GB1144911A - Improvements in or relating to the manufacture of hollow glassware - Google Patents

Abstract

1,144,911. Annealing glass articles. COMPAGNIE BELGO - LUXEMBOURGEOISE DUECOMMERCE EXTERIEUR. 11 May, 1966 [12 May, 1965], No. 20800/66. Heading C1M. A process for the heat treatment of hollow glassware comprises the steps of heating the glassware above the annealing point (i.e. in the range 500-600‹ C.), cooling the glassware to at least the transformation temperature, reheating the glass strongly to above the annealing point so as to heat strongly only the external layers of the glassware and temporarily inverse the temperature gradient through the glass wall and finally cooling the glassware to the transformation temperature at a rate sufficient to freeze in the glass a desired permanent residual stress. The glassware is any form of hollowware. Formed glass articles are fed continuously in a single line into a lehr 1. They enter a first section 5 which is heated to a temperature in the range 500‹ to 600‹ C. by any conventional means. The thermally homogeneous ware then passes into a second section 6 wherein its temperature is reduced into the range 300‹ to 400‹ C. To assist in cooling the ware, blow nozzles 31 (Fig. 3) are inserted into the ware and remain there whilst the ware passes through the section. In the third section of the lehr the temperature of the glassware outer layers is rapidly raised to within the range 600‹ to 800‹ C. Also in this section nozzles are inserted into the ware to assist in heating the outer layers of the inner surfaces. However, if desired, whilst the external surfaces of the ware are being heated, the inner surfaces may be cooled. Finally, the ware passes in section 9 wherein it is rapidly cooled through the transformation range to room temperature.