US2275768A - Electric lamp - Google Patents

Description

Y M h 10, 1942. KERN 2,275,768

a ELECTRIC LAMP Filed Nov. 12, 1940 lnven'tors Josef Kern rman Kref'ft,

he'n' Attorneg.

Patented Mar. 10, 1942 ELECTRIC LAMP Josef Kern and Herman Krefi't, Berlin-Schoneberg, Germany, assignors to General Electric Company, a corporation of New York Application November 12, 1940, Serial No.

In Germany June 17,- 1939 4 Claims.-

The present invention relates to electric lamps generally and more particularly the invention relates to such lamps comprising an incandescent filament and a gaseous electric discharge device capable of operation on alternating current with a vapor pressure in the order of atmospheres.

Lamps of the above type are now known in the art which operate directly on commercial voltages and can be mounted in sockets used" for incandescent lamps without .extemal auxiliary apparatus. The practice in the art heretofore has been to operate the discharge device at a vapor pressure of about 1 to 8 atmospheres in series with an incandescent filament of such size that the main part of the line voltage is dissipated in the seriesfilament. This proportioning mospheres, a specific power consumption of morethan 200 watts, preferably more than 300 watts,

per centimeter of arc length and a specific wallload of more than ,20 watts per square centimeter of the inner surface of the container. We prefer to mount the discharge lamp in a vitreous, bulb provided with a screw base and'to connect in series therewith an' incandescible filament, also mounted in the bulb, said filament between the voltage dissipated by the filament and that dissipated by the discharge is made necessary by the fact that the high pressure discharge device has a high reignition peak occurring in each half cycle of the alternating current and the fact that commercial current sources have unavoidable voltage fluctuations. twice the voltage occurring at the electrodes is necessary for insuring reignition of the arc.-

The object of the present invention is to provide an electric lamp of the above type which Thus having a resistance value such that during the operation of the lamp the voltage drop across thefilament'is less than 45 per cent of the line voltage.

In the drawing accompanying and forming part of this specification an embodiment of the invention is shown in a front elevation, partly sectional view.

Referring to the drawing the electric lamp comprises a bulb 2 of vitreous materiaLsuch as glass, having a metal screw base I attached thereto and containing a high pressure metal vapor discharge lamp, an incandescible filament and current leads for said dischargelamp and has a greater light output than those now known in the art. Another object of the invention is to provide a gaseous electric discharge lamp of the high vapor pressure type capable of operation on alternating currentand which has a lower reignition voltage on each half cycle of the alternating current than those now known in the art.

Still further objects and advantages of the invention will be apparent to those skilled in the art from the following detailed description there of and from the appended claims.

We have discovered that the reignition voltage of discharge lamps of the above type decreases with increasing current and voltage gradient. that is, with increasing energy consumption per unit length of the arc path. We have utilized our discovery to provide a new the above type.

The new lamp comprises a discharge device having a vitreous container of high softening point material, such as quartz, providing a spherical or keg shaped discharge chamber of 15 mm. or less insidediameter and having cooperating thermionic electrodes sealed therein. Said electrodes are separated a distance less than 5 mm. The discharge lamp is capable of operation with a vapor pressure greater than 25 atkind of lamp of said filament. The discharge lamp has a'container 3 of vitreous material having a high softening point, such as 'quartz, providing a spherical discharge chamber of about 8 mm. inside diameter. Two cooperating electrodes 5 separated a distance of about 3 mm. are sealed into said con tainer 3. Part of the current leads for said elec-. trodes 5 are imbedded in the stems of the con-r tainer 3 and comprise metal foil, such as molyb J denum foil,'as is well known in this art. Said pressure of about atmospheres.

electrodes 5 preferably consist of small, perfo-' rated tungsten shells, cone shaped in the direc- I tion of the discharge path and containing thorium oxide or zirconium oxide. Other types of activated electrodes known in the art, such as wire helices surrounding or impregnated with activating materials, are used when desired.

, Said container 3 has therein a rare gas, such as argon, at a pressure of about 20 mm. When rapid heating of the device is desired to shorten the time required to attain operating equilibrium after starting the pressure of the gas is increased; A gas pressure of about 400 mm. is effective for this purpose though pressures lowerathan this are useful for the same purpose. A body of mercury 6 is present in-said container, in such amount that when the device is at operating equilibrium the vapor atmo'sphere is unsaturated, and has a The are voltage increases with a rising vapor pressure to about volts and the voltage drop across the filament 6 decreases to about 75 volts. Thus the ment and a gaseous electric discharge device mounted in said bulb, said filament being connected in series with said discharge device and of the discharge device is higher than that of the incandescent filament.

