US1648677A - Incandescent electric lamp - Google Patents

Description

Patented Nov. 8, 1927.

UNITED STATES PATENT OFFICE.

JAN HENDRIK DE BOER, OF EINDHOVEN, NETHERLANDS, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

INCANDESCENT ELECTRIC LAMP.

No Drawing. Application filed November 2, 1926, Serial No. 145,914, and in the Netherlands December 12,

This invention relates to electric incandescent lamps and more particularly to vacuum lamps provided with a tungsten filament. 1n the burning of the lamp the tungsten vaporizes and deposits upon the inner walls of the lamp bulb, resulting in a harmful and undesirable absorption of light.

Many ways have been suggested for diminishing such loss and absorption of light. For instance, certain substances known as getters can be disposed upon the internal.

walls of the lamp bulb or globe. The tungsten deposited by the vaporization of the filament upon the lamp bulb combines with these substances and assumes a form in which less light is absorbed during the burning of the lamp than would be the case if the lamp bulb were not covered by the getter. this purpose various fluorides have been used, for instance, calcium fluoride.

Applicant has found that the effectiveness of the getters heretofore suggested and known is much enhanced by disposing a small quantity of one or several salts of hydrofluorboric acid upon the inner walls of the lamp bulb.

According to the present invention, a salt of hydrofluorboric acid, either alone or mixed with other fluorides or other getters, for instance, boric acid, is brought into the electric lamp bulb. Particularly good results are obtainable by the use of potassium borofluorides.

The substances above referred to can be applied in any well known way, for example, by spraying or squirting an alcoholic solution or suspension upon the filament before it is sealed into the bulb, the getter being precipitated or deposited upon the lamp bulb by incandescing the filament after the bulb has been sealed.

To compare the getter action of calcium fluorides and potassium borofluoride, it is convenient to use a curve which shows the decrease in the amount of current during the life of the incandescent lamp as a function of the decrease in candle-power,

For

For a better understanding of what has ust been stated, it may be mentioned that the decrease in amount of current is the consequence of the vaporization of the tungsten whereby the wire is attenuated. The decrease in candle-power or luminosity on the other hand is caused both by the effect of decrease in current strength, and by the abing a potassium borofluoride getter; in other words, in the presence of equal decrease in current strength and therefore of equal quantities of vaporized tungsten, the corresponding decrease in candle-power is greater when calcium fluoride is used than when potassium borofluoride is employed.

To further illustrate what has been pointed out above, the following practical figures may be cited. In the presence of a decrease of current strength of 3%, the reduction in candle-power is approximately 9.8% when calcium fluoride is used, while with the use of potassium borofluoride it amounts to about 4.6%. After the decrease in current has reached 7%, the corresponding loss in candlepower amounts to 24.8% approximately with the use of calcium fluoride, and to 19.4% with the use of potassium borofluoride.

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

1. An incandescent electric lamp comprisinga tungsten filament and a sealed bulb having a salt of hydrofluorboric acid distributed in it to hinder absorption of the light by vaporized tungsten.

2. An incandescent electric lamp comprising a sealed bulb, a tungsten filament in said bulb, and potassium borofluoride distributed on the inner Wall of said bulb to hinder abing a tungsten filament and a sealed bulb sorption of the light during operation of the containing a getter material comprising a 10 lamp. salt of hydrofluorboric acid positioned in 3. An incandescent lamp comprising a said bulb to be activated and act as a getter sealed bulb, a tungsten filament in said bulb, when said lamp is lighted.

and a getter on said filament comprising a In witness whereof, I have hereunto set salt of hydrofluorboric acid. my hand this 13th day of October, 1926.

4. An incandescent electric lamp compris- JAN HENDRIK DEBOER.