US1006021A - Electric lighting. - Google Patents

Description

C. P. STEINMETZ.

ELECTRIC LIGHTING.

APPLIOATION Hmm 1211.30. .1900.

Patented 0@t.17,1911.

UNITED sTATEs PATENT oEEicE.

CHARLES P.'sT E1NME'rz, OE SCHENECTADY, NEW YORK, v.lissiefiron To GENERAL ELECTRIC COMPANY, A CORPORATION OP NEW YORK.

ELECTRIC LIGHTING.

Speclcation of Letters Patent. Patented 0013.17, 1911..v

Application med April 30, 1900. Serial No. 14,790.

To all whom it may concern: v

lle it known that I, CHAnLEs P. STEIN METZ, a citizen of the vUnit-ed States, residing at Schenectady, county of Schenectady, State of New York, have invented certain new and useful Improvements in Electric Lighting, of which lthe following is a specitication. i

I have discovered that the light from an electric arc, excluding that portion of the light which comes directly from the crater,

. is to a, very large extent independent of the temperature at which the arc may exist, but depends rather on the nature of the substances constituting the are stream.. 'lhis being the case, it is advantageous to cause the arc to spring from a terminal, or between terminals, capable of giving forth vapor at eoniparativoly low temperatures, since. the temperaturo'of thearc stream is tixed, as is the temperature of any other saturated vapor, by the boiling point of' the substance vaporized. These considerations point to the advisability of replacing the few substances have their correct color` carbon arc of commerce by an are from terminals one at least of which is formed of lines, so that inY the light from a mercury.

arc redl substances appear black, and very values. In a former applicationfor Letters Patent ot the United States, Serial Number 7 265, I have set forth and claimed a method of overcoming this very serious defect, and without attempting herein to define the scope of the said application, or to setfortli in detail the disclosure made therein, it may be sufficient here to state that the said application contemplated the addition to the arc of conducting vapors of such a nature as to reinforce the spectrum. I find that nonconducting vapors have no effect in the mercury arc, from which I am led to believe that the action is inthe nature of a sympathetic vibration of conducting vapors under` the electrical and physical conditions existent in the arc stream. Any substances added tothe stream, if capable of producing conducting vapors, give light corresponding to the arc spectra of such substances, but carbon on the one hand and gases on the ,other hand, if added to the arc stream, ap-

parently have no etlect whatever, which is probably due to the extremely low tempera-` ture at which thel mercury are is maintained.v

I have also shown in the application above set forth, that it is, commercially speaking, essential to surround the are by inclosing chamber or envelop, for the reason that the mercury are is somewhat unstable, and also because of the extremely poisonous vapors which it produces. I have further shown that the color-modifying substances which fulfil the necessary conditions, as for exam ple, potassium, sodium, lithium,rliubidiuunA indium and tliallium, vigorously attack the transparent envelop, which, for example, may be constituted. of the best hard glass, and form :onlthe inside thereof a black deposit which destro-ys the usefulness of the lamp in a very short time, so that the lamp eau scarcely be said to be operative if the color-modi tying substances are introduced in the simple manner thus far described. In my said former application I have set forth at considerable length a method of overcoming this diticulty, which consists in causing the colormodifying substances to exist in the arc in an ionized state, which may be brought about, as described in said application, by introducing them, not in their natural condition, but rather as anhydrous iodids, or other halogen salts, with or without a neutral or diluent substance for the purpose of reducing the effect of the color-modifying substances upon the are. Ina certain other application for Letters Patent, April 21,

substances have, it is true, some chemical` action upon the glass, but the continual combination land recombination which takes place 1s such as to preserve the translucency of the envelop, for the reason that the salts` formed by such action are translucent in their nature, and the inner surface of the envelop is not blackened, but merely given an agreeable frosted appearance.-

My present application sets forth and claims certain improvements upon" the methods and apparatus described in the above- `mentioned applications.

O ne feature of my present invention is the reduction of the potential necessary `to start the arc by the use of a rarefied atmosphere of hydrogen or other material of lower dielectric strength than air, as for example helion or argon, by which I am able to very greatly reduce the initial voltage necessary for the starting of the lamp.

