Double-Walled Container Structure With Inverted Inner Wall Forming
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Solution Overview
Problem
Current methods for mass-producing double-walled containers are either incapable of producing commercially viable thin-walled containers or result in high production costs due to limitations in existing blow-forming technologies, such as extrusion-blow moulding and thermoforming, which struggle with achieving uniform wall thickness and high production speeds.
Innovation Solution
A method and apparatus for stretch-blow moulding double-walled containers from thermoplastic tubular blanks, where the blanks are mechanically stretched and blow-formed with controlled gas pressure to achieve a blow ratio less than 3, allowing for the formation of integral dual-containers with a mirror-image inverted structure, enabling the production of thin-walled containers with uniform wall thickness suitable for mass production.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If extrusion-blow moulding or thermoforming is used to mass-produce double-walled containers, then production speed can be increased, but wall thickness uniformity deteriorates and production costs increase
Solution Approach 1:
The patent applies parameter changes by controlling the blow ratio to be less than 3, which is a specific parameter threshold. This controlled parameter change enables the formation of uniform thin walls while maintaining high production speed through the stretch-blow moulding process
Solution Approach 2:
The patent segments the container formation process into two distinct stages: first forming an integral dual-container with containers extending in opposite directions, then inverting one container to achieve the final double-walled structure with containers extending in the same direction. This segmentation allows each stage to be optimized independently for both speed and precision
2Productivity
If blow ratio is increased to improve production efficiency, then production speed increases, but wall thickness uniformity and structural integrity deteriorate
Solution Approach 1:
The patent explicitly sets the blow ratio parameter to be less than 3, which resolves the contradiction by finding the optimal parameter value that balances production efficiency with wall thickness uniformity and structural integrity. This parameter threshold is critical to the invention's success
3Loss of substance
If wall thickness is reduced to minimize material usage, then material waste decreases, but structural integrity and heat-insulation properties deteriorate
Solution Approach 1:
The patent uses the nested doll principle by inverting one container inside the other to create the double-walled structure. This nesting approach allows the use of thin walls for material efficiency while the nested configuration itself provides the structural integrity and heat-insulation properties that would otherwise require thicker walls
Solution Approach 2:
The patent transitions from a single-walled structure to a double-walled nested structure, adding a dimensional aspect to the design. This dimensional change allows thin walls to achieve the same functional performance (structural integrity and heat insulation) that would require much thicker single walls
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 method enables the production of double-walled containers with wall thicknesses significantly less than 0.35 mm and high uniformity, reducing material waste and production costs, while maintaining structural integrity and heat-insulation properties.
Implementation Method 1
the tubular blank is then mechanically stretched in a longitudinal-axis direction with an LS substantially greater than 1, and blow-formed outwardly by gas pressure
Implementation Method 2
blow-formed outwardly by gas pressure such that RLmax is less than 3
Implementation Method 3
maintaining structural integrity and heat-insulation properties
Data Source
AI summary
A method and apparatus for the formation of double-walled containers with the structure of two integrally connected and adjacent containers extending in the same direction with an air gap between them, stretch-blow moulded as single bodies out of thermoplastic material, and suitable for mass-production. A thermoplastic tubular blank is formed and then heat-conditioned. The heat-conditioned tubular blank is then mechanically stretched longitudinally and blow-formed outwards by gas pressure to conformingly and stretchingly assume the tubular blank to the shape of a first dual-container shaped mould cavity set in order to form a stretch-blow moulded first container integrally connected to a second container, with both containers extending in opposite directions. Next, additional heat-conditioning is applied to further heat-condition as necessary the stretch-blow moulded second container and if deemed an advantage, at least part of the first container. Then at least one profiled inversion piston shaped as a male mould member with an outer surface configuration that defines the inner surface configuration of the article being formed and a second container shaped mould cavity set with a single-container shaped configuration are provided along with one or more wall stability devices which are applied to at least part of the wall surface(s) of either or both of the two integrally connected stretch-blow moulded containers, such that the second smaller container side wall(s) are at least substantially not in contact with the second container shaped mould cavity set and may be inverted at least partially inside-out, while at the same time the second smaller container bottom wall at least substantially does not invert, in order for the second smaller container to become a substantially mirror-image inverted second smaller container extending in the same direction as, and interior to, the first container.