US1531966A - Electrical glow device - Google Patents

Description

March 31. 1925.

G. M. J. MACKAY ELECTRICAL GLOW DEVICE Fi1ed Jan. 26, 1920 Inventor ALI/AM Mfr/1A UM MM C e a m m o lug/u m fl e%.@

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Patented 31, 1925 enonqn m. J. mcx'air, or scnnnncmnx NEW YonxfAssIeNon 'ro GENERAL nine .1310 COMPANY, A CORPORATION OF NEW YORK.

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\ Application filed January 26, 1820. .Seflal No. 354,195.v

To all whom it may concern:

Be it known that I, GEORGE M. J. MAGKAY,

' a citizen of the United States, residing at Schenectady, in the county of Schenectady, State .of New York, have invented certain new and useful Improvements in Electrical Glow Devices, of whichthe following is a specification. 1 v

The present inventionrelates to electrical glow devices and comprises a means and a method of producing an electrical discharge having new and technically useful characteristics. I p

My invention in one of its aspects 'is an electric lamp of higher efficiency than herebefore attainable. Q

I have discovered .that' an electric discharge from an incandescent cathode in thevapor of an alkali metal at pressures below about fifty microns of mercury (0.05 mm. Hg.) and preferably within a range of vapor pressure corresponding to' temperatures between about 200 to 300 0.11098 not cause the cathode to disintegrate or sputtelnf What is still more remarkable, the

cathode does not disintegrate even when the Y discharge is operated atv commercial voltages, that is, over one hundred volts and with relatively large currents, say, over 100 milliamperes.

- stable voltsampere characteristic when the applied voltage is within this range and the current is relatively large. The currentincreases with a rising voltage up to a limiting value, and thereafter remainssubstantially constant over a relatively wideirange of voltage. This discharge has a high luminous efliciency, a large part of the energy being emitted in the visible portion of the spectrum. It does not requ re an energyconsuming, steadying resistance, and therefore may be operated in shunt to an incandescent filament to constitute a lamp of 'high efficiency. J E

These and other novel features of my invention will be pointed out with particularity in the appended claims. For a complete understanding of my invention, reference may be had to the. following description taken in connection with the accompanying drawings.

Figs. "1 and 2 illustrate somewhat d ia grammatically two embodiments of my, m-

vention; Fig. 3 is a modification having a The discharge has adouble-walled container to reduce heat dissipat1on,'and Fig. 4 is a dia am of, the volt-ampere characteristics 0 thermionic dischar es-in sodiumvapor.

The evice illustrated by Fig.2 comprises material'not readily acted uponchemically by the filling material, for example, the refractory bore-silicate known in the market a'sealed envelope 5 cofisistingofa suitable as Pyrex glass; The cathode 6 consists of a coiled filament of refractory material, such, for exatrTple, as tungsten. It is provided with leading-in conductors 7 8,

sealed into the envelope whereby current may be supplied to the filament to heat the same to incandescence. The anode 9 consists preferably of'tungsten although various conductivematerials also may be used. A'leading-in conductor '10 forthe anode is sealed into the envelope in the usual manner.

In preparing the device, the envelopeis thoroughly exhausted the glass being heated during exhaust nearly to its softening point A quantity of pure to remove water vapor. sodium is introduced into thebulb. after residual gases and vapors have been removed, .as far as possible, and the bulb thereupon is sealed off. Preferably the process of exhaust is carried out by first introducing a small amount of sodium Into a dried and exhausted bulb, heating the bulb and expelling the sodium vapor. ThlS quantity of purified and redistilled sodium is introduced and allowed to remain in the bulb. The bulb is operated at a temperature high enough tovolatilize' a portlon of" the sodium and maintain the pressure of the sodium vapor high enough to be iomzed by the electron discharge and within the range throughout which the discharge has stable process may be repeated. Finally a desired characteristics. Preferably the bulb should be maintained within a range ofabout 200 to 300 C. This temperature may be 'obtainedby proportioning the bulb so that the dissipation of heat under ordinary external conditions is adjusted to ma ntam the temperature within the desired range, or the bulb' may be heated or cooled externally to maintain the temperature within the desired range.

With the cathode at. a suitably high temperature, the application of current of suitable voltage to the electrodes produces a brilliant glow in the bulb of the yellowish tint characteristic of the sodium spectrum.