Further, I find that the action of the halo-- paratively speaking, whereas they should,

for best results, be uniformly distributed over the terminal in order that the are may at all times run through a layer of colormodifying substance. The silicates above discussed do notshare this disadvantage,

but they are all open to the objection thatv their action takes place at a temperature vslightly higher than that of the action of the iodids.

Further, I nd that the iodids actually tend to emphasize and bring out the color of the modifying substances, imparting awarmer tinge to the light from the lamp. Therefore in lamps constructed in accordance with my present invention, I wholly inclose the mercury or other lightgiving substance in a hermetically-sealed glass vessel filled, say, with hydrogen, and exhausted to a fairly high vacuum, measured for example by onemillimeter of mercury on the ordinary scale or less. Further, I provide for an excessof iodin in the colormodifying substances, by the addition ofV free iodin or of iodid of mercury, or in some otherequivalent manner.

My present invention further comprises a new means for the initial starting of the lamp, which will be fully described land claimed below, as well as an automatic arrangement whereby the length of theo arc will be regulated and maintained within definite limits by the pressure generated by the arc itself.

The drawings accompanying this specification represent a simple form of lamp embodying certain features of my present invention.

and the surfaces of the electrodes are cov-V' ered with a color-modifying substance, in accordance with the principles above set forth. In this particular case we may assume that it is desired to produce whiteV light, in which case the color-modifying substance may be constituted of a mixturel of the iodids of lithium and sodium, or lithium, sodium and potassium, which mixture is prepared by heating these iodids, the lithium iodid preponderating, in an atmosphere of hydrogen under reduced pressure with the addition of some free iodin and` with the exclusion of air. To this mixture -of oidids may be added a diluent substance such as fiuorid of calcium. This type of lamp is preferably included ."fn/,afconstantcurrent circuit, in series. It is'well to warm minals nearly to the boiling point of the mercury, bythe application of a spirit lamp or other source of heat. When this result has been achieved, the lamp is included in the constant-current circuit, alternating or direct, by any suitable switching apparatus, whereupon the arc strilies across from one electrode to the other land fills the whole tube, or the central portion of the tube, according to the degree of thevacuum, with a beautiful white light. The mercury furnishes the violet, blue, green and yellow lines of the spectrum, while the orange and red lines are furnished by the color-modifythe lamp, and particularly to raise the terloo ing substances sodium and lithium. As the arc plays over the surface of the mercury, it is continuously taking up small quantities ofthe lithium and sodium iodids, which disassociate in the arc, allowing the metallic pieces to vibrate under the electrostatic stress, or otherwise asthe case may be, while the disassociated atoms of iodin continuously stand guard, as it'were, over the atoms of sodium and lithium, and preventl them from attacking the glass. This is the result of the fact that the metallic substances exist in the arc in a state in which their natural aiiinity for the glass is to a certain extent satisfied, as it were, bythe tendency of the iodin atoms to be combined with them. Thus the 4glass is protected, and the additional free iodin above mentioned tends to help the color-modifying substances to fulfil their functions, which I attribute to the fact that the excess increases the volatility of the lithium and potassium.

By increasing the amount of any one of the color-modifying substances, and by suitiso ' ably choosing said substances in laccordance with their known arc spectra, the light may be given any desired color.

In conclusion, Iwillstate that although V by Letters Patent of the United States, is,

1 VU.'Ihemethod of producing 'light of any .desired color or combination Aof colors,

which consists in drawing `an arc from a terminal vaporizable at a low temperature in a suitable envelop, introducinga c0lormodifying substanceto the arc and maintainin it in an ionized 'state bytheaddil tion 0 a protecting substance, andincreasing the action of the-color-modifying subl20 stance by the introduction-of an excess of the protecting substance.

2. The method of modifying the color of an arc light and protecting the inclosure in which the`same is contained, which consists 2'5 inv introducing vaporous colormodifying substances ina form in which their chemical activity withfreference to the envelop is neutralized, and protecting the modifying substances from -the action, of moisture or of 30 the atmosphere.

In witnesswhereof I have hereunto set my hand this 2.7 th day of April, 1.900.

y le CHARLES P. STEINMETZ. Witnesses: p l

BENJAMIN B; HULL, ALEX F. MACDONALD.

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