US2058690A - Thermionic cathode gas-filled discharge tube - Google Patents

Thermionic cathode gas-filled discharge tube Download PDF

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Publication number
US2058690A
US2058690A US746000A US74600034A US2058690A US 2058690 A US2058690 A US 2058690A US 746000 A US746000 A US 746000A US 74600034 A US74600034 A US 74600034A US 2058690 A US2058690 A US 2058690A
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United States
Prior art keywords
cathode
members
current
parallel
tube
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Expired - Lifetime
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US746000A
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English (en)
Inventor
Holst Gilles
Mulder Johannes Gijsbe Wilhelm
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.)
Koninklijke Philips NV
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Philips Gloeilampenfabrieken NV
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/02—Details
    • H01J17/04—Electrodes; Screens
    • H01J17/06—Cathodes

Definitions

  • the present invention relates to electrical discharge tubes of the type having thermionic cathodes and a gas-filling and more particularly to a cathode construction for such discharge tubes, which enables the tubesto handle large discharge currents.
  • gas-filling as used herein also includes fillings of vapor or of mixtures of vapor and gas.
  • the general purpose of using gas-fillings in discharge tubes of this type is to enable the tube to handle large currents without large losses, whereby, due toionizationof the gas-filling the building up of space charge is prevented and the current conductivity of the tube is increased by the participation'of the gas ions in the current conduction.
  • Such discharge tubes in which the discharge has usually the character of an arc, may be used, for instance, as rectifiers which are capable of rectifying'large currents with small voltage loss, thus with high efiiciency, or may be used for various other purposes, for example as relaytubes, was discharge lamps.
  • a cathode which is to provide anemission current of about 1,000amperes, requires a very large emitting surface. If such a cathode is to be directly heated by the passage of a-heating'current supplied from an external source-which in general offers the simplest solution -ithas to be given the shape of a single filament of a very great length.
  • a cathode construction according tothe invention obviatesthe above difiiculties, and consists broadly of a composite cathode which consists of a plurality of parallel connected individual cathode members.
  • the present invention is based onthe realization, that it ispossible to so design a cathode member that an accidental increase in its current-emission does not cause any, or'at least no important, increase inzlits temperature, and that it is possible to avoid'a local concentration of the discharge arc. This will be more fully explained hereinafter.
  • a compensation of the above-mentioned positive and negative members can be effected by selecting dR small, 1. e., by giving the cathode element a small resistance.
  • dimming This phenomenon of the cathode portions cooling off at excessive current values, will be referred to as dimming.
  • the parallel-connected cathode elements are made short and thick. These dimensions can be conveniently designated by the value of the heating voltage applied to the elements. In practice we prefer to so form the parallel-connected cathode elements that the heating voltage across same does not exceed 1 volt.
  • this is obtained by forming the composite cathode of two parallel discs or rings between which individual, parallel-connected cathode elements are provided.
  • Each ring or disc is provided with a current lead which is so connected to same that the voltage drop through the disc or ring, measured from the connection points of the current leads to any one of the connection points of the cathode elements, has substantially the same value. This can also be promoted by giving the discs and rings ample thickness.
  • Figure 1 is a schematic view of a cathode structure according to the invention.
  • Fig. 2 is a discharge tube comprising a cathode structure in accordance with the invention.
  • Fig. 3 is an enlarged perspective View of the cathode structure of the tube shown in Fig. 2.
  • FIG. 1 there are shown four coiled wire cathode members I, 2, 3, and 4, which are disposed parallel to each other, and which are also parallel-connected between leads 5 and 6, the leads being provided with preferably integral bent portions 5 and 6, which are secured, preferably by welding, to the respective ends of the filamentary cathode members.
  • the leads 5 and 6 approach the group of cathode members from opposite sides, 1. e., the lead 5 first connects with the member 4 and then successively with members 3, 2 and l,whereas the lead 6 first connects with cathode member l and then successively with cathode members 2, 3 and 4.
  • the combined voltage drop in the two leads 5 and 6 is the same for each cathode member and consequently the same heating voltage is applied across each of the cathode members.
  • the individual cathode members consist of a helical filament having only a few turns.
