US2135284A - Cathodic lamp - Google Patents

Cathodic lamp Download PDF

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Publication number
US2135284A
US2135284A US192808A US19280838A US2135284A US 2135284 A US2135284 A US 2135284A US 192808 A US192808 A US 192808A US 19280838 A US19280838 A US 19280838A US 2135284 A US2135284 A US 2135284A
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US
United States
Prior art keywords
lamp
sodium
cathodic
light
envelope
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Expired - Lifetime
Application number
US192808A
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English (en)
Inventor
Clifton G Found
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
General Electric Co
Original Assignee
General Electric Co
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US192808A priority Critical patent/US2135284A/en
Application granted granted Critical
Publication of US2135284A publication Critical patent/US2135284A/en
Priority to FR850738D priority patent/FR850738A/fr
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/64—Cathode glow lamps

Definitions

  • My invention relates to a gas-filled or discharge 5 lamp of the so-called cathodic type in which light generation is largely Aconned to a region closely adjacent the cathode.
  • Fig. 1 is a perspective view of a cathodic lamp embodying my invention
  • Figs. 2 and 3 are graphical representations illustrating the improved characteristics which are realized by the use of the invention.
  • the lamps with which my invention deals are of the thermionic discharge type employing an incandescible cathode and are conventionally constructed so that the distance between the cathode and the anode is comparable to the least dimension of the envelope.
  • substantially all of the utilizable light energy is generated within a restricted radial distance of the cathode. It is, therefore, convenient to refer to such a light source as aV "cathodic lamp.
  • Cathodic lamps of the type with which my invention is particularly concerned comprise a sealed envelope defining a discharge space which contains suitable electrode structure, a vaporizable substance such as sodium and an inert or noncondensable gas such as neon.
  • a vaporizable substance such as sodium
  • an inert or noncondensable gas such as neon.
  • the sodium or-equivalent vaporizable material It is a function of the sodium or-equivalent vaporizable material to provide a source of substantial numbers of atoms which may be brought to a state of light radiation by impact with electrons of low energy content as is more fully explained in the following.
  • the neon or other inert gas has been found to serve a multiplicity of functions which add both to the convenience of operation and the efficiency 5 of the lamp.
  • the neon provides atoms which serve as a deflecting means to lengthen the total path of the mov- 10 ing electrons, which would otherwise proceed almost directly through the eldof sparse sodium atoms to the anode. 'Ihis increase in the average path of travel of an individual electron greatly enhances the probability of vits encountering a l5 sodium atom in a light-emitting impact.
  • neon is capable of a further service which makes it particularly useful in the cathodic type of lamp. It has been observed that the voltage drop in an 20 electron discharge tube having closely spaced electrodes is largely concentrated in a narrow sheath around the cathode which sheath may be less than 116 of a Acentimeter in thickness. It is within this sheath that emittedelectrons receive 25y v substantially all their energy, such energy being conveniently expressedl by giving the number of volts against which an electron of the given energy content is capable of moving.
  • lt may either ionize the same or excite it to luminosity, depending upon the exact energy values involved.
  • the impinglng electron will not, of 35' course, be destroyed, but will continue its journey with its energy reduced by an amount which represents the ionization or excitation voltage of the neon.
  • An excited sodium atom is, generally speaking, capable of two further' 50 changes in condition; it may, if undisturbed for a brief period, return to its natural state, such return being accompanied with the production of light, or it may be converted into a sodium ion by a further impact with an electron having energy 56 micron.
  • I have illustrated an elongated sealed envelope I terminating at its base in a reentrant stem 2 provided with a press 3.
  • a filling of a xed gas such as neon is provided in the envelope I and a quantity of sodium, or other vaporizable material, is deposited on the wall of the tube as shown at 4.
  • the entire tube may appear to be filled with a diffused sodium glow. This is because sodium resonance radiation, actually generated within the restricted region only, is continually absorbed and reemitted by. sodium atoms in the outlying space. Luminous emission from the tube is thus viewed externally as though it were taking place from the outer portion of 'the lamp.
  • the dimensions of the region of light generation are determined in part by the concentration of excitable atoms which in turn depends on the ratio of neon pressure to sodium pressure.
  • the optimum condition which can be obtained is that at which the light generating region is coextensive with the volume of the bulb. It is not practical to assign an exact value for the best neon pressure to be employed, but this factor may be determined experimentally for any given tube construction. I have obtained most satisfactory resultsvwith a pressure of neon in the neighborhood of 400 microns of ⁇ mercury and a pressure of sodium of the order oi magnitude of one
  • a mica disk 6 is provided which effectively divides the base froml the main body of the envelope.
  • Concentrically arranged within the anode I provide a thermionic or incandescible cathode II comprising an elongated metal lament, either The anode 5 is shown as coiled or straight, coated with an electron emissive substance such as an alkaline earth metal oxide and supplied with heating current through,
