US1658568A

US1658568A - Method and apparatus for maintaining gaseous conduction discharges

Info

Publication number: US1658568A
Application number: US576768A
Authority: US
Inventors: Moore Daniel Mcfarlan
Original assignee: General Electric Co
Current assignee: General Electric Co
Priority date: 1922-07-22
Filing date: 1922-07-22
Publication date: 1928-02-07
Anticipated expiration: 1945-02-07
Also published as: FR568752A; NL14865C; GB221547A

Description

Feb. 7, 1928. 1,658,568

D. M F. MOORE METHOD AND APPARATUS FOR MAINTAINING GASEOUS CONDUCTION DISCHARGES Filed Ju1y22, 1922 Inventor: Daniel TTlc Farlan moore,

His Attorney.

Patented Feb; 7, 1928.

UNITED STATES arENT or FICE.

DANIEL MQFARLAN MOORE, OF EAST ORANGE, JERSEY, ASSIGNOR TO GENERAL ELECTRIC COMPANY, A CORPORATION OF NEW YORK.

METHOD AND APPARATUS FOR MAINTAINING GASEO 'US OONDUGTION DISCHARGES.

Application filed July 22, 1922. Serial No. 576,768.

My invention .relates to gaseous conduction devices in which an electric discharge occurs in the space between electrodes mounted in a closed vessel which contains a more or less rarefied vapors or gases and more particularly to devices of this character intended to be used as a source of light and so constructed that the vapors or gases are rendered luminous by the electric disiu charge.

In a typical vacuum tube or gaseous conduction device of the character to which my invention relates the discharge produced by the passage of an electric current thru a l tube provided with similar electrodes at each end does not extend uniformly throughout the space between the electrodes. At each alternation of the impressed voltages, there is adjoining the cathode a non-luminous region known as the Crookes dark space. Beyond this is a luminous region known as the negative glow followed by the second or Faraday dark space and beyond this and extending to the anode is a luminous region known as the positive column. In order to obtain a practical intensity of light at good etliciency from an electric discharge in a device of this character the pressure of the gas and the spacing of the electrodes should be so chosen that most of the luminosity is produced by the positive column. Heretofore, in order to obtain such a discharge it has been customary to impress upon the electrodes of such a tube a high potential ob tained from the ordinary low potential distribution circuits by means of a transformer,

which increases the cost and greatly complicates the lamps.

@ne object of my inventionis to provide at and operate when connected directly to a lighting circuit of low operating potential, such as 220 volts or even 110 volts, without the use of any auxiliary or external means for raising above the normal operating potential of the line the potential impressed a gaseous conduct-ion lamp which will start.

upon the electrodes and which utilizes the efiticient positive glow or discharge as the source of light. Another objectis to provide a gaseous conduction lamp resembling the incandescent lamp now in common use and provided with a positive column dis charge-which is in efi'ect a gaseous filament, yet so constructed that the lamp will operfor supplying incandescent electric lamps. A further ob ect is to provide a simple and rugged form of gaseous conduction lamp,

closed vessel containing a gas of high conductivity as for example some of the rare gases such as neon or neon mixed with some helium, the pressure of the gas and the spacing of the electrodes being so chosen that the discharge between the main electrodes will consist almost entirely of the positive column. The starting and maintaining of the postive column discharge is so facilitated by my invention that ordinary low voltages, such as used forcommercial light ing by incandescent lamps, are sufficient to start and maintain a positive column discharge between the main electrodes. I at tain this result by so constructing-the device that normal operating potential such as 220 volts or 110 volts when applied to the device will afi'ect the gas adjacent the main electrode in such a manner as to cause the positive column discharge to appear at that potential. [to produce the desired efi'ect on the gas I use some means which in response to the normal operating potential of the device will ionize the gas or produce the effect of ionization, whereupon normal potential will maintain the positive column discharge between the main electrodes. preferably produced by some auxiliary means such as a third electrode mounted adjacent one of the two main electrodes to form one electrode of an auxiliary gap connected in parallel with main electrodes and so constructed that the normal potential of the circuit will cause the desired effect upon the gas in the immediate vicinity of the third electrode and thereby upon the gas between the main electrodes also, whereby a positive column discharge is caused to occur and be maintained at the normal potential of the circuit.

