Orientatable Screw Closure with Anti-Backoff Thread
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Solution Overview
Problem
Screw-on closures tend to loosen due to temperature changes, material creep, relaxation of sealant materials, and vibrations, leading to issues like false tampering indications, spillage, and moisture ingress, especially with high-pitch threads that require minimal twisting for removal and reinstallation.
Innovation Solution
A closure and container combination featuring a screw thread formation with a recess or break in the neck, an abutment surface, and a thread stop to prevent back-off, where the closure screw thread is flared at the abutment surface to maximize the stop surface area, ensuring secure engagement without hindering unscrewing.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the screw threads have a high pitch to enable quick removal and reinstallation, then the ease of operation is improved, but the reliability deteriorates due to increased tendency to back off
Solution Approach 1:
The thread formation is segmented into functional zones: a first portion with higher pitch for ease of engagement and removal, and a second portion with lower pitch for anti-back-off functionality. This segmentation allows each zone to optimize for its specific purpose without compromising the other.
Solution Approach 2:
The pitch parameter of the screw thread is varied along the axial length of the closure. The pitch transitions from a first value in the upper portion to a second value in the lower portion, creating a gradient that balances ease of operation with anti-back-off reliability.
2Reliability
If the closure is designed to prevent back off, then the reliability is improved, but the ease of operation deteriorates due to difficulty in unscrewing
Solution Approach 1:
Different portions of the thread formation have different local qualities: the upper portion has higher pitch and fewer engagement points for easy engagement and removal, while the lower portion has lower pitch and more engagement points for strong anti-back-off resistance. The operator can easily engage and remove the closure at the upper portion without overcoming the anti-back-off features at the lower portion.
Solution Approach 2:
The thread formation dynamically transitions from a high-pitch, low-resistance region to a low-pitch, high-resistance region. During normal engagement and removal, the closure interacts primarily with the high-pitch portion. During back-off prevention, the low-pitch portion engages to provide resistance.
3Reliability
If the stop surface area is maximized to prevent back off, then the reliability is improved, but the device complexity increases due to flared thread formation
Solution Approach 1:
The anti-back-off feature is merged with the screw thread formation itself rather than being a separate component. The flared portion and variable pitch are integrated into the thread structure, eliminating the need for additional anti-back-off devices while providing both secure engagement and back-off prevention.
Data Source
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AI summary
In combination, an orientatable closure (10) and a container, the closure having a screw thread formation (30, 35) and the neck of the container having a screw thread formation, one end of the closure screw thread formation comprising an abutment surface, at one end of the neck screw thread a thread stop is provided for engaging the abutment surface so as to orientate the closure on the container, in which a recess or break is provided in the neck screw thread, and in which the closure screw thread is provided with an anti-backoff formation (50) for releasably engaging in the recess or break to prevent backing off of the closure when fully screwed on, the engagement of the anti-backoff formation can be overcome to unscrew the closure in use.