US2560953A

US2560953A - Electric gaseous discharge device electrode

Info

Publication number: US2560953A
Application number: US102304A
Authority: US
Inventors: Horace H Homer
Original assignee: Sylvania Electric Products Inc
Current assignee: GTE Sylvania Inc
Priority date: 1949-06-30
Filing date: 1949-06-30
Publication date: 1951-07-17
Anticipated expiration: 1968-07-17

Description

y 17, 1951 H. H. HOMER 2,560,953

ELECTRIC GASEOUS DISCHARGE DEVICE ELECTRODE F1106 June 30, 1949 5 II N u 6 R II H/ F6 2 INVENTOR.

Horace f7omer LZZWM ATTORNEY Patented July 17,1951

UNITED STATES PATENT OFFICE.- ELECTRIC GAsgloEfigizggwGE DEVICE I Horace 1!. Homer, Arlington, Mass., assignor to.

Sylvania Electric Products Inc., Salem, Mass a corporation of Massachusetts 7 Application Lime so, 1949, Serial No. 102.304

2 Claims. (Cl. sis-17s) This invention relates to electric gaseous discharge devices and more particularly to.fiuorescent lamps.

In the manufacture of electric gaseous discharge devices, and more particularly in the manufacture of fluorescent lamps of the hot cathode" type, i. e., those in which the electrode comprises a coiled filament of tungsten wire, such as that shown in U. S. Patent 2,258,158,."for example, the electrodes are usually provided with a coating of an electron-emissive material. In the case of a fluorescent lamp electrode, the electron-emissive material usually comprises an oxide of one or more of the alkaline earth metals. For convenience, the alkaline earth metals are usually appliedin the form of a carbonate hich breaks down to the oxide when the lamp is processed.

During the operating life of fluorescent lamps. an objectionable discoloration frequently appears on the wall of the lamp near the ends thereof and in proximity to the electrodes. One form which this discoloration may assume is a. light yellow, brownish or black ring or band which usually extends completely around the periphery of the inner wall of the lamp. This particular discoloration is usually defined by a sharpedge on the side near the electrode and a diffused edge on the side near the longitudinal eenter of the lamp. These rings or hands are usually found forward of the electrodes withthej sharp edge located adjacent to an end of the positive column or plasma. 7 jAn object of this invention is to retard the development of this discoloration.

' Further objects, advantages and features will be apparent from the following description when read in conjunction with the accompanying drawing in which:

Figure 1 is a side elevational view of a fluorescent lamp with an end thereof broken away. showing the electrode mount structure.

Figure 2 is an enlarged fragmentary detail of the electrode mount structure shown in Figure 1.

In Figure l, the lamp I comprises an elongated tubular glass envelope 2, the inner wall of which is provided with a coating 3 of fluorescent material, and electrode mounts 4 (one of which is shown) sealed in the ends thereof. Each electrode mount comprises a glass stem 5 having a flared portion 6 which is sealed to the glass envelope 2, a press I through which lead wires 8 are sealed, and a filamentary electrode 9 of tungsten wire mounted on the lead wires. At least one of-the stems 5 is provided with an aperture 'ZrLsmps I. therein to which an exhaust tube (not shown) is connected to permit evacuation of the lamp envelope during processing. The sealed envelope is provided with a filling of inert gas at low pressure, such as argon at about 3 mm. and a small quantity of mercury II.

The filamentary electrode 91s a tungsten wire which has been coiled once to define a' primary coil and then a portion thereof intermediate the ends is coiled again to define a secondary coil. A quantity of electronemissive material .12, such as an oxide of one or more of the alkaline earth metals, is disposed primarily within the turns of that portion of the primary, coil which has been provided with a secdndary coiling. The electrode 9 is supported on lead wires 8 by clamping or welding the lead wires 8 to the ends or legs II of the primary coll thereof.

I have discovered that the development of discoloration on the wallof the lamp envelope during life can be arrestedsubstantially-by providing the legs I! of the filamentary electrode with a reservoir of powdered zirconium is preferably disposed within the turns thereof. Table I below illustrates this quite clearly. This table reflects the results of a test in which'the legs of the filamentary electrodes of several lamps were provided with the powdered zirconium and the legs of the filamentary electrodes of several other lamps were not so provided. The former are identified as Zr lamps"; the latter as controls.- The discoloration at the end of varioushours of burning is in terms of arbitrary relative-unit's.

Table I Discoloration at- 100 Hours 600 Hours 875 Hours 2. 5 7. 6 Controls 0 2i. 3 4,3. 3

I have found that the location of the powdered zirconium on the filamentary electrode mount is quite critical. For example, when powdered zirconium is placed on the lead wires instead of on the legs of the filamentary electrode, the lamps are hard to start, their brightness is diminishcd,

' and the color of the light emitted is affected.

The powdered zirconium is applied to the legs of the filamentary electrode in the form of a suspension thereof in a suitable medium. For example, it may be prepared by adding powdered zirconium to a solution of borated silica in isopropyl alcohol.

The borated silica, hereinafter referred to as solution A, is prepared by adding an excess of anhydrous B203 to isopropyl alcohol, agitating in a closed vessel for about 24 hours, and filtering. The filtered solution should contain not less than .03 gram B20: per cc. of alcohol. This is solution A. o

A second solution, hereinafter referred to as solution B, is prepared by slowly heating 100 cc. of ethyl silicate with 40 cc., of .6N HCl and constantly stirring the same until completion of the reaction. Completion of the reaction has beenv eflected when the initial two phase solution becomes one phase; at the same time there is an evolution of heat and fine bubbles. Solution A is then added in the ratio of three parts of solution A to one part of this solution. This mixture is then permitted to stand for about 24 hours and is then decanted. The decanted solution is solution B.

The solution of powdered zirconium, which is applied to the legs of the electrode, is prepared by adding powdered zirconium to a mixture of solution A and solution B in the following pro portions: powdered zirconium 500 grams; solution A 110 cc. and solution B 40 cc. However 1 othersuitable suspension media and binders may be employed without departing from the spirit of the invention.

In the preferred embodiment of my invention the suspension of powdered zirconium is uniformly distributed and completely fills the interstices of the legs of the electrode. However, this condition is not necessary for the attainment of all the beneficial effects of my invention.

What I claim is:

1. An electric gaseous discharge device electrode comprising: a tungsten filament having coiled legs, and a coiled coil portion intermediate the legs; a quantity of electron-emissive material on said coiled coil portion; and a quantity of powdered zirconium within the interstices of said coiled legs only of said filament.

2. An electric gaseous discharge device comprising: an elongated sealed glass envelope; a

filling of inert gas at low pressure in said envelope; a small quantity of mercury in said envelope; a tungsten filament in said envelope at each end thereof, each filament having coiled legs and a coiled coil portion intermediate the legs; a quantity of electron-emissive material on said coiled coil portion; and a quantity of powdered zirconium within the interstices of said coiled legs only of said filament.

HORACE H. HOMER.

REFERENCES CITED The following references are of record in the file of this patent: 1

UNITED STATES PATENTS 2,462,837 Braunsdorfi Mar. 1, 19.49