Heat-Sealed Metal Disk Closure for Retort Container Seal Integrity
Solution Overview
Problem
Conventional container closures with plastisol sealants face challenges in maintaining a continuous compressive force during retort processing, leading to potential seal breaches.
Innovation Solution
A container assembly with a closure that uses a heat-sealable metal disk and a tamper-evident band with ratchets and spring fingers, where the disk is heat-sealed to the container rim and an upward force is applied to break the seal upon unscrewing, eliminating the need for continuous compressive force.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If plastisol sealant is used to seal the container, then the container can be sealed closed, but the seal can be breached during retort processing because the sealant's ability to seal depends on continuous compressive force from the plastic cap
Solution Approach 1:
The patent replaces the mechanical sealant system (plastisol requiring continuous compressive force) with a heat-sealing system. The metal disk is heat-sealed to the container rim, creating a permanent bond that does not require ongoing mechanical compression to maintain seal integrity during retort processing.
Solution Approach 2:
The patent changes the sealing mechanism from a mechanical/compressive system to a thermal bonding system. By applying heat to melt the plastic material and bond the metal disk to the container rim, the seal becomes thermally fixed rather than mechanically maintained, eliminating the need for continuous compressive force.
2Reliability
If the closure is designed to maintain continuous compressive force on the sealant, then seal integrity may be improved, but the device complexity increases and the closure becomes more difficult to operate
Solution Approach 1:
The patent eliminates the complex mechanical system required to maintain continuous compressive force on a sealant. Instead, a simple heat-sealing process creates a permanent bond between the metal disk and container rim, significantly reducing closure structure complexity while maintaining or improving seal integrity.
3Reliability
If a heat-sealed metal disk is used instead of plastisol sealant, then the seal does not depend on continuous compressive force, but the manufacturing process becomes more complex
Solution Approach 1:
The patent changes the sealing approach from chemical sealant application to thermal bonding. The metal disk is heat-sealed to the container rim through a controlled heating process that melts the plastic material, creating a strong permanent bond. This thermal process, while requiring heat application, eliminates the need for sealant mixing, application, and curing steps.
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 provides a reliable hermetic seal that does not depend on maintaining continuous compressive force, ensuring the seal remains intact during processing and easy to open without breaching.
Implementation Method 1
The upper end of the finish is a rim whose upper surface defines a sealing surface formed of a heat-sealable material
Data Source
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AI summary
An assembly (10) of a container (20) and a closure (40). The container has a rim (26) defining an upper sealing surface (28) formed of a heat-sealable material, and an external screw thread (24) extending helically along an outer surface at a location spaced below the rim. The closure includes a screw cap (42) assembled with a separately formed disk (60) inserted in the cap, the closure defining an internal screw thread (48) for attaching the closure to the container when the closure is rotated in a first direction. The disk is constructed of a laminated metal having an upper metal layer (62) and a lower heat-sealable layer (64) affixed to an underside of the metal layer. A heat seal between the heat-sealable layer of the disk and the upper sealing surface of the rim affixes the disk to the rim such that the disk seals closed the open top end of the container.