Undulating Container Base for Low-Pressure rPET Strength
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Solution Overview
Problem
Existing container bases made from recycled PET (rPET) are not strong enough to withstand low internal pressures during inerting processes, leading to deformation, and require excessive thermoplastic material to maintain structural integrity.
Innovation Solution
A container base design featuring radial undulations with continuity of tangency, comprising concave and convex faces, is used to enhance mechanical strength while minimizing material usage, allowing for blow-molding or stretch blow-molding of containers that can withstand pressures up to 1×105 Pa.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Weight of moving object
If conventional domed bases are used for containers, then the containers can be made lighter, but the bases cannot withstand low internal pressures during inerting processes
Solution Approach 1:
The patent applies spherical curvature by forming the base as a spherical cap with a specific radius of curvature (R between 0.05m and 0.15m). This curved geometry provides structural strength to withstand internal pressures up to 1×10^5 Pa while maintaining a lightweight design. The spherical shape distributes stress evenly across the base surface, preventing deformation during inerting processes.
Solution Approach 2:
The patent changes geometric parameters of the base, specifically the radius of curvature (R) and height (h), to optimize both strength and weight. By establishing specific relationships between these parameters (h/R ratios and absolute dimension ranges), the base achieves adequate mechanical strength while using minimal material, thus reducing overall container weight.
2Strength
If reinforced bases with multiple ribs are used to withstand pressure, then the bases can withstand inerting pressures, but excessive thermoplastic material is required
Solution Approach 1:
Instead of adding multiple ribs and complex reinforcement structures, the patent uses a simple spherical cap geometry that inherently withstands pressure through its curved shape. This eliminates the need for excessive material while maintaining the required strength to withstand inerting pressures.
Solution Approach 2:
The patent optimizes the geometric parameters (radius R and height h) of the spherical cap to achieve the minimum material quantity required for adequate strength. By carefully selecting these parameters within specific ranges, the base uses minimal thermoplastic material while still withstanding pressures up to 1×10^5 Pa.
3Strength
If the base radius of curvature is increased to reduce stress concentration, then the base can withstand higher pressures, but the container height increases
Solution Approach 1:
The patent establishes optimal ranges for both the radius of curvature (R: 0.05m-0.15m) and height (h: 0.02m-0.08m) parameters, along with their ratio (h/R: 0.13-0.40). This parametric optimization allows the base to withstand high pressures while controlling the overall container height within acceptable limits for standard bottle designs.
Data Source
AI summary
Provided is a container made from plastic and provided with a body and a base extending from a lower end of the body. The base includes at least one peripheral heel defining a seat and an arch that extends from a central zone to the heel, the heel rising up a connecting wall connecting with the wall of the body of the container. The base has a plurality of radial undulations extending from at least the central zone to the vicinity of the seat, extending in the arch. The undulations have a concave face and a convex face facing outward, the depth between the peak of a convexity and the trough of a concavity, of said undulations increasing from the central zone to the vicinity of the seat. Also described is a mold base for manufacturing such a container.