Fig. 239 is similar to Fig. 238, except that the keeper T is not made use of and the armature itself swings into and out of the range of the intense action of the heat from the burner H. Fig. 240 is a diagram similar to Fig. 231, except that in place of using a spring and stops, the armature is shown as connected by a link, to the crank of a fly-wheel, so that the fly-wheel will be revolved as rapidly as the armature can be heated and cooled to the necessary extent. A spring may be used in addition, as in Fig. 231. In Fig. 241 the armatures A A are connected by a link, so that one will be heating while the other is cooling, and the attraction exerted to move the cooled armature is availed of to draw away the heated armature instead of using a spring.
Mr. Tesla has also devoted his attention to the development of a pyromagnetic generator of electricity[13] based upon the following laws: First, that electricity or electrical energy is developed in any conducting body by subjecting such body to a varying magnetic influence; and second, that the magnetic properties of iron or other magnetic substance may be partially or entirely destroyed or caused to disappear by raising it to a certain temperature, but restored and caused to reappear by again lowering its temperature to a certain degree. These laws may be applied in the production of electrical currents in many ways, the principle of which is in all cases the same, viz., to subject a conductor to a varying magnetic influence, producing such variations by the application of heat, or, more strictly speaking, by the application or action of a varying temperature upon the source of the magnetism. This principle of operation may be illustrated by a simple experiment: Place end to end, and preferably in actual contact, a permanently magnetized steel bar and a strip or bar of soft iron. Around the end of the iron bar or plate wind a coil of insulated wire. Then apply to the iron between the coil and the steel bar a flame or other source of heat which will be capable of raising that portion of the iron to an orange red, or a temperature of about 600° centigrade. When this condition is reached, the iron somewhat suddenly loses its magnetic properties, if it be very thin, and the same effect is produced as though the iron had been moved away from the magnet or the heated section had been removed. This change of position, however, is accompanied by a shifting of the magnetic lines, or, in other words, by a variation in the magnetic influence to which the coil is exposed, and a current in the coil is the result. Then remove the flame or in any other way reduce the temperature of the iron. The lowering of its temperature is accompanied by a return of its magnetic properties, and another change of magnetic conditions occurs, accompanied by a current in an opposite direction in the coil. The same operation may be repeated indefinitely, the effect upon the coil being similar to that which would follow from moving the magnetized bar to and from the end of the iron bar or plate.
The device illustrated below is a means of obtaining this result, the features of novelty in the invention being, first, the employment of an artificial cooling device, and, second, inclosing the source of heat and that portion of the magnetic circuit exposed to the heat and artificially cooling the heated part.
These improvements are applicable generally to the generators constructed on the plan above described—that is to say, we may use an artificial cooling device in conjunction with a variable or varied or uniform source of heat.
| Fig. 242. | Fig. 243. |
Fig. 242 is a central vertical longitudinal section of the complete apparatus and Fig. 243 is a cross-section of the magnetic armature-core of the generator.
Let A represent a magnetized core or permanent magnet the poles of which are bridged by an armature-core composed of a casing or shell B inclosing a number of hollow iron tubes C. Around this core are wound the conductors E E', to form the coils in which the currents are developed. In the circuits of these coils are current-consuming devices, as F F'.
D is a furnace or closed fire-box, through which the central portion of the core B extends. Above the fire is a boiler K, containing water. The flue L from the fire-box may extend up through the boiler.
G is a water-supply pipe, and H is the steam-exhaust pipe, which communicates with all the tubes C in the armature B, so that steam escaping from the boiler will pass through the tubes.