Roll Forming High Refractive Index Glass Sheets
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Solution Overview
Problem
The existing methods for manufacturing high refractive index glass for augmented reality systems are costly and time-consuming, and fusion manufacturing processes are incompatible due to low liquidus viscosity, leading to issues with thickness variation and warp in the glass sheets.
Innovation Solution
The process involves continuously roll forming a ribbon of high refractive index glass, reducing horizontal temperature variability, controlling cooling rates, and extracting heat from rollers to produce glass sheets with minimal thickness variation and warp, using techniques like distributive feed devices, heat loss reduction elements, and radiative cooling.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Productivity
If continuously roll forming is used to produce glass sheets, then manufacturing cost and time are reduced, but the glass ribbon fractures or develops thickness variation and warp
Solution Approach 1:
The patent applies parameter changes by controlling the temperature profile of the glass ribbon during roll forming. Specifically, it reduces horizontal temperature variability and controls the vertical cooling rate through zones above and below the roll gap, adjusting these parameters to prevent fracture and minimize thickness variation while maintaining continuous production efficiency
Solution Approach 2:
The patent replaces traditional mechanical post-processing methods (such as sawing from boules, lapping, or reheating) with a controlled thermal field approach. By using thermal zones to manage temperature distribution during continuous roll forming, the system achieves thickness uniformity without the need for subsequent mechanical operations that would increase cost and time
2Manufacturing precision
If horizontal temperature variability is reduced, then thickness variation and warp are minimized, but cooling rate control becomes more complex
Solution Approach 1:
The patent segments the temperature control into distinct zones: a first zone above the roll gap that reduces horizontal temperature variability, and a second zone below the roll gap that controls vertical cooling rate. This segmentation allows each zone to be optimized independently for its specific function, managing complexity through modular thermal control regions
3Manufacturing precision
If heat is extracted from rollers, then outward expansion is reduced, but heat extraction system complexity increases
Solution Approach 1:
The patent extracts heat from the rollers through cooling systems integrated into the roll structure. This heat extraction prevents excessive outward expansion of the rollers during operation, which would otherwise imprint thickness variation and warp onto the glass ribbon, thereby maintaining thickness uniformity without requiring complex active adjustment mechanisms
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 method reduces the cost and time of producing high-quality glass sheets with minimal thickness variation and warp, enabling their use in augmented reality systems without the limitations of traditional methods.
Implementation Method 1
extracting heat from one or both of opposing rollers that roll form the molten glass into the ribbon of molten glass
Implementation Method 2
one or more of (i) reducing the rate of temperature decrease of the ribbon of glass vertically before the ribbon of glass cools to the glass transition temperature and (ii) increasing the rate of temperature decrease of the ribbon of glass vertically after the ribbon of glass cools to the glass transition temperature
Implementation Method 3
facing heat loss reduction elements (such as insulative substrates, heat producing elements, or combinations thereof) at the central portion of the ribbon of glass but not the lateral edges
Implementation Method 4
The present disclosure widens the width of the stream of molten glass delivered to the gap by utilizing a distributive feed device to deliver the stream of molten glass
Implementation Method 5
The present disclosure increases the height of the puddle of molten glass within the gap between the forming rollers by utilizing lateral dams above the rollers to limit lateral spread of the puddle of molten glass
Data Source
AI summary
A method of forming a glass sheet comprises: (a) forming a ribbon of glass from molten glass with a pair of forming rollers; (b) reducing horizontal temperature variability of the ribbon of glass to be 10° C. or less across 80 percent of an entire width of the ribbon of glass before the ribbon of glass cools to a glass transition temperature; (c) controlling a cooling rate of the ribbon of glass while the ribbon of glass moves vertically downward within a setting zone such that the ribbon of glass has a first average cooling rate before the ribbon of glass cools to the glass transition temperature and a second average cooling rate after the ribbon of glass cools to the glass transition temperature, the first average cooling rate being less than the second average cooling rate; and (d) separating a glass sheet from the ribbon of glass.