| 摘要 |
784,382. Tempered glass. COMPAGNIES REUNIES DES GLACES ET VERRES SPECIAUX DU NORD DE LA FRANCE. Feb. 10, 1956 [Feb. 14, 1955], No. 4189/56. Class 56. In the manufacture of tempered safety glass sheets, particularly for vehicle wind-screens, wherein two highly-tempered zones 2, 3 are separated by a barrier strip 8 of less highly tempered glass, the glass is so heat-treated that the complete periphery (i.e. including the ends 7) of the barrier strip is placed under permanent compression throughout its thickness as indicated by the groups of convergent arrows in Fig. 2. The groups of divergent arrows (broken lines) indicate tension in the middle of the thickness of the glass in the highly-tempered zones. The process consists essentially in heating the sheet in such a way that the temperature of the strip becomes lower than that of the zones it separates, and so that the temperature of the ends of the strip, adjacent the edges of the sheet, is lower still but is such that the viscosity of the glass at those ends is at least 10<SP>13</SP> poises. The whole sheet is then suddenly cooled. In general the selective heating is controlled by the use of screens over the strip and its ends. Fig. 10 shows an example of such screens 15, 17 and in this case the ends of the end screens 17 extend somewhat along the edges of the sheet adjacent the ends of the strip. The design of the screens, the materials therefor, and the times of their application and removal are discussed. Specifications 704,312 and 726,626 are referred to. |
