Patent GB-103645-A (GB)
Title: Improvements in Induction Furnaces.
IPC: H05B6/20
Filed: 1916-12-22
Abstract: 103,645. Ajax Metal Co., (Assignees of Wyatt, J. R.). Jan. 24, 1916, [Convention date]. Induction and resistance furnaces. - A channel communicating with a molten bath, preferably well below its normal level, and forming therewith the secondary of a transformer, is bent at an acute angle, preferably less than 60 degrees, at a distance from the bath, in order to promote electro-dynamic circulation. The channel preferably opens into a groove in the bottom of the bath, transverse to the axis of tilting of the furnace, to prevent breakage of the circuit. More than one channel may be connected to a bath. A conductor, or a material conductive only when hot, may be used as the furnace lining, to heat by resistance. The common planes of the channel edges may be vertical, horizontal, or inclined. Fig. 1 shows a vertical arrangement. A casing 1 for the furnace body and a wedge-shaped casing 2 for the channel portion are separated by a transformer core 3 serving as an intermediate casing. Bolts 18 secure together the upper and lower casings 1, 2 and hold angle-irons 17 embracing the core. The central limb of the core is recessed at the corners 26 to accommodate a primary winding consisting of ribbon conductor wound with asbestos tape. To form the furnace chamber and channel 33, there is preferably used a pattern in lower and upper sections, which are successively inserted in the casing, asbestos paste being around them; the pattern is then burnt out. In modifications, the furnace body is made independently in one piece and is employed with or without a casing. The casing may also be independent of and within the outer limbs of the transformer core, being broken by joints to diminish its conductivity. A cover may consist of a cased ring 9 secured to the body by ears and bolts, and a conical plug 12 seated in the ring and hinged thereto. A pouring-spout 8 is provided. The channel 33 has its greatest transverse dimension parallel to the magnetic field. Its ends preferably make obtuse angles with the main chamber. They may be of the form shown in dotted lines in Fig. 1, may be straight for a short distance below the bath, may converge slightly at their upper ends, or may be of unvarying cross-section right up to their ends. Cool metal enters at their inner sides, and hotter metal is forced out at their remoter sides. Instead of the three-limbed core shown, one with a single outer limb may be used. Fig. 7 is a sectional plan of a furnace with the channel 3 horizontal, and with the windings on the outer limbs of the core. Two channels may be arranged in W form, or may be placed on opposite sides of the chamber; there may be provided either a single core, or separate cores with windings in series or parallel or connected to different sides of a two-phase circuit. Fig. 12 shows another horizontal arrangement with a passage 49 common to two channels 47, 48, and separate cores, 3a. Three channels bounded by vertical planes may be arranged triangularly as shown in plan in Fig. 16, a suitable core 3 and windings being shown in Fig. 17. Or the three channels may be parallel, with independent cores. Three-phase currents may be used with the last two arrangements. Such furnaces may be used for tempering with lead-allov or other baths; and for the melting of chips, shavings, turnings, &c. of brass, &c. for casting.