US2424457A

US2424457A - Gaseous electric discharge lamp

Info

Publication number: US2424457A
Application number: US556559A
Authority: US
Inventors: Haynes Howard; Jr Lynn S Ickis
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1944-09-30
Filing date: 1944-09-30
Publication date: 1947-07-22
Anticipated expiration: 1964-07-22

Description

y 1947. H. HAYNES ETAL 2,424,457

' GASEOUS ELECTRIC msdms LAIP Filed Sept. 30, 1944 mmmmwma I N VEN TURF- HUWARD HAYNES LYNN j [CKIS JP.

' THE/R A TTURNEY Patented July 22, 1947 Howard Haynes, Wllloughby, andLynn S. Ickis,,

Jr., East Cleveland, Ohio, auignors to General Electric Company, a corporation of New York Application Sept. :0, 1944, serial No. asse 12 Claims. 176-425) Our invention relates; to gaseous electric discharge devices.

Certain types of gaseous electric discharge lamps, such as hot or thermionic cathode fluorescent lamps now in extensive use and employing activated filamentary electrodes at the ends of an elongated tubular envelope, are started by passingcurrent through the electrodes to preheat them before application of a potential.

higher than the operating potential of the lamp to initiate the discharge between the electrodes. This type oflamp is incapable of starting at the voltages applied thereto in the event the electrodes have become deactivated. Repeated flashing of the lamp in unsuccessful attempts to start is obviated by employing a suitable cut-out switch which opens the circuit therethrough, so that the lamp merely remains unlighted to indicate the need for replacement.

However, certain other types of lamps employing activated thermionic electrodes are started "cold," that is, the electrodes are not preheated as described above. This type of starting necessitates the use of higher voltages, and the lamps do not extinguish themselves at the end of life as determined by electrode deactivation, particularly on high voltage circuits (such as those commonly used in installations of the "neon sign tube type), but continue to operate with abnormal heating of all metal parts of the electrode. trode may result in violent failure (such as shattering of the envelope) or damage to the socket.

Oneof the objects of our invention is to prevent such continued overheating of the electrode by extinguishing the discharge. According to our invention this is accomplished by utilizing the abnormal heat to effect introduction into the envelope of an atmosphere which is capable of quenching the discharge, or to put it another way, an atmosphere which is incapable of supporting a discharge between the electrodes. Further objects and advantages of our invention will appear from the following detailed description of species thereof and from the drawing.

In the drawing, Fig. 1 is a sectional view of one end of a gaseous electric discharge lamp embodying our invention; Fig. 2 is a partial section of a, modification, the left hand end of the lamp being shown as rotated about its longitudinal axis somewhat as compared to its right hand end; and Fig. 3 is a sectional view of one end of a further modification.

Referring to Fig. 1, the lamp shown therein is of the positive column type comprising an elon The continued overheating of the elecgated tubular glass envelope i which may be coated interiorly with a suitable fluorescent material and which contains a suitable gaseous atmosphere, such for example, as a few millimeters of argon and a small quantity of mercury. A terminal contact member in the form of a disc or cap 2 of sheet metal, such asa chrome-iron alloy known as "Allegheny 55, is sealed by fusion directly to each end of the envelope. The form of disc illustrated is like that disclosed in Patent 2,146,579, G. E. Inman, wherein the disc is inwardly embossed at 3, and is provided with an aperture 4 through which the envelope is exhausted and then filled with its gaseous atmosphere through a glass exhaust tube, the said aperture being subsequently sealed by the residue 5 of the exhaust tube.

At each end of the envelope is an activated filamentary electrode 6 consisting, preferably, of a coiled tungsten wire activated by a coating of alkaline earth oxides. The electrode 6 is supported from and electrically connected to the disc 2 by a comparatively rigid wire I one end of which is coiled around the embossment 3, as shown at 8. If desired the end 8 of the wire i may be welded to the disc 2. The other, or free, end 9 of the wire I is shaped in the form of a U which preferably lies in a plane including the iongitudinal axis of the envelope l. The extremity of the wire 1 is formed into a hook ill in which one end of the electrode 6 is clamped, while an intermediate portion thereof is doubled back upon itself in an S-shape to form a hook in which the other end of the electrode is clamped.