In accordance with my invention theelec- The effect is ing gap that very little or no visible discharge occurs in thatgap, while a brilliant positive column discharge occurs and persists between the main electrodes. Apparently this resistance at the electrodes of the auxiliary gap is caused by the Crookes dark space from each electrode extending practically to the other electrode at the potential of the supply circuit. I prefer'to confine the discharge from the third electrode to the end of that electrode and one convenient way to do this is to use cylindrical ionizing electrodes and place theminaglass tube having a bore only slightly larger than the ionizing electrodes. Where it is desired that the lamp shall start and operate on a very low potential such as 110 volts, I prefer that one or both of the electrodes of the auxiliary gap be made of or coated or treated with amaterial having a high electron emissivity, as for example, magnesium, caesium, or some equivalent metal.

This and other aspects of my invention will be more fully explained in the specification following and the novel features of my invention are pointed out with greater particularity in the appended claims, but the invention itself may best be understood in con nection with the acompanying drawing in which merely for purposes of illustration I have shown some of the various forms in which my invention maybe embodied and in which Figure 1 is a view of one form of lamp embodying my invention; Figure 2 is an other form; and Figure 3 is still another form in which the light giving column is curved.

I have shown-my invention embodied in lamps which are substantially the size and shape of the incandescent lamps in general use, as this form of embodiment of my invention is very convenient. My invention is not restricted to such lamps, but is equally valuable in any-form of gaseous conduction lamp utilizing the positive column as a source of light.

7 In Figure 1, I have illustrated a form of lamp comprising a bulb 1 quite similar in SIZE and shape to an lncandescent lamp and provided with a screw base 2 such as commonly used on incandescent lamps. Leading inwires 3 for supplying current to the lamp are connected at their outer ends to the contacts of the base as is customary in incandescent lamps, and at their lower ends to main electrodes between which occurs the positive column discharge from which the light is obtained. The lead wires 3 are preferably though not necessarily coated with positive column discharge to a definite channel, as for example by a glass or quartz tube 6 open at one or both ends, in which the electrodes 5 are placed so that the discharge is confined to the tube. The length of this :tube should be greater than its diameter, and

it should be as long as possible to'obtain the best efficiency.

I prefer to use in the bulb 1 a rare gas or vapor of good conductivitysuch as neon. or neon having mixed with it some other rare gas, such as helium. The gas in the bulb is at such a pressure that any discharge initiated and maintained between the main electrodes 5 at the voltages commonly used for operating incandescent electric lamps will consist almost entirely of the positive glow or column. This pressure may range from 5 mm. to 50 mm. of mercury depending upon the character of the electrodes, their spacing, the composition of the gas, and other factors. If the pressure is too low there is merely a faint glow around the electrodes; if the pressure is too high the discharge contracts into a thin threadlike column; but if the pressure is right the positive column discharge fills the tube 6.

In accordance with my invention the gas between the main electrodes is affected or ionized by some means responsive to the low potential commonly used on supply circuits for incandescent lamps so that the discharge between the main electrodes 5 can be started and maintained at that low potential. I prefer to use some means responsive to this low normal potential which will keep the gas between the electrodes ionized at the low potential of the supply circuit. One suitable means responsive to the normal potential of the circuit for supplying incandescent electric lamps is an ionizing gap so proportioned that at normal potential it permits sufficient current to flow to produce a scarce- 1y noticeable discharge, but offers such resistance that at the same potential a large current flows between the main electrodes as a bright positive column discharge in parallel with the discharge in the auxiliary gap. A suitable ionizing gap may be made between one of the two main electrodes and a third or auxiliary electrode 7 or preferably by using two such auxiliary electrodes spaced apart a distance such that an ionizing discharge will occur between them but very little current will flow. hen such a gap is connected in parallel with the main electrodes, 5, as shown in Figure 1, and the normal potential of the circuit is impressed upon bothpairs of electrodes, a barely VISI- hle discharge will occur between the auxiliary electrodes 7 which apparently ionizesmain electrodes. I prefer to confine thepositive column discharge between the electrodes 7 to their adjacent'ends as much as.

