GB1004708A - Electric furnaces - Google Patents

Abstract

1,004,708. Electric resistance furnaces. SPEMBLY Ltd. Dec. 5, 1963 [Dec. 8, 1962], No. 46421/62. Heading H5H. In an electric furnace generally similar to that of Specification 908,667 the current supply connection to the heating element 17 comprises axially-extended arcuate supporting legs 18 integral with the element 17 and having lower portions which engage copper current feeders 9 in the form of quadrants cut longitudinally from a hollow cylinder. The feeders 9 are secured in position and connected to the current supply by insulated pins 10 and are in contact with a water-cooled shell 1 through an insulating layer 13, contact between members 1, 9 and 18 being obtained by means of a conical ceramic plug 25 which is forced into engagement with the legs 18 by movement of a lifting plate 22 controlled by adjustment of a spindle 21. Insertion of a key to perform this operation is facilitated by a hole 29 in the plug 25 which hole receives the refractory pillar 60 supporting the furnace hearth. The plug 25 has parts cut away axially to leave diametrically-opposed conical quadrants alternating with diametricallyopposed plane surfaces. Axial movement of the element 17 is prevented by complementary circumferential projections and recesses 19, 20 on members 9, 19 forming a bayonet-type joint. Apertures 7 enable the furnace to be evacuated or supplied with an inert gas. Fig. 3 shows a modification in which the mating surfaces of members 9, 18 are conical, and a refractory distance-piece 37 is inserted between near semicircular portions of the legs 18 to prevent inward radial movement thereof when a nut 34 is screwed down on to an insulating ring 35 to engage members 9, 18. The member 37 has a counterbored hole to support the refractory furnace pillar, Fig. 4 (not shown). The baseplate 3 is provided with apertures fitted with plugged bosses 38 of the same size as the bosses 11 in the shell 1, so that if desired an alternative form of heating element, mounting therefor and current supply thereto may be employed, the bosses 38 being used instead of the bosses 11 which are then plugged and sealed in a manner similar to that shown for the bosses 38 in Fig. 1. One such alternative is described having a cylindrical-shaped heating element which is formed from tungsten and tantalum strips and is suspended from tantalum arms secured to water-cooled current-feeding tubes supported in the bosses 38, Fig. 5 (not shown).