US2166817A - Electric discharge device - Google Patents

Electric discharge device Download PDF

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Publication number
US2166817A
US2166817A US716112A US71611234A US2166817A US 2166817 A US2166817 A US 2166817A US 716112 A US716112 A US 716112A US 71611234 A US71611234 A US 71611234A US 2166817 A US2166817 A US 2166817A
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United States
Prior art keywords
grid
anode
voltage
tube
cathode
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Expired - Lifetime
Application number
US716112A
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English (en)
Inventor
Harold T Maser
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General Electric Co
Original Assignee
General Electric Co
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Publication date
Application filed by General Electric Co filed Critical General Electric Co
Priority to US716112A priority Critical patent/US2166817A/en
Priority to GB7946/35A priority patent/GB444362A/en
Priority to FR787452D priority patent/FR787452A/fr
Application granted granted Critical
Publication of US2166817A publication Critical patent/US2166817A/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
    • H01J17/00—Gas-filled discharge tubes with solid cathode
    • H01J17/50—Thermionic-cathode tubes
    • H01J17/52—Thermionic-cathode tubes with one cathode and one anode
    • H01J17/54—Thermionic-cathode tubes with one cathode and one anode having one or more control electrodes
    • H01J17/56—Thermionic-cathode tubes with one cathode and one anode having one or more control electrodes for preventing and then permitting ignition, but thereafter having no control

