Two-Part Closure Reducing Opening Force via Segmented Torque
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Solution Overview
Problem
Existing two-part closures require excessive force to open due to vacuum resistance, as the combined torque for unscrewing and breaking the seal is high, especially when dealing with containers that experience negative pressure.
Innovation Solution
A two-part closure design featuring a disc and skirt where the disc is held by an inwardly projecting rim and lugs, allowing separate stages of torque application to rotate the skirt and pry the disc away from the container, with the lugs only needing to resist crushing forces, thus reducing the material thickness and effort required.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the lugs are made stronger to resist vacuum forces, then the sealing reliability is improved, but the opening force becomes excessively high
Solution Approach 1:
The opening process is segmented into two distinct stages: first rotating the skirt to activate tamper-evident features, then prising the disc from the container. This segmentation allows the lugs to be optimized for prising rather than having to handle both unscrewing and seal-breaking forces simultaneously.
Solution Approach 2:
The closure transitions from a static sealed state to a dynamic opening sequence. The skirt rotates first, then the disc is prised away, creating a dynamic two-stage opening mechanism that reduces the peak force required compared to a single-stage opening.
2Strength
If thicker material is used for the lugs, then the strength to resist crushing forces is improved, but the weight and material usage increase
Solution Approach 1:
The lugs only need to resist crushing forces during the second stage of opening when the disc is prised away, not during the initial unscrewing stage. This dynamic loading condition allows for thinner, lighter lug design while maintaining adequate strength for the specific prising function.
3Reliability
If the disc is held tightly by the inwardly projecting rim and lugs, then the seal integrity is improved, but the torque required to open the closure increases
Solution Approach 1:
The holding mechanism is segmented into the inwardly projecting rim providing initial containment and the lugs providing secondary retention during prising. This segmentation allows the disc to be held securely during sealing while enabling controlled release through the two-stage opening process.
Solution Approach 2:
The retention system transitions from a static tight hold during sealing to a dynamic controlled release during opening. The skirt rotation precedes disc removal, dynamically managing the release of sealing forces to reduce peak opening torque.
Data Source
AI summary
A two-part closure (1) which has a disc (2) and a skirt (3). In one example, the skirt wall is smooth between upper and lower rims so that the disc is moveable between the rim features. Typically in a metal skirt or ring, the upper rim feature is a curl (11) and the lower rim feature is a curled edge (12) with equi-spaced lugs (13) on the skirt wall.