  • the leads 5 and 6, as well as the cathode filament members I to 4, consist, as a rule, of a refractory metal, for instance tungsten, which is preferably provided with a nickel coating. Furthermore, the filament members may be surrounded by a closely wound nickel wire, as described in U. S. patent to Dobben, et al. No. 1,718,123.
  • the cathode members are provided with an emissive coating, usually an oxide coating of high electron emissivity, for instance, with a barium oxide coating.
  • an emissive coating usually an oxide coating of high electron emissivity, for instance, with a barium oxide coating.
  • tungsten other suitable metals or alloys, for instance nickel or nickel alloys, may be used.
  • the discharge tube shown in Fig. 2 is a rectifier tube comprising a vitreous envelope 8.
  • the envelope 8 is provided at one end with a reentrant neck portion 20 in the bottom of which is sealed a metal ring II, preferably of chrome iron, the ring H carrying the anode 9.
  • the active portion of the anode 9 is formed of a hood-shaped graphite member, into the central hollow portion of which extends a metal tube In, which tube is secured at its other and open end within the aperture of ring ll, for instance by being welded thereto. Through the metal tube lo cooling fluid may pass to the anode.
  • the tube I0 is surrounded by a tube l2 of insulating material, for instance of steatite, to prevent the tube l8 from participating in the discharge.
  • the composite cathode structure 1 consists of a plurality of parallel-arranged and parallelconnected filamentary cathode members l3. In the construction shown, twelve of these members are arranged in equal spacing about a circle as indicated in Fig. 3 in dot and dash lines.
  • the cathode members 13 consist of comparatively short and heavy wire which is coiled into a helix of a few turns and are of the general type above described.
  • the cathode members I3 are connected at their upper end to a disc l4 and at their lower end to a ring l5, the disc I4 and ring l5 being of considerable thickness and extending parallel to each other and perpendicularly to the cathode members I3.
  • the disc I4 is provided with a heavy current lead 16, which passes centrally through the ring l5 and is connected at the center of the disc M.
  • the current leads I 6 and l 8 are supported from the other end of the tube, which forms a neck 2
  • mercury vapor may be conveniently used, whereby an excess of liquid mercury is also provided in the tube.
  • the temperature at the mercury should be such as to give approximately 10 millimeters of mercury vapor pressure.
  • each of the cathode members is dimensioned for a heating voltage of 0.8 volts and a heating current of about 10 amperes.
  • a heating voltage of 0.8 volts and a heating current of about 10 amperes With such cathode construction a very high degree of uniformity in the burning of the parallel-connected cathode members is obtained. This uniformity can be achieved in tubes for very large currents, for example, 800 amperes and more, built according to our invention.
  • Such cathodes preferably exhibit the above referred dimming phenomenon, i. e. when the emission current in a cathode member exceeds the permissible value a lowering of the temperature of this member takes place.
  • a cathode structure for a thermioniccathode, gas-filled discharge tube comprising a group of parallel-disposed and parallel-connected coiled wire cathode elements, a conductive member connected to one end of each of said cathode elements and a conductive member connected to the opposite ends of said cathode elements, and a current lead connected to each of said conductive members, said leads approaching said group from opposite sides thereof, the combined voltage drops in said conductive members between connecting points of said leads and the connecting points of said cathode elements being the same for each of said cathode members.
  • a composite cathode structure for thermionic-cathode, gas-filled discharge tubes comprising a disc member and a ring member disposed parallel to each other, a plurality of coiled wire cathode elements mounted in parallel to each other and equidistantly spaced along the periphery of said members, said elements being connected in parallel between said members, a current lead centrally connected to said disc, and a current lead for said ring having two branches, said. branches being connected to diametrically opposite points of said ring.

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  • Discharge Lamp (AREA)
  • Solid Thermionic Cathode (AREA)
US746000A 1933-10-27 1934-09-28 Thermionic cathode gas-filled discharge tube Expired - Lifetime US2058690A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
DE427609X 1933-10-27

Publications (1)

Publication Number Publication Date
US2058690A true US2058690A (en) 1936-10-27

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Family Applications (1)

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US746000A Expired - Lifetime US2058690A (en) 1933-10-27 1934-09-28 Thermionic cathode gas-filled discharge tube

Country Status (5)

Country Link
US (1) US2058690A (en, 2012)
BE (1) BE405876A (en, 2012)
FR (1) FR780201A (en, 2012)
GB (1) GB427609A (en, 2012)
NL (1) NL42085C (en, 2012)

Also Published As

Publication number Publication date
FR780201A (fr) 1935-04-20
GB427609A (en) 1935-04-26
BE405876A (en, 2012)
NL42085C (en, 2012)

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