ES360054A1 - Improvements in or relating to tempered glass sheets and their manufacture - Google Patents

Abstract

A tempered glass sheet for use as a windscreen is characterized by a fragmentation system comprising in a central zone C successive strips 6 with fine fragmentation characteristics alternating with strips 4 with larger fragmentation characteristics (the strips preferably being parallel and vertical, and the width of the larger fragment strips preferably corresponding to the mean large fragment diameter) and by a marginal zone M 1 , M 2 in which the size of fragments 7a, 7b, 7c increases from the sheet edge towards the central zone. The sheet is obtained by differential cooling of the centre zone to give strips of glass which are lowtempered and high-tempered respectively and by differential tempering of the marginal zone, the degree of tempering diminishing from sheet edge to centre zone. Apparatus for producing the sheet may comprise two chests 9 and 10, fed with cooling fluid under pressure from ducts 11, each main chest containing a smaller chest 18 and 19 whose periphery corresponds to that of the central zone of the glass, and each small chest having nozzles 20 so arranged that blasts of cooling fluid fall in lines corresponding to fine fragmentation strips 6 (large fragment strips 4 remaining untempered), the remaining blowing surfaces 14 and 15 of the chests 9 and 10 having perforations 25, either of diameters which decrease towards the small chest or whose spacing increases towards the centre, so that the degree of tempering decreases, and the fragment size increases, from edge to centre. The pressure in chests 18 and 19 may be varied from 9 and 10 by control means 23 and 24, which operate sliding plates 21 and 22. The chests 9 and 10 may be subjected to a displacement motion parallel to the strips of the central zone, ducts 11 having deformable parts 12 to allow this.