Figure 10.—Electric furnace for producing elemental phosphorus, invented by Thomas Parker of Newbridge, England, and assigned to The Electric Construction Corporation of the same place. The drawing is part of United States patent 482,586 (September 13, 1892). The furnace was patented in England on October 29, 1889 (no. 17,060); in France on June 23, 1890 (no. 206,566); in Germany on June 17, 1890 (no. 55,700); and in Italy on October 23, 1890 (no. 431). The following explanation is cited from the U.S. patent:
Figure 1 [shown here] is a vertical section of the furnace, and Fig. 2 is a diagram to illustrate the means for regulating the electro-motive force or quantity of current across the furnace.
F is the furnace containing the charge to be treated. It has an inlet-hopper at a, with slides AA, by which the charge can be admitted without opening communication between the interior of the furnace and the outer air.
B is a screw conveyer by which the charge is pushed forward into the furnace.
c´c´ are the electrodes, consisting of blocks or cylinders or the like of carbon fixed in metal socket-pieces c c, to which the electric-circuit wires d from the dynamo D are affixed. The current, as aforesaid, may be either continuous or alternating. c2c2 are rods of metal or carbon, which are used to establish the electric circuit through the furnace, the said rods being inserted into holes in conductors c3 (in contact with the socket-pieces c) and in the furnace, as shown.
g is the outlet for the gas or vapor, h the slag-tap hole, and x the opening for manipulating the charge, the said openings being closed by clay or otherwise when the furnace is at work.
I use coke or other form of carbon in the charge between the electrodes c´, the said coke being in contact with the said electrodes, so that complete incandescence is insured.
A means for varying the electro-motive force or quantity of current across the furnace with the varying resistance of the charge is illustrated by the diagram, Fig. 2. c´ c2 indicate the electrodes in the furnace, as in Fig. 1, and D is the dynamo and T its terminals. E represents the exciting-circuit. R R are resistances, and R S is the resistance-switch, which is operated to put in more or less resistance at R as the resistance of the charge in the furnace lessens or increases. This switch may be automatically operated, and a suitable arrangement for the purpose is a current-regulator such as is described in the specification of English Letters Patent No. 14,504, of September 14, 1889, granted to William Henry Douglas and Thomas Hugh Parker.