Rotating Susceptor Induction Furnace for Symmetric Glass Draw Heating
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Solution Overview
Problem
Existing optical fiber drawing furnaces face challenges in achieving circumferential temperature symmetry, leading to defects such as high-frequency diameter variations, ovalities, and radial irregularities in drawn tubes due to asymmetrical temperature profiles caused by factors like coil helicity, misalignment, and susceptor thickness, which are critical for maintaining precise geometries in hollow fibers.
Innovation Solution
A drawing furnace with a rotational drive system that rotates the susceptor and insulating material at a controlled frequency, combined with an A/C induction coil, to ensure even heat distribution and circumferential symmetry during the drawing process.
Engineering Contradictions & Design Principles
Engineering Contradiction Analysis
1Manufacturing precision
If a stationary susceptor is used in the induction furnace, then the heating apparatus is simple and easy to operate, but the circumferential temperature profile becomes asymmetric causing defects like ovality, siding, and high-frequency diameter variations
Solution Approach 1:
The susceptor is made rotatable instead of stationary, allowing it to rotate about its longitudinal axis during induction heating. This dynamic configuration enables the susceptor to experience uniform circumferential heating by periodically changing its orientation relative to the induction coil, thereby achieving symmetric temperature distribution and eliminating geometric defects in the drawn glass elements.
2Manufacturing precision
If the susceptor is rotated during heating, then uniform temperature distribution is achieved eliminating defects, but the device complexity increases due to additional rotational drive system
Solution Approach 1:
The susceptor is equipped with a rotational drive system that enables it to rotate about its longitudinal axis during the heating process. This dynamic motion ensures that all circumferential regions of the susceptor are exposed uniformly to the induction heating field, achieving symmetric temperature distribution that prevents dimensional instabilities and geometric defects in the drawn glass elements.
3Power
If resistance heater is used for tube draw, then sufficient power is available, but the heating uniformity and circumferential symmetry are difficult to maintain
Solution Approach 1:
The patent replaces the conventional resistance heating system with an induction heating system. In this system, an induction coil generates a time-varying magnetic field that induces eddy currents within the conductive susceptor, which in turn generates heat internally through resistive heating. This substitution provides both sufficient heating power and superior circumferential temperature symmetry, as the induced currents are generated uniformly throughout the susceptor volume.
Solution Approach 2:
The susceptor is made rotatable during induction heating, allowing it to dynamically adjust its orientation relative to the induction coil. This rotation ensures that the magnetic field penetrates all circumferential regions of the susceptor uniformly, maintaining symmetric temperature distribution while providing sufficient heating power for tube and preform drawing applications.
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 significantly reduces or eliminates defects in drawn optical fibers by ensuring uniform temperature distribution, meeting tight tolerance requirements for ovality, siding, and CSA variation, enhancing the yield of precise tubing geometries.
Implementation Method 1
an A/C induction coil capable of accepting a level of electrical current and producing an oscillating electronic signal oscillating at a frequency
Implementation Method 2
a cylindrical susceptor capable of producing a level of heat output
Implementation Method 3
a rotational drive system operably connected to the bottom annular plate by an annular rotation gear system, wherein when the rotational drive system is engaged with the annular rotation gear system such that the bottom annular plate rotates along with at least one of the cylindrical susceptor
Data Source
AI summary
A drawing furnace for drawing a glass element includes: a furnace body having an upper end and a lower end. The furnace body includes a top annular plate, an A/C induction coil capable of accepting electrical current and producing an oscillating electronic signal, a cylindrical susceptor capable of producing heat output, a cylindrical quartz beaker, an insulating material disposed between the susceptor and the beaker, and a bottom annular plate housing and supporting at least one of the susceptor, the beaker, and the insulating material. wherein the furnace body comprises a central longitudinal axis; A rotational drive system operably connected to the bottom annular plate by an annular rotation gear system rotates the bottom annular plate along with the susceptor, beaker, and/or insulating material at a frequency between 0.01 to 10 Hz. The electrical current and oscillation frequency determine the heat output of the susceptor.