Double Container Mouth Structure for Pullable Inner Bag Separation
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Solution Overview
Problem
Existing double containers face issues with separation of the inner bag from the outer shell, twisting of the inner bag during use, shrinkage of the inner bag during cooling, difficulty in handling the separated inner bag, and the need to improve gas barrier properties while maintaining pullability.
Innovation Solution
The double container design includes features such as a larger body part diameter than the mouth part, alternating wall thickness in the bottom part, and a concave-convex shape in the mouth part to facilitate easy separation of the inner bag, along with a preform composition that ensures both polyolefin and amorphous PET are softened within an overlapping temperature range, and an EVOH layer with a high ethylene content for improved gas barrier properties.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If the inner bag and outer shell are loosely fitted at the mouth part to facilitate separation, then the inner bag can be easily pulled out, but the inner bag rotates relative to the outer shell causing twisting
Solution Approach 1:
The patent applies preliminary action by forming a projection on the inner bag at the mouth part before assembly. This projection engages with a corresponding recess in the outer shell, pre-establishing a mechanical interlock that prevents rotation during subsequent operations. The anti-rotation feature is built into the structure beforehand, eliminating the need for additional components while maintaining ease of separation through the loose fit design.
2Reliability
If the inner bag is tightly fitted in the outer shell to prevent rotation, then twisting is suppressed, but the inner bag cannot be easily pulled out for separation
Solution Approach 1:
The patent applies local quality by creating different fit characteristics at different locations of the inner bag. The mouth part region features a loose fit with a projection-recess engagement mechanism that allows easy separation while preventing rotation. The body part region maintains a tighter fit for stability during use. This localized differentiation of fit quality enables both easy separation and twisting suppression simultaneously.
3Ease of manufacture
If the inner preform is made of homopolypropylene and outer preform of amorphous PET, then the materials have good processing properties, but the inner bag shrinks during cooling causing gap formation and content loss
Solution Approach 1:
The patent applies parameter changes by modifying the cooling process parameters specifically for the inner preform. A controlled cooling rate is applied to the inner homopolypropylene preform during biaxial stretch blow molding, and the molding temperature is optimized to prevent excessive shrinkage. These parameter adjustments maintain the good processing properties of homopolypropylene while eliminating the shrinkage-induced gap formation and content loss issues.
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 allows for easy separation of the inner bag from the outer shell with reduced force, suppresses shrinkage during cooling, enhances handleability, and maintains pullability while improving gas barrier properties.
Implementation Method 1
a preform composition that ensures both polyolefin and amorphous PET are softened within an overlapping temperature range
Data Source
AI summary
A double container where an inner bag can be easily pulled out from an outer shell. The double container includes a container body and a mouth part attachment member is provided. The container body includes a mouth part and a body part and a bottom part. The mouth part is a tubular portion having an open end. The body part is arranged adjacent to the mouth part on a side farther from the open end than the mouth part, and has a larger outer diameter than the mouth part. The bottom part is configured to close a lower end of the body part. The container body includes an inner bag and an outer shell arranged to cover the inner bag. The mouth part attachment member is configured to be attachable to the mouth part, and is configured such that the inner bag rotates as the mouth part attachment member rotates.