GB563138A - Improvements in or relating to the manufacture of tempered glass - Google Patents

Abstract

563,138. Tempering glass. SUNTEX SAFETY GLASS INDUSTRIES, Ltd., and GLASER, H. Jan. 26, 1943, No. 1325. [Class 56] An apparatus for tempering glass comprises a polygonal tunnel constructed in a number of sections 11, Fig. 1, through which the glass is moved step-by-step while suspended from wheeled trolleys 20, Fig. 3, that run on rails 15, 16. Each of the trolleys carries a number of posts 21 which are engaged by pins 24 on a chain 22 that extends around sprockets 23, Fig. 1, and is driven intermittently by an electric motor 31 that is connected to the driving sprocket through a magnetic clutch 32. Section 63 of the turret is a loading and unloading section ; sections 64 ... 70 are heating sections in each of which the temperature of the glass is raised by a predetermined amount as indicated by a pyrometer 71 ; sections 83, 89, 93 are cooling sections and section 95 is an inspection section where the glass is examined while illuminated by polarized light. A glass plate or sheet 53, Fig. 3, to be tempered is gripped between metal grids 56 secured to the arms of tongs 52 so shaped that the weight of the glass forces the grids towards one another. The arms of the tongs are insulated electrically from one another and are provided with contact arms 57. The sections 64 ... 68 are heated by electric heating resistances; in section 69, the heating device is of the induction type in which a mass of iron is heated by magnetic hysteresis and a uniform temperature is maintained automatically by the diminution of the magnetic permeability of the iron. Section 70 also is provided with induction heating units 75 and in this section the arms 57 of the tongs make contact with brushes 58, 59 connected by leads 60, 61 with a battery 76 and a relay 77. When the glass attains a temperature slightly below its softening point it becomes conductive and the current from the battery 76 flows through the glass between the grids 56. This operates the relay 77 which breaks the circuit of the magnetic clutch 33 and allows the motor to move the chain 22 and the whole of the sheets of glass from one section of the tunnel to the next. The sheet that was in the section 70 is' carried into the first cooling section 83 when it is chilled by air jets from nozzles in the known way. The nozzles may be movable in a circular path parallel to the surface of the glass or they may be reciprocated slowly to and from the sheet. Moisture may be added to the air to increase the chilling effect. The grids 56 screen parts of the glass from the direct air blast, thereby producing in the finished sheet tempered areas separated by lightly-tempered zones so that shattering of a windscreen, for example, is localised. Cooling by air jets is continued in section 89, and in section 93 cooling is completed by a current of air blown through the. section by a fan 94. After examination in section 95, the finished sheet is removed at station 63. The floor of the furnace section is formed by hinged and counterweighted plates 102, 103 with refractory linings 100, 101 respectively. The trolleys 20 carry plates 48 with flanges 49 which dip into sand in troughs 47 to seal the upper ends of the heating chambers.