US2247869A - Heater element for cathodes used in radio tubes and method of making the same - Google Patents

Heater element for cathodes used in radio tubes and method of making the same Download PDF

Info

Publication number
US2247869A
US2247869A US321308A US32130840A US2247869A US 2247869 A US2247869 A US 2247869A US 321308 A US321308 A US 321308A US 32130840 A US32130840 A US 32130840A US 2247869 A US2247869 A US 2247869A
Authority
US
United States
Prior art keywords
core
wire
heating
coil
flexible
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
US321308A
Inventor
John R Beers
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.)
Individual
Original Assignee
Individual
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 Individual filed Critical Individual
Priority to US321308A priority Critical patent/US2247869A/en
Application granted granted Critical
Publication of US2247869A publication Critical patent/US2247869A/en
Anticipated expiration legal-status Critical
Expired - Lifetime legal-status Critical Current

Links

Images

Classifications

    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/13—Solid thermionic cathodes
    • H01J1/20—Cathodes heated indirectly by an electric current; Cathodes heated by electron or ion bombardment
    • 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
    • H05B3/00—Ohmic-resistance heating
    • H05B3/10—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor
    • H05B3/16—Heater elements characterised by the composition or nature of the materials or by the arrangement of the conductor the conductor being mounted on an insulating base
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T29/00—Metal working
    • Y10T29/49—Method of mechanical manufacture
    • Y10T29/49002—Electrical device making
    • Y10T29/49082—Resistor making
    • Y10T29/49087—Resistor making with envelope or housing
    • Y10T29/49096—Resistor making with envelope or housing with winding
    • Y—GENERAL TAGGING OF NEW TECHNOLOGICAL DEVELOPMENTS; GENERAL TAGGING OF CROSS-SECTIONAL TECHNOLOGIES SPANNING OVER SEVERAL SECTIONS OF THE IPC; TECHNICAL SUBJECTS COVERED BY FORMER USPC CROSS-REFERENCE ART COLLECTIONS [XRACs] AND DIGESTS
    • Y10—TECHNICAL SUBJECTS COVERED BY FORMER USPC
    • Y10T—TECHNICAL SUBJECTS COVERED BY FORMER US CLASSIFICATION
    • Y10T428/00—Stock material or miscellaneous articles
    • Y10T428/29—Coated or structually defined flake, particle, cell, strand, strand portion, rod, filament, macroscopic fiber or mass thereof
    • Y10T428/2913—Rod, strand, filament or fiber
    • Y10T428/2933—Coated or with bond, impregnation or core
    • Y10T428/2936—Wound or wrapped core or coating [i.e., spiral or helical]

