Methods and apparatus for heat treating glass sheets

Abstract

Methods for heat treating glass sheets ( 13 ) are disclosed in which the sheets ( 13 ) are held in a vertical orientation in a treatment container ( 15 ) during the heat treatment. The container ( 15 ) includes a support system for the glass sheets ( 13 ) that comprises a bottom support ( 17 ), two side supports ( 19 a, 19 b ), and a top support ( 21 ). The sheets ( 13 ) are slid into the container ( 15 ) without contact between their side edges ( 23 a, 23 b ) and the side supports ( 19 a, 19 b ). The top support ( 21 ) is then slid onto the tops of the sheets ( 13 ) without contacting the sheets' top edges ( 25 ). In certain embodiments, flushing air which has been HEPA filtered and pre-heated is passed through the container ( 15 ) during the heat treatment. Apparatus for practicing the methods of the invention are also disclosed.

1 . A container for holding a plurality of glass sheets during a heat treatment comprising six walls which define the container's internal volume, wherein:
 (a) each of the six walls comprises one or more metal sheets which together form at least 80 percent of the wall's surface area; and   (b) each of the metal sheets has a thickness that is less than or equal to one millimeter.   
     
     
         2 . The container of  claim 1  wherein:
 (a) the container comprises a support system for holding the plurality of glass sheets in a vertical orientation during the heat treatment; 
 (b) the support system comprises a bottom support, two side supports, and a top support; 
 (c) the top support comprises shaped members which, during use of the container, contact the glass sheets only at locations inboard from the top edges of the sheets; 
 (d) the side supports comprise shaped members which, during use of the container, contact the glass sheets only at locations inboard from the side edges of the sheets; and 
 (e) the shaped members are composed of metal and have a thickness that is less than or equal to one millimeter. 
 
     
     
         3 . The container of  claim 2  wherein the metal sheets and the shaped members are composed of an alloy which does not substantially oxidize at 650° C. 
     
     
         4 . The container of  claim 1  comprising tubing for carrying a flushing gas, said tubing being mounted on the outer surface of at least one of the six walls. 
     
     
         5 . The container of  claim 4  wherein at least a part of the tubing has a pattern that increases the length of the tubing through which the flushing gas passes during use of the container. 
     
     
         6 . A support system for holding a plurality of glass sheets in a vertical orientation during a heat treatment comprising a bottom support, two side supports, and a top support wherein:
 (a) the top support comprises shaped members which, during use of the support system, contact the glass sheets only at locations inboard from the top edges of the sheets; and   (b) the side supports comprise shaped members which, during use of the support system, contact the glass sheets only at locations inboard from the side edges of the sheets.   
     
     
         7 . The support system of  claim 6  wherein the shaped members are composed of metal and have a thickness that is less than or equal to one millimeter. 
     
     
         8 . The support system of  claim 6  wherein the shaped members are composed of an alloy which does not substantially oxidize at 650° C.