Blow Molding Preform Thinning via Intermittent Air Pressure
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Solution Overview
Problem
The existing blow molding methods, such as hot and cold parison types, face challenges in achieving uniform thickness in hollow containers due to variations in preform thickness, leading to issues like handleability, rigidity, and aesthetics, and heat-resistant containers suffer from uneven temperature distribution and deformation when filled with high-temperature contents.
Innovation Solution
A blow molding method and device that incorporates a thinning step involving alternating blowing and exhausting steps to uniformly stretch and contract the preform, particularly focusing on the bottom part, to improve the uniformity of the hollow container's thickness and enhance heat resistance.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If conventional blow molding methods (hot or cold parison type) are used, then hollow containers can be produced efficiently, but the thickness of the container becomes uneven due to variations in preform thickness
Solution Approach 1:
The patent applies periodic action by repeatedly and intermittently applying air blow pressure to the preform multiple times before final blow molding. This periodic inflation and deflation process gradually thins the preform wall thickness uniformly, transforming the uneven thick preform into a uniformly thin-walled container that maintains both production efficiency and thickness precision
2Reliability
If heat set treatment is applied to improve heat resistance, then crystallization of resin is promoted, but uneven temperature distribution causes deformation when filled with high-temperature contents
Solution Approach 1:
The patent performs preliminary thinning of the preform wall thickness through repeated intermittent blowing before the final blow molding and heat set treatment. This preliminary action creates a more uniform thickness distribution that prevents localized overheating and deformation during subsequent high-temperature filling, maintaining both heat resistance and shape stability
3Manufacturing precision
If preform thickness is reduced to improve container uniformity, then thickness uniformity improves, but the preform becomes more difficult to handle and process
Solution Approach 1:
The patent segments the blow molding process into multiple distinct stages: initial preform formation, repeated intermittent thinning blows, and final blow molding. This segmentation allows the preform to maintain its original thickness and handling properties during transport and positioning, while achieving uniform thinning only during the controlled blowing stages
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 method effectively reduces the uneven thickness of hollow containers, particularly the bottom part, improving their rigidity, heat resistance, and preventing deformation when filled with high-temperature contents, while maintaining manufacturing efficiency suitable for mass production.
Implementation Method 1
the surface temperature of the preform is increased by the inner temperature
Implementation Method 2
repeatedly and intermittently applying an air blow pressure to the preform
Data Source
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AI summary
Provided is a blow-molding method in which primary blowing is performed on a resin preform 10 to form an intermediate molded product 30, which is then subjected to final blowing to form a hollow container 40 as a final molded product, wherein the step for performing the primary blowing and/or the step for performing the final blowing step comprise a wall-thinning step where a step for stretching primary molded articles 20a-20c or the preform 10, which are subject items, by a blowing process, and a step for deflating the respective stretched parts of the primary molded articles 20a-20c, which are the subject items, by letting out the air used for blowing, are successively repeated within a prescribed period of time.