Definitions

  • This invention relates to heater elements and method of producing the same for cathodes used in the conventional type or" radio tubes.
  • the line heating wire has been wound upon a metal mandrel in a coil winding machine and after the coil has been wound the mandr l has been dissolved out with an acid.
  • a flexible metal mandrel one was enabled to use a conventional coil winding machine to produce the heating elements.
  • the problem which I have solved involves the feature of providing a heating coil with a ceramic core or mandrel which is of sufiicient flexibility to enable it to be used as a mandrel in a coil winding machine and on which the heating coil is wound.
  • a tungsten or molybdenum wire of any desired length and coat it throughout its length with a suitable high temperature ceramic type insulation to a predetermined diameter.
  • the insulating core thus produced is placed in a coil winding 1nachine in the same way as the metal mandrel referred to above and the heating coil is wound thereon throughout the length of the core.
  • the insulated core is of sufficient flexibility to enable it to be wound upon a spool and to be used in a coil winding machine without breaking the insulation.
  • the heating element is wound on the insulation core in alternate sections of closely wound turns and coarsely wound turns and after completion of the winding the coils are separated by cutting midway of the coarsely wound turns.
  • This provides short sections of heating filaments terminating at each end in a few coarse turns, which turns may be used as cor1- nesting leads for the heating element.
  • the core of ceramic insulation which, of course, retains III its flexibility is maintained in the completed heating coil during normal operation and is not dissolved out or dispensed with as in the case of a metal core.
  • an object of the invention is to provide a heating coil mounted upon a flexible core of ceramic insulation and the invention also resides in the method of producing, continuously, heating elements for radio tubes in a conventional coil winding machine, which I am enabled to do by reason of my development of the core of ceramic insulation which is of suflicient flexibility to enable it to be used in such machines.
  • Fig. 2 is a section on line 22 of Fig. 1;
  • Fig. 3 is similar to Fig. 1 with the core separated and the coarse turns straightened;
  • Fig. 4 shows a construction using two insulated cores as a mandrel
  • Fig. 5 is a section on line 55 of Fig. i.
  • the core wire I has thereon a flexible coating of ceramic insulation 2.
  • the resistance or heating wire 3 has been coiled.
  • the heating wire is coiled in closely wound turns as indicated at A and coarsely wound turns as indicated at B.
  • the closely wound sections A form the heating elements while the sections B are cut in the middle and serve to form connecting leads for the sections A.
  • the method of construction employed is as follows: a length of tungsten or molybdenum wire is coated with a high temperature resistant ceramic insulation to a predetermined diameter.
  • the coated wire is sufliciently flexible to admit of being wound on a spool and used as a mandrel in a conventional coil winding machine.
  • the flexible coated core or mandrel is then placed in a coil winding machine and the heating wire wound thereon in alternating sections of coarse and line turns, B and A as a continuous operation.
  • Figure 3 shows two heater sections or units in which the core had been cut and the coarse turns of a section B straightened but not cut.
  • the length of insulated core employed in windings is from to 300 feet and this will accommodate from 1,000 to 2,000 complete heating coils wound from a single piece of tungsten wire on a continuous coil winding machine.
  • tungsten wire having a diameter of the order of .007 inch has been employed and this wire is coated with ceramic insulation to a diameter of the order of from .030 to .032 inch.
  • the diameter of the heating coil wire itself is of the same order as that of core wire.
  • Figures 4 and 5 illustrate a construction in which two coated conductors are employed as a mandrel and the heating wire coiled thereon.
  • the two cores of Fig. 4 are duplicates of the single flexible core of Fig. 1, each comprising a center tungsten or molybdenum wire I, a coating 2 of ceramic insulation which is flexible enough to be wound on a spool and used in a coil winding machine as a flexible mandrel.
  • the heater wire 3 in Figs. 4 and 5 is wound in alternate sections of fine and coarse turns A and B and these sections are separated into individual units as above described in connection with the description of Figs. 1, 2 and 3.
  • One, two, or three insulated core mandrels could be used for a single coil. It has been found most satisfactory, however, to employ a single core for the present type of tube in which the high voltages are used.
  • the heating unit may be finished by connecting one end of the heating coil to the adjacent end of a core wire leaving the other free ends of the coil and core wire for leads.
  • the core wire may be disregarded as a connecting means and light metal caps slipped over the ends of the core or cores and the ends of the coils attached thereto.
  • a spray insulation is applied over the heater coil to indulate it from the metallic cathode sleeve.
  • alternate rings of insulation separated by short gaps of unsprayed coil facilitate the removal of gas, make the spray thickness less critical, and improve the action of the heater.
  • the usual method of producing ceramics is to mold or extrude suitable materials into the desired form and then subject them to a temperature at which the separate particles flow into each other and form an homogeneous mass.
  • a flexible ceramic in the form of an insulated wire the wire is drawn through suspensions of the ceramic material in water then through baking ovens arranged alternately.
  • the ceramic material usually consists of finely divided aluminum oxide. Binding of the oxide to the wire is accomplished by using a small amount of aluminum nitrate in the water suspension, the nitrate converting to oxide as it passes through the baking ovens.
  • the baking temperatures used are much below the fusion temperature of the aluminum oxide and so the particles retain their original form and are more or less only mechanically united by the converted nitrate.
  • a heating unit for radio tubes consisting of a flexible core wire, a flexible coating of ceramic material on said wire and a heating coil having its turns closely wound on said coating.
  • a method of continuously producing heating elements for radio tubes comprising, coating a length of flexible wire with a ceramic to produce a flexible mandrel, winding a heating coil on said mandrel in a coil winding machine and dividing the product into relatively short sections as individual heating units.
  • a manufactured product from which heating elements for radio tubes may be made, comprising a length of flexible core wire having a flexible coating of ceramic material thereon throughout its length and a plurality of coil sections coiled on said coating in continuous alternating sections of closely wound turns and coarsely wound turns.
  • a heating element for radio tubes comprising a core conductor having a diameter of the order of .00? inch, a flexible coating of ceramic insulation on said core having a diameter of the order of .032 inch and a coiled heater wire on said coating, the diameter of the wire of said coil being of substantially the same order as the core conductor.
  • a heating element for cathodes used in radio tubes comprising a flexible core wire of tungsten
  • a method of continuously producing heating coils for radio tubes which comprises coating 21 flexible wire of small diameter and substantial length with a flexible ceramic to form an insulating core, using said core as a flexible mandrel and winding a heating wire thereon in alternate sections of relatively closely wound and relatively coarsely wound turns and dividing the product between the successive closely wound sections.

