Divergent Cooling Element for Blown Film Stability
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Solution Overview
Problem
Existing thermoplastic blown film cooling systems face limitations in throughput rate, aerodynamic holding forces, stability, and film size range, often resulting in vibration, flutter, high noise levels, and reduced film quality.
Innovation Solution
A high-performance cooling system utilizing divergent cooling elements with a divergent cooling interface that expels cooling gas in opposing and parallel paths to the molten film tube, combined with controlled pressure enclosures and a flow buffer to maintain a predetermined pressure differential, enhancing stability and cooling efficiency.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Stability of the object's composition
If cooling gas is applied to flow along the surface of the molten film tube to create holding forces, then stability is improved, but vibration, flutter, and high noise levels occur
Solution Approach 1:
The cooling system divides the cooling gas flow into multiple zones with different characteristics: a first cooling gas flow along the upstream side creating holding forces, and a second cooling gas flow along the downstream side creating repelling forces. This local differentiation allows simultaneous achievement of stability and reduction of harmful vibrations and noise.
Solution Approach 2:
The system changes the parameters of cooling gas application by creating opposing flows with different directions and characteristics. The first cooling gas flow moves in one direction to provide holding forces, while the second cooling gas flow moves in the opposite direction to provide repelling forces, thereby controlling the molten film tube's stability while minimizing harmful effects.
2Temperature
If cooling gas is applied against the surface of the molten film tube to create repelling forces, then cooling efficiency is improved, but a separate means is required to stabilize the molten film tube
Solution Approach 1:
The system merges the cooling function and stabilization function into a single integrated cooling system. The same cooling gas flows serve dual purposes: providing cooling efficiency through repelling forces while simultaneously providing stabilization through holding forces, eliminating the need for separate stabilization means.
Solution Approach 2:
The cooling gas flows are designed to perform multiple functions simultaneously. The first cooling gas flow provides both cooling and holding forces, while the second cooling gas flow provides both cooling and repelling forces. This multi-functionality reduces device complexity by eliminating separate stabilization systems.
3Productivity
If the cooling element is extended upward to increase cooled surface area, then throughput rate is improved, but stability deteriorates due to greater unsupported surface area
Solution Approach 1:
The cooling element is designed with different cooling gas flow characteristics at different locations. The upstream side receives cooling gas flowing in one direction to provide holding forces and stability, while the downstream side receives cooling gas flowing in the opposite direction to provide repelling forces. This local differentiation allows extended cooling surface area without compromising stability.
Solution Approach 2:
The system uses opposing cooling gas flows to counterbalance each other. The holding forces from the first cooling gas flow counteract the instability caused by extended unsupported surface area, while the repelling forces from the second cooling gas flow maintain cooling efficiency. This counterbalancing allows greater throughput rate without stability loss.
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 proposed cooling system significantly increases throughput rate, maximizes aerodynamic holding forces, maintains stability with large unsupported regions, produces a wide range of film sizes, minimizes turbulence and noise, and is simple to control, resulting in improved film quality and process efficiency.
Implementation Method 1
Cooling systems are designed using well known Bernoulli and Coanda principles, and in many cases, apply the cooling gas to flow generally along the surface of the molten film tube to create holding forces on the molten film tube
Implementation Method 2
Cooling systems are designed using well known Bernoulli and Coanda principles, and in many cases, apply the cooling gas to flow generally along the surface of the molten film tube to create holding forces on the molten film tube, providing for both stability and cooling
Implementation Method 3
at least one enclosure including a cavity operable for receiving at least a portion of the cooling gas from the at least one cooling element to substantially maintain a predetermined pressure differential between an inside surface and an outside surface of the flow of the molten film tube
Data Source
AI summary
The present invention relates to an external cooling system for a molten film tube produced by a blown film tubular extrusion process, comprised of one or more enclosures with one or more respective cavities that directly receive a portion of cooling gas emanating from one or more associated cooling elements. Each enclosure includes a port containing a variable exhaust device and optional flow buffer, acting to maintain a pressure differential between the cavity and an adjacent inside volume of the molten film tube, adjustable to optimize molten film tube stability cooling element efficiency and spaced apart dimension between cooling elements. Additionally, at least one cooling element is provided, comprised of a divergent cooling element with a divergent cooling interface containing a cooling gas deflector spaced adjacent to the molten film tube and providing an expelled cooling gas.