Definitions

  • the present invention relates to electrical discharge. apparatus, more particularly to thermionic devices containing an ionizable medium and provided with a source of electrons, a cooperating anode and an electrostatic control member or grid.
  • the invention is directed more particularly to a novel construction and arrangement of the grid electrode for use in this type of apparatus.
  • the invention is principally concerned with devices in which the pressure of the ionizable medium and the impressed voltages are such that a discharge of arc-like character, 1. e., having a flat straight line or slightly negative anode voltageanode current characteristic, is produced between the electrodes, the initiation of the discharge being controlled by the charge on the grid.
  • the grid ordinarily loses control unless fairly large and impractical bias voltages are employed but the arc may be conveniently stopped by removing the anode voltage.
  • the grid Upon re-applying this voltage, the grid again determines whether the arc will start and by the continued repetition of this process, the grid can control the average plate current over a period of time.
  • a practical method of obtaining interruption of the anode current or stoppage of. the arc discharge is to apply alternating current voltage to the anode, although direct current voltage may also be utilized in case proper circuit interrupting means are available.
  • Tubes or this character are usually designated negative grid arc discharge devices or simply negative tubes.
  • the amount of negative charge necessary to prevent ignition of the tube depends upon the anode voltage except in the case of the improved tubes which constitute the subject of the present invention. Generally speaking, the greater the anode voltage in the prior tubes, the more negative must be the grid voltage with respect to the cathode.
  • An object of the present invention is to provide a tube of the arc-like or glow discharge type which has a starting characteristic in which the negative grid voltage is substantially independent of anode voltage, at least much more independent than any prior tubes of this character.
  • the object is to provide a tube in which the starting negative grid voltage versus anode voltage characteristic is steep.
  • Tubes of this character are usually designated positive grid arc discharge devices, or simply positive tubes, meaning that it takes a charge on the grid which is positive with respect to the cathode to initiate a discharge, and any charges less positive, i. e., more negative than the predetermined charge will not ignite the tube.
  • another object of the invention is to provide a tube in which the electrode structure will not only provide the improved negative characteristic, as stated hereinbefore, but by a suitable and simple change in the structure, will also provide a positive characteristic of improved character.
  • the positive grid voltage-anode voltage characteristic obtained by the structure as thus modified and described hereinafter, is so steep that it closely approaches a vertical straight line, indicating that the positive grid voltage necessary to cause the arc to start is entirely independent of the anode voltage.
  • a more specific object is to provide an improved grid or control member which will give the improved negative and positive characteristics referred to above in tubes of the character described.
  • Fig. 1 represents an elevational view, partly broken away and in cross section, of a tube improved in accordance with the present invention
  • Fig. 2 is a plan View of one of the baflle members employed in the grid construction
  • Fig. 3 is a plan View of the modified transverse section
  • Fig. 4 is a graph depicting the negative and positive starting characteristics of the improved tube.
  • numeral I designates a glass envelope having a bulbous form and which terminates at the lower end in a metal socket member 2, carrying several contact pins 3.
  • the envelope at the top is drawn down to a portion 4 of reduced size which supports a relatively large metal thimble 5 secured thereto in any suitable and well-known manner.
  • the envelope contains a plurality of cooperating electrodes including the cathode 6, an electro static control member 1 and an anode 8.
  • the envelope may contain a globule of mercury which produces vapor at the operating temperature sufficient to carry the desired current.
  • the cathode 6 is preferably of the well known indirectly heated type, although it will be understood that if desired, a directly heated filamentary cathode may be employed, depending upon the type of tube, anode voltage, current requirements, etc.
  • the cathode is constituted of a metal casing (not shown) which contains a longitudinal helix (not shown) serving as a heater.
  • a number of equidistantly spaced longitudinal vanes which are secured at their radial extremity to a metal cylinder which serves to prevent radiation of heat.
  • the recesses between the vanes are open at the end nearer the anode and are preferably coated on the interior with electronically active material, such as barium oxide.
  • Several other heat shields spaced apart in any suitable manner may surround the cylinder referred to above, to further reduce heat radiation. The outermost of these heat shields is illustrated in the drawing and is designated by the reference character 6.
  • a pair of load current conductors 9, connected in parallel, may be taken from the cathode structure through the press IU of the envelope to the exterior and connected to one of the contact pins 3.
  • One end of the filamentary spiral is connected within the interior of the casing to the cathode, and the other end is brought out by a lead II to a conductor 20 which also passes through the press and is connected to one of the contact pins 3.
  • a cathode of this general type, including the vanes and heat shields, is disclosed and claimed in the Hull and Ruggles Patent No. 1,924,318, August 29, 1933, assigned to the same assignee as the present application.
  • the anode 8 may be fabricated of carbonized nickel or graphite and is mounted in place by means of a plurality of support wires 12 which terminate in a metal sleeve l3 secured to a glass pant leg I4. A leading-in conductor for the anode is taken through the pant leg and makes connection with the external contact member 5.
