US2373219A - Electric fluorescent lighting device - Google Patents

Description

April 10, 1945. o. R. BESSER I 2,373,219

ELECTREG ELUORESCENT LIEHTINQ DEvIcE Filed A115425, 1941 llllil INVENTOR. 0770 RICHARD BESSER BY M Patented pr. l10,1945

` UNITED STATES" PATENr OFFICE ELECTRIC FLUORESCENT LIGHTING DEVICE om Richard Bessr, Maspeth, N. Y.

Application August Z3, 1941, Serial No. 408,037

10 Claims.

This invention relates "to electrodes and more particularly to electrodes whichare adapted to be employed with cold fluorescent electric lighting tubes.

The voltages required to initially strike an arc through an :ionizable gaseous medium between f a pair of electrodes vary with the different mabeen extensively employed for this purpose, the

high striking voltage required by such electrodes has necessitated the use loi special equipment and has greatly restricted the employment of cold fluorescent electric lighting. `\g

Attempts have been made to utilize the low striking voltage of electrodes composed of materials such as tungsten in conjunction with ferrous operating electrodes. In these attempts either the tungsten striking electrode and the ferrous operating electrodes have been in separate electrical circuits, or they have been directly electrically connected.

In the first instance, switching equipment is required, whereby after an arc has been initially struck through the gaseous, ionizable medium, potential is removed from the starting electrodes and a proper operating potential applied to the ferrous operating electrodes. lThe tungsten starting electrodes have thus been subjected to oper-` ating conditions whichcaused same to deteriorate before potential was removed therefrom. Moreover, such switching equipment added materially to the expense of installation.

In the second instance, the tungsten electrode. after the tube had commenced to operate.' carried sufficient potential to allow an operating current to flow therethrough, and the tungsten electrode therefore quickly deteriorated during use of the tube.

- It is, therefore, an object of my invention to provide la combined starting and operating electrode of the character 4described wherein the starting electrode will be automatically cut out without the use of switching equipment when the fluorescent tube has `commenced to operate.

Another object oi my invention is to provide a starting and operating. electrode 4of the character of a fluorescent tube the starting electrode will be automatically cut out without the use of switching equipment.

A further object of my invention is to provide a starting and operating electrode of the character described wherein a resistance under the operating conditions of the fluorescent tube will decrease the potential applied to the starting electrode below its operating potential.

Still another object of my invention is to provide a starting and operating electrode of the character described which shall be rugged in construction and efficient in operation to a high degree.

Other objects of this invention will in part be obvious and in part hereinafter pointed out. y 'The invention accordingly consists in the features of construction, combinations of elements, and arrangement of parts which will be exemplified in the construction hereinafter described, f and of which the scope of application will be indicated in the claims.

lIn general, I accomplish the objects of my in-` vention byproviding an operating electrode of standard construction, such as for example the steel cup electrode now commonly used inl cold fluorescent electric lighting tubes. Connected in parallel with the'operating electrode is a tungsten starting electrode. y -diate the operating and starting electrodes is a resistance of such nature that when cold it is of a low ohmage and when heated during operation of the tube its ohmage will become sufficiently large to cut down the potential applied to the tungsten starting electrode 4below the operating potential for tungsten. I

The heat utilized to raise the temperature of the intermediate resistance may initially be conveniently obtained from the current flowing through this resistance when starting the tube. Subsequently and during the operation of the tube, the heat is obtained from the hot operating electrode. It will be understood, however, that I described wherein under the operating conditions 55 do not desire to be limited to this method of raising the temperature of the intermediate resistance. and that I contemplate the use of any other means, such as a separate heating element, to

raise the intermediate resistance to and maintain Fig. 1 is a sectional'view at starting-through a I fluorescent electric lighting tube employing my Series-connected intermenovel electrodes and additionally schematically indicating the electric supply circuit therefor; and

Fig. 2 is a sectional view through one end of said tube during operation.

Referring now in detail to the drawing, I is a cold fluorescent electric lighting appliance employing my invention. Said appliance comprises an open-ended elongated glass cylinder I I, whose inner surface is suitably coated in any manner well known to the art with a fluorescent substance I2 which is luminously activated by the passage of current through a gaseous ionlzable medium contained within the cylinder. The ends of the cylinder I I are sealed off by glass plates I3, whose periphery is hermetlcally fused to the edges of the said cylinder.

