Fixed-Composition Glass-Ceramic Hob for Variable Optical Properties
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Solution Overview
Problem
Existing glass-ceramic plates for cooking appliances require significant composition adjustments to vary optical properties, leading to increased production costs due to transition times and stock management needs, limiting the range of aesthetic and functional options.
Innovation Solution
A lithium aluminosilicate glass-ceramic plate with a specific chemical composition comprising SnO2, V2O5, Fe2O3, and Cr2O3, balanced to achieve a wide range of optical properties without altering the mother glass composition, allowing for varied light transmission and thermal expansion.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Adaptability or versatility
If the composition of glass-ceramic plates is adjusted to vary optical properties, then the range of aesthetic and functional options is improved, but production costs increase due to transition times and stock management needs
Solution Approach 1:
The patent applies parameter changes by modifying the ceramization process parameters (temperature, time, atmosphere) rather than changing the glass composition. The glass batch contains fixed amounts of colorants (Fe2O3: 0.3-0.5%, V2O5: 0.05-0.2%, SnO2: 0.05-0.1%), and the desired optical variations are achieved through controlled ceramization cycles that transform these fixed compositional parameters into variable optical properties. This resolves the contradiction by decoupling composition changes from property variations.
Solution Approach 2:
The patent implements preliminary action by pre-loading the glass batch with all necessary colorants and compositional elements during the glass melting stage. The glass composition is formulated in advance with specific ranges of iron oxide, vanadium oxide, and tin oxide that will respond to subsequent ceramization treatments. This preliminary preparation eliminates the need for composition adjustments during production, reducing manufacturing complexity and costs while maintaining versatility.
2Adaptability or versatility
If the composition of glass-ceramic plates is adjusted to vary optical properties, then the range of aesthetic and functional options is improved, but production complexity increases due to stock management needs
Solution Approach 1:
The patent applies universality by creating a single, multi-functional glass batch composition that can produce multiple optical outcomes through process variation alone. The glass formulation contains a balanced combination of colorants (Fe2O3, V2O5, SnO2) that respond differently to ceramization conditions, allowing one composition to serve multiple aesthetic and functional purposes. This universal base composition eliminates the need for multiple specialized stockpiles and simplifies production planning.
Solution Approach 2:
The patent uses parameter changes in the ceramization process (temperature profiles, holding times, cooling rates) to generate optical property variations from a fixed composition. By changing process parameters rather than compositional parameters, the production system maintains simplicity in material handling and stock management while achieving versatility in final product properties. The ceramization cycle becomes the primary tool for differentiation.
3Illumination intensity
If vanadium oxide content is increased to achieve desired optical properties, then light transmission control is improved, but the glass darkens excessively during ceramization
Solution Approach 1:
The patent introduces tin oxide (SnO2) as an intermediary substance that mediates between vanadium oxide and the final optical properties. SnO2 acts as a buffer that controls the redox reactions during ceramization, preventing excessive darkening while allowing V2O5 to provide the desired light transmission control. This intermediary element enables the use of V2O5 at optimized levels without the harmful side effect of excessive darkening.
Solution Approach 2:
The patent applies parameter changes by carefully controlling the oxidation-reduction conditions during ceramization to manage the optical properties. The ceramization process parameters (temperature, atmosphere, time) are optimized to control the valence states of vanadium and iron, thereby controlling light transmission without excessive darkening. This parametric control allows precise tuning of optical properties while avoiding the harmful effects of high V2O5 content.
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
Enables a wider range of optical properties in glass-ceramic plates, reducing production costs by maintaining consistent composition, while meeting functional and aesthetic demands.
Implementation Method 1
V2O5 is responsible for absorption, mainly below 700 nm and it is possible, in its presence, to maintain a sufficiently high transmission at 950 nm and in the infrared
Implementation Method 2
This heat treatment generates crystals of beta-quartz or beta-spodumene structure, which have a negative coefficient of thermal expansion, within the plate. The glass-ceramic material is therefore no longer glass: it is made up of crystals linked by a residual glassy phase; and has a coefficient of thermal expansion close to zero
Data Source
AI summary
The invention relates to a lithium aluminosilicate-type glass-ceramic hob characterised in that it has a chemical composition comprising the following constituents, within the limits defined below expressed in weight percent: SnO2: 0.05 to < 0.35%; V2O5: 0.05 to 0.40%; Fe2O3: >0.30 to 0.40%; Cr2O3: 0.005 to 0.040%.