GB1136964A - Continuous weighing of a consumable electrode - Google Patents

Abstract

1,136,964. Mounting arc furnace electrodes. WELLMAN INCANDESCENT FURNACE CO. Ltd. (Consarc Corp.). 3 Aug., 1966, No. 34756/66. Heading H5H. [Also in Division G1] A method of continuously measuring during melting the weight of a consumable electrode 16 for a vacuum arc-melting furnace, such as that of Specification 1,094,749, comprises placing a load sensitive transducer element between the electrode supporting-ram 12 and the electrode stub clamp 14. Clamp 14 is that of Specification 1,109,709. The apparatus 10 includes copper bushings 34, 35, conducting current to the electrode 16 through a copper tube 18, copper ram head 24 and electrode stub clamp 14. Bushing 34 has a cavity 38 containing four load cells 40-43 (see also Fig. 2, not shown), clamped by a pressure plate 46 on an elongatable rod 48 passing through the bushings 34, 35, and carrying a nut 52 for pre-stressing the load cells 40-43 via plate 46. Cells 40-43 are magnetostrictive devices varying in accordance with stress placed thereon, and conducting leads 58 transmit a signal proportional to the load on the cells, i.e. to the weight of the electrode 16, which signal is utilized to control the supply current or switch off the supply when the electrode 16 is almost consumed. Rod 48 has a greater modulus of elasticity than bushing 34 and, when electrode 16 is clamped in place, it elongates to a greater extent than bushing 34 to relieve the clamping stress on the load cells 40-43. The amount of stress relieved is proportional to the electrode weight, which decreases during melting. Instead of bushings 34, 35 and rod 48, a copper bellows-type bushing 62, Fig. 3 (not shown), may connect ram 12<SP>1</SP> and clamp 14<SP>1</SP>, the bushing 62 having a bore containing a tension-type stress detector element 66 with a resistance strain gauge 78 with leads 58<SP>1</SP> to a control circuit. The tension detector 66 is tensioned by the weight of the electrode, and as the bellows portion 64 of bushing 62 contracts the tension is relieved, to decrease the electrode weight measured by gauge 78 as the electrode is consumed. Alternatively, an annular bushing 80, Fig. 4 (not shown), is secured between ram 12<SP>11</SP> and clamp 14<SP>11</SP>, and has opposing holes 84, 86 providing maximum stress areas and having resistance strain gauges 88, 90 therein to indicate the stress on the bushing 80 and thereby the weight of the consumable electrode. In each embodiment the ram 12 is water-cooled to draw heat away from the load-sensitive element.