Vertical crucible pulling method for producing a glass body having a high silicic-acid component

Patent metadata

Field	Value
Publication number	US-9790116-B2
Application number	US-201414569615-A
Country	US
Kind code	B2
Filing date	Dec 12, 2014
Priority date	Dec 18, 2013
Publication date	Oct 17, 2017
Grant date	Oct 17, 2017

Abstract

The present invention refers to a method for producing a glass body with high silicic-acid content by drawing a softened glass mass from an elongated, substantially cylindrical crucible in that SiO 2 granules are supplied from above into the crucible, the SiO 2 granules are heated to a softening temperature, so that the softened glass mass which comprises a melt surface is formed, the softened glass mass is drawn off via a bottom opening of the crucible so as to form a glass strand, and the glass strand is cut to length to obtain the glass body, wherein due to the supply of the SiO 2 granules a bulk heap is formed that covers the melt surface in part while leaving a melt edge, and wherein the melt surface is optically detected. To improve the fusion behavior of the granules and to suppress or altogether prevent the formation of a sinter crust, it is suggested according to the invention that during the optical detection of the melt surface the width of at least a sub-section of the melt edge is determined consecutively and is set to a value within a target width range through the supply rate of the SiO 2 granules.

First claim

The invention claimed is:

1. A method for producing a glass body with high silicic-acid content, said method comprising:
supplying SiO 2 granules from above into an elongated, substantially cylindrical crucible,
heating the SiO 2 granules to a softening temperature, so that a softened glass mass comprising a melt surface is formed,
drawing off the softened glass mass via a bottom opening of the crucible so as to form a glass strand, and
cutting the glass strand to a length to obtain the glass body,
wherein the supplying of the SiO 2 granules causes a bulk heap to be formed that partly covers the melt surface while leaving a melt edge not covered by said bulk heap, and
the method further comprising
optically detecting the melt surface,
wherein during the optical detecting of the melt surface a width of at least a sub-section of the melt edge is determined consecutively and is set to a value within a target width range by setting a supply rate of the SiO 2 granules; and
wherein the width of the melt edge is set to a value within the target width range by a nominal supply rate of SiO 2 granules based on a throughput of the drawn-off glass mass, and wherein the nominal supply rate is changed by not more than 10%.

2. The method according to claim 1 , wherein the supply rate of the SiO 2 granules is set such that the melt edge formed has a width between 0.5 cm and 4 cm.

3. The method according to claim 1 , wherein the optical detecting of the melt surface comprises a temperature measurement.

4. The method according to claim 3 , wherein the temperature measurement is carried out using at least one pyrometer that is directed to a position on an edge of the bulk heap.

5. The method according to claim 1 , wherein the optical detecting of the melt surface comprises an imaging of the melt edge with an at least one camera.

6. The method according to claim 1 , wherein the optical detecting of the melt surface comprising an imaging detection combined with a temperature measurement, and wherein a camera is used with a pyrometer.

7. The method according to claim 6 , wherein the camera is directed to a position on an edge of the bulk heap.

8. The method according claim 1 , wherein the SiO 2 granules are supplied via an individual filling tube terminating centrally above the bulk heap, and a distance ranging from 5 cm to 20 cm is set between the end of the filling tube and the bulk heap.

9. The method according to claim 1 , wherein the supply rate of the SiO 2 granules is adjusted using vibrations.

10. The method according to claim 1 , wherein the SiO 2 granules are supplied continuously.

11. The method according to claim 1 , wherein the supply rate of the SiO 2 granules is set such that a surrounding melt edge is formed with a width between 1 cm and 2 cm.

12. The method according claim 1 , wherein the SiO 2 granules are supplied via an individual filling tube terminating centrally above the bulk heap, and a distance ranging from 5 cm to 20 cm is set between the end of the filling tube and the bulk heap.

13. The method according to claim 1 , wherein the nominal supply rate of the SiO 2 granules is adjusted using vibrations.

14. The method according to claim 1 , wherein the SiO 2 granules are supplied continuously at the varying nominal supply rate.

15. A method for producing a glass body with high silicic-acid content, said method comprising:
supplying SiO 2 granules from above into a substantially cylindrical crucible,
heating the SiO 2 granules to a softening temperature, so that a softened glass mass comprising a melt surface is formed,
drawing off the softened glass mass via a bottom opening of the crucible so as to form a glass strand, and
cutting the glass strand to a length to obtain the glass body,
wherein the supplying of the SiO 2 granules causes a bulk heap to be formed that partly covers the melt surface while leaving a melt edge not covered by said bulk heap, and
the method further comprising
optically detecting the melt surface so as to repeatedly determine a width of at least a sub-section of the melt edge of the melt surface; and
controlling a nominal supply rate of the SiO 2 granules based on a throughput of the glass mass drawn off as the strand so as to maintain the determined width of the melt edge within a target width range.

16. The method according to claim 15 , wherein the nominal supply rate varies within a range of plus or minus 10% of a supply rate value.

17. The method according to claim 15 , wherein the nominal supply rate of the SiO 2 granules is set such that the melt edge formed has a width between 0.5 cm and 4 cm.

18. The method according to claim 15 , wherein the supply rate of the SiO 2 granules is set such that a surrounding melt edge is formed with a width between 1 cm and 2 cm.

19. The method according to claim 15 , wherein the optical detecting of the melt surface comprises a temperature measurement carried out using at least one pyrometer that is directed to a position on an edge of the bulk heap.

20. The method according to claim 15 , wherein the optical detecting of the melt surface comprises an imaging of the melt edge with an at least one camera directed to a position on an edge of the bulk heap.

21. The method according to claim 15 , wherein the optical detecting of the melt surface comprising an imaging detection combined with a temperature measurement, and wherein a camera is used with a pyrometer.

Assignees

• Heraeus Quarzglas

Inventors

• Buckenauer Thomas
• Pohl Remo
• Stenger Robert
• Böhler Alexander

Classifications

• C03B5/24

  Automatically regulating the melting process · CPC title

• C03B3/00 Primary

  Charging the melting furnaces · CPC title

• C03B5/0336

  Shaft furnaces (C03B5/0338 takes precedence) · CPC title

• C03B17/04

  Forming tubes or rods by drawing from stationary or rotating tools or from forming nozzles · CPC title