Double Container Inner Bag Rotation for Easy Pull-Out
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Solution Overview
Problem
Existing double containers face issues with separation of the inner bag from the outer shell, particularly when different materials are used, adherence of content to the inner bag, twisting of the inner bag during cap attachment, shrinkage during cooling, difficulty in handling the separated inner bag, and deterioration of gas barrier properties.
Innovation Solution
The double container design includes features such as a rotating inner bag mechanism, alternating wall thickness, differential rotation resistance, overlapping temperature ranges for material softening, laser-printed information displays, and concave-convex shapes to facilitate easy separation and reduce pulling force, while maintaining 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 asymmetry by providing differential rotation resistance in different directions. The inner bag is designed to rotate easily in the separation direction (one direction) while having restricted rotation in the opposite direction, preventing twisting during cap attachment. This asymmetric rotational behavior resolves the contradiction between ease of separation and prevention of relative rotation.
2Stability of the object's composition
If the inner bag is tightly fitted to prevent rotation, then twisting is suppressed, but the inner bag cannot be easily pulled out from the outer shell
Solution Approach 1:
The inner bag structure implements asymmetric fitting characteristics: tight fitting in the radial direction to prevent rotation, while maintaining loose fitting in the axial direction to facilitate easy pull-out. This directional difference in fitting tightness resolves the contradiction between preventing rotation and enabling easy separation.
3Reliability
If an EVOH layer is provided in the inner bag to improve gas barrier properties, then content deterioration is suppressed, but the inner bag becomes hard and pullability deteriorates
Solution Approach 1:
The patent applies local quality by providing the EVOH layer only in specific regions where gas barrier properties are most needed (such as the body portion), while keeping the mouth part and separation-critical regions made of more flexible materials. This localized material distribution maintains gas barrier performance while preserving pullability.
Solution Approach 2:
The inner bag uses composite material construction, combining EVOH layer with flexible polymer layers. The composite structure integrates the gas barrier properties of EVOH with the flexibility and pullability of the polymer materials, resolving the contradiction between improved gas barrier and maintained pullability.
4Productivity
If the inner preform and outer preform are stacked for biaxial stretch blow molding, then double container is formed efficiently, but the inner bag shrinks during cooling causing gap formation
Solution Approach 1:
The patent applies parameter changes by optimizing the cooling rate and temperature gradient during the blow molding process. By controlling the cooling parameters, the inner bag's shrinkage is minimized while maintaining the efficient stacked molding process, thus resolving the contradiction between manufacturing efficiency and shape stability.
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, prevents content overflow, suppresses shrinkage, improves handleability, and maintains gas barrier properties without compromising pullability.
Implementation Method 1
an information transmission display is printed on the inner bag by irradiating a laser light
Implementation Method 2
a container body is formed by heating a preform configured by covering an inner preform with an outer preform and performing a biaxial stretch blow molding
Data Source
AI summary
Provided is a double container where an inner bag can be easily pulled out from an outer shell. According to the present invention, a double container comprising 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. And 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.