Gas-Assisted Base Blow Off for Blow Molding
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Solution Overview
Problem
High-speed stretch blow molding operations face challenges in maintaining base clearance and integrity of bottles, particularly in non-hot fill applications, where conventional post-mold cooling methods are inadequate, leading to significant drops in base clearance and reduced Environmental Stress Crack Resistance (ESCR) and Thermal Stability.
Innovation Solution
A gas-assisted base blow off system that introduces pressurized gas, such as air, into the base blow mold before bottle evacuation, using multiple orifices to cool the bottle base, thereby eliminating the need for post-mold cooling and improving ESCR and Thermal Stability.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If high speed stretch blow molding operations are used to increase productivity, then manufacturing speed increases, but base clearance reduction and bottle integrity problems occur
Solution Approach 1:
The patent applies preliminary action by cooling the bottle base within the mold before evacuation using gas-assisted base blow off. This pre-cooling action prevents base clearance reduction that would otherwise occur during high-speed operations, allowing the bottle to maintain dimensional stability before being removed from the mold.
Solution Approach 2:
The patent uses gas (air or nitrogen) as an intermediary medium to transfer thermal energy from the bottle base to the surrounding environment. The gas flows through channels in the mold base, acting as a heat transfer medium that efficiently cools the bottle base without requiring direct contact with cooling surfaces, thus preventing base clearance reduction while maintaining high-speed production.
2Manufacturing precision
If conventional post-mold cooling methods are used to cool the bottle, then base clearance is maintained, but additional process steps and time are required
Solution Approach 1:
The patent merges the cooling function with the existing mold structure by integrating gas flow channels into the mold base. The cooling action is combined with the evacuation process, eliminating the need for separate post-mold cooling steps. The gas-assisted base blow off occurs during the normal mold operation cycle, thereby maintaining base clearance without adding time to the manufacturing process.
3Reliability
If the bottle is cooled sufficiently to maintain integrity during removal, then bottle quality is improved, but the cooling process becomes complex and difficult to control
Solution Approach 1:
The patent applies self-service by using the bottle's own thermal properties and the natural flow characteristics of gas to achieve cooling. The gas flows through channels in the mold base and naturally absorbs heat from the bottle base through thermal conduction and convection. This self-regulating process maintains bottle integrity without requiring complex control systems, as the cooling rate is determined by the gas flow rate and thermal properties of the materials involved.
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 gas-assisted base blow off method effectively maintains base clearance and enhances ESCR and Thermal Stability, allowing for sustainable high-speed manufacturing by cooling the bottle base within the mold, which is more efficient and cleaner compared to conventional methods.
Implementation Method 1
introducing pressurized gas through the two or more orifices in the blow mold base sufficient to cool the container base
Implementation Method 2
cool the container base prior to container evacuation
Data Source
Figure 1
Figure 2A~2B
AI summary
This disclosure provides a method of manufacturing a polymer container according to a blow molding or stretch blow molding process, in which the base of the blow mold has at least one orifice for pressurized gas to enter the blow mold through the base. Introducing pressurized gas through the orifice in the blow mold base provides cooling assistance within the gas mold, much earlier than the cooling using conventional methods, which can reduce or eliminate the need for any post mold cooling. This method has been found to be applicable to non-hot fill application bottle and container manufacture.