Patent GB-1462513-A (GB)
Title: Furnaces for heat treating glass
IPC: F27B9/36
Filed: 1974-03-27
Abstract: 1462513 Glass treating furnace H A Mc- MASTER and N C NITSCHKE 27 March 1974 [1 June 1973 21 Jan 1974] 8937/76 Divided out of 1462512 Heading C1M [Also in Division F4] In apparatus for tempering glass sheet material G including a conveyer (E) having an inlet end at a loading station (C) and extending through a treatment zone, such as a furnace A and tempering station (B) and a discharge end at an unloading station (D) together with carriers 2 for supporting glass sheets G and engageable with the conveyer E for movement therewith, the furnace A has a top wall 14 with an aperture 76 therein, the conveyer E comprises a pair of spaced parallel rails 188 extending from station C, through stations A, B and to station D which extend across the top wall 14 of furnace A parallel to slot 76, one on each side thereof, and a pair of endless flexible chains 190 each having one run supported on one of the rails 188 and the carrier 2 comprises at least one slide member 190 bridging the space between the rails 188 and frictionally supported on the chains 190 when located on the conveyer E so as to be frictionally advanced thereby. The conveyer chain 190 comprises rollers 194 on axes 195 interconnected by links 192, the slide members 196 resting on the rollers 194. Friction material such as plaster of paris is supplied to the rollers on their return run through channel rails 206 at each end thereof. Chain 190 is advanced intermittently by motor 222 with a timing motor 224 and cam 226 so that carrier 2 has suitable dwell periods at the loading and unloading stations C, D and in the furnace A and blasthead B. Chains 190 extend round idler sprockets 202 and drive sprockets 204 on shaft of drive gears 225 engaged with gears (223) on output shaft (221) of motor 222. The active run of chains 190 extends through an enclosure 228 covering the slot 76 and the top wall 236 has slots 230 covered by a housing 237 to which cooling air is supplied by a blower 239 which cools the chains 190 and prevents loss of hot gases from the furnace through slot 76. Smaller slots (241) adjacent each end of the furnace A provide an air curtain over the entrance and exit 74 while the glass sheet G is being moved into and out of the furnace A before doors 84 are positioned while the glass sheet G is heated. The carrier 2 is returned from the unloading station D to the loading station C by a further drive chain (252) through an elongated housing 242 on idler rollers 250, the drive chain 252 having lateral lugs (256) which engage a slide member 196, the drive chain 252 being driven to synchronize with chains 190. In an alternative arrangement, the return runs of chains 190 are positioned in enclosures, also air cooled, either side of slot 76, between the enclosure 228 and the top of the furnace A. The furnace A comprises top 6, bottom 8 and side walls 10 of refractory material 12, with heating means 18 throughout, divided by a partition 22 into first zone 24 and second zone 26, there being gas treating and distributing means in zone 24 to draw gas from a low temperature area of zone 26 into zone 24, draw ambient gas from the exterior of the furnace into zone 24, mix the two gases to form a substantially homogeneous mixture of gases, heat the mixed gases and force the heated, homogeneous mixture of gases into zone 26. Furnace A, as shown, is of circular cross-section in two halves leaving entrance and exit slots 74 covered by refractory dross 84. The partition 22 is spaced from the inner side walls 10, and a series of vanes 30 are seated on the periphery 28 to span the gap, leaving a series of slots 32, the vanes 30 directing gases from zone 24 past the heating elements 18. Openings 36 in partition 22 allow passage for gases from the lower portion of the upper zone 26 to pass into an intake channel 38 in zone 24. In the lower zone 24, circular walls 44, 48 divide the zone into a chimney 42, the intake chamber 38 and a discharge chamber 40. Four blowers 50, powered by motors 52, are mounted in chamber 40, the shaft 56 of each blower extending through an opening 58 in wall 10, the opening 58 being of greater diameter so that ambient air is drawn into the blower 50. Each blower 50 is connected to intake chamber 38 by an opening 60 in wall 48 and has its discharge opening (62) directed along the length of chamber 40, there being a ramp (64) extending from the lower end of one opening 62<SP>1</SP> upwardly towards the adjacent blower and near the slots 32 for deflecting the flow into the upper zone 26. The chimney 42 has an adjustable damper 46 in the bottom wall 8 and is connected with intake chamber 38 by a plurality of openings 66 so that blower 50 also draws ambient air through the chimney 42, which is thereby mixed with the gases from zone 26 through openings 36. Heating elements 18 in zones 24 are controlled by a differential air heat controller 72 responding to the temperature differential sensed by thermocouples 68 and 70 in upper zone 26 and slots 32 respectively, a further control being provided for the elements 18 in the upper zone 26. The door 84 covering slots 74 is formed by a series of segments 88 adjustably secured to an elongated support bar 86, each segment 88 being supported by a sheath 92 of steel having inwardly projecting, block engaging, flanges 96 and bar engaging flanges (94) with slots (98) for bolts (100) inserted through openings in the bar 86. The door 84 is moved into and out of position by an hydraulic ram and system of links. The blasthead B comprises a plenum chamber 130, supported for reciprocatory movement on a stationary frame including uprights 132, 134, cross-beam 136 and base 138, and including two U-shaped supporting yokes 139 with upright segments 140 and 142 secured together and to a base member 144, each member 144 being supported on an eccentric 146 non-rotatably secured to a driven shaft 148 and suspended from the beam 136 on springs 154 which extend from beam 136 to brackets 156 on upright segments 140. Plenum chambers 158 have inclined outer side walls 162 extending from a collar 160 and parallel inner side faces 164 from which a bank of nozzles 166 extend inwardly towards sheet 9, each nozzle 166 being inclined downwardly, the nozzles 166 at the upper end of each bank having a greater inclination than the remainder. Air is provided to the plenum chambers 158 by a pair of blowers (178) feeding a common duct (180) and dividing into separate ducts 182, 184, a damper (185) being provided to equalize pressures in the two ducts 182, 184. Air is fed from each duct 182, 184 to its outlet 187 lying within collar 160 and provided with rolling seal members 191.