GB1025518A - Blasthead structure,particularly for tempering glass sheets - Google Patents

Abstract

A blasthead structure for thermally tempering glass sheets comprises a pair of horizontally opposed blastheads 27, 271, Fig. 2 (not shown), each blasthead comprising walls partly defining a pressure compartment which is open towards a substantially similar compartment of the other blasthead, and means for introducing a gas to the compartments at substantially equal rates of flow, wherein the walls are arranged to extend towards a glass sheet suspended therebetween to within a predetermined and uniform distance of the surfaces of said sheet so as to leave a clearance space 63, Fig. 6 (not shown), between the walls and the surfaces whereby escape of the gas is substantially restricted to the clearance space 63 and the pressure so created in the pressure compartments causes automatic centring of the sheet between the blastheads, means 51, Fig. 5 (not shown), being provided on the outer side of the compartment walls for the exit of the gas. The blastheads are each divided into four compartments 49 and two end compartments 52, 53, Fig. 3 (not shown), by a series of walls extending across their width and depth. Within these compartments nozzles 61 are arranged in a regular square lattice pattern, of six horizontal rows in compartments 49 and half as many again in the end compartments 52, 53. The nozzles of the centre four rows are each joined to the nozzle below by a vertical web 64, Fig. 5, with halfwebs extending from the last two nozzles, whilst the end two rows are joined by a horizontal web 62 thus providing sub-compartments. Between each compartment 49, 52, 53 is provided an exhaust area 51, but within which are placed blast nozzles 70 (Fig. 6). The nozzles of one blasthead are located directly opposite to the nozzles of the other blasthead. The blastheads are slidingly connected to air ducts which have valves therein all operated by a single pneumatic cylinder 48, Fig. 1 (not shown). The blastheads are mounted for oscillatory motion and have a surface contour similar to that of the glass sheet to be tempered. Preferably the blasthead apparatus is mounted immediately below a furnace for heating glass sheets. A glass sheet suspended freely from its upper edge is heated in the furnace and then lowered to between the blastheads. The construction of the pressure compartments is such that if the sheet moves towards one blasthead, pressure builds up very quickly in its pressure compartments and decreases rapidly in those of the other blasthead, the sheet thus being quickly centred. The cooled tempered sheet is finally removed.