PROCESS AND APPARATUS FOR CONTACT HARDENING OF A FLAT GLASS ARTICLE AND THE HARDENED FLAT GLASS ARTICLE

摘要

For contact hardening of a flat glass element (3) having a through-hole (12) the surfaces of the flat glass element (3) heated to hardening temperature are subjected to the action of cooled clamping plates (18, 19) with coating of fibers exhibiting high thermal stability. During action of the clamping plates (18, 19), cooling gas is supplied on the flat glass element (3) inner surfaces defining an opening (12). The apparatus for making the above-described process consists of two cooled clamping plates (18, 19), whereby the clamping plate (18) has on its side turned toward the flat glass element (3) a supply and discharge passage (12). The clamping plates (18, 19) are covered on the side being brought into contact with the flat glass element (3) with a cloth, fabric or netting (5, 7).