US2126787A

US2126787A - Electric lamp

Info

Publication number: US2126787A
Application number: US385707A
Authority: US
Inventors: Bel Clarence J Le
Original assignee: Raytheon Manufacturing Co
Current assignee: Raytheon Co
Priority date: 1929-08-14
Filing date: 1929-08-14
Publication date: 1938-08-16
Anticipated expiration: 1955-08-16

Description

ELECTRIC LAMP Filed Aug. 14, 1929 2 Sheets-Sheet l ilmieva la ial'ence fle/Zal Aug. 16, 1938. c. J. LE BEL ELECTRIC LAMP Filed Aug. 14, 1929 2 Sheets-Sheet 2 Patented Aug. 16, 1938 ELECTRIC LAMP Clarence J. Le Bel, Cambridge, Mass., assigner, by

mesne assignments, to Raytheon Manufacturing Company, Newton, Mass., a corporation of Delaware Application August M, i929, Serial No. 3853i?! 15 Glaims.. (CL 25u-35) REISSUED Netzteil This invention relates to electric lamps and particularly to a lamp which will radiate a substantial portion of its energy in a predetermined portion of the spectrum. The lamp ci this invention is characterized by an extraordinary high instead of neon. In general the gas should have a high ionization potential.

When a lamp with such a mixture of gas is energized so that the sas therein becomes ionized, I have discovered that as much as 65% of the 5 output of energy lying in the ultra violet portion total radiant energy is emitted in the form oi of the spectrum. ultra violet light having a wave length in the A lamp of this character has great utility in case of mercury of about 2537 angstrom units. many elds. Thus for sterilizing and antiseptic By varying the pressure of the mercury within purposes such a lamp is very eilcient. Furthennarrow limits this percentage may be reduced i@ more many chemical reactions, especially obsomewhat as the energy sees into other wave scure organic reactions such as are involved in lengths. Apparently some obscure resonance the tanning of leather, treating of foods and the phenomenon is involved in which rare gas pal'- like, are greatly accelerated by ultra violet light. ticles freely interact with mercury particles to For purposes such as these it has been found that transfer substantially all energy to the latter 15 only a comparatively narrow portion of the specand cause it to emit as described. It is possible trum in the ultra violet region is useful and any that some unstable compound of mercury and of the radiant energy outside of this spectrum is rare gas is formed which emits its characteristic therefore wasted. While devices such as merradiation. The radiation emitted will in general cury arcs in quartz containers are generators of be one of the prominent lines of the substance 20 substantially powerful ultra violet rays, their having the lower ionization potential, in this radiant energy is nevertheless distributed over a. instance mercury. considerable spectrum in this region with a By varying the mercury pressure over the wider resultant loss of eilciency. limits as from 1 to 20 microns, it is possible to An object of this invention is to devise a lamp ionize both the gas and the vapor and change the 25 in which radiant energy in a certain portion of color of the resulting light. In fact it is possible the ultra violet spectrum is generated in a much to go from the pure color of the gas to the pure more ellicient manner than has previously been color of mercury through the combination of the the case. A further object is to devise a lamp two colors by properly adjusting the mercury which will be simple and cheap and will start vapor pressure. Inthis latter case, however, the 30 and operate at reasonably low voltages. lamp does not emit as great a portion of its I have discovered that a metal vapor such as energy in the narrow region of the ultra violet mercury and an inert gas such as argon or neon spectrum 8S iS true When vthe mercury pressure at certain pressures when carrying a discharge, is maintained within smaller limits.

