solution Approach 1:
The mechanical attachment method (such as mechanical interlocking or adhesives) is replaced with thermal bonding using heat-sealable material. This substitution simplifies the manufacturing process by using a well-established heat sealing technology that can be integrated into existing thermoplastic forming operations, despite the added step of heating.
Solution Approach 2:
The attachment process utilizes parameter changes in the heat-sealable material, which transitions from a solid state to a molten state during heating, then re-solidifies to create a strong bond. This phase change allows for effective bonding without complex mechanical attachment mechanisms.
Applied Scientific Principles
This section explains which scientific principles are used to turn an abstract innovation direction into a practical engineering solution.
Function Achieved in This Case
The solution enhances blow-off resistance and maintains container integrity during retort processing, reducing pressure stress on the seams and enabling efficient sterilization while offering cost and aesthetic benefits.
Implementation Method 1
the interface between the chuck wall and the side wall being fused by heat-sealing of the first heat-sealable material between the radially outer surface of the chuck wall and the inner surface of the side wall
Data Source
AI summary
A container includes a metal end applied and sealed to an all-thermoplastic container body by a crimp-seaming or double-seaming operation. The metal end has an outer curl joined to a chuck wall that extends down from the curl. One or both of the inner surface of the container side wall and the outer surface of the chuck wall has/have a heat-sealable material thereon. The metal end is crimp-seamed or double-seamed to the container body and the heat-sealable material(s) are heated to soften or melt such that the interface between the chuck wall and the side wall is fused. The interface is oriented along a direction relative to internal pressure exerted on the metal end such that stress on the interface caused by the internal pressure is predominantly shear stress.