Description

July I, 1941. J. R. BEERS 2.247.869
HEATER ELEMENT FOR OATH USED I ODES AND METHOD MAKING THE 5 Filed 28, 1940 N RADIO TUBES AME Patented July 1, 1941 UNETED STATES .PATEZNT OFFICE HEATER ELEMENT FOR CATHODES USED IN RADIO TUBES AND METHOD OF MAKING THE SAME 6 Claims.
This invention relates to heater elements and method of producing the same for cathodes used in the conventional type or" radio tubes.
There has been a tendency recently to have tubes in which the cathode heaters operate at fl'L 1 28 to 117 volts as compared to the older types op 'ating at 2.5 to 6 Volts. Using the higher voltage presents a problem since sometimes as much as six feet of very fine tungsten wire are required for each heating element.
According to prior practice the line heating wire has been wound upon a metal mandrel in a coil winding machine and after the coil has been wound the mandr l has been dissolved out with an acid. By using a flexible metal mandrel one was enabled to use a conventional coil winding machine to produce the heating elements.
It is also old in the art to provide heating coils of the type under consideration with a rigid core of insulating material and in some cases the insulation surrounds a wire core which may itself be used as a return lead for the heating coil. In the case where the coil has been wound upon a metal mandrel and the mandrel has been dissolved out, an insulating sleeve or core has been inserted in the coil to form a support therefor.
The problem which I have solved involves the feature of providing a heating coil with a ceramic core or mandrel which is of sufiicient flexibility to enable it to be used as a mandrel in a coil winding machine and on which the heating coil is wound.
In carrying out this process I employ a tungsten or molybdenum wire of any desired length and coat it throughout its length with a suitable high temperature ceramic type insulation to a predetermined diameter. The insulating core thus produced is placed in a coil winding 1nachine in the same way as the metal mandrel referred to above and the heating coil is wound thereon throughout the length of the core. The insulated core is of sufficient flexibility to enable it to be wound upon a spool and to be used in a coil winding machine without breaking the insulation. The heating element is wound on the insulation core in alternate sections of closely wound turns and coarsely wound turns and after completion of the winding the coils are separated by cutting midway of the coarsely wound turns. This provides short sections of heating filaments terminating at each end in a few coarse turns, which turns may be used as cor1- nesting leads for the heating element. The core of ceramic insulation which, of course, retains III its flexibility is maintained in the completed heating coil during normal operation and is not dissolved out or dispensed with as in the case of a metal core.
As indicated above an object of the invention is to provide a heating coil mounted upon a flexible core of ceramic insulation and the invention also resides in the method of producing, continuously, heating elements for radio tubes in a conventional coil winding machine, which I am enabled to do by reason of my development of the core of ceramic insulation which is of suflicient flexibility to enable it to be used in such machines.
The invention is illustrated in the accompanying drawing, in which- Figure 1 shows a short section of the wound core as it comes from the winding machine;
Fig. 2 is a section on line 22 of Fig. 1;
Fig. 3 is similar to Fig. 1 with the core separated and the coarse turns straightened;
Fig. 4 shows a construction using two insulated cores as a mandrel; and
Fig. 5 is a section on line 55 of Fig. i.
In the drawing the core wire I has thereon a flexible coating of ceramic insulation 2. On this coating 2 the resistance or heating wire 3 has been coiled. The heating wire is coiled in closely wound turns as indicated at A and coarsely wound turns as indicated at B. The closely wound sections A form the heating elements while the sections B are cut in the middle and serve to form connecting leads for the sections A.
The method of construction employed is as follows: a length of tungsten or molybdenum wire is coated with a high temperature resistant ceramic insulation to a predetermined diameter. The coated wire is sufliciently flexible to admit of being wound on a spool and used as a mandrel in a conventional coil winding machine. The flexible coated core or mandrel is then placed in a coil winding machine and the heating wire wound thereon in alternating sections of coarse and line turns, B and A as a continuous operation. When the product comes from the winding machine it is out into short lengths for use by cutting through the center of the coarse turns E. Figure 3 shows two heater sections or units in which the core had been cut and the coarse turns of a section B straightened but not cut.
Usually, in carrying out my process, the length of insulated core employed in windings is from to 300 feet and this will accommodate from 1,000 to 2,000 complete heating coils wound from a single piece of tungsten wire on a continuous coil winding machine.
