Heat-Resistant PET Container Bottom Deformation Control
Find Innovative SolutionsGenerate Solutions
Solution Overview
Problem
Heat-resistant containers made by blow molding with polyethylene terephthalate (PET) face deformation issues under reduced pressure, which complicates the mold design, increases material usage, and restricts label design due to the need for vacuum panels or ribs, making them heavy and costly.
Innovation Solution
A method involving two-phase blow molding where a thin-walled raised bottom portion is formed in the first phase and the surrounding wall portion is thickened in the second phase, allowing the raised bottom portion to displace inwardly and accommodate pressure reduction without external panels, maintaining container rigidity and self-supporting properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If vacuum panel portions or three-dimensional portions (ribs) are provided in the wall section to suppress deformation under reduced pressure, then deformation resistance is improved, but device complexity and material usage increase
Solution Approach 1:
The invention applies local quality by creating a raised bottom portion with different wall thickness characteristics compared to the surrounding wall. The raised bottom portion has a first wall section with greater thickness and a second wall section with lesser thickness, allowing localized deformation accommodation without affecting the entire container structure or requiring complex mold modifications throughout.
Solution Approach 2:
The bottom portion is segmented into distinct wall sections with different thicknesses. The first wall section has greater thickness while the second wall section has lesser thickness, creating zones with different mechanical properties that work together to accommodate reduced pressure without requiring additional vacuum panels or ribs throughout the container.
2Reliability
If vacuum panel portions or ribs are added to prevent deformation, then deformation resistance is improved, but weight increases
Solution Approach 1:
Instead of uniformly increasing wall thickness throughout the container, the invention locally modifies only the bottom portion with segmented wall thicknesses. The second wall section has lesser thickness to minimize material usage and weight, while the first wall section has greater thickness to provide necessary structural support and deformation resistance.
3Reliability
If vacuum panel portions are provided in the wall section, then deformation resistance is improved, but manufacturing cost increases
Solution Approach 1:
The invention achieves deformation resistance through localized wall thickness variations in the bottom portion rather than adding separate vacuum panels or ribs. This integrated approach modifies the existing mold cavity shape rather than requiring additional mold components, thereby reducing manufacturing complexity and cost.
4Shape
If the wall surface is kept flat to maintain commercial value, then appearance quality is improved, but deformation resistance under reduced pressure deteriorates
Solution Approach 1:
Instead of adding external protrusions (ribs or vacuum panels) to the container wall, the invention inverts the approach by creating a raised bottom portion that deforms inward. The second wall section with lesser thickness is designed to collapse inward under reduced pressure, accommodating volume reduction while maintaining the external flat appearance of the container wall.
5Reliability
If a raised bottom portion with thinner wall is formed to accommodate pressure reduction, then deformation resistance is improved, but structural strength may be compromised
Solution Approach 1:
The invention applies local quality by creating spatially varying wall thicknesses in the bottom portion. The first wall section has greater thickness to maintain structural strength and support, while the second wall section has lesser thickness to allow controlled deformation and pressure accommodation. This differentiated design ensures both strength and flexibility where needed.
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
This approach enables heat-resistant containers to handle deformation under reduced pressure without additional structural elements, reducing material usage, weight, and maintaining a flat surface for improved commercial value and label design flexibility.
Implementation Method 1
a resin preform is heated to a temperature suitable for blow molding
Implementation Method 2
blow molding is performed, with the folded-back portion and the raised bottom portion thinner than the surrounding wall portion being pressed from outside
Implementation Method 3
the interior of the bottle has an atmosphere at reduced pressure, as the volume of the contents decreases
Implementation Method 4
When the interior of the product falls into a reduced-pressure atmosphere, the raised bottom portion is displaced toward the interior to accommodate pressure reduction
Data Source
Figure 1~2
Figure 3(a)~3(b)
Figure 4
AI summary
An invention of a method for production of a heat-resistant container, in which a raised bottom portion is displaced inwardly by reduction in internal pressure, is disclosed. The method is characterized by forming a raised bottom portion 11 smaller in wall thickness than a surrounding wall portion 12a by first blow molding using a heat-treating blow mold; and pushing up the raised bottom portion 11 by a secondary bottom mold, in performing second blow molding using a final blow mold, to increase the wall thickness of the surrounding wall portion 12a (ground portion 12) relative to the raised bottom portion.