exhibit a remarkable phenomenon. Under oper- Referring t0 the drawings, Figure 1 ShOWS 8. 35 ating conditions the pressure of either one of Preferred embodiment 0f lump 0f Substantially the rare gases may be between 1 and 8 mm. while two thirds full size and a circuit for energizing the pressure of the mercury must be between 1 said lamp. and 8 microns. The pressure of the rare gas is Figures 2 and 3 are mOdCutiOuS not very critical and may be varied over sub- Flgure4 shows an induction lamp drawn to full 40 stantially wide limits. It is, however, necessary Ze. to maintain the mercury pressure within critical Referring to Figure 1, the lamp consists ofa limits. This may be done by either having the container having a substantially uniform cylinnecessary amount of cooling surface in the tube drical p0rt0n l With IOunded Spherical DOIOIIS 2 4; or by artificially cooling the tube so that the deat each end. Most of the light of this lamp is 45 sired pressure is maintained. Apparently it is emitted within the space enclosed by portion I immaterial in what manner the gaseous disof the container. Inorder to effectively transmit charge is effected. Thus the discharge through this ultra violet radiant energy, this 110111011 the gas may beeffected by one or more thermionic may be made 0f quartz 01 a Special glass Which cathodes, one or more cold cathodes in the usual readily transmits such radiations. Portions 2 50 manner or may be eiected by inducing high may be made of ordinary glass if desired in order frequency alternating currents in the gas. to reduce the cost of the lamp. The rounded Sodium or other easily vaporizable metals may portions 2 of the lamp terminate in end portions also be used instead of mercury while a com- 3 having reentrant portions 4 terminating in paratively inert gas like nitrogen may be presses 5. 55

Sealed within these presses are a plurality of wires some of which are both supporting wires and leads while others are merely supporting wires. In order to maintain the assembly, insulating members l having suitably spaced apertures through which the various leads and supporting wires pass, are disposed beyond the press. Supported by insulators 8 and wires 1 are two hollow cathodes.

While any type of cathode may be used, I prefer to use a thermionic cathode in order to reduce the starting and running potential. A hollow cathode ot this type is very efficient and has a long life and is not subject to the destructive bombardment usually present in gas lled tubes. 'I'hese hollow cathodes comprise outer metal members l having a cylindrical shape and end walls 9 with a central aperture therethrough. Within members t are cylindrical members I0 supported by wires II and I2 respectively. Inner members I0 are cylindrical in shape and at their ends carry smaller cylindrical throat members I3 giving access to the inside of members III. Within cylindrical members III are smaller housings M welded or otherwise fastened to the inner surface of members I0. Within these housings are filament heaters Il grounded to the housing and supported by wires I6 and I1. The inner surface of member lo between the throat n and the housing Il is preferably coated with suit- 'able chemicals such as the oxide of alkaline earth metals in order to promote electron emission therefrom. Upon the energization of heaters I6 electron emission takes place from the inside surfaces of members III. During the operation of the tube large quantities of ions are generated in both cathodes and effectively neutralize the electronic space charge. This has a tendency to reduce the cathode drop and greatly increase electron emission therefrom. The lamp is provided with two cathodes, both of which act alternately as anodes when energized by alternating current.

In order to start a lamp of this character, it is necessary to heat either one or both of the cathodes to cause electron emission. Because of the lack of ionization throughout the gas space in the lamp a comparatively high potential in the neighborhood of '100 or 800 volts will be necessary to start a discharge through the tube. As soon as the discharge has started, however, the running potential drops to about volts.

In order to reduce the starting potential and thus eliminate the necessity for complicated apparatus to furnish the high starting potential, I have devised auxiliary ionizing means. These means consist of wires 20 projecting beyond the cathodes and into the space surrounded by portion I of the container. By impressing between 150 and 200 volts across the ionizing wires a sufcient amount of ionization in the gas takes place to enable the tube to have a discharge therethrough.

It is evident that once a discharge has been initiated further discharge between wires 20 is not only unnecessary but may indeed be undesirable. In order to eliminate such a discharge after the tube has been started I preferably have the entire lamp energized by the transformer shown. Due to the reaction of various magnetic fluxes the main discharge through the lamp operates to cut down the ionizing discharge to a negligible value.

Transformer B0 is energized by a primary coil BI supplied by line wires 52 from any suitable source oi' alternating current. Mounted on the same leg of the core of the primary is a secondary l2 which energizes one of the heaters I5 through leads 2| and 2l. Another secondary 53 similar to I2 and mounted on the same leg energizes the other heater Il through leads 4I and 40. Ionizing wires 2l are energized through leads 30 and l0 by a secondary Il on leg ll of the transformer core. Another coil 8B on the same leg 59 as secondary ll is connected by leads B6 and 51 across the two cathodes of the lamp. Coil IIS opposes Il with the result that as soon as the main discharge through the lamp is initiated the current flowing through coil il increases the reluctance of leg M of the transformer core to such an extent as to drive the magnetic flux through the center leg SII and airgap BI. Before the main discharge is initiated through the lamp, the reluetance of leg 50 is so low compared to leg 60 that substantially all the flux goes through the former leg. In this way it is evident that substantial discharge between wires 20 is suppressed upon the lamp coming into normal operation.

