Electric heating – Heating devices – With power supply and voltage or current regulation or...
Reexamination Certificate
1999-08-20
2001-05-15
Paschall, Mark (Department: 3742)
Electric heating
Heating devices
With power supply and voltage or current regulation or...
C219S506000, C219S494000, C374S137000, C374S124000, C065S384000
Reexamination Certificate
active
06232583
ABSTRACT:
BACKGROUND OF THE INVENTION
1. Technical Field
This invention relates to a fiber temperature sensor and processor device for an optical fiber draw furnace; and more particularly to high temperature measurement of optical fiber in excess of 1000 degrees Celsius during a fiber draw process.
2. Description of Related Art
There are no practical ways to measure the high temperature of optical fiber in excess of 500 degrees Celsius during the fiber draw process. There is a real need in the industry to do so. All the known ways that measure the low temperature of optical fiber significantly below 1000 degrees Celsius during the fiber draw process have limited temperature range, inaccuracy and unreliability, require precise fiber alignment and very close proximity to fiber making a measurement difficult, and are impractical for high temperature measurement. See U.S. Pat. No. 4,576,485.
As described in an abstract, Japanese Patent No. 60-163,377 discloses an optical fiber drawing apparatus having an electronic circuit to take out a temperature signal from an intensity component of an infrared ray signal detected from a heated optical fiber and an outer diameter signal from its period component. The temperature of the fiber appears to be determined from the intensity of an infrared signal using a scanning beam technique. For example, the optical fiber is scanned as shown in FIG. 3(
a
), the pulse height determines the optical fiber temperature as shown in FIG. 3(
b
), and the pulse width determines the outer diameter of the optical fiber as shown in FIG. 3(
c
). The signal from the detector appears to be used to control the extrusion rate of the fiber and the speed of a drum 11. The optical fiber drawing apparatus does not use thermographic imaging (i.e. a temperature distribution image) of the optical fiber. The optical fiber drawing apparatus does not provide thermographic sensing or profile processing of the optical fiber.
SUMMARY OF THE INVENTION
The basic idea of the present invention is to use infrared (IR) energy to measure optical fiber temperature during the fiber draw process.
The present invention provides a fiber draw furnace for drawing a fiber from a preform comprising a thermographic sensor in combination with a thermographic profiling processor.
The thermographic sensor responds to infrared energy radiating from the fiber, for providing a thermographic sensor signal containing information about the infrared energy radiating from the fiber.
The thermographic profiling processor responds to the thermographic sensor signal, for providing a thermographic profiling processor signal containing information about a thermographic profile of variations in the heat emitted by the fiber.
The fiber is typically quartz glass; and the thermographic sensor includes an infrared filter for filtering out infrared energy outside a range of 8-12 microns radiating from the quartz fiber, and also includes a lens and infrared sensor for focusing and sensing infrared energy inside a range of 8-12 microns radiating from the quartz fiber.
The quartz fiber typically has a temperature in a range of 500 to 2,000 degrees Celsius. The thermographic sensor signal contains information about the infrared energy radiating from the quartz fiber in a temperature range of 500 to 2,000 degrees Celsius.
The thermographic profile includes variations in the heat emitted across the width or along the length of the fiber.
The thermographic profiling processor may include microprocessor circuitry having a combination of a microprocessor, a random access memory, a read only memory, an input/output device, and an address, control and data bus for connecting the combination.
The thermographic profiling processor signal contains information either to control the temperature of the fiber draw furnace, the speed of the fiber being drawn from the preform, or both.
The fiber draw furnace has a furnace temperature controller that responds to the thermographic profiling processor signal, for providing a furnace temperature control signal to control the temperature of the fiber draw furnace.
The fiber draw furnace also has a capstan and spool speed controller that responds to the thermographic profiling processor signal, for providing a capstan and spool speed controller signal to control the speed of a capstan and spool drawing and winding the fiber from the preform.
In operation, the fiber draw furnace uses high sensitivity infrared (IR) thermographic technology (including commercial measurement systems) to optically scan the natural infrared radiation associated with the fiber. The temperature signal attained through optical scanning of infrared radiation is converted into a thermographic image of the optical fiber (i.e. a temperature distribution image). The signal/image is then converted into a temperature reading. Use of filters (specific wavelengths) and cooling of the sensor detector may be necessary to obtain an accurate temperature reading using this technique for glass fiber at high or low temperatures.
One advantage of the present invention is that infrared (IR) measurement of optical fiber is accurate and practical for production use. Infrared energy can be sensed and measured by the temperature of the fiber during draw anywhere along the visible fiber path, and does not require precise fiber alignment while a distance of several inches can be maintained from the fiber path.
Another advantage of the present invention is that the thermographic sensor and profiling processor device can provide a valuable research tool to collect data related to a drawn fiber that allows one to study and determine physical and optical properties about the drawn fiber, including cooling rates and temperature profiles, that have otherwise to date only been determined via modelling or theoretically.
REFERENCES:
patent: 4576485 (1986-03-01), Lambert
patent: 5086220 (1992-02-01), Berthlold et al.
patent: 5180226 (1993-01-01), Moslehi
patent: 5561294 (1996-10-01), Iddan
patent: 5730527 (1998-03-01), Takayama
patent: 60-16377 (1985-04-01), None
patent: 61-86442 (1986-05-01), None
patent: 3-37129 (1991-02-01), None
patent: 4193731 (1992-07-01), None
patent: 5186239 (1993-07-01), None
patent: 6-72737 (1994-03-01), None
patent: 9915470 (1999-04-01), None
“Patent Abstract of Japan,” M. Ito et al., “Measurement of Temperature of Preform Material for Spinning Fiber”, Application No. 4-4062, Jul. 27, 1993.
“Patent Abstract of Japan,” K. Hirano, “Method of Controlling Heating Furnace of Spinning Machine”, Application No. 4-248606, Mar/ 15, 1994.
“Patent Abstract of Japan,” No. J6 1086-442-A, Hitachi Cable KK, “Manufacturing of parent material for optical fibre-using bath temperature detector to control burner giving improved constancy of temperatire”.
“Patent Abstract of Japan,” No. J8 5016-377-B, Nippon Telegraph & Telephone, “Optical fibre drawing appts.-produces optical fibre by drawing of a preform rod”.
“Patent Abstract of Japan,” J0 3037-129-A, Asahi Optical KK, “Production of optical glass fibre with uniform diameter, comprises spinning multi-fibre from neck down part of preform in heating furnace”.
“Patent Abstract of Japan,” N. Mitomi et al, “Production of Optical Fiber Base Material”, Application No. 2-321635 Jul.13, 1992.
“Patent Abstract of Japan,” H. kenichi, No. JP 06 072737 A, Fujikura Ltd., “Method for Controlling Heating Furnace of Spinning Machine”, 15 Mar. 1994.
“Patent Abstract of Japan, ” K. Takehiro, No. JP 63 195139, Hitachi Cable Ltd., “Apparatus for Drawing Glass Rod”, 12 Aug. 1988.
Alcatel
Paschall Mark
Ware Fressola Van der Sluys & Adolphson LLP
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