Wire Edge Directors for Stable Glass Ribbon Formation
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Solution Overview
Problem
Forming glasses with low liquidus viscosity using a typical fusion process is challenging due to edge instability, which can lead to edge destabilization, edge flow density issues, and lateral contraction, making it difficult to maintain stable ribbon width and flow.
Innovation Solution
The use of edge directors comprising one or more wires that are partially immersed in the molten glass flow, which can be easily replaced or adjusted, and are heated with electrical current to stabilize the glass ribbon edges.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Reliability
If the ribbon center viscosity is reduced to stay below the liquidus viscosity, then the glass ribbon can be formed successfully, but the viscosity at the ribbon edges is also reduced and edges become destabilized
Solution Approach 1:
The patent applies local quality by implementing edge directors specifically at the ribbon edges to provide localized stabilization. The edge directors are positioned only where needed (at the edges) rather than throughout the entire ribbon, allowing the center to maintain low viscosity for successful formation while the edges receive targeted support to prevent destabilization and lateral contraction.
2Manufacturing precision
If typical edge directors made from sheets of platinum or platinum alloy are used, then ribbon width can be maintained, but they are impossible to change during operation and require long downtime to repair damage
Solution Approach 1:
The edge director is segmented into a replaceable component that can be independently changed. The design allows the edge director element to be separated from the main forming body, enabling quick replacement of just the edge director component rather than the entire forming assembly, thus maintaining precision while minimizing downtime.
Solution Approach 2:
The edge director design incorporates dynamic replaceability, transitioning from a fixed, permanent component to one that can be dynamically changed during operation. This allows the system to adapt to different production needs and quickly recover from damage without extended停机 periods.
3Manufacturing precision
If typical edge directors are used, then ribbon width can be maintained, but they are challenging to heat and devitrification can form on the glass contact surfaces
Solution Approach 1:
The edge director design incorporates parameters that facilitate easier heating, such as geometry and material properties that improve thermal response. This allows the edge director to be heated more effectively to temperatures above the glass liquidus, preventing devitrification on the contact surfaces while maintaining its function of controlling ribbon width.
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 wire edge directors effectively maintain ribbon width and stabilize the flow of molten glass, reducing edge instability and lateral contraction, allowing for stable glass ribbon formation even at high flow rates.
Implementation Method 1
wires that are at least partially immersed in the flow of molten glass may be easily replaced in the case of damage or a process change requiring a different design. For example, the wire(s) may be incorporated into a housing or other fixture than can be withdrawn from the forming process, for example a cartridge design, so the wire portion of the edge director can be repaired or replaced.
Data Source
AI summary
A glass forming apparatus configured to form a molten glass ribbon is disclosed, the glass forming apparatus including an edge director assembly positioned to immerse at least a portion of a wire immersion tool in an edge portion of the molten glass ribbon to mitigate lateral contraction of the molten glass ribbon and improve stability of the edge portion. A method of forming a glass ribbon using the edge director is also disclosed.