The U-shaped portion 9 of wire 1, togetherwith the electrode 6, thereby form a closed loop, so

that when the end of the lamp is inserted in the coil of a high frequency oscillator, the loop permits the induction of currents suflicient to heat the electrode 6 and activate it by converting the original coating of alkaline earth carbonates to the corresponding oxides, preferably during evacuation of the envelope. The loop is located in the lamp in a, plane perpendicular to the high frequency field. When necessary, a small wire 12 is threaded through the electrode coil to reduce the resistance of that part of the loop to a value only slightly higher than that of the remainder of the loop.

The. lamp is operated by connecting it across any suitable source of electric energy which, for long lamps, may be a. high voltage transformer such as those commonly used in "neon" sign type installations. The discharge strikes through the gaseous filling between the electrodes 8 at the 3 ends of the envelope. The electrodes are rapidly heated by the discharge to an electron-emitting temperature. As long as the electrodes remain properly activated, the ends of the lamp are not unduly heated. However, when an electrode 6 becomes deactivated by loss of activating oxides, although the current remains substantially the same, the voltage drop in the discharge increases with a resulting increased wattage, and the support wire I becomes highly heated, with the resuit that the envelope I may crack and be shattered, or sufficient heat maybe conducted through the disc 2 to fuse it to the socket in which the lamp is mounted, or otherwise damage the socket.

According to this invention, such action is eliminated by introducing into the lamp a gas capable of extinguishing the discharge therein. In the form shown in Fig. 1, we provide within the envelope, a sealed ampule or capsule l3 which is attached to the support wire I by a wire H.

The ampule I3 is made ofa material, or of such form (a locally weakened portion, for example), that it is ruptured upon continued overheating.

of the electrode and its supporting structure, thereby evolving a gas capable of extinguishing the discharge in the lamp. To this end, the ampule may be made of a glass which softens at the abnormally high temperature then existing in the lamp. Y

The ampule I3 may be filled with an inorganic material which decomposes at the temperature of the electrode and its supporting structure after deactivation of the electrode. The ampule is then submitted to high pressure, and by selecting a glass for the ampule which softens at those high temperatures, the ampule will open and introduce the products of decomposition into the arc stream to extinguish the discharge.

As an inorganic filling material for the ampule I3, we prefer at present to use the ammonium sulphate (NH4)2SO4. However, we have successfully used ammonium acetate, NH4C2I-BO2; ammonium phosphate, (NHozHPOl; and sodium bisulphate, NaHSOr. These substances are effective even in lamps operating on high voltage circuits. It will be noted that these substances are characterized by the fact that they break down to form water vapor as one of the products of decomposition. However, in lamps operated on low voltage circuits, successful results may be obtained with gaseous fillings such as hydrogen, air, CO2, C1, and S02.

The left hand end (not shown) of the lamp shown in Fig. 1 may be of the same construction corresponding disc 2 need not be provided with an exhaust aperture 4 and tubulation 5.

In the form shown in Fig. 2, the right hand end of the lamp is provided with an internal tubular glass appendage l5 which is sealed at its inner end but has its outer end in communication with. the atmosphere. Although the appendage may be attached to the envelope l, we prefer to fuse its outer end to the disc 2 around the aperture 4. An intermediate portion'of the wire I is coiled around the appendage IS. The left hand end of the lamp contains a similar appendage l5 which is fusedaround a supplementary aperture 4' in disc 2 since that end of the lamp is evacuated through aperture 4, although, of course, the appendage could be attached around aperture 4 and the exhaust tube around aperture 4f.

In thev Fig. 2 lamp, deactivation of anelectrode 6 with resultant overheating, causes an appendage I! to be punctured, usually at a point under a portion of the wire I in contact therewith, thereby admitting the ambient atmosphere into the envelope with the result that the discharge is extinguished.

In Fig. 3 the lead-in wire'l is provided with a bent V-shaped portion 16 with its bight engaging the wall of the envelope I. In this case, overheating of the electrode 6 and wire 1 causes the envelope l to be punctured at the point engaged by the portion iii of wire I, thereby admitting air into the envelope to extinguish the discharge. A number of tests have demonstrated that a small puncture is produced in this way without shattering the envelope or cracking it around its circumference.

It will be' apparent to those skilled in the art that various modifications, omissions and substi- .as the right hand end with the exception that the tutions may be made within the scope of our invention.' We have successfully applied the invention, as illustrated in the several modifications disclosed herein, to elongated tubular fluorescent lamps of the low pressure mercury vapor type which operate at low temperatures.