possible as, for example, by enclosing the cylindrical electrodes 7 in a glass tube 8 having BflJOl'G only slightly larger than the electrodes. The auxiliary electrodes may be connected in-parallel with the main electrodes in any convenient way for example, by making them an extension of the main electrodes which are preferably made of magnesium wire wound into a spiral as indicated in Figure 1. I I I I have obtained good results with either alternating or direct potential of about 220 volts with a lamp constructed as shown in Figurel with the bulb 1 about three inches in diameter and main electrodes 5 made of seven turns of magnesium wire 38 thousandths of an inch in diametenwound to form a sort of cup having a bore aboutone quarter of an inch. These main electrodes have a gap about three quarters of an inch inlength between them and the open ended glass tube 6 is about one and a half inches long with a bore about five sixteenths of an inch. 'The electrodes of the ionizing gap may toadvantage consist, of the ends of the magnesium wire composing the main electrodes, these ends being spaced one-thirtysecond of an inch apart in a glass tube 8 about five-eighths of an inch long and having a bore such that it fits the electrodes 7 just loosely enough to be moved along them easily. I have found that if the tube 8 fits the electrodes too tightly the auxiliary gap does not function properly. If the tube 8 fits loosely but the length of the gap between the electrodes 7 is too great, a luminous discharge like that in a Geissler tube appears inthe gap at a normal potential of 220 volts and the electrodes should be moved'towards each other until this luminous discharge just disappears, whereupon the length of the gap will be correct. I

The bulb 1 was first well exhausted and then filledto a pressure of about 20 mm. of mercury with a mixture of neon and helium containing about 20% helium. Such a lamp when connected to a 220volt alterrating current circuit lighted up immediately with a brightcolumn of light between the electrodes 5 and consumed about 4.5 watts when a limitingresistance 9 of 5000 ohms was used.

In Figure 2 I have shown a form of lamp which, in general, is constructed much like Figure 1, but in which the main electrodes 5 are so mounted that thedischarge between ure 1.

within wide limits, but if toolarge it prethem is confined to a tube 10 sealed at both ends and communicating with the interior of the' bulb 1 through a" vent 11 which equalizes the pressure and enables the bulb to act as a sort of reservoir of gas and to prevent m wide fluctuations of pressure of the gas through which the discharge is passing. In this particular form of lamp the lonizing gap, mounted outside of the posltive column discharge between the main'electrodes, and 75 as shown in Figure 2 at a considerable distance from the main electrodes, is construct ed substantially like'the ionizing gap of the lamp shown in Figure 1 and may be connected to the leads at any place which is'con- S0 venient. This lamp is constructed with sub-' stantially the same pressure and electrode size and spacing as that shown in F ig- The size of the vent ll may vary vents the discharge between the main electrodes 5 being confined to form a column of the most advantageous cross section.

In Figure 3 I have illustrated another form of lamp in which the ionizing elec- 0 trodes 7 are mounted adjacent to or immediately behind the main electrodes 5. In this a particular form of lamp the discharge between the main electrodes is restricted or confined to" a bent tube 12 provided with a vent 13 to the interior of the bulb 1. The

tube 12 should have an interiordiameter which "will restrictthe discharge to the cross section at whichit has the greatest elficiency.

If the tube is made to small the discharge will not pass, while if thetube is made too large the discharge becomes rather diffuse and decreases in intrinsic brilliancy. In all cases it is advantageous to have the envelope around the main electrodes 5 oflgreater di- 5.

ameter than the bore ofthe tubewhich confines the light giving positive column, whether the main electrodes'be smallor large. a

the 'form of lamp such as shown'in uo Fi ure 3 the auxiliary gaps'may be placed adjacent to the main electrodes 5 and in the same chamber with them.- In Figure 3 I have shown two ionizing gaps one'for each I main elect-rode but the lamp will function well when only oneof the ionizing gaps is used. The electrodes 7 of each gap 'are connected to opposite sides of the circuit through wires 14.- and .15 in the base of the lamp. If the tube8 of each auxiliary gap is left open at the ends it should be of such 7 a length that a discharge around the outside of the tube encounters greater resistance than a discharge between the main electrodes 5 .of the lamp, but I prefer to seal the remote end of each tube enclosing an electrode 7 so as to 'enclose'the ionizing gap in a kind of, cup with its open end adjacent to the main electrodes.

In many cases I find it desirable to limit bright the amount of energy expended in the ionizin gap to some nominal amount, such as one haIf watt, by inserting a controlling resistance 16. When such a resistance is used the length of the ionizing gap for 220 volts may be as much as one sixteenth of an inch, although I prefer one thirty-second of an inch and the glass tube 8 can then be made of larger diameter or eliminated.