  • electrodes should extend lengthwise of the envelope for a distance substantially greater than the tube diameter and preferably commensurate with its length.
  • I have indicated an elementary circuit comprising a main transformer 22, a filament transformer 23 and a current. limiting resistor 24.
  • curve A comprises the output characteristic of a cathodic lamp of known type in which the cathodev comprises a relatively concentrated coil. It will be seen that While the luminous output increases linearly with cu'rrent up to a value of about 11/2 amperes, above that value -the curve iiattens out to such an extent that little or no gain is realized by increasing the current input.
  • curve B shows the improvement obtained' in the operation of a cathodic lamp of identical construction with that of curve A by carefully selecting an optimum ratio of neon to sodium pressure which in the instance chosen operated at such temperature that the sodium;- vapor pressure was approximately one micron.
  • a considerable in- ⁇ crease in luminous output is .realized by the change indicated a definite saturation eiect occurs at currents materially in excess of 5 amperes.
  • the curve C represents the results obtained by using( an electrode arrangement such as is shown in Fig. 1 in connection with an optimal neon pressure of about 400 microns.
  • an electrode arrangement such as is shown in Fig. 1 in connection with an optimal neon pressure of about 400 microns.
  • the envelope and other structural parts were of precisely the same dimensions as were employed in connection with curves A and B.
  • a current intensity corresponding to'an ar'c current of 10 amperes was employed without producing any manifestation of saturation due to cumulative ionization.
  • a luminous output Iof approximately 10,000 lumens was obtained in a lamp having a volumetric content of approximately 450 cubic centimeters and using a power input of. approximately.- 200 watts. To the best of my knowledge this is the first time that an output of this magnitude has been attained in a cathodic, lamp irrespective of the input employed.
  • a further advantage attendant upon the use of an extended rather than a concentrated cathode consists in the possibility of making a cathodio lamp which is substantially insensitive to variations in ambient temperature.
  • the point y indicates the temperature re quired to vaporize the least amount of sodium sufficient to produce maximum,A light excitation, i. e., 'to permit full utilization of available electron energy.
  • 'I'he point z on theother'hand, represents the temperature vat which excessive cumulative ionization begins to occur.
  • the light output of the lamp may be substantially insensitive lto variations in ambient temperature (at least as long as such variations do not carry the operating temperature of the lamp above z or below il).
  • this result can be obtained by selectingthe proportions and heat insulation of the lamp such that at the preferred operating currents, i. e. for discharge currents corresponding to the range of emcient operation .f may, for example, take the form of a transparent vacuum jacket such as is indicated at 25 in Fig. 1.
  • the form of lamp which I have described is exemplary only and it will be understood that various modications o f 'structure may be used.
  • the anode may be constituted of'a screen-like mesh rather than a spiral ribbon as illustrated and the cathode may lcomprise an velongated helical structure rather than a straight lament such as that shown in Fig, 1.
  • a cathodic lamp comprising an envelope which encloses a discharge-Supporting gas.
  • a cathodic lamp including an elongated tubular envelope which encloses a discharge-supporting gas, a vaporizable light-producing substance, and a vpair of cooperating electrodes hav ⁇ ing mutually facing discharge-receiving surfaces place, whereby the luminous output of said lamp is substantially insensitive to variations in ambient temperature.
  • a cathodic lamp comprising an elongated tubular envelope enclosing an inert gas, a quantity of sodium and concentrically arranged discharge electrodes having opposed discharge-receiving surfaces which extend longitudinally of the envelope a distance substantially greater than the diameter thereof, the proportions and heat insulation of the envelope being such as to main-v tain in the vapor phase during operation of the lamp a quantity of sodium intermediate between the least amount suflicient for maximum light excitation at the operating current of the lamp and.
  • the amount at which cumulative ionization becomes excessive whereby the luminous output of the lamp is substantiallyv independent of variations in ambient temperature.

Landscapes

  • Discharge Lamp (AREA)
  • Discharge Lamps And Accessories Thereof (AREA)
US192808A 1938-02-26 1938-02-26 Cathodic lamp Expired - Lifetime US2135284A (en)

Priority Applications (2)

Application Number Priority Date Filing Date Title
US192808A US2135284A (en) 1938-02-26 1938-02-26 Cathodic lamp
FR850738D FR850738A (fr) 1938-02-26 1939-02-23 Perfectionnements aux lampes à décharge

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US192808A US2135284A (en) 1938-02-26 1938-02-26 Cathodic lamp

Publications (1)

Publication Number Publication Date
US2135284A true US2135284A (en) 1938-11-01

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Family Applications (1)

Application Number Title Priority Date Filing Date
US192808A Expired - Lifetime US2135284A (en) 1938-02-26 1938-02-26 Cathodic lamp

Country Status (2)

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US (1) US2135284A (fr)
FR (1) FR850738A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2899584A (en) * 1955-01-24 1959-08-11 Verwey

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2899584A (en) * 1955-01-24 1959-08-11 Verwey

Also Published As

Publication number Publication date
FR850738A (fr) 1939-12-23

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