GB497480A - Improvements in or relating to furnaces for the heat treatment of materials or of articles - Google Patents

Abstract

497,480. Metal - heating &c. furnaces. MACDONALD, J., and G.W.B. ELECTRIC FURNACES, Ltd. April 15, 1937, Nos. 10784 and 34748. [Class 51 (ii)] A furnace installation comprises sets of furnace bases for use with a single belltype furnace unit and an appropriate number of bell covers for charges to be preheated and cooled, each base having pipe connections with at least one other base in its set for circulating a heat transferring gas between the bases, the cycle of operations being such that the bases arc charged in succession, and each charge is first preheated by heat interchange with a cooling charge, then heated by the furnace unit, and finally cooled by heat interchange with a charge to be preheated. In the four unit plant shown in Fig. 1, the bases 1, 2, 3, 4, which are charged in that order, are connected in pairs 1, 3 and 2, 4 by pipe systems 10, 11 leading to the suction and delivery ports of the fans 51. At the stage shown the charge 16 on the base 1 is being heated by the furnace unit 5, while heat interchange is being effected between a cooling charge 17 on the base 4 and a charge 19 being preheated on the base 2. The base 3 carries a charge which, after cooling off naturally, is to be replaced by a new charge. The charges 16, 17 and 19 are enclosed within protective covers 6, and around the cover on the base 2 is a heat-insulating bell 15. The fans 51 are preferably mounted so that they can be moved axially from a lower position shown at the bases 2, 4, Fig. 1, and on Fig. 5, in which their delivery ports register with passages 56 connected up with the pipe systems 10, 11, to an upper position, shown at the base 1, where the fan is effective to circulate the atmosphere within the cover 6. A spigot portion 52 on the fan closes the passages 59 for the internal circulation of the atmosphere when the fan is in its lower position. The change over from the lower to the upper position and vice versa may be effected automatically by the positioning and removal of the heating-bell. In a modified arrangement, Fig. 6 (not shown), the first and third and the second and fourth of a line of four bases are connected, so that charging can proceed in sequence along the line, and in a further modification, Fig. 7 (not shown), an indirect heat exchange between the atmospheres around two charges is effected by passing one atmosphere through a coil around which the other is circulated. When six bases are connected up in two sets of three the preheating and cooling of each of the charges can be effected in two stages.