  • the control member or grid which constitutes the subject of the present invention is preferably made in the form of a long metal cylinder which may or may not be perforated.
  • the cylinder is spaced away from the envelope and extends at one end, well beyond the anode 8 and at the other end, well beyond the inner edge or the electronemitting mouth of the cathode.
  • the anode is completely surrounded by the grid cylinder, while the cathode has only a small portion of its lower surface projecting therefrom and that portion does not emit electrons.
  • the function of the control member or grid is to control the starting of the arc or glow during the recurring positive half-cycles of the alternating voltage on the anode, thereby determining the average current flowing through the tube over a period of time.
  • baflles Intermediate the ends of the metal cylinder, there are two metal cross-pieces, baflles, or layers 2
  • the baflles may be spun to shape with a downwardly extending flange which fits snugly within the grid cylinder and is secured thereto.
  • Each baille may have a large number of relatively small openings as illustrated ni Figs. 1 and 2, or one circular central opening 23, as shown in Fig. 3 which is preferably of larger size than the openings provided in the multi-opening bafile.
  • transverse members within the grid cylinder 1 are made of metal, it is understood that, if desired, these members, also the cylindrical portion of the grid, may be fabricated of semiconducting material such as graphite.
  • control member as a whole, is supported in position by several equidistantly spaced rod uprights l5, which are secured at one end to the outer surface of the grid, and at the other end, terminate in a metal collar l6 which may be clamped tightly by means of screws H to the stem l8 of the envelope.
  • a leading-in conductor l9 may be taken from a convenient part of the collar l6 and passed through the envelope to make contact with one of the terminal pins 3.
  • a tube of the type described in which a grid is employed having two perforated cross-pieces or baffle members offers many advantages over tubes which are provided with other types of control members, including variously shaped grids and those in which only one bafile is employed.
  • the long cylindrical member 1 which extends well beyond the active surfaces of both the cathode and anode shields the current path between the electrodes from the electric charges which inevitably collect on the interior surface of the envelope.
  • the provision of the two cross-piece or baffle members offers the distinct advantage over the open cylindrical grid, i.
  • a positive grid characteristic of the most desirable sort may be imparted to the device, by which is meant that the discharge will be restrained so long as the grid is not positive or, at least, is no more negative than the cathode.
  • a positive grid characteristic of the most desirable sort is highly desirable in certain forms of translating circuits.
  • the double-bafile grid structure improved in accordance with the present invention, upon proper change in the spacing between baffles, thickness of baffle and size of opening therein may impart a negative characteristic to the tube, also of the most desirable sort.
  • the bailies are made thinner and the distance between baffles decreased.
  • the openings in the bafiles are also made larger.
  • the cross-pieces exert a stronger control effect, 1. e., greater re straining effect on the discharge, than the cylindrical portion.
  • the chief function of the cylinder, apart from the cross-pieces, is to protect the discharge path from migratory charges on the envelope, i. e., to provide simply a shielding or screening effect.
  • Fig. 4 The effect of modifying the cross-piece struc ture to obtain dverent characteristics is clearly shown in Fig. 4 wherein curves a and b depict the negative and positive characteristics respectively, obtainable in a typical tube improved in accordance with the present invention.
  • the curves are plotted against anode voltage as ordinate, and grid voltage at the time of starting as abscissa. These curves demonstrate that in the improved tube, the grid voltage on the negative side of the ordinate is almost independent of the anode voltage while on the positive side, it is absolutely independent thereof,
  • the double cross-piece type of grid not only offers many advantages over the open cylinder type of grid, as stated hereinbefore, but also advantages over a grid which is provided with only a single cross-piece or bafile.
  • the method commonly employed is to make the hole or holes in the crosspiece smaller.
  • the arc stream becomes more concentrated, and gives rise to electrical transients due to partial stoppage of the current if the hole is extremely small.
  • the starting grid voltage is substantially independent of the anode voltage over a large portion of the operating range While in the case of a positive tube, the grid voltage is entirely inde pendent of the anode voltage.
  • the grid starting voltage versus anode voltage characteristic both on the negative and positive side of the ordinate are more or less flat, or at least much more curved than those of. the double-baffle grid tube, so that the grid voltage is not independent of the anode voltage.
  • a positive tube with a double layer grid will also operate at a much lower condensed mercury temperature than a single tube and such a tube is 5 may be designed to give a definite positive characteristic, obviously, if the grid were accidentally disconnected from its energizing circuit, so that it assumes a floating potential, nearly that of the cathode, the arc will be extinguished at the end of the positive alternating voltage cycle of the anode.
  • This consideration is of extreme importance when emplcyingtubes of this character as signal relays. Since the improved tube will fail to ignite on the succeeding positive halfcycle of the anode voltage when the grid becomes disconnected, a false signal is precluded from being given by the relay.
  • the single opening form of bave offers certain advantages
  • the point where the starting characteristic curve of grid voltage versus anode voltage crosses the axis of zero grid voltage of a tube employing a single opening is much lower than when a large number of holes are used. This means that with zero voltage on the grid, only a small anode voltage is required to start discharge and such a characteristic is sometimes desirable.
