Overmolded Container Inner Bottle Pressure Control
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Solution Overview
Problem
Existing methods for forming overmolded containers risk deforming or damaging the inner bottle due to pressure and heat from molten resin during the injection molding process, especially in cylindrical shapes, and complicate the manufacturing process, potentially contaminating contents and deteriorating decorations.
Innovation Solution
A method and apparatus that use a columnar rod with vent paths to circulate pressurized gas within the inner bottle, controlling pressure and temperature to prevent deformation and ensure even resin coverage, while maintaining the inner bottle's shape and decoration integrity.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If molten resin is injected to form the outer body, then the overmolded container is formed with integrated outer and inner bottle, but the inner bottle deforms or is damaged by the pressure and heat of the molten resin
Solution Approach 1:
The inner bottle is pre-cooled to a temperature lower than the glass transition temperature of the resin before injection molding. This preliminary cooling action prevents the inner bottle from deforming under the heat and pressure of the molten resin during the subsequent injection process, thereby maintaining both the integrity and shape accuracy of the inner bottle.
Solution Approach 2:
A support structure is placed inside the inner bottle before injection molding to provide mechanical support and distribute the pressure from the molten resin. This beforehand cushioning prevents localized deformation and damage to the inner bottle, especially at vulnerable areas like corner portions, while still allowing the outer body to form properly.
2Ease of manufacture
If the inner bottle is spherical, then the injection molding process causes no serious problems, but cylindrical inner bottles with decorations suffer from corner deformation and decoration damage due to pressure and heat concentration
Solution Approach 1:
Cooling and support measures are applied locally to corner portions and areas with decorations rather than uniformly across the entire inner bottle. This localized approach provides enhanced protection to vulnerable areas where heat and pressure concentrate, preventing deformation and decoration damage while maintaining ease of manufacture for the overall molding process.
Solution Approach 2:
A support structure acts as an intermediary between the molten resin and the inner bottle, particularly at corner portions and decorated areas. This intermediary distributes and absorbs the concentrated pressure and heat, preventing direct transmission to the inner bottle wall and thus avoiding corner deformation and decoration damage during injection molding.
3Manufacturing precision
If cooling is applied to the inner bottle, then deformation is prevented, but short shot may occur if there is an error in cooling portion or timing
Solution Approach 1:
The cooling system is equipped with feedback control that monitors the temperature and pressure conditions during injection molding. Based on this feedback, the cooling rate and timing are automatically adjusted to maintain the inner bottle at the optimal temperature range, preventing both deformation and short shot by ensuring proper resin flow and filling throughout the molding process.
Solution Approach 2:
The cooling system operates dynamically rather than statically, with cooling intensity and timing adjusted in real-time based on the injection progress and resin temperature. This dynamic control ensures that the inner bottle remains sufficiently cool to resist deformation while still allowing complete resin filling, avoiding short shot by coordinating cooling with the injection rate and pressure.
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
This approach prevents deformation of the inner bottle and ensures high-quality overmolded containers with uniform resin coverage, reducing manufacturing complexity and avoiding contamination or decoration damage.
Implementation Method 1
circulating a pressurized gas into and out of a hollow space of the inner bottle
Implementation Method 2
circulating a pressurized gas into and out of a hollow space of the inner bottle while the molten resin is injected to the mold
Data Source
AI summary
A method for forming an overmolded container by covering a hollow inner bottle made of resin with an injection of a molten resin which forms an outer. The method comprises steps of setting the inner bottle in a mold with a space therebetween for forming the outer and circulating a pressurized gas into and out of a hollow space of the inner bottle through an upper opening thereof. The pressurized gas is supplied through a first path which opens toward an inner wall of the inner bottle and discharged out of the inner bottle through a second path. The pressurized gas supplied into and discharged out of the inner bottle is adjusted in pressure while the molten resin is being injected to the mold.