US2935638A - Cathode structures for thermionic valves - Google Patents

Cathode structures for thermionic valves Download PDF

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Publication number
US2935638A
US2935638A US817575A US81757559A US2935638A US 2935638 A US2935638 A US 2935638A US 817575 A US817575 A US 817575A US 81757559 A US81757559 A US 81757559A US 2935638 A US2935638 A US 2935638A
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US
United States
Prior art keywords
cathode
heater
heating element
sleeve
helical
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
US817575A
Other languages
English (en)
Inventor
Farrow Frederic Willia Rodbard
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.)
Siemens Edison Swan Ltd
Original Assignee
Siemens Edison Swan Ltd
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 Siemens Edison Swan Ltd filed Critical Siemens Edison Swan Ltd
Application granted granted Critical
Publication of US2935638A publication Critical patent/US2935638A/en
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
    • 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
    • H01J1/22—Heaters

Definitions

  • This invention relates to indirectly heated cathode structures and is especially applicable to such structures of the kind in which an electrically insulated heating element is accommodated within a metal sleeve coated with electron-emissive material.
  • the heating element which takes the form of a length of electrically insulated refractory wire of spiralised hairpin or M-shaped configuration is supported within the sleeve by means of a metal-cored helical insulator which fits into the metal sleeve and embraces the heating element.
  • the present invention has in view a form of cathode heater which enables the separate helical insulator, just above referred to, to be dispensed with.
  • the helical protuberance is preferably narrow and of hollow form.
  • Fig. 1 shows a cathode heater according to the invention
  • Fig. 2 shows a fragmentary longitudinal cross-sectional view of the heater according to Fig. 1.
  • a helical heating element 1 of small pitch (e.g. having 100-500 turns per inch) is formed by winding tungsten wire for example on to a suitable mandrel (not shown) such as of molybdenum, or other material capable of being dissolved in acid without the latter attacking the wire of the heating element.
  • Molybdenum or other wire likewise capable of being dissolved in acid is wound over the element 1 so as to form thereon an outer helix having a relatviely large pitch (e.g. having turns per inch).
  • the mandrel and the two helices carried thereby are then passed through a furnace to set the helices, after which they are cut into the desired lengths.
  • Each length is then bent into the form of a hairpin as shown in Fig. l or otherwise bent according to the desired shape of the heater and thereafter thinly coated with a refractory electrically insulating material defining sleeve 2 such as by spraying, dipping or electrophoresis.
  • the heating element and the outer helix may be coated with refractory insulating material by suspending them in a bath containing a suspension having the following compositions Alumina gms 1980 Silica g 20 Aluminium nitrate gms 48 Magnesium nitrate "gals-.. 45
  • the insulating coating of the heater may be strengthened to render the heater more robust by coating the heater with a bonding agent such as a solution of polymethacrylic ester or nitro-cellulose.
  • the mandrel and the wire forming the outer helix may have a diameter of .008 while the diameter of the heating wire and the thickness of the insulating coating may be .003".
  • the invention provides a cathode heater which is formed with integral helical spacing means, thereby obviating the need for a separate helical insulator between the cathode sleeve and the heating element.
  • the helical protuberance will, in cases where the heater is a close fit in the cathode sleeve prevent movement of the heater with respect to the sleeve and thereby prevent hum due to variations in the heater to cathode capacitance in valves subject to vibration.
  • a cathode heater comprising a helical heating element of small pitch coated externally with a layer of refractory electrically insulating material defining an insulating sleeve with an external helical protuberance of relatively large pitch.
  • a method of manufacturing a cathode heater including the steps of winding a helical heating element of small pitch on a mandrel, winding a helix of relatively large pitch on said element, coating the assembly with a layer of refractory insulating material and dissolving the mandrel and the outer helix with acid incapable of attacking the heating element and insulating material.
  • An indirectly heated cathode structure comprising 5 No references cited.

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  • Solid Thermionic Cathode (AREA)
US817575A 1958-06-10 1959-06-02 Cathode structures for thermionic valves Expired - Lifetime US2935638A (en)

Applications Claiming Priority (1)

Application Number Priority Date Filing Date Title
GB18535/58A GB848589A (en) 1958-06-10 1958-06-10 Improvements relating to cathode heaters

Publications (1)

Publication Number Publication Date
US2935638A true US2935638A (en) 1960-05-03

Family

ID=10114082

Family Applications (1)

Application Number Title Priority Date Filing Date
US817575A Expired - Lifetime US2935638A (en) 1958-06-10 1959-06-02 Cathode structures for thermionic valves

Country Status (5)

Country Link
US (1) US2935638A (is)
DE (1) DE1124158B (is)
FR (1) FR1226931A (is)
GB (1) GB848589A (is)
NL (1) NL105737C (is)

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4002884A (en) * 1974-01-30 1977-01-11 International Standard Electric Corporation Heater element for an indirectly heated cathode

Family Cites Families (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
DE868319C (de) * 1944-01-26 1953-02-23 Wiener Radiowerke Ag Heizelement fuer indirekt erhitzte Kathoden von Entladungsroehren

Non-Patent Citations (1)

* Cited by examiner, † Cited by third party
Title
None *

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4002884A (en) * 1974-01-30 1977-01-11 International Standard Electric Corporation Heater element for an indirectly heated cathode

Also Published As

Publication number Publication date
GB848589A (en) 1960-09-21
FR1226931A (fr) 1960-08-18
DE1124158B (de) 1962-02-22
NL105737C (is)

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