  • An electron discharge device including an envelope containing a thermionic cathode, an anode, and an electrostatic control element, an ionizable medium in said envelope at a pressure under operating conditions sufficient to support an arc-like discharge at the impressed voltages, said control element comprising a hollow member surrounding the discharge path between the cathode and anode and provided with only two perforated sheets positioned in the discharge path, the perforations in said sheets being of circular configuration and in effective alignment.
  • An electron discharge device including an envelope containing a thermionic cathode, an anode, and an electrostatic control element, an ionizable medium in said envelope at a pressure under operating conditions suificient to support an arc-like discharge at the impressed voltages, said control element comprising a hollow member surrounding the discharge path between the cathode and anode, and provided with only two sheets having circular openings in register with one another and mounted transversely across the interior of said element.
  • An electron discharge device including an envelope containing a thermionic cathode, an anode, and an electrostatic control element, an ionizable medium in said envelope at a pressure under operating conditions sufiicient to support an arc-like discharge at the impressed voltages, said control element comprising a cylindrical member spaced away from the envelope and provided with only two perforated sheets extending across the interior of said member, the perforations in said sheets being of circular configuration and in effective alignment.
  • An electron discharge device including an envelope containing a thermionic cathode, an anode, and an electrostatic control element, an ionizable medium in said envelope at a pressure under operating conditions suflicient to support an arc-like discharge at the impressed voltages, said control element comprising a cylindrical member spaced away from the envelope and extending substantially to the rear surface of the cathode and anode, said member provided with only two perforated sheets extending transversely across the interior thereof, the perforations in said sheets being of circular configuration and in effective alignment.
  • An electron discharge device including an envelope containing a thermionic cathode, an anode, and an electrostatic control element, an ionizable medium in said envelope at a pressure under operating conditions sufficient to support an arc-like discharge at the impressed voltages, said control element comprising a cylindrical member spaced away from the envelope and surrounding the cathode and anode, said member being provided with only two perforated sheets extending transversely across the interior thereof, each of said sheets being provided with a peripheral flange which fits snugly within the cylindrical member and is secured thereto, the perforations in said sheets being of circular configuration and in effective alignment.
  • An electron discharge device including an envelope enclosing a thermionic cathode and an anode, and containing an ionizable medium for supporting a self-sustaining discharge between said cathode and said anode, and a control electrode comprising a pair of parallel metal sheets, each having a plurality of circular perforations of uniform diameter and mounted with the perforations in effective alignment, said sheets being spaced apart a distance at least as great as the diameter of the perforations in said sheets.
  • An electron discharge device including an envelope enclosing a thermionic cathode and an anode, and containing an ionizable medium for supporting a self-sustaining discharge between said cathode and anode, and a control electrode including a tubular member having a pair of perforated discs mounted in said member perpendicular to its longitudinal axis, said perforations being in alignment and spaced apart a distance at least equal to the average diameter of the perforations in said discs.
  • An electron discharge device including an envelope enclosing a thermionic cathode and an anode and containing an ionizable medium for supporting a self-sustaining discharge between said cathode and said anode and a control electrode between the anode and the thermionic cathode and comprising a tubular member provided with a pair of metal members having parallel surfaces, each of said members having a plurality of perforations of uniform size and mounted with the perforations in efiective alignment, said members being spaced apart a distance at least equal to the average diameter of the perforations in said members.
  • a discharge device including an envelope enclosing a thermionic cathode and an anode and containing an ionizable medium for facilitating the maintenance of a low voltage discharge between said cathode and anode, and a control electrode comprising a pair of parallel metal sheets, each having a plurality of generally similar perforations of substantially the same area and mounted with the perforations in effective alignment, said sheets being spaced apart a distance at least as great as the average diameter of the perforations in said sheets.

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US716112A 1934-03-17 1934-03-17 Electric discharge device Expired - Lifetime US2166817A (en)

Priority Applications (3)

Application Number Priority Date Filing Date Title
US716112A US2166817A (en) 1934-03-17 1934-03-17 Electric discharge device
GB7946/35A GB444362A (en) 1934-03-17 1935-03-14 Improvements in and relating to electric discharge devices
FR787452D FR787452A (fr) 1934-03-17 1935-03-16 Tube à décharge

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US716112A US2166817A (en) 1934-03-17 1934-03-17 Electric discharge device

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US2166817A true US2166817A (en) 1939-07-18

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FR (1) FR787452A (fr)
GB (1) GB444362A (fr)

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2518879A (en) * 1945-02-03 1950-08-15 Kenneth J Germeshausen Hydrogen thyratron
US2678403A (en) * 1946-05-03 1954-05-11 Us Navy Grid probe structure

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2518879A (en) * 1945-02-03 1950-08-15 Kenneth J Germeshausen Hydrogen thyratron
US2678403A (en) * 1946-05-03 1954-05-11 Us Navy Grid probe structure

Also Published As

Publication number Publication date
GB444362A (en) 1936-03-19
FR787452A (fr) 1935-09-23

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