Centrally embedded in and extending` completely through the plate I8 are a pair of electrically conductive heavy mount wires Il and I5.

The exterior portions of the mount wires are employed as supply terminals for the tube. To the ends of the interior -portions of the mount wires are welded cup electrodes I8 made from a ferrous material, such as for example "Svea metal, which consists of highly pure steel having a very small percentage of carbon. This cup electrode will hereinafter be referredk to as the operating electrode. The dimensions of the operating electrode are controlled, as well known in the art, by such factors as the spacing between the electrodes, .the diameter of the cylinder, the desired wattage and luminosity and the nature and constitution of the fluorescent coating I2 and ioniz able gaseous medium.

The starting electrode comprises a tungsten wire Il whose major central portion i8 is formed.

The helices I8 and 2| are preferably oppositely convoluted so that their magnetic fields tend to neutralize each other and thereby minimize interference with nearby radio receivers. 'Ihe helix 2| should be so dimensioned and the wire from which it is formed so selected that its resistance, whencold, is negligible and will not lower to below starting voltage, the potential applied to the tungsten starting electrode I1, and furthermore so that as soon as or shortly after an operating current flows through the said helix 2| the temperature thereof will be raised so high and its resistance thereby so greatly increased that the potential applied to the electrode will 'be greatly reduced and be lowered -below the operatingpotential of the said starting electrode. In addition; the said helix 2| must absorb sufflcient heat radiated from the inner surface of the electrode I8 during the operation of the tube to maintain said helix at such a sufficiently high temperature that its resistance will prevent the application of an operating potential to the tungsten electrode Il. L

By way of example and without limiting myself to this specific embodiment of my invention. I have found that when the helix is constructed in the following manner, satisfactory results are obtained:

' helix is spaced a@ The total length of the iron wire comprising the helix 2| is approximately two-thirds of overall .length of the operating electrode I8 and the said helix comp ises from 3 to 5 turns. The

rt distance from the inner surface of the shl.\ The cross-sectional area of the wire is equal to or less than the crosssectional area of the operating electrode. The overall length of the combined helices I8 and 2| from the base ofthe cup electrode to the free end is approximately two-thirds of the overall length of the operating electrode.

The ends of the tube may be finished off with metallic caps 22, which are secured in any suitable manner, as by cement 23.

Electrical energy is supplied to the tube from `a source of alternating current 2l through a transformer of any type well known to the art,

said transformer being so constructed that when the circuit supplied by it is open a high potentialy will be applied thereto, and when said circuit is closed through a resistance of a certain order of magnitude the potential drops a predetermined value.

My novel electrodes do not necessarily require the companion use of a regulating transformer, although their specific construction may be conditioned thereby.

The operation of the electrodes will now be described with reference to a typical application thereof in va cold fluorescent lighting tube approximately four feet long. It has been found that at room temperatures the striking voltage between iron or ferrous electrodes in such tube is approximately 600 volts and between equally spaced tungsten electrodes about 320 volts. The

operating voltage of the ferrous electrodes is approximately 110 volts, while the operating voltage of tungsten electrodes is approximately 60 volts. Thus if such a tube had only iron electrodes, it would be necessary to initially apply a voltage in the neighborhood of 600 volts to start the tube, and special apparatus and wiring to 'comply with the Fire Underwriters regulations would be required. For example, the fixture employing the fluorescent tube could not be hung from a standard outlet box. However, where my electrode is employed it is only necessary to employ an original starting voltage of -about 320 volts supplied from .the transformer 24. Upon application of this potential, an arc will be struck between the two tungsten electrodes I'I, as illustrated by the electron stream in Fig. 1.

Shortly after this electron stream has been initiated, an electron stream will flow through the ionized gaseous medium between the operating electrodes I6. However, as current flows through the starting electrodes I'I, the temperature of the resistance 2| will be greatly raised. As the resistance of the fluorescent tube decreases upon operatlon,'the potential supplied by the transformer 24 will drop to approximately 110 volts, which suffices to maintain a flow of current between the operating electrodes. However, at such time the ohmage of the resistance 2| has been so greatly increased that less than the operating voltage for tungsten will be impressed upon the tungsten starting electrodes. Current will thus no longer pass between said starting electrodes, and during operation of the tubes the electron stream will be concentrated between the cup-shaped operating electrodes I8, as illustrated in Fig. 2.

