Methods for controlling the thickness wedge in a glass ribbon

• US 10,233,109 B2
• Filed: 11/16/2016
• Issued: 03/19/2019
• Est. Priority Date: 09/22/2014
• Status: Active Grant

• Current Assignee: Corning Incorporated
• Original Assignee: Corning Incorporated
• Inventors: Ahrens, Jeffrey Howard
• Primary Examiner(s): Franklin, Jodi C
• Application Number:
  US15/353,138
• Publication Number:
  US 20170066675A1
• Time in Patent Office: 853 Days
• CPC Class Codes: C03B 17/064 by the overflow downdraw fusion process; Isopipes therefor
• CPC Class Codes: G01B 21/08 for measuring thickness
• CPC Class Codes: G05B 1/00 Comparing elements, i.e. elements for effecting comparison directly or indirectly between a desired value and existing or anticipated values
• CPC Class Codes: G05D 23/1917 using digital means

Abstract

A method for controlling wedge variation in a glass ribbon includes flowing molten glass over converging sides of a forming vessel, drawing a glass ribbon from a root of the forming vessel, measuring the wedge variation over at least a portion of the width of the glass ribbon, adjusting a tilt of the forming vessel and a temperature near a weir of the forming vessel based on the measured wedge variation to decrease the wedge variation over the width of the glass ribbon, and re-measuring the wedge variation over the portion of the width of the glass ribbon.

Claims

1. A fusion draw apparatus comprising:

a forming vessel having a first end and a second end defining a length of the forming vessel there between, and a trough positioned in an upper surface of the forming vessel;

a tilt mechanism configured to change a position of the first end of the forming vessel relative to the second end of the forming vessel;

at least one heating mechanism configured to heat to an area near a weir of the forming vessel; and

an automatic thickness control system comprising a thickness gauge positioned in a bottom of the draw apparatus and a controller comprising a processor and memory storing a computer readable and executable instruction set, which when executed by the processor;

receives a wedge variation calculation from the thickness gauge;

determines, based on the received wedge variation calculation, a high frequency component of the wedge variation and a low frequency component of the wedge variation by identifying peaks in a Fourier transform of the wedge variation signal wherein low frequency refers to periods greater than a first predetermined number of hours and high frequency refers to periods less than a second predetermined number of hours, wherein the second predetermined number of hours is less than the first predetermined number of hours, and a difference between the first and second predetermined number of hours is greater than or equal to two hours;

calculates a tilt setpoint to reduce the high frequency component of the wedge variation;

calculates a temperature setpoint to reduce the low frequency component of the wedge variation;

provides the tilt setpoint to the tilt mechanism; and

provides the temperature setpoint to the at least one heating mechanism.

2. The fusion draw apparatus of claim 1, wherein the automatic thickness control system adjusts a degree of tilt of the forming vessel based on the tilt setpoint.

3. The fusion draw apparatus of claim 1, wherein the automatic thickness control system adjusts an amount of heat provided to the area at the weir of the forming vessel based on the temperature setpoint.

4. The fusion draw apparatus of claim 1, further comprising a cooling mechanism positioned near the weir, wherein the automatic thickness control system causes the area at the weir of the forming vessel to be actively cooled based on the temperature setpoint.

5. The fusion draw apparatus of claim 1, wherein the automatic thickness control system calculates the tilt setpoint to minimize the high frequency component of the wedge variation.

6. The fusion draw apparatus of claim 1, wherein the automatic thickness control system calculates the temperature setpoint to minimize the low frequency component of the wedge variation.

7. The fusion draw apparatus of claim 1, wherein the automatic thickness control system calculates the tilt setpoint independent of the low frequency component of the wedge variation.

8. The fusion draw apparatus of claim 1, wherein the automatic thickness control system calculates the temperature setpoint independent of the high frequency component of the wedge variation.