In my development of this method and product a tungsten wire having a diameter of the order of .007 inch has been employed and this wire is coated with ceramic insulation to a diameter of the order of from .030 to .032 inch. The diameter of the heating coil wire itself is of the same order as that of core wire.
Figures 4 and 5 illustrate a construction in which two coated conductors are employed as a mandrel and the heating wire coiled thereon. The two cores of Fig. 4 are duplicates of the single flexible core of Fig. 1, each comprising a center tungsten or molybdenum wire I, a coating 2 of ceramic insulation which is flexible enough to be wound on a spool and used in a coil winding machine as a flexible mandrel. The heater wire 3 in Figs. 4 and 5 is wound in alternate sections of fine and coarse turns A and B and these sections are separated into individual units as above described in connection with the description of Figs. 1, 2 and 3.
One, two, or three insulated core mandrels could be used for a single coil. It has been found most satisfactory, however, to employ a single core for the present type of tube in which the high voltages are used.
The heating unit may be finished by connecting one end of the heating coil to the adjacent end of a core wire leaving the other free ends of the coil and core wire for leads. As an alternative method the core wire may be disregarded as a connecting means and light metal caps slipped over the ends of the core or cores and the ends of the coils attached thereto.
In further finishing the coil a spray insulation is applied over the heater coil to indulate it from the metallic cathode sleeve. In this connection, it has been found that, instead of the usual solid spray coating, alternate rings of insulation separated by short gaps of unsprayed coil facilitate the removal of gas, make the spray thickness less critical, and improve the action of the heater.
The usual method of producing ceramics is to mold or extrude suitable materials into the desired form and then subject them to a temperature at which the separate particles flow into each other and form an homogeneous mass. In producting a flexible ceramic in the form of an insulated wire the wire is drawn through suspensions of the ceramic material in water then through baking ovens arranged alternately. The ceramic material usually consists of finely divided aluminum oxide. Binding of the oxide to the wire is accomplished by using a small amount of aluminum nitrate in the water suspension, the nitrate converting to oxide as it passes through the baking ovens. The baking temperatures used are much below the fusion temperature of the aluminum oxide and so the particles retain their original form and are more or less only mechanically united by the converted nitrate.
By the described method of manufacture flexible heating units having a supporting core are produced. By this method the step of dissolving out a metal mandrel is avoided and the completed filaments more readily produced by a continuous process than heretofore known. Coils of any desired length can be easily produced and are flexible enough for manipulation and still have an insulation core which is often desirable.
What is claimed is- 1. A heating unit for radio tubes consisting of a flexible core wire, a flexible coating of ceramic material on said wire and a heating coil having its turns closely wound on said coating.
2. A method of continuously producing heating elements for radio tubes comprising, coating a length of flexible wire with a ceramic to produce a flexible mandrel, winding a heating coil on said mandrel in a coil winding machine and dividing the product into relatively short sections as individual heating units.
3. A manufactured product from which heating elements for radio tubes may be made, comprising a length of flexible core wire having a flexible coating of ceramic material thereon throughout its length and a plurality of coil sections coiled on said coating in continuous alternating sections of closely wound turns and coarsely wound turns.
4. A heating element for radio tubes comprising a core conductor having a diameter of the order of .00? inch, a flexible coating of ceramic insulation on said core having a diameter of the order of .032 inch and a coiled heater wire on said coating, the diameter of the wire of said coil being of substantially the same order as the core conductor.
5. A heating element for cathodes used in radio tubes comprising a flexible core wire of tungsten,
a flexible covering of ceramic material on said wire, and a heating coil of tungsten helically wound on said covering.
6. A method of continuously producing heating coils for radio tubes which comprises coating 21 flexible wire of small diameter and substantial length with a flexible ceramic to form an insulating core, using said core as a flexible mandrel and winding a heating wire thereon in alternate sections of relatively closely wound and relatively coarsely wound turns and dividing the product between the successive closely wound sections.
JOHN R. BEERS.
US321308A 1940-02-28 1940-02-28 Heater element for cathodes used in radio tubes and method of making the same Expired - Lifetime US2247869A (en)

