Quartz glass tube and method of manufacturing the same

Patent metadata

Field	Value
Publication number	US-11919794-B2
Application number	US-202217706748-A
Country	US
Kind code	B2
Filing date	Mar 29, 2022
Priority date	Mar 29, 2021
Publication date	Mar 5, 2024
Grant date	Mar 5, 2024

Abstract

In a method of manufacturing a tube of quartz glass by molding a hollow cylinder having a wall thickness of at least 20 mm, the cylinder is continuously fed under rotation about a rotational axis into a heating zone at a relative feed rate VC, softened and radially expanded under the effect of a gas pressure. A tube strand is continuously formed and is withdrawn at a withdrawal rate VT. In order to mold thick-walled initial hollow cylinders of quartz glass into tubes with larger diameter, the gas pressure is used as an actuating variable of a diameter regulation for the tube outer diameter or for a geometrical correlated parameter thereof, and in a pressure build-up phase the gas pressure is gradually increased from a lower initial value to a higher final value, and that the following applies to the ratio of VC and VT:VT=VC±0.2·VC.

First claim

The invention claimed is:

1. A method of manufacturing a tube of quartz glass by molding a hollow cylinder having a hollow cylinder bore, an outer diameter C a , an inner diameter C i and a wall thickness which is at least 20 mm, by continuously feeding the hollow cylinder under rotation around a rotational axis into a heating zone at a relative feed rate V C , softening the hollow cylinder in areas in the heating zone, and radially expanding the softened area under the effect of a gas pressure applied in the hollow cylinder bore, and continuously molding a tube strand having an outer tube diameter T a , a tube inner diameter T i , and a tube wall thickness from the softened area and withdrawing the tube strand at a withdrawal speed V T ,
wherein the gas pressure is an actuating variable of a diameter regulation and/or a diameter control for the tube outer diameter or for a geometrical parameter correlated with the tube outer diameter, and in that in a pressure build-up phase the gas pressure is gradually increased from a lower initial value to a higher final value characterized in that the gas pressure in the pressure build-up phase is increased at least temporarily with a temporal ramp Δp for which 0.01 mbar/min<Δp<0.8 mbar/min, and in that the following applies to the ratio of V C and V T :V T =V C ±0.2·V C .

2. The method according to claim 1 , characterized in that the gradual increase of the gas pressure in the pressure build-up phase takes place independently of the diameter regulation or independently of the diameter control.

3. The method according to claim 1 , characterized in that a nominal diameter value for the tube outer diameter or for the tube inner diameter is assigned to the diameter regulation or control, and in that a nominal gas pressure is assigned to the nominal diameter value, and in that the lower initial value lies in the range from 10 to 30% of the nominal gas pressure, and the higher final value lies in the range from 90 to 100% of the nominal gas pressure.

4. The method according to claim 3 , characterized in that the nominal gas pressure is set in the range from 2 to 20 mbar.

5. The method according to claim 3 , characterized in that the nominal gas pressure is set in the range from 4 to 10 mbar.

6. The method according to claim 1 , characterized in that the pressure build-up phase has a duration of between 1 and 120 minutes.

7. The method according to claim 1 , characterized in that the pressure build-up phase has a duration of between 15 and 60 minutes.

8. The method according to claim 1 , characterized in that for the hollow cylinder and for the tube strand there applies:

150 mm < C a < 300 mm,

 30 mm < C i < 180 mm,

     40 mm < (C a -C i )/2) < 100 mm

300 mm < T a < 550 mm,

250 mm < T i < 450 mm,

    20 mm < (T a -T i )/2) < 60 mm.

9. The method according to claim 1 , characterized in that for the hollow cylinder and for the tube strand there applies:

  4 · C i < T i < 8 · C i ,

C a + 100 mm < T a <C a + 300 mm.

10. The method according to claim 1 , characterized in that the tube outer diameter T a lies in the range of 1.5 times to 2.2 times the hollow cylinder outer diameter C a .

11. The method according to claim 1 , characterized in that the initial hollow cylinder has a glass cross-sectional surface A C and the tube strand has a glass cross-sectional surface A T , wherein:
A T =A C ±0.15· A C .

12. The method according to claim 11 , characterized in that the glass cross-sectional surfaces A C and A T lie in the range of 250 to 1000 cm 2 .

13. The method according to claim 1 , characterized in that for the ratio of V C and V T there applies:
0.8· V C ≤V T ≤1.05· V C .

14. The method according to claim 1 , characterized in that V C is adjusted to result in a throughput of quartz glass mass of at least 30 kg/h but less than 45 kg/h.

15. The method according to claim 1 , characterized in that the gas pressure is increased during the entire pressure build-up phase with an average temporal ramp Δp m for which there applies:
0.01 mbar/min<Δ p m <0.5 mbar/min.

16. The method according to claim 1 , characterized in that the gas pressure in the pressure build-up phase is increased at least temporarily with the temporal ramp Δp for which there applies: 0.01 mbar/min<Δp<0.5 mbar/min.

17. The method according to claim 1 , characterized in that the gas pressure in the pressure build-up phase is increased at least temporarily with the temporal ramp Δp for which there applies: 0.01 mbar/min<Δp<0.2 mbar/min.

18. The method according to claim 1 , characterized in that the gas pressure is increased during the entire pressure build-up phase with an average temporal ramp Δp m for which there applies: 0.01 mbar/min<Δp m <0.1 mbar/min.

19. The method according to claim 1 , characterized in that the gas pressure is increased during the entire pressure build-up phase with an average temporal ramp Δp m for which there applies: 0.01 mbar/min<Δp m <0.06 mbar/min.

Assignees

• Heraeus Quarzglas

Inventors

• Söhn Matthias
• Gromann Boris
• Visnow Eduard

Classifications

• C03B11/16 Primary

  Gearing or controlling mechanisms specially adapted for glass presses · CPC title

• C03B11/127

  of hollow or semi-hollow articles or their moulds · CPC title

• C03B23/07 Primary

  by blowing, e.g. for making electric bulbs {(C03B23/097 takes precedence)} · CPC title

• C03B23/047

  by drawing ({C03B23/091} , C03B37/025 takes precedence) · CPC title

• C03B2215/40

  Product characteristics · CPC title