A lamp may be constructed as shown in Figure 3 suitablefor useon a 220 volt circuit with either alternating or direct current with bulb 1, main electrodes 5, ionizing gaps with electrodes 7 and tubes 8, and with the gas in the bulb 1 of the same composition and pressure as above described in connection with the lamp shown in Figure 1. It is immaterial whether the ends ofthe bent tube 12 are practically side by side so. as to make the tube U shaped or whether they are further apart, so long as the main gap in which the positive column discharge occurs between the main electrodes 5 is about one inch long measured along the axis of the bent tube 12.v I have found that such a lamp when connected directly to a 220 volt alternating current circuit will light up immediately and operate continuously with a positive column discharge in the tube 12. p

Various means other than the ionizing gap disclosed may in; accordance withmy invention be used to ionize the gas in the gap between the main electrodes and to keep it ionized so thata positive column'discharge will start and persist at low potentials. for example, use radio active materials, but I prefer to use some means responsive to the normal potential of the supply circuit com-v monly used for incandescent lamps such as the auxiliary gap with magnesium or equivalent electrodes spaced the proper distance apart to respond to the normal potential. applied to the lamp. r i

My invention may be embodied in other forms not shown or described and I do not wish to be restricted to theparticular forms shown.

IVhat I claim as new and desire to secure by Letters Patent of the United States, is 1. A gaseous conduction device com ris ing a closed vessel containing a rarefie gas of good conductivity, a tube mounted in said.

vessel and having enlarged sealed chambers at its ends and a vent intermediate its ends and an electrode having a cross-section greater than the bore of said tube in each of said chambers, the length of said tube and the pressure of the gas in said vessel being such that the discharge between said electrodes consists principally of-the positive column. Y

2. A gaseous conduction device comprising'a sealed vessel containing rarefied gas of good conductivity, a U shaped transpar-- I may of the positive column.

ent tube in said vessel having a vent at the bend and at its ends sealed chambers larger than its bore, and electrodes in said sealed chambers of a cross-section greater than the bore of. said tube, the pressure of said gas in said vessel being such that the discharge through said tube between said electrodes consists principally of the positive column.

3. A low potential gaseous conduction lamp comprising a sealed glass bulb containing a conductive gas and having a base and re-entrant tubular stein, a transparent bent tube mounted on said stem and having enlarged scaled chambers at its ends and a vent to the interior of said vessel, and electrodes having a cross-section greater than the bore of said tube mounted in said enlarged chambers, the pressure of the gas in said bulb being such that the discharge between said electrodes consists principally of the positive column.

4. A low potential gaseous conduction device comprising a scaled bulb containing a rarefied gas of good conductivity, a tube in said bulb having sealed enlarged chambers at its ends, electrodes mounted in said sealed chambers of a cross-section such that the discharge between them is constricted by said tube, an auxiliary electrode mounted in one of said enlargements to form an electrode of a short'gap proportioned to permit a non-luminous discharge at the normal potential of the circuit and thereby cause at that potential a-discharge between the main electrodes and a current controlling resistance in series with said auxiliary electrode, the pressure of said gas in said bulb being such as to cause the discharge between said electrodes in said tube to consist principally 5. A gaseous conduction lamp comprising a sealed bulb having a base secured to one end thereof and containing a rarefied gas, a U shaped transparent tube mounted in said bulb and having enlarged sealed chambers at its ends, the bent portion of said tube between said enlargements having a length several times the bore of the tube and a vent to the interior of said bulb, a main electrode in each of said enlargements having a cross-section greater than the bore of said tube, an auxiliary electrode in each of said enlargements spaced from the main electrode in said enlargement to form a discharge gap of such a length as to permit a non-luminous discharge at the operating po tential of the lamp, and current controlling resistance in series with said auxiliary elecof main electrodes spaced apart about threefourths of an inch in said vessel to cause the discharge between them to consist principally of the positive column, a tube having a diameter less than its length for confin- 7 ing the discharge between said electrodes,

and auxiliary electrodes spaced apart about one thirty-second of an-inch-and connected in parallel with the main electrodes, and an open ended glass tube fitting loosely over said electrodes and of a size to permit a nonluminous discharge to occur between said electrodes and start a positive column discharge between the main electrodes 7 The. method of maintaining a positive column gaseous conduction discharge at low potential in a rarefied gas between electrodes separated a distance greater than the striking distance of said potential, which consists of ionizing the gas in the vicinity char e in said gas at said low potential in para l el to said positive discharge and thru the Crookes dark space only.

8. The method of maintaining a positive colu'mngaseous conduction discharge at low potential in a rarefied gas between electrodes separated a distance greater than the striking distance of said potential, which consists in ionizing the gasin the vicinity of one of said electrodes by an auxiliary discharge in said gas at said low potential in parallel to said positive column discharge and limiting said auxiliary discharge to restrict it to substantially the Crookes dark space.

In witness whereof I have hereunto set my hand this 18th day of J uly 1922.

DANIEL MoFARLAN MOORE.