The lamp shown in Figure 2 is a modification of Figure 1 in which only one cathode is provided and in which the ionizing wires are broken up into suitable lengths. Portion I of the container of Figure 2 is preferably the same as Figure 1. The end of the lamp containing the cathode is substantially the same as that shown in Figure 1 with the exception that two ionizing wires 10 and 1I are sealed in press 5 to

leads

12 and 13.

If ionizing wires 10 and 1I are too long it has been found that there is a tendency for the discharge to go along these wires, thus reducing the intensity of the gaseous discharge and possibly damaging the ionizing wires. In order to eliminate this I have provided a plurality of distinct ionizing wires connected through resistance to each other to prevent any substantial dis charge between the wires. Ionizing wires 14 and 1l are suitably supported by wires 16 and 11 sealed in the lamp. Additional ionizing wires 1B and 1il are similarly supported by wires 80 and Il. Ionizing wires 1U and 18 are connected through suitable resistances BI and 82 to lead 12.

Ionizing wires 14 and 19 are connected through similar resistances to lead 2I of the cathode. I onizer wire 1I) is connected through a resistance 83 to cathode lead 2|. The values of reslstances 8l, 82 and 83 are preferably so chosen as to prevent any substantial current flowing between the opposing ionizer wires. In this way substantial discharge between them is prevented.

At the other end of the lamp an anode 85 of any suitable material such as carbon or the like is supported by wires sealed in press 5. The lamp is energized by line wires BB and 81 carrying either direct or alternating current. It is evident that if the current is alternating the lamp will rectify while in operation. The anode and cathode are connected to supply wires B6 and B1 through leads B8, resistance B9 and lead 2|. Resistance 88 is of such a value as to keep the current through the lamp at a safe value. In order to energize the heater, lead I6 from the heater is connected through a suitable resistance 9U to line wire 81. Across

lines

86 and 81 is disposed a switch 90 and an inductance 9i. Lead 12 from ionizing wire 1I is connected between the inner point of the inductance 9| and switch 90. As soon as the cathode has been energized, switch 90 is closed but a short time and then suddenly opened. The resulting high voltage surge across 75 amena? inductance 9| is transmitted through lead I2 to ionizing wires 1|, 15 and 18 across the gas space to ionizing wires 10, 14 and 19 through lead 13, resistance 83, cathode lead to inner cathode member i0 then through the heating filament, through lead I6 resistance 90 to the other side of inductance 9|.

The tube of Figure 3 is somewhat similar to Figure 2 in that only one cathode is provided. This may consist of two members |00 of porcelain or the like having a metal shell around them being suitably treated for electron emission. Through these members pass heating laments supported by leads |0|. Leads |02 and cathode lead |03 are sealed in press 5 and act to support the entire cathode. Two ionizing wires |00 and |05 are suitably supported by wires |06 and |01 sealed in tube The connections between the anode and cathode and ionizing wires may be similar to that shown in Figure 2.

In Figure 4 is shown in true form, at substantially full size, an electrodeless induction lamp comprising a tubular portion and bulb ||2. Either or both may be made of material transparent to the ultra violet rays generated. A coil ||3 energized by a suitable source of high frequency such as an oscillator encircles bulb ||3 and energizes the lamp.

After the tubes of Figures 1 to 4 inclusive have thus been constructed they are treated in the customary manner to remove all occluded gases and exhausted to a high vacuum. A small drop of -mercury vapor indicated by M may be introduced within the container. In addition, a quantity of argon or neon may be introduced so that at the operating temperature of the tube, the pressure will preferably be within the limits previously specied. When the tube is first started much of the discharge is carried by the rare gas. The discharge, however, warms the mercury so that its pressure becomes suiiicient for it to partake of the discharge. Within a very short space of time the lamp begins to function as a generator of ultra violet rays.

