Patent GB-326517-A (GB)
Title: Improvements in, or relating to, electric furnaces
IPC: F27B9/38
Filed: 1928-09-15
Abstract: 326,517. Sadley, A., (Shipley, G. B., and Alinder, H.). Sept. 15, 1928. Resistance furnaces.-In a furnace installation, particularly adapted for annealing metal sheets, of the kind comprising an electrically heated tunnel furnace disposed above a loading and unloading or handling deck, a continuous train of work-carrying trucks 21 is maintained both in the furnace and on the handling deck, rams 31, 35 and elevators 8, 9 being provided to effect a continuous circulation of trucks through the installation. The furnace is formed with charging and discharging chambers 1, 3, having bottom openings for the insertion and removal of trucks by the elevators 8, 9, and is divided by vertical partitions 41 into a preheating zone 4, heating zone 5, and cooling zones 6, 7. A water jacket 94 is provided around the cooling zone and to maintain a non-oxidizing atmosphere within the furnace, a mixture of hydrogen and nitrogen is introduced at the junction of the zones 5, 6. Attached to the side walls of the heating and preheating zones and extending over substantially the whole height thereof are electric resistance elements 110, 111, 112, Fig. 9, arranged in independently controlled tiers. The lower part of the tunnel is insulated from the working chamber by the engagement of asbestos strips 102, 103, Fig. 2, carried by the side walls, with the upper portion and the sides respectively of the trucks 21; the latter are each provided with an end-plate 28 conforming closely to the openings in the partitions 41 and with racks 27 to support the sheets in a vertical position during their passage through the furnace. The charging and discharging openings in the chambers 1, 3 are sealed when the elevators 8, 9 are raised, by the engagement of a depending flange 11, Fig. 6, in a sand-trough 12 on the elevator platform, and also when they are lowered, by closure members 13 which are mounted on supports 14 and formed with a flange 15 to co-operate with a sand-trough 16. The elevators 8, 9 are carried by chains 57 passing over sprockets 54, 55 and attached to counterweights 58, the sprockets 54 being driven from electric motors 51 in connection with which are provided magnetic brakes 61 to lock the elevators in any desired position. Guide frames 62, mounted on each side of the elevators, are equipped with rollers 63, 64, 65 which bear against vertical guiding plates 66, 67, 68. Each elevator platform carries movable rails 25 which are automatically shifted, as the elevators are raised and lowered, away from the furnace and handling deck tracks 22, 23 to prevent fouling of the sealing means. Each rail 25 carries a rack 72 engaged by a pinion 73 secured to an arm 74 which is rocked about its pivot 75 by the engagement of a roller 81 in a cam-slot 82, the movement of the roller 81 being transmitted through links 78, 80 and a slidable rod 76 fitted with buffer springs 77, 79. A weighted lever device 91, Fig. 1, is provided in connection with each of the tracks 22, 23 to engage the trucks 21 and prevent their movement backwards into the charging chamber 1 and into the space below the elevator 9 respectively. At the opposite ends of the tracks 22, 23 are arranged catches 86 which prevent forward movement of the trucks 21 except when they are depressed by solenoids which are energized simultaneously, with the movements of the rams 31, 35.