Method and apparatus for producing a tube of glass

Patent metadata

Field	Value
Publication number	US-9957185-B2
Application number	US-201615140031-A
Country	US
Kind code	B2
Filing date	Apr 27, 2016
Priority date	Apr 28, 2015
Publication date	May 1, 2018
Grant date	May 1, 2018

Abstract

A method and apparatus are provided for producing a tube of glass by zonewise heating and softening of a hollow cylinder by a movable heating zone while rotating about its rotation axis. The glass tube is continuously formed by radial expansion of the softened region under action of centrifugal force and/or internal overpressure applied in the hollow-cylinder bore. The method and apparatus make it possible to deform the hollow cylinder in a single or a small number of forming steps into a glass tube having a larger outer diameter and high dimensional accuracy by determining a circumferential position at which the wall thickness is comparatively small, and during heating and softening of the rotating hollow cylinder a coolant is dispensed from a coolant source onto the deformation zone only when or predominantly when the circumferential position having the comparatively small wall thickness passes the coolant source.

First claim

We claim:

1. A method for producing a tube of glass comprising the following method steps:
(a) providing a hollow cylinder of the glass having a bore defined by a wall, a wall thickness, and an initial outer wall diameter D 1 ;
(b) heating and softening the hollow cylinder in a zonewise manner while the hollow cylinder is rotating about a rotation axis of the hollow cylinder and a heating zone is moved axially relative to the rotation axis;
(c) forming a deformation zone by radial expansion of a softened area of the hollow cylinder under action of at least one of centrifugal force and internal overpressure applied in the hollow cylinder bore; and
(d) continuously deforming the hollow cylinder to a tube having a second outer diameter D 2 which is greater than initial diameter D 1 ,
wherein step (a) includes a step of determining a circumferential position at which the wall thickness is minimal around a circumference of the hollow cylinder, and
wherein during heating and softening of the rotating hollow cylinder, a coolant is dispensed from a coolant source onto the deformation zone only when or predominantly when the circumferential position having the minimal wall thickness passes the coolant source.

2. The method according to claim 1 , wherein a liquid is used as the coolant.

3. The method according to claim 2 , wherein the liquid is sprayed or splashed onto the deformation zone.

4. The method according to claim 2 , wherein the liquid comprises water.

5. The method according to claim 2 , wherein the liquid is changed in amount during a cycle of the hollow-cylinder rotation.

6. The method according to claim 5 , wherein the liquid amount during each rotation of the hollow cylinder about its longitudinal axis is increased exactly once and is decreased exactly once.

7. The method according to claim 1 , wherein a circular arc around the deformation zone in which the coolant is operative is smaller than 30 angular degrees.

8. The method according to claim 1 , wherein the internal overpressure is set to less than 20 mbar.

9. The method according to claim 1 , wherein the produced tube has an outer diameter D 2 which is greater than the initial diameter D 1 by at least 40 mm.

10. The method according to claim 1 , further comprising a step of determining a temperature profile around a circumference of the deformation zone.

11. The method according to claim 1 , wherein the internal overpressure is set to less than 10 mbar.

12. The method according to claim 1 , wherein the outer diameter D 2 of the produced tube is greater than the initial diameter D 1 by at least 70 mm.

13. The method according to claim 1 , wherein the outer diameter D 2 of the produced tube is greater than the initial diameter D 1 by at least 100 mm.

Assignees

• Heraeus Quarzglas

Inventors

• Gromann Boris
• Söhn Matthias
• Blumenau Alexander

Classifications

• C03B23/08 Primary

  to exact dimensions, e.g. calibrating · CPC title

• C03B23/043

  Heating devices specially adapted for re-forming tubes or rods in general, e.g. burners · CPC title

• C03B23/053

  by centrifuging ({C03B23/094} , C03B37/04 takes precedence) · CPC title

• C03B23/045 Primary

  Tools or apparatus specially adapted for re-forming tubes or rods in general, e.g. glass lathes, chucks (C03B23/043 takes precedence) · CPC title

• C03B23/07

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