Method and apparatus for heating glass panels

Abstract

Glass panels are heated in a heating oven while supported on rolls. The glass panels are heated form above and below with convection air or with a combination of convection air and radiation heat. The convection air is heated by electric resistance elements and/or a combustible gas. The convection air passes through heat exchangers disposed in the oven en route to the glass panels.

1 . A method for heating glass panels supported on rolls in a heating oven, comprising the steps of: 
 A) directing convection air to the glass panels from above and below the glass panels;    B) heating the convection air by a heat source; and    C) passing the convection air in heat exchange relationship with a heat accumulator disposed in the oven.    
   
   
       2 . The method according to  claim 1  wherein step B is performed by a heat source comprising an electric resistance element.  
   
   
       3 . The method according to  claim 1  wherein step B is performed by a heat source comprising a gas burner.  
   
   
       4 . The method according to  claim 1  wherein the heat accumulator is directly heated by the heat source.  
   
   
       5 . The method according to  claim 4  wherein the heat source comprises an electric resistance element.  
   
   
       6 . The method according to  claim 4  wherein the heat source comprises a gas burner.  
   
   
       7 . The method according to  claim 1  wherein convection air directed to the glass panels from above, flows through a first heat exchanger, and convection air directed to the glass panels from below flows through a separate heat exchanger.  
   
   
       8 . The method according to  claim 1  wherein during an initial stage of heating of a glass panel the convection air is at least partially heated by residual heat from the heat accumulator, wherein the heat source operates at a maximum power rate less than heating power required during the initial stage of heating the glass panel.  
   
   
       9 . The method according to  claim 1  wherein the power source operates at a substantially constant power.  
   
   
       10 . The method according to  claim 1  wherein step A further includes heating the glass panels by radiant heat.  
   
   
       11 . The method according to  claim 1  wherein step C comprises passing the convection air through a porous heat exchanger body.  
   
   
       12 . An oven for heating glass panels comprising: 
 a heating chamber;    rolls in the heating chamber for supporting glass panels;    air directing structure in the heating chamber for directing convection air against the glass panels from above and below the glass panels;    a heat source for heating the convection air; and    a heat accumulator disposed in the heating chamber and arranged wherein the convection air passes in heat-exchange relationship therewith.    
   
   
       13 . The oven according to  claim 12  wherein the heat source comprises an electric resistance element.  
   
   
       14 . The oven according to  claim 12  wherein the heat source comprises a gas burner.  
   
   
       15 . The oven according to  claim 12  wherein the heat source is arranged to directly heat the heat exchanger.  
   
   
       16 . The oven according to  claim 15  wherein the heat source comprises an electric resistance element.  
   
   
       17 . The oven according to  claim 15  wherein the heat source comprises a gas burner.  
   
   
       18 . The oven according to  claim 1  wherein a first heat accumulator heats convection air directed against the glass panels from above, and a separate heat accumulator heats convection air directed against the glass panels from below.  
   
   
       19 . The oven according to  claim 12  further including radiant heaters in the heating chamber for heating the glass panels by radiant heat.  
   
   
       20 . The oven according to  claim 12  wherein the heat accumulator comprises a porous body through which convection air flows.