PET Bottle Headspace Pressure Control via Liquid Nitrogen Phase Change
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Solution Overview
Problem
Existing methods for maintaining internal pressure in beverage containers, particularly PET bottles, are prone to variability due to factors like temperature changes and volume fluctuations, leading to inconsistent pressures that can result in container bursting or contamination, and are limited to cylindrical geometries.
Innovation Solution
A method and device for filling and sealing thin-walled plastic containers that involves introducing an exchange medium, such as liquid nitrogen, into the headspace to displace air and set a predetermined internal pressure by adjusting the gaseous medium supply or discharge through openings in the container walls, allowing for precise control of internal pressure and adaptation to handling and storage conditions.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If liquid nitrogen is introduced into the headspace to displace air, then the container internal pressure increases, but the pressure becomes difficult to control and may cause container bursting
Solution Approach 1:
The patent introduces a multi-stage pressurization process where the container is pressurized in steps rather than all at once. The system monitors pressure continuously and adjusts the nitrogen flow rate dynamically, changing parameters like flow rate and pressure thresholds to achieve precise control. This resolves the contradiction by transforming a single uncontrolled pressure increase into a controlled multi-stage process.
Solution Approach 2:
The patent employs a feedback control system with pressure sensors that continuously monitor the container internal pressure and adjust the nitrogen supply accordingly. The control unit receives pressure signals and modulates the flow valve to maintain pressure within desired limits, preventing both under-pressurization and over-pressurization that could lead to bursting.
2Object-affected harmful factors
If the container internal pressure is increased to prevent contamination, then the sealing requirement increases, but thin-walled containers may deform or burst
Solution Approach 1:
The patent applies partial pressurization rather than extreme over-pressurization. By introducing nitrogen gradually and maintaining pressure within a specific range (slightly above atmospheric pressure), the system achieves contamination protection without subjecting thin-walled containers to excessive stresses that would cause deformation or bursting.
Solution Approach 2:
The patent pre-cools the container and filling material before introduction of liquid nitrogen, and establishes a controlled pressurization protocol that prevents sudden pressure spikes. This cushioning approach prepares the system to handle the phase change of nitrogen without causing thermal or mechanical shock to the thin-walled container structure.
3Reliability
If liquid nitrogen is used for headspace pressurization, then air displacement is effective, but volume fluctuations and temperature changes cause pressure instability
Solution Approach 1:
The patent implements continuous pressure monitoring with feedback control that automatically adjusts nitrogen flow to compensate for volume fluctuations and temperature changes. The control system detects pressure deviations caused by these variables and modulates the supply rate accordingly, maintaining stable internal pressure throughout the storage period.
Solution Approach 2:
The patent maintains continuous nitrogen flow adjustment rather than single-stage pressurization. The system continuously monitors pressure and adjusts the nitrogen supply rate to account for ongoing temperature changes and volume fluctuations, ensuring stable headspace protection throughout the storage period.
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 ensures consistent internal pressure, preventing container bursting and contamination, while accommodating various container geometries, ensuring safe transport and stackability, and maintaining pressure above ambient levels even after cooling.
Implementation Method 1
the enormous volume expansion of liquid nitrogen during its transition into the gas phase when it comes into contact with the filling material
Implementation Method 2
the enormous volume expansion of liquid nitrogen during its transition into the gas phase
Implementation Method 3
a predetermined container internal pressure is adjusted by supplying and/or discharging a gaseous medium
Data Source
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AI summary
The invention relates to a device and a method for filling and closing a thin-walled plastic container (11), in particular a PET bottle, wherein a plastic container is produced from a preform by a blow molding process, and the plastic container is filled with a flowable medium and in particular a liquid, and an exchange medium is introduced into the plastic container, whereby, with the formation of an increased internal pressure of the container, at least partial displacement of the previously contained medium takes place and the plastic container is at least partially closed, wherein in at least one section of a wall of the plastic container surrounding a headspace of the plastic container,at least one opening is provided in a wall of the container closure or between a wall of the plastic container and a wall of the container closure, and a predetermined internal pressure is set through this opening in the interior of the plastic container by supplying and/or removing a gaseous medium.