Plastic Closure Varying Retention Force High-Speed Application
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Solution Overview
Problem
Plastic closures formed from thermoplastic polymeric materials face challenges in high-speed application due to increased clearance between the closure and container, leading to misapplication and impaired sealing performance, especially with containers having multiple thread starts, which can result in damaged threads and reduced sealing efficiency.
Innovation Solution
The closure is configured with a varying retention force that decreases in a direction away from the top wall portion, achieved by staggering the centerlines of thread segments and varying thread profiles, including a large cross-sectional area closer to the top wall and a small cross-sectional area further down, along with axially extending gas-venting grooves and reinforcing elements to facilitate even thread contact and reduce material usage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If the thickness of the side wall portion is reduced to achieve weight savings, then the weight of the closure decreases, but the clearance between the inside of the skirt portion and the container finish increases, leading to misapplication and impaired sealing performance
Solution Approach 1:
The patent applies local quality by varying the thickness of the side wall portion along its length. The side wall is thicker near the top wall to provide structural support and maintain proper clearance for sealing, while being thinner near the bottom to reduce overall weight. This gradient thickness distribution allows the closure to achieve weight savings without compromising sealing performance.
Solution Approach 2:
The patent employs dynamics by designing the side wall portion with a gradual thickness transition rather than a uniform thickness. This dynamic variation in thickness allows the closure to adapt to the clearance requirements during high-speed application while maintaining structural integrity where needed, thus preventing misapplication and maintaining sealing reliability.
2Ease of operation
If the closure threads are made smaller to facilitate easier engagement with multiple thread starts, then the tendency to cock decreases, but the closure becomes easier to strip during application, resulting in damaged threads and large variation of application angle
Solution Approach 1:
The patent applies parameter changes by optimizing the thread dimensions and pitch to achieve a balance between engagement ease and strip resistance. The thread parameters are specifically designed to work with multi-start threads on containers, allowing smooth engagement without cocking while maintaining sufficient strength to prevent stripping during application.
3Productivity
If the closure is designed for high-speed automatic application, then the productivity increases, but the clearance between closure and container must be precisely controlled to avoid misapplication
Solution Approach 1:
The patent applies segmentation by dividing the side wall portion into multiple zones with different thickness characteristics. This segmentation allows each zone to serve a specific function: one zone controls the clearance for proper engagement, another provides structural support, and a third reduces weight. This segmented approach enables high-speed application while maintaining precise clearance control.
Data Source
AI summary
A plastic closure embodying the principles of the present invention comprises a closure cap having a top wall portion, and an annular skirt portion depending from the top wall portion. The skirt portion includes an internal thread formation for threaded engagement with the external thread formation of an associated container. In order to facilitate high-speed application, and minimize the use of polymeric material, the closure is configured to exhibit a variation in retention force which decreases in a direction away from the top wall portion of the closure cap.