Double-Walled Container Structure for Lower Inner Bag Pull-Out Force
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Solution Overview
Problem
The separation of the inner bag from a double container requires significant force due to the interference of the inner bag with the outer shell, especially when the materials are different or contents adhere to the inner bag, making recycling difficult.
Innovation Solution
A double container design with a constricted part on the outer shell at a specific height position and a reduced wall thickness of the inner bag at the undercut point, facilitated by biaxial stretch blow molding with a forming mold that includes a protruding part, reduces the force required for separation.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Strength
If the inner bag has sufficient wall thickness to maintain structural integrity, then the inner bag can withstand internal pressure and contents, but the force required to separate the inner bag from the outer shell increases
Solution Approach 1:
The inner bag is designed with non-uniform wall thickness, having a first wall thickness in the upper portion and a second, smaller wall thickness in the lower portion. This local variation allows the bag to maintain sufficient strength where needed while reducing separation force where the bag exits the container, directly resolving the contradiction between structural integrity and ease of separation.
Solution Approach 2:
The forming mold includes a protruding part that pre-forms the inner bag with reduced wall thickness in the lower portion during manufacturing. This preliminary action embeds the thickness variation into the bag structure itself, ensuring that when the bag is later removed from the container, the reduced thickness at the exit point minimizes the separation force required while the upper portion retains adequate thickness for structural support.
2Force
If the inner bag wall thickness is reduced at the undercut point, then the force required to separate the inner bag from the container body is reduced, but the inner bag may become too thin to maintain structural integrity
Solution Approach 1:
The inner bag features spatially varying wall thickness with a first thickness in the upper portion and a second, reduced thickness in the lower portion. This local differentiation allows the bag to be weak where separation occurs (reducing pull-out force) while remaining strong where structural support is needed (upper portion containing contents), thereby resolving the contradiction between ease of separation and structural integrity.
3Adaptability or versatility
If the outer shell and inner bag are made of different materials for recycling purposes, then selective recycling becomes possible, but the bonding between materials becomes more complex and difficult to separate
Solution Approach 1:
The forming mold's protruding part pre-forms the inner bag with reduced wall thickness at the lower portion during manufacturing. This preliminary structural preparation ensures that when different materials are used for the outer shell and inner bag, the separation process becomes easier because the pre-thinned section reduces friction and mechanical interlocking at the exit point, allowing selective recycling while minimizing separation resistance.
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 reduces the force needed to separate the inner bag by minimizing the wall thickness at the undercut point, enhancing recyclability and ease of use.
Implementation Method 1
a method for manufacturing a double container, comprising a step of manufacturing a container body by biaxially stretch blow molding a preform using a forming mold
Data Source
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AI summary
To provide a double container in which the force required to separate an inner bag from a container body can be reduced. According to the present invention, provided is a double container comprising a container body having an inner bag and an outer shell arranged to cover the inner bag, wherein the inner bag is configured to be pullable from the container body, and a constricted part is provided on an outer surface of the outer shell at a first height position, which is a starting point of an undercut part where the inner bag interferes with the outer shell when pulling the inner bag from the container body.