When the arc current is one-half ampere thewattage input is about 72.5 watts which is a specific wall load of about 36 'watts per square centimeter of the inner surface of the container 3 and a specific power consumption of about 250 watts per centimeter of the length of the arc path.

The bulb 2 contains an inert gaseous atmosphere, such as a mixture of argon and nitrogen. When glare is to be avoided a light diffusing bulb 2 is preferred. When the considerable ultra violet light output of the discharge device is desired for utilization external to the lamp the bulb 2 is made of a vitreous material capable of transmitting such radiation. When the lamp is used for purposes of illumination we prefer to coat the inner surface of the bulb 2 with luminescent powder 1 or to make the bulb 2 of a luminescent glass.

When desired another series resistance of the type which automatically decreases in value during the starting period is mounted in the bulb 2 or in the base I to prevent excessive currents inthe lamp when potential is first applied thereto. It will be understood, of course, that where prior devices for lowering the reignition voltage, such as auxiliary electrodes or electrically conducting strips, are used in the new lamp, the operating.

voltage of the discharge device can be increased still further.

1 While we have pointed out in the annexed claim certain novel features of the invention, it will be understood, of course, thatvarious modifications and changes in theform and details of the lamp described above and illustrated in the drawing may be made by those skilled in the art without departure from the spirit and scope of the invention.

What we claim as new and desire to secure by Letters Patent of the United States is:

1. An electric lamp capable of operating, on

alternating current and comprising in combination a sealed bulb of vitreous material, gaseous electric discharge device and ohmic resistance means mounted in said bulb said means being connected in series with said device and constituting the sole ballast means therefor, said discharge device having a vitreous container providing a spherical discharge chamber which is 'not more than mm. in diameter, a pair of constituting the sole ballast means therefor, said discharge device having an ultraviolet ray transmitting vitreous container providing aspherical discharge chamber which is not more than 15 mm. in diameter, a pair of spaced, cooperating electrodes sealed into said container and sepa rated a distance of less than 5 mm. from each other, a starting gas and a quantity of mercury in said container, said discharge device being capable of operating with a vapor pressure of at least 25 atmospheres, a specific current load of more than "200 watts per centimeter of length of the arc 'path and a specific wall load of more than 20 watts per square centimeter of the inner surface of the container, the operating voltage of said device being more than 55 per cent of the voltage applied across the terminals of said lamp when said device is at operating equilibrium. l

3. An electric lamp capable of operating on alternating current and comprising in combination a sealed bulb of vitreous material, anincandescible filament and a gaseous electric discharge device mounted in said bulb, said filament being connected in series with'said discharge device and constituting the sole ballast means therefor, said discharge device having an ultraviolet ray transmitting vitreous container providing a spherical discharge chamber which is not more than 15 mm. in diameter, a pair of spaced, cooperating electrodes sealed into said container and separated a distance of less than 5 mm. from each other, a starting gas and a quantity of mercury in said container, said discharge device being capable of operating with a vapor pressure of at least25 atmospheres, a specific current load of more than 200 watts per centimeter of length of the arc path and a specific wall load of more than 20 watts per square centimeter of the inner surface of the container, the operating voltage drop across said filament b'eing more than per cent of the voltage applied across the terminals of said lamp when said device is at operating equilibrium and luminescent material supported by said bulb.

4. An electric lamp unit comprising in combination, anohmic ballast resistance means and a gaseous electric discharge lamp device con-' nected in series therewith, said resistance means constituting the sole ballast for said device said discharge device having a vitreous container providing a spherical discharge chamber not more than 15 mm. in diameter, spaced, cooperating electrodes sealed into said container and separated a distance of less than 5 mm., a starting gas and a quantity of vaporizable metal in said container, said discharge device being capable of operating with a vapor pressure of at least 25 atspecific wall load of more than 20watts per square centimeter of the inner surface of the container, the operating voltage of said device mitting vitreous material, an incandescible filamospheres, a specific current load of more than 200 watts per centimeter of length of the arc path and a specific wall load of more than 20 watts per square centimeter of the inner surface of the container, the reignition voltage of said discharge device being so low that the device is successfully operated even when the operating voltage thereof: is more than 55 per cent of the voltage applied to said lamp unit when said vdevice is at operating equilibrium.

JOSEF KERN. HERMANN KREFFT.

CERTIFICATE or comcmon. i 3 Patent No. 2,27 ,768. a n 10, 1911.2.

JosEF KERN, ET AL It is hereby certified that error appears in the printed specification of the above numbered patent requiring correction as follows: Page 2, 590-. 0nd column, line 14.5, claim 5, for "drop across said filament" read of said device--; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed thie 20th day of October, A. 1)., 191 .2.

Henry Van Arsda le, (Seal) Acting Commissioner of Patents.

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