US2135283A - Method of producing polychromatic light - Google Patents

Method of producing polychromatic light Download PDF

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Publication number
US2135283A
US2135283A US103567A US10356736A US2135283A US 2135283 A US2135283 A US 2135283A US 103567 A US103567 A US 103567A US 10356736 A US10356736 A US 10356736A US 2135283 A US2135283 A US 2135283A
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US
United States
Prior art keywords
cathode
discharge
current
electron
light
Prior art date
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Expired - Lifetime
Application number
US103567A
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English (en)
Inventor
Clifton G Found
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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 US103567A priority Critical patent/US2135283A/en
Priority to FR827367D priority patent/FR827367A/fr
Priority to GB26526/37A priority patent/GB503024A/en
Priority to FR827395D priority patent/FR827395A/fr
Application granted granted Critical
Publication of US2135283A publication Critical patent/US2135283A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/70—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr
    • H01J61/72—Lamps with low-pressure unconstricted discharge having a cold pressure < 400 Torr having a main light-emitting filling of easily vaporisable metal vapour, e.g. mercury
    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J61/00—Gas-discharge or vapour-discharge lamps
    • H01J61/02—Details
    • H01J61/12—Selection of substances for gas fillings; Specified operating pressure or temperature
    • H—ELECTRICITY
    • H05—ELECTRIC TECHNIQUES NOT OTHERWISE PROVIDED FOR
    • H05B—ELECTRIC HEATING; ELECTRIC LIGHT SOURCES NOT OTHERWISE PROVIDED FOR; CIRCUIT ARRANGEMENTS FOR ELECTRIC LIGHT SOURCES, IN GENERAL
    • H05B41/00—Circuit arrangements or apparatus for igniting or operating discharge lamps
    • H05B41/14—Circuit arrangements
    • H05B41/36—Controlling
    • H05B41/38—Controlling the intensity of light
    • H05B41/39—Controlling the intensity of light continuously