Priority Applications (1)

Application Number Priority Date Filing Date Title
US321308A US2247869A (en) 1940-02-28 1940-02-28 Heater element for cathodes used in radio tubes and method of making the same

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
US321308A US2247869A (en) 1940-02-28 1940-02-28 Heater element for cathodes used in radio tubes and method of making the same

Publications (1)

Publication Number Publication Date
US2247869A true US2247869A (en) 1941-07-01

Family

ID=23250067

Family Applications (1)

Application Number Title Priority Date Filing Date
US321308A Expired - Lifetime US2247869A (en) 1940-02-28 1940-02-28 Heater element for cathodes used in radio tubes and method of making the same

Country Status (1)

Country Link
US (1) US2247869A (en)

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2422827A (en) * 1944-03-11 1947-06-24 Eitel Mccullough Inc Method of making grids
US2479192A (en) * 1946-06-28 1949-08-16 Gen Electric Cathode
US2589522A (en) * 1952-03-18 Cathode heater structure
US2589521A (en) * 1952-03-18 Heater
US2793277A (en) * 1956-03-30 1957-05-21 Sylvania Electric Prod Textile processing apparatus
US2831140A (en) * 1953-10-12 1958-04-15 Sylvania Electric Prod Cataphoretically coated heater insulator assembly
US2909753A (en) * 1955-08-30 1959-10-20 Beckman Instruments Inc Resistance elements and method of making same
US2932759A (en) * 1954-07-21 1960-04-12 Univ Minnesota Vacuum tube
US2953842A (en) * 1954-06-28 1960-09-27 Sylvania Electric Prod Method of making tabbed heater
US3002075A (en) * 1958-08-04 1961-09-26 Knapp Monarch Co Heating element for toaster
US3196523A (en) * 1958-06-30 1965-07-27 Zenith Radio Corp Method of constructing a tuning strip
US3280452A (en) * 1963-11-26 1966-10-25 Rca Corp Method of manufacturing heaters for electron discharge devices
US3286327A (en) * 1962-07-27 1966-11-22 Ward Leonard Electric Co Method of manufacturing electrical resistors
US3337949A (en) * 1963-12-30 1967-08-29 Sarkes Tarzian Method of making a coil assembly for a tuner
US3816706A (en) * 1972-12-23 1974-06-11 Eicherauer F Heating member for a hair dryer
US4626665A (en) * 1985-06-24 1986-12-02 Shell Oil Company Metal oversheathed electrical resistance heater
US5038458A (en) * 1989-02-22 1991-08-13 Heaters Engineering, Inc. Method of manufacture of a nonuniform heating element
US6737616B1 (en) 2003-04-02 2004-05-18 Tutco, Inc. Open coil electric resistance heater using twisted resistance wires and methods of making
US20100171411A1 (en) * 2007-06-13 2010-07-08 Aerojet-General Corporation Cathode heater
US8997753B2 (en) 2012-01-31 2015-04-07 Altria Client Services Inc. Electronic smoking article