'A peculiar characteristic of the glow is of the order of a tenth the uniform distribution of luminescence throughout the bulb which may be due to optical resonance effects in the sodium vapor. The light eificiency of the glow appears to be very high. It is approximately of a watt per candle. The presenceof the ionized vapor greatly increases the current-carrying capacity the device by substantial elimination of the current limiting effect of the negative" field i operating of the electrons on each other which is usually known as space charge. For example, a given devicecarrying in the substantial absence of positive ionization about three milliamperes at 125 volts carries in the presence of sodium vapor at a suitable pressure a current of about 500 milliamperes at the same voltage. temperature in these devices should correspond to a luminous efficiency of about one then remains substantially constant with further increase of voltage over a wide range until a second increase of current occurs when the discharge characteristic becomes negative, as indi-- cated by the dotted line. From zero to a limiting value of voltage on, the discharge is stable without a series resistance, as the current cannot increase without a rise of applied voltage. Above the voltage 00. the discharge becomes unstable. An attempt 'to increase the voltage further results in an arc-like or runaway discharge in which the current increases with a corresponding I decrease of voltage across the terminals of the discharge electrodes.

When the temperature of the device is increased, and hence the pressure of sodium vapor is increased, the critical point of instability corresponds to lower voltage values, that is, the operating ran e of the device is contracted. At a su ciently high pressure of sodium vapor, corresponding, y: rent voltage characteristic of the deviceis negative at ordinary commercial voltage and is similar to the characteristic of incan- Ordinarily the cathode Asillustrated by this curve the "current rises rapidy with an increase of voltage from .zero,

to a temperature above 400 C. the our descent cathode devices operated in other f vapors or gases at relatively considerable pressures.

The device shown in Fig. 2 may be used as a rectifier of alternating currents or as a lamp. v i v .Fig. 1 illustrates a, lamp embodying my invention containing a looped filament 14 consisting of tungsten, or other suitable refractorymaterial, and supported upon a framework comprising a stem 15 upon which are mountedtwobuttons 16, 17 ,in which are embedded hooks 18 upon which the filament is supported. The stem 15 and.

the hooks 18 consist preferably of a materialv more refractory than glass, for example, such as tungsten, Nichrome or, the like. The buttons 16, 17, in which the hooks 18 are embedded consist either of suitable heatresisting glass or of porcelain. Current connection is made i by conductors 19, 20, consisting of relatively heavy wires composed of tungsten, molybdenum or the like. These wires preferably extend from the seal 21 to the opposite end of the frame-work where'attachment is made to the ends of the filament in the usual manner.- The lamp is exhausted and provided ,with a quantity of metallic sodium, as already described in connection with the device shown in Fig, 2.

When a lamp embodying my invention constructed and prepared as above described is operated in the usual way on either direct or alternating current, a discharge will pass through'theisodium vapor acrosstlie space between the loops of the filaments by reason of the difference of voltage between these filament sections and cause theentire bulb to bepervaded with a brilliant yellow glow.

The amount of light obtained from a glow ably great and depending upon the size of the bulb may emit several times the candle power of the filament. These efl'ects, which are of such a different order from those hitherto observed with gases at such low pressures, may be partly due to the purity of the sodium vapor. The sodium vapor itself seems to'bring this about by cleaning up any traces of foreign gases which may be present.

In an alternatingcuri-ent device the conductors immediately adjacent the leading-in wires have alternately the highest positive otential and act as anode for the discharge and 3, the in conduceby preventa .ijacent the min other morenegatiie filament sections. These sections therefore tend to overheat as ing overheating of the same, .The lamp shown in. Fig. 3 has a double-walled envelope, the space between the twogwalls I preferably being evacuated. This construcby Letters Patent of the United States, is

1. An electrical discharge device comprising a cathode adapted to be heated to incandescence, heating means therefor, an

anode, and means for furnishing, subject to the ionizing influence of an electron discharge between-said electrodes, a gas which .when ionized will leaveisaid electrodes intact from electrical disintegration, said gas having a pressure at which a discharge of stable characteristics ma be produced with currents of the order oi magnitude of 100 milliamperes at voltages materially above the ionization voltage of said gas 2. An electric discharge device comprising a sealed envelope, means for producing therein an ,electron discharge and a sublsaae L 6. An electrical discharge device comprismg the combination of a tungsten cathode, an anode, means for heating said cathode,

an enclosing bulb and aquantity of sodium in said bulb, said lamp being proportioned to maintain the vapor pressure of said sodium below the value at which vthe voltampere characteristic of a'discharge therecombination of an enclosed envelope, a

cathode adapted to opeate at incandescence, an anode, and a quantity of sodi'umin said envelope, said envelope being proportioned to operate at a -temperature 'at which the vapor pressure of said sodium issuificiently high to enable an electric discharge there-- through to ionize said vapor but below the value at which a discharge through said Y device has a negative .voltampere characteristic.

