Blown Bottle Flange Interlock for Shrinkage Control
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Solution Overview
Problem
Injection blow molding of two-layer preforms often results in deformation due to post-molding shrinkage, leading to weak welding and potential leakage, especially when materials with low heat resistance or crystallinity are used.
Innovation Solution
A blown bottle design featuring a two-layer structure with an outer layer made of high rigidity material like PET and an inner layer of flexible material like LLDPE, where the inner and outer layers are molded separately and the flanges are configured with recesses and protrusions to enhance adhesiveness and prevent deformation, along with specific molding and welding techniques to maintain shape integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Shape
If injection blow molding is performed on a two-layer preform, then the desired bottle shape is achieved, but deformation occurs due to post-molding shrinkage
Solution Approach 1:
The patent applies preliminary action by forming a protrusion on one flange and a corresponding recess on the other flange before the blow molding process. This pre-formed interlocking structure prevents post-molding shrinkage deformation by mechanically constraining the flanges maintaining their relative positions even as the material cools and shrinks, ensuring the welding rib remains at the correct location for proper welding operation.
2Ease of manufacture
If a two-layer preform is blow molded, then the bottle structure is formed, but welding is unable to be performed as designed due to deformation
Solution Approach 1:
The protrusion and recess are formed in advance on the flanges before blow molding, creating a mechanical interlock that maintains the welding rib's positional accuracy. This preliminary structural feature ensures that even during cooling and shrinkage, the welding rib remains at the designed location, enabling proper welding to be performed without deformation-related failures.
3Adaptability or versatility
If materials with low heat resistance or low crystallinity are used, then flexibility is improved, but deformation occurs due to stress relaxation
Solution Approach 1:
By pre-forming the protrusion and recess interlocking structure on the flanges before blow molding, the patent creates a mechanical constraint that compensates for the inherent dimensional instability of materials with low heat resistance or crystallinity. This preliminary structural feature prevents stress relaxation from causing deformation, allowing flexible materials to maintain their shape integrity throughout the molding and cooling process.
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 solution effectively suppresses deformation and ensures strong, leak-proof welding by maintaining the shape integrity of the inner layer flange, even after molding, thereby improving the reliability of the blow-molded bottles.
Implementation Method 1
a heated preform is molded into a desired shape by longitudinally stretching the heated preform with a stretch rod and then laterally stretching and inflating the preform with pressurized air
Implementation Method 2
laterally stretching and inflating the preform with pressurized air
Implementation Method 3
deformation may occur in the molded article (post-molding shrinkage) due to stress relaxation of strain caused by the stretching
Data Source
Figure 1A~1C
Figure 2A~2C
Figure 3A~3B
AI summary
A blown bottle (13) includes at least two layers including an inner layer (16) and an outer layer (17), wherein the inner layer includes an inner layer flange (20), the outer layer (20) includes an outer layer flange, and wherein a protrusion is formed on either one of the inner layer flange or the outer layer flange, a recess is formed in the other, and the protrusion is fitted to the recess.