Polygonal Plastic Container Sidewall Concave Panel Design
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Solution Overview
Problem
Large noncircular plastic beverage containers face issues with outward bulging of the sidewall due to hydrostatic pressure, which compromises strength and rigidity while trying to minimize material costs.
Innovation Solution
A plastic container design featuring a substantially polygonal transverse cross-section with side panels that include a flat portion for labels and a central concave portion, optimized with specific radius and rib structures to enhance strength and resistance to bulging, fabricated using the stretch blow molding process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Quantity of substance
If the sidewall is made as thin as possible to minimize material costs, then material costs are reduced, but the strength and rigidity of the sidewall deteriorates
Solution Approach 1:
The patent applies local quality by creating a concave portion in the sidewall at a specific location (lateral mid-point) where hydrostatic pressure is highest. This localized structural modification provides enhanced strength and rigidity exactly where needed to resist bulging, while the rest of the sidewall maintains its thin profile to minimize material usage. The concave portion acts as a stress distribution zone that prevents outward bulging without requiring the entire sidewall to be thicker.
2Quantity of substance
If the container is made noncircular in transverse cross-section to reduce material costs, then material costs are reduced, but resistance to outward bulging of the sidewall deteriorates
Solution Approach 1:
The patent combines noncircular cross-section geometry with a locally added concave portion at the lateral mid-point of the sidewall. This local modification specifically addresses the bulging issue at the point of maximum hydrostatic pressure, allowing the container to maintain its noncircular shape for material efficiency while gaining targeted resistance to outward bulging where it is most needed.
Solution Approach 2:
The concave portion introduces a curved surface element into the otherwise polygonal or noncircular sidewall profile. This curved geometry at the critical stress point helps distribute hydrostatic pressure more effectively and prevents sharp corners or flat surfaces from concentrating stress that would lead to bulging, while still maintaining the overall noncircular cross-sectional shape for material efficiency.
3Reliability
If a concave portion is added to the sidewall to improve resistance to bulging, then resistance to outward bulging is improved, but device complexity increases
Solution Approach 1:
The sidewall is segmented into distinct functional zones: upper substantially flat portion for label reception, central concave portion for bulging resistance, and lower substantially flat portion for label reception. This segmentation allows each zone to perform its specific function optimally while maintaining overall structural simplicity. The concave portion is isolated as a discrete feature rather than a complex overall structural change, making it easier to manufacture using conventional blow molding techniques.
Solution Approach 2:
The patent modifies the geometric parameters of the sidewall by introducing a concave portion with specific dimensional characteristics (average radius between 1.0 to 2.0 times the maximum lateral dimension). This parameter-based approach allows for standardized manufacturing and simplifies the design process, as the concave portion can be created using conventional mold design techniques without requiring complex multi-step manufacturing processes.
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 design effectively improves the resistance to outward bulging of the sidewall without significant increases in material costs, as demonstrated by finite element analysis showing flexure patterns that maintain label adhesion and structural integrity.
Implementation Method 1
The preform is first heated and then is longitudinally stretched and subsequently inflated within a mold cavity
Implementation Method 2
the preform is then longitudinally stretched and subsequently inflated within a mold cavity so that it assumes the desired final shape
Implementation Method 3
The polymer solidifies upon contacting the cooler surface of the mold
Data Source
AI summary
A plastic container includes a finish portion defining an opening and a main body portion having a shape that is substantially polygonal in transverse cross-section. The main body portion has a maximum lateral dimension. At least one of the side panels includes a substantially flat portion for receiving a label and a concave portion having an average radius. A ratio of the average radius to the maximum lateral dimension is substantially within a range of about 1.0 to about 2.0. The side panel having the concave portion further has an inwardmost portion and an outwardmost portion, with a first maximum lateral distance being defined between the inwardmost portion and the outwardmost portion. A second maximum lateral distance is defined between the inwardmost portion and one of the substantially flat portions. A ratio of the first distance to the second distance is substantially within a range of about 0.8 to about 1.2.