Definitions

  • the present invention relates to a novel method of operating luminous discharge devices of the type known as cathodic lamps.
  • this object is attained by so regulating the cathode temperature at a given discharge current, or by so regulating the discharge current at a given cathode temperature, that at least during certain portions of the operating cycle of the lamp different components of the gaseous mixture in the lamp are caused to be preferentially excited to give light, thus varyin the character of the instantaneous light output 0 of the lamp. Since different gases emit different colored radiations when excited, the effect of these variations will be to produce the appear- .ance either of blended polychromatic light or of a light of constantly varying shade, depending 5 on the rapidity with which the variations are caused to occur.
  • the luminescence produced by a gaseous discharge between relatively spaced electrodes is comprised of a plu- L0 rality of zones having somewhat different characteristics.
  • the principal sources of light comprise the positive column which forms in the intermediate space between the electrodes and the cathodic glow which L5 occurs in a region very close to the cathode.
  • conditions of operation may be chosen such that essentially no positive column is present while the cathodic glow is raised to a maximum.
  • the spacing between 50 the cathode and anode is equal to or less than the least dimension of the discharge vessel within. which the electrodes are enclosed, the light produced will be predominantly of a cathodic glow nature. For this reason lamps having a 55 construction such as that specified are commonly referred to as cathodic lampsand will be so referred to herein.
  • Electrons proceeding from the boundary of the sheath toward the anode will produce such ionization of the'gaseous atmosphere as is required to maintain a plasma or condition of equilibrium in the discharge space.
  • ionization consists in the creation of positively charged particles and is a result of collisions between atoms and electrons and the absorption of energy by the former.
  • Such collisions as do not result in the production of positive ions may'produce excitation of the colliding atoms, the electron energy required for excitation being less than that required for ionization. It is this latter phenomenon (excitation) which is chiefly responsible for the production of light.
  • the rate of production of positive ions is determined jointly by the electronic current moving from the cathode and by the average velocity of the electrons which comprise that current.
  • the ratio Ie/Ip in which 10 represents the electronic .current and 19 represents positive ion current moving to the cathode, will remain a constant maximum as long as the electrons demanded by the discharge are not in excess of those supplied by the zero field emission of the cathode (i. e. the emission of which the cathode is capable without the presence of a positive field at the cathode 5 surface).
  • the magnitude of the discharge is such as to require a greater number of electrons than are supplied by the zero field emission oi the cathode, then a. compensatory change in condition must take place. This change is accomplished by an increase in electron emission from the cathode, which increase is produced by the action of an electric field as will be more fully explained in the following:
  • the electric field required to offset the inadequacy of the electron supply may be created either by an increased cathode drop or by the accumulation of positive ions in the vicinity of the cathode.
  • both these factors wil be involved in the equilibrium-seeking changes necessitated by an increase in discharge current with respect to the zero field electron emission of the cathode. This is true because an increased cathode drop, acting through an increase in electron velocity, raises the rate of production of ions per electron which in turn produces a greater electric field at the cathode.
  • the cathode drop will seek a value at which the rate of generation of positive ions is exactly that which will produce the field regiuired to stimulate therequired electron emis- It will be seen that ⁇ as a consequence of the increased rate or production of positive ions with reference to electron emission the ratio Ie/Ip between these two quantities will have decreased. As still greater fields are required for further increasing discharge currents this ratio must again be decreased by adisproportionate change in the value of Ip. Thus, it will be seen that whereas throughout the range of zero field emission, a linear relation exists between the electron and positive ion currents, in the region of required field emission, we have a non-linear relation between these same quantities.
  • a sealed envelope I suitably of glass, having at the lower end a reentrant stem 2 terminating in a press 3.
  • a transverse septum 4 for example of mica, serves substantially to isolate the stem-containing portion of the envelope'from the main discharge space.
  • an ionizable gas for example, neon
  • a pressure of from about one-half to several millimeters, for example, 1 millimeter and a quantity of vaporizable easily ionizable material indicated at 6 as adhering to the walls of the discharge vessel, which latter material may suitably comprise a mixture of sodium and mercury.
  • the conditions of operation should preferably be such that the concentrations of the various constituents are in inverse order to their ionization potentials.
  • the conditions may suitably be such that the pressure of sodium is about 0.1 micron, the pressure of-mercury about 0.1 millimeter and the pressure of neon about 2 millimeters.
  • An anode comprising a pair of similar sleevelike metal rings 8 and 9 is supported on a vertical rod secured at its lower end to the press 3.
  • This rod may consist of a. conducting element l0 embedded for the greater portion of its length in a refractory insulating material H, such as alumina, which serves to protect the conductor from the effects of the discharge.
  • the anode parts 8, 9, are electrically connected by conductor l0 and are consequently maintained at approximately the same potential.
  • a thermionic cathode l3 suitably comprising a refractory base member, for example, of tungsten, coated with an electron emisslve material, for
  • the cathode is so positioned that its distance from the anode surface is less than the least dimension ofthe envelope 1', thus fulfilling the requisite conditions for the maintenance of a cathodic type 01' discharge.
  • Heating current is supplied to the oathode through insulated lead-in connections I 4 and I; which also serve to support the cathode in place.
  • the lead-in connections I4 and I! which are sealed through the press 3, may be connected to a source of heating current.
  • this comprises atransformer havingasecondary I 6 and a primary fl-gthe latter beingprovided with a serially connected current-11ml ng device 18 shown as a variable resistor?
  • the anode and cathode terminals is im" a discharge potential derived as shown from the secondary of a transformer 20.
  • a. current-limiting device such as a variable reactor 22 is provided in series with the transformer primary.
  • the ratio I /I. will be a minimum (or Ie/Ip a maximum, as previously explained) and the positive ion current will be preponderantly produced by ionization of the sodium. This requires electrons or a velocity equal to or slightly in excess or 5.1 volts and will'res'ult in the production of light developed almost exclusively by the excitation of sodium atoms.
  • Fig. 2 I have shown graphically the nature of the results which may be obtained when using an alternating current discharge supply in connection with cathodic lamps, employing mixed gases.
  • sinusoidal curve A represents the cyclical variations of the discharge current
  • horizontal dotted lines indicate the currents at which, for
  • the cathode drop exceeds the above-mentioned excitation voltage of mercury.
  • T1 for example, the zero field emission of the cathode may be suflicient to take care of the demands of the discharge current in the time interval ab.
  • this condition no longer obtains and an increase in the cathode drop sets in so that in the interval be the light emission from the discharge may be partially, or even predominantly composed of mercury luminescence. Furtherrepeated very many times during each second,
  • the apparent effect on the observer will be that of the generation of a mixed or blended light comprising the spectra of all three of the gaseous constituents.
  • these constituents comprise sodium, mercury and neon, respectively, characterized by yellow, blue, and red luminescence
  • thecolor distribution may be such as to produce a polychromatic or approximately white light.
  • Fig. 3 the curves illustrated show how color regulation may be obtained in a slightly difierent manner by adjustment of the average value of the discharge current while leav ing the cathode temperature constant.
  • curve B which represents the greater value of the dis- .charge current
  • the cathode is assumed to be set at a temperature T3 at which zero field emission is less than that required to supply the current at the peak of the cycle. Consequently, color blending of the type previously described may occur. If, however, with the same cathode tem-.
  • the color of the emitted light may be made to change in a very pleasing manner.
  • the cathode temperature falls below that at which the zero field emission is less than the electronic current required by the discharge, the spectrum of the emitted luminescence will be more and more that of the gaseous constituent of highest excitation potential.
  • the cathode temperature again increases the spectrum of the constituents of lower excitation potential will again predominate. It will be clear that this mode of regulation may be accomplished either manually or automatically by the use of a rotating contactor device or other known means included in the cathode circuit, whereby the cathode current may be cyclically varied in a desired position.
  • a method of producing color variations in a cathodic lamp containing a plurality of ionizing media which comprises passing a discharge current of relatively constant average value through said lamp and cyclically varying the normal zero field emission of the cathode of the lamp in such a manner that such emission is less than the electron current required by the discharge during a substantial portion of the variation and is greater than said current during another substantial portion of such variation whereby sequential excitation of the various ionizable media is obtained.
  • a method of producing color variations in a cathodic lamp containing a plurality of ionizable media of difierent excitation and ionization potentials which comprises passing a discharge current of relatively constant average value through said lamp and cyclically varying the temperature of the cathode of the lamp in such a manner that the zero field emission of the cathode is less than the electron current required by the discharge during a substantial portion of such variation and is greater than such current during another substantial portion of the variation whereby sequential excitation of the various ionizable media is obtained.

