Apparatuses For Controlling The Temperature Of Glass Forming Materials In Forehearths

Abstract

Forehearths that create a substantially homogeneous temperature to molten glass forming materials across the end position are provided. A gas cavity, a weir, a refractory block, or a heating element in the forehearth may be utilized to reduce a temperature gradient of molten glass forming materials across the end position. Reducing the temperature difference of the molten glass forming material across the end position permits for improved chemical and physical properties of the glass fibers and the end products formed from the glass fibers. In addition, a reduction in the temperature gradient across the end position produces a more homogenous glass fiber and glass product. Further, a reduction in the shear break rate occurs when the molten glass forming material has a temperature that is substantially the same across the end position, which results in a reduction in the breakage of glass fibers and an increase in manufacturing efficiency.

1 - 20 . (canceled) 
     
     
         21 . A forehearth for conveying a molten glass forming material to a glass forming apparatus, said forehearth comprising:
 a flow block extending a length of said forehearth and defining a flow channel over which said molten glass forming material flows toward an end wall, said flow block further defining a plurality of openings downward through said flow channel operable to deliver said molten glass forming material to at least one bushing of said glass forming apparatus, wherein one of the openings closest to said end wall is an end opening;   a roof covering at least a portion of said flow block and enclosing a gas combustion chamber between said flow block and said roof, said gas combustion chamber containing combustion gases to heat said molten glass forming material; and   a glass contact wall positioned in said flow channel downstream from said end opening and having an upstream face contacting said molten glass forming material to prevent the passage of molten glass forming material and an opposed downstream face facing but spaced from said end wall such that said glass contact wall is located between said end wall and said end opening;   wherein a gas cavity is formed between the downstream face of said glass contact wall and said end wall, said gas cavity being devoid of molten glass material and in flow communication with said combustion chamber for the flow of said combustion gases thereto, and said gas cavity being in direct contact with said glass contact wall and said flow block to transfer heat from said combustion gases in said gas cavity to said molten glass material proximate said end opening via said glass contact wall and said flow block.   
     
     
         22 . The forehearth of  claim 21 , wherein said combustion gases located in said gas cavity radiate heat through said glass contact wall and said flow block to increase the temperature of said molten glass forming material at a downstream portion of said end opening and reduce a temperature gradient of said molten glass forming material across said end opening. 
     
     
         23 . The forehearth of  claim 21 , wherein said gas cavity has a dimension of about 1 inch to about 12 inches extending from said glass contact wall to said end wall. 
     
     
         24 . The forehearth of  claim 23 , wherein said gas cavity has a depth-extending from a top surface of said glass contact wall to a top surface of said flow block. 
     
     
         25 . The forehearth of  claim 21 , wherein said gas cavity extends at least to a downstream end of a bushing block positioned beneath said end opening of the flow block. 
     
     
         26 . The forehearth of  claim 21 , further comprising gas burners adapted to inject flames into said gas combustion chamber, and wherein no additional energy source is adapted to supply energy to said gas cavity other than said gas burners adapted to inject flames into said gas combustion chamber. 
     
     
         27 . A forehearth for conveying a molten glass forming material to a glass forming apparatus, said forehearth comprising:
 a flow block over which said molten glass forming material flows toward an end opening, said flow block defining a plurality of openings therethrough for the passage of said molten glass forming material from said forehearth to at least one bushing of said glass forming apparatus, said plurality of openings including a first opening and said end opening which is located downstream of said first opening and adjacent an end wall of said forehearth; and   a refractory block supported on said flow block over said end opening,   said refractory block having a thickness and a hole therethrough in register with said end opening in the flow block for the passage of said molten glass forming material through said hole and said end opening;   wherein said refractory block extends upstream from said end opening to alter the flow of said molten glass forming material over said refractory block so that said molten glass forming material at said end opening has a depth less than a depth of said molten glass forming material at said first opening by an amount equal to the thickness of said refractory block.   
     
     
         28 . The forehearth of  claim 27 , wherein said molten glass forming material has an upper surface and a bottom surface and said refractory block forces said molten glass forming material at said bottom surface towards said upper surface. 
     
     
         29 . The forehearth of  claim 28 , wherein said upstream portion of said refractory block is submerged in said molten glass forming material and said upstream portion of said refractory block allows passage of said upper surface of said molten glass forming material over said upstream portion of said refractory block. 
     
     
         30 . The forehearth of  claim 27 , wherein the shallower depth of said molten glass forming material on said refractory block permits heat from combustion gases to penetrate said molten glass forming material over said refractory block and increase the temperature of said molten glass forming material at said end opening and reduce a temperature gradient of said molten glass forming material between said first opening and said end opening. 
     
     
         31 . A forehearth for conveying a molten glass forming material to a glass forming apparatus, said forehearth comprising:
 a gas combustion chamber including a flow block over which said molten glass forming material flows to a plurality of openings through said flow block, said plurality of openings including an end opening and being operable to deliver said molten glass forming material to a bushing of said glass forming apparatus;   a glass contact wall positioned downstream from said end opening;   an end wall positioned downstream and adjacent to said glass contact wall; and   a heating element contiguous with said end wall, said flow block, and at least one of said bushing and a bushing block to decrease thermal losses in said molten glass forming material proximate said end opening via heat transfer through said end wall, said flow block, and said bushing to said molten glass forming material,   wherein said bushing is located in a bushing block below said flow block.   
     
     
         32 . The forehearth of  claim 31 , wherein said heating element achieves a temperature of at least 2100° F. 
     
     
         33 . The forehearth of  claim 32 , wherein said heating element is selected from the group consisting of molybdenum electrodes, nickel chrome wire, silicon carbide, a platinum wire, a torch, a pipe having therein hot combustible gases and glow bars. 
     
     
         34 . The forehearth of  claim 31 , wherein said heating element increases the temperature of said molten glass forming material positioned adjacent to said glass contact wall and reduces a temperature gradient of said molten glass forming material across said end opening. 
     
     
         35 . The forehearth of  claim 31 , wherein said heating element is distinct from any heating device that heats a bushing located beneath said flow block.