Ceramic Tube Heating Element for Dental Furnace
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Solution Overview
Problem
Current dental furnaces face challenges with heating elements that fail to maintain high temperatures required for sintering advanced ceramic materials like zirconium oxide, leading to contamination, flaking, and structural issues, and are limited by the need for complex configurations and frequent replacement.
Innovation Solution
A dental furnace with a heating element comprising a ceramic tube element made from high-purity oxide ceramics, such as aluminum oxide or zirconium oxide, with a heat-resistant and vacuum-tight design, and a connecting system using quartz glass and borosilicate glass with intermediate elements to manage thermal expansion, preventing contamination and structural damage.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Temperature
If molybdenum silicide heating elements are used to achieve temperatures up to 1650°C, then the temperature requirement is met, but flaking and contamination occur due to glass phase changes
Solution Approach 1:
The patent applies this principle by using a heating element made of molybdenum silicide with a controlled glass phase that is designed to be consumed during operation. The glass phase gradually dissolves to form MoO3, which is then removed through periodic firing cycles. This controlled consumption approach accepts the temporary harmful effect (coloration) as a trade-off for achieving the required high temperatures, with the understanding that the heating element will need replacement after a certain service life.
Solution Approach 2:
The patent implements this principle through the periodic firing process that removes MoO3 from the heating element surface. The glass phase is intentionally allowed to dissolve and form volatile MoO3, which is then discarded through the firing cycle. This continuous discarding of the degraded glass phase allows the heating element to maintain its functionality at high temperatures despite the ongoing material transformation.
2Temperature
If silicon carbide heating elements are used for high-temperature sintering, then temperature requirements are met, but the elements are prone to breaking and require complex installation
Solution Approach 1:
The patent applies this principle by using a composite heating element consisting of molybdenum silicide (a dense metal-ceramic material) combined with a controlled glass phase. This composite structure provides both the high-temperature capability of ceramic materials and the flexibility and fracture resistance characteristic of glass-ceramic composites. The glass phase acts as a binder that holds the molybdenum silicide particles together, creating a material that is both thermally stable and mechanically robust.
Solution Approach 2:
The patent implements this principle by carefully controlling the composition and properties of the glass phase in the composite material. By adjusting the glass phase content and composition, the patent optimizes the balance between thermal stability and mechanical flexibility, allowing the heating element to withstand thermal stresses and mechanical handling without fracturing.
3Adaptability or versatility
If heating elements are led through vacuum-tight openings for furnace evacuation, then vacuum capability is achieved, but forces and moments are exerted on the heating element causing damage
Solution Approach 1:
The patent applies this principle by using a flexible heating element design that can accommodate the mechanical constraints imposed by the vacuum-tight opening. The glass-ceramic composite structure provides sufficient flexibility to bend and adapt to the mounting geometry without fracturing, while still maintaining structural integrity under vacuum conditions. This flexibility allows the heating element to be routed through the vacuum opening without experiencing excessive stress concentrations.
4Ease of manufacture
If Kanthal heating wire in quartz glass is used for veneering ceramic sintering, then the process is simple, but temperatures are limited to max. 1200°C
Solution Approach 1:
The patent applies this principle by replacing the simple Kanthal wire in quartz glass construction with a sophisticated molybdenum silicide-based glass-ceramic composite. This advanced material combines the high-temperature stability of molybdenum silicide with the workability and flexibility of glass-ceramic matrices, enabling the heating element to operate at temperatures up to 1650°C while maintaining ease of installation and integration into the furnace structure.
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 solution allows for reliable high-temperature sintering of dental-ceramic compounds without contamination, reduced risk of structural damage, and extended heating element lifespan, enabling efficient processing of dental objects at temperatures up to 1600°C with improved vacuum tightness and reduced maintenance costs.
Implementation Method 1
a heating coil (34) arranged inside the tube element (30)
Implementation Method 2
a first thermal expansion compensation element (44) and a second thermal expansion compensation element (46)
Data Source
AI summary
Disclosed is a heating element for a dental furnace including a tube element for accommodating a heating coil inside the tube element. At least one closing element may be connected to at least one open end of the tube element, wherein electrical connectors may be led through the closing element and fused with the element. The tube element may be made from a ceramic material, such as oxide ceramics, that may be connected to the connector via a plurality of intermediate glasses/transition glasses and glass solder to compensate for different heat expansion coefficients such that up to 500° C. gas escaping from the tube element may not enter due to a thermal action, providing that operational safety of the heating element is ensured. Further, disclosed is a dental furnace including such a heating element.