Plastic Preform Blow Molding With Pressure-Based Air Recycling
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Solution Overview
Problem
Existing stretch blow molding machines require user input for intermediate blow-off pressures, leading to inefficient compressed air recycling and increased energy consumption due to suboptimal valve opening times and neglecting air extraction characteristics during the pressure build-up phase.
Innovation Solution
The method optimizes compressed air recycling by determining valve opening times and recycling start times based on pressure levels and machine parameters, using a control system to minimize pressure differences and synchronize air flow between pressure reservoirs and containers, thereby enhancing energy efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Ease of operation
If user input is required for intermediate blow-off pressures, then the system can be operated with manual control, but the compressed air recycling efficiency deteriorates due to suboptimal valve opening times
Solution Approach 1:
The control system continuously monitors the actual pressure in pressure reservoirs and compares it with target pressure values. Based on this feedback, the system automatically adjusts valve opening times and recycling start times to optimize compressed air recycling efficiency, eliminating the need for manual pressure input while maximizing energy recovery.
Solution Approach 2:
The system determines valve opening times and recycling start times autonomously based on measured pressure values and pre-stored target values. The control device automatically calculates optimal parameters without requiring operator intervention, enabling the system to self-optimize compressed air recycling while maintaining ease of operation through automatic control.
2Quantity of substance
If valve opening times are extended to achieve complete pressure equalization, then more air mass is recycled, but the discharge pressure remains far above the lowest possible discharge pressure
Solution Approach 1:
The control system dynamically adjusts valve opening times based on real-time pressure measurements and process stage. During different phases of the blow molding cycle, the valve opening duration is optimized to balance air mass recycling with discharge pressure reduction, rather than using fixed extended opening times.
Solution Approach 2:
The control device determines optimal valve opening times in advance based on pre-stored target pressure values and current process conditions. By calculating the required valve opening duration before actual recycling begins, the system prepares optimal parameters that achieve both sufficient air mass recovery and acceptable discharge pressure levels.
3Stability of the object's composition
If recycling start times depend on unloading time characteristics, then the system can be synchronized with machine cycle, but the recycling potential is reduced when reservoir pressure is at its highest
Solution Approach 1:
The control system continuously monitors actual pressure values in pressure reservoirs and uses this feedback to determine optimal recycling start times. Instead of relying solely on fixed unloading time characteristics, the system adjusts recycling timing based on real-time pressure conditions, enabling synchronization with the machine cycle while maximizing recycling potential when pressure conditions are favorable.
4Device complexity
If the characteristics of air extraction during pressure build-up are not considered, then the control system is simpler, but the recycling potential is left unused
Solution Approach 1:
The control system maintains continuous monitoring of pressure conditions throughout the entire blow molding cycle, including the pressure build-up phase. By continuously tracking pressure evolution and air extraction characteristics during all phases, the system identifies recycling opportunities that would otherwise be missed, maximizing energy recovery without significantly increasing control complexity.
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 reduces compressed air consumption and improves energy efficiency by optimizing air recycling, allowing for smaller compressor sizing and lower operational costs.
Implementation Method 1
the plastic preform is subjected to a first blowing pressure via a flow connection between the first pressure reservoir and the plastic preform and is subjected to the second blowing pressure via a flow connection between the second pressure reservoir and the plastic preform
Implementation Method 2
The valve opening time during the recycling phase determines the air mass that is recycled. This assumes a pressure gradient between the container and the pressure reservoir of the individual stages.
Data Source
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AI summary
A method for forming plastic preforms (10) into plastic containers (15), wherein a plastic preform (10) is expanded into the plastic container by being supplied with a flowable medium, wherein the flowable medium is stored in a first pressure reservoir under a first pressure and in a second pressure reservoir under a second pressure which is higher than the first pressure, and wherein the plastic preform is supplied with a first blowing pressure via a flow connection between the first pressure reservoir and the plastic preform, and is supplied with a second blowing pressure via a flow connection between the second pressure reservoir and the plastic preform, and wherein at least temporarily flowable medium is returned to the first pressure reservoir, wherein first values characteristic for the supply of the plastic preforms (10) with the flowable medium (P1, Pi, P2, t1P1, tPi,tP2) are specified in such a way that, taking into account the first values, second values (t2Pi, t2P+ ) are determined which are characteristic for a time or period of time of returning the flowing medium to the first pressure reservoir.