Methods and apparatus for finishing edges of glass sheets

Abstract

A method for finishing an edge of a glass sheet comprises grinding the edge of the glass sheet with a grinding wheel. The glass sheet includes a first major surface, a second major surface substantially parallel to the first major surface, and the edge connecting the first and second major surfaces. The grinding produces a central edge portion and two chamfered edge portions connecting the central edge portion with the first and second major surfaces, respectively. The method further comprises polishing the central edge portion with at least one cup wheel rotated about a first axis substantially parallel with the first and second major surfaces of the glass sheet to polish the central edge portion, wherein an abrasive layer of the cup wheel comprises at least one of ferric oxide (Fe2O3), silicon carbide (SiC), and ceric oxide (CeO2).

1 . A method for finishing an edge of a glass sheet, comprising:
 grinding the edge of the glass sheet with a grinding wheel, the glass sheet including a first major surface, a second major surface substantially parallel with the first major surface, and the edge connecting the first and second major surfaces, the grinding producing a central edge portion and two chamfered edge portions connecting the central edge portion with the first and second major surfaces, respectively; and   polishing the central edge portion with a first cup wheel rotated about a first axis substantially parallel with the first and second major surfaces of the glass sheet to polish the central edge portion, wherein an abrasive layer of the first cup wheel comprises at least one of Fe 2 O 3 , SiC, and CeO 2 .   
     
     
         2 . The method of  claim 1 , wherein the abrasive layer comprises about 5% to about 15% of Fe 2 O 3  by volume. 
     
     
         3 . The method of  claim 1 , wherein the abrasive layer comprises about 15% to about 27% of SiC or CeO 2  by volume. 
     
     
         4 . The method of  claim 1 , wherein the abrasive layer further comprises diamond particles comprising a particle size from about 2 micrometers to about 4 micrometers. 
     
     
         5 . The method of  claim 1 , further comprising conveying at least one of the grinding wheel and the glass sheet such that a relative speed between the grinding wheel and the glass sheet is in a range from about 2 meters per minute to about 6 meters per minute. 
     
     
         6 . The method of  claim 1 , further comprising conveying at least one of the first cup wheel and the glass sheet such that a relative speed between the first cup wheel and the glass sheet is in a range from about 4 meters per minute to about 10 meters per minute. 
     
     
         7 . (canceled) 
     
     
         8 . The method of  claim 1 , wherein an average roughness Ra of the polished central edge portion is equal to or less than about 0.05 micrometers. 
     
     
         9 . The method of  claim 1 , wherein a surface of the polished central edge portion is within 0.1 degrees of perpendicularity relative to the first or second major surface. 
     
     
         10 . The method of  claim 1 , wherein a transmittance of light of the polished central edge portion is equal to or larger than about 98% over a wavelength range from about 380 nm to about 750 nm. 
     
     
         11 . The method of  claim 1 , further comprising performing intermediate polishing on the central edge portion with a second cup wheel after grinding the edge of the glass sheet, wherein the second cup wheel is rotated about a second axis substantially parallel with the first and second major surfaces, and wherein grits of the second cup wheel are larger than grits of the first cup wheel. 
     
     
         12 . The method of  claim 11 , further comprising conveying at least one of the second cup wheel and the glass sheet such that a relative speed between the second cup wheel and the glass sheet is in a range from about 4 meters per minute to about 10 meters per minute. 
     
     
         13 . The method of  claim 11 , wherein the second cup wheel comprises a plurality of slots distributed along an inner periphery of an abrasive surface of the second cup wheel. 
     
     
         14 . An apparatus for finishing an edge of a glass sheet, comprising:
 a grinding wheel for grinding the edge of the glass sheet, the glass sheet comprising a first major surface, a second major surface substantially parallel with the first major surface and the edge connecting the first and second major surfaces, the grinding wheel further comprising a circumferential groove with a profile configured to form a central edge portion substantially perpendicular to the first and second major surfaces and two chamfered edge portions connecting the central edge portion to the first and second major surfaces; and   a cup wheel for polishing the central edge portion, the cup wheel rotatable about a first axis substantially parallel with the first major surface and the second major surface, the cup wheel comprising an abrasive layer comprising at least one of Fe 2 O 3 , SiC, and CeO 2 .   
     
     
         15 . The apparatus of  claim 14 , wherein the abrasive layer comprises about 5% to about 15% of Fe 2 O 3  by volume. 
     
     
         16 . The apparatus of  claim 14 , wherein the abrasive layer comprises about 15% to about 27% of SiC or CeO 2  by volume. 
     
     
         17 . The apparatus of  claim 14 , further comprising a second cup wheel configured to polish the central edge portion, the second cup wheel supported and rotatable about a second axis substantially parallel with the first major surface and the second major surface, wherein grits of the first cup wheel are smaller than grits of the second cup wheel. 
     
     
         18 . The apparatus according to  claim 17 , wherein the second cup wheel comprises a plurality of slots distributed along an inner periphery of an abrasive surface of the second cup wheel. 
     
     
         19 . The apparatus according to  claim 17 , wherein the first cup wheel comprises 5000 mesh grits. 
     
     
         20 . The apparatus of  claim 14 , further comprising at least one conveyor coupled to either one of the first cup wheel and the glass sheet and configured to convey at least one of the first cup wheel and the glass sheet in a direction along a length of the edge of the glass sheet by a relative speed in a range from about 4 meters per minute to about 10 meters per minute. 
     
     
         21 . (canceled)