Double glazing

Abstract

A double glazing unit has a pair of glass sheets 1, 2, with a frit seal 3 therebetween, the frit seal being fused to both sheets and extending around the periphery of the unit. The frit seal is fused by irradiation with light 4 from a laser. Typically, the frit is of brown glass, whereby it readily absorbs heat on laser irradiation.

1 . A double glazing unit comprising two parallel sheets of glass peripherally sealed to each other, the seal being of fused glass frit.  
     
     
         2 . A double glazing unit according to  claim 1 , wherein the frit is of colored glass, whereby it absorbs heat on irradiation for sealing.  
     
     
         3 . A double glazing unit according to  claim 1 , wherein the unit comprises three or more parallel sheets of glass peripherally sealed to each other by fused glass frit.  
     
     
         4 . A double glazing unit according to  claim 1 , wherein the frit has substantially the same coefficient of thermal expansion as that of the glass to be sealed.  
     
     
         5 . A double glazing unit according to  claim 1 , wherein the glass of the frit has a softening point less than that of the glass to be sealed.  
     
     
         6 . A method of producing a double glazing unit comprising two parallel sheets of glass peripherally sealed to each other, consisting in the steps of: 
 applying the frit to one of the sheets of glass,    positioning the other sheet of glass over the first sheet on the frit and locally heating the frit to fusing temperature by traversing it with laser irradiation, whereby the two sheets of glass become peripherally sealed together.    
     
     
         7 . A method according to  claim 6 , wherein the sheets are preheated to close to the frit fusing temperature, whereby the energy supplied by the laser is only that required to raise the temperature of the frit locally to its fusing temperature from the preheat temperature.  
     
     
         8 . A method according to  claim 6 , wherein the degree of preheat of the glass is maintained below the temper firing temperature of the glass, whereby the surface compressive stresses induced to strengthen the glass on tempering are not relieved, at least in the bulk of the glass.  
     
     
         9 . A method according to  claim 6 , wherein the sealed unit is cooled in a controlled manner.  
     
     
         10 . A method according to  claim 6 , wherein the laser irradiation is carried out in a dry, inert atmosphere, whereby such an atmosphere is enclosed within the double glazing unit.  
     
     
         11 . A method according to  claim 6 , wherein the frit is preliminarily tape cast and positioned on the glass in continuous lengths.  
     
     
         12 . A method according to  claim 6 , wherein the frit is positioned by tape casting direct onto the first sheet of glass.  
     
     
         13 . A method according to  claim 6 , wherein the frit is positioned by screen printing onto the first sheet of glass.  
     
     
         14 . A method according to  claim 10 , wherein the frit is preliminarily heated to drive off its binder, prior to positioning of the other sheet of glass on it.  
     
     
         15 . A double glazing sealing machine comprising: 
 a frit application station for applying frit peripherally to a glass sheet to form one side of a double glazing unit;    an assembly station for assembling the double glazing unit from the two glass sheets on top of each other with the frit between them;    a preheating station for preheating the assembled pairs of sheets;    a laser irradiation station for fusing the frit to seal the sheets to each other; and    a cooling station for cooling the sealed units to room temperature.