Patent GB-378015-A (GB)
Title: Improvements in or relating to electrically heated glass annealing lehrs
IPC: C03B25/06
Filed: 1931-04-02
Abstract: 378,015. Electrically heated leers. BRITISH HARTFORD-FAIRMONT SYNDICATE, Ltd., 142, Audrey House, Ely Place, London.-(Assignees of Wadman, H. A.; 816, Farmington Avenue, Hartford, Connecticut, U.S.A.) April 2, 1931, No. 10115. Convention date, April 5, 1930. [Class 39 (iii).] In a tunnel glass annealing leer the ware is ' preconditioned before the annealing operation proper by heating or cooling the upper portions of the ware, and the temperature in the tunnel is regulated thermostatically. In the leer shown the preconditioning zone 9, Fig. 2, is formed with floor and roof flues 12, 15, which are open at one end to the atmosphere, and at the other, are in damper-controlled communication with a chamber 88 connected by a conduit 96 to a main wind box 97, Fig. 6. Adjacent the flues are electrical heating elements 100 .. 103, and by control of these elements and of the dampers 89, 95 heat can be supplied to or abstracted from the ware, and a differential treatment of the upper and lower parts of the ware can be effected. The preconditioning zone is followed by a soaking zone having a series of heating elements, and a cooling zone with lower and upper cooling flues 242, 258 which are reduced in size by steps 244, 270, Fig. 5, to provide a slow cooling zone following the soaking zone. The cooling flues are in damper-controlled communication at several points along their length with conduits 253, 268 leading to the main wind box 97, and these conduits are controlled by interconnected but relatively adjustable dampers 257, 269. A forced cooling zone at the discharge end of the leer is provided by admitting air to the tunnel under control of a pivoted end flap, and this air is withdrawn into the lower flue 242 through groups of openings in the floor of the tunnel. Air is also drawn into the open ends of the flues 242 under control of a damper which is operated simultaneously with a damper 330 for controlling the return of hot air to the tunnel through boxes 334 having curved delivery passages 336 adapted to direct the incoming air towards the entrance end of the tunnel. The damper 330 is actuated by a motor under control of a differential thermostat 351 as described in Specifications 356,920 and 357,075, [both in Group XII]. The dampers 89, 95 are controlled by a thermostat A positioned in the flue 12 above the heating element 101, and the setting of this thermostat is in turn controlled from a thermostat A<1> located in the soaking zone, this second control being effected in the manner described in Specification 355,467, [Group XII]. The main heating elements are controlled by thermostats in the soaking zone, and the ranges over which these operate can be adjusted to vary the top and bottom heating of the ware. The dampers 257, 269 controlling the cooling are operated by a motor 277, Fig. 16, in turn controlled by a thermostat D situated near the end of the slow cooling zone. For small variations in temperature the motor is supplied over cam-operated contacts 323, so as to run intermittently, while for large variations the contact 282 comes into operation to run the motor continuously. Reversal of the motor is effected by the contact 281 and relay 296. A similar arrangement is provided in connection with the control of the thermostat A by the thermostat A<1>.