US685727A - Electric glow-lamp. - Google Patents

Description

No. 685,727. Patented Oct. 29, IQOI. W. NERNST.

ELECTRIC GLOW LAMP.

(Application filed Apr. 10, 1901.)

(No Model.)

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UNITED STATES PATENT @FEICE.

WALTIIER NERNST, 'oF-co'rTINcEN, GERMANY, ASSIGNORYTO GEORGE WESTINGHOUSE, E PITTSBURG, PENNSYLVANIA.

ELECTRIC GLOW-Y-LAMP'.

s'PEcIEicATroN forming part of Letters Patent No. 685,727, dated October 29, 1901..

Original application filed April 28, 1898, Serial No. 679,081. Divided and application filed May 29, 1899, Serial No. 718,624; Again divided and this application filed April 10,1901. Serial No. 55,221-l (No model.)

To (ZZZ whom it may concern.-

Be it known that I, WALTHER NERNST, a subject of the Emperor of Germany, and a resident of Gottingen, Germany, have invented certain new and useful Improvements in Electric Glow-Lamps, (division of an application filed by me April 28, 1898, Serial No. 679,081,) of which the following is a specification.

My invention relates in a general way to the class of devices known as incandescent electric lamps and a method of lighting; but it diifers fundamentally from the incandescent lamps and methods heretofore used and involves certain peculiar features and characteristics which justify its classification as a distinct and novel species.

Heretofore all practical incandescent electric lamps have comprised a filament of conducting material, usually, if not always, of carbon, contained within an inclosing chamher from which the air is exhausted. The fact that the filaments heretofore employed will oxidize when heated in the open air has necessitated inclosing them in vacuum-chambers.

Various refractory materials comprising certain oxids, sulfids, silicates, and other saltrefractory materials were to be used in connection with electric lighting at ordinary voltages, it has heretofore been considered necessary to either maintain them in an incandescent st-ate by placing them in proximity to conductors heated by electric currents on to coat them or add to them 'or in some way combine with them'some good conducting material, such as a metal or carbon,which should afford a conducting-path for the current. For example, it has been proposed to impregnate or coat conductors-such, for instance, as platinum, iridium, 0r carbonwith a refracmelts or disintegrates or causes the refractorymaterial to crack off or disintegrate.

I have discovered that certain refractory salt-like combinations, particularly oxide usually classed as the rare earths, which are at ordinary temperatures non-conductors of electricity, as that term is usually employed, will when raised to the high temperature of incandescence become sufficiently good conductors to permit the passage of an electric current under moderate differences of potential and may be maintained sufficiently heated to retain their thus-acquired conducting qualities by the passage of the electric current therethrough. These materials when so traversed by electric currents not only emit more light under the influence of a given amount of electrical energy than the ordinary incandescent lamp, but they also resist I decomposition and disintegration even in the open air, and therefore a lamp constructed in accordance with my invention does not require a vacuum-chamber, though a vacuumchamber may be used in certain cases, if desired.

The general character-i. ing portion of my lamp are so widely different from those of the ordinary incandescent electric lamp that to term it a filament would be not only inappropriate, but to a certain extent misleading. The light is emitted therefrom without combustion or material disintegration even when exposed to the air, and being translucent it emits light from its interior and from its surface, and I have given the name glower to the light-giving portion and glow-lamp to the lamp itself as being properly applicable.

The materials which I have discovered to possess the qualities above referred to may be classed under the general term of dry stics of the light-givelectrolytes or dry conductors of the second class. By the expression conductors of the second class I refer to those which when in a conducting condition conduct cur rent by electrolytic action.

Prominent among the materials with which I have obtained excellent results may be mentioned oxid of magnesium, or magnesia, and oxid of zirconium, or zirconia; also, the oxids of yttrium, cerium, thorium, and the like. These materials when in a dry state and at normal temperatures are practically insulators or non-conductors; but when glowers made from them are heated to a state of incandescence they acquire conducting qualities to such an extent that electricity may be caused to pass through them at ordinary low pressures in sufficient quantities to keep them in the state of incandescence even after the means employed for imparting the original starting-heat is withdrawn. Instead of using these materials individually or alone for forming the glower two or more of them may be mixed or combined in varying proportions with advantageous results. Glowers made from a proper mixture of certain of the materials will pass into the conducting state at a lower initial or starting temperature than will a glower madev from one of the materials alone and will maintain, under the passage of the electric current, a luminous condition without deterioration better and for a longer time than will any single one of such materials. It is not, therefore, the mere mixture of such materials that I prescribe, but the utilization of such mixtures on account of their superior properties when brought to and maintained in a luminous condition. These materials even when in their best operating conducting condition have a specific resistance so great with reference to that of carbon that a glower to be used with a given voltage may be much shorter and thicker than the carbon filament of an ordinary incandescent lamp. For instance, a practical glower of, say, one-fiftieth'of an inch in diameter and one-half an inch in length may be made which when heated to a low incandescence will become a sufficiently good c011- ductor to be traversed nnder'a one-hundredvolt difference of potential by a sufficient current to bring it to and maintain it at a state of high incandescence. A current of, say, four-tenths of an ampere, or thereabout, will accomplish this result. As the material has sufficient strength to enable it to be used in much longer lengths than that above referred to, it is possible to construct lamps adapted to be operated at'very much higher voltages than is practicable with lamps using carbon filaments, a feature which may be utilized to obtain economy of transmission. This feature,

in connection with the high efficiency of the lamp, renders it possible to secure either a given illumination with a much higher transmission eiliciency than at present obtained or a higher illumination with the'present transmission efliciency, or both the illuminating and transmission efficiencies may be materially increased.