For example, in a lamp of which the one shown in Figure 1 is drawn to scale and containing neon at about 4 mm. and mercury at about 2 microns, a discharge of two amperes resulted in a very powerful emission of ultra violet in a region of the spectrum below 2900 angstrom units. A major portion of this energy was concentrated in the 2537 line. During the operation of this lamp the current and pressure within the lamp could be adjusted so that practically the greatest portion of the energy was concentrated in the 2537 line.

I claim:

1. .An ultra. violet lamp comprising an envelope, containing mercury vapor at a pressure of between 1 and 8 microns during the normal operation of the lamp, and an inert gas at a pressure of the order of between 1 and 8 mm. and

`means for producing an electrical discharge in said gaseous filling.

2. A gaseous conduction device including a sealed container containing an ionizable atmosphere, electrodes within said container, a plurality of auxiliary electrodes within said container extending into the region between said iirstnamed electrodes, means for initiating a discharge between said auxiliary electrodes for assisting in the starting of the discharge between said first-named electrodes, and means responsive to the current iiowing between said first-named electrodes for suppressing the discharge between said auxiliary electrodes when said current reaches its normal operating value.

3. A gaseous conduction device comprising an elongated tubular container, a thermionic cathode sealed in one end of said container, another electrode adapted to function as an anode sealed at the other end of said container, a gaseous iilling in said container, the pressure of said gas being lower than that at which a discharge will start between said cathode and anode upon the application of the operating voltage across said cathode and anode, a plurality of auxiliary electrodes in said container extending into the region between the cathode and anode, said auxiliary electrodes being spaced apart, the spacing between said auxiliary electrodes being suiliciently small to cause anv ionizing discharge to occur in the gas between said auxiliary electrodes when a voltage of the order of the operating voltage applied to the tube is applied across said auxiliary electrodes, and means for impressing such voltage across said auxiliary electrodes whereby such 4 an ionizing discharge may be produced to cause a main discharge to start between said cathode and anode.

4. A gaseous conduction device comprising an elongated tubular container, two thermionic cathodes sealed in opposite ends of said container, a gaseous lling in said container, the pressure of said gas being lower than that at which a discharge will start between said electrodes upon the application of the operating voltage across said electrodes, a plurality oi auxiliary electrodes in said container extending into the region between the first-mentioned electrodes, the said auxiliary electrodes being spaced apart, the spacing between said auxiliary electrodes being sufliciently small to cause an ionizing discharge to occur in the gas between said auxiliary electrodes when a voltage of the order of the operating voltage applied to the tube is applied across said auxiliary electrodes, and means for impressing such voltage across said auxiliary electrodes whereby such an ionizing discharge may be produced to cause a main' discharge to start between-said first-mentioned electrodes.

5. A gaseous conduction device comprising an Velongated tubular container, a thermionic cathode sealed in one end of said container, another electrode adapted to function as an anode sealed at the other end of said container, a gaseous filling in said container, the pressure of said gas being lower than that at which a discharge will start between said cathode and anode upon the application of the operating voltage across said cathode and anode, and a plurality of pairs of auxiliary electrodes, spaced apart within said tubular container, said discharge path passing between each of said pairs 4of auxiliary electrodes, one electrode of each of said pairs being connected to one electrode of each of the other of said pairs through a resistance, the other electrode of each of said pairs being connected to the other electrode of each of said pairs through a resistance, the spacing between the electrodes of each of said pairs of auxiliary electrodes being sufficiently small to cause an ionizing discharge to occur in the gas between said auxiliary electrodes when a voltage of the order of the operating voltage applied to the tube is applied across said auxiliary electrodes.

6. An electric discharge lamp device comprising a container, a gaseous atmosphere therein comprising mercury vapor and a rare gas, and means for producing a gaseous electric discharge in said atmosphere, the pressure of the mercury vapor being between one and eight microns and the pressure of the rare gas being between one and eight millimeters during the operation of the device.

7. The method ot operating a gaseousconduction lamp comprising a container with a gaseous filling of mercury vapor, and an inert gas having a pressure of the order of between one and eight millimeters, and means for producing a gaseous electric discharge therein which consists in en ergizing said lamp and operating the same while maintaining the vapor pressure of said mercury vapor between one and eight microns.