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  • Discharge Lamp (AREA)
  • Discharge Lamps And Accessories Thereof (AREA)
US103567A 1936-10-01 1936-10-01 Method of producing polychromatic light Expired - Lifetime US2135283A (en)

Priority Applications (4)

Application Number Priority Date Filing Date Title
US103567A US2135283A (en) 1936-10-01 1936-10-01 Method of producing polychromatic light
FR827367D FR827367A (fr) 1936-10-01 1937-09-30 Perfectionnements aux lampes cathodiques
GB26526/37A GB503024A (en) 1936-10-01 1937-09-30 Improvements in and relating to electric discharge devices
FR827395D FR827395A (fr) 1936-10-01 1937-10-01 Perfectionnements aux sources de lumière

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US103567A US2135283A (en) 1936-10-01 1936-10-01 Method of producing polychromatic light

Publications (1)

Publication Number Publication Date
US2135283A true US2135283A (en) 1938-11-01

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Application Number Title Priority Date Filing Date
US103567A Expired - Lifetime US2135283A (en) 1936-10-01 1936-10-01 Method of producing polychromatic light

Country Status (3)

Country Link
US (1) US2135283A (fr)
FR (2) FR827367A (fr)
GB (1) GB503024A (fr)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4996465A (en) * 1988-06-27 1991-02-26 Matsushita Electric Works, Ltd. Variable color lighting device

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4996465A (en) * 1988-06-27 1991-02-26 Matsushita Electric Works, Ltd. Variable color lighting device

Also Published As

Publication number Publication date
FR827395A (fr) 1938-04-25
FR827367A (fr) 1938-04-25
GB503024A (en) 1939-03-30

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