There are numerous diiferent proportions in which the different refractory materials adapted to the purposes of my invention may be used, and there is a very wide range for the selection of the different materials to be mixed together, and therefore I will attempt only, and it will only be necessary, to specify one or two examples. Very excellent results have been obtained from a mixture of approximately seventy per cent. of zirconia and thirty percent. of yttria, (oxid of yttrium.) Another mixture which I have used with good advantage consists of approximately ten per cent. of zirconia, seventy percent. of thoria, and twenty per cent. of yttria. I have also obtained excellent glowers from a mixture of about seventy per cent. of thoria and thirty per cent. of yttria. Another mixture consists of 0.5 per cent. of ceria, eighty per cent. of thoria, with 19.5 per cent of yttria. These percentages may be widely varied, and, generally speaking, the oxide of the rare earths are well adapted for mixture in widelyvarying proportions.

The process of preparing the glowers from which I have heretofore obtained the best results when two or more of theoxids are to be used together consists in thoroughly pulverizing and mixing the materials together into very intimate relations, then mixing therewith a binder of clear-starch paste, making a plastic mass which should be thoroughly worked. The water used in making the paste should be clear and preferably distilled to avoid the presence of lime, which is more volatile than the oxids of the rare earths, and therefore undesirable. The plastic mass may then be inserted in a press adapted to force the mixture through a small hole of the requisite diameter, dependent upon the ultimate diameter desired for the glower, and as the material leaves the press it may be hung over aglass rod or laid upon a suitable supportingsurface and allowed to dry. The material acquires sufficient strength when dried to be conveniently handled, and it is then heated to a very high temperature in any suitable manner-for instance, in an oxyhydrogen flame. It is desirable that as great a specific gravity as possible may be given to the material-that is to say, the smallest diameter for a given mass of a given length. Care should be taken that every part of the glower is brought to a high incandescence. Usually it is advantageous to heat the material gradually, so as to drive off the moisture and the binding material slowly, and thus lessen the liability of the surface becoming cracked. For example, it may be passed through a preliminary heat in a porcelain kiln. The eventual heating, however, should be carried to an extremely high temperature. \Vhen the material has been thus prepared, a proper length, dependent upon the voltage and current with which it IIO is to be used, is mounted between two suitable cond noting-wires. The ends may advantageously be fastened mechanically in any suitable wayas, for-instance, by inserting them into suitable sockets made by forming into spirals the-conducting-wires, which may be of platinum or other good conducting materials which melt only at a very high temperature. The junctions of the glower with the respective wires' are then built up by placing thereon in a liquid or paste-like condition small quantities of acementing material and heating and drying the same in a gas-flame or otherwise. This process is repeated until a firm union is obtained between the respective ends of the glower and the wires. It is advantageous also to make the points of juncture with the wires of larger diameter than the main portion of the glower, for then the points of contact with the wire will not during the operation of the lamp be as hot as the remainder of the glower, and therefore the wires themselves are less liable to burn olf. The paste or cement with which it is desirable to build up the ends may be of the same material as that used for forming the glower itself. I have obtained excellent results by pulverizing portions of glowers which have been previously prepared and heated to high temperatures and mixing the same with water, and, if desired, starch-paste may be added. Any suitable means for sup porting the conducting-wires and securing electrical connections therewith may be employed.

For the purpose of obtaining the preliminary or starting heating of the glower various different means maybe employed. Usually it is desirable that the heat should be applied only during the starting process and thenwithdrawn, although in some cases it maybe desired to continue the extraneous heat while the lamp itself is in operation. A very convenient starting-heater consists of a coil of platinum wire or other conducting material which may be heated to a high temperature in the open air by the passage of electric currents without being melted. This wire is coiled or otherwise arranged in such proximity to the glower that when heated by the passage of an electric current it will raise the glower to a sufficiently high temperature.

to cause it to acquire the necessary conducting capacity to permit sufficient current to flow through it under the influence of the difference of potential of the circuit upon which it is to be used to carry it to a state of high incandescence and maintain it there. When the lamp has once been started, the circuit through the heater may be interrupted manually or automatically, and, if it is desired, the heater may also be withdrawn from the immediate vicinity of the glower. In-

stead of imparting the starting-heat by the agency of electric currents other extraneous sources of heat may be employedas, for instance, a gas-flame or the flame of a lamp, or even a match in some instances.