8. The method of operating a gaseous conduction lamp comprising a container, a gaseous illi- `ing in said container, said gaseous iilling comprising mercury vapor and an inert gas, and means for producing an electrical discharge through said gaseous filling which consists in varying the pressure oi! the mercury vapor between one and -twenty microns, whereby the color emitted by said lamp is varied, the pressure of said inert gas being greater than the pressure o! the mercury v VEDO?.

9. A gaseous conduction device including a sealed container containing an ionizable atmosphere, electrodes within said container, a plurality of auxiliary electrodes within said container ex'- tending into the region between said first-named electrodes, means for initiating a discharge between said auxiliary electrodes for assisting in the starting of the discharge between said ilrst named electrodes, said means comprising a trans- Y former having a primary winding and a secondary winding connected to said auxiliary electrodes, and an additional coil on said transformer energized in response to the current flowing between said first-named electrodes, said additional coil opposing said secondary coil, whereby the voltage generated in said secondary coil is reduced to a negligible value when the discharge starts between said ilrst-named electrodes.

10. A gaseous conduction device comprising an elongated tubular container, a thermionic cathode sealed in one end of said container, another electrode adapted to function as an anode sealed at the other end of said container, a gaseous illling in said container, the pressure of said gas being lower than that at which a discharge will start between said cathode and anode upon the application oi' the operating voltage across said cathode and anode, a plurality of auxiliary electrodes in said container extending into the region between the cathode and anode, the spacing between said auxiliary electrodes being suiiiciently small to cause an ionizing discharge to occur in. the gas between said auxiliary electrodes whenV a voltage oi' the order of the operating voltage applied to the tube is applied across said auxiliary electrodes, whereby an ionizing discharge may be produced to cause a. main discharge to start between said cathode and anode, a circuit for irnpressing a starting voltage to the auxiliary electrodes. and another circuit for impressing an operating voltage between the main electrodes, said two circuits being electrically insulated from each other.

11. An electrical discharge lamp comprising a container, a gaseous atmosphere therein, and means i'or producing an electrical discharge through said gaseous atmosphere, said gaseous atmosphere comprising mercury and an inert gas. the pressure of the mercury vapor during operation being below eight microns but sutnclently high to become ionized during operation and to emit radiations therefrom, the pressure o! the inert gas being at a substantially higher order of magnitude sufilcient to permit an ionizing discharge to be initiated therein.

l2. An electrical discharge lamp comprising a container, a gaseous atmosphere therein, and means for producing an electrical discharge through said gaseous atmosphere, said gaseous atmosphere comprising mercury and an inert gas, the pressure of the mercury vapor during operation being below eight microns butsuiliciently high to produce substantially a maximum oi radiation eillciency, the pressure oi the inert -gas being at container, a gaseous atmosphere therein, and

means for producing anA electrical discharge throughsaid gaseous atmosphere, said gaseous atmosphere comprising a metallic vapor and an inert gas, the pressure of the metallic vapor during operation being below eight microns in the path of the discharge but sufficiently high in the path of the discharge to become ionized during operation and to emit radiations therefrom, the pressure of the inert gas being at a substantially higher order oi.' magnitude sufiicient to permit an ionizing discharge to be initiated therein.

14. An electrical discharge lamp comprising a container, a gaseous atmosphere therein, and means for producing an electrical discharge through said gaseous atmosphere, said gaseous atmosphere comprising sodium vapor and an inert gas, the pressure oi' the sodium vapor during operation being below eight microns in the path of the discharge but suiiiciently high in the path of the discharge to become ionized during operation and to emit radiations therefrom, the pressure o! the inert gas being at a substantially higher order oi magnitude sui'iicient to permit an ionizing discharge to be initiated therein.

l5. An electrical discharge lamp comprising a container, a gaseous atmosphere therein, and means i'or producing an electrical discharge through said gaseous atmosphere, said gaseous atmosphere comprising sodium vapor and an inert gas, the pressure of the sodium vapor during operation being below eight microns in the path of the discharge but sumciently high to produce substantially a maximum oi radiation eiilclency, the pressure of the inert gas being at a substantially higher order of magnitude sufficient to permit an ionizing discharge to be initiated therein.

CLARENCE J. LE BEL.