Since the tube should be capable of starting.V

in extremely cold weather, for example around .0 F., I contemplate applying a larger starting voltage than 220 volts from the transforme 24, and said transformer may be so constructe as to originally apply 350 volts, which will suillce to strike an arc under such low temperature cononions.

The lowered operating voltage above mentioned in no way affects the starting action of the electrodes or the cutting out of the starting electrodes during operation of the tube,` but .isonly .employed to prevent rapid deterioration of the said operating electrodes.

I have found that where the starting electrode and iron electrode are constructed in accordance with the above description, a lesser power demand is imposed upon the regulating transformers employed with fluorescent electric lighting, and therefore the tendency of the transformer to burn out is substantially eliminated.

It will thus be seen that there is provided a device in which the several objects of this. invention are achieved, and which is well adapted to meet the conditions of practical use.

As various possible embodiments might be made of the above invention, and as various changes might be made in the embodiments abovev set forth, it is to be understood that all of a cross-sectional area no greater thanthe cross-sectional area of said operating electrode shell.

3. `An electric fluorescent lighting device comprising a pellucid envelope, a gaseous ioni'zable medium contained therein, and a, pair of spaced electrodes in said envelope which are electrically unconnected except through said gaseous medium when said device is energized, one of said electrodescomprising a ferrous operating electrode shell, a starting electrode disposed within said operating electrode, and a ferrous resistance disposed within said operating electrode shell and electrically connecting said starting electrode and said operating electrode shell whereby said resistance will initially be heated l by operation of said starting electrode and be matter herein set forth or shown in the accomy.

panying drawing is to be interpreted as illustrative and not in a limiting sense.

Having thus described my invention, I claim as new and desire to secure by Letters Patent:

1. An electric iiuorescent lighting device comprising a pellucidy envelope, a gaseous ionizable medium contained therein, and a .pair of spaced electrodes in said envelope which are electrically unconnected except through said gaseous medium when said device is energized, one of said electrodes comprising a ferrous Joperating electrode shell, a starting electrode and a ferrous resistance disposed Iwithin said operating electrode shell, said resistance electrically connecting said starting electrode and said operating electrode shell whereby said resistance will initially be heated by operation of said starting electrode and be subsequently maintained at a high ternperature by radiation from the inner wills of said `operating electrode shell, the ohmagel of said resistance when so heatedy being sufficiently large to prevent the application of an operating potential to said starting electrode when an opn erating potential is applied to said operating electrode shell.

2. An electric fluorescent lighting device com- .fprising a pellucid envelope,` a gaseous ioizable subsequently maintained at a high temperature by radiation from the inner walls of saidoperating electrode shell, the ohmage of said resistance when so heated being sufficiently large to prevent the application of an operating potential to said starting electrode when an operating potential is applied to said operating electrode shell, said resistance comprising a wire whose llength is approximately two-thirds the overall length of said operating electrode shell.

4. An electric iiuorescent lighting device comprising a pellucid envelope, a gaseous ionizablemedium contained therein, and a pair of spaced electrodes in vsaid envelope which are electrically unconnected except through said gaseous medium when said device is energized, one of said` electrodes comprising a ferrous operating electrode shell, a starting electrode disposed within said operating electrode, and a ferrous resistance disposed within said operating electrdde shell, said resistance electrically connecting said starting electrode and said operating electrode shell whereby said resistance will initially be heated by operation of said starting electrode and be subsequently maintained at a high temperature by radiation from the inner Walls of said operating electrode shell, the ohmageof said resistance when so heated being sufficiently large to prelvent the application of an operating potential to said starting electrode when an operating potential is applied to said operating electrode shell,

. said resistance comprising a wire vof. a crossmedium contained therein, and a pair of spaced electrodes in said envelope which are electrically unconnected except through said gaseous medium when said device is energized, one of said electrodes comprising a ferrous operating electrode shell, a starting electrodel disposed within said operating electrode, and a ferrous resistance disposed within said operating electrode shell, said resistance electrically connecting said starting electrode and said operating electrode shell whereby said resistance will initially be heated by operation of said starting electrode and be subsequently maintained `at a high temperature by radiation from the inner walls of said operating electrode shell, the ohmage of said resistance when' so heated being suiliciently large to prevent the application of an operating potential to said starting electrode when an' operating potential is applied to said operating electrode shell, said ferrous resistance comprising a wire sectional area no greater than the cross-sectional area and whose, length is approximately twothirds the overall length of said operating electrode shell.'

