Apparatus and method for producing float glass having reduced defect density

Abstract

A float glass chamber and related methods comprising a hot section having an atmosphere in at least the lower plenum comprises less than 3 percent hydrogen based on volume and a cold section, wherein the boundary line between the hot section and the cold section is where the temperature of the glass falls below a threshold temperature

What is claimed is:  
     
         1 . A float glass chamber comprising: 
 a hot section having an atmosphere in at least the lower plenum comprises less than 3 percent hydrogen based on volume; and    a cold section, wherein the boundary line between the hot section and the cold section is where the temperature of the glass falls below a threshold temperature.    
     
     
         2 . A float chamber according to  claim 1  wherein the threshold temperature of the chamber is 1600° F.  
     
     
         3 . A float chamber according to  claim 1  wherein the threshold temperature of the float chamber is 1800° F.  
     
     
         4 . A float chamber according to  claim 1  wherein the threshold temperature of the float chamber is 2100° F.  
     
     
         5 . A float chamber according to  claim 1  wherein the atmosphere in at least the lower plenum of the cold section comprises up to 10 percent of hydrogen based on volume.  
     
     
         6 . A float chamber comprising: 
 a hot section having an atmosphere in at least the lower plenum comprises less than 3 percent hydrogen based on volume; and    a cold section, wherein the boundary line between the hot section and the cold section is where the temperature of the glass falls below a threshold temperature of greater than 1600° F.    
     
     
         7 . A float chamber according to  claim 6  wherein the atmosphere in at least the lower plenum of the cold section comprises up to 10 percent of hydrogen based on volume.  
     
     
         8 . A method for making float glass with reduced defect density comprising: 
 a. melting a glass composition to form a glass melt; and    b. pouring the glass melt in a float chamber having a hot section and an cold section, the boundary line between the hot section and the cold section is where the temperature of the glass falls below a threshold temperature, wherein the hot section has an atmosphere in at least the lower plenum comprises less than 3 percent hydrogen based on volume    
     
     
         9 . A method according to  claim 8  wherein the threshold temperature of the float chamber is 1600° F.  
     
     
         10 . A method according to  claim 8  wherein the threshold temperature of the float chamber is 1800° F.  
     
     
         11 . A method according to  claim 8  wherein the threshold temperature of the float chamber is 2100° F.  
     
     
         12 . A method according to  claim 8  wherein the atmosphere in at least the lower plenum of the cold section comprises up to 10 percent of hydrogen based on volume  
     
     
         13 . A method according to  claim 8  wherein the glass melt has a water content equal to or greater than 0.035 weight percent based on the total weight percent of the composition.  
     
     
         14 . A method according to  claim 8  wherein the float glass produced comprises at least one piece of glass in a laminated product.  
     
     
         15 . A method according to  claim 14  wherein the laminated product is a windshield.  
     
     
         16 . A method for making float glass with reduced defect density comprising: 
 a. melting a glass composition to form a glass melt; and    b. pouring the glass melt into a float chamber having a hot section and an cold section, the boundary line between the hot section and the cold section is where the temperature of the glass falls below a threshold temperature;    c. pumping a gas mixture comprising less than 3% hydrogen based on volume into at least the lower plenum of the hot section.    
     
     
         17 . A method according to  claim 16  wherein the pumping comprises pumping a gas mixture comprising less than 1% hydrogen based on volume into at least the lower plenum of the hot section.  
     
     
         18 . A method according to  claim 16  wherein the glass composition comprises: 
 from 65 to 75 weight percent SiO 2 ;  
 from 10 to 20 weight percent Na 2 O;  
 from 5 to 15 weight percent CaO;  
 from 0 to 5 weight percent MgO;  
 from 0 to 5 weight percent Al 2 O 3 ;  
 from 0 to 5 weight percent K2O; and  
 from 0 to 2 weight percent Fe2O 3 ,  
 with weight percents being based on the total weight of the glass composition.  
 
     
     
         19 . A method according to  claim 16  wherein the melting occurs in an oxy-fuel furnace.