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

1. A gaseous electric discharge lamp comprising a sealed glass container containingspaced electrodes at least one of which is activated, said container being subject to uncontrolled fracture upon overheating at the activated electrode due to deactivation thereof, and means sensitive to such overheating and effective to cause introduction into the container, rior to such uncontrolled fracture thereof, of a gaseous .material having a quenching effect upon the discharge.

2. A gaseous electric discharge lamp comprising a sealed glass container containing spaced electrodes at least one of which is an activated thermionic electrode carried by a lead-in conductor, said container being subject to uncontrolled fracture upon overheating at the activated electrode due to deactivation thereof, and means including said lead-in conductor for effecting introduction into the container, upon overheating of said conductor and prior'to such uncontrolled fracture thereof, of a gaseous material having a quenching effect upon the discharge.

3. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least one of which is activated, and an ampule adjacent the activated electrode and sealed from the atmosphere within said container but rupturable upon overheating at said electrode due to deactivation thereof to release a gaseous material having a quenching effect upon the discharge.

4. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least one of which is activated, and an ampule adjacent the activated electrode and. sealed from the atmosphere within said container but rupturable upon overheating at said electrode due to deactivation thereof and containing an inorganic salt which decomposes to yield a gaseous material'having a quenching effect upon the discharge.

5. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least one of which is activated, a support wire for said electrode, an internal hollow appendage on said container sealed from the atmosphere within the container but open to the external atmosphere, a portion of said support wire beingin engagement with said appendage and adapted to puncture said appendage upon overheating thereof due to deactivation of the electrode to admit .the surrounding atmosphere into the lamp and thus quench the discharge therein.

6. A gaseous electric discharge lamp comprising a sealed glass envelop containing spaced electrodes at least one of which is activated, and a support wire for said electrode having an intermediate portion thereof bent so that its bight engages the envelope wall and is adapted to puncture said wall upon overheating of said wire due to deactivation of said electrode.

7. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least one of which is activated, supports for said electrodes, said container being subject to uncontrolled fracture upon overheating at the activated electrode due to deactivation thereof, and means associated with the activated electrode support and operable upon overheating of the said electrode and its support due to'deactivation of an electrode for introducing into the discharge electrode support to be ruptured byheat there-- from.

8. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least oneof which is activated, and 'a sealed ampule adjacent the activated electrode and rupturable upon overheating at said electrode due to deactivation thereof and containing an ammonium salt which is stable at the normal operating temperature of the lamp but upon such overheating decomposes to yield a gaseous material having a quenching effect upon the discharge.

9. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least one of which is activated, and a sealed ampule. adjacent the activated" electrode and rupturable upon overheating at said electrode due to deactivation thereof and containing ammonium sulphate salt which decomposes to yield a gaseous material having a quenching effect upon the discharge.

10. A gaseous electric discharge lam comprising a sealed container containing spaced electrodes at least one of which is an activated thermionic'electrode, and a sealed ampule containing a compound which is stable at the normal operating temperature of the lamp but which decomposes at higher temperatures to yield a gaseous material having a quenching eifect on the discharge in the lamp, said ampule being located adjacent the activated electrode and being rupturable upon overheating at said electrode due to deactivation thereof.

11. A gaseous electric discharge lamp comprising a sealed container containing spaced electrodes at least one of which is an activated thermionic electrode carried by a lead-in wire, and

a sealed ampule containing a, compound which. .is stable at the normal operating temperature of the lam but which decomposes at higher temperatures to yielda gaseous material having a quenching effect on the discharge in the lamp,

said ampule being mounted on said lead-in Wire adjacent the activated electrode and being rupturable upon-overheating at said electrode due to deactivation thereof. r

12. A gaseous electric discharge lamp comprising a sealed tubular glass container having sheet metal terminal members sealed to itsends and.

constituting the end walls therefor, an activated thermionic electrode at each end of the container carried by a lead-in conductor mounted on the adjacent terminal member, and a sealed ampule containing a compound which is decomposable at temperatures above the normal operating temperature of the lamp to yield a gaseous material having a quenching effect on the discharge in the lamp, said ampule being located adjacent the activated electrode and rupturable upon overheating at said electrode due to deactivation thereof.

HOWARD HAYNES. LYNN S. ICKIS, JR.

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

UNITED STATES PATENTS Switzerland Sept. 16, 1935