5. vAn electric vfluorescent lighting device comprisingv a pellucid envelope, a gaseous ionizable medium contained therein, and a pair of spaced electrodes in said envelope which are electrically unconnected except ,through said gaseous medium when said device Ais energized, one of said electrodes comprising a ferrous operating electrode shellwa starting electrode comprising a coil of vire'of a material having a relatively low striking voltage, and a coil of ferrous wire disposed within the said ferrous operating electrode shell, said coil electrically connecting saidI starting electrode and said operating electrode shell whereby said coil will initially be heated by operation of said starting electrode and be subsequently maintained at a high temperature by radiation from the inner walls of said operating electrode shell, the 4ohmage of said ferrous coil when so heated being sutiiciently large to prevent the application of an operating poten tial to said starting electrode when the operating potential is applied to said operating elecsubsequently `maintained at,a high temperature by radiation from the inner walls of said operating electrode shell. the ohmage oi' saidlv resistance when so heated being sufiiciently large to prevent the application yof an operating potential to said starting electrode when anoperating potential is applied to said operating electrode marano shell, said pair of spaced electrodes being elecy trically unconnected except through said gaseous medium when said appliance is initiallyenergized.

7. An electric fluorescent lighting appliance comprising a, pellucid envelope, a' gaseous ionizable medium contained therein, and a pair of spaced electrodes in said envelope, each of said large to prevent the application of an operating potential tolsaid starting electrode when an operating potential is applied to said operating electrode shell, said resistance comprising a wire of a cross-sectional area no greater than the cross-sectional area and whbse length is approximatcly two-thirds the overall length of said operating electrode shell, said pair oi! spaced electrodes being electrically unconnected except through said gaseous medium when said applil ance is initially energized.

`9. An electric fluorescent lighting appliance comprising a pellucid envelope, a gaseous ionizable medium contained' therein, and a pair of spaced electrodes in said envelope, each ofsaid electrodes including a ferrous operatlngvelectrode shell, a starting electrode comprising a coil of wire of amaterial having a relatively lovr striking voltage, and a coil of ferrous wire disposed-within the said ferrous operating electrode shell, said coil electrically connecting said starting electrode and said operating electrode shell whereby said coil will initially be heated by operation oi' said starting electrode and be subsequently maintained at a high temperature by radiation from the inner walls of said operating electrode shell, the ohmage of said ferrous coil when so heated being sumciently large to prevent .the application of an operating potential to said starting electrode when the operating potential is applied to said operating electrode shell, the coil comprising said starting electrode being convoluted in a direction opposite to the convolutions of said ferrous coil, said pair as of spaced electrodes being electrically unconperature by radiation from the inner walls oi' said operating electrode shell, the ohrnage of said resistance when so heated being sufficiently large to prevent the application of an operating potential to said starting electrode when an operating potential is applied to said operating electrode shell, said pair of spaced electrodes vbeing electrically unconnected except through shell, said resistance electrically connecting said starting electrode and said operating electrode shell whereby said resistance will initially be heated by operation of said starting electrode and be subsequently maintained at a high tem-4 perature by radiation from the inner walls of said operating electrode shell, the o hmage of said resistance when so heated being sufficiently l nected except through said gaseous medium when said appliance is initially energized.

l0. An electric fluorescent lighting device comprising a pellucid envelope, a gaseous ionizable o medium contained therein, and a pair of spaced electrodes in said envelope which are electrically .unconnected except through said gaseous medium when said device is energized, one of said electrodes -comprising an operating electrode shell of a material having a relatively high striking voltage, a starting electrode of a material having a relatively low striking voltage and a resistance electrically connected in series between said operating and said starting electrodes and disposed within said operating electrode shell so that said resistance will be initially heated by the current flowing therethrough to said starting electrode and will subsequently be maintained at a high temperature by radiation from the inner walls of said shell without passing electric current through said resistance, the ohmage of said resistance when so heated being suiilciently high to vprevent the application of an operating potential to said starting electrode when an operating potential is applied to said operating electrode shell.v

, O'I'IO RICHARD BESSER.

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