Patent GB-191214741-A (GB)
Title: Improved Electrodes for Arc Lamps.
Inventor: BLONDEL ANDRE
IPC: H05B31/06
Filed: 1912-06-24
Granted: 1913-04-24
Abstract: 14,741. Blondel, A. June 24. Arc - lamp electrodes. - A flame-arc electrode consists of inner and outer zones, both made with carbon paste, of such compositions that the inner burns less readily than the outer, and the end of the electrode remains convex. If the inner zone is of pure carbon, it is made relatively small. In one type of electrode, the inner zone contains a smaller proportion of mineral matter than the outer; for instance, the inner and outer zones may have diameters of 12 to 15 and 22 millimetres and contain 30 to 40 per cent and 40 to 70 per cent of mineral matter respectively. Preferably, the percentage of mineral matter in the inner zone is not more than four-fifths of the percentage in the outer zone. A heavilymineralized outer zone may be thinly covered with pure or lightly-mineralized carbon which burns at the same rate as the outer zone when the air has access to the electrode. The inner zone, especially if star-shaped in section, may contain little or no mineral matter and be reduced in diameter, say to 0À25-0À35 of the external diameter of the electrode. Such an inner zone becomes impregnated with mineral matter during burning. One or more heavilymineralized star-shaped or other cores 3 may be arranged in the inner zone, or a heavilymineralized layer may be placed between the zones. A single core may have a diameter of 4 to 6 millimetres. Both zones, as well as the core, may be of star-shaped section. Suitable mineral materials are oxides, carbides, fluorides, borates, cerates, silicates, tungstates, molybdates, titanates, manganates, or ferrates of alkali or alkaline-earth metals, manganese, cerium, lanthanum, titanium, tungsten, or boron. The outer zones may contain 25 parts of calcium fluoride, or of a mixture of calcium and cerium fluorides, 2 of calcium or barium borate or tungstate, 3À5 of alkaline borates, 5 of alkaline silicates, 16 of gas or petroleum coke, 5 of lamp-black, and 16 of tar or pitch. For the inner zone, a larger proportion of coke is employed. Cores may consist of the same mineral substances without coke or lamp-black,- or with lamp-black only; thin tar, silicates, gum, or dextrine may be used as binding- material. In another type of electrode, the mineral matter such as carbide of titanium or tungsten in the inner zone is less volatile than that in the outer one. For instance, 'the inner zone may contain 35 parts of titanium carbide, 25 of calcium fluoride, 1 of potassium borate, 2 of sodium borate, 7 of sodium silicate, and 2 of potassium silicate, while the outer zone consists of 25 parts of cerium fluoride, 10 of calcium fluoride, 3 of alkaline borates, 1 of calcium borate, 9 of alkaline silicates, 1 of boric acid, 40 of gas-retort carbon, 6 of lampblack, and sufficient tar or pitch to agglomerate the mixture. In the latter mixture, the alkaline borates and silicates may be replaced by tungstates or molybdates of the alkaline metals or rare earths, and in either mixture they may be replaced by cryolite. The two zones and the outer coating, if any, may be made simultaneously, holes being left for cores if required. A wire a, a' may be inserted in one zone or each, or the electrode may be electro-plated. Specifications 17,406/02, 6060/03, and 6061/03 are referred to.