Methods and systems for forming continuous glass sheets
A method for forming a continuous glass sheet from a tube of glass includes expanding and thinning the tube of glass by drawing the tube of glass over susceptor bearing comprising a porous sidewall defining an internal chamber. The diameter of the susceptor bearing may increase between a top portion and a bottom portion. The tube of glass may be maintained at a temperature above a softening point of the glass as the tube of glass is drawn over the susceptor bearing. The tube of glass is suspended over the susceptor bearing by blowing the tube of glass away from the susceptor bearing in a radial direction with a pressurized fluid supplied to the internal chamber and emitted from the porous sidewall as the tube of glass is drawn over the susceptor bearing. Thereafter, the tube of glass is cooled and sectioned to form a continuous glass sheet.
1. A method for forming a continuous glass sheet, the method comprising:
thinning and expanding a tube of glass by drawing the tube of glass over a susceptor bearing comprising a porous sidewall defining an internal chamber, wherein a diameter of the susceptor bearing increases between a top portion of the susceptor bearing and a bottom portion of the susceptor bearing and the tube of glass is maintained at a temperature above a softening point of the glass as the tube of glass is drawn over the susceptor bearing;
blowing the glass tube away from the susceptor bearing in a radially outward direction with a pressurized fluid supplied to the internal chamber and emitted from the porous sidewall as the tube is drawn over the susceptor bearing thereby suspending the tube of glass over the susceptor bearing;
cooling the tube of glass; and
sectioning the tube of glass to form a continuous glass sheet.
2. The method of claim 1 further comprising winding the continuous glass sheet onto a storage spool.
3. The method of claim 1 wherein the tube of glass is molten glass and the method further comprises cooling the tube of glass to the temperature above the softening point of the glass as the tube of glass is drawn over the susceptor bearing.
4. The method of claim 3 wherein the tube of glass is air cooled as the tube of glass is drawn over the susceptor bearing.
5. The method of claim 1 wherein the tube of glass is a solid glass preform and the method further comprises heating the tube of glass to the temperature above the softening point of the glass as the tube of glass is drawn over the susceptor bearing.
6. The method of claim 1 further comprising rotating the tube of glass relative to the susceptor bearing as the tube of glass is drawn over the susceptor bearing.
7. The method of claim 1 further comprising rotating the susceptor bearing relative to the tube of glass as the tube of glass is drawn over the susceptor bearing.
8. The method of claim 1 wherein the susceptor bearing comprises the top portion, an upper intermediate portion, a lower intermediate portion and the bottom portion, wherein:
the top portion is substantially cylindrical;
the upper intermediate portion is substantially conical;
the lower intermediate portion is substantially spherical; and
the bottom portion is substantially cylindrical.
9. The method of claim 1 wherein the temperature of the tube of glass is maintained at the temperature above the softening point of the glass with a heating system disposed around the susceptor bearing, and wherein the heating system cooperates with the pressurized fluid emitted from the susceptor bearing to maintain the temperature of the glass at the temperature above the softening point of the glass.
10. The method of claim 1 , wherein the tube of glass surrounds the porous sidewall of the susceptor bearing.
11. The method of claim 1 , wherein the diameter of the tube of glass adjacent the top portion of the susceptor bearing is smaller than the diameter of the tube of glass adjacent the bottom portion of the susceptor bearing.
12. The method of claim 1 , wherein the porous sidewall has a radial thickness that is non-uniform.
13. A system for forming a continuous glass sheet comprising a susceptor bearing, a heating system, a drawing mechanism and a cutting device, wherein:
the susceptor bearing comprises a porous sidewall defining an internal chamber for receiving a pressurized fluid, wherein a diameter of the susceptor bearing increases between a top portion of the susceptor bearing and a bottom portion of the susceptor bearing and the susceptor bearing is operable to emit the pressurized fluid through the porous sidewall such that, when a heated tube of glass is drawn over the susceptor bearing, the heated tube of glass is blown away from the susceptor bearing in a radially outward direction thereby suspending the tube of glass over the susceptor bearing;
the heating system surrounds the susceptor bearing and cooperates with the pressurized fluid emitted from the susceptor bearing to regulate a temperature of a tube of glass drawn over the susceptor bearing;
the drawing mechanism is disposed below the susceptor bearing and comprises at least one tractor wheel positioned to contact the tube of glass and draw the tube of glass over the susceptor bearing in a downward direction; and
the cutting device is positioned below the drawing mechanism and is operable to section the tube of glass into a continuous glass sheet.
14. The system of claim 13 further comprising a take-up mechanism for winding the continuous glass sheet onto a storage spool.
15. The system of claim 13 wherein the susceptor bearing comprises the top portion, an upper intermediate portion, a lower intermediate portion, and the bottom portion, wherein:
the top portion is substantially cylindrical;
the upper intermediate portion is substantially conical;
the lower intermediate portion is substantially spherical; and
the bottom portion is substantially cylindrical.
16. The system of claim 13 wherein the heating system is operable to provide at least two temperature zones along an axial length of the susceptor bearing.
17. The system of claim 13 wherein the susceptor bearing is operable to rotate with respect to the heating system.
18. The system of claim 13 wherein the at least one tractor wheel of the drawing mechanism comprises three pairs of opposed tractor wheels.
19. The system of claim 13 , wherein when the heated tube of glass is drawn over the susceptor bearing, it surrounds the porous sidewall.
20. The system of claim 13 , wherein the heating system comprises more than one induction coil, wherein each of the more than one induction coil is independently controlled.