The temperature to which the glower must be brought in order to have sufficient conductivity to allow enough current to flow through it to maintain itself in that conductive condition varies somewhatlwith different materials and proportions. Some of the mixtures will produce a glower which when heated to a conductive temperature will fall in resistance as rapidly under the influence of a constant difierence of potential as to permit a current to flow which would be destructive to the glower. With such glowers means should be employed for counteracting this effect and cause the glower to receive and consume only a predetermined amount of current,and therefore remain at a predetermined safe temperature. A convenient means for accomplishing this result with such glowers consists in introducing in series with the glower a correctly proportioned resistance, preferably having a high positive temperature coefficient, and therefore offering an increasing opposition to the flow of the current with increments of current. Resistances composed of materials having little or no positive temperature corrections may, however, be usedin cer tain cases. In constan t-potential alternating-' current circuits reactive coils may be used in lieu of such resistance as above referred to. The expenditure of energy in such compensatingdevices when required may be very low, as their effective resistance may be in some cases as low as two per cent. or even less of the resistance oifered by the glower when in operation if the lamps are used upon circuits having little or no variation in difference of potential-as, for instance, storagebattery circuits. When used upon circuits subject to wider-variations, it may be'desirable that this resistance should consume as much as five per cent. or even more. alternating-current circuits where reactive coils are used less than this will usually suflice.

The present applicatiomwhich is a division of my application, Serial No. 679,081, dated April 28, 1898, relates more particularly to that feature of the original application which is concerned with the arrangement of the heating-body in an independent circuit with respect to the glower and also to the use of a transparent material as the support for the heater.

Upon

' The present invention is illustrated in the 'pleted to the binding-posts c c of the lamp. The light-giving portion or glower A of the lamp is made in accordance with the description hereinbefore given. It is carried by two conductors a a of any suitable character, and these are connected with the terminals '0 c of the lamp. A bridge-piece a may be employed for holding the conductors a. a in their proper relative position. A heating or starting conductor B is shown in Fig. 1 as carried upon a glass or other transparent support II, and it incloses to a greater or less extent the glower A. Suitable supportingclips ff are provided for receiving the ends of the supports a (t so that a glower may be readily replaced. The heater-support II is here mounted, through the medium of a standard 0 and bracket 0 so that both the support II and its heating-conductor B remain stationary. On the other hand, the glower A and the parts connected therewith are mounted upon a movable bracket K, connected with the core 7c of a solenoid K, forming part of the glower-circuit. The core 7.; is supported by a spring t, connected with a horizontal extension of the standard 0. A downward movement of the core 71: within its solenoid will move the glower out from the inclosing support II. A rod *1", passing through an openingoflserves toguidetheparts throughout their motion. It will be understood that in some cases it may not be desired to separate the heater and the glower from each other, in which case light from the glower will be transmitted through the transparent heater-support. In this instanceI have shown the heater as being supplied from a separate source G of electricity instead of being in a branch circuit from the source G. The source G and the source G may either or both of them be sources of alternating or continuous current, as desired. In the heater-circuit I place a switch .9, by means of which the circuit may be opened or closed. An automatic circuit-interrupting device may be placed in the circuit of the heater, if desired. WVhen the switches D and s are closed, the current passes through the heater B, raising the glower A to such a temperature as will render it sufficiently conductive to be traversed by the current from the generator G. The solenoid K will then be energized, drawing down the core against the force of the springt and removing the glower A from within the inclosing support H. The circuit through the heater may then be interrupted by means of the switch 5, if desired. The interruption of the circuit through the glower automatically restores the parts to the positions shown in Fig. 1.

Ghana"? By requirement of the Patent Office this application is divided out of my application, Serial No. 718,624, which was filed May 20, 1899, as a division, of an earlier application, Serial No. 679,081, filed April 28, 1898.

I claim as my invention 1. In an electric-lighting system, a source of electric current, a glower which is nonconductive when cold and requires to be heated to be rendered conductive, in circuit with the said source, and an electric heater in an independent circuit and located in pro imity to the said glower.

2. In an electric-lighting system, a source of electric current, a glower which is nonconductive when cold and requires to be heated to be rendered conductive, in circuit with the said source, an electric heater in an independent circuit and located in proximity to the glower, and a switch in the heatercircuit for controlling the operation of the heater.

S. In an electric-lighting system, a source of electric current, a glower which is nonconductive when cold and requires to be heated to be rendered conductive, in circuit with the said source, an electric heater in an independent circuit and located in proximity to the said glower, and switches in the glower and heater circuits for controlling their operation.

4. In electric lamps, the combination with an incandescent body made of a material that is a non-conductor whencold and becomes a conductor when heated to a high temperature, of a resistance-conductor, a support of fireproof non conducting and transparent material surrounding the said incandescent body, and means for heating said resistance-conductor by the passage of electric currents, substantially as and for the purpose described.

5. Inelectricalincandescentlamps,thecombination with an incandescent body made of a material that isa non-conductor when cold and becomes a conductor when heated to a high temperature, of a wire resistance combined with a sleeve of fireproof non-conducting and transparent material such as glass surrounding the said incandescent body, and means for electrically heating said wire resistance, substantially as and for the purpose described.

Signed by me at Berlin this 27th of March, 1901.

WALTHER NERNST.

Witnesses:

WOLDEMAR IIAUPT, HENRY I'IASPER.

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