8. An electrical device comprising the combination of a sealed envelope, a cathode v of refractory material adapted to operate at incandescence, an anode and 'a quantity of sodium within said envelope, said device havinga heat dissipating capacity adapted to maintain-said device at a temperature corresponding to a pressure of sodium vastance within said envelope having a prespor less than about fifty microns of mercury.

sure less than about fifty microns of mercury at the operating temperature of said device-and capable of becoming ionized in the space between said electrodes to increase materially the current carryingcapacity of an electrical discharge betweenan incandescent cathode and an anode through sodium vvapor and maintaining the pressure of said vapor at a value at which a luminous discharge is produced having a stable electrical characteristic.

4:. The method of converting electrical en ergy into light which consists in passing an electrical discharge through sodium vapor and maintaining the pressure of saidvapor within the range of vapor pressure of metallic sodium corresponding to temperatures between about 200 to 300 C.

5. An electrical device comprising ,the combination of a sealed envelope, a-refrac- 7 tory cathode adapted to operate at (incandescence, an anode and a quantity of alkali metal within saidenlgelope, said device having a heat dissipating capacity adapted to maintain the vapor pressure of said alkali metal at avalue at which an electrical discharge therethrough has stable electrical characteristics.

. in said bulbwhich' is gaseous at the operat;

ing temperature of the lamp and is capable ofconducting a luminous discharge from an end of said filament when at incandescence to the opposite end, and in parallel with the connecting art without disintegrating said filament, said discharge having a constant current value over a range of voltages.

10. An electric lamp comprising a bulb, a conductor therein capable of conducting current with a voltage drop between termimale of theorder of magnitude of about one hundred volts and a quantity of material therein having at the operating tempera-- ture of the bulb a vapor ressure sufiiciently high to conduct current y a stable electrical dischargeacross the space in said'bulb between; a section of said conductor when at incandescence, and another section havin a positive potential with respect to' said mcandescent' section. ,g r 11. An electric lamp comprising a sealed exhausted container, a quantity of metallic sodium in said container, and a filament of heat generated therein at a rate which will maintain the operating temperature of said vlamp at a value at which the pressure of said sodium is high enough to produce a glow discharge, but below about 300 C. to

avoid the formation of an arc-like discharge 1 a" filament of refractory material therein, a and a uantity of metallic sodium in said bu1b, sa1d .devlcebeing operable with a dis-. charge having a stable electrical characteris- I tic conducted through said sodium in a vaporized' state, in parallel with a portion of.

said filament.-, g

- v14. The method of increasing the current-' carrying'capacity of an electron discharge which consists in maintaining in the path of said discharge the vapor of an alkalrmetal within 'ressure limits sufiiciently high to cause su stantial positive ionization by collision but insufficient to permit of an arclike discharge having a negative volt-ampere characteristic. i

15. An electrical discharge device coinpris ing an evacuated envelope, electrodes therein, means for heating one of said electrodes to' incandescence independently of a dis charge therebetween, an alkali metal contained therein, said device being construct ed to maintain the vapor pressure of alkali -which a discharge througli metal during operation high enough to increase the current carrying capacity of said device, but below the value at which an arclike discharge of negative volt-ampere characteristic may occur.

16. An electrical discharge device comprising a container, cooperating electrodes therein, means for producing an electron discharge between said electrodes, a quantity 'of an alkali metal in said container, and means surrounding said container for maintaining'the temperature of said device at a value at which the metal vapor has a sufficiently high pressure to' permit. substantial positive ionization during operation but:

will not be so high astto permit an arc-like discharge. y

17. An electrical discharge'device comprising a sealed evacuated envelope, a. filamentarycathode consisting of refractory inate rial, terminal conductors therefor whereby a heating current maybe conveyed to said cathode, an anode, I metal in said. envelope, I pro ortioned, when dissipating heat under ordinary external conditions, to operate at a temperature at which the vaporfpresstire of said alkali metal is sufliciently high-to enable an electric dischargetherethrough to ionize said vapor but below the- 'value at aract'efihtie'ia negative volt-ampere c o In witness whereof, I have heiieuntoset .my hand this 22nd day of January 1920.,

GEORGE M. J KAY and a quantity of alkali said device being said d evice has

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