Cited By (20)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US2589522A (en) * 1952-03-18 Cathode heater structure
US2589521A (en) * 1952-03-18 Heater
US2422827A (en) * 1944-03-11 1947-06-24 Eitel Mccullough Inc Method of making grids
US2479192A (en) * 1946-06-28 1949-08-16 Gen Electric Cathode
US2831140A (en) * 1953-10-12 1958-04-15 Sylvania Electric Prod Cataphoretically coated heater insulator assembly
US2953842A (en) * 1954-06-28 1960-09-27 Sylvania Electric Prod Method of making tabbed heater
US2932759A (en) * 1954-07-21 1960-04-12 Univ Minnesota Vacuum tube
US2909753A (en) * 1955-08-30 1959-10-20 Beckman Instruments Inc Resistance elements and method of making same
US2793277A (en) * 1956-03-30 1957-05-21 Sylvania Electric Prod Textile processing apparatus
US3196523A (en) * 1958-06-30 1965-07-27 Zenith Radio Corp Method of constructing a tuning strip
US3002075A (en) * 1958-08-04 1961-09-26 Knapp Monarch Co Heating element for toaster
US3286327A (en) * 1962-07-27 1966-11-22 Ward Leonard Electric Co Method of manufacturing electrical resistors
US3280452A (en) * 1963-11-26 1966-10-25 Rca Corp Method of manufacturing heaters for electron discharge devices
US3337949A (en) * 1963-12-30 1967-08-29 Sarkes Tarzian Method of making a coil assembly for a tuner
US3816706A (en) * 1972-12-23 1974-06-11 Eicherauer F Heating member for a hair dryer
US4626665A (en) * 1985-06-24 1986-12-02 Shell Oil Company Metal oversheathed electrical resistance heater
US5038458A (en) * 1989-02-22 1991-08-13 Heaters Engineering, Inc. Method of manufacture of a nonuniform heating element
US6737616B1 (en) 2003-04-02 2004-05-18 Tutco, Inc. Open coil electric resistance heater using twisted resistance wires and methods of making
US20100171411A1 (en) * 2007-06-13 2010-07-08 Aerojet-General Corporation Cathode heater
US8997753B2 (en) 2012-01-31 2015-04-07 Altria Client Services Inc. Electronic smoking article

Similar Documents

Publication Publication Date Title
US2247869A (en) Heater element for cathodes used in radio tubes and method of making the same
US2306925A (en) Electrode and its fabrication
US3131469A (en) Process of producing a unitary multiple wire strand
US2287460A (en) Insulated heater and method of manufacture
JPH0795430B2 (en) Composite wire for high frequency coil winding and deflection unit using such composite wire
US1944870A (en) Apparatus for making an electrical coil
GB465119A (en) Improvements in the manufacture of coiled-coil filaments for incandescent electric lamps and the like
US2371205A (en) Coiled
US2126155A (en) Incandescent electric lamp
US2014787A (en) Thermionic cathode
US2394474A (en) Coiled filament or cathode and its manufacture
US1972162A (en) Heater element electron emitting cathode
US2589521A (en) Heater
US2880297A (en) Electric heating units
US2177743A (en) Production of coiled vitreous tubing
US2397533A (en) Method of making cathodes
US2038297A (en) Method of making inductive windings
US2041286A (en) Indirectly heated cathode
US2482826A (en) Filament structure for thermionic tubes
US1744911A (en) Resistance device
US716048A (en) Electric heater.
US3280452A (en) Method of manufacturing heaters for electron discharge devices
US2241761A (en) Electrical coil and a method of making the same
US2167765A (en) Filament and method of making
US2192753A (en) Electron discharge device