Method and apparatus for integral double-walled container structures
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Solution Overview
Problem
Current production methods for mass-producing double-walled containers are either incapable of producing integral double-walled containers or result in commercially cost-prohibitive unit costs due to limitations in achieving thin, uniform wall thickness and high production speeds.
Innovation Solution
A method and apparatus for stretch-blow moulding thermoplastic tubular blanks with controlled mechanical and gas pressure stretching to form integral double-walled containers with thin, uniform walls, involving heat-conditioning, mechanical stretching, and gas pressure blow-forming, along with profiled inversion pistons and wall stability devices to invert the second container, ensuring a partially or fully enclosed air gap for improved insulation and structural integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If conventional production methods are used to manufacture double-walled containers, then production speed can be maintained, but wall thickness uniformity deteriorates and cannot achieve thin walls below 0.35 mm
Solution Approach 1:
The container is segmented into two distinct walls (first wall and second wall) with an air gap between them, allowing each wall to be formed and controlled independently. This segmentation enables precise control of wall thickness for each individual wall while maintaining high production speed through the integrated molding process.
Solution Approach 2:
The patent utilizes parameter changes in the molding process, specifically controlling the injection pressure, temperature, and cooling rates to achieve uniform thin walls. By optimizing these parameters, the process can produce walls thinner than 0.35 mm with high uniformity while maintaining production efficiency.
2Loss of substance
If material is reduced to achieve thin walls, then production cost decreases, but structural integrity deteriorates
Solution Approach 1:
The patent employs a nested structure where one container wall is positioned inside another with an air gap between them. This nested configuration provides enhanced structural integrity through the dual-wall design while using less material overall compared to a single thick wall, thereby reducing material waste.
Solution Approach 2:
The double-walled structure acts as a composite system where the two walls and the air gap between them work together to provide structural strength. This composite approach allows for thinner individual walls while maintaining or improving overall structural integrity compared to a single solid wall.
3Reliability
If double-walled structure is implemented for insulation, then insulation efficiency improves, but device complexity increases
Solution Approach 1:
The patent merges the formation of two container walls and the creation of the insulating air gap into a single integrated molding process. This combining of operations achieves effective insulation through the double-walled structure while avoiding the complexity of separate assembly steps, thereby maintaining manufacturing simplicity.
4Loss of substance
If wall thickness is reduced to minimize material use, then production cost decreases, but manufacturing precision requirements increase
Solution Approach 1:
The patent incorporates preliminary design features into the mold cavities, such as optimized gating systems and cooling channel arrangements, that ensure uniform material distribution and cooling from the outset. This preliminary action enables the production of consistently thin walls with precise thickness control while minimizing material consumption.
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
Enables the mass 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 insulation efficiency.
Implementation Method 1
heat-conditioned to a first heat-conditioned temperature within the heat-softened temperature range but below the melt temperature of the thermoplastic material
Implementation Method 2
blow-formed outwardly by gas pressure such that RLmax is less than 3
Implementation Method 3
the second smaller container side wall(s) 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
Implementation Method 4
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
Data Source
AI summary
A method and apparatus for the formation of double-walled containers includes two integrally connected 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 form first and second containers. A piston and mould cavity cooperate to further mould the 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 inside-out, while 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.