Method and apparatus for suppressing flow instabilities in an optical fiber draw system

Patent metadata

Field	Value
Publication number	US-11198636-B2
Application number	US-201916298532-A
Country	US
Kind code	B2
Filing date	Mar 11, 2019
Priority date	Mar 22, 2018
Publication date	Dec 14, 2021
Grant date	Dec 14, 2021

Abstract

A furnace system includes a muffle defining a furnace cavity. A lower heater is coupled to the muffle and is configured to create a hot zone within the furnace cavity having a temperature of about 1900° C. or greater. An upper muffle extension is positioned above the muffle and defines a handle cavity. A downfeed handle is positioned within the handle cavity such that a gap is defined between an outer surface of the downfeed handle and an inner surface of the upper muffle extension. An upper heater is thermally coupled to the upper muffle extension and configured to heat the gap. A gas screen is positioned in the upper muffle extension and is configured to inject a process gas into the handle cavity.

First claim

What is claimed is:

1. A furnace system, comprising:
a muffle defining a furnace cavity;
a lower heater coupled to the muffle and configured to create a hot zone within the furnace cavity having a temperature of about 1900° C. or greater;
an upper muffle extension positioned above the muffle and defining a handle cavity;
a downfeed handle positioned within the handle cavity such that a gap is defined between an outer surface of the downfeed handle and an inner surface of the upper muffle extension, the gap having a length as measured from the outer surface of the downfeed handle to the inner surface of the upper muffle extension of about 4 cm or less;
an upper heater thermally coupled to the upper muffle extension and configured to heat the gap to a temperature in a range from about 600° C. to about 1800° C.; and
a gas screen positioned in the upper muffle extension and configured to inject a process gas into the handle cavity.

2. The furnace system of claim 1 , wherein the process gas comprises about 10% or more by volume of argon.

3. The furnace system of claim 1 , wherein the process gas comprises about 10% or more by volume of nitrogen.

4. The furnace system of claim 1 , wherein:
the downfeed handle further comprises a boule, and wherein the boule is configured to support an optical fiber preform.

5. The furnace system of claim 4 , further comprising a shroud between the upper muffle extension and the optical fiber preform.

6. The furnace system of claim 1 , wherein the upper heater is configured to heat the gap to a temperature in a range of about 700° C. to about 1500° C.

7. The furnace system of claim 1 , wherein the length of the gap is about 2 cm or less.

8. The furnace system of claim 1 , wherein the upper heater is thermally coupled at an entrance of the upper muffle extension.

9. A furnace system, comprising:
a muffle defining a furnace cavity;
an upper muffle extension positioned above the muffle;
a gas screen positioned in the upper muffle extension and configured to inject a process gas;
a downfeed handle positioned within the upper muffle extension such that a gap is defined between an outer surface of the downfeed handle and an inner surface of the upper muffle extension, wherein the gap has a length as measured from the downfeed handle to the upper muffle extension of about 4 cm or less, wherein the downfeed handle is configured to support an optical fiber preform; and
an upper heater thermally coupled to the upper muffle extension and configured to heat the gap to a temperature of about 800° C. or greater.

10. The furnace system of claim 9 , wherein at least one of the muffle and the upper muffle extension comprises carbon.

11. The furnace system of claim 9 , wherein the length of the gap is about 3 cm or less as measured from the outer surface of the downfeed handle to the inner surface of the upper muffle extension.

12. The furnace system of claim 9 , wherein the length of the gap is about 2.5 cm or less as measured from the outer surface of the downfeed handle to the inner surface of the upper muffle extension.

13. The furnace system of claim 9 , wherein the length of the gap is about 2 cm or less as measured from the outer surface of the downfeed handle to the inner surface of the upper muffle extension.

14. The furnace system of claim 9 , wherein the process gas comprises an inert gas.

15. The furnace system of claim 14 , wherein the process gas comprises at least one of nitrogen and argon.

Assignees

• Corning Inc

Inventors

• Anderson Erling Richard
• Hoffmann Tammy M
• Jewell John Michael
• Kladias Nikolaos Pantelis
• Moore Robert Clark

Classifications

• C03B37/029 Primary

  Furnaces therefor · CPC title

• C03B37/0253

  Controlling or regulating (for glass fibre manufacture in general C03B37/07) · CPC title

• C03B2205/62

  Heating means for drawing · CPC title

• C03B2205/60

  Optical fibre draw furnaces · CPC title

• C03B2205/61

  Recovering, recycling or purifying the inert gas, e.g. helium · CPC title